xref: /openbmc/qemu/block/block-backend.c (revision 84d0984dfe336f24109a6792d06aad0e9ae5e0a6)
1 /*
2  * QEMU Block backends
3  *
4  * Copyright (C) 2014-2016 Red Hat, Inc.
5  *
6  * Authors:
7  *  Markus Armbruster <armbru@redhat.com>,
8  *
9  * This work is licensed under the terms of the GNU LGPL, version 2.1
10  * or later.  See the COPYING.LIB file in the top-level directory.
11  */
12 
13 #include "qemu/osdep.h"
14 #include "sysemu/block-backend.h"
15 #include "block/block_int.h"
16 #include "block/blockjob.h"
17 #include "block/throttle-groups.h"
18 #include "sysemu/blockdev.h"
19 #include "sysemu/sysemu.h"
20 #include "qapi-event.h"
21 #include "qemu/id.h"
22 #include "trace.h"
23 
24 /* Number of coroutines to reserve per attached device model */
25 #define COROUTINE_POOL_RESERVATION 64
26 
27 #define NOT_DONE 0x7fffffff /* used while emulated sync operation in progress */
28 
29 static AioContext *blk_aiocb_get_aio_context(BlockAIOCB *acb);
30 
31 struct BlockBackend {
32     char *name;
33     int refcnt;
34     BdrvChild *root;
35     DriveInfo *legacy_dinfo;    /* null unless created by drive_new() */
36     QTAILQ_ENTRY(BlockBackend) link;         /* for block_backends */
37     QTAILQ_ENTRY(BlockBackend) monitor_link; /* for monitor_block_backends */
38     BlockBackendPublic public;
39 
40     void *dev;                  /* attached device model, if any */
41     /* TODO change to DeviceState when all users are qdevified */
42     const BlockDevOps *dev_ops;
43     void *dev_opaque;
44 
45     /* the block size for which the guest device expects atomicity */
46     int guest_block_size;
47 
48     /* If the BDS tree is removed, some of its options are stored here (which
49      * can be used to restore those options in the new BDS on insert) */
50     BlockBackendRootState root_state;
51 
52     bool enable_write_cache;
53 
54     /* I/O stats (display with "info blockstats"). */
55     BlockAcctStats stats;
56 
57     BlockdevOnError on_read_error, on_write_error;
58     bool iostatus_enabled;
59     BlockDeviceIoStatus iostatus;
60 
61     bool allow_write_beyond_eof;
62 
63     NotifierList remove_bs_notifiers, insert_bs_notifiers;
64 };
65 
66 typedef struct BlockBackendAIOCB {
67     BlockAIOCB common;
68     QEMUBH *bh;
69     BlockBackend *blk;
70     int ret;
71 } BlockBackendAIOCB;
72 
73 static const AIOCBInfo block_backend_aiocb_info = {
74     .get_aio_context = blk_aiocb_get_aio_context,
75     .aiocb_size = sizeof(BlockBackendAIOCB),
76 };
77 
78 static void drive_info_del(DriveInfo *dinfo);
79 static BlockBackend *bdrv_first_blk(BlockDriverState *bs);
80 
81 /* All BlockBackends */
82 static QTAILQ_HEAD(, BlockBackend) block_backends =
83     QTAILQ_HEAD_INITIALIZER(block_backends);
84 
85 /* All BlockBackends referenced by the monitor and which are iterated through by
86  * blk_next() */
87 static QTAILQ_HEAD(, BlockBackend) monitor_block_backends =
88     QTAILQ_HEAD_INITIALIZER(monitor_block_backends);
89 
90 static void blk_root_inherit_options(int *child_flags, QDict *child_options,
91                                      int parent_flags, QDict *parent_options)
92 {
93     /* We're not supposed to call this function for root nodes */
94     abort();
95 }
96 static void blk_root_drained_begin(BdrvChild *child);
97 static void blk_root_drained_end(BdrvChild *child);
98 
99 static void blk_root_change_media(BdrvChild *child, bool load);
100 static void blk_root_resize(BdrvChild *child);
101 
102 static const char *blk_root_get_name(BdrvChild *child)
103 {
104     return blk_name(child->opaque);
105 }
106 
107 static const BdrvChildRole child_root = {
108     .inherit_options    = blk_root_inherit_options,
109 
110     .change_media       = blk_root_change_media,
111     .resize             = blk_root_resize,
112     .get_name           = blk_root_get_name,
113 
114     .drained_begin      = blk_root_drained_begin,
115     .drained_end        = blk_root_drained_end,
116 };
117 
118 /*
119  * Create a new BlockBackend with a reference count of one.
120  * Store an error through @errp on failure, unless it's null.
121  * Return the new BlockBackend on success, null on failure.
122  */
123 BlockBackend *blk_new(void)
124 {
125     BlockBackend *blk;
126 
127     blk = g_new0(BlockBackend, 1);
128     blk->refcnt = 1;
129     blk_set_enable_write_cache(blk, true);
130 
131     qemu_co_queue_init(&blk->public.throttled_reqs[0]);
132     qemu_co_queue_init(&blk->public.throttled_reqs[1]);
133 
134     notifier_list_init(&blk->remove_bs_notifiers);
135     notifier_list_init(&blk->insert_bs_notifiers);
136 
137     QTAILQ_INSERT_TAIL(&block_backends, blk, link);
138     return blk;
139 }
140 
141 /*
142  * Creates a new BlockBackend, opens a new BlockDriverState, and connects both.
143  *
144  * Just as with bdrv_open(), after having called this function the reference to
145  * @options belongs to the block layer (even on failure).
146  *
147  * TODO: Remove @filename and @flags; it should be possible to specify a whole
148  * BDS tree just by specifying the @options QDict (or @reference,
149  * alternatively). At the time of adding this function, this is not possible,
150  * though, so callers of this function have to be able to specify @filename and
151  * @flags.
152  */
153 BlockBackend *blk_new_open(const char *filename, const char *reference,
154                            QDict *options, int flags, Error **errp)
155 {
156     BlockBackend *blk;
157     BlockDriverState *bs;
158 
159     blk = blk_new();
160     bs = bdrv_open(filename, reference, options, flags, errp);
161     if (!bs) {
162         blk_unref(blk);
163         return NULL;
164     }
165 
166     blk->root = bdrv_root_attach_child(bs, "root", &child_root, blk);
167 
168     return blk;
169 }
170 
171 static void blk_delete(BlockBackend *blk)
172 {
173     assert(!blk->refcnt);
174     assert(!blk->name);
175     assert(!blk->dev);
176     if (blk->root) {
177         blk_remove_bs(blk);
178     }
179     assert(QLIST_EMPTY(&blk->remove_bs_notifiers.notifiers));
180     assert(QLIST_EMPTY(&blk->insert_bs_notifiers.notifiers));
181     QTAILQ_REMOVE(&block_backends, blk, link);
182     drive_info_del(blk->legacy_dinfo);
183     block_acct_cleanup(&blk->stats);
184     g_free(blk);
185 }
186 
187 static void drive_info_del(DriveInfo *dinfo)
188 {
189     if (!dinfo) {
190         return;
191     }
192     qemu_opts_del(dinfo->opts);
193     g_free(dinfo->serial);
194     g_free(dinfo);
195 }
196 
197 int blk_get_refcnt(BlockBackend *blk)
198 {
199     return blk ? blk->refcnt : 0;
200 }
201 
202 /*
203  * Increment @blk's reference count.
