Commit 9b7f43af authored Apr 18, 2012 by Hugh Dickins Committed by Linus Torvalds Apr 18, 2012

memcg: fix Bad page state after replace_page_cache



My 9ce70c02 "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>

parent 932e9f35

mm/memcontrol.c

+1 −0

Original line number	Diff line number	Diff line
		@@ -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
		* 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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