Re: [Qemu-devel] [PATCH 1/2] block: Drain source node in bdrv_replace_node()

[Max Reitz <mreitz@redhat.com>]

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On 21.05.19 21:16, Kevin Wolf wrote:
> Instead of just asserting that no requests are in flight in
> bdrv_replace_node(), which is a requirement that most callers ignore, we
> can just drain the source node right there. This fixes at least starting
> a commit job while I/O is active on the backing chain, but probably
> other callers, too.
> 
> Having requests in flight on the target node isn't a problem because the
> target just gets new parents, but the call path of running requests
> isn't modified. So we can just drop this assertion without a replacement.
> 
> Fixes: https://bugzilla.redhat.com/show_bug.cgi?id=1711643
> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
> ---
>  block.c | 7 ++++---
>  1 file changed, 4 insertions(+), 3 deletions(-)

I had a similar problem with throttle on a blockdev-mirror job.  I
suppose this is more general than my “Don’t increment in_flight in
bdrv_drain_invoke()” solution, that probably doesn’t even work for your
case. :-)

Reviewed-by: Max Reitz <mreitz@redhat.com>


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