blkcg: restructure blkio_get_stat()

Restructure blkio_get_stat() to prepare for removal of stats_lock.

* Define BLKIO_STAT_ARR_NR explicitly to denote which stats have
  subtypes instead of using BLKIO_STAT_QUEUED.

* Separate out stat acquisition and printing.  After this, there are
  only two users of blkio_fill_stat().  Just open code it.

* The code was mixing MAX_KEY_LEN and MAX_KEY_LEN - 1.  There's no
  need to subtract one.  Use MAX_KEY_LEN consistently.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

1 files changed, 5 insertions, 1 deletions

diff --git a/block/blk-cgroup.h b/block/blk-cgroup.h
index 1fa3c5e8d87f..8bdcf504f94b 100644
--- a/block/blk-cgroup.h
+++ b/block/blk-cgroup.h
@@ -39,6 +39,7 @@ enum stat_type {
         BLKIO_STAT_WAIT_TIME,
         /* Number of IOs queued up */
         BLKIO_STAT_QUEUED,
+
         /* All the single valued stats go below this */
         BLKIO_STAT_TIME,
 #ifdef CONFIG_DEBUG_BLK_CGROUP
@@ -52,6 +53,9 @@ enum stat_type {
 #endif
 };
 
+/* Types lower than this live in stat_arr and have subtypes */
+#define BLKIO_STAT_ARR_NR       (BLKIO_STAT_QUEUED + 1)
+
 /* Per cpu stats */
 enum stat_type_cpu {
         BLKIO_STAT_CPU_SECTORS,
@@ -117,7 +121,7 @@ struct blkio_cgroup {
 struct blkio_group_stats {
         /* total disk time and nr sectors dispatched by this group */
         uint64_t time;
-        uint64_t stat_arr[BLKIO_STAT_QUEUED + 1][BLKIO_STAT_TOTAL];
+        uint64_t stat_arr[BLKIO_STAT_ARR_NR][BLKIO_STAT_TOTAL];
 #ifdef CONFIG_DEBUG_BLK_CGROUP
         /* Time not charged to this cgroup */
         uint64_t unaccounted_time;