linux-kernel - [PATCH] mm: initialize variable for mem_cgroup_end_page

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Date:	Wed, 29 Oct 2014 21:44:24 -0400
From:	Sasha Levin <sasha.levin@...cle.com>
To:	akpm@...ux-foundation.org
Cc:	linux-kernel@...r.kernel.org, riel@...hat.com, mhocko@...e.cz,
	hannes@...xchg.org, peterz@...radead.org, linux-mm@...ck.org,
	Sasha Levin <sasha.levin@...cle.com>
Subject: [PATCH] mm: initialize variable for mem_cgroup_end_page_stat

Commit "mm: memcontrol: fix missed end-writeback page accounting" has changed
the behaviour of mem_cgroup_begin_page_stat() to not always set the "locked"
parameter.

We should initialize it at the callers to prevent garbage being used in a
later call to mem_cgroup_end_page_stat().

Signed-off-by: Sasha Levin <sasha.levin@...cle.com>
---
 mm/page-writeback.c |    4 ++--
 mm/rmap.c           |    4 ++--
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index 19ceae8..7a02c97 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -2329,7 +2329,7 @@ int test_clear_page_writeback(struct page *page)
 	struct address_space *mapping = page_mapping(page);
 	unsigned long memcg_flags;
 	struct mem_cgroup *memcg;
-	bool locked;
+	bool locked = false;
 	int ret;
 
 	memcg = mem_cgroup_begin_page_stat(page, &locked, &memcg_flags);
@@ -2366,7 +2366,7 @@ int __test_set_page_writeback(struct page *page, bool keep_write)
 	struct address_space *mapping = page_mapping(page);
 	unsigned long memcg_flags;
 	struct mem_cgroup *memcg;
-	bool locked;
+	bool locked = false;
 	int ret;
 
 	memcg = mem_cgroup_begin_page_stat(page, &locked, &memcg_flags);
diff --git a/mm/rmap.c b/mm/rmap.c
index 19886fb..4a4dc84 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -1044,7 +1044,7 @@ void page_add_file_rmap(struct page *page)
 {
 	struct mem_cgroup *memcg;
 	unsigned long flags;
-	bool locked;
+	bool locked = false;
 
 	memcg = mem_cgroup_begin_page_stat(page, &locked, &flags);
 	if (atomic_inc_and_test(&page->_mapcount)) {
@@ -1058,7 +1058,7 @@ static void page_remove_file_rmap(struct page *page)
 {
 	struct mem_cgroup *memcg;
 	unsigned long flags;
-	bool locked;
+	bool locked = false;
 
 	memcg = mem_cgroup_begin_page_stat(page, &locked, &flags);
 
-- 
1.7.10.4

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