linux-kernel - [patch 03/10] mm: memcg: push down PageSwapCache check into uncharge entry functions

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Date:	Wed, 11 Jul 2012 19:02:15 +0200
From:	Johannes Weiner <hannes@...xchg.org>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Michal Hocko <mhocko@...e.cz>, Hugh Dickins <hughd@...gle.com>,
	David Rientjes <rientjes@...gle.com>,
	Wanpeng Li <liwp.linux@...il.com>, linux-mm@...ck.org,
	cgroups@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [patch 03/10] 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@...xchg.org>
Acked-by: Michal Hocko <mhocko@...e.cz>
---
 mm/memcontrol.c |   18 ++++++++++++------
 1 files changed, 12 insertions(+), 6 deletions(-)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 12ee2de..fb8d525 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -2988,8 +2988,7 @@ __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);
@@ -3086,6 +3085,8 @@ 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);
 }
 
@@ -3093,6 +3094,8 @@ 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);
 }
 
@@ -3157,6 +3160,8 @@ 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);
 
 	/*
@@ -3346,10 +3351,11 @@ 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
-- 
1.7.7.6

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