linux-kernel - [PATCH] MM: Fix NR_SECTION_ROOTS == 0 when using using sparsemem extreme.

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Date:	Wed,  5 May 2010 18:02:46 -0300
From:	Marcelo Roberto Jimenez <mroberto@...i.cetuc.puc-rio.br>
To:	mroberto@...i.cetuc.puc-rio.br,
	Andrew Morton <akpm@...ux-foundation.org>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Christoph Lameter <cl@...ux-foundation.org>,
	Mel Gorman <mel@....ul.ie>,
	Minchan Kim <minchan.kim@...il.com>,
	Russell King - ARM Linux <linux@....linux.org.uk>,
	Stephen Rothwell <sfr@...b.auug.org.au>,
	"H. Peter Anvin" <hpa@...or.com>, Yinghai Lu <yinghai@...nel.org>,
	Sergei Shtylyov <sshtylyov@...sta.com>
Cc:	linux@....linux.org.uk, linux-kernel@...r.kernel.org,
	linux-mm@...ck.org
Subject: [PATCH] MM: Fix NR_SECTION_ROOTS == 0 when using using sparsemem extreme.

Got this while compiling for ARM/SA1100:

mm/sparse.c: In function '__section_nr':
mm/sparse.c:135: warning: 'root' is used uninitialized in this function

This patch follows Russell King's suggestion for a new calculation for
NR_SECTION_ROOTS. Thanks also to Sergei Shtylyov for pointing out the
existence of the macro DIV_ROUND_UP.

Signed-off-by: Marcelo Roberto Jimenez <mroberto@...i.cetuc.puc-rio.br>
---
 include/linux/mmzone.h |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index cf9e458..e90ad64 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -972,7 +972,7 @@ struct mem_section {
 #endif
 
 #define SECTION_NR_TO_ROOT(sec)	((sec) / SECTIONS_PER_ROOT)
-#define NR_SECTION_ROOTS	(NR_MEM_SECTIONS / SECTIONS_PER_ROOT)
+#define NR_SECTION_ROOTS	DIV_ROUND_UP(NR_MEM_SECTIONS, SECTIONS_PER_ROOT)
 #define SECTION_ROOT_MASK	(SECTIONS_PER_ROOT - 1)
 
 #ifdef CONFIG_SPARSEMEM_EXTREME
-- 
1.7.1

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