2 files changed, 18 insertions, 17 deletions

diff --git a/block/blk-merge.c b/block/blk-merge.c
index 6aa43dec5af4..3826fc32b72c 100644
--- a/block/blk-merge.c
+++ b/block/blk-merge.c
@@ -659,31 +659,32 @@ static void blk_account_io_merge(struct request *req)
 }
 
 /*
- * Has to be called with the request spinlock acquired
+ * For non-mq, this has to be called with the request spinlock acquired.
+ * For mq with scheduling, the appropriate queue wide lock should be held.
  */
-static int attempt_merge(struct request_queue *q, struct request *req,
-                          struct request *next)
+static struct request *attempt_merge(struct request_queue *q,
+                                     struct request *req, struct request *next)
 {
         if (!rq_mergeable(req) || !rq_mergeable(next))
-                return 0;
+                return NULL;
 
         if (req_op(req) != req_op(next))
-                return 0;
+                return NULL;
 
         /*
          * not contiguous
          */
         if (blk_rq_pos(req) + blk_rq_sectors(req) != blk_rq_pos(next))
-                return 0;
+                return NULL;
 
         if (rq_data_dir(req) != rq_data_dir(next)
             || req->rq_disk != next->rq_disk
             || req_no_special_merge(next))
-                return 0;
+                return NULL;
 
         if (req_op(req) == REQ_OP_WRITE_SAME &&
             !blk_write_same_mergeable(req->bio, next->bio))
-                return 0;
+                return NULL;
 
         /*
          * If we are allowed to merge, then append bio list
@@ -692,7 +693,7 @@ static int attempt_merge(struct request_queue *q, struct request *req,
          * counts here.
          */
         if (!ll_merge_requests_fn(q, req, next))
-                return 0;
+                return NULL;
 
         /*
          * If failfast settings disagree or any of the two is already
@@ -735,27 +736,27 @@ static int attempt_merge(struct request_queue *q, struct request *req,
         /* owner-ship of bio passed from next to req */
         next->bio = NULL;
         __blk_put_request(q, next);
-        return 1;
+        return next;
 }
 
-int attempt_back_merge(struct request_queue *q, struct request *rq)
+struct request *attempt_back_merge(struct request_queue *q, struct request *rq)
 {
         struct request *next = elv_latter_request(q, rq);
 
         if (next)
                 return attempt_merge(q, rq, next);
 
-        return 0;
+        return NULL;
 }
 
-int attempt_front_merge(struct request_queue *q, struct request *rq)
+struct request *attempt_front_merge(struct request_queue *q, struct request *rq)
 {
         struct request *prev = elv_former_request(q, rq);
 
         if (prev)
                 return attempt_merge(q, prev, rq);
 
-        return 0;
+        return NULL;
 }
 
 int blk_attempt_req_merge(struct request_queue *q, struct request *rq,
@@ -767,7 +768,7 @@ int blk_attempt_req_merge(struct request_queue *q, struct request *rq,
                 if (!e->type->ops.sq.elevator_allow_rq_merge_fn(q, rq, next))
                         return 0;
 
-        return attempt_merge(q, rq, next);
+        return attempt_merge(q, rq, next) != NULL;
 }
 
 bool blk_rq_merge_ok(struct request *rq, struct bio *bio)
diff --git a/block/blk.h b/block/blk.h
index 6aa53a4aad88..4972b98d47e1 100644
--- a/block/blk.h
+++ b/block/blk.h
@@ -208,8 +208,8 @@ int ll_back_merge_fn(struct request_queue *q, struct request *req,
                      struct bio *bio);
 int ll_front_merge_fn(struct request_queue *q, struct request *req, 
                       struct bio *bio);
-int attempt_back_merge(struct request_queue *q, struct request *rq);
-int attempt_front_merge(struct request_queue *q, struct request *rq);
+struct request *attempt_back_merge(struct request_queue *q, struct request *rq);
+struct request *attempt_front_merge(struct request_queue *q, struct request *rq);
 int blk_attempt_req_merge(struct request_queue *q, struct request *rq,
                                 struct request *next);
 void blk_recalc_rq_segments(struct request *rq);