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 (*bdrv_getlength)(BlockDriverState *bs);
684     int64_t (*bdrv_get_allocated_file_size)(BlockDriverState *bs);
685     BlockMeasureInfo *(*bdrv_measure)(QemuOpts *opts, BlockDriverState *in_bs,
686                                       Error **errp);
687 
688     int coroutine_fn (*bdrv_co_pwritev_compressed)(BlockDriverState *bs,
689         int64_t offset, int64_t bytes, QEMUIOVector *qiov);
690     int coroutine_fn (*bdrv_co_pwritev_compressed_part)(BlockDriverState *bs,
691         int64_t offset, int64_t bytes, QEMUIOVector *qiov,
692         size_t qiov_offset);
693 
694     int (*bdrv_get_info)(BlockDriverState *bs, BlockDriverInfo *bdi);
695 
696     ImageInfoSpecific *(*bdrv_get_specific_info)(BlockDriverState *bs,
697                                                  Error **errp);
698     BlockStatsSpecific *(*bdrv_get_specific_stats)(BlockDriverState *bs);
699 
700     int coroutine_fn GRAPH_RDLOCK_PTR (*bdrv_save_vmstate)(
701         BlockDriverState *bs, QEMUIOVector *qiov, int64_t pos);
702 
703     int coroutine_fn GRAPH_RDLOCK_PTR (*bdrv_load_vmstate)(
704         BlockDriverState *bs, QEMUIOVector *qiov, int64_t pos);
705 
706     /* removable device specific */
707     bool (*bdrv_is_inserted)(BlockDriverState *bs);
708     void (*bdrv_eject)(BlockDriverState *bs, bool eject_flag);
709     void (*bdrv_lock_medium)(BlockDriverState *bs, bool locked);
710 
711     /* to control generic scsi devices */
712     BlockAIOCB *(*bdrv_aio_ioctl)(BlockDriverState *bs,
713         unsigned long int req, void *buf,
714         BlockCompletionFunc *cb, void *opaque);
715     int coroutine_fn (*bdrv_co_ioctl)(BlockDriverState *bs,
716                                       unsigned long int req, void *buf);
717 
718     /*
719      * Returns 0 for completed check, -errno for internal errors.
720      * The check results are stored in result.
721      */
722     int coroutine_fn GRAPH_RDLOCK_PTR (*bdrv_co_check)(
723         BlockDriverState *bs, BdrvCheckResult *result, BdrvCheckMode fix);
724 
725     void (*bdrv_debug_event)(BlockDriverState *bs, BlkdebugEvent event);
726 
727     /* io queue for linux-aio */
728     void (*bdrv_io_plug)(BlockDriverState *bs);
729     void (*bdrv_io_unplug)(BlockDriverState *bs);
730 
731     /**
732      * bdrv_drain_begin is called if implemented in the beginning of a
733      * drain operation to drain and stop any internal sources of requests in
734      * the driver.
735      * bdrv_drain_end is called if implemented at the end of the drain.
736      *
737      * They should be used by the driver to e.g. manage scheduled I/O
738      * requests, or toggle an internal state. After the end of the drain new
739      * requests will continue normally.
740      *
741      * Implementations of both functions must not call aio_poll().
742      */
743     void (*bdrv_drain_begin)(BlockDriverState *bs);
744     void (*bdrv_drain_end)(BlockDriverState *bs);
745 
746     bool (*bdrv_supports_persistent_dirty_bitmap)(BlockDriverState *bs);
747     bool coroutine_fn (*bdrv_co_can_store_new_dirty_bitmap)(
748         BlockDriverState *bs, const char *name, uint32_t granularity,
749         Error **errp);
750     int coroutine_fn (*bdrv_co_remove_persistent_dirty_bitmap)(
751         BlockDriverState *bs, const char *name, Error **errp);
752 };
753 
754 static inline bool block_driver_can_compress(BlockDriver *drv)
755 {
756     return drv->bdrv_co_pwritev_compressed ||
757            drv->bdrv_co_pwritev_compressed_part;
758 }
759 
760 typedef struct BlockLimits {
761     /*
762      * Alignment requirement, in bytes, for offset/length of I/O
763      * requests. Must be a power of 2 less than INT_MAX; defaults to
764      * 1 for drivers with modern byte interfaces, and to 512
765      * otherwise.
