qemu

snapshot.c (22791B)

---

 /*
  * Block layer snapshot related functions
  *
  * Copyright (c) 2003-2008 Fabrice Bellard
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy
  * of this software and associated documentation files (the "Software"), to deal
  * in the Software without restriction, including without limitation the rights
  * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  * copies of the Software, and to permit persons to whom the Software is
  * furnished to do so, subject to the following conditions:
  *
  * The above copyright notice and this permission notice shall be included in
  * all copies or substantial portions of the Software.
  *
  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
  * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
  * THE SOFTWARE.
  */
 
 #include "qemu/osdep.h"
 #include "block/snapshot.h"
 #include "block/block_int.h"
 #include "block/qdict.h"
 #include "qapi/error.h"
 #include "qapi/qmp/qdict.h"
 #include "qapi/qmp/qerror.h"
 #include "qapi/qmp/qstring.h"
 #include "qemu/option.h"
 #include "sysemu/block-backend.h"
 
 QemuOptsList internal_snapshot_opts = {
     .name = "snapshot",
     .head = QTAILQ_HEAD_INITIALIZER(internal_snapshot_opts.head),
     .desc = {
         {
             .name = SNAPSHOT_OPT_ID,
             .type = QEMU_OPT_STRING,
             .help = "snapshot id"
         },{
             .name = SNAPSHOT_OPT_NAME,
             .type = QEMU_OPT_STRING,
             .help = "snapshot name"
         },{
             /* end of list */
         }
     },
 };
 
 int bdrv_snapshot_find(BlockDriverState *bs, QEMUSnapshotInfo *sn_info,
                        const char *name)
 {
     QEMUSnapshotInfo *sn_tab, *sn;
     int nb_sns, i, ret;
 
     GLOBAL_STATE_CODE();
 
     ret = -ENOENT;
     nb_sns = bdrv_snapshot_list(bs, &sn_tab);
     if (nb_sns < 0) {
         return ret;
     }
     for (i = 0; i < nb_sns; i++) {
         sn = &sn_tab[i];
         if (!strcmp(sn->name, name)) {
             *sn_info = *sn;
             ret = 0;
             break;
         }
     }
     g_free(sn_tab);
     return ret;
 }
 
 /**
  * Look up an internal snapshot by @id and @name.
  * @bs: block device to search
  * @id: unique snapshot ID, or NULL
  * @name: snapshot name, or NULL
  * @sn_info: location to store information on the snapshot found
  * @errp: location to store error, will be set only for exception
  *
  * This function will traverse snapshot list in @bs to search the matching
  * one, @id and @name are the matching condition:
  * If both @id and @name are specified, find the first one with id @id and
  * name @name.
  * If only @id is specified, find the first one with id @id.
  * If only @name is specified, find the first one with name @name.
  * if none is specified, abort().
  *
  * Returns: true when a snapshot is found and @sn_info will be filled, false
  * when error or not found. If all operation succeed but no matching one is
  * found, @errp will NOT be set.
  */
 bool bdrv_snapshot_find_by_id_and_name(BlockDriverState *bs,
                                        const char *id,
                                        const char *name,
                                        QEMUSnapshotInfo *sn_info,
                                        Error **errp)
 {
     QEMUSnapshotInfo *sn_tab, *sn;
     int nb_sns, i;
     bool ret = false;
 
     assert(id || name);
     GLOBAL_STATE_CODE();
 
     nb_sns = bdrv_snapshot_list(bs, &sn_tab);
     if (nb_sns < 0) {
         error_setg_errno(errp, -nb_sns, "Failed to get a snapshot list");
         return false;
     } else if (nb_sns == 0) {
         return false;
     }
 
     if (id && name) {
         for (i = 0; i < nb_sns; i++) {
             sn = &sn_tab[i];
             if (!strcmp(sn->id_str, id) && !strcmp(sn->name, name)) {
                 *sn_info = *sn;
                 ret = true;
                 break;
             }
         }
     } else if (id) {
         for (i = 0; i < nb_sns; i++) {
             sn = &sn_tab[i];
             if (!strcmp(sn->id_str, id)) {
                 *sn_info = *sn;
                 ret = true;
                 break;
             }
         }
     } else if (name) {
         for (i = 0; i < nb_sns; i++) {
             sn = &sn_tab[i];
             if (!strcmp(sn->name, name)) {
                 *sn_info = *sn;
                 ret = true;
                 break;
             }
         }
     }
 
