block: fix external snapshot abort permission error
In external_snapshot_abort(), we try to undo what was done in
external_snapshot_prepare() calling bdrv_replace_node() to swap the
nodes back. However, we receive a permissions error as writers are
blocked on the old node, which is now the new node backing file.
An easy fix (initially suggested by Kevin Wolf) is to call
bdrv_set_backing_hd() on the new node, to set the backing node to NULL.
Signed-off-by: Jeff Cody <jcody@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
diff --git a/blockdev.c b/blockdev.c
index 892d768..6472548 100644
--- a/blockdev.c
+++ b/blockdev.c
@@ -1803,7 +1803,11 @@
DO_UPCAST(ExternalSnapshotState, common, common);
if (state->new_bs) {
if (state->overlay_appended) {
+ bdrv_ref(state->old_bs); /* we can't let bdrv_set_backind_hd()
+ close state->old_bs; we need it */
+ bdrv_set_backing_hd(state->new_bs, NULL, &error_abort);
bdrv_replace_node(state->new_bs, state->old_bs, &error_abort);
+ bdrv_unref(state->old_bs); /* bdrv_replace_node() ref'ed old_bs */
}
}
}
