linux-kernel - [183/205] block: Dont count_vm_events for discard bio in submit

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Date:	Fri, 30 Jul 2010 10:53:20 -0700
From:	Greg KH <gregkh@...e.de>
To:	linux-kernel@...r.kernel.org, stable@...nel.org
Cc:	stable-review@...nel.org, torvalds@...ux-foundation.org,
	akpm@...ux-foundation.org, alan@...rguk.ukuu.org.uk,
	Tao Ma <tao.ma@...cle.com>, Jens Axboe <jaxboe@...ionio.com>
Subject: [183/205] block: Dont count_vm_events for discard bio in submit_bio.

2.6.34-stable review patch.  If anyone has any objections, please let us know.

------------------

From: Tao Ma <tao.ma@...cle.com>

commit 1b99973f1c82707e46e8cb9416865a1e955e8f8c upstream.

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.

Signed-off-by: Tao Ma <tao.ma@...cle.com>
Signed-off-by: Jens Axboe <jaxboe@...ionio.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...e.de>

---
 block/blk-core.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -1556,7 +1556,7 @@ 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 & (1 << BIO_RW_DISCARD))) {
 		if (rw & WRITE) {
 			count_vm_events(PGPGOUT, count);
 		} else {


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