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