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
  35 QemuOptsList internal_snapshot_opts = {
  36     .name = "snapshot",
  37     .head = QTAILQ_HEAD_INITIALIZER(internal_snapshot_opts.head),
  38     .desc = {
  39         {
  40             .name = SNAPSHOT_OPT_ID,
  41             .type = QEMU_OPT_STRING,
  42             .help = "snapshot id"
  43         },{
  44             .name = SNAPSHOT_OPT_NAME,
  45             .type = QEMU_OPT_STRING,
  46             .help = "snapshot name"
  47         },{
  48             /* end of list */
  49         }
  50     },
  51 };
  52
  53 int bdrv_snapshot_find(BlockDriverState *bs, QEMUSnapshotInfo *sn_info,
  54                        const char *name)
  55 {
  56     QEMUSnapshotInfo *sn_tab, *sn;
  57     int nb_sns, i, ret;
  58
  59     ret = -ENOENT;
  60     nb_sns = bdrv_snapshot_list(bs, &sn_tab);
  61     if (nb_sns < 0) {
  62         return ret;
  63     }
  64     for (i = 0; i < nb_sns; i++) {
  65         sn = &sn_tab[i];
  66         if (!strcmp(sn->name, name)) {
  67             *sn_info = *sn;
  68             ret = 0;
  69             break;
  70         }
  71     }
  72     g_free(sn_tab);
  73     return ret;
  74 }
  75
  76 /**
  77  * Look up an internal snapshot by @id and @name.
  78  * @bs: block device to search
  79  * @id: unique snapshot ID, or NULL
  80  * @name: snapshot name, or NULL
  81  * @sn_info: location to store information on the snapshot found
  82  * @errp: location to store error, will be set only for exception
  83  *
  84  * This function will traverse snapshot list in @bs to search the matching
  85  * one, @id and @name are the matching condition:
  86  * If both @id and @name are specified, find the first one with id @id and
  87  * name @name.
  88  * If only @id is specified, find the first one with id @id.
  89  * If only @name is specified, find the first one with name @name.
  90  * if none is specified, abort().
  91  *
  92  * Returns: true when a snapshot is found and @sn_info will be filled, false
  93  * when error or not found. If all operation succeed but no matching one is
  94  * found, @errp will NOT be set.
  95  */
  96 bool bdrv_snapshot_find_by_id_and_name(BlockDriverState *bs,
  97                                        const char *id,
  98                                        const char *name,
  99                                        QEMUSnapshotInfo *sn_info,
 100                                        Error **errp)
 101 {
 102     QEMUSnapshotInfo *sn_tab, *sn;
 103     int nb_sns, i;
 104     bool ret = false;
 105
 106     assert(id || name);
 107
 108     nb_sns = bdrv_snapshot_list(bs, &sn_tab);
 109     if (nb_sns < 0) {
 110         error_setg_errno(errp, -nb_sns, "Failed to get a snapshot list");
 111         return false;
 112     } else if (nb_sns == 0) {
 113         return false;
 114     }
 115
 116     if (id && name) {
 117         for (i = 0; i < nb_sns; i++) {
 118             sn = &sn_tab[i];
 119             if (!strcmp(sn->id_str, id) && !strcmp(sn->name, name)) {
 120                 *sn_info = *sn;
 121                 ret = true;
 122                 break;
 123             }
 124         }
 125     } else if (id) {
 126         for (i = 0; i < nb_sns; i++) {
 127             sn = &sn_tab[i];
 128             if (!strcmp(sn->id_str, id)) {
 129                 *sn_info = *sn;
 130                 ret = true;
 131                 break;
 132             }
 133         }
 134     } else if (name) {
 135         for (i = 0; i < nb_sns; i++) {
 136             sn = &sn_tab[i];
 137             if (!strcmp(sn->name, name)) {
 138                 *sn_info = *sn;
 139                 ret = true;
 140                 break;
 141             }
 142         }
 143     }
 144
 145     g_free(sn_tab);
 146     return ret;
 147 }
 148
 149 int bdrv_can_snapshot(BlockDriverState *bs)
 150 {
 151     BlockDriver *drv = bs->drv;
 152     if (!drv || !bdrv_is_inserted(bs) || bdrv_is_read_only(bs)) {
