path: root/block
diff options
authorMing Lei <>2021-06-28 10:33:12 +0800
committerJens Axboe <>2021-06-29 07:41:08 -0600
commit2705dfb2094777e405e065105e307074af8965c1 (patch)
tree1fdc528a77f5be9455dcedf07b303dbceac04bd1 /block
parentc06bc5a3fb42304d815a2dc41e324b5a97c9f7da (diff)
block: fix discard request merge
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 <> Reported-by: Wang Shanker <> Signed-off-by: Ming Lei <> Link: Signed-off-by: Jens Axboe <>
Diffstat (limited to 'block')
1 files changed, 6 insertions, 2 deletions
diff --git a/block/blk-merge.c b/block/blk-merge.c
index 1398b52a24b4..a11b3b53717e 100644
--- a/block/blk-merge.c
+++ b/block/blk-merge.c
@@ -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;