block/snapshot.c

   1 /*
   2  * Block layer snapshot related functions
   3  *
   4  * Copyright (c) 2003-2008 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/osdep.h"
  26 #include "block/snapshot.h"
  27 #include "block/block_int.h"
  28 #include "block/qdict.h"
  29 #include "qapi/error.h"
  30 #include "qapi/qmp/qdict.h"
  31 #include "qapi/qmp/qstring.h"
  32 #include "qemu/option.h"
  33 #include "sysemu/block-backend.h"
  34
  35 QemuOptsList internal_snapshot_opts = {
  36     .name = "snapshot",
  37     .head = QTAILQ_HEAD_INITIALIZER(internal_snapshot_opts.head),
  38     .desc = {
  39         {
  40             .name = SNAPSHOT_OPT_ID,
  41             .type = QEMU_OPT_STRING,
  42             .help = "snapshot id"
  43         },{
  44             .name = SNAPSHOT_OPT_NAME,
  45             .type = QEMU_OPT_STRING,
  46             .help = "snapshot name"
  47         },{
  48             /* end of list */
  49         }
  50     },
  51 };
  52
  53 int bdrv_snapshot_find(BlockDriverState *bs, QEMUSnapshotInfo *sn_info,
  54                        const char *name)
  55 {
  56     QEMUSnapshotInfo *sn_tab, *sn;
  57     int nb_sns, i, ret;
  58
  59     GLOBAL_STATE_CODE();
  60
  61     ret = -ENOENT;
  62     nb_sns = bdrv_snapshot_list(bs, &sn_tab);
  63     if (nb_sns < 0) {
  64         return ret;
  65     }
  66     for (i = 0; i < nb_sns; i++) {
  67         sn = &sn_tab[i];
  68         if (!strcmp(sn->name, name)) {
  69             *sn_info = *sn;
  70             ret = 0;
  71             break;
  72         }
  73     }
  74     g_free(sn_tab);
  75     return ret;
  76 }
  77
  78 /**
  79  * Look up an internal snapshot by @id and @name.
  80  * @bs: block device to search
  81  * @id: unique snapshot ID, or NULL
  82  * @name: snapshot name, or NULL
  83  * @sn_info: location to store information on the snapshot found
  84  * @errp: location to store error, will be set only for exception
  85  *
  86  * This function will traverse snapshot list in @bs to search the matching
  87  * one, @id and @name are the matching condition:
  88  * If both @id and @name are specified, find the first one with id @id and
  89  * name @name.
  90  * If only @id is specified, find the first one with id @id.
  91  * If only @name is specified, find the first one with name @name.
  92  * if none is specified, abort().
  93  *
  94  * Returns: true when a snapshot is found and @sn_info will be filled, false
  95  * when error or not found. If all operation succeed but no matching one is
  96  * found, @errp will NOT be set.
  97  */
  98 bool bdrv_snapshot_find_by_id_and_name(BlockDriverState *bs,
  99                                        const char *id,
 100                                        const char *name,
 101                                        QEMUSnapshotInfo *sn_info,
 102                                        Error **errp)
 103 {
 104     QEMUSnapshotInfo *sn_tab, *sn;
 105     int nb_sns, i;
 106     bool ret = false;
 107
 108     assert(id || name);
 109     GLOBAL_STATE_CODE();
 110
 111     nb_sns = bdrv_snapshot_list(bs, &sn_tab);
 112     if (nb_sns < 0) {
 113         error_setg_errno(errp, -nb_sns, "Failed to get a snapshot list");
 114         return false;
 115     } else if (nb_sns == 0) {
 116         return false;
 117     }
 118
 119     if (id && name) {
 120         for (i = 0; i < nb_sns; i++) {
 121             sn = &sn_tab[i];
 122             if (!strcmp(sn->id_str, id) && !strcmp(sn->name, name)) {
 123                 *sn_info = *sn;
 124                 ret = true;
 125                 break;
 126             }
 127         }
 128     } else if (id) {
 129         for (i = 0; i < nb_sns; i++) {
 130             sn = &sn_tab[i];
 131             if (!strcmp(sn->id_str, id)) {
 132                 *sn_info = *sn;
 133                 ret = true;
 134                 break;
 135             }
 136         }
 137     } else if (name) {
 138         for (i = 0; i < nb_sns; i++) {
 139             sn = &sn_tab[i];
 140             if (!strcmp(sn->name, name)) {
 141                 *sn_info = *sn;
 142                 ret = true;
 143                 break;
 144             }
 145         }
 146     }
 147
 148     g_free(sn_tab);
 149     return ret;
 150 }
 151
 152 /**
 153  * Return a pointer to child of given BDS to which we can fall
 154  * back if the given BDS does not support snapshots.