204  * @blk must not be null.
205  */
206 void blk_ref(BlockBackend *blk)
207 {
208     blk->refcnt++;
209 }
210 
211 /*
212  * Decrement @blk's reference count.
213  * If this drops it to zero, destroy @blk.
214  * For convenience, do nothing if @blk is null.
215  */
216 void blk_unref(BlockBackend *blk)
217 {
218     if (blk) {
219         assert(blk->refcnt > 0);
220         if (!--blk->refcnt) {
221             blk_delete(blk);
222         }
223     }
224 }
225 
226 /*
227  * Behaves similarly to blk_next() but iterates over all BlockBackends, even the
228  * ones which are hidden (i.e. are not referenced by the monitor).
229  */
230 static BlockBackend *blk_all_next(BlockBackend *blk)
231 {
232     return blk ? QTAILQ_NEXT(blk, link)
233                : QTAILQ_FIRST(&block_backends);
234 }
235 
236 void blk_remove_all_bs(void)
237 {
238     BlockBackend *blk = NULL;
239 
240     while ((blk = blk_all_next(blk)) != NULL) {
241         AioContext *ctx = blk_get_aio_context(blk);
242 
243         aio_context_acquire(ctx);
244         if (blk->root) {
245             blk_remove_bs(blk);
246         }
247         aio_context_release(ctx);
248     }
249 }
250 
251 /*
252  * Return the monitor-owned BlockBackend after @blk.
253  * If @blk is null, return the first one.
254  * Else, return @blk's next sibling, which may be null.
255  *
256  * To iterate over all BlockBackends, do
257  * for (blk = blk_next(NULL); blk; blk = blk_next(blk)) {
258  *     ...
259  * }
260  */
261 BlockBackend *blk_next(BlockBackend *blk)
262 {
263     return blk ? QTAILQ_NEXT(blk, monitor_link)
264                : QTAILQ_FIRST(&monitor_block_backends);
265 }
266 
267 /* Iterates over all top-level BlockDriverStates, i.e. BDSs that are owned by
268  * the monitor or attached to a BlockBackend */
269 BlockDriverState *bdrv_next(BdrvNextIterator *it)
270 {
271     BlockDriverState *bs;
272 
273     /* First, return all root nodes of BlockBackends. In order to avoid
274      * returning a BDS twice when multiple BBs refer to it, we only return it
275      * if the BB is the first one in the parent list of the BDS. */
276     if (it->phase == BDRV_NEXT_BACKEND_ROOTS) {
277         do {
278             it->blk = blk_all_next(it->blk);
279             bs = it->blk ? blk_bs(it->blk) : NULL;
280         } while (it->blk && (bs == NULL || bdrv_first_blk(bs) != it->blk));
281 
282         if (bs) {
283             return bs;
284         }
285         it->phase = BDRV_NEXT_MONITOR_OWNED;
286     }
287 
288     /* Then return the monitor-owned BDSes without a BB attached. Ignore all
289      * BDSes that are attached to a BlockBackend here; they have been handled
290      * by the above block already */
291     do {
292         it->bs = bdrv_next_monitor_owned(it->bs);
293         bs = it->bs;
294     } while (bs && bdrv_has_blk(bs));
295 
296     return bs;
297 }
298 
299 BlockDriverState *bdrv_first(BdrvNextIterator *it)
300 {
301     *it = (BdrvNextIterator) {
302         .phase = BDRV_NEXT_BACKEND_ROOTS,
303     };
304 
305     return bdrv_next(it);
306 }
307 
308 /*
309  * Add a BlockBackend into the list of backends referenced by the monitor, with
310  * the given @name acting as the handle for the monitor.
311  * Strictly for use by blockdev.c.
312  *
313  * @name must not be null or empty.
314  *
315  * Returns true on success and false on failure. In the latter case, an Error
316  * object is returned through @errp.
317  */
318 bool monitor_add_blk(BlockBackend *blk, const char *name, Error **errp)
319 {
320     assert(!blk->name);
321     assert(name && name[0]);
322 
323     if (!id_wellformed(name)) {
324         error_setg(errp, "Invalid device name");
325         return false;
326     }
327     if (blk_by_name(name)) {
328         error_setg(errp, "Device with id '%s' already exists", name);
329         return false;
330     }
331     if (bdrv_find_node(name)) {
332         error_setg(errp,
333                    "Device name '%s' conflicts with an existing node name",
334                    name);
335         return false;
336     }
337 
338     blk->name = g_strdup(name);
339     QTAILQ_INSERT_TAIL(&monitor_block_backends, blk, monitor_link);
340     return true;
341 }
342 
343 /*
344  * Remove a BlockBackend from the list of backends referenced by the monitor.
345  * Strictly for use by blockdev.c.
346  */
347 void monitor_remove_blk(BlockBackend *blk)
348 {
349     if (!blk->name) {
350         return;
351     }
352 
353     QTAILQ_REMOVE(&monitor_block_backends, blk, monitor_link);
354     g_free(blk->name);
355     blk->name = NULL;
356 }
357 
358 /*
359  * Return @blk's name, a non-null string.
360  * Returns an empty string iff @blk is not referenced by the monitor.
361  */
362 const char *blk_name(BlockBackend *blk)
363 {
364     return blk->name ?: "";
365 }
366 
367 /*
368  * Return the BlockBackend with name @name if it exists, else null.
369  * @name must not be null.
370  */
371 BlockBackend *blk_by_name(const char *name)
372 {
373     BlockBackend *blk = NULL;
374 
375     assert(name);
376     while ((blk = blk_next(blk)) != NULL) {
377         if (!strcmp(name, blk->name)) {
378             return blk;
379         }
380     }
381     return NULL;
382 }
383 
384 /*
385  * Return the BlockDriverState attached to @blk if any, else null.
386  */
387 BlockDriverState *blk_bs(BlockBackend *blk)
388 {
389     return blk->root ? blk->root->bs : NULL;
390 }
391 
392 static BlockBackend *bdrv_first_blk(BlockDriverState *bs)
393 {
394     BdrvChild *child;
395     QLIST_FOREACH(child, &bs->parents, next_parent) {
396         if (child->role == &child_root) {
397             return child->opaque;
398         }
399     }
400 
401     return NULL;
402 }
403 
404 /*
405  * Returns true if @bs has an associated BlockBackend.
406  */
407 bool bdrv_has_blk(BlockDriverState *bs)
408 {
409     return bdrv_first_blk(bs) != NULL;
410 }
411 
412 /*
413  * Returns true if @bs has only BlockBackends as parents.
414  */
415 bool bdrv_is_root_node(BlockDriverState *bs)
416 {
417     BdrvChild *c;
418 
419     QLIST_FOREACH(c, &bs->parents, next_parent) {
420         if (c->role != &child_root) {
421             return false;
422         }
423     }
424 
425     return true;
426 }
427 
428 /*
429  * Return @blk's DriveInfo if any, else null.
430  */
431 DriveInfo *blk_legacy_dinfo(BlockBackend *blk)
432 {
433     return blk->legacy_dinfo;
434 }
435 
436 /*
437  * Set @blk's DriveInfo to @dinfo, and return it.
438  * @blk must not have a DriveInfo set already.
439  * No other BlockBackend may have the same DriveInfo set.
