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1 /*
2 * Block driver for the QCOW version 2 format
3 *
4 * Copyright (c) 2004-2006 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
25 #include "qemu-common.h"
26 #include "block/block_int.h"
27 #include "block/qcow2.h"
28
29 void qcow2_free_snapshots(BlockDriverState *bs)
30 {
31 BDRVQcowState *s = bs->opaque;
32 int i;
33
34 for(i = 0; i < s->nb_snapshots; i++) {
35 g_free(s->snapshots[i].name);
36 g_free(s->snapshots[i].id_str);
37 }
38 g_free(s->snapshots);
39 s->snapshots = NULL;
40 s->nb_snapshots = 0;
41 }
42
43 int qcow2_read_snapshots(BlockDriverState *bs)
44 {
45 BDRVQcowState *s = bs->opaque;
46 QCowSnapshotHeader h;
47 QCowSnapshotExtraData extra;
48 QCowSnapshot *sn;
49 int i, id_str_size, name_size;
50 int64_t offset;
51 uint32_t extra_data_size;
52 int ret;
53
54 if (!s->nb_snapshots) {
55 s->snapshots = NULL;
56 s->snapshots_size = 0;
57 return 0;
58 }
59
60 offset = s->snapshots_offset;
61 s->snapshots = g_malloc0(s->nb_snapshots * sizeof(QCowSnapshot));
62
63 for(i = 0; i < s->nb_snapshots; i++) {
64 /* Read statically sized part of the snapshot header */
65 offset = align_offset(offset, 8);
66 ret = bdrv_pread(bs->file, offset, &h, sizeof(h));
67 if (ret < 0) {
68 goto fail;
69 }
70
71 offset += sizeof(h);
72 sn = s->snapshots + i;
73 sn->l1_table_offset = be64_to_cpu(h.l1_table_offset);
74 sn->l1_size = be32_to_cpu(h.l1_size);
75 sn->vm_state_size = be32_to_cpu(h.vm_state_size);
76 sn->date_sec = be32_to_cpu(h.date_sec);
77 sn->date_nsec = be32_to_cpu(h.date_nsec);
78 sn->vm_clock_nsec = be64_to_cpu(h.vm_clock_nsec);
79 extra_data_size = be32_to_cpu(h.extra_data_size);
80
81 id_str_size = be16_to_cpu(h.id_str_size);
82 name_size = be16_to_cpu(h.name_size);
83
84 /* Read extra data */
85 ret = bdrv_pread(bs->file, offset, &extra,
86 MIN(sizeof(extra), extra_data_size));
87 if (ret < 0) {
88 goto fail;
89 }
90 offset += extra_data_size;
91
92 if (extra_data_size >= 8) {
93 sn->vm_state_size = be64_to_cpu(extra.vm_state_size_large);
94 }
95
96 if (extra_data_size >= 16) {
97 sn->disk_size = be64_to_cpu(extra.disk_size);
98 } else {
99 sn->disk_size = bs->total_sectors * BDRV_SECTOR_SIZE;
100 }
101
102 /* Read snapshot ID */
103 sn->id_str = g_malloc(id_str_size + 1);
104 ret = bdrv_pread(bs->file, offset, sn->id_str, id_str_size);
105 if (ret < 0) {
106 goto fail;
107 }
108 offset += id_str_size;
109 sn->id_str[id_str_size] = '\0';
110
111 /* Read snapshot name */
112 sn->name = g_malloc(name_size + 1);
113 ret = bdrv_pread(bs->file, offset, sn->name, name_size);
114 if (ret < 0) {
115 goto fail;
116 }
117 offset += name_size;
118 sn->name[name_size] = '\0';
119
120 if (offset - s->snapshots_offset > QCOW_MAX_SNAPSHOTS_SIZE) {
121 ret = -EFBIG;
122 goto fail;
123 }
124 }
125
126 assert(offset - s->snapshots_offset <= INT_MAX);
127 s->snapshots_size = offset - s->snapshots_offset;
128 return 0;
129
130 fail:
131 qcow2_free_snapshots(bs);
132 return ret;
133 }
134
135 /* add at the end of the file a new list of snapshots */
136 static int qcow2_write_snapshots(BlockDriverState *bs)
