block/snapshot.c - third_party/qemu - Git at Google

 /*
  * 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;

     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);

     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;
 }

 int bdrv_can_snapshot(BlockDriverState *bs)
 {
     BlockDriver *drv = bs->drv;
     if (!drv || !bdrv_is_inserted(bs) || bdrv_is_read_only(bs)) {
         return 0;
     }

     if (!drv->bdrv_snapshot_create) {
         if (bs->file != NULL) {
             return bdrv_can_snapshot(bs->file->bs);
         }
         return 0;
     }

     return 1;
 }

 int bdrv_snapshot_create(BlockDriverState *bs,
                          QEMUSnapshotInfo *sn_info)
 {
     BlockDriver *drv = bs->drv;
     if (!drv) {
         return -ENOMEDIUM;
     }
     if (drv->bdrv_snapshot_create) {
         return drv->bdrv_snapshot_create(bs, sn_info);
     }
     if (bs->file) {
         return bdrv_snapshot_create(bs->file->bs, sn_info);
     }
     return -ENOTSUP;
 }

 int bdrv_snapshot_goto(BlockDriverState *bs,
                        const char *snapshot_id,
                        Error **errp)
 {
     BlockDriver *drv = bs->drv;
     int ret, open_ret;

     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;
     }

     if (bs->file) {
         BlockDriverState *file;
         QDict *options = qdict_clone_shallow(bs->options);
         QDict *file_options;
         Error *local_err = NULL;

         file = bs->file->bs;
         /* Prevent it from getting deleted when detached from bs */
         bdrv_ref(file);

         qdict_extract_subqdict(options, &file_options, "file.");
         qobject_unref(file_options);
         qdict_put_str(options, "file", bdrv_get_node_name(file));

         if (drv->bdrv_close) {
             drv->bdrv_close(bs);
         }
         bdrv_unref_child(bs, bs->file);
         bs->file = NULL;

         ret = bdrv_snapshot_goto(file, snapshot_id, errp);
         open_ret = drv->bdrv_open(bs, options, bs->open_flags, &local_err);
         qobject_unref(options);
         if (open_ret < 0) {
             bdrv_unref(file);
             bs->drv = NULL;
             /* A bdrv_snapshot_goto() error takes precedence */
             error_propagate(errp, local_err);
             return ret < 0 ? ret : open_ret;
         }

         assert(bs->file->bs == file);
         bdrv_unref(file);
         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;
     int ret;

     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 (bs->file) {
         ret = bdrv_snapshot_delete(bs->file->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;
     if (!drv) {
         return -ENOMEDIUM;
     }
     if (drv->bdrv_snapshot_list) {
         return drv->bdrv_snapshot_list(bs, psn_info);
     }
     if (bs->file) {
         return bdrv_snapshot_list(bs->file->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;

     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 (!bs->read_only) {
         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;

     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 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(BlockDriverState **first_bad_bs)
 {
     bool ok = true;
     BlockDriverState *bs;
     BdrvNextIterator it;

     for (bs = bdrv_first(&it); bs; bs = bdrv_next(&it)) {
         AioContext *ctx = bdrv_get_aio_context(bs);

         aio_context_acquire(ctx);
         if (bdrv_all_snapshots_includes_bs(bs)) {
             ok = bdrv_can_snapshot(bs);
         }
         aio_context_release(ctx);
         if (!ok) {
             bdrv_next_cleanup(&it);
             goto fail;
         }
     }

 fail:
     *first_bad_bs = bs;
     return ok;
 }

 int bdrv_all_delete_snapshot(const char *name, BlockDriverState **first_bad_bs,
                              Error **errp)
 {
     int ret = 0;
     BlockDriverState *bs;
     BdrvNextIterator it;
     QEMUSnapshotInfo sn1, *snapshot = &sn1;

     for (bs = bdrv_first(&it); bs; bs = bdrv_next(&it)) {
         AioContext *ctx = bdrv_get_aio_context(bs);

         aio_context_acquire(ctx);
         if (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) {
             bdrv_next_cleanup(&it);
             goto fail;
         }
     }

 fail:
     *first_bad_bs = bs;
     return ret;
 }


 int bdrv_all_goto_snapshot(const char *name, BlockDriverState **first_bad_bs,
                            Error **errp)
 {
     int ret = 0;
     BlockDriverState *bs;
     BdrvNextIterator it;

     for (bs = bdrv_first(&it); bs; bs = bdrv_next(&it)) {
         AioContext *ctx = bdrv_get_aio_context(bs);

         aio_context_acquire(ctx);
         if (bdrv_all_snapshots_includes_bs(bs)) {
             ret = bdrv_snapshot_goto(bs, name, errp);
         }
         aio_context_release(ctx);
         if (ret < 0) {
             bdrv_next_cleanup(&it);
             goto fail;
         }
     }