440  */
441 DriveInfo *blk_set_legacy_dinfo(BlockBackend *blk, DriveInfo *dinfo)
442 {
443     assert(!blk->legacy_dinfo);
444     return blk->legacy_dinfo = dinfo;
445 }
446 
447 /*
448  * Return the BlockBackend with DriveInfo @dinfo.
449  * It must exist.
450  */
451 BlockBackend *blk_by_legacy_dinfo(DriveInfo *dinfo)
452 {
453     BlockBackend *blk = NULL;
454 
455     while ((blk = blk_next(blk)) != NULL) {
456         if (blk->legacy_dinfo == dinfo) {
457             return blk;
458         }
459     }
460     abort();
461 }
462 
463 /*
464  * Returns a pointer to the publicly accessible fields of @blk.
465  */
466 BlockBackendPublic *blk_get_public(BlockBackend *blk)
467 {
468     return &blk->public;
469 }
470 
471 /*
472  * Returns a BlockBackend given the associated @public fields.
473  */
474 BlockBackend *blk_by_public(BlockBackendPublic *public)
475 {
476     return container_of(public, BlockBackend, public);
477 }
478 
479 /*
480  * Disassociates the currently associated BlockDriverState from @blk.
481  */
482 void blk_remove_bs(BlockBackend *blk)
483 {
484     notifier_list_notify(&blk->remove_bs_notifiers, blk);
485     if (blk->public.throttle_state) {
486         throttle_timers_detach_aio_context(&blk->public.throttle_timers);
487     }
488 
489     blk_update_root_state(blk);
490 
491     bdrv_root_unref_child(blk->root);
492     blk->root = NULL;
493 }
494 
495 /*
496  * Associates a new BlockDriverState with @blk.
497  */
498 void blk_insert_bs(BlockBackend *blk, BlockDriverState *bs)
499 {
500     bdrv_ref(bs);
501     blk->root = bdrv_root_attach_child(bs, "root", &child_root, blk);
502 
503     notifier_list_notify(&blk->insert_bs_notifiers, blk);
504     if (blk->public.throttle_state) {
505         throttle_timers_attach_aio_context(
506             &blk->public.throttle_timers, bdrv_get_aio_context(bs));
507     }
508 }
509 
510 /*
511  * Attach device model @dev to @blk.
512  * Return 0 on success, -EBUSY when a device model is attached already.
513  */
514 int blk_attach_dev(BlockBackend *blk, void *dev)
515 /* TODO change to DeviceState *dev when all users are qdevified */
516 {
517     if (blk->dev) {
518         return -EBUSY;
519     }
520     blk_ref(blk);
521     blk->dev = dev;
522     blk_iostatus_reset(blk);
523     return 0;
524 }
525 
526 /*
527  * Attach device model @dev to @blk.
528  * @blk must not have a device model attached already.
529  * TODO qdevified devices don't use this, remove when devices are qdevified
530  */
531 void blk_attach_dev_nofail(BlockBackend *blk, void *dev)
532 {
533     if (blk_attach_dev(blk, dev) < 0) {
534         abort();
535     }
536 }
537 
538 /*
539  * Detach device model @dev from @blk.
540  * @dev must be currently attached to @blk.
541  */
542 void blk_detach_dev(BlockBackend *blk, void *dev)
543 /* TODO change to DeviceState *dev when all users are qdevified */
544 {
545     assert(blk->dev == dev);
546     blk->dev = NULL;
547     blk->dev_ops = NULL;
548     blk->dev_opaque = NULL;
549     blk->guest_block_size = 512;
550     blk_unref(blk);
551 }
552 
553 /*
554  * Return the device model attached to @blk if any, else null.
555  */
556 void *blk_get_attached_dev(BlockBackend *blk)
557 /* TODO change to return DeviceState * when all users are qdevified */
558 {
559     return blk->dev;
560 }
561 
562 /*
563  * Return the BlockBackend which has the device model @dev attached if it
564  * exists, else null.
565  *
566  * @dev must not be null.
567  */
568 BlockBackend *blk_by_dev(void *dev)
569 {
570     BlockBackend *blk = NULL;
571 
572     assert(dev != NULL);
573     while ((blk = blk_all_next(blk)) != NULL) {
574         if (blk->dev == dev) {
575             return blk;
576         }
577     }
578     return NULL;
579 }
580 
581 /*
582  * Set @blk's device model callbacks to @ops.
583  * @opaque is the opaque argument to pass to the callbacks.
584  * This is for use by device models.
585  */
586 void blk_set_dev_ops(BlockBackend *blk, const BlockDevOps *ops,
587                      void *opaque)
588 {
589     blk->dev_ops = ops;
590     blk->dev_opaque = opaque;
591 }
592 
593 /*
594  * Notify @blk's attached device model of media change.
595  * If @load is true, notify of media load.
596  * Else, notify of media eject.
597  * Also send DEVICE_TRAY_MOVED events as appropriate.
598  */
599 void blk_dev_change_media_cb(BlockBackend *blk, bool load)
600 {
601     if (blk->dev_ops && blk->dev_ops->change_media_cb) {
602         bool tray_was_open, tray_is_open;
603 
604         tray_was_open = blk_dev_is_tray_open(blk);
605         blk->dev_ops->change_media_cb(blk->dev_opaque, load);
606         tray_is_open = blk_dev_is_tray_open(blk);
607 
608         if (tray_was_open != tray_is_open) {
609             qapi_event_send_device_tray_moved(blk_name(blk), tray_is_open,
610                                               &error_abort);
611         }
612     }
613 }
614 
615 static void blk_root_change_media(BdrvChild *child, bool load)
616 {
617     blk_dev_change_media_cb(child->opaque, load);
618 }
619 
620 /*
621  * Does @blk's attached device model have removable media?
622  * %true if no device model is attached.
623  */
624 bool blk_dev_has_removable_media(BlockBackend *blk)
625 {
626     return !blk->dev || (blk->dev_ops && blk->dev_ops->change_media_cb);
627 }
628 
629 /*
630  * Does @blk's attached device model have a tray?
631  */
632 bool blk_dev_has_tray(BlockBackend *blk)
633 {
634     return blk->dev_ops && blk->dev_ops->is_tray_open;
635 }
636 
637 /*
638  * Notify @blk's attached device model of a media eject request.
639  * If @force is true, the medium is about to be yanked out forcefully.
640  */
641 void blk_dev_eject_request(BlockBackend *blk, bool force)
642 {
643     if (blk->dev_ops && blk->dev_ops->eject_request_cb) {
644         blk->dev_ops->eject_request_cb(blk->dev_opaque, force);
645     }
646 }
647 
648 /*
649  * Does @blk's attached device model have a tray, and is it open?
650  */
651 bool blk_dev_is_tray_open(BlockBackend *blk)
652 {
653     if (blk_dev_has_tray(blk)) {
654         return blk->dev_ops->is_tray_open(blk->dev_opaque);
655     }
656     return false;
657 }
658 
659 /*
660  * Does @blk's attached device model have the medium locked?
661  * %false if the device model has no such lock.
662  */
663 bool blk_dev_is_medium_locked(BlockBackend *blk)
664 {
665     if (blk->dev_ops && blk->dev_ops->is_medium_locked) {
666         return blk->dev_ops->is_medium_locked(blk->dev_opaque);
667     }
668     return false;
669 }
670 
671 /*
672  * Notify @blk's attached device model of a backend size change.
