xref: /openbmc/qemu/block.c (revision 3cfafd31)
1 /*
2  * QEMU System Emulator block driver
3  *
4  * Copyright (c) 2003 Fabrice Bellard
5  * Copyright (c) 2020 Virtuozzo International GmbH.
6  *
7  * Permission is hereby granted, free of charge, to any person obtaining a copy
8  * of this software and associated documentation files (the "Software"), to deal
9  * in the Software without restriction, including without limitation the rights
10  * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
11  * copies of the Software, and to permit persons to whom the Software is
12  * furnished to do so, subject to the following conditions:
13  *
14  * The above copyright notice and this permission notice shall be included in
15  * all copies or substantial portions of the Software.
16  *
17  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
18  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
19  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
20  * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
21  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
22  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
23  * THE SOFTWARE.
24  */
25 
26 #include "qemu/osdep.h"
27 #include "block/trace.h"
28 #include "block/block_int.h"
29 #include "block/blockjob.h"
30 #include "block/fuse.h"
31 #include "block/nbd.h"
32 #include "block/qdict.h"
33 #include "qemu/error-report.h"
34 #include "block/module_block.h"
35 #include "qemu/main-loop.h"
36 #include "qemu/module.h"
37 #include "qapi/error.h"
38 #include "qapi/qmp/qdict.h"
39 #include "qapi/qmp/qjson.h"
40 #include "qapi/qmp/qnull.h"
41 #include "qapi/qmp/qstring.h"
42 #include "qapi/qobject-output-visitor.h"
43 #include "qapi/qapi-visit-block-core.h"
44 #include "sysemu/block-backend.h"
45 #include "qemu/notify.h"
46 #include "qemu/option.h"
47 #include "qemu/coroutine.h"
48 #include "block/qapi.h"
49 #include "qemu/timer.h"
50 #include "qemu/cutils.h"
51 #include "qemu/id.h"
52 #include "block/coroutines.h"
53 
54 #ifdef CONFIG_BSD
55 #include <sys/ioctl.h>
56 #include <sys/queue.h>
57 #if defined(HAVE_SYS_DISK_H)
58 #include <sys/disk.h>
59 #endif
60 #endif
61 
62 #ifdef _WIN32
63 #include <windows.h>
64 #endif
65 
66 #define NOT_DONE 0x7fffffff /* used while emulated sync operation in progress */
67 
68 static QTAILQ_HEAD(, BlockDriverState) graph_bdrv_states =
69     QTAILQ_HEAD_INITIALIZER(graph_bdrv_states);
70 
71 static QTAILQ_HEAD(, BlockDriverState) all_bdrv_states =
72     QTAILQ_HEAD_INITIALIZER(all_bdrv_states);
73 
74 static QLIST_HEAD(, BlockDriver) bdrv_drivers =
75     QLIST_HEAD_INITIALIZER(bdrv_drivers);
76 
77 static BlockDriverState *bdrv_open_inherit(const char *filename,
78                                            const char *reference,
79                                            QDict *options, int flags,
80                                            BlockDriverState *parent,
81                                            const BdrvChildClass *child_class,
82                                            BdrvChildRole child_role,
83                                            Error **errp);
84 
85 static void bdrv_replace_child_noperm(BdrvChild *child,
86                                       BlockDriverState *new_bs);
87 static void bdrv_remove_file_or_backing_child(BlockDriverState *bs,
88                                               BdrvChild *child,
89                                               Transaction *tran);
90 static void bdrv_remove_filter_or_cow_child(BlockDriverState *bs,
91                                             Transaction *tran);
92 
93 static int bdrv_reopen_prepare(BDRVReopenState *reopen_state,
94                                BlockReopenQueue *queue,
95                                Transaction *change_child_tran, Error **errp);
96 static void bdrv_reopen_commit(BDRVReopenState *reopen_state);
97 static void bdrv_reopen_abort(BDRVReopenState *reopen_state);
98 
99 /* If non-zero, use only whitelisted block drivers */
100 static int use_bdrv_whitelist;
101 
102 #ifdef _WIN32
103 static int is_windows_drive_prefix(const char *filename)
104 {
105     return (((filename[0] >= 'a' && filename[0] <= 'z') ||
106              (filename[0] >= 'A' && filename[0] <= 'Z')) &&
107             filename[1] == ':');
108 }
109 
110 int is_windows_drive(const char *filename)
111 {
112     if (is_windows_drive_prefix(filename) &&
113         filename[2] == '\0')
114         return 1;
115     if (strstart(filename, "\\\\.\\", NULL) ||
116         strstart(filename, "//./", NULL))
117         return 1;
118     return 0;
119 }
120 #endif
121 
122 size_t bdrv_opt_mem_align(BlockDriverState *bs)
123 {
124     if (!bs || !bs->drv) {
125         /* page size or 4k (hdd sector size) should be on the safe side */
126         return MAX(4096, qemu_real_host_page_size);
127     }
128 
129     return bs->bl.opt_mem_alignment;
130 }
131 
132 size_t bdrv_min_mem_align(BlockDriverState *bs)
133 {
134     if (!bs || !bs->drv) {
135         /* page size or 4k (hdd sector size) should be on the safe side */
136         return MAX(4096, qemu_real_host_page_size);
137     }
138 
139     return bs->bl.min_mem_alignment;
140 }
141 
142 /* check if the path starts with "<protocol>:" */
143 int path_has_protocol(const char *path)
144 {
145     const char *p;
146 
147 #ifdef _WIN32
148     if (is_windows_drive(path) ||
149         is_windows_drive_prefix(path)) {
150         return 0;
151     }
152     p = path + strcspn(path, ":/\\");
153 #else
154     p = path + strcspn(path, ":/");
155 #endif
156 
157     return *p == ':';
158 }
159 
160 int path_is_absolute(const char *path)
161 {
162 #ifdef _WIN32
163     /* specific case for names like: "\\.\d:" */
164     if (is_windows_drive(path) || is_windows_drive_prefix(path)) {
165         return 1;
166     }
167     return (*path == '/' || *path == '\\');
168 #else
169     return (*path == '/');
170 #endif
171 }
172 
173 /* if filename is absolute, just return its duplicate. Otherwise, build a
174    path to it by considering it is relative to base_path. URL are
175    supported. */
176 char *path_combine(const char *base_path, const char *filename)
177 {
178     const char *protocol_stripped = NULL;
179     const char *p, *p1;
180     char *result;
181     int len;
182 
183     if (path_is_absolute(filename)) {
184         return g_strdup(filename);
185     }
186 
187     if (path_has_protocol(base_path)) {
188         protocol_stripped = strchr(base_path, ':');
189         if (protocol_stripped) {
190             protocol_stripped++;
191         }
192     }
193     p = protocol_stripped ?: base_path;
194 
195     p1 = strrchr(base_path, '/');
196 #ifdef _WIN32
197     {
198         const char *p2;
199         p2 = strrchr(base_path, '\\');
200         if (!p1 || p2 > p1) {
201             p1 = p2;
202         }
203     }
204 #endif
205     if (p1) {
206         p1++;
207     } else {
208         p1 = base_path;
209     }
210     if (p1 > p) {
211         p = p1;
212     }
213     len = p - base_path;
214 
215     result = g_malloc(len + strlen(filename) + 1);
216     memcpy(result, base_path, len);
217     strcpy(result + len, filename);
218 
219     return result;
220 }
221 
222 /*
223  * Helper function for bdrv_parse_filename() implementations to remove optional
224  * protocol prefixes (especially "file:") from a filename and for putting the
225  * stripped filename into the options QDict if there is such a prefix.
226  */
227 void bdrv_parse_filename_strip_prefix(const char *filename, const char *prefix,
228                                       QDict *options)
229 {
230     if (strstart(filename, prefix, &filename)) {
231         /* Stripping the explicit protocol prefix may result in a protocol
232          * prefix being (wrongly) detected (if the filename contains a colon) */
233         if (path_has_protocol(filename)) {
234             GString *fat_filename;
235 
236             /* This means there is some colon before the first slash; therefore,
237              * this cannot be an absolute path */
238             assert(!path_is_absolute(filename));
239 
240             /* And we can thus fix the protocol detection issue by prefixing it
241              * by "./" */
242             fat_filename = g_string_new("./");
243             g_string_append(fat_filename, filename);
244 
245             assert(!path_has_protocol(fat_filename->str));
246 
247             qdict_put(options, "filename",
248                       qstring_from_gstring(fat_filename));
249         } else {
250             /* If no protocol prefix was detected, we can use the shortened
251              * filename as-is */
252             qdict_put_str(options, "filename", filename);
253         }
254     }
255 }
256 
257 
258 /* Returns whether the image file is opened as read-only. Note that this can
259  * return false and writing to the image file is still not possible because the
260  * image is inactivated. */
261 bool bdrv_is_read_only(BlockDriverState *bs)
262 {
263     return !(bs->open_flags & BDRV_O_RDWR);
264 }
265 
266 int bdrv_can_set_read_only(BlockDriverState *bs, bool read_only,
267                            bool ignore_allow_rdw, Error **errp)
268 {
269     /* Do not set read_only if copy_on_read is enabled */
270     if (bs->copy_on_read && read_only) {
271         error_setg(errp, "Can't set node '%s' to r/o with copy-on-read enabled",
272                    bdrv_get_device_or_node_name(bs));
273         return -EINVAL;
274     }
275 
276     /* Do not clear read_only if it is prohibited */
277     if (!read_only && !(bs->open_flags & BDRV_O_ALLOW_RDWR) &&
278         !ignore_allow_rdw)
279     {
280         error_setg(errp, "Node '%s' is read only",
281                    bdrv_get_device_or_node_name(bs));
282         return -EPERM;
283     }
284 
285     return 0;
286 }
287 
288 /*
289  * Called by a driver that can only provide a read-only image.
290  *
291  * Returns 0 if the node is already read-only or it could switch the node to
292  * read-only because BDRV_O_AUTO_RDONLY is set.
293  *
294  * Returns -EACCES if the node is read-write and BDRV_O_AUTO_RDONLY is not set
295  * or bdrv_can_set_read_only() forbids making the node read-only. If @errmsg
296  * is not NULL, it is used as the error message for the Error object.
297  */
298 int bdrv_apply_auto_read_only(BlockDriverState *bs, const char *errmsg,
299                               Error **errp)
300 {
301     int ret = 0;
302 
303     if (!(bs->open_flags & BDRV_O_RDWR)) {
304         return 0;
305     }
306     if (!(bs->open_flags & BDRV_O_AUTO_RDONLY)) {
307         goto fail;
308     }
309 
310     ret = bdrv_can_set_read_only(bs, true, false, NULL);
311     if (ret < 0) {
312         goto fail;
313     }
314 
315     bs->open_flags &= ~BDRV_O_RDWR;
316 
317     return 0;
318 
319 fail:
320     error_setg(errp, "%s", errmsg ?: "Image is read-only");
321     return -EACCES;
322 }
323 
324 /*
325  * If @backing is empty, this function returns NULL without setting
326  * @errp.  In all other cases, NULL will only be returned with @errp
327  * set.
328  *
329  * Therefore, a return value of NULL without @errp set means that
330  * there is no backing file; if @errp is set, there is one but its
331  * absolute filename cannot be generated.
332  */
333 char *bdrv_get_full_backing_filename_from_filename(const char *backed,
334                                                    const char *backing,
335                                                    Error **errp)
336 {
337     if (backing[0] == '\0') {
338         return NULL;
339     } else if (path_has_protocol(backing) || path_is_absolute(backing)) {
340         return g_strdup(backing);
341     } else if (backed[0] == '\0' || strstart(backed, "json:", NULL)) {
342         error_setg(errp, "Cannot use relative backing file names for '%s'",
343                    backed);
344         return NULL;
345     } else {
346         return path_combine(backed, backing);
347     }
348 }
349 
350 /*
351  * If @filename is empty or NULL, this function returns NULL without
352  * setting @errp.  In all other cases, NULL will only be returned with
353  * @errp set.
354  */
355 static char *bdrv_make_absolute_filename(BlockDriverState *relative_to,
356                                          const char *filename, Error **errp)
357 {
358     char *dir, *full_name;
359 
360     if (!filename || filename[0] == '\0') {
361         return NULL;
362     } else if (path_has_protocol(filename) || path_is_absolute(filename)) {
363         return g_strdup(filename);
364     }
365 
366     dir = bdrv_dirname(relative_to, errp);
367     if (!dir) {
368         return NULL;
369     }
370 
371     full_name = g_strconcat(dir, filename, NULL);
372     g_free(dir);
373     return full_name;
374 }
375 
376 char *bdrv_get_full_backing_filename(BlockDriverState *bs, Error **errp)
377 {
378     return bdrv_make_absolute_filename(bs, bs->backing_file, errp);
379 }
380 
381 void bdrv_register(BlockDriver *bdrv)
382 {
383     assert(bdrv->format_name);
384     QLIST_INSERT_HEAD(&bdrv_drivers, bdrv, list);
385 }
386 
387 BlockDriverState *bdrv_new(void)
388 {
389     BlockDriverState *bs;
390     int i;
391 
392     bs = g_new0(BlockDriverState, 1);
393     QLIST_INIT(&bs->dirty_bitmaps);
394     for (i = 0; i < BLOCK_OP_TYPE_MAX; i++) {
395         QLIST_INIT(&bs->op_blockers[i]);
396     }
397     qemu_co_mutex_init(&bs->reqs_lock);
398     qemu_mutex_init(&bs->dirty_bitmap_mutex);
399     bs->refcnt = 1;
400     bs->aio_context = qemu_get_aio_context();
401 
402     qemu_co_queue_init(&bs->flush_queue);
403 
404     for (i = 0; i < bdrv_drain_all_count; i++) {
405         bdrv_drained_begin(bs);
406     }
407 
408     QTAILQ_INSERT_TAIL(&all_bdrv_states, bs, bs_list);
409 
410     return bs;
411 }
412 
413 static BlockDriver *bdrv_do_find_format(const char *format_name)
414 {
415     BlockDriver *drv1;
416 
417     QLIST_FOREACH(drv1, &bdrv_drivers, list) {
418         if (!strcmp(drv1->format_name, format_name)) {
419             return drv1;
420         }
421     }
422 
423     return NULL;
424 }
425 
426 BlockDriver *bdrv_find_format(const char *format_name)
427 {
428     BlockDriver *drv1;
429     int i;
430 
431     drv1 = bdrv_do_find_format(format_name);
432     if (drv1) {
433         return drv1;
434     }
435 
436     /* The driver isn't registered, maybe we need to load a module */
437     for (i = 0; i < (int)ARRAY_SIZE(block_driver_modules); ++i) {
438         if (!strcmp(block_driver_modules[i].format_name, format_name)) {
439             block_module_load_one(block_driver_modules[i].library_name);
440             break;
441         }
442     }
443 
444     return bdrv_do_find_format(format_name);
445 }
446 
447 static int bdrv_format_is_whitelisted(const char *format_name, bool read_only)
448 {
449     static const char *whitelist_rw[] = {
450         CONFIG_BDRV_RW_WHITELIST
451         NULL
452     };
453     static const char *whitelist_ro[] = {
454         CONFIG_BDRV_RO_WHITELIST
455         NULL
456     };
457     const char **p;
458 
459     if (!whitelist_rw[0] && !whitelist_ro[0]) {
460         return 1;               /* no whitelist, anything goes */
461     }
462 
463     for (p = whitelist_rw; *p; p++) {
464         if (!strcmp(format_name, *p)) {
465             return 1;
466         }
467     }
468     if (read_only) {
469         for (p = whitelist_ro; *p; p++) {
470             if (!strcmp(format_name, *p)) {
471                 return 1;
472             }
473         }
474     }
475     return 0;
476 }
477 
478 int bdrv_is_whitelisted(BlockDriver *drv, bool read_only)
479 {
480     return bdrv_format_is_whitelisted(drv->format_name, read_only);
481 }
482 
483 bool bdrv_uses_whitelist(void)
484 {
485     return use_bdrv_whitelist;
486 }
487 
488 typedef struct CreateCo {
489     BlockDriver *drv;
490     char *filename;
491     QemuOpts *opts;
492     int ret;
493     Error *err;
494 } CreateCo;
495 
496 static void coroutine_fn bdrv_create_co_entry(void *opaque)
497 {
498     Error *local_err = NULL;
499     int ret;
500 
501     CreateCo *cco = opaque;
502     assert(cco->drv);
503 
504     ret = cco->drv->bdrv_co_create_opts(cco->drv,
505                                         cco->filename, cco->opts, &local_err);
506     error_propagate(&cco->err, local_err);
507     cco->ret = ret;
508 }
509 
510 int bdrv_create(BlockDriver *drv, const char* filename,
511                 QemuOpts *opts, Error **errp)
512 {
513     int ret;
514 
515     Coroutine *co;
516     CreateCo cco = {
517         .drv = drv,
518         .filename = g_strdup(filename),
519         .opts = opts,
520         .ret = NOT_DONE,
521         .err = NULL,
522     };
523 
524     if (!drv->bdrv_co_create_opts) {
525         error_setg(errp, "Driver '%s' does not support image creation", drv->format_name);
526         ret = -ENOTSUP;
527         goto out;
528     }
529 
530     if (qemu_in_coroutine()) {
531         /* Fast-path if already in coroutine context */
532         bdrv_create_co_entry(&cco);
533     } else {
534         co = qemu_coroutine_create(bdrv_create_co_entry, &cco);
535         qemu_coroutine_enter(co);
536         while (cco.ret == NOT_DONE) {
537             aio_poll(qemu_get_aio_context(), true);
538         }
539     }
540 
541     ret = cco.ret;
542     if (ret < 0) {
543         if (cco.err) {
544             error_propagate(errp, cco.err);
545         } else {
546             error_setg_errno(errp, -ret, "Could not create image");
547         }
548     }
549 
550 out:
551     g_free(cco.filename);
552     return ret;
553 }
554 
555 /**
556  * Helper function for bdrv_create_file_fallback(): Resize @blk to at
557  * least the given @minimum_size.
558  *
559  * On success, return @blk's actual length.
560  * Otherwise, return -errno.
561  */
562 static int64_t create_file_fallback_truncate(BlockBackend *blk,
563                                              int64_t minimum_size, Error **errp)
564 {
565     Error *local_err = NULL;
566     int64_t size;
567     int ret;
568 
569     ret = blk_truncate(blk, minimum_size, false, PREALLOC_MODE_OFF, 0,
570                        &local_err);
571     if (ret < 0 && ret != -ENOTSUP) {
572         error_propagate(errp, local_err);
573         return ret;
574     }
575 
576     size = blk_getlength(blk);
577     if (size < 0) {
578         error_free(local_err);
579         error_setg_errno(errp, -size,
580                          "Failed to inquire the new image file's length");
581         return size;
582     }
583 
584     if (size < minimum_size) {
585         /* Need to grow the image, but we failed to do that */
586         error_propagate(errp, local_err);
587         return -ENOTSUP;
588     }
589 
590     error_free(local_err);
591     local_err = NULL;
592 
593     return size;
594 }
595 
596 /**
597  * Helper function for bdrv_create_file_fallback(): Zero the first
598  * sector to remove any potentially pre-existing image header.
599  */
600 static int create_file_fallback_zero_first_sector(BlockBackend *blk,
601                                                   int64_t current_size,
602                                                   Error **errp)
603 {
604     int64_t bytes_to_clear;
605     int ret;
606 
607     bytes_to_clear = MIN(current_size, BDRV_SECTOR_SIZE);
608     if (bytes_to_clear) {
609         ret = blk_pwrite_zeroes(blk, 0, bytes_to_clear, BDRV_REQ_MAY_UNMAP);
610         if (ret < 0) {
611             error_setg_errno(errp, -ret,
612                              "Failed to clear the new image's first sector");
613             return ret;
614         }
615     }
616 
617     return 0;
618 }
619 
620 /**
621  * Simple implementation of bdrv_co_create_opts for protocol drivers
622  * which only support creation via opening a file
623  * (usually existing raw storage device)
624  */
625 int coroutine_fn bdrv_co_create_opts_simple(BlockDriver *drv,
626                                             const char *filename,
627                                             QemuOpts *opts,
628                                             Error **errp)
629 {
630     BlockBackend *blk;
631     QDict *options;
632     int64_t size = 0;
633     char *buf = NULL;
634     PreallocMode prealloc;
635     Error *local_err = NULL;
636     int ret;
637 
638     size = qemu_opt_get_size_del(opts, BLOCK_OPT_SIZE, 0);
639     buf = qemu_opt_get_del(opts, BLOCK_OPT_PREALLOC);
640     prealloc = qapi_enum_parse(&PreallocMode_lookup, buf,
641                                PREALLOC_MODE_OFF, &local_err);
642     g_free(buf);
643     if (local_err) {
644         error_propagate(errp, local_err);
645         return -EINVAL;
646     }
647 
648     if (prealloc != PREALLOC_MODE_OFF) {
649         error_setg(errp, "Unsupported preallocation mode '%s'",
650                    PreallocMode_str(prealloc));
651         return -ENOTSUP;
652     }
653 
654     options = qdict_new();
655     qdict_put_str(options, "driver", drv->format_name);
656 
657     blk = blk_new_open(filename, NULL, options,
658                        BDRV_O_RDWR | BDRV_O_RESIZE, errp);
659     if (!blk) {
660         error_prepend(errp, "Protocol driver '%s' does not support image "
661                       "creation, and opening the image failed: ",
662                       drv->format_name);
663         return -EINVAL;
664     }
665 
666     size = create_file_fallback_truncate(blk, size, errp);
667     if (size < 0) {
668         ret = size;
669         goto out;
670     }
671 
672     ret = create_file_fallback_zero_first_sector(blk, size, errp);
673     if (ret < 0) {
674         goto out;
675     }
676 
677     ret = 0;
678 out:
679     blk_unref(blk);
680     return ret;
681 }
682 
683 int bdrv_create_file(const char *filename, QemuOpts *opts, Error **errp)
684 {
685     QemuOpts *protocol_opts;
686     BlockDriver *drv;
687     QDict *qdict;
688     int ret;
689 
690     drv = bdrv_find_protocol(filename, true, errp);
691     if (drv == NULL) {
692         return -ENOENT;
693     }
694 
695     if (!drv->create_opts) {
696         error_setg(errp, "Driver '%s' does not support image creation",
697                    drv->format_name);
698         return -ENOTSUP;
699     }
700 
701     /*
702      * 'opts' contains a QemuOptsList with a combination of format and protocol
703      * default values.
704      *
705      * The format properly removes its options, but the default values remain
706      * in 'opts->list'.  So if the protocol has options with the same name
707      * (e.g. rbd has 'cluster_size' as qcow2), it will see the default values
708      * of the format, since for overlapping options, the format wins.
709      *
710      * To avoid this issue, lets convert QemuOpts to QDict, in this way we take
711      * only the set options, and then convert it back to QemuOpts, using the
712      * create_opts of the protocol. So the new QemuOpts, will contain only the
713      * protocol defaults.
714      */
715     qdict = qemu_opts_to_qdict(opts, NULL);
716     protocol_opts = qemu_opts_from_qdict(drv->create_opts, qdict, errp);
717     if (protocol_opts == NULL) {
718         ret = -EINVAL;
719         goto out;
720     }
721 
722     ret = bdrv_create(drv, filename, protocol_opts, errp);
723 out:
724     qemu_opts_del(protocol_opts);
725     qobject_unref(qdict);
726     return ret;
727 }
728 
729 int coroutine_fn bdrv_co_delete_file(BlockDriverState *bs, Error **errp)
730 {
731     Error *local_err = NULL;
732     int ret;
733 
734     assert(bs != NULL);
735 
736     if (!bs->drv) {
737         error_setg(errp, "Block node '%s' is not opened", bs->filename);
738         return -ENOMEDIUM;
739     }
740 
741     if (!bs->drv->bdrv_co_delete_file) {
742         error_setg(errp, "Driver '%s' does not support image deletion",
743                    bs->drv->format_name);
744         return -ENOTSUP;
745     }
746 
747     ret = bs->drv->bdrv_co_delete_file(bs, &local_err);
748     if (ret < 0) {
749         error_propagate(errp, local_err);
750     }
751 
752     return ret;
753 }
754 
755 void coroutine_fn bdrv_co_delete_file_noerr(BlockDriverState *bs)
756 {
757     Error *local_err = NULL;
758     int ret;
759 
760     if (!bs) {
761         return;
762     }
763 
764     ret = bdrv_co_delete_file(bs, &local_err);
765     /*
766      * ENOTSUP will happen if the block driver doesn't support
767      * the 'bdrv_co_delete_file' interface. This is a predictable
768      * scenario and shouldn't be reported back to the user.
769      */
770     if (ret == -ENOTSUP) {
771         error_free(local_err);
772     } else if (ret < 0) {
773         error_report_err(local_err);
774     }
775 }
776 
777 /**
778  * Try to get @bs's logical and physical block size.
779  * On success, store them in @bsz struct and return 0.
780  * On failure return -errno.
781  * @bs must not be empty.
782  */
783 int bdrv_probe_blocksizes(BlockDriverState *bs, BlockSizes *bsz)
784 {
785     BlockDriver *drv = bs->drv;
786     BlockDriverState *filtered = bdrv_filter_bs(bs);
787 
788     if (drv && drv->bdrv_probe_blocksizes) {
789         return drv->bdrv_probe_blocksizes(bs, bsz);
790     } else if (filtered) {
791         return bdrv_probe_blocksizes(filtered, bsz);
792     }
793 
794     return -ENOTSUP;
795 }
796 
797 /**
798  * Try to get @bs's geometry (cyls, heads, sectors).
799  * On success, store them in @geo struct and return 0.
800  * On failure return -errno.
801  * @bs must not be empty.
802  */
803 int bdrv_probe_geometry(BlockDriverState *bs, HDGeometry *geo)
804 {
805     BlockDriver *drv = bs->drv;
806     BlockDriverState *filtered = bdrv_filter_bs(bs);
807 
808     if (drv && drv->bdrv_probe_geometry) {
809         return drv->bdrv_probe_geometry(bs, geo);
810     } else if (filtered) {
811         return bdrv_probe_geometry(filtered, geo);
812     }
813 
814     return -ENOTSUP;
815 }
816 
817 /*
818  * Create a uniquely-named empty temporary file.
819  * Return 0 upon success, otherwise a negative errno value.
820  */
821 int get_tmp_filename(char *filename, int size)
822 {
823 #ifdef _WIN32
824     char temp_dir[MAX_PATH];
825     /* GetTempFileName requires that its output buffer (4th param)
826        have length MAX_PATH or greater.  */
827     assert(size >= MAX_PATH);
828     return (GetTempPath(MAX_PATH, temp_dir)
829             && GetTempFileName(temp_dir, "qem", 0, filename)
830             ? 0 : -GetLastError());
831 #else
832     int fd;
833     const char *tmpdir;
834     tmpdir = getenv("TMPDIR");
835     if (!tmpdir) {
836         tmpdir = "/var/tmp";
837     }
838     if (snprintf(filename, size, "%s/vl.XXXXXX", tmpdir) >= size) {
839         return -EOVERFLOW;
840     }
841     fd = mkstemp(filename);
842     if (fd < 0) {
843         return -errno;
844     }
845     if (close(fd) != 0) {
846         unlink(filename);
847         return -errno;
848     }
849     return 0;
850 #endif
851 }
852 
853 /*
854  * Detect host devices. By convention, /dev/cdrom[N] is always
855  * recognized as a host CDROM.
856  */
857 static BlockDriver *find_hdev_driver(const char *filename)
858 {
859     int score_max = 0, score;
860     BlockDriver *drv = NULL, *d;
861 
862     QLIST_FOREACH(d, &bdrv_drivers, list) {
863         if (d->bdrv_probe_device) {
864             score = d->bdrv_probe_device(filename);
865             if (score > score_max) {
866                 score_max = score;
867                 drv = d;
868             }
869         }
870     }
871 
872     return drv;
873 }
874 
875 static BlockDriver *bdrv_do_find_protocol(const char *protocol)
876 {
877     BlockDriver *drv1;
878 
879     QLIST_FOREACH(drv1, &bdrv_drivers, list) {
880         if (drv1->protocol_name && !strcmp(drv1->protocol_name, protocol)) {
881             return drv1;
882         }
883     }
884 
885     return NULL;
886 }
887 
888 BlockDriver *bdrv_find_protocol(const char *filename,
889                                 bool allow_protocol_prefix,
890                                 Error **errp)
891 {
892     BlockDriver *drv1;
893     char protocol[128];
894     int len;
895     const char *p;
896     int i;
897 
898     /* TODO Drivers without bdrv_file_open must be specified explicitly */
899 
900     /*
901      * XXX(hch): we really should not let host device detection
902      * override an explicit protocol specification, but moving this
903      * later breaks access to device names with colons in them.
904      * Thanks to the brain-dead persistent naming schemes on udev-
905      * based Linux systems those actually are quite common.
906      */
907     drv1 = find_hdev_driver(filename);
908     if (drv1) {
909         return drv1;
910     }
911 
912     if (!path_has_protocol(filename) || !allow_protocol_prefix) {
913         return &bdrv_file;
914     }
915 
916     p = strchr(filename, ':');
917     assert(p != NULL);
918     len = p - filename;
919     if (len > sizeof(protocol) - 1)
920         len = sizeof(protocol) - 1;
921     memcpy(protocol, filename, len);
922     protocol[len] = '\0';
923 
924     drv1 = bdrv_do_find_protocol(protocol);
925     if (drv1) {
926         return drv1;
927     }
928 
929     for (i = 0; i < (int)ARRAY_SIZE(block_driver_modules); ++i) {
930         if (block_driver_modules[i].protocol_name &&
931             !strcmp(block_driver_modules[i].protocol_name, protocol)) {
932             block_module_load_one(block_driver_modules[i].library_name);
933             break;
934         }
935     }
936 
937     drv1 = bdrv_do_find_protocol(protocol);
938     if (!drv1) {
939         error_setg(errp, "Unknown protocol '%s'", protocol);
940     }
941     return drv1;
942 }
943 
944 /*
945  * Guess image format by probing its contents.
946  * This is not a good idea when your image is raw (CVE-2008-2004), but
947  * we do it anyway for backward compatibility.
948  *
949  * @buf         contains the image's first @buf_size bytes.
950  * @buf_size    is the buffer size in bytes (generally BLOCK_PROBE_BUF_SIZE,
951  *              but can be smaller if the image file is smaller)
952  * @filename    is its filename.
953  *
954  * For all block drivers, call the bdrv_probe() method to get its
955  * probing score.
956  * Return the first block driver with the highest probing score.
957  */
958 BlockDriver *bdrv_probe_all(const uint8_t *buf, int buf_size,
959                             const char *filename)
960 {
961     int score_max = 0, score;
962     BlockDriver *drv = NULL, *d;
963 
964     QLIST_FOREACH(d, &bdrv_drivers, list) {
965         if (d->bdrv_probe) {
966             score = d->bdrv_probe(buf, buf_size, filename);
967             if (score > score_max) {
968                 score_max = score;
969                 drv = d;
970             }
971         }
972     }
973 
974     return drv;
975 }
976 
977 static int find_image_format(BlockBackend *file, const char *filename,
978                              BlockDriver **pdrv, Error **errp)
979 {
980     BlockDriver *drv;
981     uint8_t buf[BLOCK_PROBE_BUF_SIZE];
982     int ret = 0;
983 
984     /* Return the raw BlockDriver * to scsi-generic devices or empty drives */
985     if (blk_is_sg(file) || !blk_is_inserted(file) || blk_getlength(file) == 0) {
986         *pdrv = &bdrv_raw;
987         return ret;
988     }
989 
990     ret = blk_pread(file, 0, buf, sizeof(buf));
991     if (ret < 0) {
992         error_setg_errno(errp, -ret, "Could not read image for determining its "
993                          "format");
994         *pdrv = NULL;
995         return ret;
996     }
997 
998     drv = bdrv_probe_all(buf, ret, filename);
999     if (!drv) {
1000         error_setg(errp, "Could not determine image format: No compatible "
1001                    "driver found");
1002         ret = -ENOENT;
1003     }
1004     *pdrv = drv;
1005     return ret;
1006 }
1007 
1008 /**
1009  * Set the current 'total_sectors' value
1010  * Return 0 on success, -errno on error.
1011  */
1012 int refresh_total_sectors(BlockDriverState *bs, int64_t hint)
1013 {
1014     BlockDriver *drv = bs->drv;
1015 
1016     if (!drv) {
1017         return -ENOMEDIUM;
1018     }
1019 
1020     /* Do not attempt drv->bdrv_getlength() on scsi-generic devices */
1021     if (bdrv_is_sg(bs))
1022         return 0;
1023 
1024     /* query actual device if possible, otherwise just trust the hint */
1025     if (drv->bdrv_getlength) {
1026         int64_t length = drv->bdrv_getlength(bs);
1027         if (length < 0) {
1028             return length;
1029         }
1030         hint = DIV_ROUND_UP(length, BDRV_SECTOR_SIZE);
1031     }
1032 
1033     bs->total_sectors = hint;
1034 
1035     if (bs->total_sectors * BDRV_SECTOR_SIZE > BDRV_MAX_LENGTH) {
1036         return -EFBIG;
1037     }
1038 
1039     return 0;
1040 }
1041 
1042 /**
1043  * Combines a QDict of new block driver @options with any missing options taken
1044  * from @old_options, so that leaving out an option defaults to its old value.