766      */
767     uint32_t request_alignment;
768 
769     /*
770      * Maximum number of bytes that can be discarded at once. Must be multiple
771      * of pdiscard_alignment, but need not be power of 2. May be 0 if no
772      * inherent 64-bit limit.
773      */
774     int64_t max_pdiscard;
775 
776     /*
777      * Optimal alignment for discard requests in bytes. A power of 2
778      * is best but not mandatory.  Must be a multiple of
779      * bl.request_alignment, and must be less than max_pdiscard if
780      * that is set. May be 0 if bl.request_alignment is good enough
781      */
782     uint32_t pdiscard_alignment;
783 
784     /*
785      * Maximum number of bytes that can zeroized at once. Must be multiple of
786      * pwrite_zeroes_alignment. 0 means no limit.
787      */
788     int64_t max_pwrite_zeroes;
789 
790     /*
791      * Optimal alignment for write zeroes requests in bytes. A power
792      * of 2 is best but not mandatory.  Must be a multiple of
793      * bl.request_alignment, and must be less than max_pwrite_zeroes
794      * if that is set. May be 0 if bl.request_alignment is good
795      * enough
796      */
797     uint32_t pwrite_zeroes_alignment;
798 
799     /*
800      * Optimal transfer length in bytes.  A power of 2 is best but not
801      * mandatory.  Must be a multiple of bl.request_alignment, or 0 if
802      * no preferred size
803      */
804     uint32_t opt_transfer;
805 
806     /*
807      * Maximal transfer length in bytes.  Need not be power of 2, but
808      * must be multiple of opt_transfer and bl.request_alignment, or 0
809      * for no 32-bit limit.  For now, anything larger than INT_MAX is
810      * clamped down.
811      */
812     uint32_t max_transfer;
813 
814     /*
815      * Maximal hardware transfer length in bytes.  Applies whenever
816      * transfers to the device bypass the kernel I/O scheduler, for
817      * example with SG_IO.  If larger than max_transfer or if zero,
818      * blk_get_max_hw_transfer will fall back to max_transfer.
819      */
820     uint64_t max_hw_transfer;
821 
822     /*
823      * Maximal number of scatter/gather elements allowed by the hardware.
824      * Applies whenever transfers to the device bypass the kernel I/O
825      * scheduler, for example with SG_IO.  If larger than max_iov
826      * or if zero, blk_get_max_hw_iov will fall back to max_iov.
827      */
828     int max_hw_iov;
829 
830 
831     /* memory alignment, in bytes so that no bounce buffer is needed */
832     size_t min_mem_alignment;
833 
834     /* memory alignment, in bytes, for bounce buffer */
835     size_t opt_mem_alignment;
836 
837     /* maximum number of iovec elements */
838     int max_iov;
839 } BlockLimits;
840 
841 typedef struct BdrvOpBlocker BdrvOpBlocker;
842 
843 typedef struct BdrvAioNotifier {
844     void (*attached_aio_context)(AioContext *new_context, void *opaque);
845     void (*detach_aio_context)(void *opaque);
846 
847     void *opaque;
848     bool deleted;
849 
850     QLIST_ENTRY(BdrvAioNotifier) list;
851 } BdrvAioNotifier;
852 
853 struct BdrvChildClass {
854     /*
855      * If true, bdrv_replace_node() doesn't change the node this BdrvChild
856      * points to.
857      */
858     bool stay_at_node;
859 
860     /*
861      * If true, the parent is a BlockDriverState and bdrv_next_all_states()
862      * will return it. This information is used for drain_all, where every node
863      * will be drained separately, so the drain only needs to be propagated to
864      * non-BDS parents.
