blkcg: Track DISCARD statistics and output them in cgroup io.stat

Add tracking of REQ_OP_DISCARD ios to the per-cgroup io.stat.  Two
fields, dbytes and dios, to respectively count the total bytes and
number of discards are added.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Andy Newell <newella@fb.com>
Cc: Michael Callahan <michaelcallahan@fb.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

1 files changed, 4 insertions, 1 deletions

diff --git a/include/linux/blk-cgroup.h b/include/linux/blk-cgroup.h
index de57de4831d5..3bed5e02a873 100644
--- a/include/linux/blk-cgroup.h
+++ b/include/linux/blk-cgroup.h
@@ -35,6 +35,7 @@ enum blkg_rwstat_type {
         BLKG_RWSTAT_WRITE,
         BLKG_RWSTAT_SYNC,
         BLKG_RWSTAT_ASYNC,
+        BLKG_RWSTAT_DISCARD,
 
         BLKG_RWSTAT_NR,
         BLKG_RWSTAT_TOTAL = BLKG_RWSTAT_NR,
@@ -649,7 +650,9 @@ static inline void blkg_rwstat_add(struct blkg_rwstat *rwstat,
 {
         struct percpu_counter *cnt;
 
-        if (op_is_write(op))
+        if (op_is_discard(op))
+                cnt = &rwstat->cpu_cnt[BLKG_RWSTAT_DISCARD];
+        else if (op_is_write(op))
                 cnt = &rwstat->cpu_cnt[BLKG_RWSTAT_WRITE];
         else
                 cnt = &rwstat->cpu_cnt[BLKG_RWSTAT_READ];