Re: [PATCH 06/13] iotests/298: add testcase for async writes with preallocation filter

[Kevin Wolf <kwolf@redhat.com>]

Am 30.09.2026 um 18:49 hat Denis V. Lunev geschrieben:
> From: Andrey Drobyshev <andrey.drobyshev@virtuozzo.com>
> 
> The testcase creates a 64G image with 1M clusters, generates a list of
> 1M aligned offsets and feeds aio_write commands with those offsets to
> qemu-io run with '--aio native --nocache'. Then we check the data
> written at each of the offsets. Before this series this could result
> in a race within the preallocation filter which would zeroize some
> clusters after actually writing data to them.
> 
> Note: the test does not fail every time as there's a race involved, but
> the failures are pretty consistent so it should be good enough for
> detecting the problem.
> 
> Signed-off-by: Andrey Drobyshev <andrey.drobyshev@virtuozzo.com>
> Signed-off-by: Denis V. Lunev <den@openvz.org>
> CC: Kevin Wolf <kwolf@redhat.com>
> CC: Hanna Reitz <hreitz@redhat.com>
> CC: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru>

FWIW, this doesn't seem to fail at all for me even without the fixes. I
kept it running in a loop for a while, but it always passed.

What is the bug this triggered for you? I don't think it can't be the
locking one because qemu-io tests are always single threaded.

If it is what patch 2 addressed, shouldn't a deterministic test be
possible in which you set a blkdebug breakpoint that suspends the
bdrv_co_pwrite_zeroes() before you launch another write?

Kevin