1 /*
2  * QEMU System Emulator block driver
3  *
4  * Copyright (c) 2003 Fabrice Bellard
5  *
6  * Permission is hereby granted, free of charge, to any person obtaining a copy
7  * of this software and associated documentation files (the "Software"), to deal
8  * in the Software without restriction, including without limitation the rights
9  * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
10  * copies of the Software, and to permit persons to whom the Software is
11  * furnished to do so, subject to the following conditions:
12  *
13  * The above copyright notice and this permission notice shall be included in
14  * all copies or substantial portions of the Software.
15  *
16  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
17  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
18  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
19  * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
20  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
21  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
22  * THE SOFTWARE.
23  */
24 #ifndef BLOCK_INT_COMMON_H
25 #define BLOCK_INT_COMMON_H
26 
27 #include "block/aio.h"
28 #include "block/block-common.h"
29 #include "block/block-global-state.h"
30 #include "block/snapshot.h"
31 #include "qemu/iov.h"
32 #include "qemu/rcu.h"
33 #include "qemu/stats64.h"
34 
35 #define BLOCK_FLAG_LAZY_REFCOUNTS   8
36 
37 #define BLOCK_OPT_SIZE              "size"
38 #define BLOCK_OPT_ENCRYPT           "encryption"
39 #define BLOCK_OPT_ENCRYPT_FORMAT    "encrypt.format"
40 #define BLOCK_OPT_COMPAT6           "compat6"
41 #define BLOCK_OPT_HWVERSION         "hwversion"
42 #define BLOCK_OPT_BACKING_FILE      "backing_file"
43 #define BLOCK_OPT_BACKING_FMT       "backing_fmt"
44 #define BLOCK_OPT_CLUSTER_SIZE      "cluster_size"
45 #define BLOCK_OPT_TABLE_SIZE        "table_size"
46 #define BLOCK_OPT_PREALLOC          "preallocation"
47 #define BLOCK_OPT_SUBFMT            "subformat"
48 #define BLOCK_OPT_COMPAT_LEVEL      "compat"
49 #define BLOCK_OPT_LAZY_REFCOUNTS    "lazy_refcounts"
50 #define BLOCK_OPT_ADAPTER_TYPE      "adapter_type"
51 #define BLOCK_OPT_REDUNDANCY        "redundancy"
52 #define BLOCK_OPT_NOCOW             "nocow"
53 #define BLOCK_OPT_EXTENT_SIZE_HINT  "extent_size_hint"
54 #define BLOCK_OPT_OBJECT_SIZE       "object_size"
55 #define BLOCK_OPT_REFCOUNT_BITS     "refcount_bits"
56 #define BLOCK_OPT_DATA_FILE         "data_file"
57 #define BLOCK_OPT_DATA_FILE_RAW     "data_file_raw"
58 #define BLOCK_OPT_COMPRESSION_TYPE  "compression_type"
59 #define BLOCK_OPT_EXTL2             "extended_l2"
60 
61 #define BLOCK_PROBE_BUF_SIZE        512
62 
63 enum BdrvTrackedRequestType {
64     BDRV_TRACKED_READ,
65     BDRV_TRACKED_WRITE,
66     BDRV_TRACKED_DISCARD,
67     BDRV_TRACKED_TRUNCATE,
68 };
69 
70 /*
71  * That is not quite good that BdrvTrackedRequest structure is public,
72  * as block/io.c is very careful about incoming offset/bytes being
73  * correct. Be sure to assert bdrv_check_request() succeeded after any
74  * modification of BdrvTrackedRequest object out of block/io.c
75  */
76 typedef struct BdrvTrackedRequest {
77     BlockDriverState *bs;
78     int64_t offset;
79     int64_t bytes;
80     enum BdrvTrackedRequestType type;
81 
82     bool serialising;
83     int64_t overlap_offset;
84     int64_t overlap_bytes;
85 
86     QLIST_ENTRY(BdrvTrackedRequest) list;
87     Coroutine *co; /* owner, used for deadlock detection */
88     CoQueue wait_queue; /* coroutines blocked on this request */
89 
90     struct BdrvTrackedRequest *waiting_for;
91 } BdrvTrackedRequest;
92 
93 
94 struct BlockDriver {
95     /*
96      * These fields are initialized when this object is created,
97      * and are never changed afterwards.
98      */
99 
100     const char *format_name;
101     int instance_size;
102 
103     /*
104      * Set to true if the BlockDriver is a block filter. Block filters pass
105      * certain callbacks that refer to data (see block.c) to their bs->file
106      * or bs->backing (whichever one exists) if the driver doesn't implement
107      * them. Drivers that do not wish to forward must implement them and return
108      * -ENOTSUP.
109      * Note that filters are not allowed to modify data.
110      *
111      * Filters generally cannot have more than a single filtered child,
112      * because the data they present must at all times be the same as
113      * that on their filtered child.  That would be impossible to
114      * achieve for multiple filtered children.
115      * (And this filtered child must then be bs->file or bs->backing.)
116      */
117     bool is_filter;
118     /*
119      * Only make sense for filter drivers, for others must be false.
120      * If true, filtered child is bs->backing. Otherwise it's bs->file.
121      * Two internal filters use bs->backing as filtered child and has this
122      * field set to true: mirror_top and commit_top. There also two such test
123      * filters in tests/unit/test-bdrv-graph-mod.c.
124      *
125      * Never create any more such filters!
126      *
127      * TODO: imagine how to deprecate this behavior and make all filters work
128      * similarly using bs->file as filtered child.
129      */
130     bool filtered_child_is_backing;
131 
132     /*
133      * Set to true if the BlockDriver is a format driver.  Format nodes
134      * generally do not expect their children to be other format nodes
135      * (except for backing files), and so format probing is disabled
136      * on those children.
137      */
138     bool is_format;
139 
140     /*
141      * Drivers not implementing bdrv_parse_filename nor bdrv_open should have
142      * this field set to true, except ones that are defined only by their
143      * child's bs.
144      * An example of the last type will be the quorum block driver.
145      */
146     bool bdrv_needs_filename;
147 
148     /*
149      * Set if a driver can support backing files. This also implies the
150      * following semantics:
151      *
152      *  - Return status 0 of .bdrv_co_block_status means that corresponding
153      *    blocks are not allocated in this layer of backing-chain
154      *  - For such (unallocated) blocks, read will:
155      *    - fill buffer with zeros if there is no backing file
156      *    - read from the backing file otherwise, where the block layer
157      *      takes care of reading zeros beyond EOF if backing file is short
158      */
159     bool supports_backing;
160 
161     bool has_variable_length;
162 
163     /*
164      * Drivers setting this field must be able to work with just a plain
165      * filename with '<protocol_name>:' as a prefix, and no other options.