     g_free(sn_tab);
     return ret;
 }
 
 /**
  * Return a pointer to child of given BDS to which we can fall
  * back if the given BDS does not support snapshots.
  * Return NULL if there is no BDS to (safely) fall back to.
  */
 static BdrvChild *bdrv_snapshot_fallback_child(BlockDriverState *bs)
 {
     BdrvChild *fallback = bdrv_primary_child(bs);
     BdrvChild *child;
 
     /* We allow fallback only to primary child */
     if (!fallback) {
         return NULL;
     }
 
     /*
      * Check that there are no other children that would need to be
      * snapshotted.  If there are, it is not safe to fall back to
      * fallback.
      */
     QLIST_FOREACH(child, &bs->children, next) {
         if (child->role & (BDRV_CHILD_DATA | BDRV_CHILD_METADATA |
                            BDRV_CHILD_FILTERED) &&
             child != fallback)
         {
             return NULL;
         }
     }
 
     return fallback;
 }
 
 static BlockDriverState *bdrv_snapshot_fallback(BlockDriverState *bs)
 {
     return child_bs(bdrv_snapshot_fallback_child(bs));
 }
 
 int bdrv_can_snapshot(BlockDriverState *bs)
 {
     BlockDriver *drv = bs->drv;
     GLOBAL_STATE_CODE();
     if (!drv || !bdrv_is_inserted(bs) || bdrv_is_read_only(bs)) {
         return 0;
     }
 
     if (!drv->bdrv_snapshot_create) {
         BlockDriverState *fallback_bs = bdrv_snapshot_fallback(bs);
         if (fallback_bs) {
             return bdrv_can_snapshot(fallback_bs);
         }
         return 0;
     }
 
     return 1;
 }
 
 int bdrv_snapshot_create(BlockDriverState *bs,
                          QEMUSnapshotInfo *sn_info)
 {
     BlockDriver *drv = bs->drv;
     BlockDriverState *fallback_bs = bdrv_snapshot_fallback(bs);
 
     GLOBAL_STATE_CODE();
 
     if (!drv) {
         return -ENOMEDIUM;
     }
     if (drv->bdrv_snapshot_create) {
         return drv->bdrv_snapshot_create(bs, sn_info);
     }
     if (fallback_bs) {
         return bdrv_snapshot_create(fallback_bs, sn_info);
     }
     return -ENOTSUP;
 }
 
 int bdrv_snapshot_goto(BlockDriverState *bs,
                        const char *snapshot_id,
                        Error **errp)
 {
     BlockDriver *drv = bs->drv;
     BdrvChild *fallback;
     int ret, open_ret;
 
     GLOBAL_STATE_CODE();
 
     if (!drv) {
         error_setg(errp, "Block driver is closed");
         return -ENOMEDIUM;
     }
 
     if (!QLIST_EMPTY(&bs->dirty_bitmaps)) {
         error_setg(errp, "Device has active dirty bitmaps");
         return -EBUSY;
     }
 
     if (drv->bdrv_snapshot_goto) {
         ret = drv->bdrv_snapshot_goto(bs, snapshot_id);
         if (ret < 0) {
             error_setg_errno(errp, -ret, "Failed to load snapshot");
         }
         return ret;
     }
 
     fallback = bdrv_snapshot_fallback_child(bs);
     if (fallback) {
         QDict *options;
         QDict *file_options;
         Error *local_err = NULL;
         BlockDriverState *fallback_bs = fallback->bs;
         char *subqdict_prefix = g_strdup_printf("%s.", fallback->name);
 
         options = qdict_clone_shallow(bs->options);
 
         /* Prevent it from getting deleted when detached from bs */
         bdrv_ref(fallback_bs);
 
         qdict_extract_subqdict(options, &file_options, subqdict_prefix);
         qobject_unref(file_options);
         g_free(subqdict_prefix);
 