865      */
866     bool parent_is_bds;
867 
868     /*
869      * Global state (GS) API. These functions run under the BQL.
870      *
871      * See include/block/block-global-state.h for more information about
872      * the GS API.
873      */
874     void (*inherit_options)(BdrvChildRole role, bool parent_is_format,
875                             int *child_flags, QDict *child_options,
876                             int parent_flags, QDict *parent_options);
877     void (*change_media)(BdrvChild *child, bool load);
878 
879     /*
880      * Returns a malloced string that describes the parent of the child for a
881      * human reader. This could be a node-name, BlockBackend name, qdev ID or
882      * QOM path of the device owning the BlockBackend, job type and ID etc. The
883      * caller is responsible for freeing the memory.
884      */
885     char *(*get_parent_desc)(BdrvChild *child);
886 
887     /*
888      * Notifies the parent that the child has been activated/inactivated (e.g.
889      * when migration is completing) and it can start/stop requesting
890      * permissions and doing I/O on it.
891      */
892     void (*activate)(BdrvChild *child, Error **errp);
893     int (*inactivate)(BdrvChild *child);
894 
895     void GRAPH_WRLOCK_PTR (*attach)(BdrvChild *child);
896     void GRAPH_WRLOCK_PTR (*detach)(BdrvChild *child);
897 
898     /*
899      * Notifies the parent that the filename of its child has changed (e.g.
900      * because the direct child was removed from the backing chain), so that it
901      * can update its reference.
902      */
903     int (*update_filename)(BdrvChild *child, BlockDriverState *new_base,
904                            const char *filename, Error **errp);
905 
906     bool (*change_aio_ctx)(BdrvChild *child, AioContext *ctx,
907                            GHashTable *visited, Transaction *tran,
908                            Error **errp);
909 
910     /*
911      * I/O API functions. These functions are thread-safe.
912      *
913      * See include/block/block-io.h for more information about
914      * the I/O API.
915      */
916 
917     void (*resize)(BdrvChild *child);
918 
919     /*
920      * Returns a name that is supposedly more useful for human users than the
921      * node name for identifying the node in question (in particular, a BB
922      * name), or NULL if the parent can't provide a better name.
923      */
924     const char *(*get_name)(BdrvChild *child);
925 
926     AioContext *(*get_parent_aio_context)(BdrvChild *child);
927 
928     /*
929      * If this pair of functions is implemented, the parent doesn't issue new
930      * requests after returning from .drained_begin() until .drained_end() is
931      * called.
932      *
933      * These functions must not change the graph (and therefore also must not
934      * call aio_poll(), which could change the graph indirectly).
935      *
936      * Note that this can be nested. If drained_begin() was called twice, new
937      * I/O is allowed only after drained_end() was called twice, too.
938      */
939     void (*drained_begin)(BdrvChild *child);
940     void (*drained_end)(BdrvChild *child);
941 
942     /*
943      * Returns whether the parent has pending requests for the child. This
944      * callback is polled after .drained_begin() has been called until all
945      * activity on the child has stopped.
946      */
947     bool (*drained_poll)(BdrvChild *child);
948 };
949 
950 extern const BdrvChildClass child_of_bds;
951 
952 struct BdrvChild {
953     BlockDriverState *bs;
954     char *name;
955     const BdrvChildClass *klass;
956     BdrvChildRole role;
957     void *opaque;
958 
959     /**
960      * Granted permissions for operating on this BdrvChild (BLK_PERM_* bitmask)
961      */
962     uint64_t perm;
963 
964     /**
965      * Permissions that can still be granted to other users of @bs while this
966      * BdrvChild is still attached to it. (BLK_PERM_* bitmask)
967      */
968     uint64_t shared_perm;
969 
970     /*
971      * This link is frozen: the child can neither be replaced nor
972      * detached from the parent.