166      * Options may be extracted from the filename by implementing
167      * bdrv_parse_filename.
168      */
169     const char *protocol_name;
170 
171     /* List of options for creating images, terminated by name == NULL */
172     QemuOptsList *create_opts;
173 
174     /* List of options for image amend */
175     QemuOptsList *amend_opts;
176 
177     /*
178      * If this driver supports reopening images this contains a
179      * NULL-terminated list of the runtime options that can be
180      * modified. If an option in this list is unspecified during
181      * reopen then it _must_ be reset to its default value or return
182      * an error.
183      */
184     const char *const *mutable_opts;
185 
186     /*
187      * Pointer to a NULL-terminated array of names of strong options
188      * that can be specified for bdrv_open(). A strong option is one
189      * that changes the data of a BDS.
190      * If this pointer is NULL, the array is considered empty.
191      * "filename" and "driver" are always considered strong.
192      */
193     const char *const *strong_runtime_opts;
194 
195 
196     /*
197      * Global state (GS) API. These functions run under the BQL.
198      *
199      * See include/block/block-global-state.h for more information about
200      * the GS API.
201      */
202 
203     /*
204      * This function is invoked under BQL before .bdrv_co_amend()
205      * (which in contrast does not necessarily run under the BQL)
206      * to allow driver-specific initialization code that requires
207      * the BQL, like setting up specific permission flags.
208      */
209     int (*bdrv_amend_pre_run)(BlockDriverState *bs, Error **errp);
210     /*
211      * This function is invoked under BQL after .bdrv_co_amend()
212      * to allow cleaning up what was done in .bdrv_amend_pre_run().
213      */
214     void (*bdrv_amend_clean)(BlockDriverState *bs);
215 
216     /*
217      * Return true if @to_replace can be replaced by a BDS with the
218      * same data as @bs without it affecting @bs's behavior (that is,
219      * without it being visible to @bs's parents).
220      */
221     bool (*bdrv_recurse_can_replace)(BlockDriverState *bs,
222                                      BlockDriverState *to_replace);
223 
224     int (*bdrv_probe_device)(const char *filename);
225 
226     /*
227      * Any driver implementing this callback is expected to be able to handle
228      * NULL file names in its .bdrv_open() implementation.
229      */
230     void (*bdrv_parse_filename)(const char *filename, QDict *options,
231                                 Error **errp);
232 
233     /* For handling image reopen for split or non-split files. */
234     int (*bdrv_reopen_prepare)(BDRVReopenState *reopen_state,
235                                BlockReopenQueue *queue, Error **errp);
236     void (*bdrv_reopen_commit)(BDRVReopenState *reopen_state);
237     void (*bdrv_reopen_commit_post)(BDRVReopenState *reopen_state);
238     void (*bdrv_reopen_abort)(BDRVReopenState *reopen_state);
239     void (*bdrv_join_options)(QDict *options, QDict *old_options);
240 
241     int (*bdrv_open)(BlockDriverState *bs, QDict *options, int flags,
242                      Error **errp);
243 
244     /* Protocol drivers should implement this instead of bdrv_open */
245     int (*bdrv_file_open)(BlockDriverState *bs, QDict *options, int flags,
246                           Error **errp);
247     void (*bdrv_close)(BlockDriverState *bs);
248 
249     int coroutine_fn (*bdrv_co_create)(BlockdevCreateOptions *opts,
250                                        Error **errp);
251     int coroutine_fn (*bdrv_co_create_opts)(BlockDriver *drv,
252                                             const char *filename,
253                                             QemuOpts *opts,
254                                             Error **errp);
255 
256     int (*bdrv_amend_options)(BlockDriverState *bs,
257                               QemuOpts *opts,
258                               BlockDriverAmendStatusCB *status_cb,
259                               void *cb_opaque,
260                               bool force,
261                               Error **errp);
262 
263     int (*bdrv_make_empty)(BlockDriverState *bs);
264 
265     /*
266      * Refreshes the bs->exact_filename field. If that is impossible,
267      * bs->exact_filename has to be left empty.
268      */
269     void (*bdrv_refresh_filename)(BlockDriverState *bs);
270 
271     /*
272      * Gathers the open options for all children into @target.
273      * A simple format driver (without backing file support) might
274      * implement this function like this:
275      *
276      *     QINCREF(bs->file->bs->full_open_options);
277      *     qdict_put(target, "file", bs->file->bs->full_open_options);
278      *
279      * If not specified, the generic implementation will simply put
280      * all children's options under their respective name.
281      *
282      * @backing_overridden is true when bs->backing seems not to be
283      * the child that would result from opening bs->backing_file.
284      * Therefore, if it is true, the backing child's options should be
285      * gathered; otherwise, there is no need since the backing child
286      * is the one implied by the image header.
287      *
288      * Note that ideally this function would not be needed.  Every
289      * block driver which implements it is probably doing something
290      * shady regarding its runtime option structure.
291      */
292     void (*bdrv_gather_child_options)(BlockDriverState *bs, QDict *target,
293                                       bool backing_overridden);
294 
295     /*
296      * Returns an allocated string which is the directory name of this BDS: It
297      * will be used to make relative filenames absolute by prepending this
298      * function's return value to them.
299      */
300     char *(*bdrv_dirname)(BlockDriverState *bs, Error **errp);
301 
302     /*
303      * This informs the driver that we are no longer interested in the result
304      * of in-flight requests, so don't waste the time if possible.
305      *
306      * One example usage is to avoid waiting for an nbd target node reconnect
307      * timeout during job-cancel with force=true.
308      */
309     void (*bdrv_cancel_in_flight)(BlockDriverState *bs);
310 
311     int (*bdrv_inactivate)(BlockDriverState *bs);
312 
313     int (*bdrv_snapshot_create)(BlockDriverState *bs,
314                                 QEMUSnapshotInfo *sn_info);
315     int (*bdrv_snapshot_goto)(BlockDriverState *bs,
316                               const char *snapshot_id);
317     int (*bdrv_snapshot_delete)(BlockDriverState *bs,
318                                 const char *snapshot_id,
319                                 const char *name,
320                                 Error **errp);
321     int (*bdrv_snapshot_list)(BlockDriverState *bs,
322                               QEMUSnapshotInfo **psn_info);
323     int (*bdrv_snapshot_load_tmp)(BlockDriverState *bs,
324                                   const char *snapshot_id,
325                                   const char *name,
326                                   Error **errp);
327 
328     int (*bdrv_change_backing_file)(BlockDriverState *bs,
329         const char *backing_file, const char *backing_fmt);
330 
331     /* TODO Better pass a option string/QDict/QemuOpts to add any rule? */
332     int (*bdrv_debug_breakpoint)(BlockDriverState *bs, const char *event,
333         const char *tag);
334     int (*bdrv_debug_remove_breakpoint)(BlockDriverState *bs,
335         const char *tag);
336     int (*bdrv_debug_resume)(BlockDriverState *bs, const char *tag);
337     bool (*bdrv_debug_is_suspended)(BlockDriverState *bs, const char *tag);
338 
339     void (*bdrv_refresh_limits)(BlockDriverState *bs, Error **errp);
340 
341     /*
342      * Returns 1 if newly created images are guaranteed to contain only
343      * zeros, 0 otherwise.
