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 child of given BDS 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 static BdrvChild * GRAPH_RDLOCK
 159 bdrv_snapshot_fallback_child(BlockDriverState *bs)
 160 {
 161     BdrvChild *fallback = bdrv_primary_child(bs);
 162     BdrvChild *child;
 163
 164     GLOBAL_STATE_CODE();
 165     assert_bdrv_graph_readable();
 166
 167     /* We allow fallback only to primary child */
 168     if (!fallback) {
 169         return NULL;
 170     }
 171
 172     /*
 173      * Check that there are no other children that would need to be
 174      * snapshotted.  If there are, it is not safe to fall back to
 175      * fallback.
 176      */
 177     QLIST_FOREACH(child, &bs->children, next) {
 178         if (child->role & (BDRV_CHILD_DATA | BDRV_CHILD_METADATA |
 179                            BDRV_CHILD_FILTERED) &&
 180             child != fallback)
 181         {
 182             return NULL;
 183         }
 184     }
 185
 186     return fallback;
 187 }
 188
 189 static BlockDriverState * GRAPH_RDLOCK
 190 bdrv_snapshot_fallback(BlockDriverState *bs)
 191 {
 192     GLOBAL_STATE_CODE();
 193     return child_bs(bdrv_snapshot_fallback_child(bs));
 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;
 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     bdrv_graph_rdlock_main_loop();
 264     fallback = bdrv_snapshot_fallback_child(bs);
 265     bdrv_graph_rdunlock_main_loop();
 266
 267     if (fallback) {
 268         QDict *options;
 269         QDict *file_options;
 270         Error *local_err = NULL;
 271         BlockDriverState *fallback_bs = fallback->bs;
 272         char *subqdict_prefix = g_strdup_printf("%s.", fallback->name);
 273
 274         options = qdict_clone_shallow(bs->options);
 275
 276         /* Prevent it from getting deleted when detached from bs */
 277         bdrv_ref(fallback_bs);
 278
 279         qdict_extract_subqdict(options, &file_options, subqdict_prefix);
 280         qobject_unref(file_options);
 281         g_free(subqdict_prefix);
 282
 283         /* Force .bdrv_open() below to re-attach fallback_bs on fallback */
 284         qdict_put_str(options, fallback->name,
 285                       bdrv_get_node_name(fallback_bs));
 286
 287         /* Now close bs, apply the snapshot on fallback_bs, and re-open bs */
 288         if (drv->bdrv_close) {
 289             drv->bdrv_close(bs);
 290         }
 291
 292         /* .bdrv_open() will re-attach it */
 293         bdrv_graph_wrlock(NULL);
 294         bdrv_unref_child(bs, fallback);
 295         bdrv_graph_wrunlock();
 296
 297         ret = bdrv_snapshot_goto(fallback_bs, snapshot_id, errp);
 298         open_ret = drv->bdrv_open(bs, options, bs->open_flags, &local_err);
 299         qobject_unref(options);
 300         if (open_ret < 0) {
 301             bdrv_unref(fallback_bs);
 302             bs->drv = NULL;
 303             /* A bdrv_snapshot_goto() error takes precedence */
 304             error_propagate(errp, local_err);
 305             return ret < 0 ? ret : open_ret;
 306         }
 307
 308         /*
 309          * fallback was a primary child. It was closed above and set to NULL,
 310          * but the .bdrv_open() call has opened it again, because we set the
 311          * respective option (with the qdict_put_str() call above).
 312          * Assert that .bdrv_open() has attached the right BDS as primary child.
 313          */
 314         bdrv_graph_rdlock_main_loop();
 315         assert(bdrv_primary_bs(bs) == fallback_bs);
 316         bdrv_graph_rdunlock_main_loop();
 317
 318         bdrv_unref(fallback_bs);
 319         return ret;
 320     }
 321
 322     error_setg(errp, "Block driver does not support snapshots");
 323     return -ENOTSUP;
 324 }
 325
 326 /**
 327  * Delete an internal snapshot by @snapshot_id and @name.
 328  * @bs: block device used in the operation
 329  * @snapshot_id: unique snapshot ID, or NULL
 330  * @name: snapshot name, or NULL
 331  * @errp: location to store error
 332  *
 333  * If both @snapshot_id and @name are specified, delete the first one with
 334  * id @snapshot_id and name @name.
 335  * If only @snapshot_id is specified, delete the first one with id
 336  * @snapshot_id.
 337  * If only @name is specified, delete the first one with name @name.
