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memcg: fix Bad page state after replace_page_cache 

My 9ce70c0240 "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@google.com>
Cc: stable@vger.kernel.org [v3.3 only]
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Hugh Dickins 2012-04-18 23:34:46 -07:00 committed by Linus Torvalds
parent 932e9f352b
commit 9b7f43afd4
1 changed files with 1 additions and 0 deletions
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mm/memcontrol.c
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@ -3392,6 +3392,7 @@ void mem_cgroup_replace_page_cache(struct page *oldpage,
* the newpage may be on LRU(or pagevec for LRU) already. We lock * the newpage may be on LRU(or pagevec for LRU) already. We lock
* LRU while we overwrite pc->mem_cgroup. * LRU while we overwrite pc->mem_cgroup.
*/ */
pc = lookup_page_cgroup(newpage);
__mem_cgroup_commit_charge(memcg, newpage, 1, pc, type, true); __mem_cgroup_commit_charge(memcg, newpage, 1, pc, type, true);
} }