344      */
345     int (*bdrv_has_zero_init)(BlockDriverState *bs);
346 
347     /*
348      * Remove fd handlers, timers, and other event loop callbacks so the event
349      * loop is no longer in use.  Called with no in-flight requests and in
350      * depth-first traversal order with parents before child nodes.
351      */
352     void (*bdrv_detach_aio_context)(BlockDriverState *bs);
353 
354     /*
355      * Add fd handlers, timers, and other event loop callbacks so I/O requests
356      * can be processed again.  Called with no in-flight requests and in
357      * depth-first traversal order with child nodes before parent nodes.
358      */
359     void (*bdrv_attach_aio_context)(BlockDriverState *bs,
360                                     AioContext *new_context);
361 
362     /**
363      * Try to get @bs's logical and physical block size.
364      * On success, store them in @bsz and return zero.
365      * On failure, return negative errno.
366      */
367     int (*bdrv_probe_blocksizes)(BlockDriverState *bs, BlockSizes *bsz);
368     /**
369      * Try to get @bs's geometry (cyls, heads, sectors)
370      * On success, store them in @geo and return 0.
371      * On failure return -errno.
372      * Only drivers that want to override guest geometry implement this
373      * callback; see hd_geometry_guess().
374      */
375     int (*bdrv_probe_geometry)(BlockDriverState *bs, HDGeometry *geo);
376 
377     void (*bdrv_add_child)(BlockDriverState *parent, BlockDriverState *child,
378                            Error **errp);
379     void (*bdrv_del_child)(BlockDriverState *parent, BdrvChild *child,
380                            Error **errp);
381 
382     /**
383      * Informs the block driver that a permission change is intended. The
384      * driver checks whether the change is permissible and may take other
385      * preparations for the change (e.g. get file system locks). This operation
386      * is always followed either by a call to either .bdrv_set_perm or
387      * .bdrv_abort_perm_update.
388      *
389      * Checks whether the requested set of cumulative permissions in @perm
390      * can be granted for accessing @bs and whether no other users are using
391      * permissions other than those given in @shared (both arguments take
392      * BLK_PERM_* bitmasks).
393      *
394      * If both conditions are met, 0 is returned. Otherwise, -errno is returned
395      * and errp is set to an error describing the conflict.
396      */
397     int (*bdrv_check_perm)(BlockDriverState *bs, uint64_t perm,
398                            uint64_t shared, Error **errp);
399 
400     /**
401      * Called to inform the driver that the set of cumulative set of used
402      * permissions for @bs has changed to @perm, and the set of sharable
403      * permission to @shared. The driver can use this to propagate changes to
404      * its children (i.e. request permissions only if a parent actually needs
405      * them).
406      *
407      * This function is only invoked after bdrv_check_perm(), so block drivers
408      * may rely on preparations made in their .bdrv_check_perm implementation.
409      */
410     void (*bdrv_set_perm)(BlockDriverState *bs, uint64_t perm, uint64_t shared);
411 
412     /*
413      * Called to inform the driver that after a previous bdrv_check_perm()
414      * call, the permission update is not performed and any preparations made
415      * for it (e.g. taken file locks) need to be undone.
416      *
417      * This function can be called even for nodes that never saw a
418      * bdrv_check_perm() call. It is a no-op then.
419      */
420     void (*bdrv_abort_perm_update)(BlockDriverState *bs);
421 
422     /**
423      * Returns in @nperm and @nshared the permissions that the driver for @bs
424      * needs on its child @c, based on the cumulative permissions requested by
425      * the parents in @parent_perm and @parent_shared.
426      *
427      * If @c is NULL, return the permissions for attaching a new child for the
428      * given @child_class and @role.
429      *
430      * If @reopen_queue is non-NULL, don't return the currently needed
431      * permissions, but those that will be needed after applying the
432      * @reopen_queue.
433      */
434      void (*bdrv_child_perm)(BlockDriverState *bs, BdrvChild *c,
435                              BdrvChildRole role,
436                              BlockReopenQueue *reopen_queue,
437                              uint64_t parent_perm, uint64_t parent_shared,
438                              uint64_t *nperm, uint64_t *nshared);
439 
440     /**
441      * Register/unregister a buffer for I/O. For example, when the driver is
442      * interested to know the memory areas that will later be used in iovs, so
443      * that it can do IOMMU mapping with VFIO etc., in order to get better
444      * performance. In the case of VFIO drivers, this callback is used to do
445      * DMA mapping for hot buffers.
446      *
447      * Returns: true on success, false on failure
448      */
449     bool (*bdrv_register_buf)(BlockDriverState *bs, void *host, size_t size,
450                               Error **errp);
451     void (*bdrv_unregister_buf)(BlockDriverState *bs, void *host, size_t size);
452 
453     /*
454      * This field is modified only under the BQL, and is part of
455      * the global state.
456      */
457     QLIST_ENTRY(BlockDriver) list;
458 
459     /*
460      * I/O API functions. These functions are thread-safe.
461      *
462      * See include/block/block-io.h for more information about
463      * the I/O API.
464      */
465 
466     int (*bdrv_probe)(const uint8_t *buf, int buf_size, const char *filename);
467 
468     int coroutine_fn (*bdrv_co_amend)(BlockDriverState *bs,
469                                       BlockdevAmendOptions *opts,
470                                       bool force,
471                                       Error **errp);
472 
473     /* aio */
474     BlockAIOCB *(*bdrv_aio_preadv)(BlockDriverState *bs,
475         int64_t offset, int64_t bytes, QEMUIOVector *qiov,
476         BdrvRequestFlags flags, BlockCompletionFunc *cb, void *opaque);
477     BlockAIOCB *(*bdrv_aio_pwritev)(BlockDriverState *bs,
478         int64_t offset, int64_t bytes, QEMUIOVector *qiov,
479         BdrvRequestFlags flags, BlockCompletionFunc *cb, void *opaque);
480     BlockAIOCB *(*bdrv_aio_flush)(BlockDriverState *bs,
481         BlockCompletionFunc *cb, void *opaque);
482     BlockAIOCB *(*bdrv_aio_pdiscard)(BlockDriverState *bs,
483         int64_t offset, int bytes,
484         BlockCompletionFunc *cb, void *opaque);
485 
486     int coroutine_fn (*bdrv_co_readv)(BlockDriverState *bs,
487         int64_t sector_num, int nb_sectors, QEMUIOVector *qiov);
488 
489     /**
490      * @offset: position in bytes to read at
491      * @bytes: number of bytes to read
492      * @qiov: the buffers to fill with read data
493      * @flags: currently unused, always 0
494      *
495      * @offset and @bytes will be a multiple of 'request_alignment',
496      * but the length of individual @qiov elements does not have to
497      * be a multiple.
