From f5e03a4989e80a86f8b514659dca8539132e6e09 Mon Sep 17 00:00:00 2001 From: Michal Hocko Date: Thu, 5 Feb 2015 12:25:14 -0800 Subject: memcg, shmem: fix shmem migration to use lrucare It has been reported that 965GM might trigger VM_BUG_ON_PAGE(!lrucare && PageLRU(oldpage), oldpage) in mem_cgroup_migrate when shmem wants to replace a swap cache page because of shmem_should_replace_page (the page is allocated from an inappropriate zone). shmem_replace_page expects that the oldpage is not on LRU list and calls mem_cgroup_migrate without lrucare. This is obviously incorrect because swapcache pages might be on the LRU list (e.g. swapin readahead page). Fix this by enabling lrucare for the migration in shmem_replace_page. Also clarify that lrucare should be used even if one of the pages might be on LRU list. The BUG_ON will trigger only when CONFIG_DEBUG_VM is enabled but even without that the migration code might leave the old page on an inappropriate memcg' LRU which is not that critical because the page would get removed with its last reference but it is still confusing. Fixes: 0a31bc97c80c ("mm: memcontrol: rewrite uncharge API") Signed-off-by: Michal Hocko Reported-by: Chris Wilson Reported-by: Dave Airlie Acked-by: Hugh Dickins Acked-by: Johannes Weiner Cc: [3.17+] Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/shmem.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'mm/shmem.c') diff --git a/mm/shmem.c b/mm/shmem.c index 73ba1df7c8ba..993e6ba689cc 100644 --- a/mm/shmem.c +++ b/mm/shmem.c @@ -1013,7 +1013,7 @@ static int shmem_replace_page(struct page **pagep, gfp_t gfp, */ oldpage = newpage; } else { - mem_cgroup_migrate(oldpage, newpage, false); + mem_cgroup_migrate(oldpage, newpage, true); lru_cache_add_anon(newpage); *pagep = newpage; } -- cgit v1.2.3