         /* Force .bdrv_open() below to re-attach fallback_bs on fallback */
         qdict_put_str(options, fallback->name,
                       bdrv_get_node_name(fallback_bs));
 
         /* Now close bs, apply the snapshot on fallback_bs, and re-open bs */
         if (drv->bdrv_close) {
             drv->bdrv_close(bs);
         }
 
         /* .bdrv_open() will re-attach it */
         bdrv_unref_child(bs, fallback);
 
         ret = bdrv_snapshot_goto(fallback_bs, snapshot_id, errp);
         open_ret = drv->bdrv_open(bs, options, bs->open_flags, &local_err);
         qobject_unref(options);
         if (open_ret < 0) {
             bdrv_unref(fallback_bs);
             bs->drv = NULL;
             /* A bdrv_snapshot_goto() error takes precedence */
             error_propagate(errp, local_err);
             return ret < 0 ? ret : open_ret;
         }
 
         /*
          * fallback was a primary child. It was closed above and set to NULL,
          * but the .bdrv_open() call has opened it again, because we set the
          * respective option (with the qdict_put_str() call above).
          * Assert that .bdrv_open() has attached the right BDS as primary child.
          */
         assert(bdrv_primary_bs(bs) == fallback_bs);
         bdrv_unref(fallback_bs);
         return ret;
     }
 
     error_setg(errp, "Block driver does not support snapshots");
     return -ENOTSUP;
 }
 
 /**
  * Delete an internal snapshot by @snapshot_id and @name.
  * @bs: block device used in the operation
  * @snapshot_id: unique snapshot ID, or NULL
  * @name: snapshot name, or NULL
  * @errp: location to store error
  *
  * If both @snapshot_id and @name are specified, delete the first one with
  * id @snapshot_id and name @name.
  * If only @snapshot_id is specified, delete the first one with id
  * @snapshot_id.
  * If only @name is specified, delete the first one with name @name.
  * if none is specified, return -EINVAL.
  *
  * Returns: 0 on success, -errno on failure. If @bs is not inserted, return
  * -ENOMEDIUM. If @snapshot_id and @name are both NULL, return -EINVAL. If @bs
  * does not support internal snapshot deletion, return -ENOTSUP. If @bs does
  * not support parameter @snapshot_id or @name, or one of them is not correctly
  * specified, return -EINVAL. If @bs can't find one matching @id and @name,
  * return -ENOENT. If @errp != NULL, it will always be filled with error
  * message on failure.
  */
 int bdrv_snapshot_delete(BlockDriverState *bs,
                          const char *snapshot_id,
                          const char *name,
                          Error **errp)
 {
     BlockDriver *drv = bs->drv;
     BlockDriverState *fallback_bs = bdrv_snapshot_fallback(bs);
     int ret;
 
     GLOBAL_STATE_CODE();
 
     if (!drv) {
         error_setg(errp, QERR_DEVICE_HAS_NO_MEDIUM, bdrv_get_device_name(bs));
         return -ENOMEDIUM;
     }
     if (!snapshot_id && !name) {
         error_setg(errp, "snapshot_id and name are both NULL");
         return -EINVAL;
     }
 
     /* drain all pending i/o before deleting snapshot */
     bdrv_drained_begin(bs);
 
     if (drv->bdrv_snapshot_delete) {
         ret = drv->bdrv_snapshot_delete(bs, snapshot_id, name, errp);
     } else if (fallback_bs) {
         ret = bdrv_snapshot_delete(fallback_bs, snapshot_id, name, errp);
     } else {
         error_setg(errp, "Block format '%s' used by device '%s' "
                    "does not support internal snapshot deletion",
                    drv->format_name, bdrv_get_device_name(bs));
         ret = -ENOTSUP;
     }
 
     bdrv_drained_end(bs);
     return ret;
 }
 
 int bdrv_snapshot_list(BlockDriverState *bs,
                        QEMUSnapshotInfo **psn_info)
 {
     BlockDriver *drv = bs->drv;
     BlockDriverState *fallback_bs = bdrv_snapshot_fallback(bs);
 