137 {
138 BDRVQcowState *s = bs->opaque;
139 QCowSnapshot *sn;
140 QCowSnapshotHeader h;
141 QCowSnapshotExtraData extra;
142 int i, name_size, id_str_size, snapshots_size;
143 struct {
144 uint32_t nb_snapshots;
145 uint64_t snapshots_offset;
146 } QEMU_PACKED header_data;
147 int64_t offset, snapshots_offset = 0;
148 int ret;
149
150 /* compute the size of the snapshots */
151 offset = 0;
152 for(i = 0; i < s->nb_snapshots; i++) {
153 sn = s->snapshots + i;
154 offset = align_offset(offset, 8);
155 offset += sizeof(h);
156 offset += sizeof(extra);
157 offset += strlen(sn->id_str);
158 offset += strlen(sn->name);
159
160 if (offset > QCOW_MAX_SNAPSHOTS_SIZE) {
161 ret = -EFBIG;
162 goto fail;
163 }
164 }
165
166 assert(offset <= INT_MAX);
167 snapshots_size = offset;
168
169 /* Allocate space for the new snapshot list */
170 snapshots_offset = qcow2_alloc_clusters(bs, snapshots_size);
171 offset = snapshots_offset;
172 if (offset < 0) {
173 ret = offset;
174 goto fail;
175 }
176 ret = bdrv_flush(bs);
177 if (ret < 0) {
178 goto fail;
179 }
180
181 /* The snapshot list position has not yet been updated, so these clusters
182 * must indeed be completely free */
183 ret = qcow2_pre_write_overlap_check(bs, 0, offset, snapshots_size);
184 if (ret < 0) {
185 goto fail;
186 }
187
188
189 /* Write all snapshots to the new list */
190 for(i = 0; i < s->nb_snapshots; i++) {
191 sn = s->snapshots + i;
192 memset(&h, 0, sizeof(h));
193 h.l1_table_offset = cpu_to_be64(sn->l1_table_offset);
194 h.l1_size = cpu_to_be32(sn->l1_size);
195 /* If it doesn't fit in 32 bit, older implementations should treat it
196 * as a disk-only snapshot rather than truncate the VM state */
197 if (sn->vm_state_size <= 0xffffffff) {
198 h.vm_state_size = cpu_to_be32(sn->vm_state_size);
199 }
200 h.date_sec = cpu_to_be32(sn->date_sec);
201 h.date_nsec = cpu_to_be32(sn->date_nsec);
202 h.vm_clock_nsec = cpu_to_be64(sn->vm_clock_nsec);
203 h.extra_data_size = cpu_to_be32(sizeof(extra));
204
205 memset(&extra, 0, sizeof(extra));
206 extra.vm_state_size_large = cpu_to_be64(sn->vm_state_size);
207 extra.disk_size = cpu_to_be64(sn->disk_size);
208
209 id_str_size = strlen(sn->id_str);
210 name_size = strlen(sn->name);
211 assert(id_str_size <= UINT16_MAX && name_size <= UINT16_MAX);
212 h.id_str_size = cpu_to_be16(id_str_size);
213 h.name_size = cpu_to_be16(name_size);
214 offset = align_offset(offset, 8);
215
216 ret = bdrv_pwrite(bs->file, offset, &h, sizeof(h));
217 if (ret < 0) {
218 goto fail;
219 }
220 offset += sizeof(h);
221
222 ret = bdrv_pwrite(bs->file, offset, &extra, sizeof(extra));
223 if (ret < 0) {
224 goto fail;
225 }
226 offset += sizeof(extra);
227
228 ret = bdrv_pwrite(bs->file, offset, sn->id_str, id_str_size);
229 if (ret < 0) {
230 goto fail;
231 }
232 offset += id_str_size;
233
234 ret = bdrv_pwrite(bs->file, offset, sn->name, name_size);
235 if (ret < 0) {
236 goto fail;
237 }
238 offset += name_size;
239 }
240
241 /*
242 * Update the header to point to the new snapshot table. This requires the
243 * new table and its refcounts to be stable on disk.