498      *
499      * @bytes will always equal the total size of @qiov, and will be
500      * no larger than 'max_transfer'.
501      *
502      * The buffer in @qiov may point directly to guest memory.
503      */
504     int coroutine_fn (*bdrv_co_preadv)(BlockDriverState *bs,
505         int64_t offset, int64_t bytes, QEMUIOVector *qiov,
506         BdrvRequestFlags flags);
507 
508     int coroutine_fn (*bdrv_co_preadv_part)(BlockDriverState *bs,
509         int64_t offset, int64_t bytes,
510         QEMUIOVector *qiov, size_t qiov_offset,
511         BdrvRequestFlags flags);
512 
513     int coroutine_fn (*bdrv_co_writev)(BlockDriverState *bs,
514         int64_t sector_num, int nb_sectors, QEMUIOVector *qiov,
515         int flags);
516     /**
517      * @offset: position in bytes to write at
518      * @bytes: number of bytes to write
519      * @qiov: the buffers containing data to write
520      * @flags: zero or more bits allowed by 'supported_write_flags'
521      *
522      * @offset and @bytes will be a multiple of 'request_alignment',
523      * but the length of individual @qiov elements does not have to
524      * be a multiple.
525      *
526      * @bytes will always equal the total size of @qiov, and will be
527      * no larger than 'max_transfer'.
528      *
529      * The buffer in @qiov may point directly to guest memory.
530      */
531     int coroutine_fn (*bdrv_co_pwritev)(BlockDriverState *bs,
532         int64_t offset, int64_t bytes, QEMUIOVector *qiov,
533         BdrvRequestFlags flags);
534     int coroutine_fn (*bdrv_co_pwritev_part)(BlockDriverState *bs,
535         int64_t offset, int64_t bytes, QEMUIOVector *qiov, size_t qiov_offset,
536         BdrvRequestFlags flags);
537 
538     /*
539      * Efficiently zero a region of the disk image.  Typically an image format
540      * would use a compact metadata representation to implement this.  This
541      * function pointer may be NULL or return -ENOSUP and .bdrv_co_writev()
542      * will be called instead.
543      */
544     int coroutine_fn (*bdrv_co_pwrite_zeroes)(BlockDriverState *bs,
545         int64_t offset, int64_t bytes, BdrvRequestFlags flags);
546     int coroutine_fn (*bdrv_co_pdiscard)(BlockDriverState *bs,
547         int64_t offset, int64_t bytes);
548 
549     /*
550      * Map [offset, offset + nbytes) range onto a child of @bs to copy from,
551      * and invoke bdrv_co_copy_range_from(child, ...), or invoke
552      * bdrv_co_copy_range_to() if @bs is the leaf child to copy data from.
553      *
554      * See the comment of bdrv_co_copy_range for the parameter and return value
555      * semantics.
556      */
557     int coroutine_fn (*bdrv_co_copy_range_from)(BlockDriverState *bs,
558                                                 BdrvChild *src,
559                                                 int64_t offset,
560                                                 BdrvChild *dst,
561                                                 int64_t dst_offset,
562                                                 int64_t bytes,
563                                                 BdrvRequestFlags read_flags,
564                                                 BdrvRequestFlags write_flags);
565 
566     /*
567      * Map [offset, offset + nbytes) range onto a child of bs to copy data to,
568      * and invoke bdrv_co_copy_range_to(child, src, ...), or perform the copy
569      * operation if @bs is the leaf and @src has the same BlockDriver.  Return
570      * -ENOTSUP if @bs is the leaf but @src has a different BlockDriver.
571      *
572      * See the comment of bdrv_co_copy_range for the parameter and return value
573      * semantics.
574      */
575     int coroutine_fn (*bdrv_co_copy_range_to)(BlockDriverState *bs,
576                                               BdrvChild *src,
577                                               int64_t src_offset,
578                                               BdrvChild *dst,
579                                               int64_t dst_offset,
580                                               int64_t bytes,
581                                               BdrvRequestFlags read_flags,
582                                               BdrvRequestFlags write_flags);
583 
584     /*
585      * Building block for bdrv_block_status[_above] and
586      * bdrv_is_allocated[_above].  The driver should answer only
587      * according to the current layer, and should only need to set
588      * BDRV_BLOCK_DATA, BDRV_BLOCK_ZERO, BDRV_BLOCK_OFFSET_VALID,
589      * and/or BDRV_BLOCK_RAW; if the current layer defers to a backing
590      * layer, the result should be 0 (and not BDRV_BLOCK_ZERO).  See
591      * block.h for the overall meaning of the bits.  As a hint, the
592      * flag want_zero is true if the caller cares more about precise
593      * mappings (favor accurate _OFFSET_VALID/_ZERO) or false for
594      * overall allocation (favor larger *pnum, perhaps by reporting
595      * _DATA instead of _ZERO).  The block layer guarantees input
596      * clamped to bdrv_getlength() and aligned to request_alignment,
597      * as well as non-NULL pnum, map, and file; in turn, the driver
598      * must return an error or set pnum to an aligned non-zero value.
599      *
600      * Note that @bytes is just a hint on how big of a region the
601      * caller wants to inspect.  It is not a limit on *pnum.
602      * Implementations are free to return larger values of *pnum if
603      * doing so does not incur a performance penalty.
604      *
605      * block/io.c's bdrv_co_block_status() will utilize an unclamped
606      * *pnum value for the block-status cache on protocol nodes, prior
607      * to clamping *pnum for return to its caller.
608      */
609     int coroutine_fn (*bdrv_co_block_status)(BlockDriverState *bs,
610         bool want_zero, int64_t offset, int64_t bytes, int64_t *pnum,
611         int64_t *map, BlockDriverState **file);
612 
613     /*
614      * Snapshot-access API.
