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
 200     GLOBAL_STATE_CODE();
 201
 202     if (!drv || !bdrv_is_inserted(bs) || !bdrv_is_writable(bs)) {
 203         return 0;
 204     }
 205
 206     if (!drv->bdrv_snapshot_create) {
 207         BlockDriverState *fallback_bs = bdrv_snapshot_fallback(bs);
 208         if (fallback_bs) {
 209             return bdrv_can_snapshot(fallback_bs);
 210         }
 211         return 0;
 212     }
 213
 214     return 1;
 215 }
 216
 217 int bdrv_snapshot_create(BlockDriverState *bs,
 218                          QEMUSnapshotInfo *sn_info)
 219 {
 220     BlockDriver *drv = bs->drv;
 221     BlockDriverState *fallback_bs = bdrv_snapshot_fallback(bs);
 222
 223     GLOBAL_STATE_CODE();
 224
 225     if (!drv) {
 226         return -ENOMEDIUM;
 227     }
 228     if (drv->bdrv_snapshot_create) {
 229         return drv->bdrv_snapshot_create(bs, sn_info);
 230     }
 231     if (fallback_bs) {
 232         return bdrv_snapshot_create(fallback_bs, sn_info);
 233     }
 234     return -ENOTSUP;
 235 }
 236
 237 int bdrv_snapshot_goto(BlockDriverState *bs,
 238                        const char *snapshot_id,
 239                        Error **errp)
 240 {
 241     BlockDriver *drv = bs->drv;
 242     BdrvChild *fallback;
 243     int ret, open_ret;
 244
 245     GLOBAL_STATE_CODE();
 246
 247     if (!drv) {
 248         error_setg(errp, "Block driver is closed");
 249         return -ENOMEDIUM;
 250     }
 251
 252     if (!QLIST_EMPTY(&bs->dirty_bitmaps)) {
 253         error_setg(errp, "Device has active dirty bitmaps");
 254         return -EBUSY;
 255     }
 256
 257     if (drv->bdrv_snapshot_goto) {
 258         ret = drv->bdrv_snapshot_goto(bs, snapshot_id);
 259         if (ret < 0) {
 260             error_setg_errno(errp, -ret, "Failed to load snapshot");
 261         }
 262         return ret;
 263     }
 264
 265     bdrv_graph_rdlock_main_loop();
 266     fallback = bdrv_snapshot_fallback_child(bs);
 267     bdrv_graph_rdunlock_main_loop();
 268
 269     if (fallback) {
 270         QDict *options;
 271         QDict *file_options;
 272         Error *local_err = NULL;
 273         BlockDriverState *fallback_bs = fallback->bs;
 274         char *subqdict_prefix = g_strdup_printf("%s.", fallback->name);
 275
 276         options = qdict_clone_shallow(bs->options);
 277
 278         /* Prevent it from getting deleted when detached from bs */
 279         bdrv_ref(fallback_bs);
 280
 281         qdict_extract_subqdict(options, &file_options, subqdict_prefix);
 282         qobject_unref(file_options);
 283         g_free(subqdict_prefix);
 284
 285         /* Force .bdrv_open() below to re-attach fallback_bs on fallback */
 286         qdict_put_str(options, fallback->name,
 287                       bdrv_get_node_name(fallback_bs));
 288
 289         /* Now close bs, apply the snapshot on fallback_bs, and re-open bs */
 290         if (drv->bdrv_close) {
 291             drv->bdrv_close(bs);
 292         }
 293
 294         /* .bdrv_open() will re-attach it */
 295         bdrv_graph_wrlock(NULL);
 296         bdrv_unref_child(bs, fallback);
 297         bdrv_graph_wrunlock(NULL);
 298
 299         ret = bdrv_snapshot_goto(fallback_bs, snapshot_id, errp);
 300         open_ret = drv->bdrv_open(bs, options, bs->open_flags, &local_err);
 301         qobject_unref(options);
 302         if (open_ret < 0) {
 303             bdrv_unref(fallback_bs);
 304             bs->drv = NULL;
 305             /* A bdrv_snapshot_goto() error takes precedence */
 306             error_propagate(errp, local_err);
 307             return ret < 0 ? ret : open_ret;
 308         }
 309
 310         /*
 311          * fallback was a primary child. It was closed above and set to NULL,
 312          * but the .bdrv_open() call has opened it again, because we set the
 313          * respective option (with the qdict_put_str() call above).
 314          * Assert that .bdrv_open() has attached the right BDS as primary child.
 315          */
 316         bdrv_graph_rdlock_main_loop();
 317         assert(bdrv_primary_bs(bs) == fallback_bs);
 318         bdrv_graph_rdunlock_main_loop();
 319
 320         bdrv_unref(fallback_bs);
 321         return ret;
 322     }
 323
 324     error_setg(errp, "Block driver does not support snapshots");
 325     return -ENOTSUP;
 326 }
 327
 328 /**
 329  * Delete an internal snapshot by @snapshot_id and @name.
