linux-kernel - Re: [PATCH 2/2] page_cgroup array is never stored on reserved pages

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Message-ID: <20110302100418.GC19651@tiehlicka.suse.cz>
Date:	Wed, 2 Mar 2011 11:04:18 +0100
From:	Michal Hocko <mhocko@...e.cz>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	linux-mm@...ck.org, LKML <linux-kernel@...r.kernel.org>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Dave Hansen <dave@...ux.vnet.ibm.com>
Subject: Re: [PATCH 2/2] page_cgroup array is never stored on reserved pages

Hi Andrew,
here is the updated follow up patch refreshed on top of the current
mmotm (2011-02-10-16-26) with a checkpatch cleanup:
--- 
>From b458b849767e41038adce81e59ff30d7d42d7321 Mon Sep 17 00:00:00 2001
From: Michal Hocko <mhocko@...e.cz>
Date: Mon, 28 Feb 2011 10:43:12 +0100
Subject: [PATCH 2/2] page_cgroup array is never stored on reserved pages

KAMEZAWA Hiroyuki noted that free_pages_cgroup doesn't have to check for
PageReserved because we never store the array on reserved pages
(neither alloc_pages_exact nor vmalloc use those pages).

So we can replace the check by a BUG_ON.

Signed-off-by: Michal Hocko <mhocko@...e.cz>
CC: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>

Index: linux-2.6.38-rc4/mm/page_cgroup.c
===================================================================
--- linux-2.6.38-rc4.orig/mm/page_cgroup.c	2011-03-02 10:58:01.000000000 +0100
+++ linux-2.6.38-rc4/mm/page_cgroup.c	2011-03-02 10:58:41.000000000 +0100
@@ -152,11 +152,11 @@ static void free_page_cgroup(void *addr)
 		vfree(addr);
 	} else {
 		struct page *page = virt_to_page(addr);
-		if (!PageReserved(page)) { /* Is bootmem ? */
-			size_t table_size =
-				sizeof(struct page_cgroup) * PAGES_PER_SECTION;
-			free_pages_exact(addr, table_size);
-		}
+		size_t table_size =
+			sizeof(struct page_cgroup) * PAGES_PER_SECTION;
+
+		BUG_ON(PageReserved(page));
+		free_pages_exact(addr, table_size);
 	}
 }
 
-- 
Michal Hocko
SUSE Labs
SUSE LINUX s.r.o.
Lihovarska 1060/12
190 00 Praha 9    
Czech Republic
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