1045  */
1046 static void bdrv_join_options(BlockDriverState *bs, QDict *options,
1047                               QDict *old_options)
1048 {
1049     if (bs->drv && bs->drv->bdrv_join_options) {
1050         bs->drv->bdrv_join_options(options, old_options);
1051     } else {
1052         qdict_join(options, old_options, false);
1053     }
1054 }
1055 
1056 static BlockdevDetectZeroesOptions bdrv_parse_detect_zeroes(QemuOpts *opts,
1057                                                             int open_flags,
1058                                                             Error **errp)
1059 {
1060     Error *local_err = NULL;
1061     char *value = qemu_opt_get_del(opts, "detect-zeroes");
1062     BlockdevDetectZeroesOptions detect_zeroes =
1063         qapi_enum_parse(&BlockdevDetectZeroesOptions_lookup, value,
1064                         BLOCKDEV_DETECT_ZEROES_OPTIONS_OFF, &local_err);
1065     g_free(value);
1066     if (local_err) {
1067         error_propagate(errp, local_err);
1068         return detect_zeroes;
1069     }
1070 
1071     if (detect_zeroes == BLOCKDEV_DETECT_ZEROES_OPTIONS_UNMAP &&
1072         !(open_flags & BDRV_O_UNMAP))
1073     {
1074         error_setg(errp, "setting detect-zeroes to unmap is not allowed "
1075                    "without setting discard operation to unmap");
1076     }
1077 
1078     return detect_zeroes;
1079 }
1080 
1081 /**
1082  * Set open flags for aio engine
1083  *
1084  * Return 0 on success, -1 if the engine specified is invalid
1085  */
1086 int bdrv_parse_aio(const char *mode, int *flags)
1087 {
1088     if (!strcmp(mode, "threads")) {
1089         /* do nothing, default */
1090     } else if (!strcmp(mode, "native")) {
1091         *flags |= BDRV_O_NATIVE_AIO;
1092 #ifdef CONFIG_LINUX_IO_URING
1093     } else if (!strcmp(mode, "io_uring")) {
1094         *flags |= BDRV_O_IO_URING;
1095 #endif
1096     } else {
1097         return -1;
1098     }
1099 
1100     return 0;
1101 }
1102 
1103 /**
1104  * Set open flags for a given discard mode
1105  *
1106  * Return 0 on success, -1 if the discard mode was invalid.
1107  */
1108 int bdrv_parse_discard_flags(const char *mode, int *flags)
1109 {
1110     *flags &= ~BDRV_O_UNMAP;
1111 
1112     if (!strcmp(mode, "off") || !strcmp(mode, "ignore")) {
1113         /* do nothing */
1114     } else if (!strcmp(mode, "on") || !strcmp(mode, "unmap")) {
1115         *flags |= BDRV_O_UNMAP;
1116     } else {
1117         return -1;
1118     }
1119 
1120     return 0;
1121 }
1122 
1123 /**
1124  * Set open flags for a given cache mode
1125  *
1126  * Return 0 on success, -1 if the cache mode was invalid.
1127  */
1128 int bdrv_parse_cache_mode(const char *mode, int *flags, bool *writethrough)
1129 {
1130     *flags &= ~BDRV_O_CACHE_MASK;
1131 
1132     if (!strcmp(mode, "off") || !strcmp(mode, "none")) {
1133         *writethrough = false;
1134         *flags |= BDRV_O_NOCACHE;
1135     } else if (!strcmp(mode, "directsync")) {
1136         *writethrough = true;
1137         *flags |= BDRV_O_NOCACHE;
1138     } else if (!strcmp(mode, "writeback")) {
1139         *writethrough = false;
1140     } else if (!strcmp(mode, "unsafe")) {
1141         *writethrough = false;
1142         *flags |= BDRV_O_NO_FLUSH;
1143     } else if (!strcmp(mode, "writethrough")) {
1144         *writethrough = true;
1145     } else {
1146         return -1;
1147     }
1148 
1149     return 0;
1150 }
1151 
1152 static char *bdrv_child_get_parent_desc(BdrvChild *c)
1153 {
1154     BlockDriverState *parent = c->opaque;
1155     return g_strdup_printf("node '%s'", bdrv_get_node_name(parent));
1156 }
1157 
1158 static void bdrv_child_cb_drained_begin(BdrvChild *child)
1159 {
1160     BlockDriverState *bs = child->opaque;
1161     bdrv_do_drained_begin_quiesce(bs, NULL, false);
1162 }
1163 
1164 static bool bdrv_child_cb_drained_poll(BdrvChild *child)
1165 {
1166     BlockDriverState *bs = child->opaque;
1167     return bdrv_drain_poll(bs, false, NULL, false);
1168 }
1169 
1170 static void bdrv_child_cb_drained_end(BdrvChild *child,
1171                                       int *drained_end_counter)
1172 {
1173     BlockDriverState *bs = child->opaque;
1174     bdrv_drained_end_no_poll(bs, drained_end_counter);
1175 }
1176 
1177 static int bdrv_child_cb_inactivate(BdrvChild *child)
1178 {
1179     BlockDriverState *bs = child->opaque;
1180     assert(bs->open_flags & BDRV_O_INACTIVE);
1181     return 0;
1182 }
1183 
1184 static bool bdrv_child_cb_can_set_aio_ctx(BdrvChild *child, AioContext *ctx,
1185                                           GSList **ignore, Error **errp)
1186 {
1187     BlockDriverState *bs = child->opaque;
1188     return bdrv_can_set_aio_context(bs, ctx, ignore, errp);
1189 }
1190 
1191 static void bdrv_child_cb_set_aio_ctx(BdrvChild *child, AioContext *ctx,
1192                                       GSList **ignore)
1193 {
1194     BlockDriverState *bs = child->opaque;
1195     return bdrv_set_aio_context_ignore(bs, ctx, ignore);
1196 }
1197 
1198 /*
1199  * Returns the options and flags that a temporary snapshot should get, based on
1200  * the originally requested flags (the originally requested image will have
1201  * flags like a backing file)
1202  */
1203 static void bdrv_temp_snapshot_options(int *child_flags, QDict *child_options,
1204                                        int parent_flags, QDict *parent_options)
1205 {
1206     *child_flags = (parent_flags & ~BDRV_O_SNAPSHOT) | BDRV_O_TEMPORARY;
1207 
1208     /* For temporary files, unconditional cache=unsafe is fine */
1209     qdict_set_default_str(child_options, BDRV_OPT_CACHE_DIRECT, "off");
1210     qdict_set_default_str(child_options, BDRV_OPT_CACHE_NO_FLUSH, "on");
1211 
1212     /* Copy the read-only and discard options from the parent */
1213     qdict_copy_default(child_options, parent_options, BDRV_OPT_READ_ONLY);
1214     qdict_copy_default(child_options, parent_options, BDRV_OPT_DISCARD);
1215 
1216     /* aio=native doesn't work for cache.direct=off, so disable it for the
1217      * temporary snapshot */
1218     *child_flags &= ~BDRV_O_NATIVE_AIO;
1219 }
1220 
1221 static void bdrv_backing_attach(BdrvChild *c)
1222 {
1223     BlockDriverState *parent = c->opaque;
1224     BlockDriverState *backing_hd = c->bs;
1225 
1226     assert(!parent->backing_blocker);
1227     error_setg(&parent->backing_blocker,
1228                "node is used as backing hd of '%s'",
1229                bdrv_get_device_or_node_name(parent));
1230 
1231     bdrv_refresh_filename(backing_hd);
1232 
1233     parent->open_flags &= ~BDRV_O_NO_BACKING;
1234 
1235     bdrv_op_block_all(backing_hd, parent->backing_blocker);
1236     /* Otherwise we won't be able to commit or stream */
1237     bdrv_op_unblock(backing_hd, BLOCK_OP_TYPE_COMMIT_TARGET,
1238                     parent->backing_blocker);
1239     bdrv_op_unblock(backing_hd, BLOCK_OP_TYPE_STREAM,
1240                     parent->backing_blocker);
1241     /*
1242      * We do backup in 3 ways:
1243      * 1. drive backup
1244      *    The target bs is new opened, and the source is top BDS
1245      * 2. blockdev backup
1246      *    Both the source and the target are top BDSes.
1247      * 3. internal backup(used for block replication)
1248      *    Both the source and the target are backing file
1249      *
1250      * In case 1 and 2, neither the source nor the target is the backing file.
1251      * In case 3, we will block the top BDS, so there is only one block job
1252      * for the top BDS and its backing chain.
1253      */
1254     bdrv_op_unblock(backing_hd, BLOCK_OP_TYPE_BACKUP_SOURCE,
1255                     parent->backing_blocker);
1256     bdrv_op_unblock(backing_hd, BLOCK_OP_TYPE_BACKUP_TARGET,
1257                     parent->backing_blocker);
1258 }
1259 
1260 static void bdrv_backing_detach(BdrvChild *c)
1261 {
1262     BlockDriverState *parent = c->opaque;
1263 
1264     assert(parent->backing_blocker);
1265     bdrv_op_unblock_all(c->bs, parent->backing_blocker);
1266     error_free(parent->backing_blocker);
1267     parent->backing_blocker = NULL;
1268 }
1269 
1270 static int bdrv_backing_update_filename(BdrvChild *c, BlockDriverState *base,
1271                                         const char *filename, Error **errp)
1272 {
1273     BlockDriverState *parent = c->opaque;
1274     bool read_only = bdrv_is_read_only(parent);
1275     int ret;
1276 
1277     if (read_only) {
1278         ret = bdrv_reopen_set_read_only(parent, false, errp);
1279         if (ret < 0) {
1280             return ret;
1281         }
1282     }
1283 
1284     ret = bdrv_change_backing_file(parent, filename,
1285                                    base->drv ? base->drv->format_name : "",
1286                                    false);
1287     if (ret < 0) {
1288         error_setg_errno(errp, -ret, "Could not update backing file link");
1289     }
1290 
1291     if (read_only) {
1292         bdrv_reopen_set_read_only(parent, true, NULL);
1293     }
1294 
1295     return ret;
1296 }
1297 
1298 /*
1299  * Returns the options and flags that a generic child of a BDS should
1300  * get, based on the given options and flags for the parent BDS.
1301  */
1302 static void bdrv_inherited_options(BdrvChildRole role, bool parent_is_format,
1303                                    int *child_flags, QDict *child_options,
1304                                    int parent_flags, QDict *parent_options)
1305 {
1306     int flags = parent_flags;
1307 
1308     /*
1309      * First, decide whether to set, clear, or leave BDRV_O_PROTOCOL.
1310      * Generally, the question to answer is: Should this child be
1311      * format-probed by default?
1312      */
1313 
1314     /*
1315      * Pure and non-filtered data children of non-format nodes should
1316      * be probed by default (even when the node itself has BDRV_O_PROTOCOL
1317      * set).  This only affects a very limited set of drivers (namely
1318      * quorum and blkverify when this comment was written).
1319      * Force-clear BDRV_O_PROTOCOL then.
1320      */
1321     if (!parent_is_format &&
1322         (role & BDRV_CHILD_DATA) &&
1323         !(role & (BDRV_CHILD_METADATA | BDRV_CHILD_FILTERED)))
1324     {
1325         flags &= ~BDRV_O_PROTOCOL;
1326     }
1327 
1328     /*
1329      * All children of format nodes (except for COW children) and all
1330      * metadata children in general should never be format-probed.
1331      * Force-set BDRV_O_PROTOCOL then.
1332      */
1333     if ((parent_is_format && !(role & BDRV_CHILD_COW)) ||
1334         (role & BDRV_CHILD_METADATA))
1335     {
1336         flags |= BDRV_O_PROTOCOL;
1337     }
1338 
1339     /*
1340      * If the cache mode isn't explicitly set, inherit direct and no-flush from
1341      * the parent.
1342      */
1343     qdict_copy_default(child_options, parent_options, BDRV_OPT_CACHE_DIRECT);
1344     qdict_copy_default(child_options, parent_options, BDRV_OPT_CACHE_NO_FLUSH);
1345     qdict_copy_default(child_options, parent_options, BDRV_OPT_FORCE_SHARE);
1346 
1347     if (role & BDRV_CHILD_COW) {
1348         /* backing files are opened read-only by default */
1349         qdict_set_default_str(child_options, BDRV_OPT_READ_ONLY, "on");
1350         qdict_set_default_str(child_options, BDRV_OPT_AUTO_READ_ONLY, "off");
1351     } else {
1352         /* Inherit the read-only option from the parent if it's not set */
1353         qdict_copy_default(child_options, parent_options, BDRV_OPT_READ_ONLY);
1354         qdict_copy_default(child_options, parent_options,
1355                            BDRV_OPT_AUTO_READ_ONLY);
1356     }
1357 
1358     /*
1359      * bdrv_co_pdiscard() respects unmap policy for the parent, so we
1360      * can default to enable it on lower layers regardless of the
1361      * parent option.
1362      */
1363     qdict_set_default_str(child_options, BDRV_OPT_DISCARD, "unmap");
1364 
1365     /* Clear flags that only apply to the top layer */
1366     flags &= ~(BDRV_O_SNAPSHOT | BDRV_O_NO_BACKING | BDRV_O_COPY_ON_READ);
1367 
1368     if (role & BDRV_CHILD_METADATA) {
1369         flags &= ~BDRV_O_NO_IO;
1370     }
1371     if (role & BDRV_CHILD_COW) {
1372         flags &= ~BDRV_O_TEMPORARY;
1373     }
1374 
1375     *child_flags = flags;
1376 }
1377 
1378 static void bdrv_child_cb_attach(BdrvChild *child)
1379 {
1380     BlockDriverState *bs = child->opaque;
1381 
1382     if (child->role & BDRV_CHILD_COW) {
1383         bdrv_backing_attach(child);
1384     }
1385 
1386     bdrv_apply_subtree_drain(child, bs);
1387 }
1388 
1389 static void bdrv_child_cb_detach(BdrvChild *child)
1390 {
1391     BlockDriverState *bs = child->opaque;
1392 
1393     if (child->role & BDRV_CHILD_COW) {
1394         bdrv_backing_detach(child);
1395     }
1396 
1397     bdrv_unapply_subtree_drain(child, bs);
1398 }
1399 
1400 static int bdrv_child_cb_update_filename(BdrvChild *c, BlockDriverState *base,
1401                                          const char *filename, Error **errp)
1402 {
1403     if (c->role & BDRV_CHILD_COW) {
1404         return bdrv_backing_update_filename(c, base, filename, errp);
1405     }
1406     return 0;
1407 }
1408 
1409 AioContext *child_of_bds_get_parent_aio_context(BdrvChild *c)
1410 {
1411     BlockDriverState *bs = c->opaque;
1412 
1413     return bdrv_get_aio_context(bs);
1414 }
1415 
1416 const BdrvChildClass child_of_bds = {
1417     .parent_is_bds   = true,
1418     .get_parent_desc = bdrv_child_get_parent_desc,
1419     .inherit_options = bdrv_inherited_options,
1420     .drained_begin   = bdrv_child_cb_drained_begin,
1421     .drained_poll    = bdrv_child_cb_drained_poll,
1422     .drained_end     = bdrv_child_cb_drained_end,
1423     .attach          = bdrv_child_cb_attach,
1424     .detach          = bdrv_child_cb_detach,
1425     .inactivate      = bdrv_child_cb_inactivate,
1426     .can_set_aio_ctx = bdrv_child_cb_can_set_aio_ctx,
1427     .set_aio_ctx     = bdrv_child_cb_set_aio_ctx,
1428     .update_filename = bdrv_child_cb_update_filename,
1429     .get_parent_aio_context = child_of_bds_get_parent_aio_context,
1430 };
1431 
1432 AioContext *bdrv_child_get_parent_aio_context(BdrvChild *c)
1433 {
1434     return c->klass->get_parent_aio_context(c);
1435 }
1436 
1437 static int bdrv_open_flags(BlockDriverState *bs, int flags)
1438 {
1439     int open_flags = flags;
1440 
1441     /*
1442      * Clear flags that are internal to the block layer before opening the
1443      * image.
1444      */
1445     open_flags &= ~(BDRV_O_SNAPSHOT | BDRV_O_NO_BACKING | BDRV_O_PROTOCOL);
1446 
1447     return open_flags;
1448 }
1449 
1450 static void update_flags_from_options(int *flags, QemuOpts *opts)
1451 {
1452     *flags &= ~(BDRV_O_CACHE_MASK | BDRV_O_RDWR | BDRV_O_AUTO_RDONLY);
1453 
1454     if (qemu_opt_get_bool_del(opts, BDRV_OPT_CACHE_NO_FLUSH, false)) {
1455         *flags |= BDRV_O_NO_FLUSH;
1456     }
1457 
1458     if (qemu_opt_get_bool_del(opts, BDRV_OPT_CACHE_DIRECT, false)) {
1459         *flags |= BDRV_O_NOCACHE;
1460     }
1461 
1462     if (!qemu_opt_get_bool_del(opts, BDRV_OPT_READ_ONLY, false)) {
1463         *flags |= BDRV_O_RDWR;
1464     }
1465 
1466     if (qemu_opt_get_bool_del(opts, BDRV_OPT_AUTO_READ_ONLY, false)) {
1467         *flags |= BDRV_O_AUTO_RDONLY;
1468     }
1469 }
1470 
1471 static void update_options_from_flags(QDict *options, int flags)
1472 {
1473     if (!qdict_haskey(options, BDRV_OPT_CACHE_DIRECT)) {
1474         qdict_put_bool(options, BDRV_OPT_CACHE_DIRECT, flags & BDRV_O_NOCACHE);
1475     }
1476     if (!qdict_haskey(options, BDRV_OPT_CACHE_NO_FLUSH)) {
1477         qdict_put_bool(options, BDRV_OPT_CACHE_NO_FLUSH,
1478                        flags & BDRV_O_NO_FLUSH);
1479     }
1480     if (!qdict_haskey(options, BDRV_OPT_READ_ONLY)) {
1481         qdict_put_bool(options, BDRV_OPT_READ_ONLY, !(flags & BDRV_O_RDWR));
1482     }
1483     if (!qdict_haskey(options, BDRV_OPT_AUTO_READ_ONLY)) {
1484         qdict_put_bool(options, BDRV_OPT_AUTO_READ_ONLY,
1485                        flags & BDRV_O_AUTO_RDONLY);
1486     }
1487 }
1488 
1489 static void bdrv_assign_node_name(BlockDriverState *bs,
1490                                   const char *node_name,
1491                                   Error **errp)
1492 {
1493     char *gen_node_name = NULL;
1494 
1495     if (!node_name) {
1496         node_name = gen_node_name = id_generate(ID_BLOCK);
1497     } else if (!id_wellformed(node_name)) {
1498         /*
1499          * Check for empty string or invalid characters, but not if it is
1500          * generated (generated names use characters not available to the user)
1501          */
1502         error_setg(errp, "Invalid node-name: '%s'", node_name);
1503         return;
1504     }
1505 
1506     /* takes care of avoiding namespaces collisions */
1507     if (blk_by_name(node_name)) {
1508         error_setg(errp, "node-name=%s is conflicting with a device id",
1509                    node_name);
1510         goto out;
1511     }
1512 
1513     /* takes care of avoiding duplicates node names */
1514     if (bdrv_find_node(node_name)) {
1515         error_setg(errp, "Duplicate nodes with node-name='%s'", node_name);
1516         goto out;
1517     }
1518 
1519     /* Make sure that the node name isn't truncated */
1520     if (strlen(node_name) >= sizeof(bs->node_name)) {
1521         error_setg(errp, "Node name too long");
1522         goto out;
1523     }
1524 
1525     /* copy node name into the bs and insert it into the graph list */
1526     pstrcpy(bs->node_name, sizeof(bs->node_name), node_name);
1527     QTAILQ_INSERT_TAIL(&graph_bdrv_states, bs, node_list);
1528 out:
1529     g_free(gen_node_name);
1530 }
1531 
1532 static int bdrv_open_driver(BlockDriverState *bs, BlockDriver *drv,
1533                             const char *node_name, QDict *options,
1534                             int open_flags, Error **errp)
1535 {
1536     Error *local_err = NULL;
1537     int i, ret;
1538 
1539     bdrv_assign_node_name(bs, node_name, &local_err);
1540     if (local_err) {
1541         error_propagate(errp, local_err);
1542         return -EINVAL;
1543     }
1544 
1545     bs->drv = drv;
1546     bs->opaque = g_malloc0(drv->instance_size);
1547 
1548     if (drv->bdrv_file_open) {
1549         assert(!drv->bdrv_needs_filename || bs->filename[0]);
1550         ret = drv->bdrv_file_open(bs, options, open_flags, &local_err);
1551     } else if (drv->bdrv_open) {
1552         ret = drv->bdrv_open(bs, options, open_flags, &local_err);
1553     } else {
1554         ret = 0;
1555     }
1556 
1557     if (ret < 0) {
1558         if (local_err) {
1559             error_propagate(errp, local_err);
1560         } else if (bs->filename[0]) {
1561             error_setg_errno(errp, -ret, "Could not open '%s'", bs->filename);
1562         } else {
1563             error_setg_errno(errp, -ret, "Could not open image");
1564         }
1565         goto open_failed;
1566     }
1567 
1568     ret = refresh_total_sectors(bs, bs->total_sectors);
1569     if (ret < 0) {
1570         error_setg_errno(errp, -ret, "Could not refresh total sector count");
1571         return ret;
1572     }
1573 
1574     bdrv_refresh_limits(bs, NULL, &local_err);
1575     if (local_err) {
1576         error_propagate(errp, local_err);
1577         return -EINVAL;
1578     }
1579 
1580     assert(bdrv_opt_mem_align(bs) != 0);
1581     assert(bdrv_min_mem_align(bs) != 0);
1582     assert(is_power_of_2(bs->bl.request_alignment));
1583 
1584     for (i = 0; i < bs->quiesce_counter; i++) {
1585         if (drv->bdrv_co_drain_begin) {
1586             drv->bdrv_co_drain_begin(bs);
1587         }
1588     }
1589 
1590     return 0;
1591 open_failed:
1592     bs->drv = NULL;
1593     if (bs->file != NULL) {
1594         bdrv_unref_child(bs, bs->file);
1595         bs->file = NULL;
1596     }
1597     g_free(bs->opaque);
1598     bs->opaque = NULL;
1599     return ret;
1600 }
1601 
1602 BlockDriverState *bdrv_new_open_driver(BlockDriver *drv, const char *node_name,
1603                                        int flags, Error **errp)
1604 {
1605     BlockDriverState *bs;
1606     int ret;
1607 
1608     bs = bdrv_new();
1609     bs->open_flags = flags;
1610     bs->explicit_options = qdict_new();
1611     bs->options = qdict_new();
1612     bs->opaque = NULL;
1613 
1614     update_options_from_flags(bs->options, flags);
1615 
1616     ret = bdrv_open_driver(bs, drv, node_name, bs->options, flags, errp);
1617     if (ret < 0) {
1618         qobject_unref(bs->explicit_options);
1619         bs->explicit_options = NULL;
1620         qobject_unref(bs->options);
1621         bs->options = NULL;
1622         bdrv_unref(bs);
1623         return NULL;
1624     }
1625 
1626     return bs;
1627 }
1628 
1629 QemuOptsList bdrv_runtime_opts = {
1630     .name = "bdrv_common",
1631     .head = QTAILQ_HEAD_INITIALIZER(bdrv_runtime_opts.head),
1632     .desc = {
1633         {
1634             .name = "node-name",
1635             .type = QEMU_OPT_STRING,
1636             .help = "Node name of the block device node",
1637         },
1638         {
1639             .name = "driver",
1640             .type = QEMU_OPT_STRING,
1641             .help = "Block driver to use for the node",
1642         },
1643         {
1644             .name = BDRV_OPT_CACHE_DIRECT,
1645             .type = QEMU_OPT_BOOL,
1646             .help = "Bypass software writeback cache on the host",
1647         },
1648         {
1649             .name = BDRV_OPT_CACHE_NO_FLUSH,
1650             .type = QEMU_OPT_BOOL,
1651             .help = "Ignore flush requests",
1652         },
1653         {
1654             .name = BDRV_OPT_READ_ONLY,
1655             .type = QEMU_OPT_BOOL,
1656             .help = "Node is opened in read-only mode",
1657         },
1658         {
1659             .name = BDRV_OPT_AUTO_READ_ONLY,
1660             .type = QEMU_OPT_BOOL,
1661             .help = "Node can become read-only if opening read-write fails",
1662         },
1663         {
1664             .name = "detect-zeroes",
1665             .type = QEMU_OPT_STRING,
1666             .help = "try to optimize zero writes (off, on, unmap)",
1667         },
1668         {
1669             .name = BDRV_OPT_DISCARD,
1670             .type = QEMU_OPT_STRING,
1671             .help = "discard operation (ignore/off, unmap/on)",
1672         },
1673         {
1674             .name = BDRV_OPT_FORCE_SHARE,
1675             .type = QEMU_OPT_BOOL,
1676             .help = "always accept other writers (default: off)",
1677         },
1678         { /* end of list */ }
1679     },
1680 };
1681 
1682 QemuOptsList bdrv_create_opts_simple = {
1683     .name = "simple-create-opts",
1684     .head = QTAILQ_HEAD_INITIALIZER(bdrv_create_opts_simple.head),
1685     .desc = {
1686         {
1687             .name = BLOCK_OPT_SIZE,
1688             .type = QEMU_OPT_SIZE,
1689             .help = "Virtual disk size"
1690         },
1691         {
1692             .name = BLOCK_OPT_PREALLOC,
1693             .type = QEMU_OPT_STRING,
1694             .help = "Preallocation mode (allowed values: off)"
1695         },
1696         { /* end of list */ }
1697     }
1698 };
1699 
1700 /*
1701  * Common part for opening disk images and files
1702  *
1703  * Removes all processed options from *options.
1704  */
1705 static int bdrv_open_common(BlockDriverState *bs, BlockBackend *file,
1706                             QDict *options, Error **errp)
1707 {
1708     int ret, open_flags;
1709     const char *filename;
1710     const char *driver_name = NULL;
1711     const char *node_name = NULL;
1712     const char *discard;
1713     QemuOpts *opts;
1714     BlockDriver *drv;
1715     Error *local_err = NULL;
1716     bool ro;
1717 
1718     assert(bs->file == NULL);
1719     assert(options != NULL && bs->options != options);
1720 
1721     opts = qemu_opts_create(&bdrv_runtime_opts, NULL, 0, &error_abort);
1722     if (!qemu_opts_absorb_qdict(opts, options, errp)) {
1723         ret = -EINVAL;
1724         goto fail_opts;
1725     }
1726 
1727     update_flags_from_options(&bs->open_flags, opts);
1728 
1729     driver_name = qemu_opt_get(opts, "driver");
1730     drv = bdrv_find_format(driver_name);
1731     assert(drv != NULL);
1732 
1733     bs->force_share = qemu_opt_get_bool(opts, BDRV_OPT_FORCE_SHARE, false);
1734 
1735     if (bs->force_share && (bs->open_flags & BDRV_O_RDWR)) {
1736         error_setg(errp,
1737                    BDRV_OPT_FORCE_SHARE
1738                    "=on can only be used with read-only images");
1739         ret = -EINVAL;
1740         goto fail_opts;
1741     }
1742 
1743     if (file != NULL) {
1744         bdrv_refresh_filename(blk_bs(file));
1745         filename = blk_bs(file)->filename;
1746     } else {
1747         /*
1748          * Caution: while qdict_get_try_str() is fine, getting
1749          * non-string types would require more care.  When @options
1750          * come from -blockdev or blockdev_add, its members are typed
1751          * according to the QAPI schema, but when they come from
1752          * -drive, they're all QString.
1753          */
1754         filename = qdict_get_try_str(options, "filename");
1755     }
1756 
1757     if (drv->bdrv_needs_filename && (!filename || !filename[0])) {
1758         error_setg(errp, "The '%s' block driver requires a file name",
1759                    drv->format_name);
1760         ret = -EINVAL;
1761         goto fail_opts;
1762     }
1763 
1764     trace_bdrv_open_common(bs, filename ?: "", bs->open_flags,
1765                            drv->format_name);
1766 
1767     ro = bdrv_is_read_only(bs);
1768 
1769     if (use_bdrv_whitelist && !bdrv_is_whitelisted(drv, ro)) {
1770         if (!ro && bdrv_is_whitelisted(drv, true)) {
1771             ret = bdrv_apply_auto_read_only(bs, NULL, NULL);
1772         } else {
1773             ret = -ENOTSUP;
1774         }
1775         if (ret < 0) {
1776             error_setg(errp,
1777                        !ro && bdrv_is_whitelisted(drv, true)
1778                        ? "Driver '%s' can only be used for read-only devices"
1779                        : "Driver '%s' is not whitelisted",
1780                        drv->format_name);
1781             goto fail_opts;
1782         }
1783     }
1784 
1785     /* bdrv_new() and bdrv_close() make it so */
1786     assert(qatomic_read(&bs->copy_on_read) == 0);
1787 
1788     if (bs->open_flags & BDRV_O_COPY_ON_READ) {
1789         if (!ro) {
1790             bdrv_enable_copy_on_read(bs);
1791         } else {
1792             error_setg(errp, "Can't use copy-on-read on read-only device");
1793             ret = -EINVAL;
1794             goto fail_opts;
1795         }
1796     }
1797 
1798     discard = qemu_opt_get(opts, BDRV_OPT_DISCARD);
1799     if (discard != NULL) {
1800         if (bdrv_parse_discard_flags(discard, &bs->open_flags) != 0) {
1801             error_setg(errp, "Invalid discard option");
1802             ret = -EINVAL;
1803             goto fail_opts;
1804         }
1805     }
1806 
1807     bs->detect_zeroes =
1808         bdrv_parse_detect_zeroes(opts, bs->open_flags, &local_err);
1809     if (local_err) {
1810         error_propagate(errp, local_err);
1811         ret = -EINVAL;
1812         goto fail_opts;
1813     }
1814 
1815     if (filename != NULL) {
1816         pstrcpy(bs->filename, sizeof(bs->filename), filename);
1817     } else {
1818         bs->filename[0] = '\0';
1819     }
1820     pstrcpy(bs->exact_filename, sizeof(bs->exact_filename), bs->filename);
1821 
1822     /* Open the image, either directly or using a protocol */
1823     open_flags = bdrv_open_flags(bs, bs->open_flags);
1824     node_name = qemu_opt_get(opts, "node-name");
1825 
1826     assert(!drv->bdrv_file_open || file == NULL);
1827     ret = bdrv_open_driver(bs, drv, node_name, options, open_flags, errp);
1828     if (ret < 0) {
1829         goto fail_opts;
1830     }
1831 
1832     qemu_opts_del(opts);
1833     return 0;
1834 
1835 fail_opts:
1836     qemu_opts_del(opts);
1837     return ret;
1838 }
1839 
1840 static QDict *parse_json_filename(const char *filename, Error **errp)
1841 {
1842     QObject *options_obj;
1843     QDict *options;
1844     int ret;
1845 
1846     ret = strstart(filename, "json:", &filename);
1847     assert(ret);
1848 
1849     options_obj = qobject_from_json(filename, errp);
1850     if (!options_obj) {
1851         error_prepend(errp, "Could not parse the JSON options: ");
1852         return NULL;
1853     }
1854 
1855     options = qobject_to(QDict, options_obj);
1856     if (!options) {
1857         qobject_unref(options_obj);
1858         error_setg(errp, "Invalid JSON object given");
1859         return NULL;
1860     }
1861 
1862     qdict_flatten(options);
1863 
1864     return options;
1865 }
1866 
1867 static void parse_json_protocol(QDict *options, const char **pfilename,
1868                                 Error **errp)
1869 {
1870     QDict *json_options;
1871     Error *local_err = NULL;
1872 
1873     /* Parse json: pseudo-protocol */
1874     if (!*pfilename || !g_str_has_prefix(*pfilename, "json:")) {
1875         return;
1876     }
1877 
1878     json_options = parse_json_filename(*pfilename, &local_err);
1879     if (local_err) {
1880         error_propagate(errp, local_err);
1881         return;
1882     }
1883 
1884     /* Options given in the filename have lower priority than options
1885      * specified directly */
1886     qdict_join(options, json_options, false);
1887     qobject_unref(json_options);
1888     *pfilename = NULL;
1889 }
1890 
1891 /*
1892  * Fills in default options for opening images and converts the legacy
1893  * filename/flags pair to option QDict entries.
1894  * The BDRV_O_PROTOCOL flag in *flags will be set or cleared accordingly if a
1895  * block driver has been specified explicitly.
1896  */
1897 static int bdrv_fill_options(QDict **options, const char *filename,
1898                              int *flags, Error **errp)
1899 {
1900     const char *drvname;
1901     bool protocol = *flags & BDRV_O_PROTOCOL;
1902     bool parse_filename = false;
1903     BlockDriver *drv = NULL;
1904     Error *local_err = NULL;
1905 
1906     /*
1907      * Caution: while qdict_get_try_str() is fine, getting non-string
1908      * types would require more care.  When @options come from
1909      * -blockdev or blockdev_add, its members are typed according to
1910      * the QAPI schema, but when they come from -drive, they're all
1911      * QString.
1912      */
1913     drvname = qdict_get_try_str(*options, "driver");
1914     if (drvname) {
1915         drv = bdrv_find_format(drvname);
1916         if (!drv) {
1917             error_setg(errp, "Unknown driver '%s'", drvname);
1918             return -ENOENT;
1919         }
1920         /* If the user has explicitly specified the driver, this choice should
1921          * override the BDRV_O_PROTOCOL flag */
1922         protocol = drv->bdrv_file_open;
1923     }
1924 
1925     if (protocol) {
1926         *flags |= BDRV_O_PROTOCOL;
1927     } else {
1928         *flags &= ~BDRV_O_PROTOCOL;
1929     }
1930 
1931     /* Translate cache options from flags into options */
1932     update_options_from_flags(*options, *flags);
1933 
1934     /* Fetch the file name from the options QDict if necessary */
1935     if (protocol && filename) {
1936         if (!qdict_haskey(*options, "filename")) {
1937             qdict_put_str(*options, "filename", filename);
1938             parse_filename = true;
1939         } else {
1940             error_setg(errp, "Can't specify 'file' and 'filename' options at "
1941                              "the same time");
1942             return -EINVAL;
1943         }
1944     }
1945 
1946     /* Find the right block driver */
1947     /* See cautionary note on accessing @options above */
1948     filename = qdict_get_try_str(*options, "filename");
1949 
1950     if (!drvname && protocol) {
1951         if (filename) {
1952             drv = bdrv_find_protocol(filename, parse_filename, errp);
1953             if (!drv) {
1954                 return -EINVAL;
1955             }
1956 
1957             drvname = drv->format_name;
1958             qdict_put_str(*options, "driver", drvname);
1959         } else {
1960             error_setg(errp, "Must specify either driver or file");
1961             return -EINVAL;
1962         }
1963     }
1964 
1965     assert(drv || !protocol);
1966 
1967     /* Driver-specific filename parsing */
1968     if (drv && drv->bdrv_parse_filename && parse_filename) {
1969         drv->bdrv_parse_filename(filename, *options, &local_err);
1970         if (local_err) {
1971             error_propagate(errp, local_err);
1972             return -EINVAL;
1973         }
1974 
1975         if (!drv->bdrv_needs_filename) {
1976             qdict_del(*options, "filename");
1977         }
1978     }
1979 
1980     return 0;
1981 }
1982 
1983 typedef struct BlockReopenQueueEntry {
1984      bool prepared;
1985      bool perms_checked;
1986      BDRVReopenState state;
1987      QTAILQ_ENTRY(BlockReopenQueueEntry) entry;
1988 } BlockReopenQueueEntry;
1989 
1990 /*
1991  * Return the flags that @bs will have after the reopens in @q have
1992  * successfully completed. If @q is NULL (or @bs is not contained in @q),
1993  * return the current flags.