615      *
616      * Block-driver may provide snapshot-access API: special functions to access
617      * some internal "snapshot". The functions are similar with normal
618      * read/block_status/discard handler, but don't have any specific handling
619      * in generic block-layer: no serializing, no alignment, no tracked
620      * requests. So, block-driver that realizes these APIs is fully responsible
621      * for synchronization between snapshot-access API and normal IO requests.
622      *
623      * TODO: To be able to support qcow2's internal snapshots, this API will
624      * need to be extended to:
625      * - be able to select a specific snapshot
626      * - receive the snapshot's actual length (which may differ from bs's
627      *   length)
628      */
629     int coroutine_fn (*bdrv_co_preadv_snapshot)(BlockDriverState *bs,
630         int64_t offset, int64_t bytes, QEMUIOVector *qiov, size_t qiov_offset);
631     int coroutine_fn (*bdrv_co_snapshot_block_status)(BlockDriverState *bs,
632         bool want_zero, int64_t offset, int64_t bytes, int64_t *pnum,
633         int64_t *map, BlockDriverState **file);
634     int coroutine_fn (*bdrv_co_pdiscard_snapshot)(BlockDriverState *bs,
635         int64_t offset, int64_t bytes);
636 
637     /*
638      * Invalidate any cached meta-data.
639      */
640     void coroutine_fn GRAPH_RDLOCK_PTR (*bdrv_co_invalidate_cache)(
641         BlockDriverState *bs, Error **errp);
642 
643     /*
644      * Flushes all data for all layers by calling bdrv_co_flush for underlying
645      * layers, if needed. This function is needed for deterministic
646      * synchronization of the flush finishing callback.
647      */
648     int coroutine_fn (*bdrv_co_flush)(BlockDriverState *bs);
649 
650     /* Delete a created file. */
651     int coroutine_fn (*bdrv_co_delete_file)(BlockDriverState *bs,
652                                             Error **errp);
653 
654     /*
655      * Flushes all data that was already written to the OS all the way down to
656      * the disk (for example file-posix.c calls fsync()).
657      */
658     int coroutine_fn (*bdrv_co_flush_to_disk)(BlockDriverState *bs);
659 
660     /*
661      * Flushes all internal caches to the OS. The data may still sit in a
662      * writeback cache of the host OS, but it will survive a crash of the qemu
663      * process.
664      */
665     int coroutine_fn (*bdrv_co_flush_to_os)(BlockDriverState *bs);
666 
667     /*
668      * Truncate @bs to @offset bytes using the given @prealloc mode
669      * when growing.  Modes other than PREALLOC_MODE_OFF should be
670      * rejected when shrinking @bs.
671      *
672      * If @exact is true, @bs must be resized to exactly @offset.
673      * Otherwise, it is sufficient for @bs (if it is a host block
674      * device and thus there is no way to resize it) to be at least
675      * @offset bytes in length.
676      *
677      * If @exact is true and this function fails but would succeed
678      * with @exact = false, it should return -ENOTSUP.
679      */
680     int coroutine_fn (*bdrv_co_truncate)(BlockDriverState *bs, int64_t offset,
681                                          bool exact, PreallocMode prealloc,
682                                          BdrvRequestFlags flags, Error **errp);
683     int64_t coroutine_fn (*bdrv_co_getlength)(BlockDriverState *bs);
684     int64_t coroutine_fn (*bdrv_co_get_allocated_file_size)(
685         BlockDriverState *bs);
686 
687     BlockMeasureInfo *(*bdrv_measure)(QemuOpts *opts, BlockDriverState *in_bs,
688                                       Error **errp);
689 
690     int coroutine_fn (*bdrv_co_pwritev_compressed)(BlockDriverState *bs,
691         int64_t offset, int64_t bytes, QEMUIOVector *qiov);
692     int coroutine_fn (*bdrv_co_pwritev_compressed_part)(BlockDriverState *bs,
693         int64_t offset, int64_t bytes, QEMUIOVector *qiov,
694         size_t qiov_offset);
695 
696     int coroutine_fn (*bdrv_co_get_info)(BlockDriverState *bs,
697                                          BlockDriverInfo *bdi);
698 
699     ImageInfoSpecific *(*bdrv_get_specific_info)(BlockDriverState *bs,
700                                                  Error **errp);
701     BlockStatsSpecific *(*bdrv_get_specific_stats)(BlockDriverState *bs);
702 
703     int coroutine_fn GRAPH_RDLOCK_PTR (*bdrv_co_save_vmstate)(
704         BlockDriverState *bs, QEMUIOVector *qiov, int64_t pos);
705 
706     int coroutine_fn GRAPH_RDLOCK_PTR (*bdrv_co_load_vmstate)(
707         BlockDriverState *bs, QEMUIOVector *qiov, int64_t pos);
708 
709     /* removable device specific */
710     bool coroutine_fn (*bdrv_co_is_inserted)(BlockDriverState *bs);
711     void coroutine_fn (*bdrv_co_eject)(BlockDriverState *bs, bool eject_flag);
712     void coroutine_fn (*bdrv_co_lock_medium)(BlockDriverState *bs, bool locked);
713 
714     /* to control generic scsi devices */
715     BlockAIOCB *(*bdrv_aio_ioctl)(BlockDriverState *bs,
716         unsigned long int req, void *buf,
717         BlockCompletionFunc *cb, void *opaque);
718     int coroutine_fn (*bdrv_co_ioctl)(BlockDriverState *bs,
719                                       unsigned long int req, void *buf);
720 
721     /*
722      * Returns 0 for completed check, -errno for internal errors.
723      * The check results are stored in result.
724      */
725     int coroutine_fn GRAPH_RDLOCK_PTR (*bdrv_co_check)(
726         BlockDriverState *bs, BdrvCheckResult *result, BdrvCheckMode fix);
727 
728     void coroutine_fn (*bdrv_co_debug_event)(BlockDriverState *bs,
729                                              BlkdebugEvent event);
730 
731     /* io queue for linux-aio */
732     void coroutine_fn (*bdrv_co_io_plug)(BlockDriverState *bs);
733     void coroutine_fn (*bdrv_co_io_unplug)(BlockDriverState *bs);
734 
735     /**
736      * bdrv_drain_begin is called if implemented in the beginning of a
737      * drain operation to drain and stop any internal sources of requests in
738      * the driver.
739      * bdrv_drain_end is called if implemented at the end of the drain.
740      *
741      * They should be used by the driver to e.g. manage scheduled I/O
742      * requests, or toggle an internal state. After the end of the drain new
743      * requests will continue normally.
744      *
745      * Implementations of both functions must not call aio_poll().
