1 files changed, 22 insertions, 4 deletions

diff --git a/block/elevator.c b/block/elevator.c
index c0063f345c5d..62c7a3069d3a 100644
--- a/block/elevator.c
+++ b/block/elevator.c
@@ -51,6 +51,21 @@ static const int elv_hash_shift = 6;
 #define ELV_ON_HASH(rq)         (!hlist_unhashed(&(rq)->hash))
 
 /*
+ * Query io scheduler to see if the current process issuing bio may be
+ * merged with rq.
+ */
+static int elv_iosched_allow_merge(struct request *rq, struct bio *bio)
+{
+        request_queue_t *q = rq->q;
+        elevator_t *e = q->elevator;
+
+        if (e->ops->elevator_allow_merge_fn)
+                return e->ops->elevator_allow_merge_fn(q, rq, bio);
+
+        return 1;
+}
+
+/*
  * can we safely merge with this request?
  */
 inline int elv_rq_merge_ok(struct request *rq, struct bio *bio)
@@ -65,12 +80,15 @@ inline int elv_rq_merge_ok(struct request *rq, struct bio *bio)
                 return 0;
 
         /*
-         * same device and no special stuff set, merge is ok
+         * must be same device and not a special request
          */
-        if (rq->rq_disk == bio->bi_bdev->bd_disk && !rq->special)
-                return 1;
+        if (rq->rq_disk != bio->bi_bdev->bd_disk || !rq->special)
+                return 0;
 
-        return 0;
+        if (!elv_iosched_allow_merge(rq, bio))
+                return 0;
+
+        return 1;
 }
 EXPORT_SYMBOL(elv_rq_merge_ok);