linux-kernel - [PATCH] kmemleak: Annotate false positive in init_section_page

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Message-ID: <20100715150117.21293.45752.stgit@e102109-lin.cambridge.arm.com>
Date:	Thu, 15 Jul 2010 16:01:17 +0100
From:	Catalin Marinas <catalin.marinas@....com>
To:	linux-kernel@...r.kernel.org
Cc:	Adrien Dessemond <adrien.dessemond@...il.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Pekka Enberg <penberg@...helsinki.fi>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Subject: [PATCH] kmemleak: Annotate false positive in
 init_section_page_cgroup()

The pointer to the page_cgroup table allocated in
init_section_page_cgroup() is stored in section->page_cgroup as (base -
pfn). Since this value does not point to the beginning or inside the
allocated memory block, kmemleak reports a false positive.

Signed-off-by: Catalin Marinas <catalin.marinas@....com>
Reported-by: Adrien Dessemond <adrien.dessemond@...il.com>
Cc: Pekka Enberg <penberg@...helsinki.fi>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
---
 mm/page_cgroup.c |    7 +++++++
 1 files changed, 7 insertions(+), 0 deletions(-)

diff --git a/mm/page_cgroup.c b/mm/page_cgroup.c
index 6c00814..5bffada 100644
--- a/mm/page_cgroup.c
+++ b/mm/page_cgroup.c
@@ -9,6 +9,7 @@
 #include <linux/vmalloc.h>
 #include <linux/cgroup.h>
 #include <linux/swapops.h>
+#include <linux/kmemleak.h>
 
 static void __meminit
 __init_page_cgroup(struct page_cgroup *pc, unsigned long pfn)
@@ -126,6 +127,12 @@ static int __init_refok init_section_page_cgroup(unsigned long pfn)
 			if (!base)
 				base = vmalloc(table_size);
 		}
+		/*
+		 * The value stored in section->page_cgroup is (base - pfn)
+		 * and it does not point to the memory block allocated above,
+		 * causing kmemleak false positives.
+		 */
+		kmemleak_not_leak(base);
 	} else {
 		/*
  		 * We don't have to allocate page_cgroup again, but

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