From 067acf28d1d726059f994356f25e054ce2926acf Mon Sep 17 00:00:00 2001 From: Kevin Wolf Date: Thu, 2 Mar 2017 15:26:18 +0100 Subject: [PATCH] block: Fix blockdev-snapshot error handling For blockdev-snapshot, external_snapshot_prepare() accepts an arbitrary node reference at first and only checks later whether it already has a backing file. Between those places, other errors can occur. Therefore checking in external_snapshot_abort() whether state->new_bs has a backing file is not sufficient to tell whether bdrv_append() was already completed or not. Trying to undo the bdrv_append() when it wasn't even executed is wrong. Introduce a new boolean flag in the state to fix this. Signed-off-by: Kevin Wolf Reviewed-by: Fam Zheng Reviewed-by: Eric Blake --- blockdev.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/blockdev.c b/blockdev.c index 8eb4e84fe0..af67ce4e56 100644 --- a/blockdev.c +++ b/blockdev.c @@ -1614,6 +1614,7 @@ typedef struct ExternalSnapshotState { BlockDriverState *old_bs; BlockDriverState *new_bs; AioContext *aio_context; + bool overlay_appended; } ExternalSnapshotState; static void external_snapshot_prepare(BlkActionState *common, @@ -1780,6 +1781,7 @@ static void external_snapshot_prepare(BlkActionState *common, error_propagate(errp, local_err); return; } + state->overlay_appended = true; } static void external_snapshot_commit(BlkActionState *common) @@ -1803,7 +1805,7 @@ static void external_snapshot_abort(BlkActionState *common) ExternalSnapshotState *state = DO_UPCAST(ExternalSnapshotState, common, common); if (state->new_bs) { - if (state->new_bs->backing) { + if (state->overlay_appended) { bdrv_replace_in_backing_chain(state->new_bs, state->old_bs); } }