 155  * Return NULL if there is no BDS to (safely) fall back to.
 156  */
 157 static BdrvChild * GRAPH_RDLOCK
 158 bdrv_snapshot_fallback_child(BlockDriverState *bs)
 159 {
 160     BdrvChild *fallback = bdrv_primary_child(bs);
 161     BdrvChild *child;
 162
 163     GLOBAL_STATE_CODE();
 164     assert_bdrv_graph_readable();
 165
 166     /* We allow fallback only to primary child */
 167     if (!fallback) {
 168         return NULL;
 169     }
 170
 171     /*
 172      * Check that there are no other children that would need to be
 173      * snapshotted.  If there are, it is not safe to fall back to
 174      * fallback.
 175      */
 176     QLIST_FOREACH(child, &bs->children, next) {
 177         if (child->role & (BDRV_CHILD_DATA | BDRV_CHILD_METADATA |
 178                            BDRV_CHILD_FILTERED) &&
 179             child != fallback)
 180         {
 181             return NULL;
 182         }
 183     }
 184
 185     return fallback;
 186 }
 187
 188 static BlockDriverState * GRAPH_RDLOCK
 189 bdrv_snapshot_fallback(BlockDriverState *bs)
 190 {
 191     GLOBAL_STATE_CODE();
 192     return child_bs(bdrv_snapshot_fallback_child(bs));
 193 }
 194
 195 int bdrv_can_snapshot(BlockDriverState *bs)
 196 {
 197     BlockDriver *drv = bs->drv;
 198
 199     GLOBAL_STATE_CODE();
 200
 201     if (!drv || !bdrv_is_inserted(bs) || !bdrv_is_writable(bs)) {
 202         return 0;
 203     }
 204
 205     if (!drv->bdrv_snapshot_create) {
 206         BlockDriverState *fallback_bs = bdrv_snapshot_fallback(bs);
 207         if (fallback_bs) {
 208             return bdrv_can_snapshot(fallback_bs);
 209         }
 210         return 0;
 211     }
 212
 213     return 1;
 214 }
 215
 216 int bdrv_snapshot_create(BlockDriverState *bs,
 217                          QEMUSnapshotInfo *sn_info)
 218 {
 219     BlockDriver *drv = bs->drv;
 220     BlockDriverState *fallback_bs = bdrv_snapshot_fallback(bs);
 221
 222     GLOBAL_STATE_CODE();
 223
 224     if (!drv) {
 225         return -ENOMEDIUM;
 226     }
 227     if (drv->bdrv_snapshot_create) {
 228         return drv->bdrv_snapshot_create(bs, sn_info);
 229     }
 230     if (fallback_bs) {
 231         return bdrv_snapshot_create(fallback_bs, sn_info);
 232     }
 233     return -ENOTSUP;
 234 }
 235
 236 int bdrv_snapshot_goto(BlockDriverState *bs,
 237                        const char *snapshot_id,
 238                        Error **errp)
 239 {
 240     BlockDriver *drv = bs->drv;
 241     BdrvChild *fallback;
 242     int ret, open_ret;
 243
 244     GLOBAL_STATE_CODE();
 245
 246     if (!drv) {
 247         error_setg(errp, "Block driver is closed");
 248         return -ENOMEDIUM;
 249     }
 250
 251     if (!QLIST_EMPTY(&bs->dirty_bitmaps)) {
 252         error_setg(errp, "Device has active dirty bitmaps");
 253         return -EBUSY;
 254     }
 255
 256     if (drv->bdrv_snapshot_goto) {
 257         ret = drv->bdrv_snapshot_goto(bs, snapshot_id);
 258         if (ret < 0) {
 259             error_setg_errno(errp, -ret, "Failed to load snapshot");
 260         }
 261         return ret;
 262     }
 263
 264     bdrv_graph_rdlock_main_loop();
 265     fallback = bdrv_snapshot_fallback_child(bs);
 266     bdrv_graph_rdunlock_main_loop();
 267
 268     if (fallback) {
 269         QDict *options;
 270         QDict *file_options;
