Re: [PATCH 2/3] mirror: Make sure that source and target size match

[Eric Blake]

On 5/7/20 9:52 AM, Kevin Wolf wrote:
> If the target is shorter than the source, mirror would copy data until
> it reaches the end of the target and then fail with an I/O error when
> trying to write past the end.
>
> If the target is longer than the source, the mirror job would complete
> successfully, but the target wouldn't actually be an accurate copy of
> the source image (it would contain some additional garbage at the end).
>
> Fix this by checking that both images have the same size when the job
> starts.
>
> Signed-off-by: Kevin Wolf <address@hidden>
> ---
>   block/mirror.c | 21 ++++++++++++---------
>   1 file changed, 12 insertions(+), 9 deletions(-)

An alternative would be trying to resize the target (like we have to do 
with active commit), but I'm fine with being conservative for now by 
forcing the user to have correct sizing, where we have the option to add 
magic resizing later only if it proves useful and not introducing more 
potential issues.

Reviewed-by: Eric Blake <address@hidden>

--
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3226
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