From abe2895b76047bf5430990f2584cd91f76692218 Mon Sep 17 00:00:00 2001 From: Huang Ying Date: Wed, 6 Sep 2017 16:22:41 -0700 Subject: [PATCH] memcg, THP, swap: avoid to duplicated charge THP in swap cache For a THP (Transparent Huge Page), tail_page->mem_cgroup is NULL. So to check whether the page is charged already, we need to check the head page. This is not an issue before because it is impossible for a THP to be in the swap cache before. But after we add delaying splitting THP after swapped out support, it is possible now. Link: http://lkml.kernel.org/r/20170724051840.2309-10-ying.huang@intel.com Signed-off-by: "Huang, Ying" Cc: Johannes Weiner Cc: Minchan Kim Cc: Michal Hocko Cc: Andrea Arcangeli Cc: "Kirill A . Shutemov" Cc: Dan Williams Cc: Hugh Dickins Cc: Jens Axboe Cc: Rik van Riel Cc: Ross Zwisler [for brd.c, zram_drv.c, pmem.c] Cc: Shaohua Li Cc: Vishal L Verma Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/memcontrol.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 2ae315e4d9f6..e7f47a38fe4f 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -5430,7 +5430,7 @@ int mem_cgroup_try_charge(struct page *page, struct mm_struct *mm, * in turn serializes uncharging. */ VM_BUG_ON_PAGE(!PageLocked(page), page); - if (page->mem_cgroup) + if (compound_head(page)->mem_cgroup) goto out; if (do_swap_account) { -- 2.20.1