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