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 <jc...@redhat.com> --- blockdev.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/blockdev.c b/blockdev.c index 892d768..6472548 100644 --- a/blockdev.c +++ b/blockdev.c @@ -1803,7 +1803,11 @@ static void external_snapshot_abort(BlkActionState *common) 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 */ } } } -- 2.9.3