673  */
674 static void blk_root_resize(BdrvChild *child)
675 {
676     BlockBackend *blk = child->opaque;
677 
678     if (blk->dev_ops && blk->dev_ops->resize_cb) {
679         blk->dev_ops->resize_cb(blk->dev_opaque);
680     }
681 }
682 
683 void blk_iostatus_enable(BlockBackend *blk)
684 {
685     blk->iostatus_enabled = true;
686     blk->iostatus = BLOCK_DEVICE_IO_STATUS_OK;
687 }
688 
689 /* The I/O status is only enabled if the drive explicitly
690  * enables it _and_ the VM is configured to stop on errors */
691 bool blk_iostatus_is_enabled(const BlockBackend *blk)
692 {
693     return (blk->iostatus_enabled &&
694            (blk->on_write_error == BLOCKDEV_ON_ERROR_ENOSPC ||
695             blk->on_write_error == BLOCKDEV_ON_ERROR_STOP   ||
696             blk->on_read_error == BLOCKDEV_ON_ERROR_STOP));
697 }
698 
699 BlockDeviceIoStatus blk_iostatus(const BlockBackend *blk)
700 {
701     return blk->iostatus;
702 }
703 
704 void blk_iostatus_disable(BlockBackend *blk)
705 {
706     blk->iostatus_enabled = false;
707 }
708 
709 void blk_iostatus_reset(BlockBackend *blk)
710 {
711     if (blk_iostatus_is_enabled(blk)) {
712         BlockDriverState *bs = blk_bs(blk);
713         blk->iostatus = BLOCK_DEVICE_IO_STATUS_OK;
714         if (bs && bs->job) {
715             block_job_iostatus_reset(bs->job);
716         }
717     }
718 }
719 
720 void blk_iostatus_set_err(BlockBackend *blk, int error)
721 {
722     assert(blk_iostatus_is_enabled(blk));
723     if (blk->iostatus == BLOCK_DEVICE_IO_STATUS_OK) {
724         blk->iostatus = error == ENOSPC ? BLOCK_DEVICE_IO_STATUS_NOSPACE :
725                                           BLOCK_DEVICE_IO_STATUS_FAILED;
726     }
727 }
728 
729 void blk_set_allow_write_beyond_eof(BlockBackend *blk, bool allow)
730 {
731     blk->allow_write_beyond_eof = allow;
732 }
733 
734 static int blk_check_byte_request(BlockBackend *blk, int64_t offset,
735                                   size_t size)
736 {
737     int64_t len;
738 
739     if (size > INT_MAX) {
740         return -EIO;
741     }
742 
743     if (!blk_is_available(blk)) {
744         return -ENOMEDIUM;
745     }
746 
747     if (offset < 0) {
748         return -EIO;
749     }
750 
751     if (!blk->allow_write_beyond_eof) {
752         len = blk_getlength(blk);
753         if (len < 0) {
754             return len;
755         }
756 
757         if (offset > len || len - offset < size) {
758             return -EIO;
759         }
760     }
761 
762     return 0;
763 }
764 
765 int coroutine_fn blk_co_preadv(BlockBackend *blk, int64_t offset,
766                                unsigned int bytes, QEMUIOVector *qiov,
767                                BdrvRequestFlags flags)
768 {
769     int ret;
770 
771     trace_blk_co_preadv(blk, blk_bs(blk), offset, bytes, flags);
772 
773     ret = blk_check_byte_request(blk, offset, bytes);
774     if (ret < 0) {
775         return ret;
776     }
777 
778     /* throttling disk I/O */
779     if (blk->public.throttle_state) {
780         throttle_group_co_io_limits_intercept(blk, bytes, false);
781     }
782 
783     return bdrv_co_preadv(blk->root, offset, bytes, qiov, flags);
784 }
785 
786 int coroutine_fn blk_co_pwritev(BlockBackend *blk, int64_t offset,
787                                 unsigned int bytes, QEMUIOVector *qiov,
788                                 BdrvRequestFlags flags)
789 {
790     int ret;
791 
792     trace_blk_co_pwritev(blk, blk_bs(blk), offset, bytes, flags);
793 
794     ret = blk_check_byte_request(blk, offset, bytes);
795     if (ret < 0) {
796         return ret;
797     }
798 
799     /* throttling disk I/O */
800     if (blk->public.throttle_state) {
801         throttle_group_co_io_limits_intercept(blk, bytes, true);
802     }
803 
804     if (!blk->enable_write_cache) {
805         flags |= BDRV_REQ_FUA;
806     }
807 
808     return bdrv_co_pwritev(blk->root, offset, bytes, qiov, flags);
809 }
810 
811 typedef struct BlkRwCo {
812     BlockBackend *blk;
813     int64_t offset;
814     QEMUIOVector *qiov;
815     int ret;
816     BdrvRequestFlags flags;
817 } BlkRwCo;
818 
819 static void blk_read_entry(void *opaque)
820 {
821     BlkRwCo *rwco = opaque;
822 
823     rwco->ret = blk_co_preadv(rwco->blk, rwco->offset, rwco->qiov->size,
824                               rwco->qiov, rwco->flags);
825 }
826 
827 static void blk_write_entry(void *opaque)
828 {
829     BlkRwCo *rwco = opaque;
830 
831     rwco->ret = blk_co_pwritev(rwco->blk, rwco->offset, rwco->qiov->size,
832                                rwco->qiov, rwco->flags);
833 }
834 
835 static int blk_prw(BlockBackend *blk, int64_t offset, uint8_t *buf,
836                    int64_t bytes, CoroutineEntry co_entry,
837                    BdrvRequestFlags flags)
838 {
839     AioContext *aio_context;
840     QEMUIOVector qiov;
841     struct iovec iov;
842     Coroutine *co;
843     BlkRwCo rwco;
844 
845     iov = (struct iovec) {
846         .iov_base = buf,
847         .iov_len = bytes,
848     };
849     qemu_iovec_init_external(&qiov, &iov, 1);
850 
851     rwco = (BlkRwCo) {
852         .blk    = blk,
853         .offset = offset,
854         .qiov   = &qiov,
855         .flags  = flags,
856         .ret    = NOT_DONE,
857     };
858 
859     co = qemu_coroutine_create(co_entry, &rwco);
860     qemu_coroutine_enter(co);
861 
862     aio_context = blk_get_aio_context(blk);
863     while (rwco.ret == NOT_DONE) {
864         aio_poll(aio_context, true);
865     }
866 
867     return rwco.ret;
868 }
869 
870 int blk_pread_unthrottled(BlockBackend *blk, int64_t offset, uint8_t *buf,
871                           int count)
872 {
873     int ret;
874 
875     ret = blk_check_byte_request(blk, offset, count);
876     if (ret < 0) {
877         return ret;
878     }
879 