 153         return 0;
 154     }
 155
 156     if (!drv->bdrv_snapshot_create) {
 157         if (bs->file != NULL) {
 158             return bdrv_can_snapshot(bs->file->bs);
 159         }
 160         return 0;
 161     }
 162
 163     return 1;
 164 }
 165
 166 int bdrv_snapshot_create(BlockDriverState *bs,
 167                          QEMUSnapshotInfo *sn_info)
 168 {
 169     BlockDriver *drv = bs->drv;
 170     if (!drv) {
 171         return -ENOMEDIUM;
 172     }
 173     if (drv->bdrv_snapshot_create) {
 174         return drv->bdrv_snapshot_create(bs, sn_info);
 175     }
 176     if (bs->file) {
 177         return bdrv_snapshot_create(bs->file->bs, sn_info);
 178     }
 179     return -ENOTSUP;
 180 }
 181
 182 int bdrv_snapshot_goto(BlockDriverState *bs,
 183                        const char *snapshot_id,
 184                        Error **errp)
 185 {
 186     BlockDriver *drv = bs->drv;
 187     int ret, open_ret;
 188
 189     if (!drv) {
 190         error_setg(errp, "Block driver is closed");
 191         return -ENOMEDIUM;
 192     }
 193
 194     if (!QLIST_EMPTY(&bs->dirty_bitmaps)) {
 195         error_setg(errp, "Device has active dirty bitmaps");
 196         return -EBUSY;
 197     }
 198
 199     if (drv->bdrv_snapshot_goto) {
 200         ret = drv->bdrv_snapshot_goto(bs, snapshot_id);
 201         if (ret < 0) {
 202             error_setg_errno(errp, -ret, "Failed to load snapshot");
 203         }
 204         return ret;
 205     }
 206
 207     if (bs->file) {
 208         BlockDriverState *file;
 209         QDict *options = qdict_clone_shallow(bs->options);
 210         QDict *file_options;
 211         Error *local_err = NULL;
 212
 213         file = bs->file->bs;
 214         /* Prevent it from getting deleted when detached from bs */
 215         bdrv_ref(file);
 216
 217         qdict_extract_subqdict(options, &file_options, "file.");
 218         qobject_unref(file_options);
 219         qdict_put_str(options, "file", bdrv_get_node_name(file));
 220
 221         if (drv->bdrv_close) {
 222             drv->bdrv_close(bs);
 223         }
 224         bdrv_unref_child(bs, bs->file);
 225         bs->file = NULL;
 226
 227         ret = bdrv_snapshot_goto(file, snapshot_id, errp);
 228         open_ret = drv->bdrv_open(bs, options, bs->open_flags, &local_err);
 229         qobject_unref(options);
 230         if (open_ret < 0) {
 231             bdrv_unref(file);
 232             bs->drv = NULL;
 233             /* A bdrv_snapshot_goto() error takes precedence */
 234             error_propagate(errp, local_err);
 235             return ret < 0 ? ret : open_ret;
 236         }
 237
 238         assert(bs->file->bs == file);
 239         bdrv_unref(file);
 240         return ret;
 241     }
 242
 243     error_setg(errp, "Block driver does not support snapshots");
 244     return -ENOTSUP;
 245 }
 246
 247 /**
 248  * Delete an internal snapshot by @snapshot_id and @name.
 249  * @bs: block device used in the operation
 250  * @snapshot_id: unique snapshot ID, or NULL
 251  * @name: snapshot name, or NULL
 252  * @errp: location to store error
 253  *
 254  * If both @snapshot_id and @name are specified, delete the first one with
 255  * id @snapshot_id and name @name.
 256  * If only @snapshot_id is specified, delete the first one with id
 257  * @snapshot_id.
 258  * If only @name is specified, delete the first one with name @name.
 259  * if none is specified, return -EINVAL.
 260  *
 261  * Returns: 0 on success, -errno on failure. If @bs is not inserted, return
 262  * -ENOMEDIUM. If @snapshot_id and @name are both NULL, return -EINVAL. If @bs
 263  * does not support internal snapshot deletion, return -ENOTSUP. If @bs does
 264  * not support parameter @snapshot_id or @name, or one of them is not correctly
 265  * specified, return -EINVAL. If @bs can't find one matching @id and @name,
 266  * return -ENOENT. If @errp != NULL, it will always be filled with error
 267  * message on failure.
