7 files changed, 57 insertions, 1 deletions

diff --git a/Documentation/cgroups/blkio-controller.txt b/Documentation/cgroups/blkio-controller.txt
index ed04fe9cce1a..810e30171a54 100644
--- a/Documentation/cgroups/blkio-controller.txt
+++ b/Documentation/cgroups/blkio-controller.txt
@@ -134,6 +134,11 @@ Details of cgroup files
           minor number of the device, third field specifies the operation type
           and the fourth field specifies the io_wait_time in ns.
 
+- blkio.io_merged
+        - Total number of bios/requests merged into requests belonging to this
+          cgroup. This is further divided by the type of operation - read or
+          write, sync or async.
+
 - blkio.dequeue
         - Debugging aid only enabled if CONFIG_DEBUG_CFQ_IOSCHED=y. This
           gives the statistics about how many a times a group was dequeued
diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index 6797df508821..d23b538858ce 100644
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -127,6 +127,18 @@ void blkiocg_update_completion_stats(struct blkio_group *blkg,
 }
 EXPORT_SYMBOL_GPL(blkiocg_update_completion_stats);
 
+void blkiocg_update_io_merged_stats(struct blkio_group *blkg, bool direction,
+                                        bool sync)
+{
+        unsigned long flags;
+
+        spin_lock_irqsave(&blkg->stats_lock, flags);
+        blkio_add_stat(blkg->stats.stat_arr[BLKIO_STAT_MERGED], 1, direction,
+                        sync);
+        spin_unlock_irqrestore(&blkg->stats_lock, flags);
+}
+EXPORT_SYMBOL_GPL(blkiocg_update_io_merged_stats);
+
 void blkiocg_add_blkio_group(struct blkio_cgroup *blkcg,
                         struct blkio_group *blkg, void *key, dev_t dev)
 {
@@ -363,6 +375,7 @@ SHOW_FUNCTION_PER_GROUP(io_service_bytes, BLKIO_STAT_SERVICE_BYTES, 1);
 SHOW_FUNCTION_PER_GROUP(io_serviced, BLKIO_STAT_SERVICED, 1);
 SHOW_FUNCTION_PER_GROUP(io_service_time, BLKIO_STAT_SERVICE_TIME, 1);
 SHOW_FUNCTION_PER_GROUP(io_wait_time, BLKIO_STAT_WAIT_TIME, 1);
+SHOW_FUNCTION_PER_GROUP(io_merged, BLKIO_STAT_MERGED, 1);
 #ifdef CONFIG_DEBUG_BLK_CGROUP
 SHOW_FUNCTION_PER_GROUP(dequeue, BLKIO_STAT_DEQUEUE, 0);
 #endif
@@ -408,6 +421,10 @@ struct cftype blkio_files[] = {
                 .read_map = blkiocg_io_wait_time_read,
         },
         {
+                .name = "io_merged",
+                .read_map = blkiocg_io_merged_read,
+        },
+        {
                 .name = "reset_stats",
                 .write_u64 = blkiocg_reset_stats,
         },
diff --git a/block/blk-cgroup.h b/block/blk-cgroup.h
index b22e55390a4f..470a29db6bec 100644
--- a/block/blk-cgroup.h
+++ b/block/blk-cgroup.h
@@ -34,6 +34,8 @@ enum stat_type {
         BLKIO_STAT_SERVICED,
         /* Total time spent waiting in scheduler queue in ns */
         BLKIO_STAT_WAIT_TIME,
+        /* Number of IOs merged */
+        BLKIO_STAT_MERGED,
         /* All the single valued stats go below this */
         BLKIO_STAT_TIME,
         BLKIO_STAT_SECTORS,
@@ -61,7 +63,7 @@ struct blkio_group_stats {
         /* total disk time and nr sectors dispatched by this group */
         uint64_t time;
         uint64_t sectors;
-        uint64_t stat_arr[BLKIO_STAT_WAIT_TIME + 1][BLKIO_STAT_TOTAL];
+        uint64_t stat_arr[BLKIO_STAT_MERGED + 1][BLKIO_STAT_TOTAL];
 #ifdef CONFIG_DEBUG_BLK_CGROUP
         /* How many times this group has been removed from service tree */
         unsigned long dequeue;
@@ -148,6 +150,8 @@ void blkiocg_update_dispatch_stats(struct blkio_group *blkg, uint64_t bytes,
                                                 bool direction, bool sync);
 void blkiocg_update_completion_stats(struct blkio_group *blkg,
         uint64_t start_time, uint64_t io_start_time, bool direction, bool sync);
+void blkiocg_update_io_merged_stats(struct blkio_group *blkg, bool direction,
+                                        bool sync);
 #else
 struct cgroup;
 static inline struct blkio_cgroup *
@@ -169,5 +173,7 @@ static inline void blkiocg_update_dispatch_stats(struct blkio_group *blkg,
 static inline void blkiocg_update_completion_stats(struct blkio_group *blkg,
                 uint64_t start_time, uint64_t io_start_time, bool direction,
                 bool sync) {}
+static inline void blkiocg_update_io_merged_stats(struct blkio_group *blkg,
+                                                bool direction, bool sync) {}
 #endif
 #endif /* _BLK_CGROUP_H */
diff --git a/block/blk-core.c b/block/blk-core.c
index 4b1b29ef2cb0..e9a5ae25db8c 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -1202,6 +1202,7 @@ static int __make_request(struct request_queue *q, struct bio *bio)
                 if (!blk_rq_cpu_valid(req))
                         req->cpu = bio->bi_comp_cpu;
                 drive_stat_acct(req, 0);
+                elv_bio_merged(q, req, bio);
                 if (!attempt_back_merge(q, req))
                         elv_merged_request(q, req, el_ret);
                 goto out;
@@ -1235,6 +1236,7 @@ static int __make_request(struct request_queue *q, struct bio *bio)
                 if (!blk_rq_cpu_valid(req))
                         req->cpu = bio->bi_comp_cpu;
                 drive_stat_acct(req, 0);
+                elv_bio_merged(q, req, bio);
                 if (!attempt_front_merge(q, req))
                         elv_merged_request(q, req, el_ret);
                 goto out;
diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index 5617ae030b15..4eb1906cf6c6 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -1467,6 +1467,14 @@ static void cfq_merged_request(struct request_queue *q, struct request *req,
         }
 }
 
