From: Huang Ying <ying.huang@xxxxxxxxx> Subject: 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@xxxxxxxxx Signed-off-by: "Huang, Ying" <ying.huang@xxxxxxxxx> Cc: Johannes Weiner <hannes@xxxxxxxxxxx> Cc: Minchan Kim <minchan@xxxxxxxxxx> Cc: Michal Hocko <mhocko@xxxxxxxxxx> Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx> Cc: "Kirill A . Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx> Cc: Dan Williams <dan.j.williams@xxxxxxxxx> Cc: Hugh Dickins <hughd@xxxxxxxxxx> Cc: Jens Axboe <axboe@xxxxxxxxx> Cc: Rik van Riel <riel@xxxxxxxxxx> Cc: Ross Zwisler <ross.zwisler@xxxxxxxxx> [for brd.c, zram_drv.c, pmem.c] Cc: Shaohua Li <shli@xxxxxxxxxx> Cc: Vishal L Verma <vishal.l.verma@xxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- mm/memcontrol.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff -puN mm/memcontrol.c~memcg-thp-swap-avoid-to-duplicated-charge-thp-in-swap-cache mm/memcontrol.c --- a/mm/memcontrol.c~memcg-thp-swap-avoid-to-duplicated-charge-thp-in-swap-cache +++ a/mm/memcontrol.c @@ -5430,7 +5430,7 @@ int mem_cgroup_try_charge(struct page *p * 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) { _ -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