746      */
747     void (*bdrv_drain_begin)(BlockDriverState *bs);
748     void (*bdrv_drain_end)(BlockDriverState *bs);
749 
750     bool (*bdrv_supports_persistent_dirty_bitmap)(BlockDriverState *bs);
751     bool coroutine_fn (*bdrv_co_can_store_new_dirty_bitmap)(
752         BlockDriverState *bs, const char *name, uint32_t granularity,
753         Error **errp);
754     int coroutine_fn (*bdrv_co_remove_persistent_dirty_bitmap)(
755         BlockDriverState *bs, const char *name, Error **errp);
756 };
757 
758 static inline bool block_driver_can_compress(BlockDriver *drv)
759 {
760     return drv->bdrv_co_pwritev_compressed ||
761            drv->bdrv_co_pwritev_compressed_part;
762 }
763 
764 typedef struct BlockLimits {
765     /*
766      * Alignment requirement, in bytes, for offset/length of I/O
767      * requests. Must be a power of 2 less than INT_MAX; defaults to
768      * 1 for drivers with modern byte interfaces, and to 512
769      * otherwise.
770      */
771     uint32_t request_alignment;
772 
773     /*
774      * Maximum number of bytes that can be discarded at once. Must be multiple
775      * of pdiscard_alignment, but need not be power of 2. May be 0 if no
776      * inherent 64-bit limit.
777      */
778     int64_t max_pdiscard;
779 
780     /*
781      * Optimal alignment for discard requests in bytes. A power of 2
782      * is best but not mandatory.  Must be a multiple of
783      * bl.request_alignment, and must be less than max_pdiscard if
784      * that is set. May be 0 if bl.request_alignment is good enough
785      */
786     uint32_t pdiscard_alignment;
787 
788     /*
789      * Maximum number of bytes that can zeroized at once. Must be multiple of
790      * pwrite_zeroes_alignment. 0 means no limit.
791      */
792     int64_t max_pwrite_zeroes;
793 
794     /*
795      * Optimal alignment for write zeroes requests in bytes. A power
796      * of 2 is best but not mandatory.  Must be a multiple of
797      * bl.request_alignment, and must be less than max_pwrite_zeroes
798      * if that is set. May be 0 if bl.request_alignment is good
799      * enough
800      */
801     uint32_t pwrite_zeroes_alignment;
802 
803     /*
804      * Optimal transfer length in bytes.  A power of 2 is best but not
805      * mandatory.  Must be a multiple of bl.request_alignment, or 0 if
806      * no preferred size
807      */
808     uint32_t opt_transfer;
809 
810     /*
811      * Maximal transfer length in bytes.  Need not be power of 2, but
812      * must be multiple of opt_transfer and bl.request_alignment, or 0
813      * for no 32-bit limit.  For now, anything larger than INT_MAX is
814      * clamped down.
815      */
816     uint32_t max_transfer;
817 
818     /*
819      * Maximal hardware transfer length in bytes.  Applies whenever
820      * transfers to the device bypass the kernel I/O scheduler, for
821      * example with SG_IO.  If larger than max_transfer or if zero,
822      * blk_get_max_hw_transfer will fall back to max_transfer.
823      */
824     uint64_t max_hw_transfer;
825 
826     /*
827      * Maximal number of scatter/gather elements allowed by the hardware.
828      * Applies whenever transfers to the device bypass the kernel I/O
829      * scheduler, for example with SG_IO.  If larger than max_iov
830      * or if zero, blk_get_max_hw_iov will fall back to max_iov.
831      */
832     int max_hw_iov;
833 
834 
835     /* memory alignment, in bytes so that no bounce buffer is needed */
836     size_t min_mem_alignment;
837 
838     /* memory alignment, in bytes, for bounce buffer */
839     size_t opt_mem_alignment;
840 
841     /* maximum number of iovec elements */
842     int max_iov;
843 } BlockLimits;
844 
845 typedef struct BdrvOpBlocker BdrvOpBlocker;
846 
847 typedef struct BdrvAioNotifier {
848     void (*attached_aio_context)(AioContext *new_context, void *opaque);
849     void (*detach_aio_context)(void *opaque);
850 
851     void *opaque;
852     bool deleted;
853 
854     QLIST_ENTRY(BdrvAioNotifier) list;
855 } BdrvAioNotifier;
856 
857 struct BdrvChildClass {
858     /*
859      * If true, bdrv_replace_node() doesn't change the node this BdrvChild
860      * points to.
861      */
862     bool stay_at_node;
863 
864     /*
865      * If true, the parent is a BlockDriverState and bdrv_next_all_states()
866      * will return it. This information is used for drain_all, where every node
867      * will be drained separately, so the drain only needs to be propagated to
868      * non-BDS parents.
869      */
870     bool parent_is_bds;
871 
872     /*
873      * Global state (GS) API. These functions run under the BQL.
874      *
875      * See include/block/block-global-state.h for more information about
876      * the GS API.
877      */
878     void (*inherit_options)(BdrvChildRole role, bool parent_is_format,
879                             int *child_flags, QDict *child_options,
880                             int parent_flags, QDict *parent_options);
881     void (*change_media)(BdrvChild *child, bool load);
882 
883     /*
884      * Returns a malloced string that describes the parent of the child for a
885      * human reader. This could be a node-name, BlockBackend name, qdev ID or
886      * QOM path of the device owning the BlockBackend, job type and ID etc. The
887      * caller is responsible for freeing the memory.
888      */
889     char *(*get_parent_desc)(BdrvChild *child);
890 
891     /*
892      * Notifies the parent that the child has been activated/inactivated (e.g.
893      * when migration is completing) and it can start/stop requesting
894      * permissions and doing I/O on it.
895      */
896     void (*activate)(BdrvChild *child, Error **errp);
897     int (*inactivate)(BdrvChild *child);
898 
899     void GRAPH_WRLOCK_PTR (*attach)(BdrvChild *child);
900     void GRAPH_WRLOCK_PTR (*detach)(BdrvChild *child);
901 
902     /*
903      * Notifies the parent that the filename of its child has changed (e.g.
904      * because the direct child was removed from the backing chain), so that it
905      * can update its reference.
906      */
907     int (*update_filename)(BdrvChild *child, BlockDriverState *new_base,
908                            const char *filename, Error **errp);
909 
910     bool (*change_aio_ctx)(BdrvChild *child, AioContext *ctx,
911                            GHashTable *visited, Transaction *tran,
912                            Error **errp);
913 
914     /*
915      * I/O API functions. These functions are thread-safe.
916      *
917      * See include/block/block-io.h for more information about
918      * the I/O API.
919      */
920 
921     void (*resize)(BdrvChild *child);
922 
923     /*
924      * Returns a name that is supposedly more useful for human users than the
925      * node name for identifying the node in question (in particular, a BB
926      * name), or NULL if the parent can't provide a better name.
