6 #include "qemu/option.h"
7 #include "qemu/coroutine.h"
8 #include "block/accounting.h"
9 #include "block/dirty-bitmap.h"
10 #include "qapi/qmp/qobject.h"
11 #include "qapi-types.h"
12 #include "qemu/hbitmap.h"
15 typedef struct BlockDriver BlockDriver;
16 typedef struct BlockJob BlockJob;
17 typedef struct BdrvChild BdrvChild;
18 typedef struct BdrvChildRole BdrvChildRole;
19 typedef struct BlockJobTxn BlockJobTxn;
21 typedef struct BlockDriverInfo {
22 /* in bytes, 0 if irrelevant */
24 /* offset at which the VM state can be saved (0 if not possible) */
25 int64_t vm_state_offset;
28 * True if unallocated blocks read back as zeroes. This is equivalent
29 * to the LBPRZ flag in the SCSI logical block provisioning page.
31 bool unallocated_blocks_are_zero;
33 * True if the driver can optimize writing zeroes by unmapping
34 * sectors. This is equivalent to the BLKDISCARDZEROES ioctl in Linux
35 * with the difference that in qemu a discard is allowed to silently
36 * fail. Therefore we have to use bdrv_pwrite_zeroes with the
37 * BDRV_REQ_MAY_UNMAP flag for an optimized zero write with unmapping.
38 * After this call the driver has to guarantee that the contents read
39 * back as zero. It is additionally required that the block device is
40 * opened with BDRV_O_UNMAP flag for this to work.
42 bool can_write_zeroes_with_unmap;
44 * True if this block driver only supports compressed writes
46 bool needs_compressed_writes;
49 typedef struct BlockFragInfo {
50 uint64_t allocated_clusters;
51 uint64_t total_clusters;
52 uint64_t fragmented_clusters;
53 uint64_t compressed_clusters;
57 BDRV_REQ_COPY_ON_READ = 0x1,
58 BDRV_REQ_ZERO_WRITE = 0x2,
59 /* The BDRV_REQ_MAY_UNMAP flag is used to indicate that the block driver
60 * is allowed to optimize a write zeroes request by unmapping (discarding)
61 * blocks if it is guaranteed that the result will read back as
62 * zeroes. The flag is only passed to the driver if the block device is
63 * opened with BDRV_O_UNMAP.
65 BDRV_REQ_MAY_UNMAP = 0x4,
66 BDRV_REQ_NO_SERIALISING = 0x8,
68 BDRV_REQ_WRITE_COMPRESSED = 0x20,
70 /* Mask of valid flags */
74 typedef struct BlockSizes {
79 typedef struct HDGeometry {
85 #define BDRV_O_RDWR 0x0002
86 #define BDRV_O_SNAPSHOT 0x0008 /* open the file read only and save writes in a snapshot */
87 #define BDRV_O_TEMPORARY 0x0010 /* delete the file after use */
88 #define BDRV_O_NOCACHE 0x0020 /* do not use the host page cache */
89 #define BDRV_O_NATIVE_AIO 0x0080 /* use native AIO instead of the thread pool */
90 #define BDRV_O_NO_BACKING 0x0100 /* don't open the backing file */
91 #define BDRV_O_NO_FLUSH 0x0200 /* disable flushing on this disk */
92 #define BDRV_O_COPY_ON_READ 0x0400 /* copy read backing sectors into image */
93 #define BDRV_O_INACTIVE 0x0800 /* consistency hint for migration handoff */
94 #define BDRV_O_CHECK 0x1000 /* open solely for consistency check */
95 #define BDRV_O_ALLOW_RDWR 0x2000 /* allow reopen to change from r/o to r/w */
96 #define BDRV_O_UNMAP 0x4000 /* execute guest UNMAP/TRIM operations */
97 #define BDRV_O_PROTOCOL 0x8000 /* if no block driver is explicitly given:
98 select an appropriate protocol driver,
99 ignoring the format layer */
100 #define BDRV_O_NO_IO 0x10000 /* don't initialize for I/O */
102 #define BDRV_O_CACHE_MASK (BDRV_O_NOCACHE | BDRV_O_NO_FLUSH)
105 /* Option names of options parsed by the block layer */
107 #define BDRV_OPT_CACHE_WB "cache.writeback"
108 #define BDRV_OPT_CACHE_DIRECT "cache.direct"
109 #define BDRV_OPT_CACHE_NO_FLUSH "cache.no-flush"
112 #define BDRV_SECTOR_BITS 9
113 #define BDRV_SECTOR_SIZE (1ULL << BDRV_SECTOR_BITS)
114 #define BDRV_SECTOR_MASK ~(BDRV_SECTOR_SIZE - 1)
116 #define BDRV_REQUEST_MAX_SECTORS MIN(SIZE_MAX >> BDRV_SECTOR_BITS, \
117 INT_MAX >> BDRV_SECTOR_BITS)
120 * Allocation status flags
121 * BDRV_BLOCK_DATA: data is read from a file returned by bdrv_get_block_status.