 fail:
     *first_bad_bs = bs;
     return ret;
 }

 int bdrv_all_find_snapshot(const char *name, BlockDriverState **first_bad_bs)
 {
     QEMUSnapshotInfo sn;
     int err = 0;
     BlockDriverState *bs;
     BdrvNextIterator it;

     for (bs = bdrv_first(&it); bs; bs = bdrv_next(&it)) {
         AioContext *ctx = bdrv_get_aio_context(bs);

         aio_context_acquire(ctx);
         if (bdrv_all_snapshots_includes_bs(bs)) {
             err = bdrv_snapshot_find(bs, &sn, name);
         }
         aio_context_release(ctx);
         if (err < 0) {
             bdrv_next_cleanup(&it);
             goto fail;
         }
     }

 fail:
     *first_bad_bs = bs;
     return err;
 }

 int bdrv_all_create_snapshot(QEMUSnapshotInfo *sn,
                              BlockDriverState *vm_state_bs,
                              uint64_t vm_state_size,
                              BlockDriverState **first_bad_bs)
 {
     int err = 0;
     BlockDriverState *bs;
     BdrvNextIterator it;

     for (bs = bdrv_first(&it); bs; bs = bdrv_next(&it)) {
         AioContext *ctx = bdrv_get_aio_context(bs);

         aio_context_acquire(ctx);
         if (bs == vm_state_bs) {
             sn->vm_state_size = vm_state_size;
             err = bdrv_snapshot_create(bs, sn);
         } else if (bdrv_all_snapshots_includes_bs(bs)) {
             sn->vm_state_size = 0;
             err = bdrv_snapshot_create(bs, sn);
         }
         aio_context_release(ctx);
         if (err < 0) {
             bdrv_next_cleanup(&it);
             goto fail;
         }
     }

 fail:
     *first_bad_bs = bs;
     return err;
 }

 BlockDriverState *bdrv_all_find_vmstate_bs(void)
 {
     BlockDriverState *bs;
     BdrvNextIterator it;

     for (bs = bdrv_first(&it); bs; bs = bdrv_next(&it)) {
         AioContext *ctx = bdrv_get_aio_context(bs);
         bool found;

         aio_context_acquire(ctx);
         found = bdrv_all_snapshots_includes_bs(bs) && bdrv_can_snapshot(bs);
         aio_context_release(ctx);

         if (found) {
             bdrv_next_cleanup(&it);
             break;
         }
     }
     return bs;
 }
	/*
	* 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;

	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);

	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;
	}

	int bdrv_can_snapshot(BlockDriverState *bs)
	{
	BlockDriver *drv = bs->drv;
	if (!drv \|\| !bdrv_is_inserted(bs) \|\| bdrv_is_read_only(bs)) {
	return 0;
	}

	if (!drv->bdrv_snapshot_create) {
	if (bs->file != NULL) {
	return bdrv_can_snapshot(bs->file->bs);
	}
	return 0;
	}

	return 1;
	}

	int bdrv_snapshot_create(BlockDriverState *bs,
	QEMUSnapshotInfo *sn_info)
	{
	BlockDriver *drv = bs->drv;
	if (!drv) {
	return -ENOMEDIUM;
	}
	if (drv->bdrv_snapshot_create) {
	return drv->bdrv_snapshot_create(bs, sn_info);
	}
	if (bs->file) {
	return bdrv_snapshot_create(bs->file->bs, sn_info);
	}
	return -ENOTSUP;
	}

	int bdrv_snapshot_goto(BlockDriverState *bs,
	const char *snapshot_id,
	Error **errp)
	{
	BlockDriver *drv = bs->drv;
	int ret, open_ret;

	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;
	}

	if (bs->file) {
	BlockDriverState *file;
	QDict *options = qdict_clone_shallow(bs->options);
	QDict *file_options;
	Error *local_err = NULL;

	file = bs->file->bs;
	/* Prevent it from getting deleted when detached from bs */
	bdrv_ref(file);

	qdict_extract_subqdict(options, &file_options, "file.");
	qobject_unref(file_options);
	qdict_put_str(options, "file", bdrv_get_node_name(file));

	if (drv->bdrv_close) {
	drv->bdrv_close(bs);
	}
	bdrv_unref_child(bs, bs->file);
	bs->file = NULL;

	ret = bdrv_snapshot_goto(file, snapshot_id, errp);
	open_ret = drv->bdrv_open(bs, options, bs->open_flags, &local_err);
	qobject_unref(options);
	if (open_ret < 0) {
	bdrv_unref(file);
	bs->drv = NULL;
	/* A bdrv_snapshot_goto() error takes precedence */
	error_propagate(errp, local_err);
	return ret < 0 ? ret : open_ret;
	}

	assert(bs->file->bs == file);
	bdrv_unref(file);
	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;
	int ret;

