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 "block/snapshot.h"
  26 #include "block/block_int.h"
  27 #include "qapi/qmp/qerror.h"
  28
  29 QemuOptsList internal_snapshot_opts = {
  30     .name = "snapshot",
  31     .head = QTAILQ_HEAD_INITIALIZER(internal_snapshot_opts.head),
  32     .desc = {
  33         {
  34             .name = SNAPSHOT_OPT_ID,
  35             .type = QEMU_OPT_STRING,
  36             .help = "snapshot id"
  37         },{
  38             .name = SNAPSHOT_OPT_NAME,
  39             .type = QEMU_OPT_STRING,
  40             .help = "snapshot name"
  41         },{
  42             /* end of list */
  43         }
  44     },
  45 };
  46
  47 int bdrv_snapshot_find(BlockDriverState *bs, QEMUSnapshotInfo *sn_info,
  48                        const char *name)
  49 {
  50     QEMUSnapshotInfo *sn_tab, *sn;
  51     int nb_sns, i, ret;
  52
  53     ret = -ENOENT;
  54     nb_sns = bdrv_snapshot_list(bs, &sn_tab);
  55     if (nb_sns < 0) {
  56         return ret;
  57     }
  58     for (i = 0; i < nb_sns; i++) {
  59         sn = &sn_tab[i];
  60         if (!strcmp(sn->id_str, name) || !strcmp(sn->name, name)) {
  61             *sn_info = *sn;
  62             ret = 0;
  63             break;
  64         }
  65     }
  66     g_free(sn_tab);
  67     return ret;
  68 }
  69
  70 /**
  71  * Look up an internal snapshot by @id and @name.
  72  * @bs: block device to search
  73  * @id: unique snapshot ID, or NULL
  74  * @name: snapshot name, or NULL
  75  * @sn_info: location to store information on the snapshot found
  76  * @errp: location to store error, will be set only for exception
  77  *
  78  * This function will traverse snapshot list in @bs to search the matching
  79  * one, @id and @name are the matching condition:
  80  * If both @id and @name are specified, find the first one with id @id and
  81  * name @name.
  82  * If only @id is specified, find the first one with id @id.
  83  * If only @name is specified, find the first one with name @name.
  84  * if none is specified, abort().
  85  *
  86  * Returns: true when a snapshot is found and @sn_info will be filled, false
  87  * when error or not found. If all operation succeed but no matching one is
  88  * found, @errp will NOT be set.
  89  */
  90 bool bdrv_snapshot_find_by_id_and_name(BlockDriverState *bs,
  91                                        const char *id,
  92                                        const char *name,
  93                                        QEMUSnapshotInfo *sn_info,
  94                                        Error **errp)
  95 {
  96     QEMUSnapshotInfo *sn_tab, *sn;
  97     int nb_sns, i;
  98     bool ret = false;
  99
 100     assert(id || name);
 101
 102     nb_sns = bdrv_snapshot_list(bs, &sn_tab);
 103     if (nb_sns < 0) {
 104         error_setg_errno(errp, -nb_sns, "Failed to get a snapshot list");
 105         return false;
 106     } else if (nb_sns == 0) {
 107         return false;
 108     }
 109
 110     if (id && name) {
 111         for (i = 0; i < nb_sns; i++) {
 112             sn = &sn_tab[i];
 113             if (!strcmp(sn->id_str, id) && !strcmp(sn->name, name)) {
 114                 *sn_info = *sn;
 115                 ret = true;
 116                 break;
 117             }
 118         }
 119     } else if (id) {
 120         for (i = 0; i < nb_sns; i++) {
 121             sn = &sn_tab[i];
 122             if (!strcmp(sn->id_str, id)) {
 123                 *sn_info = *sn;
 124                 ret = true;
 125                 break;
 126             }
 127         }
 128     } else if (name) {
 129         for (i = 0; i < nb_sns; i++) {
 130             sn = &sn_tab[i];
 131             if (!strcmp(sn->name, name)) {
 132                 *sn_info = *sn;
 133                 ret = true;
 134                 break;
 135             }
 136         }
 137     }
 138
 139     g_free(sn_tab);
 140     return ret;
 141 }
 142
 143 int bdrv_can_snapshot(BlockDriverState *bs)
 144 {
 145     BlockDriver *drv = bs->drv;
 146     if (!drv || !bdrv_is_inserted(bs) || bdrv_is_read_only(bs)) {
 147         return 0;
 148     }
 149
 150     if (!drv->bdrv_snapshot_create) {
 151         if (bs->file != NULL) {
 152             return bdrv_can_snapshot(bs->file->bs);
 153         }
 154         return 0;
 155     }
 156
 157     return 1;
 158 }
 159
 160 int bdrv_snapshot_create(BlockDriverState *bs,
 161                          QEMUSnapshotInfo *sn_info)
 162 {
 163     BlockDriver *drv = bs->drv;