 268  */
 269 int bdrv_snapshot_delete(BlockDriverState *bs,
 270                          const char *snapshot_id,
 271                          const char *name,
 272                          Error **errp)
 273 {
 274     BlockDriver *drv = bs->drv;
 275     int ret;
 276
 277     if (!drv) {
 278         error_setg(errp, QERR_DEVICE_HAS_NO_MEDIUM, bdrv_get_device_name(bs));
 279         return -ENOMEDIUM;
 280     }
 281     if (!snapshot_id && !name) {
 282         error_setg(errp, "snapshot_id and name are both NULL");
 283         return -EINVAL;
 284     }
 285
 286     /* drain all pending i/o before deleting snapshot */
 287     bdrv_drained_begin(bs);
 288
 289     if (drv->bdrv_snapshot_delete) {
 290         ret = drv->bdrv_snapshot_delete(bs, snapshot_id, name, errp);
 291     } else if (bs->file) {
 292         ret = bdrv_snapshot_delete(bs->file->bs, snapshot_id, name, errp);
 293     } else {
 294         error_setg(errp, "Block format '%s' used by device '%s' "
 295                    "does not support internal snapshot deletion",
 296                    drv->format_name, bdrv_get_device_name(bs));
 297         ret = -ENOTSUP;
 298     }
 299
 300     bdrv_drained_end(bs);
 301     return ret;
 302 }
 303
 304 int bdrv_snapshot_list(BlockDriverState *bs,
 305                        QEMUSnapshotInfo **psn_info)
 306 {
 307     BlockDriver *drv = bs->drv;
 308     if (!drv) {
 309         return -ENOMEDIUM;
 310     }
 311     if (drv->bdrv_snapshot_list) {
 312         return drv->bdrv_snapshot_list(bs, psn_info);
 313     }
 314     if (bs->file) {
 315         return bdrv_snapshot_list(bs->file->bs, psn_info);
 316     }
 317     return -ENOTSUP;
 318 }
 319
 320 /**
 321  * Temporarily load 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, load the first one with
 328  * id @snapshot_id and name @name.
 329  * If only @snapshot_id is specified, load the first one with id
 330  * @snapshot_id.
 331  * If only @name is specified, load the first one with name @name.
 332  * if none is specified, return -EINVAL.
 333  *
 334  * Returns: 0 on success, -errno on fail. If @bs is not inserted, return
 335  * -ENOMEDIUM. If @bs is not readonly, return -EINVAL. If @bs did not support
 336  * internal snapshot, return -ENOTSUP. If qemu can't find a matching @id and
 337  * @name, return -ENOENT. If @errp != NULL, it will always be filled on
 338  * failure.
 339  */
 340 int bdrv_snapshot_load_tmp(BlockDriverState *bs,
 341                            const char *snapshot_id,
 342                            const char *name,
 343                            Error **errp)
 344 {
 345     BlockDriver *drv = bs->drv;
 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     if (!bs->read_only) {
 356         error_setg(errp, "Device is not readonly");
 357         return -EINVAL;
 358     }
 359     if (drv->bdrv_snapshot_load_tmp) {
 360         return drv->bdrv_snapshot_load_tmp(bs, snapshot_id, name, errp);
 361     }
 362     error_setg(errp, "Block format '%s' used by device '%s' "
 363                "does not support temporarily loading internal snapshots",
 364                drv->format_name, bdrv_get_device_name(bs));
 365     return -ENOTSUP;
 366 }
 367
 368 int bdrv_snapshot_load_tmp_by_id_or_name(BlockDriverState *bs,
 369                                          const char *id_or_name,
 370                                          Error **errp)
 371 {
 372     int ret;
 373     Error *local_err = NULL;
 374
 375     ret = bdrv_snapshot_load_tmp(bs, id_or_name, NULL, &local_err);
 376     if (ret == -ENOENT || ret == -EINVAL) {
 377         error_free(local_err);
 378         local_err = NULL;
 379         ret = bdrv_snapshot_load_tmp(bs, NULL, id_or_name, &local_err);
 380     }
 381
 382     error_propagate(errp, local_err);
 383
 384     return ret;
 385 }
 386
 387
 388 /* Group operations. All block drivers are involved.