 338  * if none is specified, return -EINVAL.
 339  *
 340  * Returns: 0 on success, -errno on failure. If @bs is not inserted, return
 341  * -ENOMEDIUM. If @snapshot_id and @name are both NULL, return -EINVAL. If @bs
 342  * does not support internal snapshot deletion, return -ENOTSUP. If @bs does
 343  * not support parameter @snapshot_id or @name, or one of them is not correctly
 344  * specified, return -EINVAL. If @bs can't find one matching @id and @name,
 345  * return -ENOENT. If @errp != NULL, it will always be filled with error
 346  * message on failure.
 347  */
 348 int bdrv_snapshot_delete(BlockDriverState *bs,
 349                          const char *snapshot_id,
 350                          const char *name,
 351                          Error **errp)
 352 {
 353     BlockDriver *drv = bs->drv;
 354     BlockDriverState *fallback_bs = bdrv_snapshot_fallback(bs);
 355     int ret;
 356
 357     GLOBAL_STATE_CODE();
 358
 359     if (!drv) {
 360         error_setg(errp, QERR_DEVICE_HAS_NO_MEDIUM, bdrv_get_device_name(bs));
 361         return -ENOMEDIUM;
 362     }
 363     if (!snapshot_id && !name) {
 364         error_setg(errp, "snapshot_id and name are both NULL");
 365         return -EINVAL;
 366     }
 367
 368     /* drain all pending i/o before deleting snapshot */
 369     bdrv_drained_begin(bs);
 370
 371     if (drv->bdrv_snapshot_delete) {
 372         ret = drv->bdrv_snapshot_delete(bs, snapshot_id, name, errp);
 373     } else if (fallback_bs) {
 374         ret = bdrv_snapshot_delete(fallback_bs, snapshot_id, name, errp);
 375     } else {
 376         error_setg(errp, "Block format '%s' used by device '%s' "
 377                    "does not support internal snapshot deletion",
 378                    drv->format_name, bdrv_get_device_name(bs));
 379         ret = -ENOTSUP;
 380     }
 381
 382     bdrv_drained_end(bs);
 383     return ret;
 384 }
 385
 386 int bdrv_snapshot_list(BlockDriverState *bs,
 387                        QEMUSnapshotInfo **psn_info)
 388 {
 389     GLOBAL_STATE_CODE();
 390     GRAPH_RDLOCK_GUARD_MAINLOOP();
 391
 392     BlockDriver *drv = bs->drv;
 393     BlockDriverState *fallback_bs = bdrv_snapshot_fallback(bs);
 394
 395     if (!drv) {
 396         return -ENOMEDIUM;
 397     }
 398     if (drv->bdrv_snapshot_list) {
 399         return drv->bdrv_snapshot_list(bs, psn_info);
 400     }
 401     if (fallback_bs) {
 402         return bdrv_snapshot_list(fallback_bs, psn_info);
 403     }
 404     return -ENOTSUP;
 405 }
 406
 407 /**
 408  * Temporarily load an internal snapshot by @snapshot_id and @name.
 409  * @bs: block device used in the operation
 410  * @snapshot_id: unique snapshot ID, or NULL
 411  * @name: snapshot name, or NULL
 412  * @errp: location to store error
 413  *
 414  * If both @snapshot_id and @name are specified, load the first one with
 415  * id @snapshot_id and name @name.
 416  * If only @snapshot_id is specified, load the first one with id
 417  * @snapshot_id.
 418  * If only @name is specified, load the first one with name @name.
 419  * if none is specified, return -EINVAL.
 420  *
 421  * Returns: 0 on success, -errno on fail. If @bs is not inserted, return
 422  * -ENOMEDIUM. If @bs is not readonly, return -EINVAL. If @bs did not support
 423  * internal snapshot, return -ENOTSUP. If qemu can't find a matching @id and
 424  * @name, return -ENOENT. If @errp != NULL, it will always be filled on
 425  * failure.
