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