1994  */
1995 static int bdrv_reopen_get_flags(BlockReopenQueue *q, BlockDriverState *bs)
1996 {
1997     BlockReopenQueueEntry *entry;
1998 
1999     if (q != NULL) {
2000         QTAILQ_FOREACH(entry, q, entry) {
2001             if (entry->state.bs == bs) {
2002                 return entry->state.flags;
2003             }
2004         }
2005     }
2006 
2007     return bs->open_flags;
2008 }
2009 
2010 /* Returns whether the image file can be written to after the reopen queue @q
2011  * has been successfully applied, or right now if @q is NULL. */
2012 static bool bdrv_is_writable_after_reopen(BlockDriverState *bs,
2013                                           BlockReopenQueue *q)
2014 {
2015     int flags = bdrv_reopen_get_flags(q, bs);
2016 
2017     return (flags & (BDRV_O_RDWR | BDRV_O_INACTIVE)) == BDRV_O_RDWR;
2018 }
2019 
2020 /*
2021  * Return whether the BDS can be written to.  This is not necessarily
2022  * the same as !bdrv_is_read_only(bs), as inactivated images may not
2023  * be written to but do not count as read-only images.
2024  */
2025 bool bdrv_is_writable(BlockDriverState *bs)
2026 {
2027     return bdrv_is_writable_after_reopen(bs, NULL);
2028 }
2029 
2030 static char *bdrv_child_user_desc(BdrvChild *c)
2031 {
2032     return c->klass->get_parent_desc(c);
2033 }
2034 
2035 /*
2036  * Check that @a allows everything that @b needs. @a and @b must reference same
2037  * child node.
2038  */
2039 static bool bdrv_a_allow_b(BdrvChild *a, BdrvChild *b, Error **errp)
2040 {
2041     const char *child_bs_name;
2042     g_autofree char *a_user = NULL;
2043     g_autofree char *b_user = NULL;
2044     g_autofree char *perms = NULL;
2045 
2046     assert(a->bs);
2047     assert(a->bs == b->bs);
2048 
2049     if ((b->perm & a->shared_perm) == b->perm) {
2050         return true;
2051     }
2052 
2053     child_bs_name = bdrv_get_node_name(b->bs);
2054     a_user = bdrv_child_user_desc(a);
2055     b_user = bdrv_child_user_desc(b);
2056     perms = bdrv_perm_names(b->perm & ~a->shared_perm);
2057 
2058     error_setg(errp, "Permission conflict on node '%s': permissions '%s' are "
2059                "both required by %s (uses node '%s' as '%s' child) and "
2060                "unshared by %s (uses node '%s' as '%s' child).",
2061                child_bs_name, perms,
2062                b_user, child_bs_name, b->name,
2063                a_user, child_bs_name, a->name);
2064 
2065     return false;
2066 }
2067 
2068 static bool bdrv_parent_perms_conflict(BlockDriverState *bs, Error **errp)
2069 {
2070     BdrvChild *a, *b;
2071 
2072     /*
2073      * During the loop we'll look at each pair twice. That's correct because
2074      * bdrv_a_allow_b() is asymmetric and we should check each pair in both
2075      * directions.
2076      */
2077     QLIST_FOREACH(a, &bs->parents, next_parent) {
2078         QLIST_FOREACH(b, &bs->parents, next_parent) {
2079             if (a == b) {
2080                 continue;
2081             }
2082 
2083             if (!bdrv_a_allow_b(a, b, errp)) {
2084                 return true;
2085             }
2086         }
2087     }
2088 
2089     return false;
2090 }
2091 
2092 static void bdrv_child_perm(BlockDriverState *bs, BlockDriverState *child_bs,
2093                             BdrvChild *c, BdrvChildRole role,
2094                             BlockReopenQueue *reopen_queue,
2095                             uint64_t parent_perm, uint64_t parent_shared,
2096                             uint64_t *nperm, uint64_t *nshared)
2097 {
2098     assert(bs->drv && bs->drv->bdrv_child_perm);
2099     bs->drv->bdrv_child_perm(bs, c, role, reopen_queue,
2100                              parent_perm, parent_shared,
2101                              nperm, nshared);
2102     /* TODO Take force_share from reopen_queue */
2103     if (child_bs && child_bs->force_share) {
2104         *nshared = BLK_PERM_ALL;
2105     }
2106 }
2107 
2108 /*
2109  * Adds the whole subtree of @bs (including @bs itself) to the @list (except for
2110  * nodes that are already in the @list, of course) so that final list is
2111  * topologically sorted. Return the result (GSList @list object is updated, so
2112  * don't use old reference after function call).
2113  *
2114  * On function start @list must be already topologically sorted and for any node
2115  * in the @list the whole subtree of the node must be in the @list as well. The
2116  * simplest way to satisfy this criteria: use only result of
2117  * bdrv_topological_dfs() or NULL as @list parameter.
2118  */
2119 static GSList *bdrv_topological_dfs(GSList *list, GHashTable *found,
2120                                     BlockDriverState *bs)
2121 {
2122     BdrvChild *child;
2123     g_autoptr(GHashTable) local_found = NULL;
2124 
2125     if (!found) {
2126         assert(!list);
2127         found = local_found = g_hash_table_new(NULL, NULL);
2128     }
2129 
2130     if (g_hash_table_contains(found, bs)) {
2131         return list;
2132     }
2133     g_hash_table_add(found, bs);
2134 
2135     QLIST_FOREACH(child, &bs->children, next) {
2136         list = bdrv_topological_dfs(list, found, child->bs);
2137     }
2138 
2139     return g_slist_prepend(list, bs);
2140 }
2141 
2142 typedef struct BdrvChildSetPermState {
2143     BdrvChild *child;
2144     uint64_t old_perm;
2145     uint64_t old_shared_perm;
2146 } BdrvChildSetPermState;
2147 
2148 static void bdrv_child_set_perm_abort(void *opaque)
2149 {
2150     BdrvChildSetPermState *s = opaque;
2151 
2152     s->child->perm = s->old_perm;
2153     s->child->shared_perm = s->old_shared_perm;
2154 }
2155 
2156 static TransactionActionDrv bdrv_child_set_pem_drv = {
2157     .abort = bdrv_child_set_perm_abort,
2158     .clean = g_free,
2159 };
2160 
2161 static void bdrv_child_set_perm(BdrvChild *c, uint64_t perm,
2162                                 uint64_t shared, Transaction *tran)
2163 {
2164     BdrvChildSetPermState *s = g_new(BdrvChildSetPermState, 1);
2165 
2166     *s = (BdrvChildSetPermState) {
2167         .child = c,
2168         .old_perm = c->perm,
2169         .old_shared_perm = c->shared_perm,
2170     };
2171 
2172     c->perm = perm;
2173     c->shared_perm = shared;
2174 
2175     tran_add(tran, &bdrv_child_set_pem_drv, s);
2176 }
2177 
2178 static void bdrv_drv_set_perm_commit(void *opaque)
2179 {
2180     BlockDriverState *bs = opaque;
2181     uint64_t cumulative_perms, cumulative_shared_perms;
2182 
2183     if (bs->drv->bdrv_set_perm) {
2184         bdrv_get_cumulative_perm(bs, &cumulative_perms,
2185                                  &cumulative_shared_perms);
2186         bs->drv->bdrv_set_perm(bs, cumulative_perms, cumulative_shared_perms);
2187     }
2188 }
2189 
2190 static void bdrv_drv_set_perm_abort(void *opaque)
2191 {
2192     BlockDriverState *bs = opaque;
2193 
2194     if (bs->drv->bdrv_abort_perm_update) {
2195         bs->drv->bdrv_abort_perm_update(bs);
2196     }
2197 }
2198 
2199 TransactionActionDrv bdrv_drv_set_perm_drv = {
2200     .abort = bdrv_drv_set_perm_abort,
2201     .commit = bdrv_drv_set_perm_commit,
2202 };
2203 
2204 static int bdrv_drv_set_perm(BlockDriverState *bs, uint64_t perm,
2205                              uint64_t shared_perm, Transaction *tran,
2206                              Error **errp)
2207 {
2208     if (!bs->drv) {
2209         return 0;
2210     }
2211 
2212     if (bs->drv->bdrv_check_perm) {
2213         int ret = bs->drv->bdrv_check_perm(bs, perm, shared_perm, errp);
2214         if (ret < 0) {
2215             return ret;
2216         }
2217     }
2218 
2219     if (tran) {
2220         tran_add(tran, &bdrv_drv_set_perm_drv, bs);
2221     }
2222 
2223     return 0;
2224 }
2225 
2226 typedef struct BdrvReplaceChildState {
2227     BdrvChild *child;
2228     BlockDriverState *old_bs;
2229 } BdrvReplaceChildState;
2230 
2231 static void bdrv_replace_child_commit(void *opaque)
2232 {
2233     BdrvReplaceChildState *s = opaque;
2234 
2235     bdrv_unref(s->old_bs);
2236 }
2237 
2238 static void bdrv_replace_child_abort(void *opaque)
2239 {
2240     BdrvReplaceChildState *s = opaque;
2241     BlockDriverState *new_bs = s->child->bs;
2242 
2243     /* old_bs reference is transparently moved from @s to @s->child */
2244     bdrv_replace_child_noperm(s->child, s->old_bs);
2245     bdrv_unref(new_bs);
2246 }
2247 
2248 static TransactionActionDrv bdrv_replace_child_drv = {
2249     .commit = bdrv_replace_child_commit,
2250     .abort = bdrv_replace_child_abort,
2251     .clean = g_free,
2252 };
2253 
2254 /*
2255  * bdrv_replace_child_tran
2256  *
2257  * Note: real unref of old_bs is done only on commit.
2258  *
2259  * The function doesn't update permissions, caller is responsible for this.
2260  */
2261 static void bdrv_replace_child_tran(BdrvChild *child, BlockDriverState *new_bs,
2262                                     Transaction *tran)
2263 {
2264     BdrvReplaceChildState *s = g_new(BdrvReplaceChildState, 1);
2265     *s = (BdrvReplaceChildState) {
2266         .child = child,
2267         .old_bs = child->bs,
2268     };
2269     tran_add(tran, &bdrv_replace_child_drv, s);
2270 
2271     if (new_bs) {
2272         bdrv_ref(new_bs);
2273     }
2274     bdrv_replace_child_noperm(child, new_bs);
2275     /* old_bs reference is transparently moved from @child to @s */
2276 }
2277 
2278 /*
2279  * Refresh permissions in @bs subtree. The function is intended to be called
2280  * after some graph modification that was done without permission update.
2281  */
2282 static int bdrv_node_refresh_perm(BlockDriverState *bs, BlockReopenQueue *q,
2283                                   Transaction *tran, Error **errp)
2284 {
2285     BlockDriver *drv = bs->drv;
2286     BdrvChild *c;
2287     int ret;
2288     uint64_t cumulative_perms, cumulative_shared_perms;
2289 
2290     bdrv_get_cumulative_perm(bs, &cumulative_perms, &cumulative_shared_perms);
2291 
2292     /* Write permissions never work with read-only images */
2293     if ((cumulative_perms & (BLK_PERM_WRITE | BLK_PERM_WRITE_UNCHANGED)) &&
2294         !bdrv_is_writable_after_reopen(bs, q))
2295     {
2296         if (!bdrv_is_writable_after_reopen(bs, NULL)) {
2297             error_setg(errp, "Block node is read-only");
2298         } else {
2299             error_setg(errp, "Read-only block node '%s' cannot support "
2300                        "read-write users", bdrv_get_node_name(bs));
2301         }
2302 
2303         return -EPERM;
2304     }
2305 
2306     /*
2307      * Unaligned requests will automatically be aligned to bl.request_alignment
2308      * and without RESIZE we can't extend requests to write to space beyond the
2309      * end of the image, so it's required that the image size is aligned.
2310      */
2311     if ((cumulative_perms & (BLK_PERM_WRITE | BLK_PERM_WRITE_UNCHANGED)) &&
2312         !(cumulative_perms & BLK_PERM_RESIZE))
2313     {
2314         if ((bs->total_sectors * BDRV_SECTOR_SIZE) % bs->bl.request_alignment) {
2315             error_setg(errp, "Cannot get 'write' permission without 'resize': "
2316                              "Image size is not a multiple of request "
2317                              "alignment");
2318             return -EPERM;
2319         }
2320     }
2321 
2322     /* Check this node */
2323     if (!drv) {
2324         return 0;
2325     }
2326 
2327     ret = bdrv_drv_set_perm(bs, cumulative_perms, cumulative_shared_perms, tran,
2328                             errp);
2329     if (ret < 0) {
2330         return ret;
2331     }
2332 
2333     /* Drivers that never have children can omit .bdrv_child_perm() */
2334     if (!drv->bdrv_child_perm) {
2335         assert(QLIST_EMPTY(&bs->children));
2336         return 0;
2337     }
2338 
2339     /* Check all children */
2340     QLIST_FOREACH(c, &bs->children, next) {
2341         uint64_t cur_perm, cur_shared;
2342 
2343         bdrv_child_perm(bs, c->bs, c, c->role, q,
2344                         cumulative_perms, cumulative_shared_perms,
2345                         &cur_perm, &cur_shared);
2346         bdrv_child_set_perm(c, cur_perm, cur_shared, tran);
2347     }
2348 
2349     return 0;
2350 }
2351 
2352 static int bdrv_list_refresh_perms(GSList *list, BlockReopenQueue *q,
2353                                    Transaction *tran, Error **errp)
2354 {
2355     int ret;
2356     BlockDriverState *bs;
2357 
2358     for ( ; list; list = list->next) {
2359         bs = list->data;
2360 
2361         if (bdrv_parent_perms_conflict(bs, errp)) {
2362             return -EINVAL;
2363         }
2364 
2365         ret = bdrv_node_refresh_perm(bs, q, tran, errp);
2366         if (ret < 0) {
2367             return ret;
2368         }
2369     }
2370 
2371     return 0;
2372 }
2373 
2374 void bdrv_get_cumulative_perm(BlockDriverState *bs, uint64_t *perm,
2375                               uint64_t *shared_perm)
2376 {
2377     BdrvChild *c;
2378     uint64_t cumulative_perms = 0;
2379     uint64_t cumulative_shared_perms = BLK_PERM_ALL;
2380 
2381     QLIST_FOREACH(c, &bs->parents, next_parent) {
2382         cumulative_perms |= c->perm;
2383         cumulative_shared_perms &= c->shared_perm;
2384     }
2385 
2386     *perm = cumulative_perms;
2387     *shared_perm = cumulative_shared_perms;
2388 }
2389 
2390 char *bdrv_perm_names(uint64_t perm)
2391 {
2392     struct perm_name {
2393         uint64_t perm;
2394         const char *name;
2395     } permissions[] = {
2396         { BLK_PERM_CONSISTENT_READ, "consistent read" },
2397         { BLK_PERM_WRITE,           "write" },
2398         { BLK_PERM_WRITE_UNCHANGED, "write unchanged" },
2399         { BLK_PERM_RESIZE,          "resize" },
2400         { BLK_PERM_GRAPH_MOD,       "change children" },
2401         { 0, NULL }
2402     };
2403 
2404     GString *result = g_string_sized_new(30);
2405     struct perm_name *p;
2406 
2407     for (p = permissions; p->name; p++) {
2408         if (perm & p->perm) {
2409             if (result->len > 0) {
2410                 g_string_append(result, ", ");
2411             }
2412             g_string_append(result, p->name);
2413         }
2414     }
2415 
2416     return g_string_free(result, FALSE);
2417 }
2418 
2419 
2420 static int bdrv_refresh_perms(BlockDriverState *bs, Error **errp)
2421 {
2422     int ret;
2423     Transaction *tran = tran_new();
2424     g_autoptr(GSList) list = bdrv_topological_dfs(NULL, NULL, bs);
2425 
2426     ret = bdrv_list_refresh_perms(list, NULL, tran, errp);
2427     tran_finalize(tran, ret);
2428 
2429     return ret;
2430 }
2431 
2432 int bdrv_child_try_set_perm(BdrvChild *c, uint64_t perm, uint64_t shared,
2433                             Error **errp)
2434 {
2435     Error *local_err = NULL;
2436     Transaction *tran = tran_new();
2437     int ret;
2438 
2439     bdrv_child_set_perm(c, perm, shared, tran);
2440 
2441     ret = bdrv_refresh_perms(c->bs, &local_err);
2442 
2443     tran_finalize(tran, ret);
2444 
2445     if (ret < 0) {
2446         if ((perm & ~c->perm) || (c->shared_perm & ~shared)) {
2447             /* tighten permissions */
2448             error_propagate(errp, local_err);
2449         } else {
2450             /*
2451              * Our caller may intend to only loosen restrictions and
2452              * does not expect this function to fail.  Errors are not
2453              * fatal in such a case, so we can just hide them from our
2454              * caller.
2455              */
2456             error_free(local_err);
2457             ret = 0;
2458         }
2459     }
2460 
2461     return ret;
2462 }
2463 
2464 int bdrv_child_refresh_perms(BlockDriverState *bs, BdrvChild *c, Error **errp)
2465 {
2466     uint64_t parent_perms, parent_shared;
2467     uint64_t perms, shared;
2468 
2469     bdrv_get_cumulative_perm(bs, &parent_perms, &parent_shared);
2470     bdrv_child_perm(bs, c->bs, c, c->role, NULL,
2471                     parent_perms, parent_shared, &perms, &shared);
2472 
2473     return bdrv_child_try_set_perm(c, perms, shared, errp);
2474 }
2475 
2476 /*
2477  * Default implementation for .bdrv_child_perm() for block filters:
2478  * Forward CONSISTENT_READ, WRITE, WRITE_UNCHANGED, and RESIZE to the
2479  * filtered child.
2480  */
2481 static void bdrv_filter_default_perms(BlockDriverState *bs, BdrvChild *c,
2482                                       BdrvChildRole role,
2483                                       BlockReopenQueue *reopen_queue,
2484                                       uint64_t perm, uint64_t shared,
2485                                       uint64_t *nperm, uint64_t *nshared)
2486 {
2487     *nperm = perm & DEFAULT_PERM_PASSTHROUGH;
2488     *nshared = (shared & DEFAULT_PERM_PASSTHROUGH) | DEFAULT_PERM_UNCHANGED;
2489 }
2490 
2491 static void bdrv_default_perms_for_cow(BlockDriverState *bs, BdrvChild *c,
2492                                        BdrvChildRole role,
2493                                        BlockReopenQueue *reopen_queue,
2494                                        uint64_t perm, uint64_t shared,
2495                                        uint64_t *nperm, uint64_t *nshared)
2496 {
2497     assert(role & BDRV_CHILD_COW);
2498 
2499     /*
2500      * We want consistent read from backing files if the parent needs it.
2501      * No other operations are performed on backing files.
2502      */
2503     perm &= BLK_PERM_CONSISTENT_READ;
2504 
2505     /*
2506      * If the parent can deal with changing data, we're okay with a
2507      * writable and resizable backing file.
2508      * TODO Require !(perm & BLK_PERM_CONSISTENT_READ), too?
2509      */
2510     if (shared & BLK_PERM_WRITE) {
2511         shared = BLK_PERM_WRITE | BLK_PERM_RESIZE;
2512     } else {
2513         shared = 0;
2514     }
2515 
2516     shared |= BLK_PERM_CONSISTENT_READ | BLK_PERM_GRAPH_MOD |
2517               BLK_PERM_WRITE_UNCHANGED;
2518 
2519     if (bs->open_flags & BDRV_O_INACTIVE) {
2520         shared |= BLK_PERM_WRITE | BLK_PERM_RESIZE;
2521     }
2522 
2523     *nperm = perm;
2524     *nshared = shared;
2525 }
2526 
2527 static void bdrv_default_perms_for_storage(BlockDriverState *bs, BdrvChild *c,
2528                                            BdrvChildRole role,
2529                                            BlockReopenQueue *reopen_queue,
2530                                            uint64_t perm, uint64_t shared,
2531                                            uint64_t *nperm, uint64_t *nshared)
2532 {
2533     int flags;
2534 
2535     assert(role & (BDRV_CHILD_METADATA | BDRV_CHILD_DATA));
2536 
2537     flags = bdrv_reopen_get_flags(reopen_queue, bs);
2538 
2539     /*
2540      * Apart from the modifications below, the same permissions are
2541      * forwarded and left alone as for filters
2542      */
2543     bdrv_filter_default_perms(bs, c, role, reopen_queue,
2544                               perm, shared, &perm, &shared);
2545 
2546     if (role & BDRV_CHILD_METADATA) {
2547         /* Format drivers may touch metadata even if the guest doesn't write */
2548         if (bdrv_is_writable_after_reopen(bs, reopen_queue)) {
2549             perm |= BLK_PERM_WRITE | BLK_PERM_RESIZE;
2550         }
2551 
2552         /*
2553          * bs->file always needs to be consistent because of the
2554          * metadata. We can never allow other users to resize or write
2555          * to it.
2556          */
2557         if (!(flags & BDRV_O_NO_IO)) {
2558             perm |= BLK_PERM_CONSISTENT_READ;
2559         }
2560         shared &= ~(BLK_PERM_WRITE | BLK_PERM_RESIZE);
2561     }
2562 
2563     if (role & BDRV_CHILD_DATA) {
2564         /*
2565          * Technically, everything in this block is a subset of the
2566          * BDRV_CHILD_METADATA path taken above, and so this could
2567          * be an "else if" branch.  However, that is not obvious, and
2568          * this function is not performance critical, therefore we let
2569          * this be an independent "if".
2570          */
2571 
2572         /*
2573          * We cannot allow other users to resize the file because the
2574          * format driver might have some assumptions about the size
2575          * (e.g. because it is stored in metadata, or because the file
2576          * is split into fixed-size data files).
2577          */
2578         shared &= ~BLK_PERM_RESIZE;
2579 
2580         /*
2581          * WRITE_UNCHANGED often cannot be performed as such on the
2582          * data file.  For example, the qcow2 driver may still need to
2583          * write copied clusters on copy-on-read.
2584          */
2585         if (perm & BLK_PERM_WRITE_UNCHANGED) {
2586             perm |= BLK_PERM_WRITE;
2587         }
2588 
2589         /*
2590          * If the data file is written to, the format driver may
2591          * expect to be able to resize it by writing beyond the EOF.
2592          */
2593         if (perm & BLK_PERM_WRITE) {
2594             perm |= BLK_PERM_RESIZE;
2595         }
2596     }
2597 
2598     if (bs->open_flags & BDRV_O_INACTIVE) {
2599         shared |= BLK_PERM_WRITE | BLK_PERM_RESIZE;
2600     }
2601 
2602     *nperm = perm;
2603     *nshared = shared;
2604 }
2605 
2606 void bdrv_default_perms(BlockDriverState *bs, BdrvChild *c,
2607                         BdrvChildRole role, BlockReopenQueue *reopen_queue,
2608                         uint64_t perm, uint64_t shared,
2609                         uint64_t *nperm, uint64_t *nshared)
2610 {
2611     if (role & BDRV_CHILD_FILTERED) {
2612         assert(!(role & (BDRV_CHILD_DATA | BDRV_CHILD_METADATA |
2613                          BDRV_CHILD_COW)));
2614         bdrv_filter_default_perms(bs, c, role, reopen_queue,
2615                                   perm, shared, nperm, nshared);
2616     } else if (role & BDRV_CHILD_COW) {
2617         assert(!(role & (BDRV_CHILD_DATA | BDRV_CHILD_METADATA)));
2618         bdrv_default_perms_for_cow(bs, c, role, reopen_queue,
2619                                    perm, shared, nperm, nshared);
2620     } else if (role & (BDRV_CHILD_METADATA | BDRV_CHILD_DATA)) {
2621         bdrv_default_perms_for_storage(bs, c, role, reopen_queue,
2622                                        perm, shared, nperm, nshared);
2623     } else {
2624         g_assert_not_reached();
2625     }
2626 }
2627 
2628 uint64_t bdrv_qapi_perm_to_blk_perm(BlockPermission qapi_perm)
2629 {
2630     static const uint64_t permissions[] = {
2631         [BLOCK_PERMISSION_CONSISTENT_READ]  = BLK_PERM_CONSISTENT_READ,
2632         [BLOCK_PERMISSION_WRITE]            = BLK_PERM_WRITE,
2633         [BLOCK_PERMISSION_WRITE_UNCHANGED]  = BLK_PERM_WRITE_UNCHANGED,
2634         [BLOCK_PERMISSION_RESIZE]           = BLK_PERM_RESIZE,
2635         [BLOCK_PERMISSION_GRAPH_MOD]        = BLK_PERM_GRAPH_MOD,
2636     };
2637 
2638     QEMU_BUILD_BUG_ON(ARRAY_SIZE(permissions) != BLOCK_PERMISSION__MAX);
2639     QEMU_BUILD_BUG_ON(1UL << ARRAY_SIZE(permissions) != BLK_PERM_ALL + 1);
2640 
2641     assert(qapi_perm < BLOCK_PERMISSION__MAX);
2642 
2643     return permissions[qapi_perm];
2644 }
2645 
2646 static void bdrv_replace_child_noperm(BdrvChild *child,
2647                                       BlockDriverState *new_bs)
2648 {
2649     BlockDriverState *old_bs = child->bs;
2650     int new_bs_quiesce_counter;
2651     int drain_saldo;
2652 
2653     assert(!child->frozen);
2654 
2655     if (old_bs && new_bs) {
2656         assert(bdrv_get_aio_context(old_bs) == bdrv_get_aio_context(new_bs));
2657     }
2658 
2659     new_bs_quiesce_counter = (new_bs ? new_bs->quiesce_counter : 0);
2660     drain_saldo = new_bs_quiesce_counter - child->parent_quiesce_counter;
2661 
2662     /*
2663      * If the new child node is drained but the old one was not, flush
2664      * all outstanding requests to the old child node.
2665      */
2666     while (drain_saldo > 0 && child->klass->drained_begin) {
2667         bdrv_parent_drained_begin_single(child, true);
2668         drain_saldo--;
2669     }
2670 
2671     if (old_bs) {
2672         /* Detach first so that the recursive drain sections coming from @child
2673          * are already gone and we only end the drain sections that came from
2674          * elsewhere. */
2675         if (child->klass->detach) {
2676             child->klass->detach(child);
2677         }
2678         QLIST_REMOVE(child, next_parent);
2679     }
2680 
2681     child->bs = new_bs;
2682 
2683     if (new_bs) {
2684         QLIST_INSERT_HEAD(&new_bs->parents, child, next_parent);
2685 
2686         /*
2687          * Detaching the old node may have led to the new node's
2688          * quiesce_counter having been decreased.  Not a problem, we
2689          * just need to recognize this here and then invoke
2690          * drained_end appropriately more often.
2691          */
2692         assert(new_bs->quiesce_counter <= new_bs_quiesce_counter);
2693         drain_saldo += new_bs->quiesce_counter - new_bs_quiesce_counter;
2694 
2695         /* Attach only after starting new drained sections, so that recursive
2696          * drain sections coming from @child don't get an extra .drained_begin
2697          * callback. */
2698         if (child->klass->attach) {
2699             child->klass->attach(child);
2700         }
2701     }
2702 
2703     /*
2704      * If the old child node was drained but the new one is not, allow
2705      * requests to come in only after the new node has been attached.
2706      */
2707     while (drain_saldo < 0 && child->klass->drained_end) {
2708         bdrv_parent_drained_end_single(child);
2709         drain_saldo++;
2710     }
2711 }
2712 
2713 static void bdrv_child_free(void *opaque)
2714 {
2715     BdrvChild *c = opaque;
2716 
2717     g_free(c->name);
2718     g_free(c);
2719 }
2720 
2721 static void bdrv_remove_empty_child(BdrvChild *child)
2722 {
2723     assert(!child->bs);
2724     QLIST_SAFE_REMOVE(child, next);
2725     bdrv_child_free(child);
2726 }
2727 
2728 typedef struct BdrvAttachChildCommonState {
2729     BdrvChild **child;
2730     AioContext *old_parent_ctx;
2731     AioContext *old_child_ctx;
2732 } BdrvAttachChildCommonState;
2733 
2734 static void bdrv_attach_child_common_abort(void *opaque)
2735 {
2736     BdrvAttachChildCommonState *s = opaque;
2737     BdrvChild *child = *s->child;
2738     BlockDriverState *bs = child->bs;
2739 
2740     bdrv_replace_child_noperm(child, NULL);
2741 
2742     if (bdrv_get_aio_context(bs) != s->old_child_ctx) {
2743         bdrv_try_set_aio_context(bs, s->old_child_ctx, &error_abort);
2744     }
2745 
2746     if (bdrv_child_get_parent_aio_context(child) != s->old_parent_ctx) {
2747         GSList *ignore = g_slist_prepend(NULL, child);
2748 
2749         child->klass->can_set_aio_ctx(child, s->old_parent_ctx, &ignore,
2750                                       &error_abort);
2751         g_slist_free(ignore);
2752         ignore = g_slist_prepend(NULL, child);
2753         child->klass->set_aio_ctx(child, s->old_parent_ctx, &ignore);
2754 
2755         g_slist_free(ignore);
2756     }
2757 
2758     bdrv_unref(bs);
2759     bdrv_remove_empty_child(child);
2760     *s->child = NULL;
2761 }
2762 
2763 static TransactionActionDrv bdrv_attach_child_common_drv = {
2764     .abort = bdrv_attach_child_common_abort,
2765     .clean = g_free,
2766 };
2767 
2768 /*
2769  * Common part of attaching bdrv child to bs or to blk or to job
2770  *
2771  * Resulting new child is returned through @child.
2772  * At start *@child must be NULL.
2773  * @child is saved to a new entry of @tran, so that *@child could be reverted to
2774  * NULL on abort(). So referenced variable must live at least until transaction
2775  * end.
2776  *
2777  * Function doesn't update permissions, caller is responsible for this.
2778  */
2779 static int bdrv_attach_child_common(BlockDriverState *child_bs,
2780                                     const char *child_name,
2781                                     const BdrvChildClass *child_class,
2782                                     BdrvChildRole child_role,
2783                                     uint64_t perm, uint64_t shared_perm,
2784                                     void *opaque, BdrvChild **child,
2785                                     Transaction *tran, Error **errp)
2786 {
2787     BdrvChild *new_child;
2788     AioContext *parent_ctx;
2789     AioContext *child_ctx = bdrv_get_aio_context(child_bs);
2790 
2791     assert(child);
2792     assert(*child == NULL);
2793     assert(child_class->get_parent_desc);
2794 
2795     new_child = g_new(BdrvChild, 1);
2796     *new_child = (BdrvChild) {
2797         .bs             = NULL,
2798         .name           = g_strdup(child_name),
2799         .klass          = child_class,
2800         .role           = child_role,
2801         .perm           = perm,
2802         .shared_perm    = shared_perm,
2803         .opaque         = opaque,
2804     };
2805 
2806     /*
2807      * If the AioContexts don't match, first try to move the subtree of
2808      * child_bs into the AioContext of the new parent. If this doesn't work,
2809      * try moving the parent into the AioContext of child_bs instead.
2810      */
2811     parent_ctx = bdrv_child_get_parent_aio_context(new_child);
2812     if (child_ctx != parent_ctx) {
2813         Error *local_err = NULL;
2814         int ret = bdrv_try_set_aio_context(child_bs, parent_ctx, &local_err);
2815 
2816         if (ret < 0 && child_class->can_set_aio_ctx) {
2817             GSList *ignore = g_slist_prepend(NULL, new_child);
2818             if (child_class->can_set_aio_ctx(new_child, child_ctx, &ignore,
2819                                              NULL))
2820             {
2821                 error_free(local_err);
2822                 ret = 0;
2823                 g_slist_free(ignore);
2824                 ignore = g_slist_prepend(NULL, new_child);
2825                 child_class->set_aio_ctx(new_child, child_ctx, &ignore);
2826             }
2827             g_slist_free(ignore);
2828         }
2829 
2830         if (ret < 0) {
2831             error_propagate(errp, local_err);
2832             bdrv_remove_empty_child(new_child);
2833             return ret;
2834         }
2835     }
2836 
2837     bdrv_ref(child_bs);
2838     bdrv_replace_child_noperm(new_child, child_bs);
2839 
2840     *child = new_child;
2841 
2842     BdrvAttachChildCommonState *s = g_new(BdrvAttachChildCommonState, 1);
2843     *s = (BdrvAttachChildCommonState) {
2844         .child = child,
2845         .old_parent_ctx = parent_ctx,
2846         .old_child_ctx = child_ctx,
2847     };
2848     tran_add(tran, &bdrv_attach_child_common_drv, s);
2849 
2850     return 0;
2851 }
2852 
2853 /*
2854  * Variable referenced by @child must live at least until transaction end.
2855  * (see bdrv_attach_child_common() doc for details)
2856  *
2857  * Function doesn't update permissions, caller is responsible for this.
2858  */
2859 static int bdrv_attach_child_noperm(BlockDriverState *parent_bs,
2860                                     BlockDriverState *child_bs,
2861                                     const char *child_name,
2862                                     const BdrvChildClass *child_class,
2863                                     BdrvChildRole child_role,
2864                                     BdrvChild **child,
2865                                     Transaction *tran,
2866                                     Error **errp)
2867 {
2868     int ret;
2869     uint64_t perm, shared_perm;
2870 
2871     assert(parent_bs->drv);
2872 
2873     bdrv_get_cumulative_perm(parent_bs, &perm, &shared_perm);
2874     bdrv_child_perm(parent_bs, child_bs, NULL, child_role, NULL,
2875                     perm, shared_perm, &perm, &shared_perm);
2876 
2877     ret = bdrv_attach_child_common(child_bs, child_name, child_class,
2878                                    child_role, perm, shared_perm, parent_bs,
2879                                    child, tran, errp);
2880     if (ret < 0) {
2881         return ret;
2882     }
2883 
2884     QLIST_INSERT_HEAD(&parent_bs->children, *child, next);
2885     /*
2886      * child is removed in bdrv_attach_child_common_abort(), so don't care to
2887      * abort this change separately.
