[ 57/75] memcg: fix Bad page state after replace_page_cache

From: Greg KH
Date: Thu Apr 19 2012 - 17:07:55 EST

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


From: Hugh Dickins <hughd@xxxxxxxxxx>

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@xxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

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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