122 * BDRV_BLOCK_ZERO: sectors read as zero
123 * BDRV_BLOCK_OFFSET_VALID: sector stored as raw data in a file returned by
124 * bdrv_get_block_status.
125 * BDRV_BLOCK_ALLOCATED: the content of the block is determined by this
126 * layer (as opposed to the backing file)
127 * BDRV_BLOCK_RAW: used internally to indicate that the request
128 * was answered by the raw driver and that one
129 * should look in bs->file directly.
131 * If BDRV_BLOCK_OFFSET_VALID is set, bits 9-62 represent the offset in
132 * bs->file where sector data can be read from as raw data.
134 * DATA == 0 && ZERO == 0 means that data is read from backing_hd if present.
136 * DATA ZERO OFFSET_VALID
137 * t t t sectors read as zero, bs->file is zero at offset
138 * t f t sectors read as valid from bs->file at offset
139 * f t t sectors preallocated, read as zero, bs->file not
140 * necessarily zero at offset
141 * f f t sectors preallocated but read from backing_hd,
142 * bs->file contains garbage at offset
143 * t t f sectors preallocated, read as zero, unknown offset
144 * t f f sectors read from unknown file or offset
145 * f t f not allocated or unknown offset, read as zero
146 * f f f not allocated or unknown offset, read from backing_hd
148 #define BDRV_BLOCK_DATA 0x01
149 #define BDRV_BLOCK_ZERO 0x02
150 #define BDRV_BLOCK_OFFSET_VALID 0x04
151 #define BDRV_BLOCK_RAW 0x08
152 #define BDRV_BLOCK_ALLOCATED 0x10
153 #define BDRV_BLOCK_OFFSET_MASK BDRV_SECTOR_MASK
155 typedef QSIMPLEQ_HEAD(BlockReopenQueue, BlockReopenQueueEntry) BlockReopenQueue;
157 typedef struct BDRVReopenState {
158 BlockDriverState *bs;
161 QDict *explicit_options;
166 * Block operation types
168 typedef enum BlockOpType {
169 BLOCK_OP_TYPE_BACKUP_SOURCE,
170 BLOCK_OP_TYPE_BACKUP_TARGET,
171 BLOCK_OP_TYPE_CHANGE,
172 BLOCK_OP_TYPE_COMMIT_SOURCE,
173 BLOCK_OP_TYPE_COMMIT_TARGET,
174 BLOCK_OP_TYPE_DATAPLANE,
175 BLOCK_OP_TYPE_DRIVE_DEL,
177 BLOCK_OP_TYPE_EXTERNAL_SNAPSHOT,
178 BLOCK_OP_TYPE_INTERNAL_SNAPSHOT,
179 BLOCK_OP_TYPE_INTERNAL_SNAPSHOT_DELETE,
180 BLOCK_OP_TYPE_MIRROR_SOURCE,
181 BLOCK_OP_TYPE_MIRROR_TARGET,
182 BLOCK_OP_TYPE_RESIZE,
183 BLOCK_OP_TYPE_STREAM,
184 BLOCK_OP_TYPE_REPLACE,
188 void bdrv_info_print(Monitor *mon, const QObject *data);
189 void bdrv_info(Monitor *mon, QObject **ret_data);
190 void bdrv_stats_print(Monitor *mon, const QObject *data);
191 void bdrv_info_stats(Monitor *mon, QObject **ret_data);
193 /* disk I/O throttling */
194 void bdrv_init(void);
195 void bdrv_init_with_whitelist(void);
196 bool bdrv_uses_whitelist(void);
197 BlockDriver *bdrv_find_protocol(const char *filename,
198 bool allow_protocol_prefix,
200 BlockDriver *bdrv_find_format(const char *format_name);
201 int bdrv_create(BlockDriver *drv, const char* filename,