244 */
245 ret = bdrv_flush(bs);
246 if (ret < 0) {
247 goto fail;
248 }
249
250 QEMU_BUILD_BUG_ON(offsetof(QCowHeader, snapshots_offset) !=
251 offsetof(QCowHeader, nb_snapshots) + sizeof(header_data.nb_snapshots));
252
253 header_data.nb_snapshots = cpu_to_be32(s->nb_snapshots);
254 header_data.snapshots_offset = cpu_to_be64(snapshots_offset);
255
256 ret = bdrv_pwrite_sync(bs->file, offsetof(QCowHeader, nb_snapshots),
257 &header_data, sizeof(header_data));
258 if (ret < 0) {
259 goto fail;
260 }
261
262 /* free the old snapshot table */
263 qcow2_free_clusters(bs, s->snapshots_offset, s->snapshots_size,
264 QCOW2_DISCARD_SNAPSHOT);
265 s->snapshots_offset = snapshots_offset;
266 s->snapshots_size = snapshots_size;
267 return 0;
268
269 fail:
270 if (snapshots_offset > 0) {
271 qcow2_free_clusters(bs, snapshots_offset, snapshots_size,
272 QCOW2_DISCARD_ALWAYS);
273 }
274 return ret;
275 }
276
277 static void find_new_snapshot_id(BlockDriverState *bs,
278 char *id_str, int id_str_size)
279 {
280 BDRVQcowState *s = bs->opaque;
281 QCowSnapshot *sn;
282 int i;
283 unsigned long id, id_max = 0;
284
285 for(i = 0; i < s->nb_snapshots; i++) {
286 sn = s->snapshots + i;
287 id = strtoul(sn->id_str, NULL, 10);
288 if (id > id_max)
289 id_max = id;
290 }
291 snprintf(id_str, id_str_size, "%lu", id_max + 1);
292 }
293
294 static int find_snapshot_by_id_and_name(BlockDriverState *bs,
295 const char *id,
296 const char *name)
297 {
298 BDRVQcowState *s = bs->opaque;
299 int i;
300
301 if (id && name) {
302 for (i = 0; i < s->nb_snapshots; i++) {
303 if (!strcmp(s->snapshots[i].id_str, id) &&
304 !strcmp(s->snapshots[i].name, name)) {
305 return i;
306 }
307 }
308 } else if (id) {
309 for (i = 0; i < s->nb_snapshots; i++) {
310 if (!strcmp(s->snapshots[i].id_str, id)) {
311 return i;
312 }
313 }
314 } else if (name) {
315 for (i = 0; i < s->nb_snapshots; i++) {
316 if (!strcmp(s->snapshots[i].name, name)) {
317 return i;
318 }
319 }
320 }
321
322 return -1;
323 }
324
325 static int find_snapshot_by_id_or_name(BlockDriverState *bs,
326 const char *id_or_name)
327 {
328 int ret;
329
330 ret = find_snapshot_by_id_and_name(bs, id_or_name, NULL);
331 if (ret >= 0) {
332 return ret;
333 }
334 return find_snapshot_by_id_and_name(bs, NULL, id_or_name);
335 }
336
337 /* if no id is provided, a new one is constructed */
338 int qcow2_snapshot_create(BlockDriverState *bs, QEMUSnapshotInfo *sn_info)
339 {
340 BDRVQcowState *s = bs->opaque;
341 QCowSnapshot *new_snapshot_list = NULL;
342 QCowSnapshot *old_snapshot_list = NULL;
343 QCowSnapshot sn1, *sn = &sn1;
344 int i, ret;
345 uint64_t *l1_table = NULL;
346 int64_t l1_table_offset;
347
348 if (s->nb_snapshots >= QCOW_MAX_SNAPSHOTS) {
349 return -EFBIG;
350 }
351
352 memset(sn, 0, sizeof(*sn));
353
354 /* Generate an ID if it wasn't passed */
355 if (sn_info->id_str[0] == '\0') {
356 find_new_snapshot_id(bs, sn_info->id_str, sizeof(sn_info->id_str));
357 }
358
359 /* Check that the ID is unique */
360 if (find_snapshot_by_id_and_name(bs, sn_info->id_str, NULL) >= 0) {
361 return -EEXIST;
362 }
363
364 /* Populate sn with passed data */
365 sn->id_str = g_strdup(sn_info->id_str);
366 sn->name = g_strdup(sn_info->name);
367
368 sn->disk_size = bs->total_sectors * BDRV_SECTOR_SIZE;
369 sn->vm_state_size = sn_info->vm_state_size;
