mirror: fix early wake from sleep due to aio
[qemu.git] / block / mirror.c
1 /*
2 * Image mirroring
3 *
4 * Copyright Red Hat, Inc. 2012
5 *
6 * Authors:
7 * Paolo Bonzini <pbonzini@redhat.com>
8 *
9 * This work is licensed under the terms of the GNU LGPL, version 2 or later.
10 * See the COPYING.LIB file in the top-level directory.
11 *
12 */
13
14 #include "trace.h"
15 #include "block/blockjob.h"
16 #include "block/block_int.h"
17 #include "qemu/ratelimit.h"
18 #include "qemu/bitmap.h"
19
20 #define SLICE_TIME 100000000ULL /* ns */
21 #define MAX_IN_FLIGHT 16
22
23 /* The mirroring buffer is a list of granularity-sized chunks.
24 * Free chunks are organized in a list.
25 */
26 typedef struct MirrorBuffer {
27 QSIMPLEQ_ENTRY(MirrorBuffer) next;
28 } MirrorBuffer;
29
30 typedef struct MirrorBlockJob {
31 BlockJob common;
32 RateLimit limit;
33 BlockDriverState *target;
34 BlockDriverState *base;
35 bool is_none_mode;
36 BlockdevOnError on_source_error, on_target_error;
37 bool synced;
38 bool should_complete;
39 int64_t sector_num;
40 int64_t granularity;
41 size_t buf_size;
42 unsigned long *cow_bitmap;
43 BdrvDirtyBitmap *dirty_bitmap;
44 HBitmapIter hbi;
45 uint8_t *buf;
46 QSIMPLEQ_HEAD(, MirrorBuffer) buf_free;
47 int buf_free_count;
48
49 unsigned long *in_flight_bitmap;
50 int in_flight;
51 int ret;
52 } MirrorBlockJob;
53
54 typedef struct MirrorOp {
55 MirrorBlockJob *s;
56 QEMUIOVector qiov;
57 int64_t sector_num;
58 int nb_sectors;
59 } MirrorOp;
60
61 static BlockErrorAction mirror_error_action(MirrorBlockJob *s, bool read,
62 int error)
63 {
64 s->synced = false;
65 if (read) {
66 return block_job_error_action(&s->common, s->common.bs,
67 s->on_source_error, true, error);
68 } else {
69 return block_job_error_action(&s->common, s->target,
70 s->on_target_error, false, error);
71 }
72 }
73
74 static void mirror_iteration_done(MirrorOp *op, int ret)
75 {
76 MirrorBlockJob *s = op->s;
77 struct iovec *iov;
78 int64_t chunk_num;
79 int i, nb_chunks, sectors_per_chunk;
80
81 trace_mirror_iteration_done(s, op->sector_num, op->nb_sectors, ret);
82
83 s->in_flight--;
84 iov = op->qiov.iov;
85 for (i = 0; i < op->qiov.niov; i++) {
86 MirrorBuffer *buf = (MirrorBuffer *) iov[i].iov_base;
87 QSIMPLEQ_INSERT_TAIL(&s->buf_free, buf, next);
88 s->buf_free_count++;
89 }
90
91 sectors_per_chunk = s->granularity >> BDRV_SECTOR_BITS;
92 chunk_num = op->sector_num / sectors_per_chunk;
93 nb_chunks = op->nb_sectors / sectors_per_chunk;
94 bitmap_clear(s->in_flight_bitmap, chunk_num, nb_chunks);
95 if (s->cow_bitmap && ret >= 0) {
96 bitmap_set(s->cow_bitmap, chunk_num, nb_chunks);
97 }
98
99 qemu_iovec_destroy(&op->qiov);
100 g_slice_free(MirrorOp, op);
101
102 /* Enter coroutine when it is not sleeping. The coroutine sleeps to
103 * rate-limit itself. The coroutine will eventually resume since there is
104 * a sleep timeout so don't wake it early.