202 QemuOpts *opts, Error **errp);
203 int bdrv_create_file(const char *filename, QemuOpts *opts, Error **errp);
204 BlockDriverState *bdrv_new(void);
205 void bdrv_append(BlockDriverState *bs_new, BlockDriverState *bs_top);
206 void bdrv_replace_in_backing_chain(BlockDriverState *old,
207 BlockDriverState *new);
209 int bdrv_parse_cache_mode(const char *mode, int *flags, bool *writethrough);
210 int bdrv_parse_discard_flags(const char *mode, int *flags);
211 BdrvChild *bdrv_open_child(const char *filename,
212 QDict *options, const char *bdref_key,
213 BlockDriverState* parent,
214 const BdrvChildRole *child_role,
215 bool allow_none, Error **errp);
216 void bdrv_set_backing_hd(BlockDriverState *bs, BlockDriverState *backing_hd);
217 int bdrv_open_backing_file(BlockDriverState *bs, QDict *parent_options,
218 const char *bdref_key, Error **errp);
219 BlockDriverState *bdrv_open(const char *filename, const char *reference,
220 QDict *options, int flags, Error **errp);
221 BlockReopenQueue *bdrv_reopen_queue(BlockReopenQueue *bs_queue,
222 BlockDriverState *bs,
223 QDict *options, int flags);
224 int bdrv_reopen_multiple(BlockReopenQueue *bs_queue, Error **errp);
225 int bdrv_reopen(BlockDriverState *bs, int bdrv_flags, Error **errp);
226 int bdrv_reopen_prepare(BDRVReopenState *reopen_state,
227 BlockReopenQueue *queue, Error **errp);
228 void bdrv_reopen_commit(BDRVReopenState *reopen_state);
229 void bdrv_reopen_abort(BDRVReopenState *reopen_state);
230 int bdrv_read(BdrvChild *child, int64_t sector_num,
231 uint8_t *buf, int nb_sectors);
232 int bdrv_write(BdrvChild *child, int64_t sector_num,
233 const uint8_t *buf, int nb_sectors);
234 int bdrv_pwrite_zeroes(BdrvChild *child, int64_t offset,
235 int count, BdrvRequestFlags flags);
236 int bdrv_make_zero(BdrvChild *child, BdrvRequestFlags flags);
237 int bdrv_pread(BdrvChild *child, int64_t offset, void *buf, int bytes);
238 int bdrv_preadv(BdrvChild *child, int64_t offset, QEMUIOVector *qiov);
239 int bdrv_pwrite(BdrvChild *child, int64_t offset, const void *buf, int bytes);
240 int bdrv_pwritev(BdrvChild *child, int64_t offset, QEMUIOVector *qiov);
241 int bdrv_pwrite_sync(BdrvChild *child, int64_t offset,
242 const void *buf, int count);
243 int coroutine_fn bdrv_co_readv(BdrvChild *child, int64_t sector_num,
244 int nb_sectors, QEMUIOVector *qiov);
245 int coroutine_fn bdrv_co_writev(BdrvChild *child, int64_t sector_num,
246 int nb_sectors, QEMUIOVector *qiov);
248 * Efficiently zero a region of the disk image. Note that this is a regular
249 * I/O request like read or write and should have a reasonable size. This
250 * function is not suitable for zeroing the entire image in a single request
251 * because it may allocate memory for the entire region.