	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 (bs->file) {
	ret = bdrv_snapshot_delete(bs->file->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;
	if (!drv) {
	return -ENOMEDIUM;
	}
	if (drv->bdrv_snapshot_list) {
	return drv->bdrv_snapshot_list(bs, psn_info);
	}
	if (bs->file) {
	return bdrv_snapshot_list(bs->file->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;

	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 (!bs->read_only) {
	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;

	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 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(BlockDriverState **first_bad_bs)
	{
	bool ok = true;
	BlockDriverState *bs;
	BdrvNextIterator it;

	for (bs = bdrv_first(&it); bs; bs = bdrv_next(&it)) {
	AioContext *ctx = bdrv_get_aio_context(bs);

	aio_context_acquire(ctx);
	if (bdrv_all_snapshots_includes_bs(bs)) {
	ok = bdrv_can_snapshot(bs);
	}
	aio_context_release(ctx);
	if (!ok) {
	bdrv_next_cleanup(&it);
	goto fail;
	}
	}

	fail:
	*first_bad_bs = bs;
	return ok;
	}

	int bdrv_all_delete_snapshot(const char name, BlockDriverState *first_bad_bs,
	Error **errp)
	{
	int ret = 0;
	BlockDriverState *bs;
	BdrvNextIterator it;
	QEMUSnapshotInfo sn1, *snapshot = &sn1;

	for (bs = bdrv_first(&it); bs; bs = bdrv_next(&it)) {
	AioContext *ctx = bdrv_get_aio_context(bs);

	aio_context_acquire(ctx);
	if (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) {
	bdrv_next_cleanup(&it);
	goto fail;
	}
	}

	fail:
	*first_bad_bs = bs;
	return ret;
	}


	int bdrv_all_goto_snapshot(const char name, BlockDriverState *first_bad_bs,
	Error **errp)
	{
	int ret = 0;
	BlockDriverState *bs;
	BdrvNextIterator it;

	for (bs = bdrv_first(&it); bs; bs = bdrv_next(&it)) {
	AioContext *ctx = bdrv_get_aio_context(bs);

	aio_context_acquire(ctx);
	if (bdrv_all_snapshots_includes_bs(bs)) {
	ret = bdrv_snapshot_goto(bs, name, errp);
	}
	aio_context_release(ctx);
	if (ret < 0) {
	bdrv_next_cleanup(&it);
	goto fail;
	}
	}

	fail:
	*first_bad_bs = bs;
	return ret;
	}

	int bdrv_all_find_snapshot(const char name, BlockDriverState *first_bad_bs)
	{
	QEMUSnapshotInfo sn;
	int err = 0;
	BlockDriverState *bs;
	BdrvNextIterator it;

	for (bs = bdrv_first(&it); bs; bs = bdrv_next(&it)) {
	AioContext *ctx = bdrv_get_aio_context(bs);

	aio_context_acquire(ctx);
	if (bdrv_all_snapshots_includes_bs(bs)) {
	err = bdrv_snapshot_find(bs, &sn, name);
	}
	aio_context_release(ctx);
	if (err < 0) {
	bdrv_next_cleanup(&it);
	goto fail;
	}
	}

	fail:
	*first_bad_bs = bs;
	return err;
	}

	int bdrv_all_create_snapshot(QEMUSnapshotInfo *sn,
	BlockDriverState *vm_state_bs,
	uint64_t vm_state_size,
	BlockDriverState **first_bad_bs)
	{
	int err = 0;
	BlockDriverState *bs;
	BdrvNextIterator it;

	for (bs = bdrv_first(&it); bs; bs = bdrv_next(&it)) {
	AioContext *ctx = bdrv_get_aio_context(bs);

	aio_context_acquire(ctx);
	if (bs == vm_state_bs) {
	sn->vm_state_size = vm_state_size;
	err = bdrv_snapshot_create(bs, sn);
	} else if (bdrv_all_snapshots_includes_bs(bs)) {
	sn->vm_state_size = 0;
	err = bdrv_snapshot_create(bs, sn);
	}
	aio_context_release(ctx);
	if (err < 0) {
	bdrv_next_cleanup(&it);
	goto fail;
	}
	}

	fail:
	*first_bad_bs = bs;
	return err;
	}

	BlockDriverState *bdrv_all_find_vmstate_bs(void)
	{
	BlockDriverState *bs;
	BdrvNextIterator it;

	for (bs = bdrv_first(&it); bs; bs = bdrv_next(&it)) {
	AioContext *ctx = bdrv_get_aio_context(bs);
	bool found;

	aio_context_acquire(ctx);
	found = bdrv_all_snapshots_includes_bs(bs) && bdrv_can_snapshot(bs);
	aio_context_release(ctx);

	if (found) {
	bdrv_next_cleanup(&it);
	break;
	}
	}
	return bs;
	}