2888      */
2889 
2890     return 0;
2891 }
2892 
2893 static void bdrv_detach_child(BdrvChild *child)
2894 {
2895     BlockDriverState *old_bs = child->bs;
2896 
2897     bdrv_replace_child_noperm(child, NULL);
2898     bdrv_remove_empty_child(child);
2899 
2900     if (old_bs) {
2901         /*
2902          * Update permissions for old node. We're just taking a parent away, so
2903          * we're loosening restrictions. Errors of permission update are not
2904          * fatal in this case, ignore them.
2905          */
2906         bdrv_refresh_perms(old_bs, NULL);
2907 
2908         /*
2909          * When the parent requiring a non-default AioContext is removed, the
2910          * node moves back to the main AioContext
2911          */
2912         bdrv_try_set_aio_context(old_bs, qemu_get_aio_context(), NULL);
2913     }
2914 }
2915 
2916 /*
2917  * This function steals the reference to child_bs from the caller.
2918  * That reference is later dropped by bdrv_root_unref_child().
2919  *
2920  * On failure NULL is returned, errp is set and the reference to
2921  * child_bs is also dropped.
2922  *
2923  * The caller must hold the AioContext lock @child_bs, but not that of @ctx
2924  * (unless @child_bs is already in @ctx).
2925  */
2926 BdrvChild *bdrv_root_attach_child(BlockDriverState *child_bs,
2927                                   const char *child_name,
2928                                   const BdrvChildClass *child_class,
2929                                   BdrvChildRole child_role,
2930                                   uint64_t perm, uint64_t shared_perm,
2931                                   void *opaque, Error **errp)
2932 {
2933     int ret;
2934     BdrvChild *child = NULL;
2935     Transaction *tran = tran_new();
2936 
2937     ret = bdrv_attach_child_common(child_bs, child_name, child_class,
2938                                    child_role, perm, shared_perm, opaque,
2939                                    &child, tran, errp);
2940     if (ret < 0) {
2941         goto out;
2942     }
2943 
2944     ret = bdrv_refresh_perms(child_bs, errp);
2945 
2946 out:
2947     tran_finalize(tran, ret);
2948     /* child is unset on failure by bdrv_attach_child_common_abort() */
2949     assert((ret < 0) == !child);
2950 
2951     bdrv_unref(child_bs);
2952     return child;
2953 }
2954 
2955 /*
2956  * This function transfers the reference to child_bs from the caller
2957  * to parent_bs. That reference is later dropped by parent_bs on
2958  * bdrv_close() or if someone calls bdrv_unref_child().
2959  *
2960  * On failure NULL is returned, errp is set and the reference to
2961  * child_bs is also dropped.
2962  *
2963  * If @parent_bs and @child_bs are in different AioContexts, the caller must
2964  * hold the AioContext lock for @child_bs, but not for @parent_bs.
2965  */
2966 BdrvChild *bdrv_attach_child(BlockDriverState *parent_bs,
2967                              BlockDriverState *child_bs,
2968                              const char *child_name,
2969                              const BdrvChildClass *child_class,
2970                              BdrvChildRole child_role,
2971                              Error **errp)
2972 {
2973     int ret;
2974     BdrvChild *child = NULL;
2975     Transaction *tran = tran_new();
2976 
2977     ret = bdrv_attach_child_noperm(parent_bs, child_bs, child_name, child_class,
2978                                    child_role, &child, tran, errp);
2979     if (ret < 0) {
2980         goto out;
2981     }
2982 
2983     ret = bdrv_refresh_perms(parent_bs, errp);
2984     if (ret < 0) {
2985         goto out;
2986     }
2987 
2988 out:
2989     tran_finalize(tran, ret);
2990     /* child is unset on failure by bdrv_attach_child_common_abort() */
2991     assert((ret < 0) == !child);
2992 
2993     bdrv_unref(child_bs);
2994 
2995     return child;
2996 }
2997 
2998 /* Callers must ensure that child->frozen is false. */
2999 void bdrv_root_unref_child(BdrvChild *child)
3000 {
3001     BlockDriverState *child_bs;
3002 
3003     child_bs = child->bs;
3004     bdrv_detach_child(child);
3005     bdrv_unref(child_bs);
3006 }
3007 
3008 typedef struct BdrvSetInheritsFrom {
3009     BlockDriverState *bs;
3010     BlockDriverState *old_inherits_from;
3011 } BdrvSetInheritsFrom;
3012 
3013 static void bdrv_set_inherits_from_abort(void *opaque)
3014 {
3015     BdrvSetInheritsFrom *s = opaque;
3016 
3017     s->bs->inherits_from = s->old_inherits_from;
3018 }
3019 
3020 static TransactionActionDrv bdrv_set_inherits_from_drv = {
3021     .abort = bdrv_set_inherits_from_abort,
3022     .clean = g_free,
3023 };
3024 
3025 /* @tran is allowed to be NULL. In this case no rollback is possible */
3026 static void bdrv_set_inherits_from(BlockDriverState *bs,
3027                                    BlockDriverState *new_inherits_from,
3028                                    Transaction *tran)
3029 {
3030     if (tran) {
3031         BdrvSetInheritsFrom *s = g_new(BdrvSetInheritsFrom, 1);
3032 
3033         *s = (BdrvSetInheritsFrom) {
3034             .bs = bs,
3035             .old_inherits_from = bs->inherits_from,
3036         };
3037 
3038         tran_add(tran, &bdrv_set_inherits_from_drv, s);
3039     }
3040 
3041     bs->inherits_from = new_inherits_from;
3042 }
3043 
3044 /**
3045  * Clear all inherits_from pointers from children and grandchildren of
3046  * @root that point to @root, where necessary.
3047  * @tran is allowed to be NULL. In this case no rollback is possible
3048  */
3049 static void bdrv_unset_inherits_from(BlockDriverState *root, BdrvChild *child,
3050                                      Transaction *tran)
3051 {
3052     BdrvChild *c;
3053 
3054     if (child->bs->inherits_from == root) {
3055         /*
3056          * Remove inherits_from only when the last reference between root and
3057          * child->bs goes away.
3058          */
3059         QLIST_FOREACH(c, &root->children, next) {
3060             if (c != child && c->bs == child->bs) {
3061                 break;
3062             }
3063         }
3064         if (c == NULL) {
3065             bdrv_set_inherits_from(child->bs, NULL, tran);
3066         }
3067     }
3068 
3069     QLIST_FOREACH(c, &child->bs->children, next) {
3070         bdrv_unset_inherits_from(root, c, tran);
3071     }
3072 }
3073 
3074 /* Callers must ensure that child->frozen is false. */
3075 void bdrv_unref_child(BlockDriverState *parent, BdrvChild *child)
3076 {
3077     if (child == NULL) {
3078         return;
3079     }
3080 
3081     bdrv_unset_inherits_from(parent, child, NULL);
3082     bdrv_root_unref_child(child);
3083 }
3084 
3085 
3086 static void bdrv_parent_cb_change_media(BlockDriverState *bs, bool load)
3087 {
3088     BdrvChild *c;
3089     QLIST_FOREACH(c, &bs->parents, next_parent) {
3090         if (c->klass->change_media) {
3091             c->klass->change_media(c, load);
3092         }
3093     }
3094 }
3095 
3096 /* Return true if you can reach parent going through child->inherits_from
3097  * recursively. If parent or child are NULL, return false */
3098 static bool bdrv_inherits_from_recursive(BlockDriverState *child,
3099                                          BlockDriverState *parent)
3100 {
3101     while (child && child != parent) {
3102         child = child->inherits_from;
3103     }
3104 
3105     return child != NULL;
3106 }
3107 
3108 /*
3109  * Return the BdrvChildRole for @bs's backing child.  bs->backing is
3110  * mostly used for COW backing children (role = COW), but also for
3111  * filtered children (role = FILTERED | PRIMARY).
3112  */
3113 static BdrvChildRole bdrv_backing_role(BlockDriverState *bs)
3114 {
3115     if (bs->drv && bs->drv->is_filter) {
3116         return BDRV_CHILD_FILTERED | BDRV_CHILD_PRIMARY;
3117     } else {
3118         return BDRV_CHILD_COW;
3119     }
3120 }
3121 
3122 /*
3123  * Sets the bs->backing or bs->file link of a BDS. A new reference is created;
3124  * callers which don't need their own reference any more must call bdrv_unref().
3125  *
3126  * Function doesn't update permissions, caller is responsible for this.
3127  */
3128 static int bdrv_set_file_or_backing_noperm(BlockDriverState *parent_bs,
3129                                            BlockDriverState *child_bs,
3130                                            bool is_backing,
3131                                            Transaction *tran, Error **errp)
3132 {
3133     int ret = 0;
3134     bool update_inherits_from =
3135         bdrv_inherits_from_recursive(child_bs, parent_bs);
3136     BdrvChild *child = is_backing ? parent_bs->backing : parent_bs->file;
3137     BdrvChildRole role;
3138 
3139     if (!parent_bs->drv) {
3140         /*
3141          * Node without drv is an object without a class :/. TODO: finally fix
3142          * qcow2 driver to never clear bs->drv and implement format corruption
3143          * handling in other way.
3144          */
3145         error_setg(errp, "Node corrupted");
3146         return -EINVAL;
3147     }
3148 
3149     if (child && child->frozen) {
3150         error_setg(errp, "Cannot change frozen '%s' link from '%s' to '%s'",
3151                    child->name, parent_bs->node_name, child->bs->node_name);
3152         return -EPERM;
3153     }
3154 
3155     if (is_backing && !parent_bs->drv->is_filter &&
3156         !parent_bs->drv->supports_backing)
3157     {
3158         error_setg(errp, "Driver '%s' of node '%s' does not support backing "
3159                    "files", parent_bs->drv->format_name, parent_bs->node_name);
3160         return -EINVAL;
3161     }
3162 
3163     if (parent_bs->drv->is_filter) {
3164         role = BDRV_CHILD_FILTERED | BDRV_CHILD_PRIMARY;
3165     } else if (is_backing) {
3166         role = BDRV_CHILD_COW;
3167     } else {
3168         /*
3169          * We only can use same role as it is in existing child. We don't have
3170          * infrastructure to determine role of file child in generic way
3171          */
3172         if (!child) {
3173             error_setg(errp, "Cannot set file child to format node without "
3174                        "file child");
3175             return -EINVAL;
3176         }
3177         role = child->role;
3178     }
3179 
3180     if (child) {
3181         bdrv_unset_inherits_from(parent_bs, child, tran);
3182         bdrv_remove_file_or_backing_child(parent_bs, child, tran);
3183     }
3184 
3185     if (!child_bs) {
3186         goto out;
3187     }
3188 
3189     ret = bdrv_attach_child_noperm(parent_bs, child_bs,
3190                                    is_backing ? "backing" : "file",
3191                                    &child_of_bds, role,
3192                                    is_backing ? &parent_bs->backing :
3193                                                 &parent_bs->file,
3194                                    tran, errp);
3195     if (ret < 0) {
3196         return ret;
3197     }
3198 
3199 
3200     /*
3201      * If inherits_from pointed recursively to bs then let's update it to
3202      * point directly to bs (else it will become NULL).
3203      */
3204     if (update_inherits_from) {
3205         bdrv_set_inherits_from(child_bs, parent_bs, tran);
3206     }
3207 
3208 out:
3209     bdrv_refresh_limits(parent_bs, tran, NULL);
3210 
3211     return 0;
3212 }
3213 
3214 static int bdrv_set_backing_noperm(BlockDriverState *bs,
3215                                    BlockDriverState *backing_hd,
3216                                    Transaction *tran, Error **errp)
3217 {
3218     return bdrv_set_file_or_backing_noperm(bs, backing_hd, true, tran, errp);
3219 }
3220 
3221 int bdrv_set_backing_hd(BlockDriverState *bs, BlockDriverState *backing_hd,
3222                         Error **errp)
3223 {
3224     int ret;
3225     Transaction *tran = tran_new();
3226 
3227     ret = bdrv_set_backing_noperm(bs, backing_hd, tran, errp);
3228     if (ret < 0) {
3229         goto out;
3230     }
3231 
3232     ret = bdrv_refresh_perms(bs, errp);
3233 out:
3234     tran_finalize(tran, ret);
3235 
3236     return ret;
3237 }
3238 
3239 /*
3240  * Opens the backing file for a BlockDriverState if not yet open
3241  *
3242  * bdref_key specifies the key for the image's BlockdevRef in the options QDict.
3243  * That QDict has to be flattened; therefore, if the BlockdevRef is a QDict
3244  * itself, all options starting with "${bdref_key}." are considered part of the
3245  * BlockdevRef.
3246  *
3247  * TODO Can this be unified with bdrv_open_image()?
3248  */
3249 int bdrv_open_backing_file(BlockDriverState *bs, QDict *parent_options,
3250                            const char *bdref_key, Error **errp)
3251 {
3252     char *backing_filename = NULL;
3253     char *bdref_key_dot;
3254     const char *reference = NULL;
3255     int ret = 0;
3256     bool implicit_backing = false;
3257     BlockDriverState *backing_hd;
3258     QDict *options;
3259     QDict *tmp_parent_options = NULL;
3260     Error *local_err = NULL;
3261 
3262     if (bs->backing != NULL) {
3263         goto free_exit;
3264     }
3265 
3266     /* NULL means an empty set of options */
3267     if (parent_options == NULL) {
3268         tmp_parent_options = qdict_new();
3269         parent_options = tmp_parent_options;
3270     }
3271 
3272     bs->open_flags &= ~BDRV_O_NO_BACKING;
3273 
3274     bdref_key_dot = g_strdup_printf("%s.", bdref_key);
3275     qdict_extract_subqdict(parent_options, &options, bdref_key_dot);
3276     g_free(bdref_key_dot);
3277 
3278     /*
3279      * Caution: while qdict_get_try_str() is fine, getting non-string
3280      * types would require more care.  When @parent_options come from
3281      * -blockdev or blockdev_add, its members are typed according to
3282      * the QAPI schema, but when they come from -drive, they're all
3283      * QString.
3284      */
3285     reference = qdict_get_try_str(parent_options, bdref_key);
3286     if (reference || qdict_haskey(options, "file.filename")) {
3287         /* keep backing_filename NULL */
3288     } else if (bs->backing_file[0] == '\0' && qdict_size(options) == 0) {
3289         qobject_unref(options);
3290         goto free_exit;
3291     } else {
3292         if (qdict_size(options) == 0) {
3293             /* If the user specifies options that do not modify the
3294              * backing file's behavior, we might still consider it the
3295              * implicit backing file.  But it's easier this way, and
3296              * just specifying some of the backing BDS's options is
3297              * only possible with -drive anyway (otherwise the QAPI
3298              * schema forces the user to specify everything). */
3299             implicit_backing = !strcmp(bs->auto_backing_file, bs->backing_file);
3300         }
3301 
3302         backing_filename = bdrv_get_full_backing_filename(bs, &local_err);
3303         if (local_err) {
3304             ret = -EINVAL;
3305             error_propagate(errp, local_err);
3306             qobject_unref(options);
3307             goto free_exit;
3308         }
3309     }
3310 
3311     if (!bs->drv || !bs->drv->supports_backing) {
3312         ret = -EINVAL;
3313         error_setg(errp, "Driver doesn't support backing files");
3314         qobject_unref(options);
3315         goto free_exit;
3316     }
3317 
3318     if (!reference &&
3319         bs->backing_format[0] != '\0' && !qdict_haskey(options, "driver")) {
3320         qdict_put_str(options, "driver", bs->backing_format);
3321     }
3322 
3323     backing_hd = bdrv_open_inherit(backing_filename, reference, options, 0, bs,
3324                                    &child_of_bds, bdrv_backing_role(bs), errp);
3325     if (!backing_hd) {
3326         bs->open_flags |= BDRV_O_NO_BACKING;
3327         error_prepend(errp, "Could not open backing file: ");
3328         ret = -EINVAL;
3329         goto free_exit;
3330     }
3331 
3332     if (implicit_backing) {
3333         bdrv_refresh_filename(backing_hd);
3334         pstrcpy(bs->auto_backing_file, sizeof(bs->auto_backing_file),
3335                 backing_hd->filename);
3336     }
3337 
3338     /* Hook up the backing file link; drop our reference, bs owns the
3339      * backing_hd reference now */
3340     ret = bdrv_set_backing_hd(bs, backing_hd, errp);
3341     bdrv_unref(backing_hd);
3342     if (ret < 0) {
3343         goto free_exit;
3344     }
3345 
3346     qdict_del(parent_options, bdref_key);
3347 
3348 free_exit:
3349     g_free(backing_filename);
3350     qobject_unref(tmp_parent_options);
3351     return ret;
3352 }
3353 
3354 static BlockDriverState *
3355 bdrv_open_child_bs(const char *filename, QDict *options, const char *bdref_key,
3356                    BlockDriverState *parent, const BdrvChildClass *child_class,
3357                    BdrvChildRole child_role, bool allow_none, Error **errp)
3358 {
3359     BlockDriverState *bs = NULL;
3360     QDict *image_options;
3361     char *bdref_key_dot;
3362     const char *reference;
3363 
3364     assert(child_class != NULL);
3365 
3366     bdref_key_dot = g_strdup_printf("%s.", bdref_key);
3367     qdict_extract_subqdict(options, &image_options, bdref_key_dot);
3368     g_free(bdref_key_dot);
3369 
3370     /*
3371      * Caution: while qdict_get_try_str() is fine, getting non-string
3372      * types would require more care.  When @options come from
3373      * -blockdev or blockdev_add, its members are typed according to
3374      * the QAPI schema, but when they come from -drive, they're all
3375      * QString.
3376      */
3377     reference = qdict_get_try_str(options, bdref_key);
3378     if (!filename && !reference && !qdict_size(image_options)) {
3379         if (!allow_none) {
3380             error_setg(errp, "A block device must be specified for \"%s\"",
3381                        bdref_key);
3382         }
3383         qobject_unref(image_options);
3384         goto done;
3385     }
3386 
3387     bs = bdrv_open_inherit(filename, reference, image_options, 0,
3388                            parent, child_class, child_role, errp);
3389     if (!bs) {
3390         goto done;
3391     }
3392 
3393 done:
3394     qdict_del(options, bdref_key);
3395     return bs;
3396 }
3397 
3398 /*
3399  * Opens a disk image whose options are given as BlockdevRef in another block
3400  * device's options.
3401  *
3402  * If allow_none is true, no image will be opened if filename is false and no
3403  * BlockdevRef is given. NULL will be returned, but errp remains unset.
3404  *
3405  * bdrev_key specifies the key for the image's BlockdevRef in the options QDict.
3406  * That QDict has to be flattened; therefore, if the BlockdevRef is a QDict
3407  * itself, all options starting with "${bdref_key}." are considered part of the
3408  * BlockdevRef.
3409  *
3410  * The BlockdevRef will be removed from the options QDict.
3411  */
3412 BdrvChild *bdrv_open_child(const char *filename,
3413                            QDict *options, const char *bdref_key,
3414                            BlockDriverState *parent,
3415                            const BdrvChildClass *child_class,
3416                            BdrvChildRole child_role,
3417                            bool allow_none, Error **errp)
3418 {
3419     BlockDriverState *bs;
3420 
3421     bs = bdrv_open_child_bs(filename, options, bdref_key, parent, child_class,
3422                             child_role, allow_none, errp);
3423     if (bs == NULL) {
3424         return NULL;
3425     }
3426 
3427     return bdrv_attach_child(parent, bs, bdref_key, child_class, child_role,
3428                              errp);
3429 }
3430 
3431 /*
3432  * TODO Future callers may need to specify parent/child_class in order for
3433  * option inheritance to work. Existing callers use it for the root node.
3434  */
3435 BlockDriverState *bdrv_open_blockdev_ref(BlockdevRef *ref, Error **errp)
3436 {
3437     BlockDriverState *bs = NULL;
3438     QObject *obj = NULL;
3439     QDict *qdict = NULL;
3440     const char *reference = NULL;
3441     Visitor *v = NULL;
3442 
3443     if (ref->type == QTYPE_QSTRING) {
3444         reference = ref->u.reference;
3445     } else {
3446         BlockdevOptions *options = &ref->u.definition;
3447         assert(ref->type == QTYPE_QDICT);
3448 
3449         v = qobject_output_visitor_new(&obj);
3450         visit_type_BlockdevOptions(v, NULL, &options, &error_abort);
3451         visit_complete(v, &obj);
3452 
3453         qdict = qobject_to(QDict, obj);
3454         qdict_flatten(qdict);
3455 
3456         /* bdrv_open_inherit() defaults to the values in bdrv_flags (for
3457          * compatibility with other callers) rather than what we want as the
3458          * real defaults. Apply the defaults here instead. */
3459         qdict_set_default_str(qdict, BDRV_OPT_CACHE_DIRECT, "off");
3460         qdict_set_default_str(qdict, BDRV_OPT_CACHE_NO_FLUSH, "off");
3461         qdict_set_default_str(qdict, BDRV_OPT_READ_ONLY, "off");
3462         qdict_set_default_str(qdict, BDRV_OPT_AUTO_READ_ONLY, "off");
3463 
3464     }
3465 
3466     bs = bdrv_open_inherit(NULL, reference, qdict, 0, NULL, NULL, 0, errp);
3467     obj = NULL;
3468     qobject_unref(obj);
3469     visit_free(v);
3470     return bs;
3471 }
3472 
3473 static BlockDriverState *bdrv_append_temp_snapshot(BlockDriverState *bs,
3474                                                    int flags,
3475                                                    QDict *snapshot_options,
3476                                                    Error **errp)
3477 {
3478     /* TODO: extra byte is a hack to ensure MAX_PATH space on Windows. */
3479     char *tmp_filename = g_malloc0(PATH_MAX + 1);
3480     int64_t total_size;
3481     QemuOpts *opts = NULL;
3482     BlockDriverState *bs_snapshot = NULL;
3483     int ret;
3484 
3485     /* if snapshot, we create a temporary backing file and open it
3486        instead of opening 'filename' directly */
3487 
3488     /* Get the required size from the image */
3489     total_size = bdrv_getlength(bs);
3490     if (total_size < 0) {
3491         error_setg_errno(errp, -total_size, "Could not get image size");
3492         goto out;
3493     }
3494 
3495     /* Create the temporary image */
3496     ret = get_tmp_filename(tmp_filename, PATH_MAX + 1);
3497     if (ret < 0) {
3498         error_setg_errno(errp, -ret, "Could not get temporary filename");
3499         goto out;
3500     }
3501 
3502     opts = qemu_opts_create(bdrv_qcow2.create_opts, NULL, 0,
3503                             &error_abort);
3504     qemu_opt_set_number(opts, BLOCK_OPT_SIZE, total_size, &error_abort);
3505     ret = bdrv_create(&bdrv_qcow2, tmp_filename, opts, errp);
3506     qemu_opts_del(opts);
3507     if (ret < 0) {
3508         error_prepend(errp, "Could not create temporary overlay '%s': ",
3509                       tmp_filename);
3510         goto out;
3511     }
3512 
3513     /* Prepare options QDict for the temporary file */
3514     qdict_put_str(snapshot_options, "file.driver", "file");
3515     qdict_put_str(snapshot_options, "file.filename", tmp_filename);
3516     qdict_put_str(snapshot_options, "driver", "qcow2");
3517 
3518     bs_snapshot = bdrv_open(NULL, NULL, snapshot_options, flags, errp);
3519     snapshot_options = NULL;
3520     if (!bs_snapshot) {
3521         goto out;
3522     }
3523 
3524     ret = bdrv_append(bs_snapshot, bs, errp);
3525     if (ret < 0) {
3526         bs_snapshot = NULL;
3527         goto out;
3528     }
3529 
3530 out:
3531     qobject_unref(snapshot_options);
3532     g_free(tmp_filename);
3533     return bs_snapshot;
3534 }
3535 
3536 /*
3537  * Opens a disk image (raw, qcow2, vmdk, ...)
3538  *
3539  * options is a QDict of options to pass to the block drivers, or NULL for an
3540  * empty set of options. The reference to the QDict belongs to the block layer
3541  * after the call (even on failure), so if the caller intends to reuse the
3542  * dictionary, it needs to use qobject_ref() before calling bdrv_open.
3543  *
3544  * If *pbs is NULL, a new BDS will be created with a pointer to it stored there.
3545  * If it is not NULL, the referenced BDS will be reused.
3546  *
3547  * The reference parameter may be used to specify an existing block device which
3548  * should be opened. If specified, neither options nor a filename may be given,
3549  * nor can an existing BDS be reused (that is, *pbs has to be NULL).
3550  */
3551 static BlockDriverState *bdrv_open_inherit(const char *filename,
3552                                            const char *reference,
3553                                            QDict *options, int flags,
3554                                            BlockDriverState *parent,
3555                                            const BdrvChildClass *child_class,
3556                                            BdrvChildRole child_role,
3557                                            Error **errp)
3558 {
3559     int ret;
3560     BlockBackend *file = NULL;
3561     BlockDriverState *bs;
3562     BlockDriver *drv = NULL;
3563     BdrvChild *child;
3564     const char *drvname;
3565     const char *backing;
3566     Error *local_err = NULL;
3567     QDict *snapshot_options = NULL;
3568     int snapshot_flags = 0;
3569 
3570     assert(!child_class || !flags);
3571     assert(!child_class == !parent);
3572 
3573     if (reference) {
3574         bool options_non_empty = options ? qdict_size(options) : false;
3575         qobject_unref(options);
3576 
3577         if (filename || options_non_empty) {
3578             error_setg(errp, "Cannot reference an existing block device with "
3579                        "additional options or a new filename");
3580             return NULL;
3581         }
3582 
3583         bs = bdrv_lookup_bs(reference, reference, errp);
3584         if (!bs) {
3585             return NULL;
3586         }
3587 
3588         bdrv_ref(bs);
3589         return bs;
3590     }
3591 
3592     bs = bdrv_new();
3593 
3594     /* NULL means an empty set of options */
3595     if (options == NULL) {
3596         options = qdict_new();
3597     }
3598 
3599     /* json: syntax counts as explicit options, as if in the QDict */
3600     parse_json_protocol(options, &filename, &local_err);
3601     if (local_err) {
3602         goto fail;
3603     }
3604 
3605     bs->explicit_options = qdict_clone_shallow(options);
3606 
3607     if (child_class) {
3608         bool parent_is_format;
3609 
3610         if (parent->drv) {
3611             parent_is_format = parent->drv->is_format;
3612         } else {
3613             /*
3614              * parent->drv is not set yet because this node is opened for
3615              * (potential) format probing.  That means that @parent is going
3616              * to be a format node.
3617              */
3618             parent_is_format = true;
3619         }
3620 
3621         bs->inherits_from = parent;
3622         child_class->inherit_options(child_role, parent_is_format,
3623                                      &flags, options,
3624                                      parent->open_flags, parent->options);
3625     }
3626 
3627     ret = bdrv_fill_options(&options, filename, &flags, &local_err);
3628     if (ret < 0) {
3629         goto fail;
3630     }
3631 
3632     /*
3633      * Set the BDRV_O_RDWR and BDRV_O_ALLOW_RDWR flags.
3634      * Caution: getting a boolean member of @options requires care.
3635      * When @options come from -blockdev or blockdev_add, members are
3636      * typed according to the QAPI schema, but when they come from
3637      * -drive, they're all QString.
3638      */
3639     if (g_strcmp0(qdict_get_try_str(options, BDRV_OPT_READ_ONLY), "on") &&
3640         !qdict_get_try_bool(options, BDRV_OPT_READ_ONLY, false)) {
3641         flags |= (BDRV_O_RDWR | BDRV_O_ALLOW_RDWR);
3642     } else {
3643         flags &= ~BDRV_O_RDWR;
3644     }
3645 
3646     if (flags & BDRV_O_SNAPSHOT) {
3647         snapshot_options = qdict_new();
3648         bdrv_temp_snapshot_options(&snapshot_flags, snapshot_options,
3649                                    flags, options);
3650         /* Let bdrv_backing_options() override "read-only" */
3651         qdict_del(options, BDRV_OPT_READ_ONLY);
3652         bdrv_inherited_options(BDRV_CHILD_COW, true,
3653                                &flags, options, flags, options);
3654     }
3655 
3656     bs->open_flags = flags;
3657     bs->options = options;
3658     options = qdict_clone_shallow(options);
3659 
3660     /* Find the right image format driver */
3661     /* See cautionary note on accessing @options above */
3662     drvname = qdict_get_try_str(options, "driver");
3663     if (drvname) {
3664         drv = bdrv_find_format(drvname);
3665         if (!drv) {
3666             error_setg(errp, "Unknown driver: '%s'", drvname);
3667             goto fail;
3668         }
3669     }
3670 
3671     assert(drvname || !(flags & BDRV_O_PROTOCOL));
3672 
3673     /* See cautionary note on accessing @options above */
3674     backing = qdict_get_try_str(options, "backing");
3675     if (qobject_to(QNull, qdict_get(options, "backing")) != NULL ||
3676         (backing && *backing == '\0'))
3677     {
3678         if (backing) {
3679             warn_report("Use of \"backing\": \"\" is deprecated; "
3680                         "use \"backing\": null instead");
3681         }
3682         flags |= BDRV_O_NO_BACKING;
3683         qdict_del(bs->explicit_options, "backing");
3684         qdict_del(bs->options, "backing");
3685         qdict_del(options, "backing");
3686     }
3687 
3688     /* Open image file without format layer. This BlockBackend is only used for
3689      * probing, the block drivers will do their own bdrv_open_child() for the
3690      * same BDS, which is why we put the node name back into options. */
3691     if ((flags & BDRV_O_PROTOCOL) == 0) {
3692         BlockDriverState *file_bs;
3693 
3694         file_bs = bdrv_open_child_bs(filename, options, "file", bs,
3695                                      &child_of_bds, BDRV_CHILD_IMAGE,
3696                                      true, &local_err);
3697         if (local_err) {
3698             goto fail;
3699         }
3700         if (file_bs != NULL) {
3701             /* Not requesting BLK_PERM_CONSISTENT_READ because we're only
3702              * looking at the header to guess the image format. This works even
3703              * in cases where a guest would not see a consistent state. */
3704             file = blk_new(bdrv_get_aio_context(file_bs), 0, BLK_PERM_ALL);
3705             blk_insert_bs(file, file_bs, &local_err);
3706             bdrv_unref(file_bs);
3707             if (local_err) {
3708                 goto fail;
3709             }
3710 
3711             qdict_put_str(options, "file", bdrv_get_node_name(file_bs));
3712         }
3713     }
3714 
3715     /* Image format probing */
3716     bs->probed = !drv;
3717     if (!drv && file) {
3718         ret = find_image_format(file, filename, &drv, &local_err);
3719         if (ret < 0) {
3720             goto fail;
3721         }
3722         /*
3723          * This option update would logically belong in bdrv_fill_options(),
3724          * but we first need to open bs->file for the probing to work, while
3725          * opening bs->file already requires the (mostly) final set of options
3726          * so that cache mode etc. can be inherited.
3727          *
3728          * Adding the driver later is somewhat ugly, but it's not an option
3729          * that would ever be inherited, so it's correct. We just need to make
3730          * sure to update both bs->options (which has the full effective
3731          * options for bs) and options (which has file.* already removed).
3732          */
3733         qdict_put_str(bs->options, "driver", drv->format_name);
3734         qdict_put_str(options, "driver", drv->format_name);
3735     } else if (!drv) {
3736         error_setg(errp, "Must specify either driver or file");
3737         goto fail;
3738     }
3739 
3740     /* BDRV_O_PROTOCOL must be set iff a protocol BDS is about to be created */
3741     assert(!!(flags & BDRV_O_PROTOCOL) == !!drv->bdrv_file_open);
3742     /* file must be NULL if a protocol BDS is about to be created
3743      * (the inverse results in an error message from bdrv_open_common()) */
3744     assert(!(flags & BDRV_O_PROTOCOL) || !file);
3745 
3746     /* Open the image */
3747     ret = bdrv_open_common(bs, file, options, &local_err);
3748     if (ret < 0) {
3749         goto fail;
3750     }
3751 
3752     if (file) {
3753         blk_unref(file);
3754         file = NULL;
3755     }
3756 
3757     /* If there is a backing file, use it */
3758     if ((flags & BDRV_O_NO_BACKING) == 0) {
3759         ret = bdrv_open_backing_file(bs, options, "backing", &local_err);
3760         if (ret < 0) {
3761             goto close_and_fail;
3762         }
3763     }
3764 
3765     /* Remove all children options and references
3766      * from bs->options and bs->explicit_options */
3767     QLIST_FOREACH(child, &bs->children, next) {
3768         char *child_key_dot;
3769         child_key_dot = g_strdup_printf("%s.", child->name);
3770         qdict_extract_subqdict(bs->explicit_options, NULL, child_key_dot);
3771         qdict_extract_subqdict(bs->options, NULL, child_key_dot);
3772         qdict_del(bs->explicit_options, child->name);
3773         qdict_del(bs->options, child->name);
3774         g_free(child_key_dot);
3775     }
3776 
3777     /* Check if any unknown options were used */
3778     if (qdict_size(options) != 0) {
3779         const QDictEntry *entry = qdict_first(options);
3780         if (flags & BDRV_O_PROTOCOL) {
3781             error_setg(errp, "Block protocol '%s' doesn't support the option "
3782                        "'%s'", drv->format_name, entry->key);
3783         } else {
3784             error_setg(errp,
3785                        "Block format '%s' does not support the option '%s'",
3786                        drv->format_name, entry->key);
3787         }
3788 
3789         goto close_and_fail;
3790     }
3791 
3792     bdrv_parent_cb_change_media(bs, true);
3793 
3794     qobject_unref(options);
3795     options = NULL;
3796 
3797     /* For snapshot=on, create a temporary qcow2 overlay. bs points to the
3798      * temporary snapshot afterwards. */
3799     if (snapshot_flags) {
3800         BlockDriverState *snapshot_bs;
3801         snapshot_bs = bdrv_append_temp_snapshot(bs, snapshot_flags,
3802                                                 snapshot_options, &local_err);
3803         snapshot_options = NULL;
3804         if (local_err) {
3805             goto close_and_fail;
3806         }
3807         /* We are not going to return bs but the overlay on top of it
3808          * (snapshot_bs); thus, we have to drop the strong reference to bs
3809          * (which we obtained by calling bdrv_new()). bs will not be deleted,
3810          * though, because the overlay still has a reference to it. */
3811         bdrv_unref(bs);
3812         bs = snapshot_bs;
3813     }
3814 
3815     return bs;
3816 
3817 fail:
3818     blk_unref(file);
3819     qobject_unref(snapshot_options);
3820     qobject_unref(bs->explicit_options);
3821     qobject_unref(bs->options);
3822     qobject_unref(options);
3823     bs->options = NULL;
3824     bs->explicit_options = NULL;
3825     bdrv_unref(bs);
3826     error_propagate(errp, local_err);
3827     return NULL;
3828 
3829 close_and_fail:
3830     bdrv_unref(bs);
3831     qobject_unref(snapshot_options);
3832     qobject_unref(options);
3833     error_propagate(errp, local_err);
3834     return NULL;
3835 }
3836 
3837 BlockDriverState *bdrv_open(const char *filename, const char *reference,
3838                             QDict *options, int flags, Error **errp)
3839 {
3840     return bdrv_open_inherit(filename, reference, options, flags, NULL,
3841                              NULL, 0, errp);
3842 }
3843 
3844 /* Return true if the NULL-terminated @list contains @str */
3845 static bool is_str_in_list(const char *str, const char *const *list)
3846 {
3847     if (str && list) {
3848         int i;
3849         for (i = 0; list[i] != NULL; i++) {
3850             if (!strcmp(str, list[i])) {
3851                 return true;
3852             }
3853         }
3854     }
3855     return false;
3856 }
3857 
3858 /*
3859  * Check that every option set in @bs->options is also set in
3860  * @new_opts.