880     blk_root_drained_begin(blk->root);
881     ret = blk_pread(blk, offset, buf, count);
882     blk_root_drained_end(blk->root);
883     return ret;
884 }
885 
886 int blk_pwrite_zeroes(BlockBackend *blk, int64_t offset,
887                       int count, BdrvRequestFlags flags)
888 {
889     return blk_prw(blk, offset, NULL, count, blk_write_entry,
890                    flags | BDRV_REQ_ZERO_WRITE);
891 }
892 
893 int blk_make_zero(BlockBackend *blk, BdrvRequestFlags flags)
894 {
895     return bdrv_make_zero(blk->root, flags);
896 }
897 
898 static void error_callback_bh(void *opaque)
899 {
900     struct BlockBackendAIOCB *acb = opaque;
901     qemu_bh_delete(acb->bh);
902     acb->common.cb(acb->common.opaque, acb->ret);
903     qemu_aio_unref(acb);
904 }
905 
906 BlockAIOCB *blk_abort_aio_request(BlockBackend *blk,
907                                   BlockCompletionFunc *cb,
908                                   void *opaque, int ret)
909 {
910     struct BlockBackendAIOCB *acb;
911     QEMUBH *bh;
912 
913     acb = blk_aio_get(&block_backend_aiocb_info, blk, cb, opaque);
914     acb->blk = blk;
915     acb->ret = ret;
916 
917     bh = aio_bh_new(blk_get_aio_context(blk), error_callback_bh, acb);
918     acb->bh = bh;
919     qemu_bh_schedule(bh);
920 
921     return &acb->common;
922 }
923 
924 typedef struct BlkAioEmAIOCB {
925     BlockAIOCB common;
926     BlkRwCo rwco;
927     int bytes;
928     bool has_returned;
929     QEMUBH* bh;
930 } BlkAioEmAIOCB;
931 
932 static const AIOCBInfo blk_aio_em_aiocb_info = {
933     .aiocb_size         = sizeof(BlkAioEmAIOCB),
934 };
935 
936 static void blk_aio_complete(BlkAioEmAIOCB *acb)
937 {
938     if (acb->bh) {
939         assert(acb->has_returned);
940         qemu_bh_delete(acb->bh);
941     }
942     if (acb->has_returned) {
943         acb->common.cb(acb->common.opaque, acb->rwco.ret);
944         qemu_aio_unref(acb);
945     }
946 }
947 
948 static void blk_aio_complete_bh(void *opaque)
949 {
950     blk_aio_complete(opaque);
951 }
952 
953 static BlockAIOCB *blk_aio_prwv(BlockBackend *blk, int64_t offset, int bytes,
954                                 QEMUIOVector *qiov, CoroutineEntry co_entry,
955                                 BdrvRequestFlags flags,
956                                 BlockCompletionFunc *cb, void *opaque)
957 {
958     BlkAioEmAIOCB *acb;
959     Coroutine *co;
960 
961     acb = blk_aio_get(&blk_aio_em_aiocb_info, blk, cb, opaque);
962     acb->rwco = (BlkRwCo) {
963         .blk    = blk,
964         .offset = offset,
965         .qiov   = qiov,
966         .flags  = flags,
967         .ret    = NOT_DONE,
968     };
969     acb->bytes = bytes;
970     acb->bh = NULL;
971     acb->has_returned = false;
972 
973     co = qemu_coroutine_create(co_entry, acb);
974     qemu_coroutine_enter(co);
975 
976     acb->has_returned = true;
977     if (acb->rwco.ret != NOT_DONE) {
978         acb->bh = aio_bh_new(blk_get_aio_context(blk), blk_aio_complete_bh, acb);
979         qemu_bh_schedule(acb->bh);
980     }
981 
982     return &acb->common;
983 }
984 
985 static void blk_aio_read_entry(void *opaque)
986 {
987     BlkAioEmAIOCB *acb = opaque;
988     BlkRwCo *rwco = &acb->rwco;
989 
990     assert(rwco->qiov->size == acb->bytes);
991     rwco->ret = blk_co_preadv(rwco->blk, rwco->offset, acb->bytes,
992                               rwco->qiov, rwco->flags);
993     blk_aio_complete(acb);
994 }
995 
996 static void blk_aio_write_entry(void *opaque)
997 {
998     BlkAioEmAIOCB *acb = opaque;
999     BlkRwCo *rwco = &acb->rwco;
1000 
1001     assert(!rwco->qiov || rwco->qiov->size == acb->bytes);
1002     rwco->ret = blk_co_pwritev(rwco->blk, rwco->offset, acb->bytes,
1003                                rwco->qiov, rwco->flags);
1004     blk_aio_complete(acb);
1005 }
1006 
1007 BlockAIOCB *blk_aio_pwrite_zeroes(BlockBackend *blk, int64_t offset,
1008                                   int count, BdrvRequestFlags flags,
1009                                   BlockCompletionFunc *cb, void *opaque)
1010 {
1011     return blk_aio_prwv(blk, offset, count, NULL, blk_aio_write_entry,
1012                         flags | BDRV_REQ_ZERO_WRITE, cb, opaque);
1013 }
1014 
1015 int blk_pread(BlockBackend *blk, int64_t offset, void *buf, int count)
1016 {
1017     int ret = blk_prw(blk, offset, buf, count, blk_read_entry, 0);
1018     if (ret < 0) {
1019         return ret;
1020     }
1021     return count;
1022 }
1023 
1024 int blk_pwrite(BlockBackend *blk, int64_t offset, const void *buf, int count,
1025                BdrvRequestFlags flags)
1026 {
1027     int ret = blk_prw(blk, offset, (void *) buf, count, blk_write_entry,
1028                       flags);
1029     if (ret < 0) {
1030         return ret;
1031     }
1032     return count;
1033 }
1034 
1035 int64_t blk_getlength(BlockBackend *blk)
1036 {
1037     if (!blk_is_available(blk)) {
1038         return -ENOMEDIUM;
1039     }
1040 
1041     return bdrv_getlength(blk_bs(blk));
1042 }
1043 
1044 void blk_get_geometry(BlockBackend *blk, uint64_t *nb_sectors_ptr)
1045 {
1046     if (!blk_bs(blk)) {
1047         *nb_sectors_ptr = 0;
1048     } else {
1049         bdrv_get_geometry(blk_bs(blk), nb_sectors_ptr);
1050     }
1051 }
1052 
1053 int64_t blk_nb_sectors(BlockBackend *blk)
1054 {
1055     if (!blk_is_available(blk)) {
1056         return -ENOMEDIUM;
1057     }
1058 
1059     return bdrv_nb_sectors(blk_bs(blk));
1060 }
1061 
1062 BlockAIOCB *blk_aio_preadv(BlockBackend *blk, int64_t offset,
1063                            QEMUIOVector *qiov, BdrvRequestFlags flags,
1064                            BlockCompletionFunc *cb, void *opaque)
1065 {
1066     return blk_aio_prwv(blk, offset, qiov->size, qiov,
1067                         blk_aio_read_entry, flags, cb, opaque);
1068 }