 271         Error *local_err = NULL;
 272         BlockDriverState *fallback_bs = fallback->bs;
 273         char *subqdict_prefix = g_strdup_printf("%s.", fallback->name);
 274
 275         options = qdict_clone_shallow(bs->options);
 276
 277         /* Prevent it from getting deleted when detached from bs */
 278         bdrv_ref(fallback_bs);
 279
 280         qdict_extract_subqdict(options, &file_options, subqdict_prefix);
 281         qobject_unref(file_options);
 282         g_free(subqdict_prefix);
 283
 284         /* Force .bdrv_open() below to re-attach fallback_bs on fallback */
 285         qdict_put_str(options, fallback->name,
 286                       bdrv_get_node_name(fallback_bs));
 287
 288         /* Now close bs, apply the snapshot on fallback_bs, and re-open bs */
 289         if (drv->bdrv_close) {
 290             drv->bdrv_close(bs);
 291         }
 292
 293         /* .bdrv_open() will re-attach it */
 294         bdrv_graph_wrlock();
 295         bdrv_unref_child(bs, fallback);
 296         bdrv_graph_wrunlock();
 297
 298         ret = bdrv_snapshot_goto(fallback_bs, snapshot_id, errp);
 299         open_ret = drv->bdrv_open(bs, options, bs->open_flags, &local_err);
 300         qobject_unref(options);
 301         if (open_ret < 0) {
 302             bdrv_unref(fallback_bs);
 303             bs->drv = NULL;
 304             /* A bdrv_snapshot_goto() error takes precedence */
 305             error_propagate(errp, local_err);
 306             return ret < 0 ? ret : open_ret;
 307         }
 308
 309         /*
 310          * fallback was a primary child. It was closed above and set to NULL,
 311          * but the .bdrv_open() call has opened it again, because we set the
 312          * respective option (with the qdict_put_str() call above).
 313          * Assert that .bdrv_open() has attached the right BDS as primary child.
 314          */
 315         bdrv_graph_rdlock_main_loop();
 316         assert(bdrv_primary_bs(bs) == fallback_bs);
 317         bdrv_graph_rdunlock_main_loop();
 318
 319         bdrv_unref(fallback_bs);
 320         return ret;
 321     }
 322
 323     error_setg(errp, "Block driver does not support snapshots");
 324     return -ENOTSUP;
 325 }
 326
 327 /**
 328  * Delete an internal snapshot by @snapshot_id and @name.
 329  * @bs: block device used in the operation
 330  * @snapshot_id: unique snapshot ID, or NULL
 331  * @name: snapshot name, or NULL
 332  * @errp: location to store error
 333  *
 334  * If both @snapshot_id and @name are specified, delete the first one with
 335  * id @snapshot_id and name @name.
 336  * If only @snapshot_id is specified, delete the first one with id
 337  * @snapshot_id.
 338  * If only @name is specified, delete the first one with name @name.
 339  * if none is specified, return -EINVAL.
 340  *
 341  * Returns: 0 on success, -errno on failure. If @bs is not inserted, return
 342  * -ENOMEDIUM. If @snapshot_id and @name are both NULL, return -EINVAL. If @bs
 343  * does not support internal snapshot deletion, return -ENOTSUP. If @bs does
 344  * not support parameter @snapshot_id or @name, or one of them is not correctly
 345  * specified, return -EINVAL. If @bs can't find one matching @id and @name,
 346  * return -ENOENT. If @errp != NULL, it will always be filled with error
 347  * message on failure.