370 sn->date_sec = sn_info->date_sec;
371 sn->date_nsec = sn_info->date_nsec;
372 sn->vm_clock_nsec = sn_info->vm_clock_nsec;
373
374 /* Allocate the L1 table of the snapshot and copy the current one there. */
375 l1_table_offset = qcow2_alloc_clusters(bs, s->l1_size * sizeof(uint64_t));
376 if (l1_table_offset < 0) {
377 ret = l1_table_offset;
378 goto fail;
379 }
380
381 sn->l1_table_offset = l1_table_offset;
382 sn->l1_size = s->l1_size;
383
384 l1_table = g_malloc(s->l1_size * sizeof(uint64_t));
385 for(i = 0; i < s->l1_size; i++) {
386 l1_table[i] = cpu_to_be64(s->l1_table[i]);
387 }
388
389 ret = qcow2_pre_write_overlap_check(bs, 0, sn->l1_table_offset,
390 s->l1_size * sizeof(uint64_t));
391 if (ret < 0) {
392 goto fail;
393 }
394
395 ret = bdrv_pwrite(bs->file, sn->l1_table_offset, l1_table,
396 s->l1_size * sizeof(uint64_t));
397 if (ret < 0) {
398 goto fail;
399 }
400
401 g_free(l1_table);
402 l1_table = NULL;
403
404 /*
405 * Increase the refcounts of all clusters and make sure everything is
406 * stable on disk before updating the snapshot table to contain a pointer
407 * to the new L1 table.
408 */
409 ret = qcow2_update_snapshot_refcount(bs, s->l1_table_offset, s->l1_size, 1);
410 if (ret < 0) {
411 goto fail;
412 }
413
414 /* Append the new snapshot to the snapshot list */
415 new_snapshot_list = g_malloc((s->nb_snapshots + 1) * sizeof(QCowSnapshot));
416 if (s->snapshots) {
417 memcpy(new_snapshot_list, s->snapshots,
418 s->nb_snapshots * sizeof(QCowSnapshot));
419 old_snapshot_list = s->snapshots;
420 }
421 s->snapshots = new_snapshot_list;
422 s->snapshots[s->nb_snapshots++] = *sn;
423
424 ret = qcow2_write_snapshots(bs);
425 if (ret < 0) {
426 g_free(s->snapshots);
427 s->snapshots = old_snapshot_list;
428 s->nb_snapshots--;
429 goto fail;
430 }
431
432 g_free(old_snapshot_list);
433
434 /* The VM state isn't needed any more in the active L1 table; in fact, it
435 * hurts by causing expensive COW for the next snapshot. */
436 qcow2_discard_clusters(bs, qcow2_vm_state_offset(s),
437 align_offset(sn->vm_state_size, s->cluster_size)
438 >> BDRV_SECTOR_BITS,
439 QCOW2_DISCARD_NEVER);
440
441 #ifdef DEBUG_ALLOC
442 {
443 BdrvCheckResult result = {0};
444 qcow2_check_refcounts(bs, &result, 0);
445 }
446 #endif
447 return 0;
448
449 fail:
450 g_free(sn->id_str);
451 g_free(sn->name);
452 g_free(l1_table);
453
454 return ret;
455 }
456
457 /* copy the snapshot 'snapshot_name' into the current disk image */
458 int qcow2_snapshot_goto(BlockDriverState *bs, const char *snapshot_id)
459 {
460 BDRVQcowState *s = bs->opaque;
461 QCowSnapshot *sn;
462 int i, snapshot_index;
463 int cur_l1_bytes, sn_l1_bytes;
464 int ret;
465 uint64_t *sn_l1_table = NULL;
466
467 /* Search the snapshot */
468 snapshot_index = find_snapshot_by_id_or_name(bs, snapshot_id);
469 if (snapshot_index < 0) {
470 return -ENOENT;
471 }
472 sn = &s->snapshots[snapshot_index];
473
474 if (sn->disk_size != bs->total_sectors * BDRV_SECTOR_SIZE) {
475 error_report("qcow2: Loading snapshots with different disk "
476 "size is not implemented");
477 ret = -ENOTSUP;
478 goto fail;
479 }
480
481 /*
482 * Make sure that the current L1 table is big enough to contain the whole
483 * L1 table of the snapshot. If the snapshot L1 table is smaller, the
484 * current one must be padded with zeros.
