From 0faa56389c793cda7f967117415717bbab24fe4e Mon Sep 17 00:00:00 2001 From: Marcelo Roberto Jimenez Date: Mon, 24 May 2010 14:32:47 -0700 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. Atsushi Nemoto observed: : This fix doesn't just silence the warning - it fixes a real problem. : : Without this fix, mem_section[] might have 0 size so mem_section[0] : will share other variable area. For example, I got: : : c030c700 b __warned.16478 : c030c700 B mem_section : c030c701 b __warned.16483 : : This might cause very strange behavior. Your patch actually fixes it. Signed-off-by: Marcelo Roberto Jimenez Cc: Atsushi Nemoto Cc: KOSAKI Motohiro Cc: Christoph Lameter Cc: Mel Gorman Cc: Minchan Kim Cc: Yinghai Lu Cc: Sergei Shtylyov Cc: Russell King Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/mmzone.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h index fd55f72..f6f2c50 100644 --- a/include/linux/mmzone.h +++ b/include/linux/mmzone.h @@ -981,7 +981,7 @@ 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 -- 2.7.4