block: avoid duplicate calls to get_part() in disk stat code

get_part() is fairly expensive, as it O(N) loops over partitions
to find the right one. In lots of normal IO paths we end up looking
up the partition twice, to make matters even worse. Change the
stat add code to accept a passed in partition instead.
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

block/blk-core.c

@@ -54,15 +54,16 @@ static DEFINE_PER_CPU(struct list_head, blk_cpu_done);
 
 static void drive_stat_acct(struct request *rq, int new_io)
 {
+	struct hd_struct *part;
 	int rw = rq_data_dir(rq);
 
 	if (!blk_fs_request(rq) || !rq->rq_disk)
 		return;
 
-	if (!new_io) {
-		__all_stat_inc(rq->rq_disk, merges[rw], rq->sector);
-	} else {
-		struct hd_struct *part = get_part(rq->rq_disk, rq->sector);
+	part = get_part(rq->rq_disk, rq->sector);
+	if (!new_io)
+		__all_stat_inc(rq->rq_disk, part, merges[rw], rq->sector);
+	else {
 		disk_round_stats(rq->rq_disk);
 		rq->rq_disk->in_flight++;
 		if (part) {
@@ -1538,9 +1539,10 @@ static int __end_that_request_first(struct request *req, int error,
 	}
 
 	if (blk_fs_request(req) && req->rq_disk) {
+		struct hd_struct *part = get_part(req->rq_disk, req->sector);
 		const int rw = rq_data_dir(req);
 
-		all_stat_add(req->rq_disk, sectors[rw],
+		all_stat_add(req->rq_disk, part, sectors[rw],
 				nr_bytes >> 9, req->sector);
 	}
 
@@ -1727,8 +1729,8 @@ static void end_that_request_last(struct request *req, int error)
 		const int rw = rq_data_dir(req);
 		struct hd_struct *part = get_part(disk, req->sector);
 
-		__all_stat_inc(disk, ios[rw], req->sector);
-		__all_stat_add(disk, ticks[rw], duration, req->sector);
+		__all_stat_inc(disk, part, ios[rw], req->sector);
+		__all_stat_add(disk, part, ticks[rw], duration, req->sector);
 		disk_round_stats(disk);
 		disk->in_flight--;
 		if (part) {

drivers/block/aoe/aoecmd.c

@@ -755,11 +755,13 @@ diskstats(struct gendisk *disk, struct bio *bio, ulong duration, sector_t sector
 {
 	unsigned long n_sect = bio->bi_size >> 9;
 	const int rw = bio_data_dir(bio);
+	struct hd_struct *part;
 
-	all_stat_inc(disk, ios[rw], sector);
-	all_stat_add(disk, ticks[rw], duration, sector);
-	all_stat_add(disk, sectors[rw], n_sect, sector);
-	all_stat_add(disk, io_ticks, duration, sector);
+	part = get_part(disk, sector);
+	all_stat_inc(disk, part, ios[rw], sector);
+	all_stat_add(disk, part, ticks[rw], duration, sector);
+	all_stat_add(disk, part, sectors[rw], n_sect, sector);
+	all_stat_add(disk, part, io_ticks, duration, sector);
 }
 
 void

include/linux/genhd.h

@@ -178,17 +178,17 @@ static inline struct hd_struct *get_part(struct gendisk *gendiskp,
 
 static inline void disk_stat_set_all(struct gendisk *gendiskp, int value)	{
 	int i;
+
 	for_each_possible_cpu(i)
 		memset(per_cpu_ptr(gendiskp->dkstats, i), value,
-				sizeof (struct disk_stats));
+				sizeof(struct disk_stats));
 }		
 
 #define __part_stat_add(part, field, addnd)				\
 	(per_cpu_ptr(part->dkstats, smp_processor_id())->field += addnd)
 
-#define __all_stat_add(gendiskp, field, addnd, sector)		\
+#define __all_stat_add(gendiskp, part, field, addnd, sector)	\
 ({								\
-	struct hd_struct *part = get_part(gendiskp, sector);	\
 	if (part)						\
 		__part_stat_add(part, field, addnd);		\
 	__disk_stat_add(gendiskp, field, addnd);		\
@@ -203,8 +203,10 @@ static inline void disk_stat_set_all(struct gendisk *gendiskp, int value)	{
 	res;								\
 })
 
-static inline void part_stat_set_all(struct hd_struct *part, int value)	{
+static inline void part_stat_set_all(struct hd_struct *part, int value)
+{
 	int i;
+
 	for_each_possible_cpu(i)
 		memset(per_cpu_ptr(part->dkstats, i), value,
 				sizeof(struct disk_stats));
@@ -223,9 +225,8 @@ static inline void disk_stat_set_all(struct gendisk *gendiskp, int value)
 #define __part_stat_add(part, field, addnd) \
 	(part->dkstats.field += addnd)
 
-#define __all_stat_add(gendiskp, field, addnd, sector)		\
+#define __all_stat_add(gendiskp, part, field, addnd, sector)	\
 ({								\
-	struct hd_struct *part = get_part(gendiskp, sector);	\
 	if (part)						\
 		part->dkstats.field += addnd;			\
 	__disk_stat_add(gendiskp, field, addnd);		\
@@ -276,10 +277,10 @@ static inline void part_stat_set_all(struct hd_struct *part, int value)
 #define part_stat_sub(gendiskp, field, subnd) \
 		part_stat_add(gendiskp, field, -subnd)
 
-#define all_stat_add(gendiskp, field, addnd, sector)		\
+#define all_stat_add(gendiskp, part, field, addnd, sector)	\
 	do {							\
 		preempt_disable();				\
-		__all_stat_add(gendiskp, field, addnd, sector);	\
+		__all_stat_add(gendiskp, part, field, addnd, sector);	\
 		preempt_enable();				\
 	} while (0)
 
@@ -288,15 +289,15 @@ static inline void part_stat_set_all(struct hd_struct *part, int value)
 #define all_stat_dec(gendiskp, field, sector) \
 		all_stat_add(gendiskp, field, -1, sector)
 
-#define __all_stat_inc(gendiskp, field, sector) \
-		__all_stat_add(gendiskp, field, 1, sector)
-#define all_stat_inc(gendiskp, field, sector) \
-		all_stat_add(gendiskp, field, 1, sector)
+#define __all_stat_inc(gendiskp, part, field, sector) \
+		__all_stat_add(gendiskp, part, field, 1, sector)
+#define all_stat_inc(gendiskp, part, field, sector) \
+		all_stat_add(gendiskp, part, field, 1, sector)
 
-#define __all_stat_sub(gendiskp, field, subnd, sector) \
-		__all_stat_add(gendiskp, field, -subnd, sector)
-#define all_stat_sub(gendiskp, field, subnd, sector) \
-		all_stat_add(gendiskp, field, -subnd, sector)
+#define __all_stat_sub(gendiskp, part, field, subnd, sector) \
+		__all_stat_add(gendiskp, part, field, -subnd, sector)
+#define all_stat_sub(gendiskp, part, field, subnd, sector) \
+		all_stat_add(gendiskp, part, field, -subnd, sector)
 
 /* Inlines to alloc and free disk stats in struct gendisk */
 #ifdef  CONFIG_SMP