---

yaml
---
r: 44845
b: refs/heads/master
c: da77526
h: refs/heads/master
i:
  44843: 3c0a682
v: v3

[refs]

@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 8e5cfc45e7527eb5c8a9a22d56a7b9227e7c0913
+refs/heads/master: da775265021b61d5eb81df155e36cb0810f6df53

trunk/block/cfq-iosched.c

@@ -568,6 +568,38 @@ cfq_merged_requests(request_queue_t *q, struct request *rq,
 	cfq_remove_request(next);
 }
 
+static int cfq_allow_merge(request_queue_t *q, struct request *rq,
+			   struct bio *bio)
+{
+	struct cfq_data *cfqd = q->elevator->elevator_data;
+	const int rw = bio_data_dir(bio);
+	struct cfq_queue *cfqq;
+	pid_t key;
+
+	/*
+	 * If bio is async or a write, always allow merge
+	 */
+	if (!bio_sync(bio) || rw == WRITE)
+		return 1;
+
+	/*
+	 * bio is sync. if request is not, disallow.
+	 */
+	if (!rq_is_sync(rq))
+		return 0;
+
+	/*
+	 * Ok, both bio and request are sync. Allow merge if they are
+	 * from the same queue.
+	 */
+	key = cfq_queue_pid(current, rw, 1);
+	cfqq = cfq_find_cfq_hash(cfqd, key, current->ioprio);
+	if (cfqq != RQ_CFQQ(rq))
+		return 0;
+
+	return 1;
+}
+
 static inline void
 __cfq_set_active_queue(struct cfq_data *cfqd, struct cfq_queue *cfqq)
 {
@@ -2125,6 +2157,7 @@ static struct elevator_type iosched_cfq = {
 		.elevator_merge_fn = 		cfq_merge,
 		.elevator_merged_fn =		cfq_merged_request,
 		.elevator_merge_req_fn =	cfq_merged_requests,
+		.elevator_allow_merge_fn =	cfq_allow_merge,
 		.elevator_dispatch_fn =		cfq_dispatch_requests,
 		.elevator_add_req_fn =		cfq_insert_request,
 		.elevator_activate_req_fn =	cfq_activate_request,

trunk/block/elevator.c

@@ -50,6 +50,21 @@ static const int elv_hash_shift = 6;
 #define rq_hash_key(rq)		((rq)->sector + (rq)->nr_sectors)
 #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?
  */
@@ -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);
 

trunk/include/linux/elevator.h

@@ -12,6 +12,8 @@ typedef void (elevator_merge_req_fn) (request_queue_t *, struct request *, struc
 
 typedef void (elevator_merged_fn) (request_queue_t *, struct request *, int);
 
+typedef int (elevator_allow_merge_fn) (request_queue_t *, struct request *, struct bio *);
+
 typedef int (elevator_dispatch_fn) (request_queue_t *, int);
 
 typedef void (elevator_add_req_fn) (request_queue_t *, struct request *);
@@ -33,6 +35,7 @@ struct elevator_ops
 	elevator_merge_fn *elevator_merge_fn;
 	elevator_merged_fn *elevator_merged_fn;
 	elevator_merge_req_fn *elevator_merge_req_fn;
+	elevator_allow_merge_fn *elevator_allow_merge_fn;
 
 	elevator_dispatch_fn *elevator_dispatch_fn;
 	elevator_add_req_fn *elevator_add_req_fn;