From 0c59b89c81eab7fe7dcf08f2252ae22a6c081ce8 Mon Sep 17 00:00:00 2001
From: Johannes Weiner <hannes@cmpxchg.org>
Date: Tue, 31 Jul 2012 16:45:31 -0700
Subject: 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>
---
 mm/memcontrol.c | 18 ++++++++++++------
 1 file changed, 12 insertions(+), 6 deletions(-)

(limited to 'mm')

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 7eadcdad06f3..87c2ec49b482 100644
--- 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
-- 
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