[patch] remove gendisk->stamp_idle field

struct gendisk has these two fields: stamp, stamp_idle.  Update to
stamp_idle is always in sync with stamp and they are always the same.
Therefore, it does not add any value in having two fields tracking
same timestamp.  Suggest to remove it.

Also, we should only update gendisk stats with non-zero value.
Advantage is that we don't have to needlessly calculate memory address,
and then add zero to the content.

Signed-off-by: Ken Chen <kenneth.w.chen@intel.com>
Signed-off-by: Jens Axboe <axboe@suse.de>

3 files changed, 7 insertions, 8 deletions

diff --git a/drivers/block/ll_rw_blk.c b/drivers/block/ll_rw_blk.c
index baedac522945..c42071fd2e95 100644
--- a/drivers/block/ll_rw_blk.c
+++ b/drivers/block/ll_rw_blk.c
@@ -2433,13 +2433,12 @@ void disk_round_stats(struct gendisk *disk)
 {
         unsigned long now = jiffies;
 
-        __disk_stat_add(disk, time_in_queue,
-                        disk->in_flight * (now - disk->stamp));
+        if (disk->in_flight) {
+                __disk_stat_add(disk, time_in_queue,
+                                disk->in_flight * (now - disk->stamp));
+                __disk_stat_add(disk, io_ticks, (now - disk->stamp));
+        }
         disk->stamp = now;
-
-        if (disk->in_flight)
-                __disk_stat_add(disk, io_ticks, (now - disk->stamp_idle));
-        disk->stamp_idle = now;
 }
 
 /*
diff --git a/fs/partitions/check.c b/fs/partitions/check.c
index 77e178f13162..1e848648a322 100644
--- a/fs/partitions/check.c
+++ b/fs/partitions/check.c
@@ -430,7 +430,7 @@ void del_gendisk(struct gendisk *disk)
         disk->flags &= ~GENHD_FL_UP;
         unlink_gendisk(disk);
         disk_stat_set_all(disk, 0);
-        disk->stamp = disk->stamp_idle = 0;
+        disk->stamp = 0;
 
         devfs_remove_disk(disk);
 
diff --git a/include/linux/genhd.h b/include/linux/genhd.h
index 01796c41c951..142e1c1e0689 100644
--- a/include/linux/genhd.h
+++ b/include/linux/genhd.h
@@ -119,7 +119,7 @@ struct gendisk {
         int policy;
 
         atomic_t sync_io;               /* RAID */
-        unsigned long stamp, stamp_idle;
+        unsigned long stamp;
         int in_flight;
 #ifdef  CONFIG_SMP
         struct disk_stats *dkstats;