 426  */
 427 int bdrv_snapshot_load_tmp(BlockDriverState *bs,
 428                            const char *snapshot_id,
 429                            const char *name,
 430                            Error **errp)
 431 {
 432     BlockDriver *drv = bs->drv;
 433
 434     GLOBAL_STATE_CODE();
 435     GRAPH_RDLOCK_GUARD_MAINLOOP();
 436
 437     if (!drv) {
 438         error_setg(errp, QERR_DEVICE_HAS_NO_MEDIUM, bdrv_get_device_name(bs));
 439         return -ENOMEDIUM;
 440     }
 441     if (!snapshot_id && !name) {
 442         error_setg(errp, "snapshot_id and name are both NULL");
 443         return -EINVAL;
 444     }
 445     if (!bdrv_is_read_only(bs)) {
 446         error_setg(errp, "Device is not readonly");
 447         return -EINVAL;
 448     }
 449     if (drv->bdrv_snapshot_load_tmp) {
 450         return drv->bdrv_snapshot_load_tmp(bs, snapshot_id, name, errp);
 451     }
 452     error_setg(errp, "Block format '%s' used by device '%s' "
 453                "does not support temporarily loading internal snapshots",
 454                drv->format_name, bdrv_get_device_name(bs));
 455     return -ENOTSUP;
 456 }
 457
 458 int bdrv_snapshot_load_tmp_by_id_or_name(BlockDriverState *bs,
 459                                          const char *id_or_name,
 460                                          Error **errp)
 461 {
 462     int ret;
 463     Error *local_err = NULL;
 464
 465     GLOBAL_STATE_CODE();
 466
 467     ret = bdrv_snapshot_load_tmp(bs, id_or_name, NULL, &local_err);
 468     if (ret == -ENOENT || ret == -EINVAL) {
 469         error_free(local_err);
 470         local_err = NULL;
 471         ret = bdrv_snapshot_load_tmp(bs, NULL, id_or_name, &local_err);
 472     }
 473
 474     error_propagate(errp, local_err);
 475
 476     return ret;
 477 }
 478
 479
 480 static int GRAPH_RDLOCK
 481 bdrv_all_get_snapshot_devices(bool has_devices, strList *devices,
 482                               GList **all_bdrvs, Error **errp)
 483 {
 484     g_autoptr(GList) bdrvs = NULL;
 485
 486     if (has_devices) {
 487         if (!devices) {
 488             error_setg(errp, "At least one device is required for snapshot");
 489             return -1;
 490         }
 491
 492         while (devices) {
 493             BlockDriverState *bs = bdrv_find_node(devices->value);
 494             if (!bs) {
 495                 error_setg(errp, "No block device node '%s'", devices->value);
 496                 return -1;
 497             }
 498             bdrvs = g_list_append(bdrvs, bs);
 499             devices = devices->next;
 500         }
 501     } else {
 502         BlockDriverState *bs;
 503         BdrvNextIterator it;
 504         for (bs = bdrv_first(&it); bs; bs = bdrv_next(&it)) {
 505             bdrvs = g_list_append(bdrvs, bs);
 506         }
 507     }
 508
 509     *all_bdrvs = g_steal_pointer(&bdrvs);
 510     return 0;
 511 }
 512
 513
 514 static bool GRAPH_RDLOCK bdrv_all_snapshots_includes_bs(BlockDriverState *bs)
 515 {
 516     GLOBAL_STATE_CODE();
 517     assert_bdrv_graph_readable();
 518
 519     if (!bdrv_is_inserted(bs) || bdrv_is_read_only(bs)) {
 520         return false;
 521     }
 522
 523     /* Include all nodes that are either in use by a BlockBackend, or that
 524      * aren't attached to any node, but owned by the monitor. */
 525     return bdrv_has_blk(bs) || QLIST_EMPTY(&bs->parents);
 526 }
 527
 528 /* Group operations. All block drivers are involved.