973      */
974     bool frozen;
975 
976     /*
977      * True if the parent of this child has been drained by this BdrvChild
978      * (through klass->drained_*).
979      *
980      * It is generally true if bs->quiesce_counter > 0. It may differ while the
981      * child is entering or leaving a drained section.
982      */
983     bool quiesced_parent;
984 
985     QLIST_ENTRY(BdrvChild) next;
986     QLIST_ENTRY(BdrvChild) next_parent;
987 };
988 
989 /*
990  * Allows bdrv_co_block_status() to cache one data region for a
991  * protocol node.
992  *
993  * @valid: Whether the cache is valid (should be accessed with atomic
994  *         functions so this can be reset by RCU readers)
995  * @data_start: Offset where we know (or strongly assume) is data
996  * @data_end: Offset where the data region ends (which is not necessarily
997  *            the start of a zeroed region)
998  */
999 typedef struct BdrvBlockStatusCache {
1000     struct rcu_head rcu;
1001 
1002     bool valid;
1003     int64_t data_start;
1004     int64_t data_end;
1005 } BdrvBlockStatusCache;
1006 
1007 struct BlockDriverState {
1008     /*
1009      * Protected by big QEMU lock or read-only after opening.  No special
1010      * locking needed during I/O...
1011      */
1012     int open_flags; /* flags used to open the file, re-used for re-open */
1013     bool encrypted; /* if true, the media is encrypted */
1014     bool sg;        /* if true, the device is a /dev/sg* */
1015     bool probed;    /* if true, format was probed rather than specified */
1016     bool force_share; /* if true, always allow all shared permissions */
1017     bool implicit;  /* if true, this filter node was automatically inserted */
1018 
1019     BlockDriver *drv; /* NULL means no media */
1020     void *opaque;
1021 
1022     AioContext *aio_context; /* event loop used for fd handlers, timers, etc */
1023     /*
1024      * long-running tasks intended to always use the same AioContext as this
1025      * BDS may register themselves in this list to be notified of changes
1026      * regarding this BDS's context
1027      */
1028     QLIST_HEAD(, BdrvAioNotifier) aio_notifiers;
1029     bool walking_aio_notifiers; /* to make removal during iteration safe */
1030 
1031     char filename[PATH_MAX];
1032     /*
1033      * If not empty, this image is a diff in relation to backing_file.
1034      * Note that this is the name given in the image header and
1035      * therefore may or may not be equal to .backing->bs->filename.
1036      * If this field contains a relative path, it is to be resolved
1037      * relatively to the overlay's location.
1038      */
1039     char backing_file[PATH_MAX];
1040     /*
1041      * The backing filename indicated by the image header.  Contrary
1042      * to backing_file, if we ever open this file, auto_backing_file
1043      * is replaced by the resulting BDS's filename (i.e. after a
1044      * bdrv_refresh_filename() run).
1045      */
1046     char auto_backing_file[PATH_MAX];
1047     char backing_format[16]; /* if non-zero and backing_file exists */
1048 
1049     QDict *full_open_options;
1050     char exact_filename[PATH_MAX];
1051 
1052     /* I/O Limits */
1053     BlockLimits bl;
1054 
1055     /*
1056      * Flags honored during pread
1057      */
1058     BdrvRequestFlags supported_read_flags;
1059     /*
1060      * Flags honored during pwrite (so far: BDRV_REQ_FUA,
1061      * BDRV_REQ_WRITE_UNCHANGED).
1062      * If a driver does not support BDRV_REQ_WRITE_UNCHANGED, those
1063      * writes will be issued as normal writes without the flag set.
