Only anon pages that are uncharged at the time of the last page table
mapping vanishing may be in swapcache.

When shmem pages, file pages, swap-freed anon pages, or just migrated
pages are uncharged, they are known for sure to be not in swapcache.

Signed-off-by: Johannes Weiner <han...@cmpxchg.org>
Acked-by: KAMEZAWA Hiroyuki <kamezawa.hir...@jp.fujitsu.com>
Acked-by: Michal Hocko <mho...@suse.cz>
---
 mm/memcontrol.c |   13 ++++---------
 1 files changed, 4 insertions(+), 9 deletions(-)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index fb8d525..a5c0693 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -3094,8 +3094,6 @@ void mem_cgroup_uncharge_cache_page(struct page *page)
 {
        VM_BUG_ON(page_mapped(page));
        VM_BUG_ON(page->mapping);
-       if (PageSwapCache(page))
-               return;
        __mem_cgroup_uncharge_common(page, MEM_CGROUP_CHARGE_TYPE_CACHE, false);
 }
 
@@ -3160,8 +3158,6 @@ mem_cgroup_uncharge_swapcache(struct page *page, 
swp_entry_t ent, bool swapout)
        if (!swapout) /* this was a swap cache but the swap is unused ! */
                ctype = MEM_CGROUP_CHARGE_TYPE_DROP;
 
-       if (PageSwapCache(page))
-               return;
        memcg = __mem_cgroup_uncharge_common(page, ctype, false);
 
        /*
@@ -3351,11 +3347,10 @@ void mem_cgroup_end_migration(struct mem_cgroup *memcg,
                unused = oldpage;
        }
        anon = PageAnon(used);
-       if (!PageSwapCache(unused))
-               __mem_cgroup_uncharge_common(unused,
-                                            anon ? MEM_CGROUP_CHARGE_TYPE_ANON
-                                            : MEM_CGROUP_CHARGE_TYPE_CACHE,
-                                            true);
+       __mem_cgroup_uncharge_common(unused,
+                                    anon ? MEM_CGROUP_CHARGE_TYPE_ANON
+                                    : MEM_CGROUP_CHARGE_TYPE_CACHE,
+                                    true);
        css_put(&memcg->css);
        /*
         * We disallowed uncharge of pages under migration because mapcount
-- 
1.7.7.6

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