 348  */
 349 int bdrv_snapshot_delete(BlockDriverState *bs,
 350                          const char *snapshot_id,
 351                          const char *name,
 352                          Error **errp)
 353 {
 354     BlockDriver *drv = bs->drv;
 355     BlockDriverState *fallback_bs = bdrv_snapshot_fallback(bs);
 356     int ret;
 357
 358     GLOBAL_STATE_CODE();
 359
 360     if (!drv) {
 361         error_setg(errp, "Device '%s' has no medium",
 362                    bdrv_get_device_name(bs));
 363         return -ENOMEDIUM;
 364     }
 365     if (!snapshot_id && !name) {
 366         error_setg(errp, "snapshot_id and name are both NULL");
 367         return -EINVAL;
 368     }
 369
 370     /* drain all pending i/o before deleting snapshot */
 371     bdrv_drained_begin(bs);
 372
 373     if (drv->bdrv_snapshot_delete) {
 374         ret = drv->bdrv_snapshot_delete(bs, snapshot_id, name, errp);
 375     } else if (fallback_bs) {
 376         ret = bdrv_snapshot_delete(fallback_bs, snapshot_id, name, errp);
 377     } else {
 378         error_setg(errp, "Block format '%s' used by device '%s' "
 379                    "does not support internal snapshot deletion",
 380                    drv->format_name, bdrv_get_device_name(bs));
 381         ret = -ENOTSUP;
 382     }
 383
 384     bdrv_drained_end(bs);
 385     return ret;
 386 }
 387
 388 int bdrv_snapshot_list(BlockDriverState *bs,
 389                        QEMUSnapshotInfo **psn_info)
 390 {
 391     GLOBAL_STATE_CODE();
 392     GRAPH_RDLOCK_GUARD_MAINLOOP();
 393
 394     BlockDriver *drv = bs->drv;
 395     BlockDriverState *fallback_bs = bdrv_snapshot_fallback(bs);
 396
 397     if (!drv) {
 398         return -ENOMEDIUM;
 399     }
 400     if (drv->bdrv_snapshot_list) {
 401         return drv->bdrv_snapshot_list(bs, psn_info);
 402     }
 403     if (fallback_bs) {
 404         return bdrv_snapshot_list(fallback_bs, psn_info);
 405     }
 406     return -ENOTSUP;
 407 }
 408
 409 /**
 410  * Temporarily load an internal snapshot by @snapshot_id and @name.
 411  * @bs: block device used in the operation
 412  * @snapshot_id: unique snapshot ID, or NULL
 413  * @name: snapshot name, or NULL
 414  * @errp: location to store error
 415  *
 416  * If both @snapshot_id and @name are specified, load the first one with
 417  * id @snapshot_id and name @name.
 418  * If only @snapshot_id is specified, load the first one with id
 419  * @snapshot_id.
 420  * If only @name is specified, load the first one with name @name.
 421  * if none is specified, return -EINVAL.
 422  *
 423  * Returns: 0 on success, -errno on fail. If @bs is not inserted, return
 424  * -ENOMEDIUM. If @bs is not readonly, return -EINVAL. If @bs did not support
 425  * internal snapshot, return -ENOTSUP. If qemu can't find a matching @id and
 426  * @name, return -ENOENT. If @errp != NULL, it will always be filled on
 427  * failure.