     GLOBAL_STATE_CODE();
     if (!drv) {
         return -ENOMEDIUM;
     }
     if (drv->bdrv_snapshot_list) {
         return drv->bdrv_snapshot_list(bs, psn_info);
     }
     if (fallback_bs) {
         return bdrv_snapshot_list(fallback_bs, psn_info);
     }
     return -ENOTSUP;
 }
 
 /**
  * Temporarily load an internal snapshot by @snapshot_id and @name.
  * @bs: block device used in the operation
  * @snapshot_id: unique snapshot ID, or NULL
  * @name: snapshot name, or NULL
  * @errp: location to store error
  *
  * If both @snapshot_id and @name are specified, load the first one with
  * id @snapshot_id and name @name.
  * If only @snapshot_id is specified, load the first one with id
  * @snapshot_id.
  * If only @name is specified, load the first one with name @name.
  * if none is specified, return -EINVAL.
  *
  * Returns: 0 on success, -errno on fail. If @bs is not inserted, return
  * -ENOMEDIUM. If @bs is not readonly, return -EINVAL. If @bs did not support
  * internal snapshot, return -ENOTSUP. If qemu can't find a matching @id and
  * @name, return -ENOENT. If @errp != NULL, it will always be filled on
  * failure.
  */
 int bdrv_snapshot_load_tmp(BlockDriverState *bs,
                            const char *snapshot_id,
                            const char *name,
                            Error **errp)
 {
     BlockDriver *drv = bs->drv;
 
     GLOBAL_STATE_CODE();
 
     if (!drv) {
         error_setg(errp, QERR_DEVICE_HAS_NO_MEDIUM, bdrv_get_device_name(bs));
         return -ENOMEDIUM;
     }
     if (!snapshot_id && !name) {
         error_setg(errp, "snapshot_id and name are both NULL");
         return -EINVAL;
     }
     if (!bdrv_is_read_only(bs)) {
         error_setg(errp, "Device is not readonly");
         return -EINVAL;
     }
     if (drv->bdrv_snapshot_load_tmp) {
         return drv->bdrv_snapshot_load_tmp(bs, snapshot_id, name, errp);
     }
     error_setg(errp, "Block format '%s' used by device '%s' "
                "does not support temporarily loading internal snapshots",
                drv->format_name, bdrv_get_device_name(bs));
     return -ENOTSUP;
 }
 
 int bdrv_snapshot_load_tmp_by_id_or_name(BlockDriverState *bs,
                                          const char *id_or_name,
                                          Error **errp)
 {
     int ret;
     Error *local_err = NULL;
 
     GLOBAL_STATE_CODE();
 
     ret = bdrv_snapshot_load_tmp(bs, id_or_name, NULL, &local_err);
     if (ret == -ENOENT || ret == -EINVAL) {
         error_free(local_err);
         local_err = NULL;
         ret = bdrv_snapshot_load_tmp(bs, NULL, id_or_name, &local_err);
     }
 
     error_propagate(errp, local_err);
 
     return ret;
 }
 
 
 static int bdrv_all_get_snapshot_devices(bool has_devices, strList *devices,
                                          GList **all_bdrvs,
                                          Error **errp)
 {
     g_autoptr(GList) bdrvs = NULL;
 
     if (has_devices) {
         if (!devices) {
             error_setg(errp, "At least one device is required for snapshot");
             return -1;
         }
 
         while (devices) {
             BlockDriverState *bs = bdrv_find_node(devices->value);
             if (!bs) {
                 error_setg(errp, "No block device node '%s'", devices->value);
                 return -1;
             }
             bdrvs = g_list_append(bdrvs, bs);
             devices = devices->next;
         }
     } else {
         BlockDriverState *bs;
         BdrvNextIterator it;
         for (bs = bdrv_first(&it); bs; bs = bdrv_next(&it)) {
             bdrvs = g_list_append(bdrvs, bs);
         }
     }
 
     *all_bdrvs = g_steal_pointer(&bdrvs);
     return 0;
 }
 
 
 static bool bdrv_all_snapshots_includes_bs(BlockDriverState *bs)
 {
     if (!bdrv_is_inserted(bs) || bdrv_is_read_only(bs)) {
         return false;
     }
 
