On Fri, Feb 27, 2015 at 10:13:49AM +0200, Alberto Garcia wrote: > Given a chain of images like [A] <- [B] <- [C] <- [D] <- [E], where > [E] is the active (topmost) image, if we want to remove [B] and [C] we > have to do it before linking [A] and [D]. > > When [A] is set as the backing image of [D] all its operations are > blocked, but removing [B] afterwards would undo those changes, since > [B] would still be connected to [A]. > > This would result in a situation where the backing image [A] has all > its operations unblocked.
Op blockers are linked to a unique Error object. When B's backing_hd is
set to NULL only B->backing_blocker is unblocked but
new_top_bs->backing_blocker is still in place. This means operations
are still blocked.
How do you reproduce this problem? Do you have a test case that can be
added to tests/qemu-iotests/?
> Signed-off-by: Alberto Garcia <be...@igalia.com>
> ---
> block.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/block.c b/block.c
> index 9b707e3..2c36351 100644
> --- a/block.c
> +++ b/block.c
> @@ -2624,13 +2624,14 @@ int bdrv_drop_intermediate(BlockDriverState *active,
> BlockDriverState *top,
> if (ret) {
> goto exit;
> }
> - bdrv_set_backing_hd(new_top_bs, base_bs);
> + bdrv_set_backing_hd(new_top_bs, NULL);
>
> QSIMPLEQ_FOREACH_SAFE(intermediate_state, &states_to_delete, entry,
> next) {
> /* so that bdrv_close() does not recursively close the chain */
> bdrv_set_backing_hd(intermediate_state->bs, NULL);
> bdrv_unref(intermediate_state->bs);
> }
> + bdrv_set_backing_hd(new_top_bs, base_bs);
> ret = 0;
>
> exit:
> --
> 2.1.4
>
>
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