3861  *
3862  * Options listed in the common_options list and in
3863  * @bs->drv->mutable_opts are skipped.
3864  *
3865  * Return 0 on success, otherwise return -EINVAL and set @errp.
3866  */
3867 static int bdrv_reset_options_allowed(BlockDriverState *bs,
3868                                       const QDict *new_opts, Error **errp)
3869 {
3870     const QDictEntry *e;
3871     /* These options are common to all block drivers and are handled
3872      * in bdrv_reopen_prepare() so they can be left out of @new_opts */
3873     const char *const common_options[] = {
3874         "node-name", "discard", "cache.direct", "cache.no-flush",
3875         "read-only", "auto-read-only", "detect-zeroes", NULL
3876     };
3877 
3878     for (e = qdict_first(bs->options); e; e = qdict_next(bs->options, e)) {
3879         if (!qdict_haskey(new_opts, e->key) &&
3880             !is_str_in_list(e->key, common_options) &&
3881             !is_str_in_list(e->key, bs->drv->mutable_opts)) {
3882             error_setg(errp, "Option '%s' cannot be reset "
3883                        "to its default value", e->key);
3884             return -EINVAL;
3885         }
3886     }
3887 
3888     return 0;
3889 }
3890 
3891 /*
3892  * Returns true if @child can be reached recursively from @bs
3893  */
3894 static bool bdrv_recurse_has_child(BlockDriverState *bs,
3895                                    BlockDriverState *child)
3896 {
3897     BdrvChild *c;
3898 
3899     if (bs == child) {
3900         return true;
3901     }
3902 
3903     QLIST_FOREACH(c, &bs->children, next) {
3904         if (bdrv_recurse_has_child(c->bs, child)) {
3905             return true;
3906         }
3907     }
3908 
3909     return false;
3910 }
3911 
3912 /*
3913  * Adds a BlockDriverState to a simple queue for an atomic, transactional
3914  * reopen of multiple devices.
3915  *
3916  * bs_queue can either be an existing BlockReopenQueue that has had QTAILQ_INIT
3917  * already performed, or alternatively may be NULL a new BlockReopenQueue will
3918  * be created and initialized. This newly created BlockReopenQueue should be
3919  * passed back in for subsequent calls that are intended to be of the same
3920  * atomic 'set'.
3921  *
3922  * bs is the BlockDriverState to add to the reopen queue.
3923  *
3924  * options contains the changed options for the associated bs
3925  * (the BlockReopenQueue takes ownership)
3926  *
3927  * flags contains the open flags for the associated bs
3928  *
3929  * returns a pointer to bs_queue, which is either the newly allocated
3930  * bs_queue, or the existing bs_queue being used.
3931  *
3932  * bs must be drained between bdrv_reopen_queue() and bdrv_reopen_multiple().
3933  */
3934 static BlockReopenQueue *bdrv_reopen_queue_child(BlockReopenQueue *bs_queue,
3935                                                  BlockDriverState *bs,
3936                                                  QDict *options,
3937                                                  const BdrvChildClass *klass,
3938                                                  BdrvChildRole role,
3939                                                  bool parent_is_format,
3940                                                  QDict *parent_options,
3941                                                  int parent_flags,
3942                                                  bool keep_old_opts)
3943 {
3944     assert(bs != NULL);
3945 
3946     BlockReopenQueueEntry *bs_entry;
3947     BdrvChild *child;
3948     QDict *old_options, *explicit_options, *options_copy;
3949     int flags;
3950     QemuOpts *opts;
3951 
3952     /* Make sure that the caller remembered to use a drained section. This is
3953      * important to avoid graph changes between the recursive queuing here and
3954      * bdrv_reopen_multiple(). */
3955     assert(bs->quiesce_counter > 0);
3956 
3957     if (bs_queue == NULL) {
3958         bs_queue = g_new0(BlockReopenQueue, 1);
3959         QTAILQ_INIT(bs_queue);
3960     }
3961 
3962     if (!options) {
3963         options = qdict_new();
3964     }
3965 
3966     /* Check if this BlockDriverState is already in the queue */
3967     QTAILQ_FOREACH(bs_entry, bs_queue, entry) {
3968         if (bs == bs_entry->state.bs) {
3969             break;
3970         }
3971     }
3972 
3973     /*
3974      * Precedence of options:
3975      * 1. Explicitly passed in options (highest)
3976      * 2. Retained from explicitly set options of bs
3977      * 3. Inherited from parent node
3978      * 4. Retained from effective options of bs
3979      */
3980 
3981     /* Old explicitly set values (don't overwrite by inherited value) */
3982     if (bs_entry || keep_old_opts) {
3983         old_options = qdict_clone_shallow(bs_entry ?
3984                                           bs_entry->state.explicit_options :
3985                                           bs->explicit_options);
3986         bdrv_join_options(bs, options, old_options);
3987         qobject_unref(old_options);
3988     }
3989 
3990     explicit_options = qdict_clone_shallow(options);
3991 
3992     /* Inherit from parent node */
3993     if (parent_options) {
3994         flags = 0;
3995         klass->inherit_options(role, parent_is_format, &flags, options,
3996                                parent_flags, parent_options);
3997     } else {
3998         flags = bdrv_get_flags(bs);
3999     }
4000 
4001     if (keep_old_opts) {
4002         /* Old values are used for options that aren't set yet */
4003         old_options = qdict_clone_shallow(bs->options);
4004         bdrv_join_options(bs, options, old_options);
4005         qobject_unref(old_options);
4006     }
4007 
4008     /* We have the final set of options so let's update the flags */
4009     options_copy = qdict_clone_shallow(options);
4010     opts = qemu_opts_create(&bdrv_runtime_opts, NULL, 0, &error_abort);
4011     qemu_opts_absorb_qdict(opts, options_copy, NULL);
4012     update_flags_from_options(&flags, opts);
4013     qemu_opts_del(opts);
4014     qobject_unref(options_copy);
4015 
4016     /* bdrv_open_inherit() sets and clears some additional flags internally */
4017     flags &= ~BDRV_O_PROTOCOL;
4018     if (flags & BDRV_O_RDWR) {
4019         flags |= BDRV_O_ALLOW_RDWR;
4020     }
4021 
4022     if (!bs_entry) {
4023         bs_entry = g_new0(BlockReopenQueueEntry, 1);
4024         QTAILQ_INSERT_TAIL(bs_queue, bs_entry, entry);
4025     } else {
4026         qobject_unref(bs_entry->state.options);
4027         qobject_unref(bs_entry->state.explicit_options);
4028     }
4029 
4030     bs_entry->state.bs = bs;
4031     bs_entry->state.options = options;
4032     bs_entry->state.explicit_options = explicit_options;
4033     bs_entry->state.flags = flags;
4034 
4035     /*
4036      * If keep_old_opts is false then it means that unspecified
4037      * options must be reset to their original value. We don't allow
4038      * resetting 'backing' but we need to know if the option is
4039      * missing in order to decide if we have to return an error.
4040      */
4041     if (!keep_old_opts) {
4042         bs_entry->state.backing_missing =
4043             !qdict_haskey(options, "backing") &&
4044             !qdict_haskey(options, "backing.driver");
4045     }
4046 
4047     QLIST_FOREACH(child, &bs->children, next) {
4048         QDict *new_child_options = NULL;
4049         bool child_keep_old = keep_old_opts;
4050 
4051         /* reopen can only change the options of block devices that were
4052          * implicitly created and inherited options. For other (referenced)
4053          * block devices, a syntax like "backing.foo" results in an error. */
4054         if (child->bs->inherits_from != bs) {
4055             continue;
4056         }
4057 
4058         /* Check if the options contain a child reference */
4059         if (qdict_haskey(options, child->name)) {
4060             const char *childref = qdict_get_try_str(options, child->name);
4061             /*
4062              * The current child must not be reopened if the child
4063              * reference is null or points to a different node.
4064              */
4065             if (g_strcmp0(childref, child->bs->node_name)) {
4066                 continue;
4067             }
4068             /*
4069              * If the child reference points to the current child then
4070              * reopen it with its existing set of options (note that
4071              * it can still inherit new options from the parent).
4072              */
4073             child_keep_old = true;
4074         } else {
4075             /* Extract child options ("child-name.*") */
4076             char *child_key_dot = g_strdup_printf("%s.", child->name);
4077             qdict_extract_subqdict(explicit_options, NULL, child_key_dot);
4078             qdict_extract_subqdict(options, &new_child_options, child_key_dot);
4079             g_free(child_key_dot);
4080         }
4081 
4082         bdrv_reopen_queue_child(bs_queue, child->bs, new_child_options,
4083                                 child->klass, child->role, bs->drv->is_format,
4084                                 options, flags, child_keep_old);
4085     }
4086 
4087     return bs_queue;
4088 }
4089 
4090 BlockReopenQueue *bdrv_reopen_queue(BlockReopenQueue *bs_queue,
4091                                     BlockDriverState *bs,
4092                                     QDict *options, bool keep_old_opts)
4093 {
4094     return bdrv_reopen_queue_child(bs_queue, bs, options, NULL, 0, false,
4095                                    NULL, 0, keep_old_opts);
4096 }
4097 
4098 void bdrv_reopen_queue_free(BlockReopenQueue *bs_queue)
4099 {
4100     if (bs_queue) {
4101         BlockReopenQueueEntry *bs_entry, *next;
4102         QTAILQ_FOREACH_SAFE(bs_entry, bs_queue, entry, next) {
4103             qobject_unref(bs_entry->state.explicit_options);
4104             qobject_unref(bs_entry->state.options);
4105             g_free(bs_entry);
4106         }
4107         g_free(bs_queue);
4108     }
4109 }
4110 
4111 /*
4112  * Reopen multiple BlockDriverStates atomically & transactionally.
4113  *
4114  * The queue passed in (bs_queue) must have been built up previous
4115  * via bdrv_reopen_queue().
4116  *
4117  * Reopens all BDS specified in the queue, with the appropriate
4118  * flags.  All devices are prepared for reopen, and failure of any
4119  * device will cause all device changes to be abandoned, and intermediate
4120  * data cleaned up.
4121  *
4122  * If all devices prepare successfully, then the changes are committed
4123  * to all devices.
4124  *
4125  * All affected nodes must be drained between bdrv_reopen_queue() and
4126  * bdrv_reopen_multiple().
4127  *
4128  * To be called from the main thread, with all other AioContexts unlocked.
4129  */
4130 int bdrv_reopen_multiple(BlockReopenQueue *bs_queue, Error **errp)
4131 {
4132     int ret = -1;
4133     BlockReopenQueueEntry *bs_entry, *next;
4134     AioContext *ctx;
4135     Transaction *tran = tran_new();
4136     g_autoptr(GHashTable) found = NULL;
4137     g_autoptr(GSList) refresh_list = NULL;
4138 
4139     assert(qemu_get_current_aio_context() == qemu_get_aio_context());
4140     assert(bs_queue != NULL);
4141 
4142     QTAILQ_FOREACH(bs_entry, bs_queue, entry) {
4143         ctx = bdrv_get_aio_context(bs_entry->state.bs);
4144         aio_context_acquire(ctx);
4145         ret = bdrv_flush(bs_entry->state.bs);
4146         aio_context_release(ctx);
4147         if (ret < 0) {
4148             error_setg_errno(errp, -ret, "Error flushing drive");
4149             goto abort;
4150         }
4151     }
4152 
4153     QTAILQ_FOREACH(bs_entry, bs_queue, entry) {
4154         assert(bs_entry->state.bs->quiesce_counter > 0);
4155         ctx = bdrv_get_aio_context(bs_entry->state.bs);
4156         aio_context_acquire(ctx);
4157         ret = bdrv_reopen_prepare(&bs_entry->state, bs_queue, tran, errp);
4158         aio_context_release(ctx);
4159         if (ret < 0) {
4160             goto abort;
4161         }
4162         bs_entry->prepared = true;
4163     }
4164 
4165     found = g_hash_table_new(NULL, NULL);
4166     QTAILQ_FOREACH(bs_entry, bs_queue, entry) {
4167         BDRVReopenState *state = &bs_entry->state;
4168 
4169         refresh_list = bdrv_topological_dfs(refresh_list, found, state->bs);
4170         if (state->old_backing_bs) {
4171             refresh_list = bdrv_topological_dfs(refresh_list, found,
4172                                                 state->old_backing_bs);
4173         }
4174         if (state->old_file_bs) {
4175             refresh_list = bdrv_topological_dfs(refresh_list, found,
4176                                                 state->old_file_bs);
4177         }
4178     }
4179 
4180     /*
4181      * Note that file-posix driver rely on permission update done during reopen
4182      * (even if no permission changed), because it wants "new" permissions for
4183      * reconfiguring the fd and that's why it does it in raw_check_perm(), not
4184      * in raw_reopen_prepare() which is called with "old" permissions.
4185      */
4186     ret = bdrv_list_refresh_perms(refresh_list, bs_queue, tran, errp);
4187     if (ret < 0) {
4188         goto abort;
4189     }
4190 
4191     /*
4192      * If we reach this point, we have success and just need to apply the
4193      * changes.
4194      *
4195      * Reverse order is used to comfort qcow2 driver: on commit it need to write
4196      * IN_USE flag to the image, to mark bitmaps in the image as invalid. But
4197      * children are usually goes after parents in reopen-queue, so go from last
4198      * to first element.
4199      */
4200     QTAILQ_FOREACH_REVERSE(bs_entry, bs_queue, entry) {
4201         ctx = bdrv_get_aio_context(bs_entry->state.bs);
4202         aio_context_acquire(ctx);
4203         bdrv_reopen_commit(&bs_entry->state);
4204         aio_context_release(ctx);
4205     }
4206 
4207     tran_commit(tran);
4208 
4209     QTAILQ_FOREACH_REVERSE(bs_entry, bs_queue, entry) {
4210         BlockDriverState *bs = bs_entry->state.bs;
4211 
4212         if (bs->drv->bdrv_reopen_commit_post) {
4213             ctx = bdrv_get_aio_context(bs);
4214             aio_context_acquire(ctx);
4215             bs->drv->bdrv_reopen_commit_post(&bs_entry->state);
4216             aio_context_release(ctx);
4217         }
4218     }
4219 
4220     ret = 0;
4221     goto cleanup;
4222 
4223 abort:
4224     tran_abort(tran);
4225     QTAILQ_FOREACH_SAFE(bs_entry, bs_queue, entry, next) {
4226         if (bs_entry->prepared) {
4227             ctx = bdrv_get_aio_context(bs_entry->state.bs);
4228             aio_context_acquire(ctx);
4229             bdrv_reopen_abort(&bs_entry->state);
4230             aio_context_release(ctx);
4231         }
4232     }
4233 
4234 cleanup:
4235     bdrv_reopen_queue_free(bs_queue);
4236 
4237     return ret;
4238 }
4239 
4240 int bdrv_reopen(BlockDriverState *bs, QDict *opts, bool keep_old_opts,
4241                 Error **errp)
4242 {
4243     AioContext *ctx = bdrv_get_aio_context(bs);
4244     BlockReopenQueue *queue;
4245     int ret;
4246 
4247     bdrv_subtree_drained_begin(bs);
4248     if (ctx != qemu_get_aio_context()) {
4249         aio_context_release(ctx);
4250     }
4251 
4252     queue = bdrv_reopen_queue(NULL, bs, opts, keep_old_opts);
4253     ret = bdrv_reopen_multiple(queue, errp);
4254 
4255     if (ctx != qemu_get_aio_context()) {
4256         aio_context_acquire(ctx);
4257     }
4258     bdrv_subtree_drained_end(bs);
4259 
4260     return ret;
4261 }
4262 
4263 int bdrv_reopen_set_read_only(BlockDriverState *bs, bool read_only,
4264                               Error **errp)
4265 {
4266     QDict *opts = qdict_new();
4267 
4268     qdict_put_bool(opts, BDRV_OPT_READ_ONLY, read_only);
4269 
4270     return bdrv_reopen(bs, opts, true, errp);
4271 }
4272 
4273 /*
4274  * Take a BDRVReopenState and check if the value of 'backing' in the
4275  * reopen_state->options QDict is valid or not.
4276  *
4277  * If 'backing' is missing from the QDict then return 0.
4278  *
4279  * If 'backing' contains the node name of the backing file of
4280  * reopen_state->bs then return 0.
4281  *
4282  * If 'backing' contains a different node name (or is null) then check
4283  * whether the current backing file can be replaced with the new one.
4284  * If that's the case then reopen_state->replace_backing_bs is set to
4285  * true and reopen_state->new_backing_bs contains a pointer to the new
4286  * backing BlockDriverState (or NULL).
4287  *
4288  * Return 0 on success, otherwise return < 0 and set @errp.
4289  */
4290 static int bdrv_reopen_parse_file_or_backing(BDRVReopenState *reopen_state,
4291                                              bool is_backing, Transaction *tran,
4292                                              Error **errp)
4293 {
4294     BlockDriverState *bs = reopen_state->bs;
4295     BlockDriverState *new_child_bs;
4296     BlockDriverState *old_child_bs = is_backing ? child_bs(bs->backing) :
4297                                                   child_bs(bs->file);
4298     const char *child_name = is_backing ? "backing" : "file";
4299     QObject *value;
4300     const char *str;
4301 
4302     value = qdict_get(reopen_state->options, child_name);
4303     if (value == NULL) {
4304         return 0;
4305     }
4306 
4307     switch (qobject_type(value)) {
4308     case QTYPE_QNULL:
4309         assert(is_backing); /* The 'file' option does not allow a null value */
4310         new_child_bs = NULL;
4311         break;
4312     case QTYPE_QSTRING:
4313         str = qstring_get_str(qobject_to(QString, value));
4314         new_child_bs = bdrv_lookup_bs(NULL, str, errp);
4315         if (new_child_bs == NULL) {
4316             return -EINVAL;
4317         } else if (bdrv_recurse_has_child(new_child_bs, bs)) {
4318             error_setg(errp, "Making '%s' a %s child of '%s' would create a "
4319                        "cycle", str, child_name, bs->node_name);
4320             return -EINVAL;
4321         }
4322         break;
4323     default:
4324         /*
4325          * The options QDict has been flattened, so 'backing' and 'file'
4326          * do not allow any other data type here.
4327          */
4328         g_assert_not_reached();
4329     }
4330 
4331     if (old_child_bs == new_child_bs) {
4332         return 0;
4333     }
4334 
4335     if (old_child_bs) {
4336         if (bdrv_skip_implicit_filters(old_child_bs) == new_child_bs) {
4337             return 0;
4338         }
4339 
4340         if (old_child_bs->implicit) {
4341             error_setg(errp, "Cannot replace implicit %s child of %s",
4342                        child_name, bs->node_name);
4343             return -EPERM;
4344         }
4345     }
4346 
4347     if (bs->drv->is_filter && !old_child_bs) {
4348         /*
4349          * Filters always have a file or a backing child, so we are trying to
4350          * change wrong child
4351          */
4352         error_setg(errp, "'%s' is a %s filter node that does not support a "
4353                    "%s child", bs->node_name, bs->drv->format_name, child_name);
4354         return -EINVAL;
4355     }
4356 
4357     if (is_backing) {
4358         reopen_state->old_backing_bs = old_child_bs;
4359     } else {
4360         reopen_state->old_file_bs = old_child_bs;
4361     }
4362 
4363     return bdrv_set_file_or_backing_noperm(bs, new_child_bs, is_backing,
4364                                            tran, errp);
4365 }
4366 
4367 /*
4368  * Prepares a BlockDriverState for reopen. All changes are staged in the
4369  * 'opaque' field of the BDRVReopenState, which is used and allocated by
4370  * the block driver layer .bdrv_reopen_prepare()
4371  *
4372  * bs is the BlockDriverState to reopen
4373  * flags are the new open flags
4374  * queue is the reopen queue
4375  *
4376  * Returns 0 on success, non-zero on error.  On error errp will be set
4377  * as well.
4378  *
4379  * On failure, bdrv_reopen_abort() will be called to clean up any data.
4380  * It is the responsibility of the caller to then call the abort() or
4381  * commit() for any other BDS that have been left in a prepare() state
4382  *
4383  */
4384 static int bdrv_reopen_prepare(BDRVReopenState *reopen_state,
4385                                BlockReopenQueue *queue,
4386                                Transaction *change_child_tran, Error **errp)
4387 {
4388     int ret = -1;
4389     int old_flags;
4390     Error *local_err = NULL;
4391     BlockDriver *drv;
4392     QemuOpts *opts;
4393     QDict *orig_reopen_opts;
4394     char *discard = NULL;
4395     bool read_only;
4396     bool drv_prepared = false;
4397 
4398     assert(reopen_state != NULL);
4399     assert(reopen_state->bs->drv != NULL);
4400     drv = reopen_state->bs->drv;
4401 
4402     /* This function and each driver's bdrv_reopen_prepare() remove
4403      * entries from reopen_state->options as they are processed, so
4404      * we need to make a copy of the original QDict. */
4405     orig_reopen_opts = qdict_clone_shallow(reopen_state->options);
4406 
4407     /* Process generic block layer options */
4408     opts = qemu_opts_create(&bdrv_runtime_opts, NULL, 0, &error_abort);
4409     if (!qemu_opts_absorb_qdict(opts, reopen_state->options, errp)) {
4410         ret = -EINVAL;
4411         goto error;
4412     }
4413 
4414     /* This was already called in bdrv_reopen_queue_child() so the flags
4415      * are up-to-date. This time we simply want to remove the options from
4416      * QemuOpts in order to indicate that they have been processed. */
4417     old_flags = reopen_state->flags;
4418     update_flags_from_options(&reopen_state->flags, opts);
4419     assert(old_flags == reopen_state->flags);
4420 
4421     discard = qemu_opt_get_del(opts, BDRV_OPT_DISCARD);
4422     if (discard != NULL) {
4423         if (bdrv_parse_discard_flags(discard, &reopen_state->flags) != 0) {
4424             error_setg(errp, "Invalid discard option");
4425             ret = -EINVAL;
4426             goto error;
4427         }
4428     }
4429 
4430     reopen_state->detect_zeroes =
4431         bdrv_parse_detect_zeroes(opts, reopen_state->flags, &local_err);
4432     if (local_err) {
4433         error_propagate(errp, local_err);
4434         ret = -EINVAL;
4435         goto error;
4436     }
4437 
4438     /* All other options (including node-name and driver) must be unchanged.
4439      * Put them back into the QDict, so that they are checked at the end
4440      * of this function. */
4441     qemu_opts_to_qdict(opts, reopen_state->options);
4442 
4443     /* If we are to stay read-only, do not allow permission change
4444      * to r/w. Attempting to set to r/w may fail if either BDRV_O_ALLOW_RDWR is
4445      * not set, or if the BDS still has copy_on_read enabled */
4446     read_only = !(reopen_state->flags & BDRV_O_RDWR);
4447     ret = bdrv_can_set_read_only(reopen_state->bs, read_only, true, &local_err);
4448     if (local_err) {
4449         error_propagate(errp, local_err);
4450         goto error;
4451     }
4452 
4453     if (drv->bdrv_reopen_prepare) {
4454         /*
4455          * If a driver-specific option is missing, it means that we
4456          * should reset it to its default value.
4457          * But not all options allow that, so we need to check it first.
4458          */
4459         ret = bdrv_reset_options_allowed(reopen_state->bs,
4460                                          reopen_state->options, errp);
4461         if (ret) {
4462             goto error;
4463         }
4464 
4465         ret = drv->bdrv_reopen_prepare(reopen_state, queue, &local_err);
4466         if (ret) {
4467             if (local_err != NULL) {
4468                 error_propagate(errp, local_err);
4469             } else {
4470                 bdrv_refresh_filename(reopen_state->bs);
4471                 error_setg(errp, "failed while preparing to reopen image '%s'",
4472                            reopen_state->bs->filename);
4473             }
4474             goto error;
4475         }
4476     } else {
4477         /* It is currently mandatory to have a bdrv_reopen_prepare()
4478          * handler for each supported drv. */
4479         error_setg(errp, "Block format '%s' used by node '%s' "
4480                    "does not support reopening files", drv->format_name,
4481                    bdrv_get_device_or_node_name(reopen_state->bs));
4482         ret = -1;
4483         goto error;
4484     }
4485 
4486     drv_prepared = true;
4487 
4488     /*
4489      * We must provide the 'backing' option if the BDS has a backing
4490      * file or if the image file has a backing file name as part of
4491      * its metadata. Otherwise the 'backing' option can be omitted.
4492      */
4493     if (drv->supports_backing && reopen_state->backing_missing &&
4494         (reopen_state->bs->backing || reopen_state->bs->backing_file[0])) {
4495         error_setg(errp, "backing is missing for '%s'",
4496                    reopen_state->bs->node_name);
4497         ret = -EINVAL;
4498         goto error;
4499     }
4500 
4501     /*
4502      * Allow changing the 'backing' option. The new value can be
4503      * either a reference to an existing node (using its node name)
4504      * or NULL to simply detach the current backing file.
4505      */
4506     ret = bdrv_reopen_parse_file_or_backing(reopen_state, true,
4507                                             change_child_tran, errp);
4508     if (ret < 0) {
4509         goto error;
4510     }
4511     qdict_del(reopen_state->options, "backing");
4512 
4513     /* Allow changing the 'file' option. In this case NULL is not allowed */
4514     ret = bdrv_reopen_parse_file_or_backing(reopen_state, false,
4515                                             change_child_tran, errp);
4516     if (ret < 0) {
4517         goto error;
4518     }
4519     qdict_del(reopen_state->options, "file");
4520 
4521     /* Options that are not handled are only okay if they are unchanged
4522      * compared to the old state. It is expected that some options are only
4523      * used for the initial open, but not reopen (e.g. filename) */
4524     if (qdict_size(reopen_state->options)) {
4525         const QDictEntry *entry = qdict_first(reopen_state->options);
4526 
4527         do {
4528             QObject *new = entry->value;
4529             QObject *old = qdict_get(reopen_state->bs->options, entry->key);
4530 
4531             /* Allow child references (child_name=node_name) as long as they
4532              * point to the current child (i.e. everything stays the same). */
4533             if (qobject_type(new) == QTYPE_QSTRING) {
4534                 BdrvChild *child;
4535                 QLIST_FOREACH(child, &reopen_state->bs->children, next) {
4536                     if (!strcmp(child->name, entry->key)) {
4537                         break;
4538                     }
4539                 }
4540 
4541                 if (child) {
4542                     if (!strcmp(child->bs->node_name,
4543                                 qstring_get_str(qobject_to(QString, new)))) {
4544                         continue; /* Found child with this name, skip option */
4545                     }
4546                 }
4547             }
4548 
4549             /*
4550              * TODO: When using -drive to specify blockdev options, all values
4551              * will be strings; however, when using -blockdev, blockdev-add or
4552              * filenames using the json:{} pseudo-protocol, they will be
4553              * correctly typed.
4554              * In contrast, reopening options are (currently) always strings
4555              * (because you can only specify them through qemu-io; all other
4556              * callers do not specify any options).
4557              * Therefore, when using anything other than -drive to create a BDS,
4558              * this cannot detect non-string options as unchanged, because
4559              * qobject_is_equal() always returns false for objects of different
4560              * type.  In the future, this should be remedied by correctly typing
4561              * all options.  For now, this is not too big of an issue because
4562              * the user can simply omit options which cannot be changed anyway,
4563              * so they will stay unchanged.
4564              */
4565             if (!qobject_is_equal(new, old)) {
4566                 error_setg(errp, "Cannot change the option '%s'", entry->key);
4567                 ret = -EINVAL;
4568                 goto error;
4569             }
4570         } while ((entry = qdict_next(reopen_state->options, entry)));
4571     }
4572 
4573     ret = 0;
4574 
4575     /* Restore the original reopen_state->options QDict */
4576     qobject_unref(reopen_state->options);
4577     reopen_state->options = qobject_ref(orig_reopen_opts);
4578 
4579 error:
4580     if (ret < 0 && drv_prepared) {
4581         /* drv->bdrv_reopen_prepare() has succeeded, so we need to
4582          * call drv->bdrv_reopen_abort() before signaling an error
4583          * (bdrv_reopen_multiple() will not call bdrv_reopen_abort()
4584          * when the respective bdrv_reopen_prepare() has failed) */
4585         if (drv->bdrv_reopen_abort) {
4586             drv->bdrv_reopen_abort(reopen_state);
4587         }
4588     }
4589     qemu_opts_del(opts);
4590     qobject_unref(orig_reopen_opts);
4591     g_free(discard);
4592     return ret;
4593 }
4594 
4595 /*
4596  * Takes the staged changes for the reopen from bdrv_reopen_prepare(), and
4597  * makes them final by swapping the staging BlockDriverState contents into
4598  * the active BlockDriverState contents.
4599  */
4600 static void bdrv_reopen_commit(BDRVReopenState *reopen_state)
4601 {
4602     BlockDriver *drv;
4603     BlockDriverState *bs;
4604     BdrvChild *child;
4605 
4606     assert(reopen_state != NULL);
4607     bs = reopen_state->bs;
4608     drv = bs->drv;
4609     assert(drv != NULL);
4610 
4611     /* If there are any driver level actions to take */
4612     if (drv->bdrv_reopen_commit) {
4613         drv->bdrv_reopen_commit(reopen_state);
4614     }
4615 
4616     /* set BDS specific flags now */
4617     qobject_unref(bs->explicit_options);
4618     qobject_unref(bs->options);
4619     qobject_ref(reopen_state->explicit_options);
4620     qobject_ref(reopen_state->options);
4621 
4622     bs->explicit_options   = reopen_state->explicit_options;
4623     bs->options            = reopen_state->options;
4624     bs->open_flags         = reopen_state->flags;
4625     bs->detect_zeroes      = reopen_state->detect_zeroes;
4626 
4627     /* Remove child references from bs->options and bs->explicit_options.
4628      * Child options were already removed in bdrv_reopen_queue_child() */
4629     QLIST_FOREACH(child, &bs->children, next) {
4630         qdict_del(bs->explicit_options, child->name);
4631         qdict_del(bs->options, child->name);
4632     }
4633     /* backing is probably removed, so it's not handled by previous loop */
4634     qdict_del(bs->explicit_options, "backing");
4635     qdict_del(bs->options, "backing");
4636 
4637     bdrv_refresh_limits(bs, NULL, NULL);
4638 }
4639 
4640 /*
4641  * Abort the reopen, and delete and free the staged changes in
4642  * reopen_state
4643  */
4644 static void bdrv_reopen_abort(BDRVReopenState *reopen_state)
4645 {
4646     BlockDriver *drv;
4647 
4648     assert(reopen_state != NULL);
4649     drv = reopen_state->bs->drv;
4650     assert(drv != NULL);
4651 
4652     if (drv->bdrv_reopen_abort) {
4653         drv->bdrv_reopen_abort(reopen_state);
4654     }
4655 }
4656 
4657 
4658 static void bdrv_close(BlockDriverState *bs)
4659 {
4660     BdrvAioNotifier *ban, *ban_next;
4661     BdrvChild *child, *next;
4662 
4663     assert(!bs->refcnt);
4664 
4665     bdrv_drained_begin(bs); /* complete I/O */
4666     bdrv_flush(bs);
4667     bdrv_drain(bs); /* in case flush left pending I/O */
4668 
4669     if (bs->drv) {
4670         if (bs->drv->bdrv_close) {
4671             /* Must unfreeze all children, so bdrv_unref_child() works */
4672             bs->drv->bdrv_close(bs);
4673         }
4674         bs->drv = NULL;
4675     }
4676 
4677     QLIST_FOREACH_SAFE(child, &bs->children, next, next) {
4678         bdrv_unref_child(bs, child);
4679     }
4680 
4681     bs->backing = NULL;
4682     bs->file = NULL;
4683     g_free(bs->opaque);
4684     bs->opaque = NULL;
4685     qatomic_set(&bs->copy_on_read, 0);
4686     bs->backing_file[0] = '\0';
4687     bs->backing_format[0] = '\0';
4688     bs->total_sectors = 0;
4689     bs->encrypted = false;
4690     bs->sg = false;
4691     qobject_unref(bs->options);
4692     qobject_unref(bs->explicit_options);
4693     bs->options = NULL;
4694     bs->explicit_options = NULL;
4695     qobject_unref(bs->full_open_options);
4696     bs->full_open_options = NULL;
4697 
4698     bdrv_release_named_dirty_bitmaps(bs);
4699     assert(QLIST_EMPTY(&bs->dirty_bitmaps));
4700 
4701     QLIST_FOREACH_SAFE(ban, &bs->aio_notifiers, list, ban_next) {
4702         g_free(ban);
4703     }
4704     QLIST_INIT(&bs->aio_notifiers);
4705     bdrv_drained_end(bs);
4706 
4707     /*
4708      * If we're still inside some bdrv_drain_all_begin()/end() sections, end
4709      * them now since this BDS won't exist anymore when bdrv_drain_all_end()
4710      * gets called.
