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block: fix preallocate filter: don't do unaligned preallocate requests

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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>
Message-Id: <20220215121609.38570-1-vsementsov@virtuozzo.com>
[hreitz: Rebased on block GS/IO split]
Signed-off-by: Hanna Reitz <hreitz@redhat.com>
This commit is contained in:
Vladimir Sementsov-Ogievskiy 2022-02-15 13:16:09 +01:00 • committed by Hanna Reitz
parent b0ea6c98fa
commit 45e62b464a
3 changed files with 18 additions and 4 deletions
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3
include/block/block-common.h
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@ -112,7 +112,8 @@ typedef enum {
/*
* If we need to wait for other requests, just fail immediately. Used
* only together with BDRV_REQ_SERIALISING.
* only together with BDRV_REQ_SERIALISING. Used only with requests aligned
* to request_alignment (corresponding assertions are in block/io.c).
*/
BDRV_REQ_NO_WAIT = 0x400,