mm: fix NR_SECTION_ROOTS == 0 when using using sparsemem extreme.
Marcelo Roberto Jimenez [Mon, 24 May 2010 21:32:47 +0000 (14:32 -0700)]
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 <>


index fd55f72..f6f2c50 100644 (file)
@@ -981,7 +981,7 @@ struct mem_section {
 #define SECTION_NR_TO_ROOT(sec)        ((sec) / SECTIONS_PER_ROOT)