4711      */
4712     if (bs->quiesce_counter) {
4713         bdrv_drain_all_end_quiesce(bs);
4714     }
4715 }
4716 
4717 void bdrv_close_all(void)
4718 {
4719     assert(job_next(NULL) == NULL);
4720 
4721     /* Drop references from requests still in flight, such as canceled block
4722      * jobs whose AIO context has not been polled yet */
4723     bdrv_drain_all();
4724 
4725     blk_remove_all_bs();
4726     blockdev_close_all_bdrv_states();
4727 
4728     assert(QTAILQ_EMPTY(&all_bdrv_states));
4729 }
4730 
4731 static bool should_update_child(BdrvChild *c, BlockDriverState *to)
4732 {
4733     GQueue *queue;
4734     GHashTable *found;
4735     bool ret;
4736 
4737     if (c->klass->stay_at_node) {
4738         return false;
4739     }
4740 
4741     /* If the child @c belongs to the BDS @to, replacing the current
4742      * c->bs by @to would mean to create a loop.
4743      *
4744      * Such a case occurs when appending a BDS to a backing chain.
4745      * For instance, imagine the following chain:
4746      *
4747      *   guest device -> node A -> further backing chain...
4748      *
4749      * Now we create a new BDS B which we want to put on top of this
4750      * chain, so we first attach A as its backing node:
4751      *
4752      *                   node B
4753      *                     |
4754      *                     v
4755      *   guest device -> node A -> further backing chain...
4756      *
4757      * Finally we want to replace A by B.  When doing that, we want to
4758      * replace all pointers to A by pointers to B -- except for the
4759      * pointer from B because (1) that would create a loop, and (2)
4760      * that pointer should simply stay intact:
4761      *
4762      *   guest device -> node B
4763      *                     |
4764      *                     v
4765      *                   node A -> further backing chain...
4766      *
4767      * In general, when replacing a node A (c->bs) by a node B (@to),
4768      * if A is a child of B, that means we cannot replace A by B there
4769      * because that would create a loop.  Silently detaching A from B
4770      * is also not really an option.  So overall just leaving A in
4771      * place there is the most sensible choice.
4772      *
4773      * We would also create a loop in any cases where @c is only
4774      * indirectly referenced by @to. Prevent this by returning false
4775      * if @c is found (by breadth-first search) anywhere in the whole
4776      * subtree of @to.
4777      */
4778 
4779     ret = true;
4780     found = g_hash_table_new(NULL, NULL);
4781     g_hash_table_add(found, to);
4782     queue = g_queue_new();
4783     g_queue_push_tail(queue, to);
4784 
4785     while (!g_queue_is_empty(queue)) {
4786         BlockDriverState *v = g_queue_pop_head(queue);
4787         BdrvChild *c2;
4788 
4789         QLIST_FOREACH(c2, &v->children, next) {
4790             if (c2 == c) {
4791                 ret = false;
4792                 break;
4793             }
4794 
4795             if (g_hash_table_contains(found, c2->bs)) {
4796                 continue;
4797             }
4798 
4799             g_queue_push_tail(queue, c2->bs);
4800             g_hash_table_add(found, c2->bs);
4801         }
4802     }
4803 
4804     g_queue_free(queue);
4805     g_hash_table_destroy(found);
4806 
4807     return ret;
4808 }
4809 
4810 typedef struct BdrvRemoveFilterOrCowChild {
4811     BdrvChild *child;
4812     bool is_backing;
4813 } BdrvRemoveFilterOrCowChild;
4814 
4815 static void bdrv_remove_filter_or_cow_child_abort(void *opaque)
4816 {
4817     BdrvRemoveFilterOrCowChild *s = opaque;
4818     BlockDriverState *parent_bs = s->child->opaque;
4819 
4820     QLIST_INSERT_HEAD(&parent_bs->children, s->child, next);
4821     if (s->is_backing) {
4822         parent_bs->backing = s->child;
4823     } else {
4824         parent_bs->file = s->child;
4825     }
4826 
4827     /*
4828      * We don't have to restore child->bs here to undo bdrv_replace_child_tran()
4829      * because that function is transactionable and it registered own completion
4830      * entries in @tran, so .abort() for bdrv_replace_child_safe() will be
4831      * called automatically.
4832      */
4833 }
4834 
4835 static void bdrv_remove_filter_or_cow_child_commit(void *opaque)
4836 {
4837     BdrvRemoveFilterOrCowChild *s = opaque;
4838 
4839     bdrv_child_free(s->child);
4840 }
4841 
4842 static TransactionActionDrv bdrv_remove_filter_or_cow_child_drv = {
4843     .abort = bdrv_remove_filter_or_cow_child_abort,
4844     .commit = bdrv_remove_filter_or_cow_child_commit,
4845     .clean = g_free,
4846 };
4847 
4848 /*
4849  * A function to remove backing or file child of @bs.
4850  * Function doesn't update permissions, caller is responsible for this.
4851  */
4852 static void bdrv_remove_file_or_backing_child(BlockDriverState *bs,
4853                                               BdrvChild *child,
4854                                               Transaction *tran)
4855 {
4856     BdrvRemoveFilterOrCowChild *s;
4857 
4858     assert(child == bs->backing || child == bs->file);
4859 
4860     if (!child) {
4861         return;
4862     }
4863 
4864     if (child->bs) {
4865         bdrv_replace_child_tran(child, NULL, tran);
4866     }
4867 
4868     s = g_new(BdrvRemoveFilterOrCowChild, 1);
4869     *s = (BdrvRemoveFilterOrCowChild) {
4870         .child = child,
4871         .is_backing = (child == bs->backing),
4872     };
4873     tran_add(tran, &bdrv_remove_filter_or_cow_child_drv, s);
4874 
4875     QLIST_SAFE_REMOVE(child, next);
4876     if (s->is_backing) {
4877         bs->backing = NULL;
4878     } else {
4879         bs->file = NULL;
4880     }
4881 }
4882 
4883 /*
4884  * A function to remove backing-chain child of @bs if exists: cow child for
4885  * format nodes (always .backing) and filter child for filters (may be .file or
4886  * .backing)
4887  */
4888 static void bdrv_remove_filter_or_cow_child(BlockDriverState *bs,
4889                                             Transaction *tran)
4890 {
4891     bdrv_remove_file_or_backing_child(bs, bdrv_filter_or_cow_child(bs), tran);
4892 }
4893 
4894 static int bdrv_replace_node_noperm(BlockDriverState *from,
4895                                     BlockDriverState *to,
4896                                     bool auto_skip, Transaction *tran,
4897                                     Error **errp)
4898 {
4899     BdrvChild *c, *next;
4900 
4901     QLIST_FOREACH_SAFE(c, &from->parents, next_parent, next) {
4902         assert(c->bs == from);
4903         if (!should_update_child(c, to)) {
4904             if (auto_skip) {
4905                 continue;
4906             }
4907             error_setg(errp, "Should not change '%s' link to '%s'",
4908                        c->name, from->node_name);
4909             return -EINVAL;
4910         }
4911         if (c->frozen) {
4912             error_setg(errp, "Cannot change '%s' link to '%s'",
4913                        c->name, from->node_name);
4914             return -EPERM;
4915         }
4916         bdrv_replace_child_tran(c, to, tran);
4917     }
4918 
4919     return 0;
4920 }
4921 
4922 /*
4923  * With auto_skip=true bdrv_replace_node_common skips updating from parents
4924  * if it creates a parent-child relation loop or if parent is block-job.
4925  *
4926  * With auto_skip=false the error is returned if from has a parent which should
4927  * not be updated.
4928  *
4929  * With @detach_subchain=true @to must be in a backing chain of @from. In this
4930  * case backing link of the cow-parent of @to is removed.
4931  */
4932 static int bdrv_replace_node_common(BlockDriverState *from,
4933                                     BlockDriverState *to,
4934                                     bool auto_skip, bool detach_subchain,
4935                                     Error **errp)
4936 {
4937     Transaction *tran = tran_new();
4938     g_autoptr(GHashTable) found = NULL;
4939     g_autoptr(GSList) refresh_list = NULL;
4940     BlockDriverState *to_cow_parent = NULL;
4941     int ret;
4942 
4943     if (detach_subchain) {
4944         assert(bdrv_chain_contains(from, to));
4945         assert(from != to);
4946         for (to_cow_parent = from;
4947              bdrv_filter_or_cow_bs(to_cow_parent) != to;
4948              to_cow_parent = bdrv_filter_or_cow_bs(to_cow_parent))
4949         {
4950             ;
4951         }
4952     }
4953 
4954     /* Make sure that @from doesn't go away until we have successfully attached
4955      * all of its parents to @to. */
4956     bdrv_ref(from);
4957 
4958     assert(qemu_get_current_aio_context() == qemu_get_aio_context());
4959     assert(bdrv_get_aio_context(from) == bdrv_get_aio_context(to));
4960     bdrv_drained_begin(from);
4961 
4962     /*
4963      * Do the replacement without permission update.
4964      * Replacement may influence the permissions, we should calculate new
4965      * permissions based on new graph. If we fail, we'll roll-back the
4966      * replacement.
4967      */
4968     ret = bdrv_replace_node_noperm(from, to, auto_skip, tran, errp);
4969     if (ret < 0) {
4970         goto out;
4971     }
4972 
4973     if (detach_subchain) {
4974         bdrv_remove_filter_or_cow_child(to_cow_parent, tran);
4975     }
4976 
4977     found = g_hash_table_new(NULL, NULL);
4978 
4979     refresh_list = bdrv_topological_dfs(refresh_list, found, to);
4980     refresh_list = bdrv_topological_dfs(refresh_list, found, from);
4981 
4982     ret = bdrv_list_refresh_perms(refresh_list, NULL, tran, errp);
4983     if (ret < 0) {
4984         goto out;
4985     }
4986 
4987     ret = 0;
4988 
4989 out:
4990     tran_finalize(tran, ret);
4991 
4992     bdrv_drained_end(from);
4993     bdrv_unref(from);
4994 
4995     return ret;
4996 }
4997 
4998 int bdrv_replace_node(BlockDriverState *from, BlockDriverState *to,
4999                       Error **errp)
5000 {
5001     return bdrv_replace_node_common(from, to, true, false, errp);
5002 }
5003 
5004 int bdrv_drop_filter(BlockDriverState *bs, Error **errp)
5005 {
5006     return bdrv_replace_node_common(bs, bdrv_filter_or_cow_bs(bs), true, true,
5007                                     errp);
5008 }
5009 
5010 /*
5011  * Add new bs contents at the top of an image chain while the chain is
5012  * live, while keeping required fields on the top layer.
5013  *
5014  * This will modify the BlockDriverState fields, and swap contents
5015  * between bs_new and bs_top. Both bs_new and bs_top are modified.
5016  *
5017  * bs_new must not be attached to a BlockBackend and must not have backing
5018  * child.
5019  *
5020  * This function does not create any image files.
5021  */
5022 int bdrv_append(BlockDriverState *bs_new, BlockDriverState *bs_top,
5023                 Error **errp)
5024 {
5025     int ret;
5026     Transaction *tran = tran_new();
5027 
5028     assert(!bs_new->backing);
5029 
5030     ret = bdrv_attach_child_noperm(bs_new, bs_top, "backing",
5031                                    &child_of_bds, bdrv_backing_role(bs_new),
5032                                    &bs_new->backing, tran, errp);
5033     if (ret < 0) {
5034         goto out;
5035     }
5036 
5037     ret = bdrv_replace_node_noperm(bs_top, bs_new, true, tran, errp);
5038     if (ret < 0) {
5039         goto out;
5040     }
5041 
5042     ret = bdrv_refresh_perms(bs_new, errp);
5043 out:
5044     tran_finalize(tran, ret);
5045 
5046     bdrv_refresh_limits(bs_top, NULL, NULL);
5047 
5048     return ret;
5049 }
5050 
5051 static void bdrv_delete(BlockDriverState *bs)
5052 {
5053     assert(bdrv_op_blocker_is_empty(bs));
5054     assert(!bs->refcnt);
5055 
5056     /* remove from list, if necessary */
5057     if (bs->node_name[0] != '\0') {
5058         QTAILQ_REMOVE(&graph_bdrv_states, bs, node_list);
5059     }
5060     QTAILQ_REMOVE(&all_bdrv_states, bs, bs_list);
5061 
5062     bdrv_close(bs);
5063 
5064     g_free(bs);
5065 }
5066 
5067 BlockDriverState *bdrv_insert_node(BlockDriverState *bs, QDict *node_options,
5068                                    int flags, Error **errp)
5069 {
5070     BlockDriverState *new_node_bs;
5071     Error *local_err = NULL;
5072 
5073     new_node_bs = bdrv_open(NULL, NULL, node_options, flags, errp);
5074     if (new_node_bs == NULL) {
5075         error_prepend(errp, "Could not create node: ");
5076         return NULL;
5077     }
5078 
5079     bdrv_drained_begin(bs);
5080     bdrv_replace_node(bs, new_node_bs, &local_err);
5081     bdrv_drained_end(bs);
5082 
5083     if (local_err) {
5084         bdrv_unref(new_node_bs);
5085         error_propagate(errp, local_err);
5086         return NULL;
5087     }
5088 
5089     return new_node_bs;
5090 }
5091 
5092 /*
5093  * Run consistency checks on an image
5094  *
5095  * Returns 0 if the check could be completed (it doesn't mean that the image is
5096  * free of errors) or -errno when an internal error occurred. The results of the
5097  * check are stored in res.
5098  */
5099 int coroutine_fn bdrv_co_check(BlockDriverState *bs,
5100                                BdrvCheckResult *res, BdrvCheckMode fix)
5101 {
5102     if (bs->drv == NULL) {
5103         return -ENOMEDIUM;
5104     }
5105     if (bs->drv->bdrv_co_check == NULL) {
5106         return -ENOTSUP;
5107     }
5108 
5109     memset(res, 0, sizeof(*res));
5110     return bs->drv->bdrv_co_check(bs, res, fix);
5111 }
5112 
5113 /*
5114  * Return values:
5115  * 0        - success
5116  * -EINVAL  - backing format specified, but no file
5117  * -ENOSPC  - can't update the backing file because no space is left in the
5118  *            image file header
5119  * -ENOTSUP - format driver doesn't support changing the backing file
5120  */
5121 int bdrv_change_backing_file(BlockDriverState *bs, const char *backing_file,
5122                              const char *backing_fmt, bool require)
5123 {
5124     BlockDriver *drv = bs->drv;
5125     int ret;
5126 
5127     if (!drv) {
5128         return -ENOMEDIUM;
5129     }
5130 
5131     /* Backing file format doesn't make sense without a backing file */
5132     if (backing_fmt && !backing_file) {
5133         return -EINVAL;
5134     }
5135 
5136     if (require && backing_file && !backing_fmt) {
5137         return -EINVAL;
5138     }
5139 
5140     if (drv->bdrv_change_backing_file != NULL) {
5141         ret = drv->bdrv_change_backing_file(bs, backing_file, backing_fmt);
5142     } else {
5143         ret = -ENOTSUP;
5144     }
5145 
5146     if (ret == 0) {
5147         pstrcpy(bs->backing_file, sizeof(bs->backing_file), backing_file ?: "");
5148         pstrcpy(bs->backing_format, sizeof(bs->backing_format), backing_fmt ?: "");
5149         pstrcpy(bs->auto_backing_file, sizeof(bs->auto_backing_file),
5150                 backing_file ?: "");
5151     }
5152     return ret;
5153 }
5154 
5155 /*
5156  * Finds the first non-filter node above bs in the chain between
5157  * active and bs.  The returned node is either an immediate parent of
5158  * bs, or there are only filter nodes between the two.
5159  *
5160  * Returns NULL if bs is not found in active's image chain,
5161  * or if active == bs.
5162  *
5163  * Returns the bottommost base image if bs == NULL.
5164  */
5165 BlockDriverState *bdrv_find_overlay(BlockDriverState *active,
5166                                     BlockDriverState *bs)
5167 {
5168     bs = bdrv_skip_filters(bs);
5169     active = bdrv_skip_filters(active);
5170 
5171     while (active) {
5172         BlockDriverState *next = bdrv_backing_chain_next(active);
5173         if (bs == next) {
5174             return active;
5175         }
5176         active = next;
5177     }
5178 
5179     return NULL;
5180 }
5181 
5182 /* Given a BDS, searches for the base layer. */
5183 BlockDriverState *bdrv_find_base(BlockDriverState *bs)
5184 {
5185     return bdrv_find_overlay(bs, NULL);
5186 }
5187 
5188 /*
5189  * Return true if at least one of the COW (backing) and filter links
5190  * between @bs and @base is frozen. @errp is set if that's the case.
5191  * @base must be reachable from @bs, or NULL.
5192  */
5193 bool bdrv_is_backing_chain_frozen(BlockDriverState *bs, BlockDriverState *base,
5194                                   Error **errp)
5195 {
5196     BlockDriverState *i;
5197     BdrvChild *child;
5198 
5199     for (i = bs; i != base; i = child_bs(child)) {
5200         child = bdrv_filter_or_cow_child(i);
5201 
5202         if (child && child->frozen) {
5203             error_setg(errp, "Cannot change '%s' link from '%s' to '%s'",
5204                        child->name, i->node_name, child->bs->node_name);
5205             return true;
5206         }
5207     }
5208 
5209     return false;
5210 }
5211 
5212 /*
5213  * Freeze all COW (backing) and filter links between @bs and @base.
5214  * If any of the links is already frozen the operation is aborted and
5215  * none of the links are modified.
5216  * @base must be reachable from @bs, or NULL.
5217  * Returns 0 on success. On failure returns < 0 and sets @errp.
5218  */
5219 int bdrv_freeze_backing_chain(BlockDriverState *bs, BlockDriverState *base,
5220                               Error **errp)
5221 {
5222     BlockDriverState *i;
5223     BdrvChild *child;
5224 
5225     if (bdrv_is_backing_chain_frozen(bs, base, errp)) {
5226         return -EPERM;
5227     }
5228 
5229     for (i = bs; i != base; i = child_bs(child)) {
5230         child = bdrv_filter_or_cow_child(i);
5231         if (child && child->bs->never_freeze) {
5232             error_setg(errp, "Cannot freeze '%s' link to '%s'",
5233                        child->name, child->bs->node_name);
5234             return -EPERM;
5235         }
5236     }
5237 
5238     for (i = bs; i != base; i = child_bs(child)) {
5239         child = bdrv_filter_or_cow_child(i);
5240         if (child) {
5241             child->frozen = true;
5242         }
5243     }
5244 
5245     return 0;
5246 }
5247 
5248 /*
5249  * Unfreeze all COW (backing) and filter links between @bs and @base.
5250  * The caller must ensure that all links are frozen before using this
5251  * function.
5252  * @base must be reachable from @bs, or NULL.
5253  */
5254 void bdrv_unfreeze_backing_chain(BlockDriverState *bs, BlockDriverState *base)
5255 {
5256     BlockDriverState *i;
5257     BdrvChild *child;
5258 
5259     for (i = bs; i != base; i = child_bs(child)) {
5260         child = bdrv_filter_or_cow_child(i);
5261         if (child) {
5262             assert(child->frozen);
5263             child->frozen = false;
5264         }
5265     }
5266 }
5267 
5268 /*
5269  * Drops images above 'base' up to and including 'top', and sets the image
5270  * above 'top' to have base as its backing file.
5271  *
5272  * Requires that the overlay to 'top' is opened r/w, so that the backing file
5273  * information in 'bs' can be properly updated.
5274  *
5275  * E.g., this will convert the following chain:
5276  * bottom <- base <- intermediate <- top <- active
5277  *
5278  * to
5279  *
5280  * bottom <- base <- active
5281  *
5282  * It is allowed for bottom==base, in which case it converts:
5283  *
5284  * base <- intermediate <- top <- active
5285  *
5286  * to
5287  *
5288  * base <- active
5289  *
5290  * If backing_file_str is non-NULL, it will be used when modifying top's
5291  * overlay image metadata.
5292  *
5293  * Error conditions:
5294  *  if active == top, that is considered an error
5295  *
5296  */
5297 int bdrv_drop_intermediate(BlockDriverState *top, BlockDriverState *base,
5298                            const char *backing_file_str)
5299 {
5300     BlockDriverState *explicit_top = top;
5301     bool update_inherits_from;
5302     BdrvChild *c;
5303     Error *local_err = NULL;
5304     int ret = -EIO;
5305     g_autoptr(GSList) updated_children = NULL;
5306     GSList *p;
5307 
5308     bdrv_ref(top);
5309     bdrv_subtree_drained_begin(top);
5310 
5311     if (!top->drv || !base->drv) {
5312         goto exit;
5313     }
5314 
5315     /* Make sure that base is in the backing chain of top */
5316     if (!bdrv_chain_contains(top, base)) {
5317         goto exit;
5318     }
5319 
5320     /* If 'base' recursively inherits from 'top' then we should set
5321      * base->inherits_from to top->inherits_from after 'top' and all
5322      * other intermediate nodes have been dropped.
5323      * If 'top' is an implicit node (e.g. "commit_top") we should skip
5324      * it because no one inherits from it. We use explicit_top for that. */
5325     explicit_top = bdrv_skip_implicit_filters(explicit_top);
5326     update_inherits_from = bdrv_inherits_from_recursive(base, explicit_top);
5327 
5328     /* success - we can delete the intermediate states, and link top->base */
5329     /* TODO Check graph modification op blockers (BLK_PERM_GRAPH_MOD) once
5330      * we've figured out how they should work. */
5331     if (!backing_file_str) {
5332         bdrv_refresh_filename(base);
5333         backing_file_str = base->filename;
5334     }
5335 
5336     QLIST_FOREACH(c, &top->parents, next_parent) {
5337         updated_children = g_slist_prepend(updated_children, c);
5338     }
5339 
5340     /*
5341      * It seems correct to pass detach_subchain=true here, but it triggers
5342      * one more yet not fixed bug, when due to nested aio_poll loop we switch to
5343      * another drained section, which modify the graph (for example, removing
5344      * the child, which we keep in updated_children list). So, it's a TODO.
5345      *
5346      * Note, bug triggered if pass detach_subchain=true here and run
5347      * test-bdrv-drain. test_drop_intermediate_poll() test-case will crash.
5348      * That's a FIXME.
5349      */
5350     bdrv_replace_node_common(top, base, false, false, &local_err);
5351     if (local_err) {
5352         error_report_err(local_err);
5353         goto exit;
5354     }
5355 
5356     for (p = updated_children; p; p = p->next) {
5357         c = p->data;
5358 
5359         if (c->klass->update_filename) {
5360             ret = c->klass->update_filename(c, base, backing_file_str,
5361                                             &local_err);
5362             if (ret < 0) {
5363                 /*
5364                  * TODO: Actually, we want to rollback all previous iterations
5365                  * of this loop, and (which is almost impossible) previous
5366                  * bdrv_replace_node()...
5367                  *
5368                  * Note, that c->klass->update_filename may lead to permission
5369                  * update, so it's a bad idea to call it inside permission
5370                  * update transaction of bdrv_replace_node.
5371                  */
5372                 error_report_err(local_err);
5373                 goto exit;
5374             }
5375         }
5376     }
5377 
5378     if (update_inherits_from) {
5379         base->inherits_from = explicit_top->inherits_from;
5380     }
5381 
5382     ret = 0;
5383 exit:
5384     bdrv_subtree_drained_end(top);
5385     bdrv_unref(top);
5386     return ret;
5387 }
5388 
5389 /**
5390  * Implementation of BlockDriver.bdrv_get_allocated_file_size() that
5391  * sums the size of all data-bearing children.  (This excludes backing
5392  * children.)
5393  */
5394 static int64_t bdrv_sum_allocated_file_size(BlockDriverState *bs)
5395 {
5396     BdrvChild *child;
5397     int64_t child_size, sum = 0;
5398 
5399     QLIST_FOREACH(child, &bs->children, next) {
5400         if (child->role & (BDRV_CHILD_DATA | BDRV_CHILD_METADATA |
5401                            BDRV_CHILD_FILTERED))
5402         {
5403             child_size = bdrv_get_allocated_file_size(child->bs);
5404             if (child_size < 0) {
5405                 return child_size;
5406             }
5407             sum += child_size;
5408         }
5409     }
5410 
5411     return sum;
5412 }
5413 
5414 /**
5415  * Length of a allocated file in bytes. Sparse files are counted by actual
5416  * allocated space. Return < 0 if error or unknown.
5417  */
5418 int64_t bdrv_get_allocated_file_size(BlockDriverState *bs)
5419 {
5420     BlockDriver *drv = bs->drv;
5421     if (!drv) {
5422         return -ENOMEDIUM;
5423     }
5424     if (drv->bdrv_get_allocated_file_size) {
5425         return drv->bdrv_get_allocated_file_size(bs);
5426     }
5427 
5428     if (drv->bdrv_file_open) {
5429         /*
5430          * Protocol drivers default to -ENOTSUP (most of their data is
5431          * not stored in any of their children (if they even have any),
5432          * so there is no generic way to figure it out).
5433          */
5434         return -ENOTSUP;
5435     } else if (drv->is_filter) {
5436         /* Filter drivers default to the size of their filtered child */
5437         return bdrv_get_allocated_file_size(bdrv_filter_bs(bs));
5438     } else {
5439         /* Other drivers default to summing their children's sizes */
5440         return bdrv_sum_allocated_file_size(bs);
5441     }
5442 }
5443 
5444 /*
5445  * bdrv_measure:
5446  * @drv: Format driver
5447  * @opts: Creation options for new image
5448  * @in_bs: Existing image containing data for new image (may be NULL)
5449  * @errp: Error object
5450  * Returns: A #BlockMeasureInfo (free using qapi_free_BlockMeasureInfo())
5451  *          or NULL on error
5452  *
5453  * Calculate file size required to create a new image.
5454  *
5455  * If @in_bs is given then space for allocated clusters and zero clusters
5456  * from that image are included in the calculation.  If @opts contains a
5457  * backing file that is shared by @in_bs then backing clusters may be omitted
5458  * from the calculation.
5459  *
5460  * If @in_bs is NULL then the calculation includes no allocated clusters
5461  * unless a preallocation option is given in @opts.
5462  *
5463  * Note that @in_bs may use a different BlockDriver from @drv.
5464  *
5465  * If an error occurs the @errp pointer is set.
5466  */
5467 BlockMeasureInfo *bdrv_measure(BlockDriver *drv, QemuOpts *opts,
5468                                BlockDriverState *in_bs, Error **errp)
5469 {
5470     if (!drv->bdrv_measure) {
5471         error_setg(errp, "Block driver '%s' does not support size measurement",
5472                    drv->format_name);
5473         return NULL;
5474     }
5475 
5476     return drv->bdrv_measure(opts, in_bs, errp);
5477 }
5478 
5479 /**
5480  * Return number of sectors on success, -errno on error.
5481  */
5482 int64_t bdrv_nb_sectors(BlockDriverState *bs)
5483 {
5484     BlockDriver *drv = bs->drv;
5485 
5486     if (!drv)
5487         return -ENOMEDIUM;
5488 
5489     if (drv->has_variable_length) {
5490         int ret = refresh_total_sectors(bs, bs->total_sectors);
5491         if (ret < 0) {
5492             return ret;
5493         }
5494     }
5495     return bs->total_sectors;
5496 }
5497 
5498 /**
5499  * Return length in bytes on success, -errno on error.
5500  * The length is always a multiple of BDRV_SECTOR_SIZE.
5501  */
5502 int64_t bdrv_getlength(BlockDriverState *bs)
5503 {
5504     int64_t ret = bdrv_nb_sectors(bs);
5505 
5506     if (ret < 0) {
5507         return ret;
5508     }
5509     if (ret > INT64_MAX / BDRV_SECTOR_SIZE) {
5510         return -EFBIG;
5511     }
5512     return ret * BDRV_SECTOR_SIZE;
5513 }
5514 
5515 /* return 0 as number of sectors if no device present or error */
5516 void bdrv_get_geometry(BlockDriverState *bs, uint64_t *nb_sectors_ptr)
5517 {
5518     int64_t nb_sectors = bdrv_nb_sectors(bs);
5519 
5520     *nb_sectors_ptr = nb_sectors < 0 ? 0 : nb_sectors;
5521 }
5522 
5523 bool bdrv_is_sg(BlockDriverState *bs)
5524 {
5525     return bs->sg;
5526 }
5527 
5528 /**
5529  * Return whether the given node supports compressed writes.
5530  */
5531 bool bdrv_supports_compressed_writes(BlockDriverState *bs)
5532 {
5533     BlockDriverState *filtered;
5534 
5535     if (!bs->drv || !block_driver_can_compress(bs->drv)) {
5536         return false;
5537     }
5538 
5539     filtered = bdrv_filter_bs(bs);
5540     if (filtered) {
5541         /*
5542          * Filters can only forward compressed writes, so we have to
5543          * check the child.
5544          */
5545         return bdrv_supports_compressed_writes(filtered);
5546     }
5547 
5548     return true;
5549 }
5550 
5551 const char *bdrv_get_format_name(BlockDriverState *bs)
5552 {
5553     return bs->drv ? bs->drv->format_name : NULL;
5554 }
5555 
5556 static int qsort_strcmp(const void *a, const void *b)
5557 {
5558     return strcmp(*(char *const *)a, *(char *const *)b);
5559 }
5560 
5561 void bdrv_iterate_format(void (*it)(void *opaque, const char *name),
5562                          void *opaque, bool read_only)
5563 {
5564     BlockDriver *drv;
5565     int count = 0;
5566     int i;
5567     const char **formats = NULL;
5568 
5569     QLIST_FOREACH(drv, &bdrv_drivers, list) {
5570         if (drv->format_name) {
5571             bool found = false;
5572             int i = count;
5573 
5574             if (use_bdrv_whitelist && !bdrv_is_whitelisted(drv, read_only)) {
5575                 continue;
5576             }
5577 
5578             while (formats && i && !found) {
5579                 found = !strcmp(formats[--i], drv->format_name);
5580             }
5581 
5582             if (!found) {
5583                 formats = g_renew(const char *, formats, count + 1);
5584                 formats[count++] = drv->format_name;
5585             }
5586         }
5587     }
5588 
5589     for (i = 0; i < (int)ARRAY_SIZE(block_driver_modules); i++) {
5590         const char *format_name = block_driver_modules[i].format_name;
5591 
5592         if (format_name) {
5593             bool found = false;
5594             int j = count;
5595 
5596             if (use_bdrv_whitelist &&
5597                 !bdrv_format_is_whitelisted(format_name, read_only)) {
5598                 continue;
5599             }
5600 
5601             while (formats && j && !found) {
5602                 found = !strcmp(formats[--j], format_name);
5603             }
5604 
5605             if (!found) {
5606                 formats = g_renew(const char *, formats, count + 1);
5607                 formats[count++] = format_name;
5608             }
5609         }
5610     }
5611 
5612     qsort(formats, count, sizeof(formats[0]), qsort_strcmp);
5613 
5614     for (i = 0; i < count; i++) {
5615         it(opaque, formats[i]);
5616     }
5617 
5618     g_free(formats);
5619 }
5620 
5621 /* This function is to find a node in the bs graph */
5622 BlockDriverState *bdrv_find_node(const char *node_name)
5623 {
5624     BlockDriverState *bs;
5625 
5626     assert(node_name);
5627 
5628     QTAILQ_FOREACH(bs, &graph_bdrv_states, node_list) {
5629         if (!strcmp(node_name, bs->node_name)) {
5630             return bs;
5631         }
5632     }
5633     return NULL;
5634 }
5635 
5636 /* Put this QMP function here so it can access the static graph_bdrv_states. */
5637 BlockDeviceInfoList *bdrv_named_nodes_list(bool flat,
5638                                            Error **errp)
5639 {
5640     BlockDeviceInfoList *list;
5641     BlockDriverState *bs;
5642 
5643     list = NULL;
5644     QTAILQ_FOREACH(bs, &graph_bdrv_states, node_list) {
5645         BlockDeviceInfo *info = bdrv_block_device_info(NULL, bs, flat, errp);
5646         if (!info) {
5647             qapi_free_BlockDeviceInfoList(list);
5648             return NULL;
5649         }
5650         QAPI_LIST_PREPEND(list, info);
5651     }
5652 
5653     return list;
5654 }
5655 
5656 typedef struct XDbgBlockGraphConstructor {
5657     XDbgBlockGraph *graph;
5658     GHashTable *graph_nodes;
5659 } XDbgBlockGraphConstructor;
5660 
5661 static XDbgBlockGraphConstructor *xdbg_graph_new(void)
5662 {
5663     XDbgBlockGraphConstructor *gr = g_new(XDbgBlockGraphConstructor, 1);
5664 
5665     gr->graph = g_new0(XDbgBlockGraph, 1);
5666     gr->graph_nodes = g_hash_table_new(NULL, NULL);
5667 
5668     return gr;
5669 }
5670 
5671 static XDbgBlockGraph *xdbg_graph_finalize(XDbgBlockGraphConstructor *gr)
5672 {
5673     XDbgBlockGraph *graph = gr->graph;
5674 
5675     g_hash_table_destroy(gr->graph_nodes);
5676     g_free(gr);
5677 
5678     return graph;
5679 }
5680 
5681 static uintptr_t xdbg_graph_node_num(XDbgBlockGraphConstructor *gr, void *node)
5682 {
5683     uintptr_t ret = (uintptr_t)g_hash_table_lookup(gr->graph_nodes, node);
5684 
5685     if (ret != 0) {
5686         return ret;
5687     }
5688 
5689     /*
5690      * Start counting from 1, not 0, because 0 interferes with not-found (NULL)
5691      * answer of g_hash_table_lookup.