105 */
106 if (s->common.busy) {
107 qemu_coroutine_enter(s->common.co, NULL);
108 }
109 }
110
111 static void mirror_write_complete(void *opaque, int ret)
112 {
113 MirrorOp *op = opaque;
114 MirrorBlockJob *s = op->s;
115 if (ret < 0) {
116 BlockDriverState *source = s->common.bs;
117 BlockErrorAction action;
118
119 bdrv_set_dirty(source, op->sector_num, op->nb_sectors);
120 action = mirror_error_action(s, false, -ret);
121 if (action == BDRV_ACTION_REPORT && s->ret >= 0) {
122 s->ret = ret;
123 }
124 }
125 mirror_iteration_done(op, ret);
126 }
127
128 static void mirror_read_complete(void *opaque, int ret)
129 {
130 MirrorOp *op = opaque;
131 MirrorBlockJob *s = op->s;
132 if (ret < 0) {
133 BlockDriverState *source = s->common.bs;
134 BlockErrorAction action;
135
136 bdrv_set_dirty(source, op->sector_num, op->nb_sectors);
137 action = mirror_error_action(s, true, -ret);
138 if (action == BDRV_ACTION_REPORT && s->ret >= 0) {
139 s->ret = ret;
140 }
141
142 mirror_iteration_done(op, ret);
143 return;
144 }
145 bdrv_aio_writev(s->target, op->sector_num, &op->qiov, op->nb_sectors,
146 mirror_write_complete, op);
147 }
148
149 static uint64_t coroutine_fn mirror_iteration(MirrorBlockJob *s)
150 {
151 BlockDriverState *source = s->common.bs;
152 int nb_sectors, sectors_per_chunk, nb_chunks;
153 int64_t end, sector_num, next_chunk, next_sector, hbitmap_next_sector;
154 uint64_t delay_ns;
155 MirrorOp *op;
156
157 s->sector_num = hbitmap_iter_next(&s->hbi);
158 if (s->sector_num < 0) {
159 bdrv_dirty_iter_init(source, s->dirty_bitmap, &s->hbi);
160 s->sector_num = hbitmap_iter_next(&s->hbi);
161 trace_mirror_restart_iter(s,
162 bdrv_get_dirty_count(source, s->dirty_bitmap));
163 assert(s->sector_num >= 0);
164 }
165
166 hbitmap_next_sector = s->sector_num;
167 sector_num = s->sector_num;
168 sectors_per_chunk = s->granularity >> BDRV_SECTOR_BITS;
169 end = s->common.len >> BDRV_SECTOR_BITS;
170
171 /* Extend the QEMUIOVector to include all adjacent blocks that will
172 * be copied in this operation.
173 *
174 * We have to do this if we have no backing file yet in the destination,
175 * and the cluster size is very large. Then we need to do COW ourselves.
176 * The first time a cluster is copied, copy it entirely. Note that,
177 * because both the granularity and the cluster size are powers of two,
178 * the number of sectors to copy cannot exceed one cluster.
179 *
180 * We also want to extend the QEMUIOVector to include more adjacent
181 * dirty blocks if possible, to limit the number of I/O operations and
182 * run efficiently even with a small granularity.
183 */
184 nb_chunks = 0;
185 nb_sectors = 0;
186 next_sector = sector_num;
187 next_chunk = sector_num / sectors_per_chunk;
188
189 /* Wait for I/O to this cluster (from a previous iteration) to be done. */
190 while (test_bit(next_chunk, s->in_flight_bitmap)) {
191 trace_mirror_yield_in_flight(s, sector_num, s->in_flight);
192 qemu_coroutine_yield();
193 }
194
195 do {
196 int added_sectors, added_chunks;
197
198 if (!bdrv_get_dirty(source, s->dirty_bitmap, next_sector) ||
199 test_bit(next_chunk, s->in_flight_bitmap)) {
200 assert(nb_sectors > 0);
201 break;
202 }
203
204 added_sectors = sectors_per_chunk;
205 if (s->cow_bitmap && !test_bit(next_chunk, s->cow_bitmap)) {
206 bdrv_round_to_clusters(s->target,
207 next_sector, added_sectors,
208 &next_sector, &added_sectors);
209
210 /* On the first iteration, the rounding may make us copy
211 * sectors before the first dirty one.
212 */
213 if (next_sector < sector_num) {
214 assert(nb_sectors == 0);
215 sector_num = next_sector;
216 next_chunk = next_sector / sectors_per_chunk;
217 }
218 }
219
220 added_sectors = MIN(added_sectors, end - (sector_num + nb_sectors));
221 added_chunks = (added_sectors + sectors_per_chunk - 1) / sectors_per_chunk;
222
223 /* When doing COW, it may happen that there is not enough space for
224 * a full cluster. Wait if that is the case.