 164     if (!drv) {
 165         return -ENOMEDIUM;
 166     }
 167     if (drv->bdrv_snapshot_create) {
 168         return drv->bdrv_snapshot_create(bs, sn_info);
 169     }
 170     if (bs->file) {
 171         return bdrv_snapshot_create(bs->file->bs, sn_info);
 172     }
 173     return -ENOTSUP;
 174 }
 175
 176 int bdrv_snapshot_goto(BlockDriverState *bs,
 177                        const char *snapshot_id)
 178 {
 179     BlockDriver *drv = bs->drv;
 180     int ret, open_ret;
 181
 182     if (!drv) {
 183         return -ENOMEDIUM;
 184     }
 185     if (drv->bdrv_snapshot_goto) {
 186         return drv->bdrv_snapshot_goto(bs, snapshot_id);
 187     }
 188
 189     if (bs->file) {
 190         drv->bdrv_close(bs);
 191         ret = bdrv_snapshot_goto(bs->file->bs, snapshot_id);
 192         open_ret = drv->bdrv_open(bs, NULL, bs->open_flags, NULL);
 193         if (open_ret < 0) {
 194             bdrv_unref(bs->file->bs);
 195             bs->drv = NULL;
 196             return open_ret;
 197         }
 198         return ret;
 199     }
 200
 201     return -ENOTSUP;
 202 }
 203
 204 /**
 205  * Delete an internal snapshot by @snapshot_id and @name.
 206  * @bs: block device used in the operation
 207  * @snapshot_id: unique snapshot ID, or NULL
 208  * @name: snapshot name, or NULL
 209  * @errp: location to store error
 210  *
 211  * If both @snapshot_id and @name are specified, delete the first one with
 212  * id @snapshot_id and name @name.
 213  * If only @snapshot_id is specified, delete the first one with id
 214  * @snapshot_id.
 215  * If only @name is specified, delete the first one with name @name.
 216  * if none is specified, return -EINVAL.
 217  *
 218  * Returns: 0 on success, -errno on failure. If @bs is not inserted, return
 219  * -ENOMEDIUM. If @snapshot_id and @name are both NULL, return -EINVAL. If @bs
 220  * does not support internal snapshot deletion, return -ENOTSUP. If @bs does
 221  * not support parameter @snapshot_id or @name, or one of them is not correctly
 222  * specified, return -EINVAL. If @bs can't find one matching @id and @name,
 223  * return -ENOENT. If @errp != NULL, it will always be filled with error
 224  * message on failure.
 225  */
 226 int bdrv_snapshot_delete(BlockDriverState *bs,
 227                          const char *snapshot_id,
 228                          const char *name,
 229                          Error **errp)
 230 {
 231     BlockDriver *drv = bs->drv;
 232     if (!drv) {
 233         error_setg(errp, QERR_DEVICE_HAS_NO_MEDIUM, bdrv_get_device_name(bs));
 234         return -ENOMEDIUM;
 235     }
 236     if (!snapshot_id && !name) {
 237         error_setg(errp, "snapshot_id and name are both NULL");
 238         return -EINVAL;
 239     }
 240
 241     /* drain all pending i/o before deleting snapshot */
 242     bdrv_drain(bs);
 243
 244     if (drv->bdrv_snapshot_delete) {
 245         return drv->bdrv_snapshot_delete(bs, snapshot_id, name, errp);
 246     }
 247     if (bs->file) {
 248         return bdrv_snapshot_delete(bs->file->bs, snapshot_id, name, errp);
 249     }
 250     error_setg(errp, "Block format '%s' used by device '%s' "
 251                "does not support internal snapshot deletion",
 252                drv->format_name, bdrv_get_device_name(bs));
 253     return -ENOTSUP;
 254 }
 255
 256 int bdrv_snapshot_delete_by_id_or_name(BlockDriverState *bs,
 257                                        const char *id_or_name,
 258                                        Error **errp)
 259 {
 260     int ret;
 261     Error *local_err = NULL;
 262
 263     ret = bdrv_snapshot_delete(bs, id_or_name, NULL, &local_err);
 264     if (ret == -ENOENT || ret == -EINVAL) {
 265         error_free(local_err);
 266         local_err = NULL;
 267         ret = bdrv_snapshot_delete(bs, NULL, id_or_name, &local_err);
 268     }
 269
 270     if (ret < 0) {
 271         error_propagate(errp, local_err);
 272     }
 273     return ret;
 274 }
 275
 276 int bdrv_snapshot_list(BlockDriverState *bs,
 277                        QEMUSnapshotInfo **psn_info)
 278 {
 279     BlockDriver *drv = bs->drv;
 280     if (!drv) {
 281         return -ENOMEDIUM;
 282     }
 283     if (drv->bdrv_snapshot_list) {
 284         return drv->bdrv_snapshot_list(bs, psn_info);
 285     }
 286     if (bs->file) {
 287         return bdrv_snapshot_list(bs->file->bs, psn_info);
 288     }
 289     return -ENOTSUP;
 290 }
 291
 292 /**
 293  * Temporarily load an internal snapshot by @snapshot_id and @name.
