Re: [PATCH] block: fix preallocate filter: don't do unaligned preallocate requests

[Hanna Reitz <hreitz@redhat.com>]

On 15.02.22 13:16, Vladimir Sementsov-Ogievskiy wrote:
> There is a bug in handling BDRV_REQ_NO_WAIT flag: we still may wait in
> wait_serialising_requests() if request is unaligned. And this is
> possible for the only user of this flag (preallocate filter) if
> underlying file is unaligned to its request_alignment on start.
>
> So, we have to fix preallocate filter to do only aligned preallocate
> requests.
>
> Next, we should fix generic block/io.c somehow. Keeping in mind that
> preallocate is the only user of BDRV_REQ_NO_WAIT and that we have to
> fix its behavior now, it seems more safe to just assert that we never
> use BDRV_REQ_NO_WAIT with unaligned requests and add corresponding
> comment. Let's do so.
>
> Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
> Reviewed-by: Denis V. Lunev <den@openvz.org>
> ---
>   include/block/block.h |  3 ++-
>   block/io.c            |  4 ++++
>   block/preallocate.c   | 15 ++++++++++++---
>   3 files changed, 18 insertions(+), 4 deletions(-)

Thanks, applied to my block branch:

https://gitlab.com/hreitz/qemu/-/commits/block