linux-kernel - [019/107] migrate: dont account swapcache as shmem

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Message-Id: <20110708001654.632520870@clark.kroah.org>
Date:	Thu, 07 Jul 2011 17:15:51 -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,
	Andrea Arcangeli <aarcange@...hat.com>,
	Hugh Dickins <hughd@...gle.com>
Subject: [019/107] migrate: dont account swapcache as shmem

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

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

From: Andrea Arcangeli <aarcange@...hat.com>

commit 99a15e21d96f6857dafab1e5167e5e8183215c9c upstream.

swapcache will reach the below code path in migrate_page_move_mapping,
and swapcache is accounted as NR_FILE_PAGES but it's not accounted as
NR_SHMEM.

Hugh pointed out we must use PageSwapCache instead of comparing
mapping to &swapper_space, to avoid build failure with CONFIG_SWAP=n.

Signed-off-by: Andrea Arcangeli <aarcange@...hat.com>
Acked-by: Hugh Dickins <hughd@...gle.com>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...e.de>

---
 mm/migrate.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -288,7 +288,7 @@ static int migrate_page_move_mapping(str
 	 */
 	__dec_zone_page_state(page, NR_FILE_PAGES);
 	__inc_zone_page_state(newpage, NR_FILE_PAGES);
-	if (PageSwapBacked(page)) {
+	if (!PageSwapCache(page) && PageSwapBacked(page)) {
 		__dec_zone_page_state(page, NR_SHMEM);
 		__inc_zone_page_state(newpage, NR_SHMEM);
 	}


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