From: Andrea Arcangeli <aarcange@redhat.com>
Date: Thu, 16 Jun 2011 19:56:19 +0000 (-0700)
Subject: migrate: don't account swapcache as shmem
X-Git-Tag: v2.6.35.14~84
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=a67f6f3794586c33e430d8a8e61d0548d33a3abe;p=thirdparty%2Fkernel%2Fstable.git

migrate: don't account swapcache as shmem

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@redhat.com>
Acked-by: Hugh Dickins <hughd@google.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Signed-off-by: Andi Kleen <ak@linux.intel.com>
---

diff --git a/mm/migrate.c b/mm/migrate.c
index 4205b1d6049ed..ca71d064bce7c 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -266,7 +266,7 @@ static int migrate_page_move_mapping(struct address_space *mapping,
 	 */
 	__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);
 	}