5692      */
5693     ret = g_hash_table_size(gr->graph_nodes) + 1;
5694     g_hash_table_insert(gr->graph_nodes, node, (void *)ret);
5695 
5696     return ret;
5697 }
5698 
5699 static void xdbg_graph_add_node(XDbgBlockGraphConstructor *gr, void *node,
5700                                 XDbgBlockGraphNodeType type, const char *name)
5701 {
5702     XDbgBlockGraphNode *n;
5703 
5704     n = g_new0(XDbgBlockGraphNode, 1);
5705 
5706     n->id = xdbg_graph_node_num(gr, node);
5707     n->type = type;
5708     n->name = g_strdup(name);
5709 
5710     QAPI_LIST_PREPEND(gr->graph->nodes, n);
5711 }
5712 
5713 static void xdbg_graph_add_edge(XDbgBlockGraphConstructor *gr, void *parent,
5714                                 const BdrvChild *child)
5715 {
5716     BlockPermission qapi_perm;
5717     XDbgBlockGraphEdge *edge;
5718 
5719     edge = g_new0(XDbgBlockGraphEdge, 1);
5720 
5721     edge->parent = xdbg_graph_node_num(gr, parent);
5722     edge->child = xdbg_graph_node_num(gr, child->bs);
5723     edge->name = g_strdup(child->name);
5724 
5725     for (qapi_perm = 0; qapi_perm < BLOCK_PERMISSION__MAX; qapi_perm++) {
5726         uint64_t flag = bdrv_qapi_perm_to_blk_perm(qapi_perm);
5727 
5728         if (flag & child->perm) {
5729             QAPI_LIST_PREPEND(edge->perm, qapi_perm);
5730         }
5731         if (flag & child->shared_perm) {
5732             QAPI_LIST_PREPEND(edge->shared_perm, qapi_perm);
5733         }
5734     }
5735 
5736     QAPI_LIST_PREPEND(gr->graph->edges, edge);
5737 }
5738 
5739 
5740 XDbgBlockGraph *bdrv_get_xdbg_block_graph(Error **errp)
5741 {
5742     BlockBackend *blk;
5743     BlockJob *job;
5744     BlockDriverState *bs;
5745     BdrvChild *child;
5746     XDbgBlockGraphConstructor *gr = xdbg_graph_new();
5747 
5748     for (blk = blk_all_next(NULL); blk; blk = blk_all_next(blk)) {
5749         char *allocated_name = NULL;
5750         const char *name = blk_name(blk);
5751 
5752         if (!*name) {
5753             name = allocated_name = blk_get_attached_dev_id(blk);
5754         }
5755         xdbg_graph_add_node(gr, blk, X_DBG_BLOCK_GRAPH_NODE_TYPE_BLOCK_BACKEND,
5756                            name);
5757         g_free(allocated_name);
5758         if (blk_root(blk)) {
5759             xdbg_graph_add_edge(gr, blk, blk_root(blk));
5760         }
5761     }
5762 
5763     for (job = block_job_next(NULL); job; job = block_job_next(job)) {
5764         GSList *el;
5765 
5766         xdbg_graph_add_node(gr, job, X_DBG_BLOCK_GRAPH_NODE_TYPE_BLOCK_JOB,
5767                            job->job.id);
5768         for (el = job->nodes; el; el = el->next) {
5769             xdbg_graph_add_edge(gr, job, (BdrvChild *)el->data);
5770         }
5771     }
5772 
5773     QTAILQ_FOREACH(bs, &graph_bdrv_states, node_list) {
5774         xdbg_graph_add_node(gr, bs, X_DBG_BLOCK_GRAPH_NODE_TYPE_BLOCK_DRIVER,
5775                            bs->node_name);
5776         QLIST_FOREACH(child, &bs->children, next) {
5777             xdbg_graph_add_edge(gr, bs, child);
5778         }
5779     }
5780 
5781     return xdbg_graph_finalize(gr);
5782 }
5783 
5784 BlockDriverState *bdrv_lookup_bs(const char *device,
5785                                  const char *node_name,
5786                                  Error **errp)
5787 {
5788     BlockBackend *blk;
5789     BlockDriverState *bs;
5790 
5791     if (device) {
5792         blk = blk_by_name(device);
5793 
5794         if (blk) {
5795             bs = blk_bs(blk);
5796             if (!bs) {
5797                 error_setg(errp, "Device '%s' has no medium", device);
5798             }
5799 
5800             return bs;
5801         }
5802     }
5803 
5804     if (node_name) {
5805         bs = bdrv_find_node(node_name);
5806 
5807         if (bs) {
5808             return bs;
5809         }
5810     }
5811 
5812     error_setg(errp, "Cannot find device=\'%s\' nor node-name=\'%s\'",
5813                      device ? device : "",
5814                      node_name ? node_name : "");
5815     return NULL;
5816 }
5817 
5818 /* If 'base' is in the same chain as 'top', return true. Otherwise,
5819  * return false.  If either argument is NULL, return false. */
5820 bool bdrv_chain_contains(BlockDriverState *top, BlockDriverState *base)
5821 {
5822     while (top && top != base) {
5823         top = bdrv_filter_or_cow_bs(top);
5824     }
5825 
5826     return top != NULL;
5827 }
5828 
5829 BlockDriverState *bdrv_next_node(BlockDriverState *bs)
5830 {
5831     if (!bs) {
5832         return QTAILQ_FIRST(&graph_bdrv_states);
5833     }
5834     return QTAILQ_NEXT(bs, node_list);
5835 }
5836 
5837 BlockDriverState *bdrv_next_all_states(BlockDriverState *bs)
5838 {
5839     if (!bs) {
5840         return QTAILQ_FIRST(&all_bdrv_states);
5841     }
5842     return QTAILQ_NEXT(bs, bs_list);
5843 }
5844 
5845 const char *bdrv_get_node_name(const BlockDriverState *bs)
5846 {
5847     return bs->node_name;
5848 }
5849 
5850 const char *bdrv_get_parent_name(const BlockDriverState *bs)
5851 {
5852     BdrvChild *c;
5853     const char *name;
5854 
5855     /* If multiple parents have a name, just pick the first one. */
5856     QLIST_FOREACH(c, &bs->parents, next_parent) {
5857         if (c->klass->get_name) {
5858             name = c->klass->get_name(c);
5859             if (name && *name) {
5860                 return name;
5861             }
5862         }
5863     }
5864 
5865     return NULL;
5866 }
5867 
5868 /* TODO check what callers really want: bs->node_name or blk_name() */
5869 const char *bdrv_get_device_name(const BlockDriverState *bs)
5870 {
5871     return bdrv_get_parent_name(bs) ?: "";
5872 }
5873 
5874 /* This can be used to identify nodes that might not have a device
5875  * name associated. Since node and device names live in the same
5876  * namespace, the result is unambiguous. The exception is if both are
5877  * absent, then this returns an empty (non-null) string. */
5878 const char *bdrv_get_device_or_node_name(const BlockDriverState *bs)
5879 {
5880     return bdrv_get_parent_name(bs) ?: bs->node_name;
5881 }
5882 
5883 int bdrv_get_flags(BlockDriverState *bs)
5884 {
5885     return bs->open_flags;
5886 }
5887 
5888 int bdrv_has_zero_init_1(BlockDriverState *bs)
5889 {
5890     return 1;
5891 }
5892 
5893 int bdrv_has_zero_init(BlockDriverState *bs)
5894 {
5895     BlockDriverState *filtered;
5896 
5897     if (!bs->drv) {
5898         return 0;
5899     }
5900 
5901     /* If BS is a copy on write image, it is initialized to
5902        the contents of the base image, which may not be zeroes.  */
5903     if (bdrv_cow_child(bs)) {
5904         return 0;
5905     }
5906     if (bs->drv->bdrv_has_zero_init) {
5907         return bs->drv->bdrv_has_zero_init(bs);
5908     }
5909 
5910     filtered = bdrv_filter_bs(bs);
5911     if (filtered) {
5912         return bdrv_has_zero_init(filtered);
5913     }
5914 
5915     /* safe default */
5916     return 0;
5917 }
5918 
5919 bool bdrv_can_write_zeroes_with_unmap(BlockDriverState *bs)
5920 {
5921     if (!(bs->open_flags & BDRV_O_UNMAP)) {
5922         return false;
5923     }
5924 
5925     return bs->supported_zero_flags & BDRV_REQ_MAY_UNMAP;
5926 }
5927 
5928 void bdrv_get_backing_filename(BlockDriverState *bs,
5929                                char *filename, int filename_size)
5930 {
5931     pstrcpy(filename, filename_size, bs->backing_file);
5932 }
5933 
5934 int bdrv_get_info(BlockDriverState *bs, BlockDriverInfo *bdi)
5935 {
5936     int ret;
5937     BlockDriver *drv = bs->drv;
5938     /* if bs->drv == NULL, bs is closed, so there's nothing to do here */
5939     if (!drv) {
5940         return -ENOMEDIUM;
5941     }
5942     if (!drv->bdrv_get_info) {
5943         BlockDriverState *filtered = bdrv_filter_bs(bs);
5944         if (filtered) {
5945             return bdrv_get_info(filtered, bdi);
5946         }
5947         return -ENOTSUP;
5948     }
5949     memset(bdi, 0, sizeof(*bdi));
5950     ret = drv->bdrv_get_info(bs, bdi);
5951     if (ret < 0) {
5952         return ret;
5953     }
5954 
5955     if (bdi->cluster_size > BDRV_MAX_ALIGNMENT) {
5956         return -EINVAL;
5957     }
5958 
5959     return 0;
5960 }
5961 
5962 ImageInfoSpecific *bdrv_get_specific_info(BlockDriverState *bs,
5963                                           Error **errp)
5964 {
5965     BlockDriver *drv = bs->drv;
5966     if (drv && drv->bdrv_get_specific_info) {
5967         return drv->bdrv_get_specific_info(bs, errp);
5968     }
5969     return NULL;
5970 }
5971 
5972 BlockStatsSpecific *bdrv_get_specific_stats(BlockDriverState *bs)
5973 {
5974     BlockDriver *drv = bs->drv;
5975     if (!drv || !drv->bdrv_get_specific_stats) {
5976         return NULL;
5977     }
5978     return drv->bdrv_get_specific_stats(bs);
5979 }
5980 
5981 void bdrv_debug_event(BlockDriverState *bs, BlkdebugEvent event)
5982 {
5983     if (!bs || !bs->drv || !bs->drv->bdrv_debug_event) {
5984         return;
5985     }
5986 
5987     bs->drv->bdrv_debug_event(bs, event);
5988 }
5989 
5990 static BlockDriverState *bdrv_find_debug_node(BlockDriverState *bs)
5991 {
5992     while (bs && bs->drv && !bs->drv->bdrv_debug_breakpoint) {
5993         bs = bdrv_primary_bs(bs);
5994     }
5995 
5996     if (bs && bs->drv && bs->drv->bdrv_debug_breakpoint) {
5997         assert(bs->drv->bdrv_debug_remove_breakpoint);
5998         return bs;
5999     }
6000 
6001     return NULL;
6002 }
6003 
6004 int bdrv_debug_breakpoint(BlockDriverState *bs, const char *event,
6005                           const char *tag)
6006 {
6007     bs = bdrv_find_debug_node(bs);
6008     if (bs) {
6009         return bs->drv->bdrv_debug_breakpoint(bs, event, tag);
6010     }
6011 
6012     return -ENOTSUP;
6013 }
6014 
6015 int bdrv_debug_remove_breakpoint(BlockDriverState *bs, const char *tag)
6016 {
6017     bs = bdrv_find_debug_node(bs);
6018     if (bs) {
6019         return bs->drv->bdrv_debug_remove_breakpoint(bs, tag);
6020     }
6021 
6022     return -ENOTSUP;
6023 }
6024 
6025 int bdrv_debug_resume(BlockDriverState *bs, const char *tag)
6026 {
6027     while (bs && (!bs->drv || !bs->drv->bdrv_debug_resume)) {
6028         bs = bdrv_primary_bs(bs);
6029     }
6030 
6031     if (bs && bs->drv && bs->drv->bdrv_debug_resume) {
6032         return bs->drv->bdrv_debug_resume(bs, tag);
6033     }
6034 
6035     return -ENOTSUP;
6036 }
6037 
6038 bool bdrv_debug_is_suspended(BlockDriverState *bs, const char *tag)
6039 {
6040     while (bs && bs->drv && !bs->drv->bdrv_debug_is_suspended) {
6041         bs = bdrv_primary_bs(bs);
6042     }
6043 
6044     if (bs && bs->drv && bs->drv->bdrv_debug_is_suspended) {
6045         return bs->drv->bdrv_debug_is_suspended(bs, tag);
6046     }
6047 
6048     return false;
6049 }
6050 
6051 /* backing_file can either be relative, or absolute, or a protocol.  If it is
6052  * relative, it must be relative to the chain.  So, passing in bs->filename
6053  * from a BDS as backing_file should not be done, as that may be relative to
6054  * the CWD rather than the chain. */
6055 BlockDriverState *bdrv_find_backing_image(BlockDriverState *bs,
6056         const char *backing_file)
6057 {
6058     char *filename_full = NULL;
6059     char *backing_file_full = NULL;
6060     char *filename_tmp = NULL;
6061     int is_protocol = 0;
6062     bool filenames_refreshed = false;
6063     BlockDriverState *curr_bs = NULL;
6064     BlockDriverState *retval = NULL;
6065     BlockDriverState *bs_below;
6066 
6067     if (!bs || !bs->drv || !backing_file) {
6068         return NULL;
6069     }
6070 
6071     filename_full     = g_malloc(PATH_MAX);
6072     backing_file_full = g_malloc(PATH_MAX);
6073 
6074     is_protocol = path_has_protocol(backing_file);
6075 
6076     /*
6077      * Being largely a legacy function, skip any filters here
6078      * (because filters do not have normal filenames, so they cannot
6079      * match anyway; and allowing json:{} filenames is a bit out of
6080      * scope).
6081      */
6082     for (curr_bs = bdrv_skip_filters(bs);
6083          bdrv_cow_child(curr_bs) != NULL;
6084          curr_bs = bs_below)
6085     {
6086         bs_below = bdrv_backing_chain_next(curr_bs);
6087 
6088         if (bdrv_backing_overridden(curr_bs)) {
6089             /*
6090              * If the backing file was overridden, we can only compare
6091              * directly against the backing node's filename.
6092              */
6093 
6094             if (!filenames_refreshed) {
6095                 /*
6096                  * This will automatically refresh all of the
6097                  * filenames in the rest of the backing chain, so we
6098                  * only need to do this once.
6099                  */
6100                 bdrv_refresh_filename(bs_below);
6101                 filenames_refreshed = true;
6102             }
6103 
6104             if (strcmp(backing_file, bs_below->filename) == 0) {
6105                 retval = bs_below;
6106                 break;
6107             }
6108         } else if (is_protocol || path_has_protocol(curr_bs->backing_file)) {
6109             /*
6110              * If either of the filename paths is actually a protocol, then
6111              * compare unmodified paths; otherwise make paths relative.
6112              */
6113             char *backing_file_full_ret;
6114 
6115             if (strcmp(backing_file, curr_bs->backing_file) == 0) {
6116                 retval = bs_below;
6117                 break;
6118             }
6119             /* Also check against the full backing filename for the image */
6120             backing_file_full_ret = bdrv_get_full_backing_filename(curr_bs,
6121                                                                    NULL);
6122             if (backing_file_full_ret) {
6123                 bool equal = strcmp(backing_file, backing_file_full_ret) == 0;
6124                 g_free(backing_file_full_ret);
6125                 if (equal) {
6126                     retval = bs_below;
6127                     break;
6128                 }
6129             }
6130         } else {
6131             /* If not an absolute filename path, make it relative to the current
6132              * image's filename path */
6133             filename_tmp = bdrv_make_absolute_filename(curr_bs, backing_file,
6134                                                        NULL);
6135             /* We are going to compare canonicalized absolute pathnames */
6136             if (!filename_tmp || !realpath(filename_tmp, filename_full)) {
6137                 g_free(filename_tmp);
6138                 continue;
6139             }
6140             g_free(filename_tmp);
6141 
6142             /* We need to make sure the backing filename we are comparing against
6143              * is relative to the current image filename (or absolute) */
6144             filename_tmp = bdrv_get_full_backing_filename(curr_bs, NULL);
6145             if (!filename_tmp || !realpath(filename_tmp, backing_file_full)) {
6146                 g_free(filename_tmp);
6147                 continue;
6148             }
6149             g_free(filename_tmp);
6150 
6151             if (strcmp(backing_file_full, filename_full) == 0) {
6152                 retval = bs_below;
6153                 break;
6154             }
6155         }
6156     }
6157 
6158     g_free(filename_full);
6159     g_free(backing_file_full);
6160     return retval;
6161 }
6162 
6163 void bdrv_init(void)
6164 {
6165     module_call_init(MODULE_INIT_BLOCK);
6166 }
6167 
6168 void bdrv_init_with_whitelist(void)
6169 {
6170     use_bdrv_whitelist = 1;
6171     bdrv_init();
6172 }
6173 
6174 int coroutine_fn bdrv_co_invalidate_cache(BlockDriverState *bs, Error **errp)
6175 {
6176     BdrvChild *child, *parent;
6177     Error *local_err = NULL;
6178     int ret;
6179     BdrvDirtyBitmap *bm;
6180 
6181     if (!bs->drv)  {
6182         return -ENOMEDIUM;
6183     }
6184 
6185     QLIST_FOREACH(child, &bs->children, next) {
6186         bdrv_co_invalidate_cache(child->bs, &local_err);
6187         if (local_err) {
6188             error_propagate(errp, local_err);
6189             return -EINVAL;
6190         }
6191     }
6192 
6193     /*
6194      * Update permissions, they may differ for inactive nodes.
6195      *
6196      * Note that the required permissions of inactive images are always a
6197      * subset of the permissions required after activating the image. This
6198      * allows us to just get the permissions upfront without restricting
6199      * drv->bdrv_invalidate_cache().
6200      *
6201      * It also means that in error cases, we don't have to try and revert to
6202      * the old permissions (which is an operation that could fail, too). We can
6203      * just keep the extended permissions for the next time that an activation
6204      * of the image is tried.
6205      */
6206     if (bs->open_flags & BDRV_O_INACTIVE) {
6207         bs->open_flags &= ~BDRV_O_INACTIVE;
6208         ret = bdrv_refresh_perms(bs, errp);
6209         if (ret < 0) {
6210             bs->open_flags |= BDRV_O_INACTIVE;
6211             return ret;
6212         }
6213 
6214         if (bs->drv->bdrv_co_invalidate_cache) {
6215             bs->drv->bdrv_co_invalidate_cache(bs, &local_err);
6216             if (local_err) {
6217                 bs->open_flags |= BDRV_O_INACTIVE;
6218                 error_propagate(errp, local_err);
6219                 return -EINVAL;
6220             }
6221         }
6222 
6223         FOR_EACH_DIRTY_BITMAP(bs, bm) {
6224             bdrv_dirty_bitmap_skip_store(bm, false);
6225         }
6226 
6227         ret = refresh_total_sectors(bs, bs->total_sectors);
6228         if (ret < 0) {
6229             bs->open_flags |= BDRV_O_INACTIVE;
6230             error_setg_errno(errp, -ret, "Could not refresh total sector count");
6231             return ret;
6232         }
6233     }
6234 
6235     QLIST_FOREACH(parent, &bs->parents, next_parent) {
6236         if (parent->klass->activate) {
6237             parent->klass->activate(parent, &local_err);
6238             if (local_err) {
6239                 bs->open_flags |= BDRV_O_INACTIVE;
6240                 error_propagate(errp, local_err);
6241                 return -EINVAL;
6242             }
6243         }
6244     }
6245 
6246     return 0;
6247 }
6248 
6249 void bdrv_invalidate_cache_all(Error **errp)
6250 {
6251     BlockDriverState *bs;
6252     BdrvNextIterator it;
6253 
6254     for (bs = bdrv_first(&it); bs; bs = bdrv_next(&it)) {
6255         AioContext *aio_context = bdrv_get_aio_context(bs);
6256         int ret;
6257 
6258         aio_context_acquire(aio_context);
6259         ret = bdrv_invalidate_cache(bs, errp);
6260         aio_context_release(aio_context);
6261         if (ret < 0) {
6262             bdrv_next_cleanup(&it);
6263             return;
6264         }
6265     }
6266 }
6267 
6268 static bool bdrv_has_bds_parent(BlockDriverState *bs, bool only_active)
6269 {
6270     BdrvChild *parent;
6271 
6272     QLIST_FOREACH(parent, &bs->parents, next_parent) {
6273         if (parent->klass->parent_is_bds) {
6274             BlockDriverState *parent_bs = parent->opaque;
6275             if (!only_active || !(parent_bs->open_flags & BDRV_O_INACTIVE)) {
6276                 return true;
6277             }
6278         }
6279     }
6280 
6281     return false;
6282 }
6283 
6284 static int bdrv_inactivate_recurse(BlockDriverState *bs)
6285 {
6286     BdrvChild *child, *parent;
6287     int ret;
6288 
6289     if (!bs->drv) {
6290         return -ENOMEDIUM;
6291     }
6292 
6293     /* Make sure that we don't inactivate a child before its parent.
6294      * It will be covered by recursion from the yet active parent. */
6295     if (bdrv_has_bds_parent(bs, true)) {
6296         return 0;
6297     }
6298 
6299     assert(!(bs->open_flags & BDRV_O_INACTIVE));
6300 
6301     /* Inactivate this node */
6302     if (bs->drv->bdrv_inactivate) {
6303         ret = bs->drv->bdrv_inactivate(bs);
6304         if (ret < 0) {
6305             return ret;
6306         }
6307     }
6308 
6309     QLIST_FOREACH(parent, &bs->parents, next_parent) {
6310         if (parent->klass->inactivate) {
6311             ret = parent->klass->inactivate(parent);
6312             if (ret < 0) {
6313                 return ret;
6314             }
6315         }
6316     }
6317 
6318     bs->open_flags |= BDRV_O_INACTIVE;
6319 
6320     /*
6321      * Update permissions, they may differ for inactive nodes.
6322      * We only tried to loosen restrictions, so errors are not fatal, ignore
6323      * them.
6324      */
6325     bdrv_refresh_perms(bs, NULL);
6326 
6327     /* Recursively inactivate children */
6328     QLIST_FOREACH(child, &bs->children, next) {
6329         ret = bdrv_inactivate_recurse(child->bs);
6330         if (ret < 0) {
6331             return ret;
6332         }
6333     }
6334 
6335     return 0;
6336 }
6337 
6338 int bdrv_inactivate_all(void)
6339 {
6340     BlockDriverState *bs = NULL;
6341     BdrvNextIterator it;
6342     int ret = 0;
6343     GSList *aio_ctxs = NULL, *ctx;
6344 
6345     for (bs = bdrv_first(&it); bs; bs = bdrv_next(&it)) {
6346         AioContext *aio_context = bdrv_get_aio_context(bs);
6347 
6348         if (!g_slist_find(aio_ctxs, aio_context)) {
6349             aio_ctxs = g_slist_prepend(aio_ctxs, aio_context);
6350             aio_context_acquire(aio_context);
6351         }
6352     }
6353 
6354     for (bs = bdrv_first(&it); bs; bs = bdrv_next(&it)) {
6355         /* Nodes with BDS parents are covered by recursion from the last
6356          * parent that gets inactivated. Don't inactivate them a second
6357          * time if that has already happened. */
6358         if (bdrv_has_bds_parent(bs, false)) {
6359             continue;
6360         }
6361         ret = bdrv_inactivate_recurse(bs);
6362         if (ret < 0) {
6363             bdrv_next_cleanup(&it);
6364             goto out;
6365         }
6366     }
6367 
6368 out:
6369     for (ctx = aio_ctxs; ctx != NULL; ctx = ctx->next) {
6370         AioContext *aio_context = ctx->data;
6371         aio_context_release(aio_context);
6372     }
6373     g_slist_free(aio_ctxs);
6374 
6375     return ret;
6376 }
6377 
6378 /**************************************************************/
6379 /* removable device support */
6380 
6381 /**
6382  * Return TRUE if the media is present
6383  */
6384 bool bdrv_is_inserted(BlockDriverState *bs)
6385 {
6386     BlockDriver *drv = bs->drv;
6387     BdrvChild *child;
6388 
6389     if (!drv) {
6390         return false;
6391     }
6392     if (drv->bdrv_is_inserted) {
6393         return drv->bdrv_is_inserted(bs);
6394     }
6395     QLIST_FOREACH(child, &bs->children, next) {
6396         if (!bdrv_is_inserted(child->bs)) {
6397             return false;
6398         }
6399     }
6400     return true;
6401 }
6402 
6403 /**
6404  * If eject_flag is TRUE, eject the media. Otherwise, close the tray
6405  */
6406 void bdrv_eject(BlockDriverState *bs, bool eject_flag)
6407 {
6408     BlockDriver *drv = bs->drv;
6409 
6410     if (drv && drv->bdrv_eject) {
6411         drv->bdrv_eject(bs, eject_flag);
6412     }
6413 }
6414 
6415 /**
6416  * Lock or unlock the media (if it is locked, the user won't be able
6417  * to eject it manually).
6418  */
6419 void bdrv_lock_medium(BlockDriverState *bs, bool locked)
6420 {
6421     BlockDriver *drv = bs->drv;
6422 
6423     trace_bdrv_lock_medium(bs, locked);
6424 
6425     if (drv && drv->bdrv_lock_medium) {
6426         drv->bdrv_lock_medium(bs, locked);
6427     }
6428 }
6429 
6430 /* Get a reference to bs */
6431 void bdrv_ref(BlockDriverState *bs)
6432 {
6433     bs->refcnt++;
6434 }
6435 
6436 /* Release a previously grabbed reference to bs.
6437  * If after releasing, reference count is zero, the BlockDriverState is
6438  * deleted. */
6439 void bdrv_unref(BlockDriverState *bs)
6440 {
6441     if (!bs) {
6442         return;
6443     }
6444     assert(bs->refcnt > 0);
6445     if (--bs->refcnt == 0) {
6446         bdrv_delete(bs);
6447     }
6448 }
6449 
6450 struct BdrvOpBlocker {
6451     Error *reason;
6452     QLIST_ENTRY(BdrvOpBlocker) list;
6453 };
6454 
6455 bool bdrv_op_is_blocked(BlockDriverState *bs, BlockOpType op, Error **errp)
6456 {
6457     BdrvOpBlocker *blocker;
6458     assert((int) op >= 0 && op < BLOCK_OP_TYPE_MAX);
6459     if (!QLIST_EMPTY(&bs->op_blockers[op])) {
6460         blocker = QLIST_FIRST(&bs->op_blockers[op]);
6461         error_propagate_prepend(errp, error_copy(blocker->reason),
6462                                 "Node '%s' is busy: ",
6463                                 bdrv_get_device_or_node_name(bs));
6464         return true;
6465     }
6466     return false;
6467 }
6468 
6469 void bdrv_op_block(BlockDriverState *bs, BlockOpType op, Error *reason)
6470 {
6471     BdrvOpBlocker *blocker;
6472     assert((int) op >= 0 && op < BLOCK_OP_TYPE_MAX);
6473 
6474     blocker = g_new0(BdrvOpBlocker, 1);
6475     blocker->reason = reason;
6476     QLIST_INSERT_HEAD(&bs->op_blockers[op], blocker, list);
6477 }
6478 
6479 void bdrv_op_unblock(BlockDriverState *bs, BlockOpType op, Error *reason)
6480 {
6481     BdrvOpBlocker *blocker, *next;
6482     assert((int) op >= 0 && op < BLOCK_OP_TYPE_MAX);
6483     QLIST_FOREACH_SAFE(blocker, &bs->op_blockers[op], list, next) {
6484         if (blocker->reason == reason) {
6485             QLIST_REMOVE(blocker, list);
6486             g_free(blocker);
6487         }
6488     }
6489 }
6490 
6491 void bdrv_op_block_all(BlockDriverState *bs, Error *reason)
6492 {
6493     int i;
6494     for (i = 0; i < BLOCK_OP_TYPE_MAX; i++) {
6495         bdrv_op_block(bs, i, reason);
6496     }
6497 }
6498 
6499 void bdrv_op_unblock_all(BlockDriverState *bs, Error *reason)
6500 {
6501     int i;
6502     for (i = 0; i < BLOCK_OP_TYPE_MAX; i++) {
6503         bdrv_op_unblock(bs, i, reason);
6504     }
6505 }
6506 
6507 bool bdrv_op_blocker_is_empty(BlockDriverState *bs)
6508 {
6509     int i;
6510 
6511     for (i = 0; i < BLOCK_OP_TYPE_MAX; i++) {
6512         if (!QLIST_EMPTY(&bs->op_blockers[i])) {
6513             return false;
6514         }
6515     }
6516     return true;
6517 }
6518 
6519 void bdrv_img_create(const char *filename, const char *fmt,
6520                      const char *base_filename, const char *base_fmt,
6521                      char *options, uint64_t img_size, int flags, bool quiet,
6522                      Error **errp)
6523 {
6524     QemuOptsList *create_opts = NULL;
6525     QemuOpts *opts = NULL;
6526     const char *backing_fmt, *backing_file;
6527     int64_t size;
6528     BlockDriver *drv, *proto_drv;
6529     Error *local_err = NULL;
6530     int ret = 0;
6531 
6532     /* Find driver and parse its options */
6533     drv = bdrv_find_format(fmt);
6534     if (!drv) {
6535         error_setg(errp, "Unknown file format '%s'", fmt);
6536         return;
6537     }
6538 
6539     proto_drv = bdrv_find_protocol(filename, true, errp);
6540     if (!proto_drv) {
6541         return;
6542     }
6543 
6544     if (!drv->create_opts) {
6545         error_setg(errp, "Format driver '%s' does not support image creation",
6546                    drv->format_name);
6547         return;
6548     }
6549 
6550     if (!proto_drv->create_opts) {
6551         error_setg(errp, "Protocol driver '%s' does not support image creation",
6552                    proto_drv->format_name);
6553         return;
6554     }
6555 
6556     /* Create parameter list */
6557     create_opts = qemu_opts_append(create_opts, drv->create_opts);
6558     create_opts = qemu_opts_append(create_opts, proto_drv->create_opts);
6559 
6560     opts = qemu_opts_create(create_opts, NULL, 0, &error_abort);
6561 
6562     /* Parse -o options */
6563     if (options) {
6564         if (!qemu_opts_do_parse(opts, options, NULL, errp)) {
6565             goto out;
6566         }
6567     }
6568 
6569     if (!qemu_opt_get(opts, BLOCK_OPT_SIZE)) {
6570         qemu_opt_set_number(opts, BLOCK_OPT_SIZE, img_size, &error_abort);
6571     } else if (img_size != UINT64_C(-1)) {
6572         error_setg(errp, "The image size must be specified only once");
6573         goto out;
6574     }
6575 
6576     if (base_filename) {
6577         if (!qemu_opt_set(opts, BLOCK_OPT_BACKING_FILE, base_filename,
6578                           NULL)) {
6579             error_setg(errp, "Backing file not supported for file format '%s'",
6580                        fmt);
6581             goto out;
6582         }
6583     }
6584 
6585     if (base_fmt) {
6586         if (!qemu_opt_set(opts, BLOCK_OPT_BACKING_FMT, base_fmt, NULL)) {
6587             error_setg(errp, "Backing file format not supported for file "
6588                              "format '%s'", fmt);
6589             goto out;
6590         }
6591     }
6592 
6593     backing_file = qemu_opt_get(opts, BLOCK_OPT_BACKING_FILE);
6594     if (backing_file) {
6595         if (!strcmp(filename, backing_file)) {
6596             error_setg(errp, "Error: Trying to create an image with the "
6597                              "same filename as the backing file");
6598             goto out;
6599         }
6600         if (backing_file[0] == '\0') {
6601             error_setg(errp, "Expected backing file name, got empty string");
6602             goto out;
6603         }
6604     }
6605 
6606     backing_fmt = qemu_opt_get(opts, BLOCK_OPT_BACKING_FMT);
6607 
6608     /* The size for the image must always be specified, unless we have a backing
6609      * file and we have not been forbidden from opening it. */
6610     size = qemu_opt_get_size(opts, BLOCK_OPT_SIZE, img_size);
6611     if (backing_file && !(flags & BDRV_O_NO_BACKING)) {
6612         BlockDriverState *bs;
6613         char *full_backing;
6614         int back_flags;
6615         QDict *backing_options = NULL;
6616 
6617         full_backing =
6618             bdrv_get_full_backing_filename_from_filename(filename, backing_file,
6619                                                          &local_err);
6620         if (local_err) {
6621             goto out;
6622         }
6623         assert(full_backing);
6624 
6625         /*
6626          * No need to do I/O here, which allows us to open encrypted
6627          * backing images without needing the secret
6628          */
6629         back_flags = flags;
6630         back_flags &= ~(BDRV_O_RDWR | BDRV_O_SNAPSHOT | BDRV_O_NO_BACKING);
6631         back_flags |= BDRV_O_NO_IO;
6632 
6633         backing_options = qdict_new();
6634         if (backing_fmt) {
6635             qdict_put_str(backing_options, "driver", backing_fmt);
6636         }
6637         qdict_put_bool(backing_options, BDRV_OPT_FORCE_SHARE, true);
6638 
6639         bs = bdrv_open(full_backing, NULL, backing_options, back_flags,
6640                        &local_err);
6641         g_free(full_backing);
6642         if (!bs) {
6643             error_append_hint(&local_err, "Could not open backing image.\n");
6644             goto out;
6645         } else {
6646             if (!backing_fmt) {
6647                 error_setg(&local_err,
6648                            "Backing file specified without backing format");
6649                 error_append_hint(&local_err, "Detected format of %s.",
6650                                   bs->drv->format_name);
6651                 goto out;
6652             }
6653             if (size == -1) {
6654                 /* Opened BS, have no size */
6655                 size = bdrv_getlength(bs);
6656                 if (size < 0) {
6657                     error_setg_errno(errp, -size, "Could not get size of '%s'",
6658                                      backing_file);
6659                     bdrv_unref(bs);
6660                     goto out;
6661                 }
6662                 qemu_opt_set_number(opts, BLOCK_OPT_SIZE, size, &error_abort);
6663             }
6664             bdrv_unref(bs);
6665         }
6666         /* (backing_file && !(flags & BDRV_O_NO_BACKING)) */
6667     } else if (backing_file && !backing_fmt) {
6668         error_setg(&local_err,
6669                    "Backing file specified without backing format");
6670         goto out;
6671     }
6672 
6673     if (size == -1) {
6674         error_setg(errp, "Image creation needs a size parameter");
6675         goto out;
6676     }
6677 
6678     if (!quiet) {
6679         printf("Formatting '%s', fmt=%s ", filename, fmt);
6680         qemu_opts_print(opts, " ");
6681         puts("");
6682         fflush(stdout);
6683     }
6684 
6685     ret = bdrv_create(drv, filename, opts, &local_err);
6686 
6687     if (ret == -EFBIG) {
6688         /* This is generally a better message than whatever the driver would
6689          * deliver (especially because of the cluster_size_hint), since that
6690          * is most probably not much different from "image too large". */
6691         const char *cluster_size_hint = "";
6692         if (qemu_opt_get_size(opts, BLOCK_OPT_CLUSTER_SIZE, 0)) {
6693             cluster_size_hint = " (try using a larger cluster size)";
6694         }
6695         error_setg(errp, "The image size is too large for file format '%s'"
6696                    "%s", fmt, cluster_size_hint);
6697         error_free(local_err);
6698         local_err = NULL;
6699     }
6700 
6701 out:
6702     qemu_opts_del(opts);
6703     qemu_opts_free(create_opts);
6704     error_propagate(errp, local_err);
6705 }
6706 
6707 AioContext *bdrv_get_aio_context(BlockDriverState *bs)
6708 {
6709     return bs ? bs->aio_context : qemu_get_aio_context();
6710 }
6711 
6712 AioContext *coroutine_fn bdrv_co_enter(BlockDriverState *bs)
6713 {
6714     Coroutine *self = qemu_coroutine_self();
6715     AioContext *old_ctx = qemu_coroutine_get_aio_context(self);
6716     AioContext *new_ctx;
6717 
6718     /*
6719      * Increase bs->in_flight to ensure that this operation is completed before
6720      * moving the node to a different AioContext. Read new_ctx only afterwards.
