mm: memcg: push down PageSwapCache check into uncharge entry functions

Not all uncharge paths need to check if the page is swapcache, some of
them can know for sure.

Push down the check into all callsites of uncharge_common() so that the
patch that removes some of them is more obvious.

Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Michal Hocko <mhocko@suse.cz>
Cc: David Rientjes <rientjes@google.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Wanpeng Li <liwp.linux@gmail.com>
Cc: Mel Gorman <mel@csn.ul.ie>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 7eadcdad06f31bb7ed7b86fd321d4aebf5fbb595..87c2ec49b4825303b1ba48b98b844c88fb3bab76 100644 (file)
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -2987,8 +2987,7 @@ __mem_cgroup_uncharge_common(struct page *page, enum charge_type ctype,
        if (mem_cgroup_disabled())
                return NULL;
 
-       if (PageSwapCache(page))
-               return NULL;
+       VM_BUG_ON(PageSwapCache(page));
 
        if (PageTransHuge(page)) {
                nr_pages <<= compound_order(page);
@@ -3085,6 +3084,8 @@ void mem_cgroup_uncharge_page(struct page *page)
        if (page_mapped(page))
                return;
        VM_BUG_ON(page->mapping && !PageAnon(page));
+       if (PageSwapCache(page))
+               return;
        __mem_cgroup_uncharge_common(page, MEM_CGROUP_CHARGE_TYPE_ANON, false);
 }
 
@@ -3092,6 +3093,8 @@ 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);
 }
 
@@ -3156,6 +3159,8 @@ 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);
 
        /*
@@ -3345,10 +3350,11 @@ void mem_cgroup_end_migration(struct mem_cgroup *memcg,
                unused = oldpage;
        }
        anon = PageAnon(used);
-       __mem_cgroup_uncharge_common(unused,
-               anon ? MEM_CGROUP_CHARGE_TYPE_ANON
-                    : MEM_CGROUP_CHARGE_TYPE_CACHE,
-               true);
+       if (!PageSwapCache(unused))
+               __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