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block: fix discard request merge

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ll_new_hw_segment() is reached only in case of single range discard
merge, and we don't have max discard segment size limit actually, so
it is wrong to run the following check:

if (req->nr_phys_segments + nr_phys_segs > blk_rq_get_max_segments(req))

it may be always false since req->nr_phys_segments is initialized as
one, and bio's segment count is still 1, blk_rq_get_max_segments(reg)
is 1 too.

Fix the issue by not doing the check and bypassing the calculation of
discard request's nr_phys_segments.

Based on analysis from Wang Shanker.

Cc: Christoph Hellwig <[email protected]>
Reported-by: Wang Shanker <[email protected]>
Signed-off-by: Ming Lei <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Jens Axboe <[email protected]>
This commit is contained in:
Ming Lei authored and Jens Axboe committed 2021-06-29 07:41:08 -06:00
1 parent c06bc5a3fb
commit 2705dfb209
1 file changed
+6 -2
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block/blk-merge.c
+6 -2
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@@ -559,10 +559,14 @@ static inline unsigned int blk_rq_get_max_segments(struct request *rq)
static inline int ll_new_hw_segment(struct request *req, struct bio *bio,
unsigned int nr_phys_segs)
{
if (req->nr_phys_segments + nr_phys_segs > blk_rq_get_max_segments(req))
if (blk_integrity_merge_bio(req->q, req, bio) == false)
goto no_merge;
if (blk_integrity_merge_bio(req->q, req, bio) == false)
/* discard request merge won't add new segment */
if (req_op(req) == REQ_OP_DISCARD)
return 1;
if (req->nr_phys_segments + nr_phys_segs > blk_rq_get_max_segments(req))
goto no_merge;
/*