Re: [Qemu-devel] [PATCH 05/10] block: Fix blockdev-snapshot error handling

[Kevin Wolf <kwolf@redhat.com>]

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Am 06.03.2017 um 21:23 hat Eric Blake geschrieben:
> On 03/06/2017 10:21 AM, Kevin Wolf wrote:
> > 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>
> > ---
> >  blockdev.c | 4 +++-
> >  1 file changed, 3 insertions(+), 1 deletion(-)
> > 
> 
> Reviewed-by: Eric Blake <eblake@redhat.com>
> 
> By the way, how are you finding all these spots? Is it existing qemu-io
> tests that are failing? And if so, would mentioning which test exposed
> the problem being fixed be worth adding in the commit messages?  If not,
> are there some qemu-io tests to be added?

Most of the fixes here are based on qemu-iotests failures that only
appeared after fixing the error path in change_parent_backing_link(),
which is now later in this series. So there is no commit at which
qemu-iotests cases are actually failing, even though they helped me spot
some problems.

Kevin

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