 529  * These functions will properly handle dataplane (take aio_context_acquire
 530  * when appropriate for appropriate block drivers) */
 531
 532 bool bdrv_all_can_snapshot(bool has_devices, strList *devices,
 533                            Error **errp)
 534 {
 535     g_autoptr(GList) bdrvs = NULL;
 536     GList *iterbdrvs;
 537
 538     GLOBAL_STATE_CODE();
 539     GRAPH_RDLOCK_GUARD_MAINLOOP();
 540
 541     if (bdrv_all_get_snapshot_devices(has_devices, devices, &bdrvs, errp) < 0) {
 542         return false;
 543     }
 544
 545     iterbdrvs = bdrvs;
 546     while (iterbdrvs) {
 547         BlockDriverState *bs = iterbdrvs->data;
 548         AioContext *ctx = bdrv_get_aio_context(bs);
 549         bool ok = true;
 550
 551         aio_context_acquire(ctx);
 552         if (devices || bdrv_all_snapshots_includes_bs(bs)) {
 553             ok = bdrv_can_snapshot(bs);
 554         }
 555         aio_context_release(ctx);
 556         if (!ok) {
 557             error_setg(errp, "Device '%s' is writable but does not support "
 558                        "snapshots", bdrv_get_device_or_node_name(bs));
 559             return false;
 560         }
 561
 562         iterbdrvs = iterbdrvs->next;
 563     }
 564
 565     return true;
 566 }
 567
 568 int bdrv_all_delete_snapshot(const char *name,
 569                              bool has_devices, strList *devices,
 570                              Error **errp)
 571 {
 572     g_autoptr(GList) bdrvs = NULL;
 573     GList *iterbdrvs;
 574
 575     GLOBAL_STATE_CODE();
 576     GRAPH_RDLOCK_GUARD_MAINLOOP();
 577
 578     if (bdrv_all_get_snapshot_devices(has_devices, devices, &bdrvs, errp) < 0) {
 579         return -1;
 580     }
 581
 582     iterbdrvs = bdrvs;
 583     while (iterbdrvs) {
 584         BlockDriverState *bs = iterbdrvs->data;
 585         AioContext *ctx = bdrv_get_aio_context(bs);
 586         QEMUSnapshotInfo sn1, *snapshot = &sn1;
 587         int ret = 0;
 588
 589         aio_context_acquire(ctx);
 590         if ((devices || bdrv_all_snapshots_includes_bs(bs)) &&
 591             bdrv_snapshot_find(bs, snapshot, name) >= 0)
 592         {
 593             ret = bdrv_snapshot_delete(bs, snapshot->id_str,
 594                                        snapshot->name, errp);
 595         }
 596         aio_context_release(ctx);
 597         if (ret < 0) {
 598             error_prepend(errp, "Could not delete snapshot '%s' on '%s': ",
 599                           name, bdrv_get_device_or_node_name(bs));
 600             return -1;
 601         }
 602
 603         iterbdrvs = iterbdrvs->next;
 604     }
 605
 606     return 0;
 607 }
 608
 609
 610 int bdrv_all_goto_snapshot(const char *name,
 611                            bool has_devices, strList *devices,
 612                            Error **errp)
 613 {
 614     g_autoptr(GList) bdrvs = NULL;
 615     GList *iterbdrvs;
 616     int ret;
 617
 618     GLOBAL_STATE_CODE();
 619
 620     bdrv_graph_rdlock_main_loop();
 621     ret = bdrv_all_get_snapshot_devices(has_devices, devices, &bdrvs, errp);
 622     bdrv_graph_rdunlock_main_loop();
 623
 624     if (ret < 0) {
 625         return -1;
 626     }
 627
 628     iterbdrvs = bdrvs;
 629     while (iterbdrvs) {
 630         BlockDriverState *bs = iterbdrvs->data;
 631         AioContext *ctx = bdrv_get_aio_context(bs);
 632         int ret = 0;
 633         bool all_snapshots_includes_bs;
 634
 635         aio_context_acquire(ctx);
 636         bdrv_graph_rdlock_main_loop();
 637         all_snapshots_includes_bs = bdrv_all_snapshots_includes_bs(bs);
 638         bdrv_graph_rdunlock_main_loop();
 639
 640         if (devices || all_snapshots_includes_bs) {
 641             ret = bdrv_snapshot_goto(bs, name, errp);
 642         }
 643         aio_context_release(ctx);
 644         if (ret < 0) {
 645             bdrv_graph_rdlock_main_loop();
 646             error_prepend(errp, "Could not load snapshot '%s' on '%s': ",
 647                           name, bdrv_get_device_or_node_name(bs));
 648             bdrv_graph_rdunlock_main_loop();
 649             return -1;
 650         }
 651
 652         iterbdrvs = iterbdrvs->next;
 653     }
 654
 655     return 0;
 656 }
 657
 658 int bdrv_all_has_snapshot(const char *name,
 659                           bool has_devices, strList *devices,
 660                           Error **errp)
 661 {
 662     g_autoptr(GList) bdrvs = NULL;
 663     GList *iterbdrvs;
 664
