From bdf4f4d2161a795b9323855a81a047bd68f16202 Mon Sep 17 00:00:00 2001 From: Johannes Weiner Date: Tue, 31 Jul 2012 16:45:50 -0700 Subject: [PATCH] mm: memcg: only check anon swapin page charges for swap cache shmem knows for sure that the page is in swap cache when attempting to charge a page, because the cache charge entry function has a check for it. Only anon pages may be removed from swap cache already when trying to charge their swapin. Adjust the comment, though: '4969c11 mm: fix swapin race condition' added a stable PageSwapCache check under the page lock in the do_swap_page() before calling the memory controller, so it's unuse_pte()'s pte_same() that may fail. Signed-off-by: Johannes Weiner Acked-by: KAMEZAWA Hiroyuki Acked-by: Michal Hocko Cc: David Rientjes Cc: Hugh Dickins Cc: Johannes Weiner Cc: Wanpeng Li Cc: Mel Gorman Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/memcontrol.c | 22 ++++++++++++++-------- 1 file changed, 14 insertions(+), 8 deletions(-) diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 1a2020d72ca0..b06833f2b89e 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -2818,14 +2818,6 @@ static int __mem_cgroup_try_charge_swapin(struct mm_struct *mm, return 0; if (!do_swap_account) goto charge_cur_mm; - /* - * A racing thread's fault, or swapoff, may have already updated - * the pte, and even removed page from swap cache: in those cases - * do_swap_page()'s pte_same() test will fail; but there's also a - * KSM case which does need to charge the page. - */ - if (!PageSwapCache(page)) - goto charge_cur_mm; memcg = try_get_mem_cgroup_from_page(page); if (!memcg) goto charge_cur_mm; @@ -2848,6 +2840,20 @@ int mem_cgroup_try_charge_swapin(struct mm_struct *mm, struct page *page, *memcgp = NULL; if (mem_cgroup_disabled()) return 0; + /* + * A racing thread's fault, or swapoff, may have already + * updated the pte, and even removed page from swap cache: in + * those cases unuse_pte()'s pte_same() test will fail; but + * there's also a KSM case which does need to charge the page. + */ + if (!PageSwapCache(page)) { + int ret; + + ret = __mem_cgroup_try_charge(mm, gfp_mask, 1, memcgp, true); + if (ret == -EINTR) + ret = 0; + return ret; + } return __mem_cgroup_try_charge_swapin(mm, page, gfp_mask, memcgp); } -- 2.30.2