253 int coroutine_fn bdrv_co_pwrite_zeroes(BdrvChild *child, int64_t offset,
254 int count, BdrvRequestFlags flags);
255 BlockDriverState *bdrv_find_backing_image(BlockDriverState *bs,
256 const char *backing_file);
257 int bdrv_get_backing_file_depth(BlockDriverState *bs);
258 void bdrv_refresh_filename(BlockDriverState *bs);
259 int bdrv_truncate(BlockDriverState *bs, int64_t offset);
260 int64_t bdrv_nb_sectors(BlockDriverState *bs);
261 int64_t bdrv_getlength(BlockDriverState *bs);
262 int64_t bdrv_get_allocated_file_size(BlockDriverState *bs);
263 void bdrv_get_geometry(BlockDriverState *bs, uint64_t *nb_sectors_ptr);
264 void bdrv_refresh_limits(BlockDriverState *bs, Error **errp);
265 int bdrv_commit(BlockDriverState *bs);
266 int bdrv_change_backing_file(BlockDriverState *bs,
267 const char *backing_file, const char *backing_fmt);
268 void bdrv_register(BlockDriver *bdrv);
269 int bdrv_drop_intermediate(BlockDriverState *active, BlockDriverState *top,
270 BlockDriverState *base,
271 const char *backing_file_str);
272 BlockDriverState *bdrv_find_overlay(BlockDriverState *active,
273 BlockDriverState *bs);
274 BlockDriverState *bdrv_find_base(BlockDriverState *bs);
277 typedef struct BdrvCheckResult {
281 int corruptions_fixed;
283 int64_t image_end_offset;
292 int bdrv_check(BlockDriverState *bs, BdrvCheckResult *res, BdrvCheckMode fix);
294 /* The units of offset and total_work_size may be chosen arbitrarily by the
295 * block driver; total_work_size may change during the course of the amendment
297 typedef void BlockDriverAmendStatusCB(BlockDriverState *bs, int64_t offset,
298 int64_t total_work_size, void *opaque);
299 int bdrv_amend_options(BlockDriverState *bs_new, QemuOpts *opts,
300 BlockDriverAmendStatusCB *status_cb, void *cb_opaque);
302 /* external snapshots */
303 bool bdrv_recurse_is_first_non_filter(BlockDriverState *bs,
304 BlockDriverState *candidate);
305 bool bdrv_is_first_non_filter(BlockDriverState *candidate);
307 /* check if a named node can be replaced when doing drive-mirror */
308 BlockDriverState *check_to_replace_node(BlockDriverState *parent_bs,
309 const char *node_name, Error **errp);
311 /* async block I/O */
312 BlockAIOCB *bdrv_aio_readv(BdrvChild *child, int64_t sector_num,
313 QEMUIOVector *iov, int nb_sectors,
314 BlockCompletionFunc *cb, void *opaque);
315 BlockAIOCB *bdrv_aio_writev(BdrvChild *child, int64_t sector_num,
316 QEMUIOVector *iov, int nb_sectors,
317 BlockCompletionFunc *cb, void *opaque);
318 BlockAIOCB *bdrv_aio_flush(BlockDriverState *bs,
319 BlockCompletionFunc *cb, void *opaque);
320 BlockAIOCB *bdrv_aio_pdiscard(BlockDriverState *bs,
321 int64_t offset, int count,
322 BlockCompletionFunc *cb, void *opaque);
323 void bdrv_aio_cancel(BlockAIOCB *acb);
324 void bdrv_aio_cancel_async(BlockAIOCB *acb);
326 /* sg packet commands */
327 int bdrv_ioctl(BlockDriverState *bs, unsigned long int req, void *buf);
328 BlockAIOCB *bdrv_aio_ioctl(BlockDriverState *bs,
329 unsigned long int req, void *buf,
330 BlockCompletionFunc *cb, void *opaque);
332 /* Invalidate any cached metadata used by image formats */
333 void bdrv_invalidate_cache(BlockDriverState *bs, Error **errp);
334 void bdrv_invalidate_cache_all(Error **errp);
335 int bdrv_inactivate_all(void);
337 /* Ensure contents are flushed to disk. */
338 int bdrv_flush(BlockDriverState *bs);
339 int coroutine_fn bdrv_co_flush(BlockDriverState *bs);
340 void bdrv_close_all(void);
341 void bdrv_drain(BlockDriverState *bs);
342 void coroutine_fn bdrv_co_drain(BlockDriverState *bs);
343 void bdrv_drain_all(void);
345 int bdrv_pdiscard(BlockDriverState *bs, int64_t offset, int count);