485 */
486 ret = qcow2_grow_l1_table(bs, sn->l1_size, true);
487 if (ret < 0) {
488 goto fail;
489 }
490
491 cur_l1_bytes = s->l1_size * sizeof(uint64_t);
492 sn_l1_bytes = sn->l1_size * sizeof(uint64_t);
493
494 /*
495 * Copy the snapshot L1 table to the current L1 table.
496 *
497 * Before overwriting the old current L1 table on disk, make sure to
498 * increase all refcounts for the clusters referenced by the new one.
499 * Decrease the refcount referenced by the old one only when the L1
500 * table is overwritten.
501 */
502 sn_l1_table = g_malloc0(cur_l1_bytes);
503
504 ret = bdrv_pread(bs->file, sn->l1_table_offset, sn_l1_table, sn_l1_bytes);
505 if (ret < 0) {
506 goto fail;
507 }
508
509 ret = qcow2_update_snapshot_refcount(bs, sn->l1_table_offset,
510 sn->l1_size, 1);
511 if (ret < 0) {
512 goto fail;
513 }
514
515 ret = qcow2_pre_write_overlap_check(bs, QCOW2_OL_ACTIVE_L1,
516 s->l1_table_offset, cur_l1_bytes);
517 if (ret < 0) {
518 goto fail;
519 }
520
521 ret = bdrv_pwrite_sync(bs->file, s->l1_table_offset, sn_l1_table,
522 cur_l1_bytes);
523 if (ret < 0) {
524 goto fail;
525 }
526
527 /*
528 * Decrease refcount of clusters of current L1 table.
529 *
530 * At this point, the in-memory s->l1_table points to the old L1 table,
531 * whereas on disk we already have the new one.
532 *
533 * qcow2_update_snapshot_refcount special cases the current L1 table to use
534 * the in-memory data instead of really using the offset to load a new one,
535 * which is why this works.
536 */
537 ret = qcow2_update_snapshot_refcount(bs, s->l1_table_offset,
538 s->l1_size, -1);
539
540 /*
541 * Now update the in-memory L1 table to be in sync with the on-disk one. We
542 * need to do this even if updating refcounts failed.
543 */
544 for(i = 0;i < s->l1_size; i++) {
545 s->l1_table[i] = be64_to_cpu(sn_l1_table[i]);
546 }
547
548 if (ret < 0) {
549 goto fail;
550 }
551
552 g_free(sn_l1_table);
553 sn_l1_table = NULL;
554
555 /*
556 * Update QCOW_OFLAG_COPIED in the active L1 table (it may have changed
557 * when we decreased the refcount of the old snapshot.
558 */
559 ret = qcow2_update_snapshot_refcount(bs, s->l1_table_offset, s->l1_size, 0);
560 if (ret < 0) {
561 goto fail;
562 }
563
564 #ifdef DEBUG_ALLOC
565 {
566 BdrvCheckResult result = {0};
567 qcow2_check_refcounts(bs, &result, 0);
568 }
569 #endif
570 return 0;
571
572 fail:
573 g_free(sn_l1_table);
574 return ret;
575 }
576
577 int qcow2_snapshot_delete(BlockDriverState *bs,
578 const char *snapshot_id,
579 const char *name,
580 Error **errp)
581 {
582 BDRVQcowState *s = bs->opaque;
583 QCowSnapshot sn;
584 int snapshot_index, ret;
585
586 /* Search the snapshot */
587 snapshot_index = find_snapshot_by_id_and_name(bs, snapshot_id, name);
588 if (snapshot_index < 0) {
589 error_setg(errp, "Can't find the snapshot");
590 return -ENOENT;
591 }
592 sn = s->snapshots[snapshot_index];
593
594 /* Remove it from the snapshot list */
595 memmove(s->snapshots + snapshot_index,
596 s->snapshots + snapshot_index + 1,
597 (s->nb_snapshots - snapshot_index - 1) * sizeof(sn));
598 s->nb_snapshots--;
599 ret = qcow2_write_snapshots(bs);
600 if (ret < 0) {
601 error_setg_errno(errp, -ret,
602 "Failed to remove snapshot from snapshot list");
603 return ret;
604 }
605
606 /*
607 * The snapshot is now unused, clean up. If we fail after this point, we
608 * won't recover but just leak clusters.