927      */
928     const char *(*get_name)(BdrvChild *child);
929 
930     AioContext *(*get_parent_aio_context)(BdrvChild *child);
931 
932     /*
933      * If this pair of functions is implemented, the parent doesn't issue new
934      * requests after returning from .drained_begin() until .drained_end() is
935      * called.
936      *
937      * These functions must not change the graph (and therefore also must not
938      * call aio_poll(), which could change the graph indirectly).
939      *
940      * Note that this can be nested. If drained_begin() was called twice, new
941      * I/O is allowed only after drained_end() was called twice, too.
942      */
943     void (*drained_begin)(BdrvChild *child);
944     void (*drained_end)(BdrvChild *child);
945 
946     /*
947      * Returns whether the parent has pending requests for the child. This
948      * callback is polled after .drained_begin() has been called until all
949      * activity on the child has stopped.
950      */
951     bool (*drained_poll)(BdrvChild *child);
952 };
953 
954 extern const BdrvChildClass child_of_bds;
955 
956 struct BdrvChild {
957     BlockDriverState *bs;
958     char *name;
959     const BdrvChildClass *klass;
960     BdrvChildRole role;
961     void *opaque;
962 
963     /**
964      * Granted permissions for operating on this BdrvChild (BLK_PERM_* bitmask)
965      */
966     uint64_t perm;
967 
968     /**
969      * Permissions that can still be granted to other users of @bs while this
970      * BdrvChild is still attached to it. (BLK_PERM_* bitmask)
971      */
972     uint64_t shared_perm;
973 
974     /*
975      * This link is frozen: the child can neither be replaced nor
976      * detached from the parent.
977      */
978     bool frozen;
979 
980     /*
981      * True if the parent of this child has been drained by this BdrvChild
982      * (through klass->drained_*).
983      *
984      * It is generally true if bs->quiesce_counter > 0. It may differ while the
985      * child is entering or leaving a drained section.
986      */
987     bool quiesced_parent;
988 
989     QLIST_ENTRY(BdrvChild) next;
990     QLIST_ENTRY(BdrvChild) next_parent;
991 };
992 
993 /*
994  * Allows bdrv_co_block_status() to cache one data region for a
995  * protocol node.
996  *
997  * @valid: Whether the cache is valid (should be accessed with atomic
998  *         functions so this can be reset by RCU readers)
999  * @data_start: Offset where we know (or strongly assume) is data
1000  * @data_end: Offset where the data region ends (which is not necessarily
1001  *            the start of a zeroed region)
1002  */
1003 typedef struct BdrvBlockStatusCache {
1004     struct rcu_head rcu;
1005 
1006     bool valid;
1007     int64_t data_start;
1008     int64_t data_end;
1009 } BdrvBlockStatusCache;
1010 
1011 struct BlockDriverState {
1012     /*
1013      * Protected by big QEMU lock or read-only after opening.  No special
1014      * locking needed during I/O...
1015      */
1016     int open_flags; /* flags used to open the file, re-used for re-open */
1017     bool encrypted; /* if true, the media is encrypted */
1018     bool sg;        /* if true, the device is a /dev/sg* */
1019     bool probed;    /* if true, format was probed rather than specified */
1020     bool force_share; /* if true, always allow all shared permissions */
1021     bool implicit;  /* if true, this filter node was automatically inserted */
1022 
1023     BlockDriver *drv; /* NULL means no media */
1024     void *opaque;
1025 
1026     AioContext *aio_context; /* event loop used for fd handlers, timers, etc */
1027     /*
1028      * long-running tasks intended to always use the same AioContext as this
1029      * BDS may register themselves in this list to be notified of changes
1030      * regarding this BDS's context
1031      */
1032     QLIST_HEAD(, BdrvAioNotifier) aio_notifiers;
1033     bool walking_aio_notifiers; /* to make removal during iteration safe */
1034 
1035     char filename[PATH_MAX];
1036     /*
1037      * If not empty, this image is a diff in relation to backing_file.
1038      * Note that this is the name given in the image header and
1039      * therefore may or may not be equal to .backing->bs->filename.
1040      * If this field contains a relative path, it is to be resolved
1041      * relatively to the overlay's location.
1042      */
1043     char backing_file[PATH_MAX];
1044     /*
1045      * The backing filename indicated by the image header.  Contrary
1046      * to backing_file, if we ever open this file, auto_backing_file
1047      * is replaced by the resulting BDS's filename (i.e. after a
1048      * bdrv_refresh_filename() run).
1049      */
1050     char auto_backing_file[PATH_MAX];
1051     char backing_format[16]; /* if non-zero and backing_file exists */
1052 
1053     QDict *full_open_options;
1054     char exact_filename[PATH_MAX];
1055 
1056     /* I/O Limits */
1057     BlockLimits bl;
1058 
1059     /*
1060      * Flags honored during pread
1061      */
1062     BdrvRequestFlags supported_read_flags;
1063     /*
1064      * Flags honored during pwrite (so far: BDRV_REQ_FUA,
1065      * BDRV_REQ_WRITE_UNCHANGED).
1066      * If a driver does not support BDRV_REQ_WRITE_UNCHANGED, those
1067      * writes will be issued as normal writes without the flag set.
1068      * This is important to note for drivers that do not explicitly
1069      * request a WRITE permission for their children and instead take
1070      * the same permissions as their parent did (this is commonly what
1071      * block filters do).  Such drivers have to be aware that the
1072      * parent may have taken a WRITE_UNCHANGED permission only and is
1073      * issuing such requests.  Drivers either must make sure that
1074      * these requests do not result in plain WRITE accesses (usually
1075      * by supporting BDRV_REQ_WRITE_UNCHANGED, and then forwarding
1076      * every incoming write request as-is, including potentially that
1077      * flag), or they have to explicitly take the WRITE permission for
1078      * their children.
1079      */
1080     BdrvRequestFlags supported_write_flags;
1081     /*
1082      * Flags honored during pwrite_zeroes (so far: BDRV_REQ_FUA,
1083      * BDRV_REQ_MAY_UNMAP, BDRV_REQ_WRITE_UNCHANGED)
1084      */
1085     BdrvRequestFlags supported_zero_flags;
1086     /*
1087      * Flags honoured during truncate (so far: BDRV_REQ_ZERO_WRITE).
1088      *
1089      * If BDRV_REQ_ZERO_WRITE is given, the truncate operation must make sure
1090      * that any added space reads as all zeros. If this can't be guaranteed,
1091      * the operation must fail.