 428  */
 429 int bdrv_snapshot_load_tmp(BlockDriverState *bs,
 430                            const char *snapshot_id,
 431                            const char *name,
 432                            Error **errp)
 433 {
 434     BlockDriver *drv = bs->drv;
 435
 436     GLOBAL_STATE_CODE();
 437     GRAPH_RDLOCK_GUARD_MAINLOOP();
 438
 439     if (!drv) {
 440         error_setg(errp, "Device '%s' has no medium",
 441                    bdrv_get_device_name(bs));
 442         return -ENOMEDIUM;
 443     }
 444     if (!snapshot_id && !name) {
 445         error_setg(errp, "snapshot_id and name are both NULL");
 446         return -EINVAL;
 447     }
 448     if (!bdrv_is_read_only(bs)) {
 449         error_setg(errp, "Device is not readonly");
 450         return -EINVAL;
 451     }
 452     if (drv->bdrv_snapshot_load_tmp) {
 453         return drv->bdrv_snapshot_load_tmp(bs, snapshot_id, name, errp);
 454     }
 455     error_setg(errp, "Block format '%s' used by device '%s' "
 456                "does not support temporarily loading internal snapshots",
 457                drv->format_name, bdrv_get_device_name(bs));
 458     return -ENOTSUP;
 459 }
 460
 461 int bdrv_snapshot_load_tmp_by_id_or_name(BlockDriverState *bs,
 462                                          const char *id_or_name,
 463                                          Error **errp)
 464 {
 465     int ret;
 466     Error *local_err = NULL;
 467
 468     GLOBAL_STATE_CODE();
 469
 470     ret = bdrv_snapshot_load_tmp(bs, id_or_name, NULL, &local_err);
 471     if (ret == -ENOENT || ret == -EINVAL) {
 472         error_free(local_err);
 473         local_err = NULL;
 474         ret = bdrv_snapshot_load_tmp(bs, NULL, id_or_name, &local_err);
 475     }
 476
 477     error_propagate(errp, local_err);
 478
 479     return ret;
 480 }
 481
 482
 483 static int GRAPH_RDLOCK
 484 bdrv_all_get_snapshot_devices(bool has_devices, strList *devices,
 485                               GList **all_bdrvs, Error **errp)
 486 {
 487     g_autoptr(GList) bdrvs = NULL;
 488
 489     if (has_devices) {
 490         if (!devices) {
 491             error_setg(errp, "At least one device is required for snapshot");
 492             return -1;
 493         }
 494
 495         while (devices) {
 496             BlockDriverState *bs = bdrv_find_node(devices->value);
 497             if (!bs) {
 498                 error_setg(errp, "No block device node '%s'", devices->value);
 499                 return -1;
 500             }
 501             bdrvs = g_list_append(bdrvs, bs);
 502             devices = devices->next;
 503         }
 504     } else {
 505         BlockDriverState *bs;
 506         BdrvNextIterator it;
 507         for (bs = bdrv_first(&it); bs; bs = bdrv_next(&it)) {
 508             bdrvs = g_list_append(bdrvs, bs);
 509         }
 510     }
 511
 512     *all_bdrvs = g_steal_pointer(&bdrvs);
 513     return 0;
 514 }
 515
 516
 517 static bool GRAPH_RDLOCK bdrv_all_snapshots_includes_bs(BlockDriverState *bs)
 518 {
 519     GLOBAL_STATE_CODE();
 520     assert_bdrv_graph_readable();
 521
 522     if (!bdrv_is_inserted(bs) || bdrv_is_read_only(bs)) {
 523         return false;
 524     }
 525
 526     /* Include all nodes that are either in use by a BlockBackend, or that
 527      * aren't attached to any node, but owned by the monitor. */