609 */
610 g_free(sn.id_str);
611 g_free(sn.name);
612
613 /*
614 * Now decrease the refcounts of clusters referenced by the snapshot and
615 * free the L1 table.
616 */
617 ret = qcow2_update_snapshot_refcount(bs, sn.l1_table_offset,
618 sn.l1_size, -1);
619 if (ret < 0) {
620 error_setg_errno(errp, -ret, "Failed to free the cluster and L1 table");
621 return ret;
622 }
623 qcow2_free_clusters(bs, sn.l1_table_offset, sn.l1_size * sizeof(uint64_t),
624 QCOW2_DISCARD_SNAPSHOT);
625
626 /* must update the copied flag on the current cluster offsets */
627 ret = qcow2_update_snapshot_refcount(bs, s->l1_table_offset, s->l1_size, 0);
628 if (ret < 0) {
629 error_setg_errno(errp, -ret,
630 "Failed to update snapshot status in disk");
631 return ret;
632 }
633
634 #ifdef DEBUG_ALLOC
635 {
636 BdrvCheckResult result = {0};
637 qcow2_check_refcounts(bs, &result, 0);
638 }
639 #endif
640 return 0;
641 }
642
643 int qcow2_snapshot_list(BlockDriverState *bs, QEMUSnapshotInfo **psn_tab)
644 {
645 BDRVQcowState *s = bs->opaque;
646 QEMUSnapshotInfo *sn_tab, *sn_info;
647 QCowSnapshot *sn;
648 int i;
649
650 if (!s->nb_snapshots) {
651 *psn_tab = NULL;
652 return s->nb_snapshots;
653 }
654
655 sn_tab = g_malloc0(s->nb_snapshots * sizeof(QEMUSnapshotInfo));
656 for(i = 0; i < s->nb_snapshots; i++) {
657 sn_info = sn_tab + i;
658 sn = s->snapshots + i;
659 pstrcpy(sn_info->id_str, sizeof(sn_info->id_str),
660 sn->id_str);
661 pstrcpy(sn_info->name, sizeof(sn_info->name),
662 sn->name);
663 sn_info->vm_state_size = sn->vm_state_size;
664 sn_info->date_sec = sn->date_sec;
665 sn_info->date_nsec = sn->date_nsec;
666 sn_info->vm_clock_nsec = sn->vm_clock_nsec;
667 }
668 *psn_tab = sn_tab;
669 return s->nb_snapshots;
670 }
671
672 int qcow2_snapshot_load_tmp(BlockDriverState *bs,
673 const char *snapshot_id,
674 const char *name,
675 Error **errp)
676 {
677 int i, snapshot_index;
678 BDRVQcowState *s = bs->opaque;
679 QCowSnapshot *sn;
680 uint64_t *new_l1_table;
681 int new_l1_bytes;
682 int ret;
683
684 assert(bs->read_only);
685
686 /* Search the snapshot */
687 snapshot_index = find_snapshot_by_id_and_name(bs, snapshot_id, name);
688 if (snapshot_index < 0) {
689 error_setg(errp,
690 "Can't find snapshot");
691 return -ENOENT;
692 }
693 sn = &s->snapshots[snapshot_index];
694
695 /* Allocate and read in the snapshot's L1 table */
696 if (sn->l1_size > QCOW_MAX_L1_SIZE) {
697 error_setg(errp, "Snapshot L1 table too large");
698 return -EFBIG;
699 }
700 new_l1_bytes = sn->l1_size * sizeof(uint64_t);
701 new_l1_table = g_malloc0(align_offset(new_l1_bytes, 512));
702
703 ret = bdrv_pread(bs->file, sn->l1_table_offset, new_l1_table, new_l1_bytes);
704 if (ret < 0) {
705 error_setg(errp, "Failed to read l1 table for snapshot");
706 g_free(new_l1_table);
707 return ret;
708 }
709
710 /* Switch the L1 table */
711 g_free(s->l1_table);
712
713 s->l1_size = sn->l1_size;
714 s->l1_table_offset = sn->l1_table_offset;
715 s->l1_table = new_l1_table;
716
717 for(i = 0;i < s->l1_size; i++) {
718 be64_to_cpus(&s->l1_table[i]);
719 }
720
721 return 0;
722 }