1069 
1070 BlockAIOCB *blk_aio_pwritev(BlockBackend *blk, int64_t offset,
1071                             QEMUIOVector *qiov, BdrvRequestFlags flags,
1072                             BlockCompletionFunc *cb, void *opaque)
1073 {
1074     return blk_aio_prwv(blk, offset, qiov->size, qiov,
1075                         blk_aio_write_entry, flags, cb, opaque);
1076 }
1077 
1078 BlockAIOCB *blk_aio_flush(BlockBackend *blk,
1079                           BlockCompletionFunc *cb, void *opaque)
1080 {
1081     if (!blk_is_available(blk)) {
1082         return blk_abort_aio_request(blk, cb, opaque, -ENOMEDIUM);
1083     }
1084 
1085     return bdrv_aio_flush(blk_bs(blk), cb, opaque);
1086 }
1087 
1088 BlockAIOCB *blk_aio_pdiscard(BlockBackend *blk,
1089                              int64_t offset, int count,
1090                              BlockCompletionFunc *cb, void *opaque)
1091 {
1092     int ret = blk_check_byte_request(blk, offset, count);
1093     if (ret < 0) {
1094         return blk_abort_aio_request(blk, cb, opaque, ret);
1095     }
1096 
1097     return bdrv_aio_pdiscard(blk_bs(blk), offset, count, cb, opaque);
1098 }
1099 
1100 void blk_aio_cancel(BlockAIOCB *acb)
1101 {
1102     bdrv_aio_cancel(acb);
1103 }
1104 
1105 void blk_aio_cancel_async(BlockAIOCB *acb)
1106 {
1107     bdrv_aio_cancel_async(acb);
1108 }
1109 
1110 int blk_ioctl(BlockBackend *blk, unsigned long int req, void *buf)
1111 {
1112     if (!blk_is_available(blk)) {
1113         return -ENOMEDIUM;
1114     }
1115 
1116     return bdrv_ioctl(blk_bs(blk), req, buf);
1117 }
1118 
1119 BlockAIOCB *blk_aio_ioctl(BlockBackend *blk, unsigned long int req, void *buf,
1120                           BlockCompletionFunc *cb, void *opaque)
1121 {
1122     if (!blk_is_available(blk)) {
1123         return blk_abort_aio_request(blk, cb, opaque, -ENOMEDIUM);
1124     }
1125 
1126     return bdrv_aio_ioctl(blk_bs(blk), req, buf, cb, opaque);
1127 }
1128 
1129 int blk_co_pdiscard(BlockBackend *blk, int64_t offset, int count)
1130 {
1131     int ret = blk_check_byte_request(blk, offset, count);
1132     if (ret < 0) {
1133         return ret;
1134     }
1135 
1136     return bdrv_co_pdiscard(blk_bs(blk), offset, count);
1137 }
1138 
1139 int blk_co_flush(BlockBackend *blk)
1140 {
1141     if (!blk_is_available(blk)) {
1142         return -ENOMEDIUM;
1143     }
1144 
1145     return bdrv_co_flush(blk_bs(blk));
1146 }
1147 
1148 int blk_flush(BlockBackend *blk)
1149 {
1150     if (!blk_is_available(blk)) {
1151         return -ENOMEDIUM;
1152     }
1153 
1154     return bdrv_flush(blk_bs(blk));
1155 }
1156 
1157 void blk_drain(BlockBackend *blk)
1158 {
1159     if (blk_bs(blk)) {
1160         bdrv_drain(blk_bs(blk));
1161     }
1162 }
1163 
1164 void blk_drain_all(void)
1165 {
1166     bdrv_drain_all();
1167 }
1168 
1169 void blk_set_on_error(BlockBackend *blk, BlockdevOnError on_read_error,
1170                       BlockdevOnError on_write_error)
1171 {
1172     blk->on_read_error = on_read_error;
1173     blk->on_write_error = on_write_error;
1174 }
1175 
1176 BlockdevOnError blk_get_on_error(BlockBackend *blk, bool is_read)
1177 {
1178     return is_read ? blk->on_read_error : blk->on_write_error;
1179 }
1180 
1181 BlockErrorAction blk_get_error_action(BlockBackend *blk, bool is_read,
1182                                       int error)
1183 {
1184     BlockdevOnError on_err = blk_get_on_error(blk, is_read);
1185 
1186     switch (on_err) {
1187     case BLOCKDEV_ON_ERROR_ENOSPC:
1188         return (error == ENOSPC) ?
1189                BLOCK_ERROR_ACTION_STOP : BLOCK_ERROR_ACTION_REPORT;
1190     case BLOCKDEV_ON_ERROR_STOP:
1191         return BLOCK_ERROR_ACTION_STOP;
1192     case BLOCKDEV_ON_ERROR_REPORT:
1193         return BLOCK_ERROR_ACTION_REPORT;
1194     case BLOCKDEV_ON_ERROR_IGNORE:
1195         return BLOCK_ERROR_ACTION_IGNORE;
1196     case BLOCKDEV_ON_ERROR_AUTO:
1197     default:
1198         abort();
1199     }
1200 }
1201 
1202 static void send_qmp_error_event(BlockBackend *blk,
1203                                  BlockErrorAction action,
1204                                  bool is_read, int error)
1205 {
1206     IoOperationType optype;
1207 
1208     optype = is_read ? IO_OPERATION_TYPE_READ : IO_OPERATION_TYPE_WRITE;
1209     qapi_event_send_block_io_error(blk_name(blk), optype, action,
1210                                    blk_iostatus_is_enabled(blk),
1211                                    error == ENOSPC, strerror(error),
1212                                    &error_abort);
1213 }
1214 
1215 /* This is done by device models because, while the block layer knows
1216  * about the error, it does not know whether an operation comes from
1217  * the device or the block layer (from a job, for example).
1218  */
1219 void blk_error_action(BlockBackend *blk, BlockErrorAction action,
1220                       bool is_read, int error)
1221 {
1222     assert(error >= 0);
1223 
1224     if (action == BLOCK_ERROR_ACTION_STOP) {
1225         /* First set the iostatus, so that "info block" returns an iostatus
1226          * that matches the events raised so far (an additional error iostatus
1227          * is fine, but not a lost one).
1228          */
1229         blk_iostatus_set_err(blk, error);
1230 
1231         /* Then raise the request to stop the VM and the event.
1232          * qemu_system_vmstop_request_prepare has two effects.  First,
1233          * it ensures that the STOP event always comes after the
1234          * BLOCK_IO_ERROR event.  Second, it ensures that even if management
1235          * can observe the STOP event and do a "cont" before the STOP
1236          * event is issued, the VM will not stop.  In this case, vm_start()
1237          * also ensures that the STOP/RESUME pair of events is emitted.
