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block/io.c: drop assertion on double waiting for request serialisation

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The comments states, that on misaligned request we should have already
been waiting. But for bdrv_padding_rmw_read, we called
bdrv_mark_request_serialising with align = request_alignment, and now
we serialise with align = cluster_size. So we may have to wait again
with larger alignment.

Note, that the only user of BDRV_REQ_SERIALISING is backup which issues
cluster-aligned requests, so seems the assertion should not fire for
now. But it's wrong anyway.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Message-Id: <20201021145859.11201-3-vsementsov@virtuozzo.com>
Signed-off-by: Max Reitz <mreitz@redhat.com>
This commit is contained in:
Vladimir Sementsov-Ogievskiy 2020-10-21 17:58:40 +03:00 committed by Max Reitz
parent 2153994e2e
commit 2e36da62cf
1 changed files with 1 additions and 10 deletions
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11
block/io.c
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@ -1827,7 +1827,6 @@ bdrv_co_write_req_prepare(BdrvChild *child, int64_t offset, uint64_t bytes,
BdrvTrackedRequest *req, int flags)
{
BlockDriverState *bs = child->bs;
bool waited;
int64_t end_sector = DIV_ROUND_UP(offset + bytes, BDRV_SECTOR_SIZE);
if (bs->read_only) {
@ -1839,15 +1838,7 @@ bdrv_co_write_req_prepare(BdrvChild *child, int64_t offset, uint64_t bytes,
assert(!(flags & ~BDRV_REQ_MASK));
if (flags & BDRV_REQ_SERIALISING) {
waited = bdrv_mark_request_serialising(req, bdrv_get_cluster_size(bs));
/*
* For a misaligned request we should have already waited earlier,
* because we come after bdrv_padding_rmw_read which must be called
* with the request already marked as serialising.
*/
assert(!waited ||
(req->offset == req->overlap_offset &&
req->bytes == req->overlap_bytes));
bdrv_mark_request_serialising(req, bdrv_get_cluster_size(bs));
} else {
bdrv_wait_serialising_requests(req);
}