 665     GLOBAL_STATE_CODE();
 666     GRAPH_RDLOCK_GUARD_MAINLOOP();
 667
 668     if (bdrv_all_get_snapshot_devices(has_devices, devices, &bdrvs, errp) < 0) {
 669         return -1;
 670     }
 671
 672     iterbdrvs = bdrvs;
 673     while (iterbdrvs) {
 674         BlockDriverState *bs = iterbdrvs->data;
 675         AioContext *ctx = bdrv_get_aio_context(bs);
 676         QEMUSnapshotInfo sn;
 677         int ret = 0;
 678
 679         aio_context_acquire(ctx);
 680         if (devices || bdrv_all_snapshots_includes_bs(bs)) {
 681             ret = bdrv_snapshot_find(bs, &sn, name);
 682         }
 683         aio_context_release(ctx);
 684         if (ret < 0) {
 685             if (ret == -ENOENT) {
 686                 return 0;
 687             } else {
 688                 error_setg_errno(errp, errno,
 689                                  "Could not check snapshot '%s' on '%s'",
 690                                  name, bdrv_get_device_or_node_name(bs));
 691                 return -1;
 692             }
 693         }
 694
 695         iterbdrvs = iterbdrvs->next;
 696     }
 697
 698     return 1;
 699 }
 700
 701 int bdrv_all_create_snapshot(QEMUSnapshotInfo *sn,
 702                              BlockDriverState *vm_state_bs,
 703                              uint64_t vm_state_size,
 704                              bool has_devices, strList *devices,
 705                              Error **errp)
 706 {
 707     g_autoptr(GList) bdrvs = NULL;
 708     GList *iterbdrvs;
 709
 710     GLOBAL_STATE_CODE();
 711     GRAPH_RDLOCK_GUARD_MAINLOOP();
 712
 713     if (bdrv_all_get_snapshot_devices(has_devices, devices, &bdrvs, errp) < 0) {
 714         return -1;
 715     }
 716
 717     iterbdrvs = bdrvs;
 718     while (iterbdrvs) {
 719         BlockDriverState *bs = iterbdrvs->data;
 720         AioContext *ctx = bdrv_get_aio_context(bs);
 721         int ret = 0;
 722
 723         aio_context_acquire(ctx);
 724         if (bs == vm_state_bs) {
 725             sn->vm_state_size = vm_state_size;
 726             ret = bdrv_snapshot_create(bs, sn);
 727         } else if (devices || bdrv_all_snapshots_includes_bs(bs)) {
 728             sn->vm_state_size = 0;
 729             ret = bdrv_snapshot_create(bs, sn);
 730         }
 731         aio_context_release(ctx);
 732         if (ret < 0) {
 733             error_setg(errp, "Could not create snapshot '%s' on '%s'",
 734                        sn->name, bdrv_get_device_or_node_name(bs));
 735             return -1;
 736         }
 737
 738         iterbdrvs = iterbdrvs->next;
 739     }
 740
 741     return 0;
 742 }
 743
 744
 745 BlockDriverState *bdrv_all_find_vmstate_bs(const char *vmstate_bs,
 746                                            bool has_devices, strList *devices,
 747                                            Error **errp)
 748 {
 749     g_autoptr(GList) bdrvs = NULL;
 750     GList *iterbdrvs;
 751
 752     GLOBAL_STATE_CODE();
 753     GRAPH_RDLOCK_GUARD_MAINLOOP();
 754
 755     if (bdrv_all_get_snapshot_devices(has_devices, devices, &bdrvs, errp) < 0) {
 756         return NULL;
 757     }
 758
 759     iterbdrvs = bdrvs;
 760     while (iterbdrvs) {
 761         BlockDriverState *bs = iterbdrvs->data;
 762         AioContext *ctx = bdrv_get_aio_context(bs);
 763         bool found = false;
 764
 765         aio_context_acquire(ctx);
 766         found = (devices || bdrv_all_snapshots_includes_bs(bs)) &&
 767             bdrv_can_snapshot(bs);
 768         aio_context_release(ctx);
 769
 770         if (vmstate_bs) {
 771             if (g_str_equal(vmstate_bs,
 772                             bdrv_get_node_name(bs))) {
 773                 if (found) {
 774                     return bs;
 775                 } else {
 776                     error_setg(errp,
 777                                "vmstate block device '%s' does not support snapshots",
 778                                vmstate_bs);
 779                     return NULL;
 780                 }
 781             }
 782         } else if (found) {
 783             return bs;
 784         }
 785
 786         iterbdrvs = iterbdrvs->next;
 787     }
 788
 789     if (vmstate_bs) {
 790         error_setg(errp,
 791                    "vmstate block device '%s' does not exist", vmstate_bs);
 792     } else {
 793         error_setg(errp,
 794                    "no block device can store vmstate for snapshot");
 795     }
 796     return NULL;
 797 }