 330  * @bs: block device used in the operation
 331  * @snapshot_id: unique snapshot ID, or NULL
 332  * @name: snapshot name, or NULL
 333  * @errp: location to store error
 334  *
 335  * If both @snapshot_id and @name are specified, delete the first one with
 336  * id @snapshot_id and name @name.
 337  * If only @snapshot_id is specified, delete the first one with id
 338  * @snapshot_id.
 339  * If only @name is specified, delete the first one with name @name.
 340  * if none is specified, return -EINVAL.
 341  *
 342  * Returns: 0 on success, -errno on failure. If @bs is not inserted, return
 343  * -ENOMEDIUM. If @snapshot_id and @name are both NULL, return -EINVAL. If @bs
 344  * does not support internal snapshot deletion, return -ENOTSUP. If @bs does
 345  * not support parameter @snapshot_id or @name, or one of them is not correctly
 346  * specified, return -EINVAL. If @bs can't find one matching @id and @name,
 347  * return -ENOENT. If @errp != NULL, it will always be filled with error
 348  * message on failure.
 349  */
 350 int bdrv_snapshot_delete(BlockDriverState *bs,
 351                          const char *snapshot_id,
 352                          const char *name,
 353                          Error **errp)
 354 {
 355     BlockDriver *drv = bs->drv;
 356     BlockDriverState *fallback_bs = bdrv_snapshot_fallback(bs);
 357     int ret;
 358
 359     GLOBAL_STATE_CODE();
 360
 361     if (!drv) {
 362         error_setg(errp, QERR_DEVICE_HAS_NO_MEDIUM, 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, QERR_DEVICE_HAS_NO_MEDIUM, bdrv_get_device_name(bs));
 441         return -ENOMEDIUM;
 442     }
 443     if (!snapshot_id && !name) {
 444         error_setg(errp, "snapshot_id and name are both NULL");
 445         return -EINVAL;
 446     }
 447     if (!bdrv_is_read_only(bs)) {
 448         error_setg(errp, "Device is not readonly");
 449         return -EINVAL;
 450     }
 451     if (drv->bdrv_snapshot_load_tmp) {
 452         return drv->bdrv_snapshot_load_tmp(bs, snapshot_id, name, errp);
 453     }
 454     error_setg(errp, "Block format '%s' used by device '%s' "
 455                "does not support temporarily loading internal snapshots",
 456                drv->format_name, bdrv_get_device_name(bs));
 457     return -ENOTSUP;
 458 }
 459
 460 int bdrv_snapshot_load_tmp_by_id_or_name(BlockDriverState *bs,
 461                                          const char *id_or_name,
 462                                          Error **errp)
 463 {
 464     int ret;
 465     Error *local_err = NULL;
 466
 467     GLOBAL_STATE_CODE();
 468
 469     ret = bdrv_snapshot_load_tmp(bs, id_or_name, NULL, &local_err);
 470     if (ret == -ENOENT || ret == -EINVAL) {
 471         error_free(local_err);
 472         local_err = NULL;
 473         ret = bdrv_snapshot_load_tmp(bs, NULL, id_or_name, &local_err);
 474     }
 475
 476     error_propagate(errp, local_err);
 477
 478     return ret;
 479 }
 480
 481
 482 static int GRAPH_RDLOCK
 483 bdrv_all_get_snapshot_devices(bool has_devices, strList *devices,
 484                               GList **all_bdrvs, Error **errp)
 485 {
 486     g_autoptr(GList) bdrvs = NULL;
 487
 488     if (has_devices) {
 489         if (!devices) {
 490             error_setg(errp, "At least one device is required for snapshot");
 491             return -1;
 492         }
 493
 494         while (devices) {
 495             BlockDriverState *bs = bdrv_find_node(devices->value);
 496             if (!bs) {
 497                 error_setg(errp, "No block device node '%s'", devices->value);
 498                 return -1;
 499             }
 500             bdrvs = g_list_append(bdrvs, bs);
 501             devices = devices->next;
 502         }
 503     } else {
 504         BlockDriverState *bs;
 505         BdrvNextIterator it;
 506         for (bs = bdrv_first(&it); bs; bs = bdrv_next(&it)) {
 507             bdrvs = g_list_append(bdrvs, bs);
 508         }
 509     }
 510
 511     *all_bdrvs = g_steal_pointer(&bdrvs);
 512     return 0;
 513 }
 514
 515
 516 static bool GRAPH_RDLOCK bdrv_all_snapshots_includes_bs(BlockDriverState *bs)
 517 {
 518     GLOBAL_STATE_CODE();
 519     assert_bdrv_graph_readable();
 520
 521     if (!bdrv_is_inserted(bs) || bdrv_is_read_only(bs)) {
 522         return false;
 523     }
 524
 525     /* Include all nodes that are either in use by a BlockBackend, or that
 526      * aren't attached to any node, but owned by the monitor. */
 527     return bdrv_has_blk(bs) || QLIST_EMPTY(&bs->parents);
 528 }
 529
 530 /* Group operations. All block drivers are involved.