225 */
226 while (nb_chunks == 0 && s->buf_free_count < added_chunks) {
227 trace_mirror_yield_buf_busy(s, nb_chunks, s->in_flight);
228 qemu_coroutine_yield();
229 }
230 if (s->buf_free_count < nb_chunks + added_chunks) {
231 trace_mirror_break_buf_busy(s, nb_chunks, s->in_flight);
232 break;
233 }
234
235 /* We have enough free space to copy these sectors. */
236 bitmap_set(s->in_flight_bitmap, next_chunk, added_chunks);
237
238 nb_sectors += added_sectors;
239 nb_chunks += added_chunks;
240 next_sector += added_sectors;
241 next_chunk += added_chunks;
242 if (!s->synced && s->common.speed) {
243 delay_ns = ratelimit_calculate_delay(&s->limit, added_sectors);
244 } else {
245 delay_ns = 0;
246 }
247 } while (delay_ns == 0 && next_sector < end);
248
249 /* Allocate a MirrorOp that is used as an AIO callback. */
250 op = g_slice_new(MirrorOp);
251 op->s = s;
252 op->sector_num = sector_num;
253 op->nb_sectors = nb_sectors;
254
255 /* Now make a QEMUIOVector taking enough granularity-sized chunks
256 * from s->buf_free.
257 */
258 qemu_iovec_init(&op->qiov, nb_chunks);
259 next_sector = sector_num;
260 while (nb_chunks-- > 0) {
261 MirrorBuffer *buf = QSIMPLEQ_FIRST(&s->buf_free);
262 QSIMPLEQ_REMOVE_HEAD(&s->buf_free, next);
263 s->buf_free_count--;
264 qemu_iovec_add(&op->qiov, buf, s->granularity);
265
266 /* Advance the HBitmapIter in parallel, so that we do not examine
267 * the same sector twice.
268 */
269 if (next_sector > hbitmap_next_sector
270 && bdrv_get_dirty(source, s->dirty_bitmap, next_sector)) {
271 hbitmap_next_sector = hbitmap_iter_next(&s->hbi);
272 }
273
274 next_sector += sectors_per_chunk;
275 }
276
277 bdrv_reset_dirty(source, sector_num, nb_sectors);
278
279 /* Copy the dirty cluster. */
280 s->in_flight++;
281 trace_mirror_one_iteration(s, sector_num, nb_sectors);
282 bdrv_aio_readv(source, sector_num, &op->qiov, nb_sectors,
283 mirror_read_complete, op);
284 return delay_ns;
285 }
286
287 static void mirror_free_init(MirrorBlockJob *s)
288 {
289 int granularity = s->granularity;
290 size_t buf_size = s->buf_size;
291 uint8_t *buf = s->buf;
292
293 assert(s->buf_free_count == 0);
294 QSIMPLEQ_INIT(&s->buf_free);
295 while (buf_size != 0) {
296 MirrorBuffer *cur = (MirrorBuffer *)buf;
297 QSIMPLEQ_INSERT_TAIL(&s->buf_free, cur, next);
298 s->buf_free_count++;
299 buf_size -= granularity;
300 buf += granularity;
301 }
302 }
303
304 static void mirror_drain(MirrorBlockJob *s)
305 {
306 while (s->in_flight > 0) {
307 qemu_coroutine_yield();
308 }
309 }
310
311 static void coroutine_fn mirror_run(void *opaque)
312 {
313 MirrorBlockJob *s = opaque;
314 BlockDriverState *bs = s->common.bs;
315 int64_t sector_num, end, sectors_per_chunk, length;
316 uint64_t last_pause_ns;
317 BlockDriverInfo bdi;
318 char backing_filename[1024];
319 int ret = 0;
320 int n;
321
322 if (block_job_is_cancelled(&s->common)) {
323 goto immediate_exit;
324 }
325
326 s->common.len = bdrv_getlength(bs);
327 if (s->common.len <= 0) {
328 block_job_completed(&s->common, s->common.len);
329 return;
330 }
331
332 length = (bdrv_getlength(bs) + s->granularity - 1) / s->granularity;
333 s->in_flight_bitmap = bitmap_new(length);
334
335 /* If we have no backing file yet in the destination, we cannot let
336 * the destination do COW. Instead, we copy sectors around the
337 * dirty data if needed. We need a bitmap to do that.
