[PATCH] block: Don't count_vm_events for discard bio in submit_bio.

[Tao Ma <tao.ma@oracle.com>]

In submit_bio, we count vm events by check READ/WRITE.
But actually DISCARD_NOBARRIER also has the WRITE flag set.
It looks as if in blkdev_issue_discard, we also add a
page as the payload and the bio_has_data check isn't enough.
So add another check for discard bio.

Cc: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Tao Ma <tao.ma@oracle.com>
---
 block/blk-core.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/block/blk-core.c b/block/blk-core.c
index f84cce4..a725602 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -1586,7 +1586,7 @@ void submit_bio(int rw, struct bio *bio)
 	 * If it's a regular read/write or a barrier with data attached,
 	 * go through the normal accounting stuff before submission.
 	 */
-	if (bio_has_data(bio)) {
+	if (bio_has_data(bio) && !(rw & BIO_RW_DISCARD)) {
 		if (rw & WRITE) {
 			count_vm_events(PGPGOUT, count);
 		} else {
-- 
1.5.5