migrate: don't account swapcache as shmem

aagit · torvalds · commit 99a15e21d96f · 2011-06-16T15:01:24.000-07:00
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 &amp;swapper_space, to avoid build failure with CONFIG_SWAP=n.

Signed-off-by: Andrea Arcangeli &lt;aarcange@redhat.com&gt;
Acked-by: Hugh Dickins &lt;hughd@google.com&gt;
Cc: stable@kernel.org
Signed-off-by: Linus Torvalds &lt;torvalds@linux-foundation.org&gt;
diff --git a/mm/migrate.c b/mm/migrate.c
@@ -288,7 +288,7 @@ 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);
 	}

Original file line number	Diff line number	Diff line change
`@@ -288,7 +288,7 @@ static int migrate_page_move_mapping(struct address_space *mapping,`
`288`	`288`	`*/`
`289`	`289`	`__dec_zone_page_state(page, NR_FILE_PAGES);`
`290`	`290`	`__inc_zone_page_state(newpage, NR_FILE_PAGES);`
`291`		`- if (PageSwapBacked(page)) {`
	`291`	`+ if (!PageSwapCache(page) && PageSwapBacked(page)) {`
`292`	`292`	`__dec_zone_page_state(page, NR_SHMEM);`
`293`	`293`	`__inc_zone_page_state(newpage, NR_SHMEM);`
`294`	`294`	`}`