1238          */
1239         qemu_system_vmstop_request_prepare();
1240         send_qmp_error_event(blk, action, is_read, error);
1241         qemu_system_vmstop_request(RUN_STATE_IO_ERROR);
1242     } else {
1243         send_qmp_error_event(blk, action, is_read, error);
1244     }
1245 }
1246 
1247 int blk_is_read_only(BlockBackend *blk)
1248 {
1249     BlockDriverState *bs = blk_bs(blk);
1250 
1251     if (bs) {
1252         return bdrv_is_read_only(bs);
1253     } else {
1254         return blk->root_state.read_only;
1255     }
1256 }
1257 
1258 int blk_is_sg(BlockBackend *blk)
1259 {
1260     BlockDriverState *bs = blk_bs(blk);
1261 
1262     if (!bs) {
1263         return 0;
1264     }
1265 
1266     return bdrv_is_sg(bs);
1267 }
1268 
1269 int blk_enable_write_cache(BlockBackend *blk)
1270 {
1271     return blk->enable_write_cache;
1272 }
1273 
1274 void blk_set_enable_write_cache(BlockBackend *blk, bool wce)
1275 {
1276     blk->enable_write_cache = wce;
1277 }
1278 
1279 void blk_invalidate_cache(BlockBackend *blk, Error **errp)
1280 {
1281     BlockDriverState *bs = blk_bs(blk);
1282 
1283     if (!bs) {
1284         error_setg(errp, "Device '%s' has no medium", blk->name);
1285         return;
1286     }
1287 
1288     bdrv_invalidate_cache(bs, errp);
1289 }
1290 
1291 bool blk_is_inserted(BlockBackend *blk)
1292 {
1293     BlockDriverState *bs = blk_bs(blk);
1294 
1295     return bs && bdrv_is_inserted(bs);
1296 }
1297 
1298 bool blk_is_available(BlockBackend *blk)
1299 {
1300     return blk_is_inserted(blk) && !blk_dev_is_tray_open(blk);
1301 }
1302 
1303 void blk_lock_medium(BlockBackend *blk, bool locked)
1304 {
1305     BlockDriverState *bs = blk_bs(blk);
1306 
1307     if (bs) {
1308         bdrv_lock_medium(bs, locked);
1309     }
1310 }
1311 
1312 void blk_eject(BlockBackend *blk, bool eject_flag)
1313 {
1314     BlockDriverState *bs = blk_bs(blk);
1315 
1316     if (bs) {
1317         bdrv_eject(bs, eject_flag);
1318     }
1319 }
1320 
1321 int blk_get_flags(BlockBackend *blk)
1322 {
1323     BlockDriverState *bs = blk_bs(blk);
1324 
1325     if (bs) {
1326         return bdrv_get_flags(bs);
1327     } else {
1328         return blk->root_state.open_flags;
1329     }
1330 }
1331 
1332 /* Returns the maximum transfer length, in bytes; guaranteed nonzero */
1333 uint32_t blk_get_max_transfer(BlockBackend *blk)
1334 {
1335     BlockDriverState *bs = blk_bs(blk);
1336     uint32_t max = 0;
1337 
1338     if (bs) {
1339         max = bs->bl.max_transfer;
1340     }
1341     return MIN_NON_ZERO(max, INT_MAX);
1342 }
1343 
1344 int blk_get_max_iov(BlockBackend *blk)
1345 {
1346     return blk->root->bs->bl.max_iov;
1347 }
1348 
1349 void blk_set_guest_block_size(BlockBackend *blk, int align)
1350 {
1351     blk->guest_block_size = align;
1352 }
1353 
1354 void *blk_try_blockalign(BlockBackend *blk, size_t size)
1355 {
1356     return qemu_try_blockalign(blk ? blk_bs(blk) : NULL, size);
1357 }
1358 
1359 void *blk_blockalign(BlockBackend *blk, size_t size)
1360 {
1361     return qemu_blockalign(blk ? blk_bs(blk) : NULL, size);
1362 }
1363 
1364 bool blk_op_is_blocked(BlockBackend *blk, BlockOpType op, Error **errp)
1365 {
1366     BlockDriverState *bs = blk_bs(blk);
1367 
1368     if (!bs) {
1369         return false;
1370     }
1371 
1372     return bdrv_op_is_blocked(bs, op, errp);
1373 }
1374 
1375 void blk_op_unblock(BlockBackend *blk, BlockOpType op, Error *reason)
1376 {
1377     BlockDriverState *bs = blk_bs(blk);
1378 
1379     if (bs) {
1380         bdrv_op_unblock(bs, op, reason);
1381     }
1382 }
1383 
1384 void blk_op_block_all(BlockBackend *blk, Error *reason)
1385 {
1386     BlockDriverState *bs = blk_bs(blk);
1387 
1388     if (bs) {
1389         bdrv_op_block_all(bs, reason);
1390     }
1391 }
1392 
1393 void blk_op_unblock_all(BlockBackend *blk, Error *reason)
1394 {
1395     BlockDriverState *bs = blk_bs(blk);
1396 
1397     if (bs) {
1398         bdrv_op_unblock_all(bs, reason);
1399     }
1400 }
1401 
1402 AioContext *blk_get_aio_context(BlockBackend *blk)
1403 {
1404     BlockDriverState *bs = blk_bs(blk);
1405 
1406     if (bs) {
1407         return bdrv_get_aio_context(bs);
1408     } else {
1409         return qemu_get_aio_context();
1410     }
1411 }
1412 
1413 static AioContext *blk_aiocb_get_aio_context(BlockAIOCB *acb)
1414 {
1415     BlockBackendAIOCB *blk_acb = DO_UPCAST(BlockBackendAIOCB, common, acb);
1416     return blk_get_aio_context(blk_acb->blk);
1417 }
1418 
1419 void blk_set_aio_context(BlockBackend *blk, AioContext *new_context)
1420 {
1421     BlockDriverState *bs = blk_bs(blk);
1422 
1423     if (bs) {
1424         if (blk->public.throttle_state) {
1425             throttle_timers_detach_aio_context(&blk->public.throttle_timers);
1426         }
1427         bdrv_set_aio_context(bs, new_context);
1428         if (blk->public.throttle_state) {
1429             throttle_timers_attach_aio_context(&blk->public.throttle_timers,
1430                                                new_context);
1431         }
1432     }
1433 }
1434 
1435 void blk_add_aio_context_notifier(BlockBackend *blk,
1436         void (*attached_aio_context)(AioContext *new_context, void *opaque),
1437         void (*detach_aio_context)(void *opaque), void *opaque)
1438 {
1439     BlockDriverState *bs = blk_bs(blk);
1440 
1441     if (bs) {
1442         bdrv_add_aio_context_notifier(bs, attached_aio_context,
1443                                       detach_aio_context, opaque);
1444     }
1445 }
1446 
1447 void blk_remove_aio_context_notifier(BlockBackend *blk,
1448                                      void (*attached_aio_context)(AioContext *,
1449                                                                   void *),
1450                                      void (*detach_aio_context)(void *),
1451                                      void *opaque)
1452 {
1453     BlockDriverState *bs = blk_bs(blk);
1454 
1455     if (bs) {
1456         bdrv_remove_aio_context_notifier(bs, attached_aio_context,
1457                                          detach_aio_context, opaque);
1458     }
1459 }
1460 
1461 void blk_add_remove_bs_notifier(BlockBackend *blk, Notifier *notify)
1462 {
1463     notifier_list_add(&blk->remove_bs_notifiers, notify);
1464 }
1465 
1466 void blk_add_insert_bs_notifier(BlockBackend *blk, Notifier *notify)
1467 {
1468     notifier_list_add(&blk->insert_bs_notifiers, notify);
1469 }
1470 
1471 void blk_io_plug(BlockBackend *blk)
1472 {
1473     BlockDriverState *bs = blk_bs(blk);
1474 
1475     if (bs) {
1476         bdrv_io_plug(bs);
1477     }
1478 }
1479 
1480 void blk_io_unplug(BlockBackend *blk)
1481 {
1482     BlockDriverState *bs = blk_bs(blk);
1483 
1484     if (bs) {
1485         bdrv_io_unplug(bs);
1486     }
1487 }
1488 
1489 BlockAcctStats *blk_get_stats(BlockBackend *blk)
1490 {
1491     return &blk->stats;
1492 }
1493 