1092      */
1093     BdrvRequestFlags supported_truncate_flags;
1094 
1095     /* the following member gives a name to every node on the bs graph. */
1096     char node_name[32];
1097     /* element of the list of named nodes building the graph */
1098     QTAILQ_ENTRY(BlockDriverState) node_list;
1099     /* element of the list of all BlockDriverStates (all_bdrv_states) */
1100     QTAILQ_ENTRY(BlockDriverState) bs_list;
1101     /* element of the list of monitor-owned BDS */
1102     QTAILQ_ENTRY(BlockDriverState) monitor_list;
1103     int refcnt;
1104 
1105     /* operation blockers. Protected by BQL. */
1106     QLIST_HEAD(, BdrvOpBlocker) op_blockers[BLOCK_OP_TYPE_MAX];
1107 
1108     /*
1109      * The node that this node inherited default options from (and a reopen on
1110      * which can affect this node by changing these defaults). This is always a
1111      * parent node of this node.
1112      */
1113     BlockDriverState *inherits_from;
1114 
1115     /*
1116      * @backing and @file are some of @children or NULL. All these three fields
1117      * (@file, @backing and @children) are modified only in
1118      * bdrv_child_cb_attach() and bdrv_child_cb_detach().
1119      *
1120      * See also comment in include/block/block.h, to learn how backing and file
1121      * are connected with BdrvChildRole.
1122      */
1123     QLIST_HEAD(, BdrvChild) children;
1124     BdrvChild *backing;
1125     BdrvChild *file;
1126 
1127     QLIST_HEAD(, BdrvChild) parents;
1128 
1129     QDict *options;
1130     QDict *explicit_options;
1131     BlockdevDetectZeroesOptions detect_zeroes;
1132 
1133     /* The error object in use for blocking operations on backing_hd */
1134     Error *backing_blocker;
1135 
1136     /* Protected by AioContext lock */
1137 
1138     /*
1139      * If we are reading a disk image, give its size in sectors.
1140      * Generally read-only; it is written to by load_snapshot and
1141      * save_snaphost, but the block layer is quiescent during those.
1142      */
1143     int64_t total_sectors;
1144 
1145     /* threshold limit for writes, in bytes. "High water mark". */
1146     uint64_t write_threshold_offset;
1147 
1148     /*
1149      * Writing to the list requires the BQL _and_ the dirty_bitmap_mutex.
1150      * Reading from the list can be done with either the BQL or the
1151      * dirty_bitmap_mutex.  Modifying a bitmap only requires
1152      * dirty_bitmap_mutex.
1153      */
1154     QemuMutex dirty_bitmap_mutex;
1155     QLIST_HEAD(, BdrvDirtyBitmap) dirty_bitmaps;
1156 
1157     /* Offset after the highest byte written to */
1158     Stat64 wr_highest_offset;
1159 
1160     /*
1161      * If true, copy read backing sectors into image.  Can be >1 if more
1162      * than one client has requested copy-on-read.  Accessed with atomic
1163      * ops.
1164      */
1165     int copy_on_read;
1166 
1167     /*
1168      * number of in-flight requests; overall and serialising.
1169      * Accessed with atomic ops.
1170      */
1171     unsigned int in_flight;
1172     unsigned int serialising_in_flight;
1173 
1174     /*
1175      * counter for nested bdrv_io_plug.
1176      * Accessed with atomic ops.
1177      */
1178     unsigned io_plugged;
1179 
1180     /* do we need to tell the quest if we have a volatile write cache? */
1181     int enable_write_cache;
1182 
1183     /* Accessed with atomic ops.  */
1184     int quiesce_counter;
1185 
1186     unsigned int write_gen;               /* Current data generation */
1187 
1188     /* Protected by reqs_lock.  */
1189     CoMutex reqs_lock;
1190     QLIST_HEAD(, BdrvTrackedRequest) tracked_requests;
1191     CoQueue flush_queue;                  /* Serializing flush queue */
1192     bool active_flush_req;                /* Flush request in flight? */
1193 
1194     /* Only read/written by whoever has set active_flush_req to true.  */
1195     unsigned int flushed_gen;             /* Flushed write generation */
1196 
1197     /* BdrvChild links to this node may never be frozen */
1198     bool never_freeze;
1199 
1200     /* Lock for block-status cache RCU writers */
1201     CoMutex bsc_modify_lock;
1202     /* Always non-NULL, but must only be dereferenced under an RCU read guard */
1203     BdrvBlockStatusCache *block_status_cache;
1204 };
1205 
1206 struct BlockBackendRootState {
1207     int open_flags;
1208     BlockdevDetectZeroesOptions detect_zeroes;
1209 };
1210 
1211 typedef enum BlockMirrorBackingMode {
1212     /*
1213      * Reuse the existing backing chain from the source for the target.
1214      * - sync=full: Set backing BDS to NULL.
1215      * - sync=top:  Use source's backing BDS.
1216      * - sync=none: Use source as the backing BDS.
1217      */
1218     MIRROR_SOURCE_BACKING_CHAIN,
1219 
1220     /* Open the target's backing chain completely anew */
1221     MIRROR_OPEN_BACKING_CHAIN,
1222 
1223     /* Do not change the target's backing BDS after job completion */
1224     MIRROR_LEAVE_BACKING_CHAIN,
1225 } BlockMirrorBackingMode;
1226 
1227 
1228 /*
1229  * Essential block drivers which must always be statically linked into qemu, and
1230  * which therefore can be accessed without using bdrv_find_format()
1231  */
1232 extern BlockDriver bdrv_file;
1233 extern BlockDriver bdrv_raw;
1234 extern BlockDriver bdrv_qcow2;
1235 
1236 extern unsigned int bdrv_drain_all_count;
1237 extern QemuOptsList bdrv_create_opts_simple;
1238 
1239 /*
1240  * Common functions that are neither I/O nor Global State.
1241  *
1242  * See include/block/block-commmon.h for more information about
1243  * the Common API.
1244  */
1245 
1246 static inline BlockDriverState *child_bs(BdrvChild *child)
1247 {
1248     return child ? child->bs : NULL;
1249 }
1250 
1251 int bdrv_check_request(int64_t offset, int64_t bytes, Error **errp);
1252 char *create_tmp_file(Error **errp);
1253 void bdrv_parse_filename_strip_prefix(const char *filename, const char *prefix,
1254                                       QDict *options);
1255 
1256 
1257 int bdrv_check_qiov_request(int64_t offset, int64_t bytes,
1258                             QEMUIOVector *qiov, size_t qiov_offset,
1259                             Error **errp);
1260 
1261 #ifdef _WIN32
1262 int is_windows_drive(const char *filename);
1263 #endif
1264 
1265 #endif /* BLOCK_INT_COMMON_H */
1266