[BLOCK] Document the READ/WRITE splitup of the disk stats

Use the symbolic name where appropriate and add a comment to the
disk_stats structure.

Signed-off-by: Jens Axboe <axboe@suse.de>

2 files changed, 10 insertions, 8 deletions

diff --git a/block/genhd.c b/block/genhd.c
index 54aec4a1ae13..f04609d553b8 100644
--- a/block/genhd.c
+++ b/block/genhd.c
@@ -391,12 +391,14 @@ static ssize_t disk_stats_read(struct gendisk * disk, char *page)
                 "%8u %8u %8llu %8u "
                 "%8u %8u %8u"
                 "\n",
-                disk_stat_read(disk, ios[0]), disk_stat_read(disk, merges[0]),
-                (unsigned long long)disk_stat_read(disk, sectors[0]),
-                jiffies_to_msecs(disk_stat_read(disk, ticks[0])),
-                disk_stat_read(disk, ios[1]), disk_stat_read(disk, merges[1]),
-                (unsigned long long)disk_stat_read(disk, sectors[1]),
-                jiffies_to_msecs(disk_stat_read(disk, ticks[1])),
+                disk_stat_read(disk, ios[READ]),
+                disk_stat_read(disk, merges[READ]),
+                (unsigned long long)disk_stat_read(disk, sectors[READ]),
+                jiffies_to_msecs(disk_stat_read(disk, ticks[READ])),
+                disk_stat_read(disk, ios[WRITE]),
+                disk_stat_read(disk, merges[WRITE]),
+                (unsigned long long)disk_stat_read(disk, sectors[WRITE]),
+                jiffies_to_msecs(disk_stat_read(disk, ticks[WRITE])),
                 disk->in_flight,
                 jiffies_to_msecs(disk_stat_read(disk, io_ticks)),
                 jiffies_to_msecs(disk_stat_read(disk, time_in_queue)));
diff --git a/include/linux/genhd.h b/include/linux/genhd.h
index 8eeaa53a68c9..eef5ccdcd731 100644
--- a/include/linux/genhd.h
+++ b/include/linux/genhd.h
@@ -78,7 +78,7 @@ struct hd_struct {
         sector_t start_sect;
         sector_t nr_sects;
         struct kobject kobj;
-        unsigned ios[2], sectors[2];
+        unsigned ios[2], sectors[2];    /* READs and WRITEs */
         int policy, partno;
 };
 
@@ -89,7 +89,7 @@ struct hd_struct {
 #define GENHD_FL_SUPPRESS_PARTITION_INFO        32
 
 struct disk_stats {
-        unsigned sectors[2];
+        unsigned sectors[2];            /* READs and WRITEs */
         unsigned ios[2];
         unsigned merges[2];
         unsigned ticks[2];