346 int bdrv_co_pdiscard(BlockDriverState *bs, int64_t offset, int count);
347 int bdrv_has_zero_init_1(BlockDriverState *bs);
348 int bdrv_has_zero_init(BlockDriverState *bs);
349 bool bdrv_unallocated_blocks_are_zero(BlockDriverState *bs);
350 bool bdrv_can_write_zeroes_with_unmap(BlockDriverState *bs);
351 int64_t bdrv_get_block_status(BlockDriverState *bs, int64_t sector_num,
352 int nb_sectors, int *pnum,
353 BlockDriverState **file);
354 int64_t bdrv_get_block_status_above(BlockDriverState *bs,
355 BlockDriverState *base,
357 int nb_sectors, int *pnum,
358 BlockDriverState **file);
359 int bdrv_is_allocated(BlockDriverState *bs, int64_t sector_num, int nb_sectors,
361 int bdrv_is_allocated_above(BlockDriverState *top, BlockDriverState *base,
362 int64_t sector_num, int nb_sectors, int *pnum);
364 bool bdrv_is_read_only(BlockDriverState *bs);
365 bool bdrv_is_sg(BlockDriverState *bs);
366 bool bdrv_is_inserted(BlockDriverState *bs);
367 int bdrv_media_changed(BlockDriverState *bs);
368 void bdrv_lock_medium(BlockDriverState *bs, bool locked);
369 void bdrv_eject(BlockDriverState *bs, bool eject_flag);
370 const char *bdrv_get_format_name(BlockDriverState *bs);
371 BlockDriverState *bdrv_find_node(const char *node_name);
372 BlockDeviceInfoList *bdrv_named_nodes_list(Error **errp);
373 BlockDriverState *bdrv_lookup_bs(const char *device,
374 const char *node_name,
376 bool bdrv_chain_contains(BlockDriverState *top, BlockDriverState *base);
377 BlockDriverState *bdrv_next_node(BlockDriverState *bs);
379 typedef struct BdrvNextIterator {
381 BDRV_NEXT_BACKEND_ROOTS,
382 BDRV_NEXT_MONITOR_OWNED,
385 BlockDriverState *bs;
388 BlockDriverState *bdrv_first(BdrvNextIterator *it);
389 BlockDriverState *bdrv_next(BdrvNextIterator *it);
391 BlockDriverState *bdrv_next_monitor_owned(BlockDriverState *bs);
392 bool bdrv_is_encrypted(BlockDriverState *bs);
393 bool bdrv_key_required(BlockDriverState *bs);
394 int bdrv_set_key(BlockDriverState *bs, const char *key);
395 void bdrv_add_key(BlockDriverState *bs, const char *key, Error **errp);
396 int bdrv_query_missing_keys(void);
397 void bdrv_iterate_format(void (*it)(void *opaque, const char *name),
399 const char *bdrv_get_node_name(const BlockDriverState *bs);
400 const char *bdrv_get_device_name(const BlockDriverState *bs);
401 const char *bdrv_get_device_or_node_name(const BlockDriverState *bs);
402 int bdrv_get_flags(BlockDriverState *bs);
403 int bdrv_get_info(BlockDriverState *bs, BlockDriverInfo *bdi);
404 ImageInfoSpecific *bdrv_get_specific_info(BlockDriverState *bs);
405 void bdrv_round_sectors_to_clusters(BlockDriverState *bs,
406 int64_t sector_num, int nb_sectors,
407 int64_t *cluster_sector_num,
408 int *cluster_nb_sectors);
409 void bdrv_round_to_clusters(BlockDriverState *bs,
410 int64_t offset, unsigned int bytes,
411 int64_t *cluster_offset,
412 unsigned int *cluster_bytes);
414 const char *bdrv_get_encrypted_filename(BlockDriverState *bs);
415 void bdrv_get_backing_filename(BlockDriverState *bs,
416 char *filename, int filename_size);
417 void bdrv_get_full_backing_filename(BlockDriverState *bs,
418 char *dest, size_t sz, Error **errp);
419 void bdrv_get_full_backing_filename_from_filename(const char *backed,
421 char *dest, size_t sz,
423 int bdrv_is_snapshot(BlockDriverState *bs);
425 int path_has_protocol(const char *path);
426 int path_is_absolute(const char *path);
427 void path_combine(char *dest, int dest_size,
428 const char *base_path,
429 const char *filename);
431 int bdrv_readv_vmstate(BlockDriverState *bs, QEMUIOVector *qiov, int64_t pos);
432 int bdrv_writev_vmstate(BlockDriverState *bs, QEMUIOVector *qiov, int64_t pos);
433 int bdrv_save_vmstate(BlockDriverState *bs, const uint8_t *buf,