     /* Include all nodes that are either in use by a BlockBackend, or that
      * aren't attached to any node, but owned by the monitor. */
     return bdrv_has_blk(bs) || QLIST_EMPTY(&bs->parents);
 }
 
 /* Group operations. All block drivers are involved.
  * These functions will properly handle dataplane (take aio_context_acquire
  * when appropriate for appropriate block drivers) */
 
 bool bdrv_all_can_snapshot(bool has_devices, strList *devices,
                            Error **errp)
 {
     g_autoptr(GList) bdrvs = NULL;
     GList *iterbdrvs;
 
     GLOBAL_STATE_CODE();
 
     if (bdrv_all_get_snapshot_devices(has_devices, devices, &bdrvs, errp) < 0) {
         return false;
     }
 
     iterbdrvs = bdrvs;
     while (iterbdrvs) {
         BlockDriverState *bs = iterbdrvs->data;
         AioContext *ctx = bdrv_get_aio_context(bs);
         bool ok = true;
 
         aio_context_acquire(ctx);
         if (devices || bdrv_all_snapshots_includes_bs(bs)) {
             ok = bdrv_can_snapshot(bs);
         }
         aio_context_release(ctx);
         if (!ok) {
             error_setg(errp, "Device '%s' is writable but does not support "
                        "snapshots", bdrv_get_device_or_node_name(bs));
             return false;
         }
 
         iterbdrvs = iterbdrvs->next;
     }
 
     return true;
 }
 
 int bdrv_all_delete_snapshot(const char *name,
                              bool has_devices, strList *devices,
                              Error **errp)
 {
     g_autoptr(GList) bdrvs = NULL;
     GList *iterbdrvs;
 
     GLOBAL_STATE_CODE();
 
     if (bdrv_all_get_snapshot_devices(has_devices, devices, &bdrvs, errp) < 0) {
         return -1;
     }
 
     iterbdrvs = bdrvs;
     while (iterbdrvs) {
         BlockDriverState *bs = iterbdrvs->data;
         AioContext *ctx = bdrv_get_aio_context(bs);
         QEMUSnapshotInfo sn1, *snapshot = &sn1;
         int ret = 0;
 
         aio_context_acquire(ctx);
         if ((devices || bdrv_all_snapshots_includes_bs(bs)) &&
             bdrv_snapshot_find(bs, snapshot, name) >= 0)
         {
             ret = bdrv_snapshot_delete(bs, snapshot->id_str,
                                        snapshot->name, errp);
         }
         aio_context_release(ctx);
         if (ret < 0) {
             error_prepend(errp, "Could not delete snapshot '%s' on '%s': ",
                           name, bdrv_get_device_or_node_name(bs));
             return -1;
         }
 
         iterbdrvs = iterbdrvs->next;
     }
 
     return 0;
 }
 
 
 int bdrv_all_goto_snapshot(const char *name,
                            bool has_devices, strList *devices,
                            Error **errp)
 {
     g_autoptr(GList) bdrvs = NULL;
     GList *iterbdrvs;
 
     GLOBAL_STATE_CODE();
 
     if (bdrv_all_get_snapshot_devices(has_devices, devices, &bdrvs, errp) < 0) {
         return -1;
     }
 
     iterbdrvs = bdrvs;
     while (iterbdrvs) {
         BlockDriverState *bs = iterbdrvs->data;
         AioContext *ctx = bdrv_get_aio_context(bs);
         int ret = 0;
 
         aio_context_acquire(ctx);
         if (devices || bdrv_all_snapshots_includes_bs(bs)) {
             ret = bdrv_snapshot_goto(bs, name, errp);
         }
         aio_context_release(ctx);
         if (ret < 0) {
             error_prepend(errp, "Could not load snapshot '%s' on '%s': ",
                           name, bdrv_get_device_or_node_name(bs));
             return -1;
         }
 
         iterbdrvs = iterbdrvs->next;
     }
 
     return 0;
 }
 
 int bdrv_all_has_snapshot(const char *name,
                           bool has_devices, strList *devices,
                           Error **errp)
 {
     g_autoptr(GList) bdrvs = NULL;
     GList *iterbdrvs;
 