 389  * These functions will properly handle dataplane (take aio_context_acquire
 390  * when appropriate for appropriate block drivers) */
 391
 392 bool bdrv_all_can_snapshot(BlockDriverState **first_bad_bs)
 393 {
 394     bool ok = true;
 395     BlockDriverState *bs;
 396     BdrvNextIterator it;
 397
 398     for (bs = bdrv_first(&it); bs; bs = bdrv_next(&it)) {
 399         AioContext *ctx = bdrv_get_aio_context(bs);
 400
 401         aio_context_acquire(ctx);
 402         if (bdrv_is_inserted(bs) && !bdrv_is_read_only(bs)) {
 403             ok = bdrv_can_snapshot(bs);
 404         }
 405         aio_context_release(ctx);
 406         if (!ok) {
 407             bdrv_next_cleanup(&it);
 408             goto fail;
 409         }
 410     }
 411
 412 fail:
 413     *first_bad_bs = bs;
 414     return ok;
 415 }
 416
 417 int bdrv_all_delete_snapshot(const char *name, BlockDriverState **first_bad_bs,
 418                              Error **err)
 419 {
 420     int ret = 0;
 421     BlockDriverState *bs;
 422     BdrvNextIterator it;
 423     QEMUSnapshotInfo sn1, *snapshot = &sn1;
 424
 425     for (bs = bdrv_first(&it); bs; bs = bdrv_next(&it)) {
 426         AioContext *ctx = bdrv_get_aio_context(bs);
 427
 428         aio_context_acquire(ctx);
 429         if (bdrv_can_snapshot(bs) &&
 430                 bdrv_snapshot_find(bs, snapshot, name) >= 0) {
 431             ret = bdrv_snapshot_delete(bs, snapshot->id_str,
 432                                        snapshot->name, err);
 433         }
 434         aio_context_release(ctx);
 435         if (ret < 0) {
 436             bdrv_next_cleanup(&it);
 437             goto fail;
 438         }
 439     }
 440
 441 fail:
 442     *first_bad_bs = bs;
 443     return ret;
 444 }
 445
 446
 447 int bdrv_all_goto_snapshot(const char *name, BlockDriverState **first_bad_bs,
 448                            Error **errp)
 449 {
 450     int ret = 0;
 451     BlockDriverState *bs;
 452     BdrvNextIterator it;
 453
 454     for (bs = bdrv_first(&it); bs; bs = bdrv_next(&it)) {
 455         AioContext *ctx = bdrv_get_aio_context(bs);
 456
 457         aio_context_acquire(ctx);
 458         if (bdrv_can_snapshot(bs)) {
 459             ret = bdrv_snapshot_goto(bs, name, errp);
 460         }
 461         aio_context_release(ctx);
 462         if (ret < 0) {
 463             bdrv_next_cleanup(&it);
 464             goto fail;
 465         }
 466     }
 467
 468 fail:
 469     *first_bad_bs = bs;
 470     return ret;
 471 }
 472
 473 int bdrv_all_find_snapshot(const char *name, BlockDriverState **first_bad_bs)
 474 {
 475     QEMUSnapshotInfo sn;
 476     int err = 0;
 477     BlockDriverState *bs;
 478     BdrvNextIterator it;
 479
 480     for (bs = bdrv_first(&it); bs; bs = bdrv_next(&it)) {
 481         AioContext *ctx = bdrv_get_aio_context(bs);
 482
 483         aio_context_acquire(ctx);
 484         if (bdrv_can_snapshot(bs)) {
 485             err = bdrv_snapshot_find(bs, &sn, name);
 486         }
 487         aio_context_release(ctx);
 488         if (err < 0) {
 489             bdrv_next_cleanup(&it);
 490             goto fail;
 491         }
 492     }
 493
 494 fail:
 495     *first_bad_bs = bs;
 496     return err;
 497 }
 498
 499 int bdrv_all_create_snapshot(QEMUSnapshotInfo *sn,
 500                              BlockDriverState *vm_state_bs,
 501                              uint64_t vm_state_size,
 502                              BlockDriverState **first_bad_bs)
 503 {
 504     int err = 0;
 505     BlockDriverState *bs;
 506     BdrvNextIterator it;
 507
 508     for (bs = bdrv_first(&it); bs; bs = bdrv_next(&it)) {
 509         AioContext *ctx = bdrv_get_aio_context(bs);
 510
 511         aio_context_acquire(ctx);
 512         if (bs == vm_state_bs) {
 513             sn->vm_state_size = vm_state_size;
 514             err = bdrv_snapshot_create(bs, sn);
 515         } else if (bdrv_can_snapshot(bs)) {
 516             sn->vm_state_size = 0;
 517             err = bdrv_snapshot_create(bs, sn);
 518         }
 519         aio_context_release(ctx);
 520         if (err < 0) {
 521             bdrv_next_cleanup(&it);
 522             goto fail;
 523         }
 524     }
 525
 526 fail:
 527     *first_bad_bs = bs;
 528     return err;
 529 }
 530
 531 BlockDriverState *bdrv_all_find_vmstate_bs(void)
 532 {
 533     BlockDriverState *bs;
 534     BdrvNextIterator it;
 535
 536     for (bs = bdrv_first(&it); bs; bs = bdrv_next(&it)) {
 537         AioContext *ctx = bdrv_get_aio_context(bs);
 538         bool found;
 539
 540         aio_context_acquire(ctx);
 541         found = bdrv_can_snapshot(bs);
 542         aio_context_release(ctx);
 543
 544         if (found) {
 545             bdrv_next_cleanup(&it);
 546             break;
 547         }
 548     }
 549     return bs;
 550 }