path: root/block
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authorJens Axboe <axboe@kernel.dk>2013-10-29 12:11:47 -0600
committerJens Axboe <axboe@kernel.dk>2013-10-29 12:11:47 -0600
commite7e245000110a7794de8f925b9edc06a9c852f80 (patch)
treec774b4b9e7d7cdb59f3b4a237fd12c4e5eb8bc60 /block
parent92f399c72af2d8cbb9d4f60e11d0d67ca738147f (diff)
blk-mq: don't disallow request merges for req->special being set
For blk-mq, if a driver has requested per-request payload data to carry command structures, they are stuffed into req->special. For an old style request based driver, req->special is used for the same purpose but indicates that a per-driver request structure has been prepared for the request already. So for the old style driver, we do not merge such requests. As most/all blk-mq drivers will use the payload feature, and since we have no problem merging on these, make this check dependent on whether it's a blk-mq enabled driver or not. Reported-by: Shaohua Li <shli@fusionio.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'block')
1 files changed, 14 insertions, 3 deletions
diff --git a/block/blk-merge.c b/block/blk-merge.c
index 5f2448253797..1ffc58977835 100644
--- a/block/blk-merge.c
+++ b/block/blk-merge.c
@@ -308,6 +308,17 @@ int ll_front_merge_fn(struct request_queue *q, struct request *req,
return ll_new_hw_segment(q, req, bio);
+ * blk-mq uses req->special to carry normal driver per-request payload, it
+ * does not indicate a prepared command that we cannot merge with.
+ */
+static bool req_no_special_merge(struct request *req)
+ struct request_queue *q = req->q;
+ return !q->mq_ops && req->special;
static int ll_merge_requests_fn(struct request_queue *q, struct request *req,
struct request *next)
@@ -319,7 +330,7 @@ static int ll_merge_requests_fn(struct request_queue *q, struct request *req,
* First check if the either of the requests are re-queued
* requests. Can't merge them if they are.
- if (req->special || next->special)
+ if (req_no_special_merge(req) || req_no_special_merge(next))
return 0;
@@ -416,7 +427,7 @@ static int attempt_merge(struct request_queue *q, struct request *req,
if (rq_data_dir(req) != rq_data_dir(next)
|| req->rq_disk != next->rq_disk
- || next->special)
+ || req_no_special_merge(next))
return 0;
if (req->cmd_flags & REQ_WRITE_SAME &&
@@ -515,7 +526,7 @@ bool blk_rq_merge_ok(struct request *rq, struct bio *bio)
return false;
/* must be same device and not a special request */
- if (rq->rq_disk != bio->bi_bdev->bd_disk || rq->special)
+ if (rq->rq_disk != bio->bi_bdev->bd_disk || req_no_special_merge(rq))
return false;
/* only merge integrity protected bio into ditto rq */

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