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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 <kwolf@redhat.com>
Reviewed-by: Fam Zheng <famz@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
This commit is contained in:
Kevin Wolf 2017-03-02 15:26:18 +01:00
parent 88f9d1b3d2
commit 067acf28d1
1 changed files with 3 additions and 1 deletions
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4
blockdev.c
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@ -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);
}
}