1064      * This is important to note for drivers that do not explicitly
1065      * request a WRITE permission for their children and instead take
1066      * the same permissions as their parent did (this is commonly what
1067      * block filters do).  Such drivers have to be aware that the
1068      * parent may have taken a WRITE_UNCHANGED permission only and is
1069      * issuing such requests.  Drivers either must make sure that
1070      * these requests do not result in plain WRITE accesses (usually
1071      * by supporting BDRV_REQ_WRITE_UNCHANGED, and then forwarding
1072      * every incoming write request as-is, including potentially that
1073      * flag), or they have to explicitly take the WRITE permission for
1074      * their children.
1075      */
1076     BdrvRequestFlags supported_write_flags;
1077     /*
1078      * Flags honored during pwrite_zeroes (so far: BDRV_REQ_FUA,
1079      * BDRV_REQ_MAY_UNMAP, BDRV_REQ_WRITE_UNCHANGED)
1080      */
1081     BdrvRequestFlags supported_zero_flags;
1082     /*
1083      * Flags honoured during truncate (so far: BDRV_REQ_ZERO_WRITE).
1084      *
1085      * If BDRV_REQ_ZERO_WRITE is given, the truncate operation must make sure
1086      * that any added space reads as all zeros. If this can't be guaranteed,
1087      * the operation must fail.
1088      */
1089     BdrvRequestFlags supported_truncate_flags;
1090 
1091     /* the following member gives a name to every node on the bs graph. */
1092     char node_name[32];
1093     /* element of the list of named nodes building the graph */
1094     QTAILQ_ENTRY(BlockDriverState) node_list;
1095     /* element of the list of all BlockDriverStates (all_bdrv_states) */
1096     QTAILQ_ENTRY(BlockDriverState) bs_list;
1097     /* element of the list of monitor-owned BDS */
1098     QTAILQ_ENTRY(BlockDriverState) monitor_list;
1099     int refcnt;
1100 
1101     /* operation blockers. Protected by BQL. */
1102     QLIST_HEAD(, BdrvOpBlocker) op_blockers[BLOCK_OP_TYPE_MAX];
1103 
1104     /*
1105      * The node that this node inherited default options from (and a reopen on
1106      * which can affect this node by changing these defaults). This is always a
1107      * parent node of this node.
1108      */
1109     BlockDriverState *inherits_from;
1110 
1111     /*
1112      * @backing and @file are some of @children or NULL. All these three fields
1113      * (@file, @backing and @children) are modified only in
1114      * bdrv_child_cb_attach() and bdrv_child_cb_detach().
1115      *
1116      * See also comment in include/block/block.h, to learn how backing and file
1117      * are connected with BdrvChildRole.
1118      */
1119     QLIST_HEAD(, BdrvChild) children;
1120     BdrvChild *backing;
1121     BdrvChild *file;
1122 
1123     QLIST_HEAD(, BdrvChild) parents;
1124 
1125     QDict *options;
1126     QDict *explicit_options;
1127     BlockdevDetectZeroesOptions detect_zeroes;
1128 
1129     /* The error object in use for blocking operations on backing_hd */
1130     Error *backing_blocker;
1131 
1132     /* Protected by AioContext lock */
1133 
1134     /*
1135      * If we are reading a disk image, give its size in sectors.
1136      * Generally read-only; it is written to by load_snapshot and
1137      * save_snaphost, but the block layer is quiescent during those.
1138      */
1139     int64_t total_sectors;
1140 
1141     /* threshold limit for writes, in bytes. "High water mark". */
1142     uint64_t write_threshold_offset;
1143 
1144     /*
1145      * Writing to the list requires the BQL _and_ the dirty_bitmap_mutex.
1146      * Reading from the list can be done with either the BQL or the
1147      * dirty_bitmap_mutex.  Modifying a bitmap only requires
1148      * dirty_bitmap_mutex.
1149      */
1150     QemuMutex dirty_bitmap_mutex;
1151     QLIST_HEAD(, BdrvDirtyBitmap) dirty_bitmaps;
1152 
1153     /* Offset after the highest byte written to */
1154     Stat64 wr_highest_offset;
1155 
1156     /*
1157      * If true, copy read backing sectors into image.  Can be >1 if more
1158      * than one client has requested copy-on-read.  Accessed with atomic
1159      * ops.