 528     return bdrv_has_blk(bs) || QLIST_EMPTY(&bs->parents);
 529 }
 530
 531 /* Group operations. All block drivers are involved. */
 532
 533 bool bdrv_all_can_snapshot(bool has_devices, strList *devices,
 534                            Error **errp)
 535 {
 536     g_autoptr(GList) bdrvs = NULL;
 537     GList *iterbdrvs;
 538
 539     GLOBAL_STATE_CODE();
 540     GRAPH_RDLOCK_GUARD_MAINLOOP();
 541
 542     if (bdrv_all_get_snapshot_devices(has_devices, devices, &bdrvs, errp) < 0) {
 543         return false;
 544     }
 545
 546     iterbdrvs = bdrvs;
 547     while (iterbdrvs) {
 548         BlockDriverState *bs = iterbdrvs->data;
 549         bool ok = true;
 550
 551         if (devices || bdrv_all_snapshots_includes_bs(bs)) {
 552             ok = bdrv_can_snapshot(bs);
 553         }
 554         if (!ok) {
 555             error_setg(errp, "Device '%s' is writable but does not support "
 556                        "snapshots", bdrv_get_device_or_node_name(bs));
 557             return false;
 558         }
 559
 560         iterbdrvs = iterbdrvs->next;
 561     }
 562
 563     return true;
 564 }
 565
 566 int bdrv_all_delete_snapshot(const char *name,
 567                              bool has_devices, strList *devices,
 568                              Error **errp)
 569 {
 570     ERRP_GUARD();
 571     g_autoptr(GList) bdrvs = NULL;
 572     GList *iterbdrvs;
 573
 574     GLOBAL_STATE_CODE();
 575     GRAPH_RDLOCK_GUARD_MAINLOOP();
 576
 577     if (bdrv_all_get_snapshot_devices(has_devices, devices, &bdrvs, errp) < 0) {
 578         return -1;
 579     }
 580
 581     iterbdrvs = bdrvs;
 582     while (iterbdrvs) {
 583         BlockDriverState *bs = iterbdrvs->data;
 584         QEMUSnapshotInfo sn1, *snapshot = &sn1;
 585         int ret = 0;
 586
 587         if ((devices || bdrv_all_snapshots_includes_bs(bs)) &&
 588             bdrv_snapshot_find(bs, snapshot, name) >= 0)
 589         {
 590             ret = bdrv_snapshot_delete(bs, snapshot->id_str,
 591                                        snapshot->name, errp);
 592         }
 593         if (ret < 0) {
 594             error_prepend(errp, "Could not delete snapshot '%s' on '%s': ",
 595                           name, bdrv_get_device_or_node_name(bs));
 596             return -1;
 597         }
 598
 599         iterbdrvs = iterbdrvs->next;
 600     }
 601
 602     return 0;
 603 }
 604
 605
 606 int bdrv_all_goto_snapshot(const char *name,
 607                            bool has_devices, strList *devices,
 608                            Error **errp)
 609 {
 610     ERRP_GUARD();
 611     g_autoptr(GList) bdrvs = NULL;
 612     GList *iterbdrvs;
 613     int ret;
 614
 615     GLOBAL_STATE_CODE();
 616
 617     bdrv_graph_rdlock_main_loop();
 618     ret = bdrv_all_get_snapshot_devices(has_devices, devices, &bdrvs, errp);
 619     bdrv_graph_rdunlock_main_loop();
 620
 621     if (ret < 0) {
 622         return -1;
 623     }
 624
 625     iterbdrvs = bdrvs;
 626     while (iterbdrvs) {
 627         BlockDriverState *bs = iterbdrvs->data;
 628         bool all_snapshots_includes_bs;
 629
 630         bdrv_graph_rdlock_main_loop();
 631         all_snapshots_includes_bs = bdrv_all_snapshots_includes_bs(bs);
 632         bdrv_graph_rdunlock_main_loop();
 633
 634         ret = (devices || all_snapshots_includes_bs) ?