1494 void *blk_aio_get(const AIOCBInfo *aiocb_info, BlockBackend *blk,
1495                   BlockCompletionFunc *cb, void *opaque)
1496 {
1497     return qemu_aio_get(aiocb_info, blk_bs(blk), cb, opaque);
1498 }
1499 
1500 int coroutine_fn blk_co_pwrite_zeroes(BlockBackend *blk, int64_t offset,
1501                                       int count, BdrvRequestFlags flags)
1502 {
1503     return blk_co_pwritev(blk, offset, count, NULL,
1504                           flags | BDRV_REQ_ZERO_WRITE);
1505 }
1506 
1507 int blk_pwrite_compressed(BlockBackend *blk, int64_t offset, const void *buf,
1508                           int count)
1509 {
1510     return blk_prw(blk, offset, (void *) buf, count, blk_write_entry,
1511                    BDRV_REQ_WRITE_COMPRESSED);
1512 }
1513 
1514 int blk_truncate(BlockBackend *blk, int64_t offset)
1515 {
1516     if (!blk_is_available(blk)) {
1517         return -ENOMEDIUM;
1518     }
1519 
1520     return bdrv_truncate(blk_bs(blk), offset);
1521 }
1522 
1523 int blk_pdiscard(BlockBackend *blk, int64_t offset, int count)
1524 {
1525     int ret = blk_check_byte_request(blk, offset, count);
1526     if (ret < 0) {
1527         return ret;
1528     }
1529 
1530     return bdrv_pdiscard(blk_bs(blk), offset, count);
1531 }
1532 
1533 int blk_save_vmstate(BlockBackend *blk, const uint8_t *buf,
1534                      int64_t pos, int size)
1535 {
1536     int ret;
1537 
1538     if (!blk_is_available(blk)) {
1539         return -ENOMEDIUM;
1540     }
1541 
1542     ret = bdrv_save_vmstate(blk_bs(blk), buf, pos, size);
1543     if (ret < 0) {
1544         return ret;
1545     }
1546 
1547     if (ret == size && !blk->enable_write_cache) {
1548         ret = bdrv_flush(blk_bs(blk));
1549     }
1550 
1551     return ret < 0 ? ret : size;
1552 }
1553 
1554 int blk_load_vmstate(BlockBackend *blk, uint8_t *buf, int64_t pos, int size)
1555 {
1556     if (!blk_is_available(blk)) {
1557         return -ENOMEDIUM;
1558     }
1559 
1560     return bdrv_load_vmstate(blk_bs(blk), buf, pos, size);
1561 }
1562 
1563 int blk_probe_blocksizes(BlockBackend *blk, BlockSizes *bsz)
1564 {
1565     if (!blk_is_available(blk)) {
1566         return -ENOMEDIUM;
1567     }
1568 
1569     return bdrv_probe_blocksizes(blk_bs(blk), bsz);
1570 }
1571 
1572 int blk_probe_geometry(BlockBackend *blk, HDGeometry *geo)
1573 {
1574     if (!blk_is_available(blk)) {
1575         return -ENOMEDIUM;
1576     }
1577 
1578     return bdrv_probe_geometry(blk_bs(blk), geo);
1579 }
1580 
1581 /*
1582  * Updates the BlockBackendRootState object with data from the currently
1583  * attached BlockDriverState.
1584  */
1585 void blk_update_root_state(BlockBackend *blk)
1586 {
1587     assert(blk->root);
1588 
1589     blk->root_state.open_flags    = blk->root->bs->open_flags;
1590     blk->root_state.read_only     = blk->root->bs->read_only;
1591     blk->root_state.detect_zeroes = blk->root->bs->detect_zeroes;
1592 }
1593 
1594 /*
1595  * Applies the information in the root state to the given BlockDriverState. This
1596  * does not include the flags which have to be specified for bdrv_open(), use
1597  * blk_get_open_flags_from_root_state() to inquire them.
1598  */
1599 void blk_apply_root_state(BlockBackend *blk, BlockDriverState *bs)
1600 {
1601     bs->detect_zeroes = blk->root_state.detect_zeroes;
1602 }
1603 
1604 /*
1605  * Returns the flags to be used for bdrv_open() of a BlockDriverState which is
1606  * supposed to inherit the root state.
1607  */
1608 int blk_get_open_flags_from_root_state(BlockBackend *blk)
1609 {
1610     int bs_flags;
1611 
1612     bs_flags = blk->root_state.read_only ? 0 : BDRV_O_RDWR;
1613     bs_flags |= blk->root_state.open_flags & ~BDRV_O_RDWR;
1614 
1615     return bs_flags;
1616 }
1617 
1618 BlockBackendRootState *blk_get_root_state(BlockBackend *blk)
1619 {
1620     return &blk->root_state;
1621 }
1622 
1623 int blk_commit_all(void)
1624 {
1625     BlockBackend *blk = NULL;
1626 
1627     while ((blk = blk_all_next(blk)) != NULL) {
1628         AioContext *aio_context = blk_get_aio_context(blk);
1629 
1630         aio_context_acquire(aio_context);
1631         if (blk_is_inserted(blk) && blk->root->bs->backing) {
1632             int ret = bdrv_commit(blk->root->bs);
1633             if (ret < 0) {
1634                 aio_context_release(aio_context);
1635                 return ret;
1636             }
1637         }
1638         aio_context_release(aio_context);
1639     }
1640     return 0;
1641 }
1642 
1643 int blk_flush_all(void)
1644 {
1645     BlockBackend *blk = NULL;
1646     int result = 0;
1647 
1648     while ((blk = blk_all_next(blk)) != NULL) {
1649         AioContext *aio_context = blk_get_aio_context(blk);
1650         int ret;
1651 
1652         aio_context_acquire(aio_context);
1653         if (blk_is_inserted(blk)) {
1654             ret = blk_flush(blk);
1655             if (ret < 0 && !result) {
1656                 result = ret;
1657             }
1658         }
1659         aio_context_release(aio_context);
1660     }
1661 
1662     return result;
1663 }
1664 
1665 
1666 /* throttling disk I/O limits */
1667 void blk_set_io_limits(BlockBackend *blk, ThrottleConfig *cfg)
1668 {
1669     throttle_group_config(blk, cfg);
1670 }
1671 
1672 void blk_io_limits_disable(BlockBackend *blk)
1673 {
1674     assert(blk->public.throttle_state);
1675     bdrv_drained_begin(blk_bs(blk));
1676     throttle_group_unregister_blk(blk);
1677     bdrv_drained_end(blk_bs(blk));
1678 }
1679 
1680 /* should be called before blk_set_io_limits if a limit is set */
1681 void blk_io_limits_enable(BlockBackend *blk, const char *group)
1682 {
1683     assert(!blk->public.throttle_state);
1684     throttle_group_register_blk(blk, group);
1685 }
1686 
1687 void blk_io_limits_update_group(BlockBackend *blk, const char *group)
1688 {
1689     /* this BB is not part of any group */
1690     if (!blk->public.throttle_state) {
1691         return;
1692     }
1693 
1694     /* this BB is a part of the same group than the one we want */
1695     if (!g_strcmp0(throttle_group_get_name(blk), group)) {
1696         return;
1697     }
1698 
1699     /* need to change the group this bs belong to */
1700     blk_io_limits_disable(blk);
1701     blk_io_limits_enable(blk, group);
1702 }
1703 
1704 static void blk_root_drained_begin(BdrvChild *child)
1705 {
1706     BlockBackend *blk = child->opaque;
1707 
1708     /* Note that blk->root may not be accessible here yet if we are just
1709      * attaching to a BlockDriverState that is drained. Use child instead. */
1710 
1711     if (blk->public.io_limits_disabled++ == 0) {
1712         throttle_group_restart_blk(blk);
1713     }
1714 }
1715 
1716 static void blk_root_drained_end(BdrvChild *child)
1717 {
1718     BlockBackend *blk = child->opaque;
1719 
1720     assert(blk->public.io_limits_disabled);
1721     --blk->public.io_limits_disabled;
1722 }
1723