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

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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4
block/io.c
View File

@ -2203,6 +2203,7 @@ static int coroutine_fn bdrv_co_do_zero_pwritev(BdrvChild *child,
padding = bdrv_init_padding(bs, offset, bytes, &pad);
if (padding) {
assert(!(flags & BDRV_REQ_NO_WAIT));
bdrv_make_request_serialising(req, align);
bdrv_padding_rmw_read(child, req, &pad, true);
@ -2339,6 +2340,7 @@ int coroutine_fn bdrv_co_pwritev_part(BdrvChild *child,
* serialize the request to prevent interactions of the
* widened region with other transactions.
*/
assert(!(flags & BDRV_REQ_NO_WAIT));
bdrv_make_request_serialising(&req, align);
bdrv_padding_rmw_read(child, &req, &pad, false);
}
@ -3387,6 +3389,8 @@ static int coroutine_fn bdrv_co_copy_range_internal(
/* TODO We can support BDRV_REQ_NO_FALLBACK here */
assert(!(read_flags & BDRV_REQ_NO_FALLBACK));
assert(!(write_flags & BDRV_REQ_NO_FALLBACK));
assert(!(read_flags & BDRV_REQ_NO_WAIT));
assert(!(write_flags & BDRV_REQ_NO_WAIT));
if (!dst || !dst->bs || !bdrv_is_inserted(dst->bs)) {
return -ENOMEDIUM;

15
block/preallocate.c
View File

@ -276,6 +276,10 @@ static bool coroutine_fn handle_write(BlockDriverState *bs, int64_t offset,
int64_t end = offset + bytes;
int64_t prealloc_start, prealloc_end;
int ret;
uint32_t file_align = bs->file->bs->bl.request_alignment;
uint32_t prealloc_align = MAX(s->opts.prealloc_align, file_align);
assert(QEMU_IS_ALIGNED(prealloc_align, file_align));
if (!has_prealloc_perms(bs)) {
/* We don't have state neither should try to recover it */
@ -320,9 +324,14 @@ static bool coroutine_fn handle_write(BlockDriverState *bs, int64_t offset,
/* Now we want new preallocation, as request writes beyond s->file_end. */
prealloc_start = want_merge_zero ? MIN(offset, s->file_end) : s->file_end;
prealloc_end = QEMU_ALIGN_UP(end + s->opts.prealloc_size,
s->opts.prealloc_align);
prealloc_start = QEMU_ALIGN_UP(
want_merge_zero ? MIN(offset, s->file_end) : s->file_end,
file_align);
prealloc_end = QEMU_ALIGN_UP(
MAX(prealloc_start, end) + s->opts.prealloc_size,
prealloc_align);
want_merge_zero = want_merge_zero && (prealloc_start <= offset);
ret = bdrv_co_pwrite_zeroes(
bs->file, prealloc_start, prealloc_end - prealloc_start,

3
include/block/block-common.h
View File

@ -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,