[PATCH 5.4 099/214] block: respect queue limit of max discard segment

Greg Kroah-Hartman
2020-09-01T16:29:40Z

From: Ming Lei <ming.lei@redhat.com>

[ Upstream commit 943b40c832beb71115e38a1c4d99b640b5342738 ]

When queue_max_discard_segments(q) is 1, blk_discard_mergable() will
return false for discard request, then normal request merge is applied.
However, only queue_max_segments() is checked, so max discard segment
limit isn't respected.

Check max discard segment limit in the request merge code for fixing
the issue.

Discard request failure of virtio_blk is fixed.

Fixes: 69840466086d ("block: fix the DISCARD request merge")
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Cc: Stefano Garzarella <sgarzare@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
block/blk-merge.c | 11 +++++++++--
1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/block/blk-merge.c b/block/blk-merge.c
index 93cff719b0661..c874931bae6b5 100644
--- a/block/blk-merge.c
+++ b/block/blk-merge.c
@@ -553,10 +553,17 @@ int blk_rq_map_sg(struct request_queue *q, struct request *rq,
}
EXPORT_SYMBOL(blk_rq_map_sg);

+static inline unsigned int blk_rq_get_max_segments(struct request *rq)
+{
+ if (req_op(rq) == REQ_OP_DISCARD)
+ return queue_max_discard_segments(rq->q);
+ return queue_max_segments(rq->q);
+}
+
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 > queue_max_segments(req->q))
+ if (req->nr_phys_segments + nr_phys_segs > blk_rq_get_max_segments(req))
goto no_merge;

if (blk_integrity_merge_bio(req->q, req, bio) == false)
@@ -640,7 +647,7 @@ static int ll_merge_requests_fn(struct request_queue *q, struct request *req,
return 0;

total_phys_segments = req->nr_phys_segments + next->nr_phys_segments;
- if (total_phys_segments > queue_max_segments(q))
+ if (total_phys_segments > blk_rq_get_max_segments(req))
return 0;

if (blk_integrity_merge_rq(q, req, next) == false)
--
2.25.1