338 */
339 bdrv_get_backing_filename(s->target, backing_filename,
340 sizeof(backing_filename));
341 if (backing_filename[0] && !s->target->backing_hd) {
342 bdrv_get_info(s->target, &bdi);
343 if (s->granularity < bdi.cluster_size) {
344 s->buf_size = MAX(s->buf_size, bdi.cluster_size);
345 s->cow_bitmap = bitmap_new(length);
346 }
347 }
348
349 end = s->common.len >> BDRV_SECTOR_BITS;
350 s->buf = qemu_blockalign(bs, s->buf_size);
351 sectors_per_chunk = s->granularity >> BDRV_SECTOR_BITS;
352 mirror_free_init(s);
353
354 if (!s->is_none_mode) {
355 /* First part, loop on the sectors and initialize the dirty bitmap. */
356 BlockDriverState *base = s->base;
357 for (sector_num = 0; sector_num < end; ) {
358 int64_t next = (sector_num | (sectors_per_chunk - 1)) + 1;
359 ret = bdrv_is_allocated_above(bs, base,
360 sector_num, next - sector_num, &n);
361
362 if (ret < 0) {
363 goto immediate_exit;
364 }
365
366 assert(n > 0);
367 if (ret == 1) {
368 bdrv_set_dirty(bs, sector_num, n);
369 sector_num = next;
370 } else {
371 sector_num += n;
372 }
373 }
374 }
375
376 bdrv_dirty_iter_init(bs, s->dirty_bitmap, &s->hbi);
377 last_pause_ns = qemu_clock_get_ns(QEMU_CLOCK_REALTIME);
378 for (;;) {
379 uint64_t delay_ns = 0;
380 int64_t cnt;
381 bool should_complete;
382
383 if (s->ret < 0) {
384 ret = s->ret;
385 goto immediate_exit;
386 }
387
388 cnt = bdrv_get_dirty_count(bs, s->dirty_bitmap);
389
390 /* Note that even when no rate limit is applied we need to yield
391 * periodically with no pending I/O so that qemu_aio_flush() returns.
392 * We do so every SLICE_TIME nanoseconds, or when there is an error,
393 * or when the source is clean, whichever comes first.
394 */
395 if (qemu_clock_get_ns(QEMU_CLOCK_REALTIME) - last_pause_ns < SLICE_TIME &&
396 s->common.iostatus == BLOCK_DEVICE_IO_STATUS_OK) {
397 if (s->in_flight == MAX_IN_FLIGHT || s->buf_free_count == 0 ||
398 (cnt == 0 && s->in_flight > 0)) {
399 trace_mirror_yield(s, s->in_flight, s->buf_free_count, cnt);
400 qemu_coroutine_yield();
401 continue;
402 } else if (cnt != 0) {
403 delay_ns = mirror_iteration(s);
404 if (delay_ns == 0) {
405 continue;
406 }
407 }
408 }
409
410 should_complete = false;
411 if (s->in_flight == 0 && cnt == 0) {
412 trace_mirror_before_flush(s);
413 ret = bdrv_flush(s->target);
414 if (ret < 0) {
415 if (mirror_error_action(s, false, -ret) == BDRV_ACTION_REPORT) {
416 goto immediate_exit;
417 }
418 } else {
419 /* We're out of the streaming phase. From now on, if the job
420 * is cancelled we will actually complete all pending I/O and
421 * report completion. This way, block-job-cancel will leave
422 * the target in a consistent state.
423 */
424 s->common.offset = end * BDRV_SECTOR_SIZE;
425 if (!s->synced) {
426 block_job_ready(&s->common);
427 s->synced = true;
428 }
429
430 should_complete = s->should_complete ||
431 block_job_is_cancelled(&s->common);
432 cnt = bdrv_get_dirty_count(bs, s->dirty_bitmap);
433 }
434 }
435
436 if (cnt == 0 && should_complete) {
437 /* The dirty bitmap is not updated while operations are pending.
438 * If we're about to exit, wait for pending operations before
439 * calling bdrv_get_dirty_count(bs), or we may exit while the
440 * source has dirty data to copy!
441 *
442 * Note that I/O can be submitted by the guest while
443 * mirror_populate runs.
444 */
445 trace_mirror_before_drain(s, cnt);
446 bdrv_drain_all();
447 cnt = bdrv_get_dirty_count(bs, s->dirty_bitmap);
448 }
449
450 ret = 0;
451 trace_mirror_before_sleep(s, cnt, s->synced, delay_ns);
452 if (!s->synced) {
453 /* Publish progress */
454 s->common.offset = (end - cnt) * BDRV_SECTOR_SIZE;
455 block_job_sleep_ns(&s->common, QEMU_CLOCK_REALTIME, delay_ns);
456 if (block_job_is_cancelled(&s->common)) {
457 break;
458 }
459 } else if (!should_complete) {
460 delay_ns = (s->in_flight == 0 && cnt == 0 ? SLICE_TIME : 0);
461 block_job_sleep_ns(&s->common, QEMU_CLOCK_REALTIME, delay_ns);
462 } else if (cnt == 0) {
463 /* The two disks are in sync. Exit and report successful
464 * completion.
