linux-kernel - [-mm][PATCH 8/10] fix shmem page migration incorrectness on memcgroup

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Message-Id: <20080625190750.D864.KOSAKI.MOTOHIRO@jp.fujitsu.com>
Date:	Wed, 25 Jun 2008 19:09:06 +0900
From:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
To:	LKML <linux-kernel@...r.kernel.org>, linux-mm <linux-mm@...ck.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Lee Schermerhorn <Lee.Schermerhorn@...com>,
	Rik van Riel <riel@...hat.com>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Daisuke Nishimura <nishimura@....nes.nec.co.jp>
Cc:	kosaki.motohiro@...fujitsu.com
Subject: [-mm][PATCH 8/10] fix shmem page migration incorrectness on memcgroup


=
From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>

mem_cgroup_uncharge() against old page is done after radix-tree-replacement.
And there were special handling to ingore swap-cache page. But, shmem can
be swap-cache and file-cache at the same time. Chekcing PageSwapCache() is
not correct here. Check PageAnon() instead.

Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Acked-by: Daisuke Nishimura <nishimura@....nes.nec.co.jp>
Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>

---
 mm/migrate.c |   11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

Index: b/mm/migrate.c
===================================================================
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -332,7 +332,13 @@ static int migrate_page_move_mapping(str
 	__inc_zone_page_state(newpage, NR_FILE_PAGES);
 
 	spin_unlock_irq(&mapping->tree_lock);
-	if (!PageSwapCache(newpage))
+
+	/*
+	 * The page is removed from radix-tree implicitly.
+	 * We uncharge it here but swap cache of anonymous page should be
+	 * uncharged by mem_cgroup_ucharge_page().
+	 */
+	if (!PageAnon(newpage))
 		mem_cgroup_uncharge_cache_page(page);
 
 	return 0;
@@ -381,7 +387,8 @@ static void migrate_page_copy(struct pag
 		/*
 		 * SwapCache is removed implicitly. Uncharge against swapcache
 		 * should be called after ClearPageSwapCache() because
-		 * mem_cgroup_uncharge_page checks the flag.
+		 * mem_cgroup_uncharge_page checks the flag. shmem's swap cache
+		 * is uncharged before here.
 		 */
 		mem_cgroup_uncharge_page(page);
 	}


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