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block/io: refactor bdrv_pad_request(): move bdrv_pad_request() up 

Prepare for the following patch when bdrv_pad_request() will be able to
fail. Update the comments.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-Id: <20201211183934.169161-5-vsementsov@virtuozzo.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
[eblake: grammar tweak]
Signed-off-by: Eric Blake <eblake@redhat.com>
This commit is contained in:
Vladimir Sementsov-Ogievskiy 2020-12-11 21:39:22 +03:00 committed by Eric Blake
parent a56ed80c42
commit f0deecff82
1 changed files with 19 additions and 6 deletions
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25
block/io.c
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@ -2135,6 +2135,7 @@ int coroutine_fn bdrv_co_pwritev_part(BdrvChild *child,
uint64_t align = bs->bl.request_alignment;
BdrvRequestPadding pad;
int ret;
bool padded = false;
trace_bdrv_co_pwritev(child->bs, offset, bytes, flags);
@ -2166,20 +2167,32 @@ int coroutine_fn bdrv_co_pwritev_part(BdrvChild *child,
return 0;
}
if (!(flags & BDRV_REQ_ZERO_WRITE)) {
/*
* Pad request for following read-modify-write cycle.
* bdrv_co_do_zero_pwritev() does aligning by itself, so, we do
* alignment only if there is no ZERO flag.
*/
padded = bdrv_pad_request(bs, &qiov, &qiov_offset, &offset, &bytes,
&pad);
}
bdrv_inc_in_flight(bs);
/*
* Align write if necessary by performing a read-modify-write cycle.
* Pad qiov with the read parts and be sure to have a tracked request not
* only for bdrv_aligned_pwritev, but also for the reads of the RMW cycle.
*/
tracked_request_begin(&req, bs, offset, bytes, BDRV_TRACKED_WRITE);
if (flags & BDRV_REQ_ZERO_WRITE) {
assert(!padded);
ret = bdrv_co_do_zero_pwritev(child, offset, bytes, flags, &req);
goto out;
}
if (bdrv_pad_request(bs, &qiov, &qiov_offset, &offset, &bytes, &pad)) {
if (padded) {
/*
* Request was unaligned to request_alignment and therefore
* padded. We are going to do read-modify-write, and must
* serialize the request to prevent interactions of the
* widened region with other transactions.
*/
bdrv_make_request_serialising(&req, align);
bdrv_padding_rmw_read(child, &req, &pad, false);
}