From 9221edb7120e2dc3ae90f1c58514979f7ba40e46 Mon Sep 17 00:00:00 2001 From: Johannes Weiner Date: Tue, 1 Feb 2011 15:52:42 -0800 Subject: [PATCH] memcg: prevent endless loop when charging huge pages The charging code can encounter a charge size that is bigger than a regular page in two situations: one is a batched charge to fill the per-cpu stocks, the other is a huge page charge. This code is distributed over two functions, however, and only the outer one is aware of huge pages. In case the charging fails, the inner function will tell the outer function to retry if the charge size is bigger than regular pages--assuming batched charging is the only case. And the outer function will retry forever charging a huge page. This patch makes sure the inner function can distinguish between batch charging and a single huge page charge. It will only signal another attempt if batch charging failed, and go into regular reclaim when it is called on behalf of a huge page. Signed-off-by: Johannes Weiner Acked-by: KAMEZAWA Hiroyuki Reviewed-by: Minchan Kim Cc: Balbir Singh Cc: Daisuke Nishimura Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/memcontrol.c | 11 +++++++++-- 1 file changed, 9 insertions(+), 2 deletions(-) diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 79abb1fd39d2..50eb50e100fd 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -1837,8 +1837,15 @@ static int __mem_cgroup_do_charge(struct mem_cgroup *mem, gfp_t gfp_mask, flags |= MEM_CGROUP_RECLAIM_NOSWAP; } else mem_over_limit = mem_cgroup_from_res_counter(fail_res, res); - - if (csize > PAGE_SIZE) /* change csize and retry */ + /* + * csize can be either a huge page (HPAGE_SIZE), a batch of + * regular pages (CHARGE_SIZE), or a single regular page + * (PAGE_SIZE). + * + * Never reclaim on behalf of optional batching, retry with a + * single page instead. + */ + if (csize == CHARGE_SIZE) return CHARGE_RETRY; if (!(gfp_mask & __GFP_WAIT))