 635               bdrv_snapshot_goto(bs, name, errp) : 0;
 636         if (ret < 0) {
 637             bdrv_graph_rdlock_main_loop();
 638             error_prepend(errp, "Could not load snapshot '%s' on '%s': ",
 639                           name, bdrv_get_device_or_node_name(bs));
 640             bdrv_graph_rdunlock_main_loop();
 641             return -1;
 642         }
 643
 644         iterbdrvs = iterbdrvs->next;
 645     }
 646
 647     return 0;
 648 }
 649
 650 int bdrv_all_has_snapshot(const char *name,
 651                           bool has_devices, strList *devices,
 652                           Error **errp)
 653 {
 654     g_autoptr(GList) bdrvs = NULL;
 655     GList *iterbdrvs;
 656
 657     GLOBAL_STATE_CODE();
 658     GRAPH_RDLOCK_GUARD_MAINLOOP();
 659
 660     if (bdrv_all_get_snapshot_devices(has_devices, devices, &bdrvs, errp) < 0) {
 661         return -1;
 662     }
 663
 664     iterbdrvs = bdrvs;
 665     while (iterbdrvs) {
 666         BlockDriverState *bs = iterbdrvs->data;
 667         QEMUSnapshotInfo sn;
 668         int ret = 0;
 669
 670         if (devices || bdrv_all_snapshots_includes_bs(bs)) {
 671             ret = bdrv_snapshot_find(bs, &sn, name);
 672         }
 673         if (ret < 0) {
 674             if (ret == -ENOENT) {
 675                 return 0;
 676             } else {
 677                 error_setg_errno(errp, errno,
 678                                  "Could not check snapshot '%s' on '%s'",
 679                                  name, bdrv_get_device_or_node_name(bs));
 680                 return -1;
 681             }
 682         }
 683
 684         iterbdrvs = iterbdrvs->next;
 685     }
 686
 687     return 1;
 688 }
 689
 690 int bdrv_all_create_snapshot(QEMUSnapshotInfo *sn,
 691                              BlockDriverState *vm_state_bs,
 692                              uint64_t vm_state_size,
 693                              bool has_devices, strList *devices,
 694                              Error **errp)
 695 {
 696     g_autoptr(GList) bdrvs = NULL;
 697     GList *iterbdrvs;
 698
 699     GLOBAL_STATE_CODE();
 700     GRAPH_RDLOCK_GUARD_MAINLOOP();
 701
 702     if (bdrv_all_get_snapshot_devices(has_devices, devices, &bdrvs, errp) < 0) {
 703         return -1;
 704     }
 705
 706     iterbdrvs = bdrvs;
 707     while (iterbdrvs) {
 708         BlockDriverState *bs = iterbdrvs->data;
 709         int ret = 0;
 710
 711         if (bs == vm_state_bs) {
 712             sn->vm_state_size = vm_state_size;
 713             ret = bdrv_snapshot_create(bs, sn);
 714         } else if (devices || bdrv_all_snapshots_includes_bs(bs)) {
 715             sn->vm_state_size = 0;
 716             ret = bdrv_snapshot_create(bs, sn);
 717         }
 718         if (ret < 0) {
 719             error_setg(errp, "Could not create snapshot '%s' on '%s'",
 720                        sn->name, bdrv_get_device_or_node_name(bs));
 721             return -1;
 722         }
 723
 724         iterbdrvs = iterbdrvs->next;
 725     }
 726
 727     return 0;
 728 }
 729
 730
 731 BlockDriverState *bdrv_all_find_vmstate_bs(const char *vmstate_bs,
 732                                            bool has_devices, strList *devices,
 733                                            Error **errp)
 734 {
 735     g_autoptr(GList) bdrvs = NULL;
 736     GList *iterbdrvs;
 737
 738     GLOBAL_STATE_CODE();
 739     GRAPH_RDLOCK_GUARD_MAINLOOP();
 740
 741     if (bdrv_all_get_snapshot_devices(has_devices, devices, &bdrvs, errp) < 0) {
 742         return NULL;
 743     }
 744
 745     iterbdrvs = bdrvs;
 746     while (iterbdrvs) {
 747         BlockDriverState *bs = iterbdrvs->data;
 748         bool found = false;
 749
 750         found = (devices || bdrv_all_snapshots_includes_bs(bs)) &&
 751             bdrv_can_snapshot(bs);
 752
 753         if (vmstate_bs) {
 754             if (g_str_equal(vmstate_bs,
 755                             bdrv_get_node_name(bs))) {
 756                 if (found) {
 757                     return bs;
 758                 } else {
 759                     error_setg(errp,
 760                                "vmstate block device '%s' does not support snapshots",
 761                                vmstate_bs);
 762                     return NULL;
 763                 }
 764             }
 765         } else if (found) {
 766             return bs;
 767         }
 768
 769         iterbdrvs = iterbdrvs->next;
 770     }
 771
 772     if (vmstate_bs) {
 773         error_setg(errp,
 774                    "vmstate block device '%s' does not exist", vmstate_bs);
 775     } else {
 776         error_setg(errp,
 777                    "no block device can store vmstate for snapshot");
 778     }
 779     return NULL;
 780 }