 531  * These functions will properly handle dataplane (take aio_context_acquire
 532  * when appropriate for appropriate block drivers) */
 533
 534 bool bdrv_all_can_snapshot(bool has_devices, strList *devices,
 535                            Error **errp)
 536 {
 537     g_autoptr(GList) bdrvs = NULL;
 538     GList *iterbdrvs;
 539
 540     GLOBAL_STATE_CODE();
 541     GRAPH_RDLOCK_GUARD_MAINLOOP();
 542
 543     if (bdrv_all_get_snapshot_devices(has_devices, devices, &bdrvs, errp) < 0) {
 544         return false;
 545     }
 546
 547     iterbdrvs = bdrvs;
 548     while (iterbdrvs) {
 549         BlockDriverState *bs = iterbdrvs->data;
 550         AioContext *ctx = bdrv_get_aio_context(bs);
 551         bool ok = true;
 552
 553         aio_context_acquire(ctx);
 554         if (devices || bdrv_all_snapshots_includes_bs(bs)) {
 555             ok = bdrv_can_snapshot(bs);
 556         }
 557         aio_context_release(ctx);
 558         if (!ok) {
 559             error_setg(errp, "Device '%s' is writable but does not support "
 560                        "snapshots", bdrv_get_device_or_node_name(bs));
 561             return false;
 562         }
 563
 564         iterbdrvs = iterbdrvs->next;
 565     }
 566
 567     return true;
 568 }
 569
 570 int bdrv_all_delete_snapshot(const char *name,
 571                              bool has_devices, strList *devices,
 572                              Error **errp)
 573 {
 574     g_autoptr(GList) bdrvs = NULL;
 575     GList *iterbdrvs;
 576
 577     GLOBAL_STATE_CODE();
 578     GRAPH_RDLOCK_GUARD_MAINLOOP();
 579
 580     if (bdrv_all_get_snapshot_devices(has_devices, devices, &bdrvs, errp) < 0) {
 581         return -1;
 582     }
 583
 584     iterbdrvs = bdrvs;
 585     while (iterbdrvs) {
 586         BlockDriverState *bs = iterbdrvs->data;
 587         AioContext *ctx = bdrv_get_aio_context(bs);
 588         QEMUSnapshotInfo sn1, *snapshot = &sn1;
 589         int ret = 0;
 590
 591         aio_context_acquire(ctx);
 592         if ((devices || bdrv_all_snapshots_includes_bs(bs)) &&
 593             bdrv_snapshot_find(bs, snapshot, name) >= 0)
 594         {
 595             ret = bdrv_snapshot_delete(bs, snapshot->id_str,
 596                                        snapshot->name, errp);
 597         }
 598         aio_context_release(ctx);
 599         if (ret < 0) {
 600             error_prepend(errp, "Could not delete snapshot '%s' on '%s': ",
 601                           name, bdrv_get_device_or_node_name(bs));
 602             return -1;
 603         }
 604
 605         iterbdrvs = iterbdrvs->next;
 606     }
 607
 608     return 0;
 609 }
 610
 611
 612 int bdrv_all_goto_snapshot(const char *name,
 613                            bool has_devices, strList *devices,
 614                            Error **errp)
 615 {
 616     g_autoptr(GList) bdrvs = NULL;
 617     GList *iterbdrvs;
 618     int ret;
 619
 620     GLOBAL_STATE_CODE();
 621
 622     bdrv_graph_rdlock_main_loop();
 623     ret = bdrv_all_get_snapshot_devices(has_devices, devices, &bdrvs, errp);
 624     bdrv_graph_rdunlock_main_loop();
 625
 626     if (ret < 0) {
 627         return -1;
 628     }
 629
 630     iterbdrvs = bdrvs;
 631     while (iterbdrvs) {
 632         BlockDriverState *bs = iterbdrvs->data;
 633         AioContext *ctx = bdrv_get_aio_context(bs);
 634         bool all_snapshots_includes_bs;
 635
 636         aio_context_acquire(ctx);
 637         bdrv_graph_rdlock_main_loop();
 638         all_snapshots_includes_bs = bdrv_all_snapshots_includes_bs(bs);
 639         bdrv_graph_rdunlock_main_loop();
 640
 641         ret = (devices || all_snapshots_includes_bs) ?
 642               bdrv_snapshot_goto(bs, name, errp) : 0;
 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 }