465 */
466 assert(QLIST_EMPTY(&bs->tracked_requests));
467 s->common.cancelled = false;
468 break;
469 }
470 last_pause_ns = qemu_clock_get_ns(QEMU_CLOCK_REALTIME);
471 }
472
473 immediate_exit:
474 if (s->in_flight > 0) {
475 /* We get here only if something went wrong. Either the job failed,
476 * or it was cancelled prematurely so that we do not guarantee that
477 * the target is a copy of the source.
478 */
479 assert(ret < 0 || (!s->synced && block_job_is_cancelled(&s->common)));
480 mirror_drain(s);
481 }
482
483 assert(s->in_flight == 0);
484 qemu_vfree(s->buf);
485 g_free(s->cow_bitmap);
486 g_free(s->in_flight_bitmap);
487 bdrv_release_dirty_bitmap(bs, s->dirty_bitmap);
488 bdrv_iostatus_disable(s->target);
489 if (s->should_complete && ret == 0) {
490 if (bdrv_get_flags(s->target) != bdrv_get_flags(s->common.bs)) {
491 bdrv_reopen(s->target, bdrv_get_flags(s->common.bs), NULL);
492 }
493 bdrv_swap(s->target, s->common.bs);
494 if (s->common.driver->job_type == BLOCK_JOB_TYPE_COMMIT) {
495 /* drop the bs loop chain formed by the swap: break the loop then
496 * trigger the unref from the top one */
497 BlockDriverState *p = s->base->backing_hd;
498 s->base->backing_hd = NULL;
499 bdrv_unref(p);
500 }
501 }
502 bdrv_unref(s->target);
503 block_job_completed(&s->common, ret);
504 }
505
506 static void mirror_set_speed(BlockJob *job, int64_t speed, Error **errp)
507 {
508 MirrorBlockJob *s = container_of(job, MirrorBlockJob, common);
509
510 if (speed < 0) {
511 error_set(errp, QERR_INVALID_PARAMETER, "speed");
512 return;
513 }
514 ratelimit_set_speed(&s->limit, speed / BDRV_SECTOR_SIZE, SLICE_TIME);
515 }
516
517 static void mirror_iostatus_reset(BlockJob *job)
518 {
519 MirrorBlockJob *s = container_of(job, MirrorBlockJob, common);
520
521 bdrv_iostatus_reset(s->target);
522 }
523
524 static void mirror_complete(BlockJob *job, Error **errp)
525 {
526 MirrorBlockJob *s = container_of(job, MirrorBlockJob, common);
527 Error *local_err = NULL;
528 int ret;
529
530 ret = bdrv_open_backing_file(s->target, NULL, &local_err);
531 if (ret < 0) {
532 error_propagate(errp, local_err);
533 return;
534 }
535 if (!s->synced) {
536 error_set(errp, QERR_BLOCK_JOB_NOT_READY, job->bs->device_name);
537 return;
538 }
539
540 s->should_complete = true;
541 block_job_resume(job);
542 }
543
544 static const BlockJobDriver mirror_job_driver = {
545 .instance_size = sizeof(MirrorBlockJob),
546 .job_type = BLOCK_JOB_TYPE_MIRROR,
547 .set_speed = mirror_set_speed,
548 .iostatus_reset= mirror_iostatus_reset,
549 .complete = mirror_complete,
550 };
551
552 static const BlockJobDriver commit_active_job_driver = {
553 .instance_size = sizeof(MirrorBlockJob),
554 .job_type = BLOCK_JOB_TYPE_COMMIT,
555 .set_speed = mirror_set_speed,
556 .iostatus_reset
557 = mirror_iostatus_reset,
558 .complete = mirror_complete,
559 };
560
561 static void mirror_start_job(BlockDriverState *bs, BlockDriverState *target,
562 int64_t speed, int64_t granularity,
563 int64_t buf_size,
564 BlockdevOnError on_source_error,
565 BlockdevOnError on_target_error,
566 BlockDriverCompletionFunc *cb,
567 void *opaque, Error **errp,
568 const BlockJobDriver *driver,
569 bool is_none_mode, BlockDriverState *base)
570 {
571 MirrorBlockJob *s;
572
573 if (granularity == 0) {
574 /* Choose the default granularity based on the target file's cluster
575 * size, clamped between 4k and 64k. */
576 BlockDriverInfo bdi;