6721      */
6722     bdrv_inc_in_flight(bs);
6723 
6724     new_ctx = bdrv_get_aio_context(bs);
6725     aio_co_reschedule_self(new_ctx);
6726     return old_ctx;
6727 }
6728 
6729 void coroutine_fn bdrv_co_leave(BlockDriverState *bs, AioContext *old_ctx)
6730 {
6731     aio_co_reschedule_self(old_ctx);
6732     bdrv_dec_in_flight(bs);
6733 }
6734 
6735 void coroutine_fn bdrv_co_lock(BlockDriverState *bs)
6736 {
6737     AioContext *ctx = bdrv_get_aio_context(bs);
6738 
6739     /* In the main thread, bs->aio_context won't change concurrently */
6740     assert(qemu_get_current_aio_context() == qemu_get_aio_context());
6741 
6742     /*
6743      * We're in coroutine context, so we already hold the lock of the main
6744      * loop AioContext. Don't lock it twice to avoid deadlocks.
6745      */
6746     assert(qemu_in_coroutine());
6747     if (ctx != qemu_get_aio_context()) {
6748         aio_context_acquire(ctx);
6749     }
6750 }
6751 
6752 void coroutine_fn bdrv_co_unlock(BlockDriverState *bs)
6753 {
6754     AioContext *ctx = bdrv_get_aio_context(bs);
6755 
6756     assert(qemu_in_coroutine());
6757     if (ctx != qemu_get_aio_context()) {
6758         aio_context_release(ctx);
6759     }
6760 }
6761 
6762 void bdrv_coroutine_enter(BlockDriverState *bs, Coroutine *co)
6763 {
6764     aio_co_enter(bdrv_get_aio_context(bs), co);
6765 }
6766 
6767 static void bdrv_do_remove_aio_context_notifier(BdrvAioNotifier *ban)
6768 {
6769     QLIST_REMOVE(ban, list);
6770     g_free(ban);
6771 }
6772 
6773 static void bdrv_detach_aio_context(BlockDriverState *bs)
6774 {
6775     BdrvAioNotifier *baf, *baf_tmp;
6776 
6777     assert(!bs->walking_aio_notifiers);
6778     bs->walking_aio_notifiers = true;
6779     QLIST_FOREACH_SAFE(baf, &bs->aio_notifiers, list, baf_tmp) {
6780         if (baf->deleted) {
6781             bdrv_do_remove_aio_context_notifier(baf);
6782         } else {
6783             baf->detach_aio_context(baf->opaque);
6784         }
6785     }
6786     /* Never mind iterating again to check for ->deleted.  bdrv_close() will
6787      * remove remaining aio notifiers if we aren't called again.
6788      */
6789     bs->walking_aio_notifiers = false;
6790 
6791     if (bs->drv && bs->drv->bdrv_detach_aio_context) {
6792         bs->drv->bdrv_detach_aio_context(bs);
6793     }
6794 
6795     if (bs->quiesce_counter) {
6796         aio_enable_external(bs->aio_context);
6797     }
6798     bs->aio_context = NULL;
6799 }
6800 
6801 static void bdrv_attach_aio_context(BlockDriverState *bs,
6802                                     AioContext *new_context)
6803 {
6804     BdrvAioNotifier *ban, *ban_tmp;
6805 
6806     if (bs->quiesce_counter) {
6807         aio_disable_external(new_context);
6808     }
6809 
6810     bs->aio_context = new_context;
6811 
6812     if (bs->drv && bs->drv->bdrv_attach_aio_context) {
6813         bs->drv->bdrv_attach_aio_context(bs, new_context);
6814     }
6815 
6816     assert(!bs->walking_aio_notifiers);
6817     bs->walking_aio_notifiers = true;
6818     QLIST_FOREACH_SAFE(ban, &bs->aio_notifiers, list, ban_tmp) {
6819         if (ban->deleted) {
6820             bdrv_do_remove_aio_context_notifier(ban);
6821         } else {
6822             ban->attached_aio_context(new_context, ban->opaque);
6823         }
6824     }
6825     bs->walking_aio_notifiers = false;
6826 }
6827 
6828 /*
6829  * Changes the AioContext used for fd handlers, timers, and BHs by this
6830  * BlockDriverState and all its children and parents.
6831  *
6832  * Must be called from the main AioContext.
6833  *
6834  * The caller must own the AioContext lock for the old AioContext of bs, but it
6835  * must not own the AioContext lock for new_context (unless new_context is the
6836  * same as the current context of bs).
6837  *
6838  * @ignore will accumulate all visited BdrvChild object. The caller is
6839  * responsible for freeing the list afterwards.
6840  */
6841 void bdrv_set_aio_context_ignore(BlockDriverState *bs,
6842                                  AioContext *new_context, GSList **ignore)
6843 {
6844     AioContext *old_context = bdrv_get_aio_context(bs);
6845     GSList *children_to_process = NULL;
6846     GSList *parents_to_process = NULL;
6847     GSList *entry;
6848     BdrvChild *child, *parent;
6849 
6850     g_assert(qemu_get_current_aio_context() == qemu_get_aio_context());
6851 
6852     if (old_context == new_context) {
6853         return;
6854     }
6855 
6856     bdrv_drained_begin(bs);
6857 
6858     QLIST_FOREACH(child, &bs->children, next) {
6859         if (g_slist_find(*ignore, child)) {
6860             continue;
6861         }
6862         *ignore = g_slist_prepend(*ignore, child);
6863         children_to_process = g_slist_prepend(children_to_process, child);
6864     }
6865 
6866     QLIST_FOREACH(parent, &bs->parents, next_parent) {
6867         if (g_slist_find(*ignore, parent)) {
6868             continue;
6869         }
6870         *ignore = g_slist_prepend(*ignore, parent);
6871         parents_to_process = g_slist_prepend(parents_to_process, parent);
6872     }
6873 
6874     for (entry = children_to_process;
6875          entry != NULL;
6876          entry = g_slist_next(entry)) {
6877         child = entry->data;
6878         bdrv_set_aio_context_ignore(child->bs, new_context, ignore);
6879     }
6880     g_slist_free(children_to_process);
6881 
6882     for (entry = parents_to_process;
6883          entry != NULL;
6884          entry = g_slist_next(entry)) {
6885         parent = entry->data;
6886         assert(parent->klass->set_aio_ctx);
6887         parent->klass->set_aio_ctx(parent, new_context, ignore);
6888     }
6889     g_slist_free(parents_to_process);
6890 
6891     bdrv_detach_aio_context(bs);
6892 
6893     /* Acquire the new context, if necessary */
6894     if (qemu_get_aio_context() != new_context) {
6895         aio_context_acquire(new_context);
6896     }
6897 
6898     bdrv_attach_aio_context(bs, new_context);
6899 
6900     /*
6901      * If this function was recursively called from
6902      * bdrv_set_aio_context_ignore(), there may be nodes in the
6903      * subtree that have not yet been moved to the new AioContext.
6904      * Release the old one so bdrv_drained_end() can poll them.
6905      */
6906     if (qemu_get_aio_context() != old_context) {
6907         aio_context_release(old_context);
6908     }
6909 
6910     bdrv_drained_end(bs);
6911 
6912     if (qemu_get_aio_context() != old_context) {
6913         aio_context_acquire(old_context);
6914     }
6915     if (qemu_get_aio_context() != new_context) {
6916         aio_context_release(new_context);
6917     }
6918 }
6919 
6920 static bool bdrv_parent_can_set_aio_context(BdrvChild *c, AioContext *ctx,
6921                                             GSList **ignore, Error **errp)
6922 {
6923     if (g_slist_find(*ignore, c)) {
6924         return true;
6925     }
6926     *ignore = g_slist_prepend(*ignore, c);
6927 
6928     /*
6929      * A BdrvChildClass that doesn't handle AioContext changes cannot
6930      * tolerate any AioContext changes
6931      */
6932     if (!c->klass->can_set_aio_ctx) {
6933         char *user = bdrv_child_user_desc(c);
6934         error_setg(errp, "Changing iothreads is not supported by %s", user);
6935         g_free(user);
6936         return false;
6937     }
6938     if (!c->klass->can_set_aio_ctx(c, ctx, ignore, errp)) {
6939         assert(!errp || *errp);
6940         return false;
6941     }
6942     return true;
6943 }
6944 
6945 bool bdrv_child_can_set_aio_context(BdrvChild *c, AioContext *ctx,
6946                                     GSList **ignore, Error **errp)
6947 {
6948     if (g_slist_find(*ignore, c)) {
6949         return true;
6950     }
6951     *ignore = g_slist_prepend(*ignore, c);
6952     return bdrv_can_set_aio_context(c->bs, ctx, ignore, errp);
6953 }
6954 
6955 /* @ignore will accumulate all visited BdrvChild object. The caller is
6956  * responsible for freeing the list afterwards. */
6957 bool bdrv_can_set_aio_context(BlockDriverState *bs, AioContext *ctx,
6958                               GSList **ignore, Error **errp)
6959 {
6960     BdrvChild *c;
6961 
6962     if (bdrv_get_aio_context(bs) == ctx) {
6963         return true;
6964     }
6965 
6966     QLIST_FOREACH(c, &bs->parents, next_parent) {
6967         if (!bdrv_parent_can_set_aio_context(c, ctx, ignore, errp)) {
6968             return false;
6969         }
6970     }
6971     QLIST_FOREACH(c, &bs->children, next) {
6972         if (!bdrv_child_can_set_aio_context(c, ctx, ignore, errp)) {
6973             return false;
6974         }
6975     }
6976 
6977     return true;
6978 }
6979 
6980 int bdrv_child_try_set_aio_context(BlockDriverState *bs, AioContext *ctx,
6981                                    BdrvChild *ignore_child, Error **errp)
6982 {
6983     GSList *ignore;
6984     bool ret;
6985 
6986     ignore = ignore_child ? g_slist_prepend(NULL, ignore_child) : NULL;
6987     ret = bdrv_can_set_aio_context(bs, ctx, &ignore, errp);
6988     g_slist_free(ignore);
6989 
6990     if (!ret) {
6991         return -EPERM;
6992     }
6993 
6994     ignore = ignore_child ? g_slist_prepend(NULL, ignore_child) : NULL;
6995     bdrv_set_aio_context_ignore(bs, ctx, &ignore);
6996     g_slist_free(ignore);
6997 
6998     return 0;
6999 }
7000 
7001 int bdrv_try_set_aio_context(BlockDriverState *bs, AioContext *ctx,
7002                              Error **errp)
7003 {
7004     return bdrv_child_try_set_aio_context(bs, ctx, NULL, errp);
7005 }
7006 
7007 void bdrv_add_aio_context_notifier(BlockDriverState *bs,
7008         void (*attached_aio_context)(AioContext *new_context, void *opaque),
7009         void (*detach_aio_context)(void *opaque), void *opaque)
7010 {
7011     BdrvAioNotifier *ban = g_new(BdrvAioNotifier, 1);
7012     *ban = (BdrvAioNotifier){
7013         .attached_aio_context = attached_aio_context,
7014         .detach_aio_context   = detach_aio_context,
7015         .opaque               = opaque
7016     };
7017 
7018     QLIST_INSERT_HEAD(&bs->aio_notifiers, ban, list);
7019 }
7020 
7021 void bdrv_remove_aio_context_notifier(BlockDriverState *bs,
7022                                       void (*attached_aio_context)(AioContext *,
7023                                                                    void *),
7024                                       void (*detach_aio_context)(void *),
7025                                       void *opaque)
7026 {
7027     BdrvAioNotifier *ban, *ban_next;
7028 
7029     QLIST_FOREACH_SAFE(ban, &bs->aio_notifiers, list, ban_next) {
7030         if (ban->attached_aio_context == attached_aio_context &&
7031             ban->detach_aio_context   == detach_aio_context   &&
7032             ban->opaque               == opaque               &&
7033             ban->deleted              == false)
7034         {
7035             if (bs->walking_aio_notifiers) {
7036                 ban->deleted = true;
7037             } else {
7038                 bdrv_do_remove_aio_context_notifier(ban);
7039             }
7040             return;
7041         }
7042     }
7043 
7044     abort();
7045 }
7046 
7047 int bdrv_amend_options(BlockDriverState *bs, QemuOpts *opts,
7048                        BlockDriverAmendStatusCB *status_cb, void *cb_opaque,
7049                        bool force,
7050                        Error **errp)
7051 {
7052     if (!bs->drv) {
7053         error_setg(errp, "Node is ejected");
7054         return -ENOMEDIUM;
7055     }
7056     if (!bs->drv->bdrv_amend_options) {
7057         error_setg(errp, "Block driver '%s' does not support option amendment",
7058                    bs->drv->format_name);
7059         return -ENOTSUP;
7060     }
7061     return bs->drv->bdrv_amend_options(bs, opts, status_cb,
7062                                        cb_opaque, force, errp);
7063 }
7064 
7065 /*
7066  * This function checks whether the given @to_replace is allowed to be
7067  * replaced by a node that always shows the same data as @bs.  This is
7068  * used for example to verify whether the mirror job can replace
7069  * @to_replace by the target mirrored from @bs.
7070  * To be replaceable, @bs and @to_replace may either be guaranteed to
7071  * always show the same data (because they are only connected through
7072  * filters), or some driver may allow replacing one of its children
7073  * because it can guarantee that this child's data is not visible at
7074  * all (for example, for dissenting quorum children that have no other
7075  * parents).
7076  */
7077 bool bdrv_recurse_can_replace(BlockDriverState *bs,
7078                               BlockDriverState *to_replace)
7079 {
7080     BlockDriverState *filtered;
7081 
7082     if (!bs || !bs->drv) {
7083         return false;
7084     }
7085 
7086     if (bs == to_replace) {
7087         return true;
7088     }
7089 
7090     /* See what the driver can do */
7091     if (bs->drv->bdrv_recurse_can_replace) {
7092         return bs->drv->bdrv_recurse_can_replace(bs, to_replace);
7093     }
7094 
7095     /* For filters without an own implementation, we can recurse on our own */
7096     filtered = bdrv_filter_bs(bs);
7097     if (filtered) {
7098         return bdrv_recurse_can_replace(filtered, to_replace);
7099     }
7100 
7101     /* Safe default */
7102     return false;
7103 }
7104 
7105 /*
7106  * Check whether the given @node_name can be replaced by a node that
7107  * has the same data as @parent_bs.  If so, return @node_name's BDS;
7108  * NULL otherwise.
7109  *
7110  * @node_name must be a (recursive) *child of @parent_bs (or this
7111  * function will return NULL).
7112  *
7113  * The result (whether the node can be replaced or not) is only valid
7114  * for as long as no graph or permission changes occur.
7115  */
7116 BlockDriverState *check_to_replace_node(BlockDriverState *parent_bs,
7117                                         const char *node_name, Error **errp)
7118 {
7119     BlockDriverState *to_replace_bs = bdrv_find_node(node_name);
7120     AioContext *aio_context;
7121 
7122     if (!to_replace_bs) {
7123         error_setg(errp, "Failed to find node with node-name='%s'", node_name);
7124         return NULL;
7125     }
7126 
7127     aio_context = bdrv_get_aio_context(to_replace_bs);
7128     aio_context_acquire(aio_context);
7129 
7130     if (bdrv_op_is_blocked(to_replace_bs, BLOCK_OP_TYPE_REPLACE, errp)) {
7131         to_replace_bs = NULL;
7132         goto out;
7133     }
7134 
7135     /* We don't want arbitrary node of the BDS chain to be replaced only the top
7136      * most non filter in order to prevent data corruption.
7137      * Another benefit is that this tests exclude backing files which are
7138      * blocked by the backing blockers.
7139      */
7140     if (!bdrv_recurse_can_replace(parent_bs, to_replace_bs)) {
7141         error_setg(errp, "Cannot replace '%s' by a node mirrored from '%s', "
7142                    "because it cannot be guaranteed that doing so would not "
7143                    "lead to an abrupt change of visible data",
7144                    node_name, parent_bs->node_name);
7145         to_replace_bs = NULL;
7146         goto out;
7147     }
7148 
7149 out:
7150     aio_context_release(aio_context);
7151     return to_replace_bs;
7152 }
7153 
7154 /**
7155  * Iterates through the list of runtime option keys that are said to
7156  * be "strong" for a BDS.  An option is called "strong" if it changes
7157  * a BDS's data.  For example, the null block driver's "size" and
7158  * "read-zeroes" options are strong, but its "latency-ns" option is
7159  * not.
7160  *
7161  * If a key returned by this function ends with a dot, all options
7162  * starting with that prefix are strong.
7163  */
7164 static const char *const *strong_options(BlockDriverState *bs,
7165                                          const char *const *curopt)
7166 {
7167     static const char *const global_options[] = {
7168         "driver", "filename", NULL
7169     };
7170 
7171     if (!curopt) {
7172         return &global_options[0];
7173     }
7174 
7175     curopt++;
7176     if (curopt == &global_options[ARRAY_SIZE(global_options) - 1] && bs->drv) {
7177         curopt = bs->drv->strong_runtime_opts;
7178     }
7179 
7180     return (curopt && *curopt) ? curopt : NULL;
7181 }
7182 
7183 /**
7184  * Copies all strong runtime options from bs->options to the given
7185  * QDict.  The set of strong option keys is determined by invoking
7186  * strong_options().
7187  *
7188  * Returns true iff any strong option was present in bs->options (and
7189  * thus copied to the target QDict) with the exception of "filename"
7190  * and "driver".  The caller is expected to use this value to decide
7191  * whether the existence of strong options prevents the generation of
7192  * a plain filename.
7193  */
7194 static bool append_strong_runtime_options(QDict *d, BlockDriverState *bs)
7195 {
7196     bool found_any = false;
7197     const char *const *option_name = NULL;
7198 
7199     if (!bs->drv) {
7200         return false;
7201     }
7202 
7203     while ((option_name = strong_options(bs, option_name))) {
7204         bool option_given = false;
7205 
7206         assert(strlen(*option_name) > 0);
7207         if ((*option_name)[strlen(*option_name) - 1] != '.') {
7208             QObject *entry = qdict_get(bs->options, *option_name);
7209             if (!entry) {
7210                 continue;
7211             }
7212 
7213             qdict_put_obj(d, *option_name, qobject_ref(entry));
7214             option_given = true;
7215         } else {
7216             const QDictEntry *entry;
7217             for (entry = qdict_first(bs->options); entry;
7218                  entry = qdict_next(bs->options, entry))
7219             {
7220                 if (strstart(qdict_entry_key(entry), *option_name, NULL)) {
7221                     qdict_put_obj(d, qdict_entry_key(entry),
7222                                   qobject_ref(qdict_entry_value(entry)));
7223                     option_given = true;
7224                 }
7225             }
7226         }
7227 
7228         /* While "driver" and "filename" need to be included in a JSON filename,
7229          * their existence does not prohibit generation of a plain filename. */
7230         if (!found_any && option_given &&
7231             strcmp(*option_name, "driver") && strcmp(*option_name, "filename"))
7232         {
7233             found_any = true;
7234         }
7235     }
7236 
7237     if (!qdict_haskey(d, "driver")) {
7238         /* Drivers created with bdrv_new_open_driver() may not have a
7239          * @driver option.  Add it here. */
7240         qdict_put_str(d, "driver", bs->drv->format_name);
7241     }
7242 
7243     return found_any;
7244 }
7245 
7246 /* Note: This function may return false positives; it may return true
7247  * even if opening the backing file specified by bs's image header
7248  * would result in exactly bs->backing. */
7249 bool bdrv_backing_overridden(BlockDriverState *bs)
7250 {
7251     if (bs->backing) {
7252         return strcmp(bs->auto_backing_file,
7253                       bs->backing->bs->filename);
7254     } else {
7255         /* No backing BDS, so if the image header reports any backing
7256          * file, it must have been suppressed */
7257         return bs->auto_backing_file[0] != '\0';
7258     }
7259 }
7260 
7261 /* Updates the following BDS fields:
7262  *  - exact_filename: A filename which may be used for opening a block device
7263  *                    which (mostly) equals the given BDS (even without any
7264  *                    other options; so reading and writing must return the same
7265  *                    results, but caching etc. may be different)
7266  *  - full_open_options: Options which, when given when opening a block device
7267  *                       (without a filename), result in a BDS (mostly)
7268  *                       equalling the given one
7269  *  - filename: If exact_filename is set, it is copied here. Otherwise,
7270  *              full_open_options is converted to a JSON object, prefixed with
7271  *              "json:" (for use through the JSON pseudo protocol) and put here.
7272  */
7273 void bdrv_refresh_filename(BlockDriverState *bs)
7274 {
7275     BlockDriver *drv = bs->drv;
7276     BdrvChild *child;
7277     BlockDriverState *primary_child_bs;
7278     QDict *opts;
7279     bool backing_overridden;
7280     bool generate_json_filename; /* Whether our default implementation should
7281                                     fill exact_filename (false) or not (true) */
7282 
7283     if (!drv) {
7284         return;
7285     }
7286 
7287     /* This BDS's file name may depend on any of its children's file names, so
7288      * refresh those first */
7289     QLIST_FOREACH(child, &bs->children, next) {
7290         bdrv_refresh_filename(child->bs);
7291     }
7292 
7293     if (bs->implicit) {
7294         /* For implicit nodes, just copy everything from the single child */
7295         child = QLIST_FIRST(&bs->children);
7296         assert(QLIST_NEXT(child, next) == NULL);
7297 
7298         pstrcpy(bs->exact_filename, sizeof(bs->exact_filename),
7299                 child->bs->exact_filename);
7300         pstrcpy(bs->filename, sizeof(bs->filename), child->bs->filename);
7301 
7302         qobject_unref(bs->full_open_options);
7303         bs->full_open_options = qobject_ref(child->bs->full_open_options);
7304 
7305         return;
7306     }
7307 
7308     backing_overridden = bdrv_backing_overridden(bs);
7309 
7310     if (bs->open_flags & BDRV_O_NO_IO) {
7311         /* Without I/O, the backing file does not change anything.
7312          * Therefore, in such a case (primarily qemu-img), we can
7313          * pretend the backing file has not been overridden even if
7314          * it technically has been. */
7315         backing_overridden = false;
7316     }
7317 
7318     /* Gather the options QDict */
7319     opts = qdict_new();
7320     generate_json_filename = append_strong_runtime_options(opts, bs);
7321     generate_json_filename |= backing_overridden;
7322 
7323     if (drv->bdrv_gather_child_options) {
7324         /* Some block drivers may not want to present all of their children's
7325          * options, or name them differently from BdrvChild.name */
7326         drv->bdrv_gather_child_options(bs, opts, backing_overridden);
7327     } else {
7328         QLIST_FOREACH(child, &bs->children, next) {
7329             if (child == bs->backing && !backing_overridden) {
7330                 /* We can skip the backing BDS if it has not been overridden */
7331                 continue;
7332             }
7333 
7334             qdict_put(opts, child->name,
7335                       qobject_ref(child->bs->full_open_options));
7336         }
7337 
7338         if (backing_overridden && !bs->backing) {
7339             /* Force no backing file */
7340             qdict_put_null(opts, "backing");
7341         }
7342     }
7343 
7344     qobject_unref(bs->full_open_options);
7345     bs->full_open_options = opts;
7346 
7347     primary_child_bs = bdrv_primary_bs(bs);
7348 
7349     if (drv->bdrv_refresh_filename) {
7350         /* Obsolete information is of no use here, so drop the old file name
7351          * information before refreshing it */
7352         bs->exact_filename[0] = '\0';
7353 
7354         drv->bdrv_refresh_filename(bs);
7355     } else if (primary_child_bs) {
7356         /*
7357          * Try to reconstruct valid information from the underlying
7358          * file -- this only works for format nodes (filter nodes
7359          * cannot be probed and as such must be selected by the user
7360          * either through an options dict, or through a special
7361          * filename which the filter driver must construct in its
7362          * .bdrv_refresh_filename() implementation).
7363          */
7364 
7365         bs->exact_filename[0] = '\0';
7366 
7367         /*
7368          * We can use the underlying file's filename if:
7369          * - it has a filename,
7370          * - the current BDS is not a filter,
7371          * - the file is a protocol BDS, and
7372          * - opening that file (as this BDS's format) will automatically create
7373          *   the BDS tree we have right now, that is:
7374          *   - the user did not significantly change this BDS's behavior with
7375          *     some explicit (strong) options
7376          *   - no non-file child of this BDS has been overridden by the user
7377          *   Both of these conditions are represented by generate_json_filename.
7378          */
7379         if (primary_child_bs->exact_filename[0] &&
7380             primary_child_bs->drv->bdrv_file_open &&
7381             !drv->is_filter && !generate_json_filename)
7382         {
7383             strcpy(bs->exact_filename, primary_child_bs->exact_filename);
7384         }
7385     }
7386 
7387     if (bs->exact_filename[0]) {
7388         pstrcpy(bs->filename, sizeof(bs->filename), bs->exact_filename);
7389     } else {
7390         GString *json = qobject_to_json(QOBJECT(bs->full_open_options));
7391         if (snprintf(bs->filename, sizeof(bs->filename), "json:%s",
7392                      json->str) >= sizeof(bs->filename)) {
7393             /* Give user a hint if we truncated things. */
7394             strcpy(bs->filename + sizeof(bs->filename) - 4, "...");
7395         }
7396         g_string_free(json, true);
7397     }
7398 }
7399 
7400 char *bdrv_dirname(BlockDriverState *bs, Error **errp)
7401 {
7402     BlockDriver *drv = bs->drv;
7403     BlockDriverState *child_bs;
7404 
7405     if (!drv) {
7406         error_setg(errp, "Node '%s' is ejected", bs->node_name);
7407         return NULL;
7408     }
7409 
7410     if (drv->bdrv_dirname) {
7411         return drv->bdrv_dirname(bs, errp);
7412     }
7413 
7414     child_bs = bdrv_primary_bs(bs);
7415     if (child_bs) {
7416         return bdrv_dirname(child_bs, errp);
7417     }
7418 
7419     bdrv_refresh_filename(bs);
7420     if (bs->exact_filename[0] != '\0') {
7421         return path_combine(bs->exact_filename, "");
7422     }
7423 
7424     error_setg(errp, "Cannot generate a base directory for %s nodes",
7425                drv->format_name);
7426     return NULL;
7427 }
7428 
7429 /*
7430  * Hot add/remove a BDS's child. So the user can take a child offline when
7431  * it is broken and take a new child online
7432  */
7433 void bdrv_add_child(BlockDriverState *parent_bs, BlockDriverState *child_bs,
7434                     Error **errp)
7435 {
7436 
7437     if (!parent_bs->drv || !parent_bs->drv->bdrv_add_child) {
7438         error_setg(errp, "The node %s does not support adding a child",
7439                    bdrv_get_device_or_node_name(parent_bs));
7440         return;
7441     }
7442 
7443     if (!QLIST_EMPTY(&child_bs->parents)) {
7444         error_setg(errp, "The node %s already has a parent",
7445                    child_bs->node_name);
7446         return;
7447     }
7448 
7449     parent_bs->drv->bdrv_add_child(parent_bs, child_bs, errp);
7450 }
7451 
7452 void bdrv_del_child(BlockDriverState *parent_bs, BdrvChild *child, Error **errp)
7453 {
7454     BdrvChild *tmp;
7455 
7456     if (!parent_bs->drv || !parent_bs->drv->bdrv_del_child) {
7457         error_setg(errp, "The node %s does not support removing a child",
7458                    bdrv_get_device_or_node_name(parent_bs));
7459         return;
7460     }
7461 
7462     QLIST_FOREACH(tmp, &parent_bs->children, next) {
7463         if (tmp == child) {
7464             break;
7465         }
7466     }
7467 
7468     if (!tmp) {
7469         error_setg(errp, "The node %s does not have a child named %s",
7470                    bdrv_get_device_or_node_name(parent_bs),
7471                    bdrv_get_device_or_node_name(child->bs));
7472         return;
7473     }
7474 
7475     parent_bs->drv->bdrv_del_child(parent_bs, child, errp);
7476 }
7477 
7478 int bdrv_make_empty(BdrvChild *c, Error **errp)
7479 {
7480     BlockDriver *drv = c->bs->drv;
7481     int ret;
7482 
7483     assert(c->perm & (BLK_PERM_WRITE | BLK_PERM_WRITE_UNCHANGED));
7484 
7485     if (!drv->bdrv_make_empty) {
7486         error_setg(errp, "%s does not support emptying nodes",
7487                    drv->format_name);
7488         return -ENOTSUP;
7489     }
7490 
7491     ret = drv->bdrv_make_empty(c->bs);
7492     if (ret < 0) {
7493         error_setg_errno(errp, -ret, "Failed to empty %s",
7494                          c->bs->filename);
7495         return ret;
7496     }
7497 
7498     return 0;
7499 }
7500 
7501 /*
7502  * Return the child that @bs acts as an overlay for, and from which data may be
7503  * copied in COW or COR operations.  Usually this is the backing file.
7504  */
7505 BdrvChild *bdrv_cow_child(BlockDriverState *bs)
7506 {
7507     if (!bs || !bs->drv) {
7508         return NULL;
7509     }
7510 
7511     if (bs->drv->is_filter) {
7512         return NULL;
7513     }
7514 
7515     if (!bs->backing) {
7516         return NULL;
7517     }
7518 
7519     assert(bs->backing->role & BDRV_CHILD_COW);
7520     return bs->backing;
7521 }
7522 
7523 /*
7524  * If @bs acts as a filter for exactly one of its children, return
7525  * that child.
7526  */
7527 BdrvChild *bdrv_filter_child(BlockDriverState *bs)
7528 {
7529     BdrvChild *c;
7530 
7531     if (!bs || !bs->drv) {
7532         return NULL;
7533     }
7534 
7535     if (!bs->drv->is_filter) {
7536         return NULL;
7537     }
7538 
7539     /* Only one of @backing or @file may be used */
7540     assert(!(bs->backing && bs->file));
7541 
7542     c = bs->backing ?: bs->file;
7543     if (!c) {
7544         return NULL;
7545     }
7546 
7547     assert(c->role & BDRV_CHILD_FILTERED);
7548     return c;
7549 }
7550 
7551 /*
7552  * Return either the result of bdrv_cow_child() or bdrv_filter_child(),
7553  * whichever is non-NULL.
7554  *
7555  * Return NULL if both are NULL.
7556  */
7557 BdrvChild *bdrv_filter_or_cow_child(BlockDriverState *bs)
7558 {
7559     BdrvChild *cow_child = bdrv_cow_child(bs);
7560     BdrvChild *filter_child = bdrv_filter_child(bs);
7561 
7562     /* Filter nodes cannot have COW backing files */
7563     assert(!(cow_child && filter_child));
7564 
7565     return cow_child ?: filter_child;
7566 }
7567 
7568 /*
7569  * Return the primary child of this node: For filters, that is the
7570  * filtered child.  For other nodes, that is usually the child storing
7571  * metadata.
7572  * (A generally more helpful description is that this is (usually) the
7573  * child that has the same filename as @bs.)
7574  *
7575  * Drivers do not necessarily have a primary child; for example quorum
7576  * does not.
7577  */
7578 BdrvChild *bdrv_primary_child(BlockDriverState *bs)
7579 {
7580     BdrvChild *c, *found = NULL;
7581 
7582     QLIST_FOREACH(c, &bs->children, next) {
7583         if (c->role & BDRV_CHILD_PRIMARY) {
7584             assert(!found);
7585             found = c;
7586         }
7587     }
7588 
7589     return found;
7590 }
7591 
7592 static BlockDriverState *bdrv_do_skip_filters(BlockDriverState *bs,
7593                                               bool stop_on_explicit_filter)
7594 {
7595     BdrvChild *c;
7596 
7597     if (!bs) {
7598         return NULL;
7599     }
7600 
7601     while (!(stop_on_explicit_filter && !bs->implicit)) {
7602         c = bdrv_filter_child(bs);
7603         if (!c) {
7604             /*
7605              * A filter that is embedded in a working block graph must
7606              * have a child.  Assert this here so this function does
7607              * not return a filter node that is not expected by the
7608              * caller.
7609              */
7610             assert(!bs->drv || !bs->drv->is_filter);
7611             break;
7612         }
7613         bs = c->bs;
7614     }
7615     /*
7616      * Note that this treats nodes with bs->drv == NULL as not being
7617      * filters (bs->drv == NULL should be replaced by something else
7618      * anyway).
7619      * The advantage of this behavior is that this function will thus
7620      * always return a non-NULL value (given a non-NULL @bs).
7621      */
7622 
7623     return bs;
7624 }
7625 
7626 /*
7627  * Return the first BDS that has not been added implicitly or that
7628  * does not have a filtered child down the chain starting from @bs
7629  * (including @bs itself).
7630  */
7631 BlockDriverState *bdrv_skip_implicit_filters(BlockDriverState *bs)
7632 {
7633     return bdrv_do_skip_filters(bs, true);
7634 }
7635 
7636 /*
7637  * Return the first BDS that does not have a filtered child down the
7638  * chain starting from @bs (including @bs itself).
7639  */
7640 BlockDriverState *bdrv_skip_filters(BlockDriverState *bs)
7641 {
7642     return bdrv_do_skip_filters(bs, false);
7643 }
7644 
7645 /*
7646  * For a backing chain, return the first non-filter backing image of
7647  * the first non-filter image.
7648  */
7649 BlockDriverState *bdrv_backing_chain_next(BlockDriverState *bs)
7650 {
7651     return bdrv_skip_filters(bdrv_cow_bs(bdrv_skip_filters(bs)));
7652 }
7653