linux-kernel - [ 57/75] memcg: fix Bad page state after replace_page

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Date:	Thu, 19 Apr 2012 14:04:00 -0700
From:	Greg KH <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:	torvalds@...ux-foundation.org, akpm@...ux-foundation.org,
	alan@...rguk.ukuu.org.uk, Hugh Dickins <hughd@...gle.com>
Subject: [ 57/75] memcg: fix Bad page state after replace_page_cache

3.3-stable review patch.  If anyone has any objections, please let me know.

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

From: Hugh Dickins <hughd@...gle.com>

commit 9b7f43afd417a6feb80841d30ced4051c362eb5d upstream.

My 9ce70c0240d0 "memcg: fix deadlock by inverting lrucare nesting" put a
nasty little bug into v3.3's version of mem_cgroup_replace_page_cache(),
sometimes used for FUSE.  Replacing __mem_cgroup_commit_charge_lrucare()
by __mem_cgroup_commit_charge(), I used the "pc" pointer set up earlier:
but it's for oldpage, and needs now to be for newpage.  Once oldpage was
freed, its PageCgroupUsed bit (cleared above but set again here) caused
"Bad page state" messages - and perhaps worse, being missed from newpage.
(I didn't find this by using FUSE, but in reusing the function for tmpfs.)

Signed-off-by: Hugh Dickins <hughd@...gle.com>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 mm/memcontrol.c |    1 +
 1 file changed, 1 insertion(+)

--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -3350,6 +3350,7 @@ void mem_cgroup_replace_page_cache(struc
 	 * the newpage may be on LRU(or pagevec for LRU) already. We lock
 	 * LRU while we overwrite pc->mem_cgroup.
 	 */
+	pc = lookup_page_cgroup(newpage);
 	__mem_cgroup_commit_charge(memcg, newpage, 1, pc, type, true);
 }

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