577 if (bdrv_get_info(target, &bdi) >= 0 && bdi.cluster_size != 0) {
578 granularity = MAX(4096, bdi.cluster_size);
579 granularity = MIN(65536, granularity);
580 } else {
581 granularity = 65536;
582 }
583 }
584
585 assert ((granularity & (granularity - 1)) == 0);
586
587 if ((on_source_error == BLOCKDEV_ON_ERROR_STOP ||
588 on_source_error == BLOCKDEV_ON_ERROR_ENOSPC) &&
589 !bdrv_iostatus_is_enabled(bs)) {
590 error_set(errp, QERR_INVALID_PARAMETER, "on-source-error");
591 return;
592 }
593
594
595 s = block_job_create(driver, bs, speed, cb, opaque, errp);
596 if (!s) {
597 return;
598 }
599
600 s->on_source_error = on_source_error;
601 s->on_target_error = on_target_error;
602 s->target = target;
603 s->is_none_mode = is_none_mode;
604 s->base = base;
605 s->granularity = granularity;
606 s->buf_size = MAX(buf_size, granularity);
607
608 s->dirty_bitmap = bdrv_create_dirty_bitmap(bs, granularity);
609 bdrv_set_enable_write_cache(s->target, true);
610 bdrv_set_on_error(s->target, on_target_error, on_target_error);
611 bdrv_iostatus_enable(s->target);
612 s->common.co = qemu_coroutine_create(mirror_run);
613 trace_mirror_start(bs, s, s->common.co, opaque);
614 qemu_coroutine_enter(s->common.co, s);
615 }
616
617 void mirror_start(BlockDriverState *bs, BlockDriverState *target,
618 int64_t speed, int64_t granularity, int64_t buf_size,
619 MirrorSyncMode mode, BlockdevOnError on_source_error,
620 BlockdevOnError on_target_error,
621 BlockDriverCompletionFunc *cb,
622 void *opaque, Error **errp)
623 {
624 bool is_none_mode;
625 BlockDriverState *base;
626
627 is_none_mode = mode == MIRROR_SYNC_MODE_NONE;
628 base = mode == MIRROR_SYNC_MODE_TOP ? bs->backing_hd : NULL;
629 mirror_start_job(bs, target, speed, granularity, buf_size,
630 on_source_error, on_target_error, cb, opaque, errp,
631 &mirror_job_driver, is_none_mode, base);
632 }
633
634 void commit_active_start(BlockDriverState *bs, BlockDriverState *base,
635 int64_t speed,
636 BlockdevOnError on_error,
637 BlockDriverCompletionFunc *cb,
638 void *opaque, Error **errp)
639 {
640 int64_t length, base_length;
641 int orig_base_flags;
642 int ret;
643 Error *local_err = NULL;
644
645 orig_base_flags = bdrv_get_flags(base);
646
647 if (bdrv_reopen(base, bs->open_flags, errp)) {
648 return;
649 }
650
651 length = bdrv_getlength(bs);
652 if (length < 0) {
653 error_setg_errno(errp, -length,
654 "Unable to determine length of %s", bs->filename);
655 goto error_restore_flags;
656 }
657
658 base_length = bdrv_getlength(base);
659 if (base_length < 0) {
660 error_setg_errno(errp, -base_length,
661 "Unable to determine length of %s", base->filename);
662 goto error_restore_flags;
663 }
664
665 if (length > base_length) {
666 ret = bdrv_truncate(base, length);
667 if (ret < 0) {
668 error_setg_errno(errp, -ret,
669 "Top image %s is larger than base image %s, and "
670 "resize of base image failed",
671 bs->filename, base->filename);
672 goto error_restore_flags;
673 }
674 }
675
676 bdrv_ref(base);
677 mirror_start_job(bs, base, speed, 0, 0,
678 on_error, on_error, cb, opaque, &local_err,
679 &commit_active_job_driver, false, base);
680 if (error_is_set(&local_err)) {
681 error_propagate(errp, local_err);
682 goto error_restore_flags;
683 }
684
685 return;
686
687 error_restore_flags:
688 /* ignore error and errp for bdrv_reopen, because we want to propagate
689 * the original error */
690 bdrv_reopen(base, orig_base_flags, NULL);
691 return;
692 }