 294  * @bs: block device used in the operation
 295  * @snapshot_id: unique snapshot ID, or NULL
 296  * @name: snapshot name, or NULL
 297  * @errp: location to store error
 298  *
 299  * If both @snapshot_id and @name are specified, load the first one with
 300  * id @snapshot_id and name @name.
 301  * If only @snapshot_id is specified, load the first one with id
 302  * @snapshot_id.
 303  * If only @name is specified, load the first one with name @name.
 304  * if none is specified, return -EINVAL.
 305  *
 306  * Returns: 0 on success, -errno on fail. If @bs is not inserted, return
 307  * -ENOMEDIUM. If @bs is not readonly, return -EINVAL. If @bs did not support
 308  * internal snapshot, return -ENOTSUP. If qemu can't find a matching @id and
 309  * @name, return -ENOENT. If @errp != NULL, it will always be filled on
 310  * failure.
 311  */
 312 int bdrv_snapshot_load_tmp(BlockDriverState *bs,
 313                            const char *snapshot_id,
 314                            const char *name,
 315                            Error **errp)
 316 {
 317     BlockDriver *drv = bs->drv;
 318
 319     if (!drv) {
 320         error_setg(errp, QERR_DEVICE_HAS_NO_MEDIUM, bdrv_get_device_name(bs));
 321         return -ENOMEDIUM;
 322     }
 323     if (!snapshot_id && !name) {
 324         error_setg(errp, "snapshot_id and name are both NULL");
 325         return -EINVAL;
 326     }
 327     if (!bs->read_only) {
 328         error_setg(errp, "Device is not readonly");
 329         return -EINVAL;
 330     }
 331     if (drv->bdrv_snapshot_load_tmp) {
 332         return drv->bdrv_snapshot_load_tmp(bs, snapshot_id, name, errp);
 333     }
 334     error_setg(errp, "Block format '%s' used by device '%s' "
 335                "does not support temporarily loading internal snapshots",
 336                drv->format_name, bdrv_get_device_name(bs));
 337     return -ENOTSUP;
 338 }
 339
 340 int bdrv_snapshot_load_tmp_by_id_or_name(BlockDriverState *bs,
 341                                          const char *id_or_name,
 342                                          Error **errp)
 343 {
 344     int ret;
 345     Error *local_err = NULL;
 346
 347     ret = bdrv_snapshot_load_tmp(bs, id_or_name, NULL, &local_err);
 348     if (ret == -ENOENT || ret == -EINVAL) {
 349         error_free(local_err);
 350         local_err = NULL;
 351         ret = bdrv_snapshot_load_tmp(bs, NULL, id_or_name, &local_err);
 352     }
 353
 354     if (local_err) {
 355         error_propagate(errp, local_err);
 356     }
 357
 358     return ret;
 359 }
 360
 361
 362 /* Group operations. All block drivers are involved.
 363  * These functions will properly handle dataplane (take aio_context_acquire
 364  * when appropriate for appropriate block drivers) */
 365
 366 bool bdrv_all_can_snapshot(BlockDriverState **first_bad_bs)
 367 {
 368     bool ok = true;
 369     BlockDriverState *bs = NULL;
 370
 371     while (ok && (bs = bdrv_next(bs))) {
 372         AioContext *ctx = bdrv_get_aio_context(bs);
 373
 374         aio_context_acquire(ctx);
 375         if (bdrv_is_inserted(bs) && !bdrv_is_read_only(bs)) {
 376             ok = bdrv_can_snapshot(bs);
 377         }
 378         aio_context_release(ctx);
 379     }
 380
 381     *first_bad_bs = bs;
 382     return ok;
 383 }