434 int64_t pos, int size);
436 int bdrv_load_vmstate(BlockDriverState *bs, uint8_t *buf,
437 int64_t pos, int size);
439 void bdrv_img_create(const char *filename, const char *fmt,
440 const char *base_filename, const char *base_fmt,
441 char *options, uint64_t img_size, int flags,
442 Error **errp, bool quiet);
444 /* Returns the alignment in bytes that is required so that no bounce buffer
445 * is required throughout the stack */
446 size_t bdrv_min_mem_align(BlockDriverState *bs);
447 /* Returns optimal alignment in bytes for bounce buffer */
448 size_t bdrv_opt_mem_align(BlockDriverState *bs);
449 void *qemu_blockalign(BlockDriverState *bs, size_t size);
450 void *qemu_blockalign0(BlockDriverState *bs, size_t size);
451 void *qemu_try_blockalign(BlockDriverState *bs, size_t size);
452 void *qemu_try_blockalign0(BlockDriverState *bs, size_t size);
453 bool bdrv_qiov_is_aligned(BlockDriverState *bs, QEMUIOVector *qiov);
455 void bdrv_enable_copy_on_read(BlockDriverState *bs);
456 void bdrv_disable_copy_on_read(BlockDriverState *bs);
458 void bdrv_ref(BlockDriverState *bs);
459 void bdrv_unref(BlockDriverState *bs);
460 void bdrv_unref_child(BlockDriverState *parent, BdrvChild *child);
461 BdrvChild *bdrv_attach_child(BlockDriverState *parent_bs,
462 BlockDriverState *child_bs,
463 const char *child_name,
464 const BdrvChildRole *child_role);
466 bool bdrv_op_is_blocked(BlockDriverState *bs, BlockOpType op, Error **errp);
467 void bdrv_op_block(BlockDriverState *bs, BlockOpType op, Error *reason);
468 void bdrv_op_unblock(BlockDriverState *bs, BlockOpType op, Error *reason);
469 void bdrv_op_block_all(BlockDriverState *bs, Error *reason);
470 void bdrv_op_unblock_all(BlockDriverState *bs, Error *reason);
471 bool bdrv_op_blocker_is_empty(BlockDriverState *bs);
473 #define BLKDBG_EVENT(child, evt) \
476 bdrv_debug_event(child->bs, evt); \
480 void bdrv_debug_event(BlockDriverState *bs, BlkdebugEvent event);
482 int bdrv_debug_breakpoint(BlockDriverState *bs, const char *event,
484 int bdrv_debug_remove_breakpoint(BlockDriverState *bs, const char *tag);
485 int bdrv_debug_resume(BlockDriverState *bs, const char *tag);
486 bool bdrv_debug_is_suspended(BlockDriverState *bs, const char *tag);
489 * bdrv_get_aio_context:
491 * Returns: the currently bound #AioContext
493 AioContext *bdrv_get_aio_context(BlockDriverState *bs);
496 * bdrv_set_aio_context:
498 * Changes the #AioContext used for fd handlers, timers, and BHs by this
499 * BlockDriverState and all its children.
501 * This function must be called with iothread lock held.
503 void bdrv_set_aio_context(BlockDriverState *bs, AioContext *new_context);
504 int bdrv_probe_blocksizes(BlockDriverState *bs, BlockSizes *bsz);
505 int bdrv_probe_geometry(BlockDriverState *bs, HDGeometry *geo);
507 void bdrv_io_plug(BlockDriverState *bs);
508 void bdrv_io_unplug(BlockDriverState *bs);
509 void bdrv_io_unplugged_begin(BlockDriverState *bs);
510 void bdrv_io_unplugged_end(BlockDriverState *bs);
513 * bdrv_drained_begin:
515 * Begin a quiesced section for exclusive access to the BDS, by disabling
516 * external request sources including NBD server and device model. Note that
517 * this doesn't block timers or coroutines from submitting more requests, which
518 * means block_job_pause is still necessary.
520 * This function can be recursive.
522 void bdrv_drained_begin(BlockDriverState *bs);
527 * End a quiescent section started by bdrv_drained_begin().
529 void bdrv_drained_end(BlockDriverState *bs);
531 void bdrv_add_child(BlockDriverState *parent, BlockDriverState *child,
533 void bdrv_del_child(BlockDriverState *parent, BdrvChild *child, Error **errp);