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SubjectRe: [PATCH] memcg: fix Bad page state after replace_page_cache
On Wed 18-04-12 23:34:46, Hugh Dickins wrote:
> 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@google.com>

Acked-by: Michal Hocko <mhocko@suse.cz>

Thanks

> Cc: stable@vger.kernel.org [v3.3 only]
> ---
>
> mm/memcontrol.c | 1 +
> 1 file changed, 1 insertion(+)
>
> --- 3.4-rc3/mm/memcontrol.c 2012-04-15 20:47:37.151777506 -0700
> +++ linux/mm/memcontrol.c 2012-04-18 22:29:18.490639511 -0700
> @@ -3392,6 +3392,7 @@ 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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--
Michal Hocko
SUSE Labs
SUSE LINUX s.r.o.
Lihovarska 1060/12
190 00 Praha 9
Czech Republic


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