1160      */
1161     int copy_on_read;
1162 
1163     /*
1164      * number of in-flight requests; overall and serialising.
1165      * Accessed with atomic ops.
1166      */
1167     unsigned int in_flight;
1168     unsigned int serialising_in_flight;
1169 
1170     /*
1171      * counter for nested bdrv_io_plug.
1172      * Accessed with atomic ops.
1173      */
1174     unsigned io_plugged;
1175 
1176     /* do we need to tell the quest if we have a volatile write cache? */
1177     int enable_write_cache;
1178 
1179     /* Accessed with atomic ops.  */
1180     int quiesce_counter;
1181 
1182     unsigned int write_gen;               /* Current data generation */
1183 
1184     /* Protected by reqs_lock.  */
1185     CoMutex reqs_lock;
1186     QLIST_HEAD(, BdrvTrackedRequest) tracked_requests;
1187     CoQueue flush_queue;                  /* Serializing flush queue */
1188     bool active_flush_req;                /* Flush request in flight? */
1189 
1190     /* Only read/written by whoever has set active_flush_req to true.  */
1191     unsigned int flushed_gen;             /* Flushed write generation */
1192 
1193     /* BdrvChild links to this node may never be frozen */
1194     bool never_freeze;
1195 
1196     /* Lock for block-status cache RCU writers */
1197     CoMutex bsc_modify_lock;
1198     /* Always non-NULL, but must only be dereferenced under an RCU read guard */
1199     BdrvBlockStatusCache *block_status_cache;
1200 };
1201 
1202 struct BlockBackendRootState {
1203     int open_flags;
1204     BlockdevDetectZeroesOptions detect_zeroes;
1205 };
1206 
1207 typedef enum BlockMirrorBackingMode {
1208     /*
1209      * Reuse the existing backing chain from the source for the target.
1210      * - sync=full: Set backing BDS to NULL.
1211      * - sync=top:  Use source's backing BDS.
1212      * - sync=none: Use source as the backing BDS.
1213      */
1214     MIRROR_SOURCE_BACKING_CHAIN,
1215 
1216     /* Open the target's backing chain completely anew */
1217     MIRROR_OPEN_BACKING_CHAIN,
1218 
1219     /* Do not change the target's backing BDS after job completion */
1220     MIRROR_LEAVE_BACKING_CHAIN,
1221 } BlockMirrorBackingMode;
1222 
1223 
1224 /*
1225  * Essential block drivers which must always be statically linked into qemu, and
1226  * which therefore can be accessed without using bdrv_find_format()
1227  */
1228 extern BlockDriver bdrv_file;
1229 extern BlockDriver bdrv_raw;
1230 extern BlockDriver bdrv_qcow2;
1231 
1232 extern unsigned int bdrv_drain_all_count;
1233 extern QemuOptsList bdrv_create_opts_simple;
1234 
1235 /*
1236  * Common functions that are neither I/O nor Global State.
1237  *
1238  * See include/block/block-commmon.h for more information about
1239  * the Common API.
1240  */
1241 
1242 static inline BlockDriverState *child_bs(BdrvChild *child)
1243 {
1244     return child ? child->bs : NULL;
1245 }
1246 
1247 int bdrv_check_request(int64_t offset, int64_t bytes, Error **errp);
1248 char *create_tmp_file(Error **errp);
1249 void bdrv_parse_filename_strip_prefix(const char *filename, const char *prefix,
1250                                       QDict *options);
1251 
1252 
1253 int bdrv_check_qiov_request(int64_t offset, int64_t bytes,
1254                             QEMUIOVector *qiov, size_t qiov_offset,
1255                             Error **errp);
1256 
1257 #ifdef _WIN32
1258 int is_windows_drive(const char *filename);
1259 #endif
1260 
1261 #endif /* BLOCK_INT_COMMON_H */
1262