+static void cfq_bio_merged(struct request_queue *q, struct request *req,
+                                struct bio *bio)
+{
+        struct cfq_queue *cfqq = RQ_CFQQ(req);
+        blkiocg_update_io_merged_stats(&cfqq->cfqg->blkg, bio_data_dir(bio),
+                                        cfq_bio_sync(bio));
+}
+
 static void
 cfq_merged_requests(struct request_queue *q, struct request *rq,
                     struct request *next)
@@ -1484,6 +1492,8 @@ cfq_merged_requests(struct request_queue *q, struct request *rq,
         if (cfqq->next_rq == next)
                 cfqq->next_rq = rq;
         cfq_remove_request(next);
+        blkiocg_update_io_merged_stats(&cfqq->cfqg->blkg, rq_data_dir(next),
+                                        rq_is_sync(next));
 }
 
 static int cfq_allow_merge(struct request_queue *q, struct request *rq,
@@ -3861,6 +3871,7 @@ static struct elevator_type iosched_cfq = {
                 .elevator_merged_fn =           cfq_merged_request,
                 .elevator_merge_req_fn =        cfq_merged_requests,
                 .elevator_allow_merge_fn =      cfq_allow_merge,
+                .elevator_bio_merged_fn =       cfq_bio_merged,
                 .elevator_dispatch_fn =         cfq_dispatch_requests,
                 .elevator_add_req_fn =          cfq_insert_request,
                 .elevator_activate_req_fn =     cfq_activate_request,
diff --git a/block/elevator.c b/block/elevator.c
index 76e3702d5381..5e734592bb40 100644
--- a/block/elevator.c
+++ b/block/elevator.c
@@ -539,6 +539,15 @@ void elv_merge_requests(struct request_queue *q, struct request *rq,
         q->last_merge = rq;
 }
 
+void elv_bio_merged(struct request_queue *q, struct request *rq,
+                        struct bio *bio)
+{
+        struct elevator_queue *e = q->elevator;
+
+        if (e->ops->elevator_bio_merged_fn)
+                e->ops->elevator_bio_merged_fn(q, rq, bio);
+}
+
 void elv_requeue_request(struct request_queue *q, struct request *rq)
 {
         /*
diff --git a/include/linux/elevator.h b/include/linux/elevator.h
index 1cb3372e65d8..2c958f4fce1e 100644
--- a/include/linux/elevator.h
+++ b/include/linux/elevator.h
@@ -14,6 +14,9 @@ typedef void (elevator_merged_fn) (struct request_queue *, struct request *, int
 
 typedef int (elevator_allow_merge_fn) (struct request_queue *, struct request *, struct bio *);
 
+typedef void (elevator_bio_merged_fn) (struct request_queue *,
+                                                struct request *, struct bio *);
+
 typedef int (elevator_dispatch_fn) (struct request_queue *, int);
 
 typedef void (elevator_add_req_fn) (struct request_queue *, struct request *);
@@ -36,6 +39,7 @@ struct elevator_ops
         elevator_merged_fn *elevator_merged_fn;
         elevator_merge_req_fn *elevator_merge_req_fn;
         elevator_allow_merge_fn *elevator_allow_merge_fn;
+        elevator_bio_merged_fn *elevator_bio_merged_fn;
 
         elevator_dispatch_fn *elevator_dispatch_fn;
         elevator_add_req_fn *elevator_add_req_fn;
@@ -103,6 +107,8 @@ extern int elv_merge(struct request_queue *, struct request **, struct bio *);
 extern void elv_merge_requests(struct request_queue *, struct request *,
                                struct request *);
 extern void elv_merged_request(struct request_queue *, struct request *, int);
+extern void elv_bio_merged(struct request_queue *q, struct request *,
+                                struct bio *);
 extern void elv_requeue_request(struct request_queue *, struct request *);
 extern int elv_queue_empty(struct request_queue *);
 extern struct request *elv_former_request(struct request_queue *, struct request *);