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>

1 files changed, 18 insertions, 17 deletions

diff --git a/include/linux/genhd.h b/include/linux/genhd.h
index ecd2bf63fc8..e9874e7fcdf 100644
--- a/include/linux/genhd.h
+++ b/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);                \
@@ -203,11 +203,13 @@ 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));
+                                sizeof(struct disk_stats));
 }
                                 
 #else /* !CONFIG_SMP */
@@ -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