     GLOBAL_STATE_CODE();
 
     if (bdrv_all_get_snapshot_devices(has_devices, devices, &bdrvs, errp) < 0) {
         return -1;
     }
 
     iterbdrvs = bdrvs;
     while (iterbdrvs) {
         BlockDriverState *bs = iterbdrvs->data;
         AioContext *ctx = bdrv_get_aio_context(bs);
         QEMUSnapshotInfo sn;
         int ret = 0;
 
         aio_context_acquire(ctx);
         if (devices || bdrv_all_snapshots_includes_bs(bs)) {
             ret = bdrv_snapshot_find(bs, &sn, name);
         }
         aio_context_release(ctx);
         if (ret < 0) {
             if (ret == -ENOENT) {
                 return 0;
             } else {
                 error_setg_errno(errp, errno,
                                  "Could not check snapshot '%s' on '%s'",
                                  name, bdrv_get_device_or_node_name(bs));
                 return -1;
             }
         }
 
         iterbdrvs = iterbdrvs->next;
     }
 
     return 1;
 }
 
 int bdrv_all_create_snapshot(QEMUSnapshotInfo *sn,
                              BlockDriverState *vm_state_bs,
                              uint64_t vm_state_size,
                              bool has_devices, strList *devices,
                              Error **errp)
 {
     g_autoptr(GList) bdrvs = NULL;
     GList *iterbdrvs;
     GLOBAL_STATE_CODE();
 
     if (bdrv_all_get_snapshot_devices(has_devices, devices, &bdrvs, errp) < 0) {
         return -1;
     }
 
     iterbdrvs = bdrvs;
     while (iterbdrvs) {
         BlockDriverState *bs = iterbdrvs->data;
         AioContext *ctx = bdrv_get_aio_context(bs);
         int ret = 0;
 
         aio_context_acquire(ctx);
         if (bs == vm_state_bs) {
             sn->vm_state_size = vm_state_size;
             ret = bdrv_snapshot_create(bs, sn);
         } else if (devices || bdrv_all_snapshots_includes_bs(bs)) {
             sn->vm_state_size = 0;
             ret = bdrv_snapshot_create(bs, sn);
         }
         aio_context_release(ctx);
         if (ret < 0) {
             error_setg(errp, "Could not create snapshot '%s' on '%s'",
                        sn->name, bdrv_get_device_or_node_name(bs));
             return -1;
         }
 
         iterbdrvs = iterbdrvs->next;
     }
 
     return 0;
 }
 
 
 BlockDriverState *bdrv_all_find_vmstate_bs(const char *vmstate_bs,
                                            bool has_devices, strList *devices,
                                            Error **errp)
 {
     g_autoptr(GList) bdrvs = NULL;
     GList *iterbdrvs;
 
     GLOBAL_STATE_CODE();
 
     if (bdrv_all_get_snapshot_devices(has_devices, devices, &bdrvs, errp) < 0) {
         return NULL;
     }
 
     iterbdrvs = bdrvs;
     while (iterbdrvs) {
         BlockDriverState *bs = iterbdrvs->data;
         AioContext *ctx = bdrv_get_aio_context(bs);
         bool found = false;
 
         aio_context_acquire(ctx);
         found = (devices || bdrv_all_snapshots_includes_bs(bs)) &&
             bdrv_can_snapshot(bs);
         aio_context_release(ctx);
 
         if (vmstate_bs) {
             if (g_str_equal(vmstate_bs,
                             bdrv_get_node_name(bs))) {
                 if (found) {
                     return bs;
                 } else {
                     error_setg(errp,
                                "vmstate block device '%s' does not support snapshots",
                                vmstate_bs);
                     return NULL;
                 }
             }
         } else if (found) {
             return bs;
         }
 
         iterbdrvs = iterbdrvs->next;
     }
 
     if (vmstate_bs) {
         error_setg(errp,
                    "vmstate block device '%s' does not exist", vmstate_bs);
     } else {
         error_setg(errp,
                    "no block device can store vmstate for snapshot");
     }
     return NULL;
 }