block: support passing 'backing': '' to 'blockdev-add'

Passing an empty string allows opening an image but not its backing
file. This was already described in the API documentation, only the
implementation was missing.

This is useful for creating snapshots using images opened with
blockdev-add, since they are not supposed to have a backing image
before the operation.

Signed-off-by: Alberto Garcia <berto@igalia.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Jeff Cody <jcody@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
Alberto Garcia 2015-10-26 14:27:15 +02:00 committed by Kevin Wolf
parent a911e6ae7c
commit 3e8c2e5705

View File

@ -1393,6 +1393,7 @@ static int bdrv_open_inherit(BlockDriverState **pbs, const char *filename,
BlockDriverState *bs;
BlockDriver *drv = NULL;
const char *drvname;
const char *backing;
Error *local_err = NULL;
int snapshot_flags = 0;
@ -1460,6 +1461,12 @@ static int bdrv_open_inherit(BlockDriverState **pbs, const char *filename,
assert(drvname || !(flags & BDRV_O_PROTOCOL));
backing = qdict_get_try_str(options, "backing");
if (backing && *backing == '\0') {
flags |= BDRV_O_NO_BACKING;
qdict_del(options, "backing");
}
bs->open_flags = flags;
bs->options = options;
options = qdict_clone_shallow(options);