The patch titled
mm: fix NR_SECTION_ROOTS == 0 when using using sparsemem extreme.
has been added to the -mm tree. Its filename is
mm-fix-nr_section_roots-==-0-when-using-using-sparsemem-extreme.patch
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Subject: mm: fix NR_SECTION_ROOTS == 0 when using using sparsemem extreme.
From: Marcelo Roberto Jimenez <mroberto@xxxxxxxxxxxxxxxxxxxxx>
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 <mroberto@xxxxxxxxxxxxxxxxxxxxx>
Cc: Atsushi Nemoto <anemo@xxxxxxxxxxxxx>
Cc: KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx>
Cc: Christoph Lameter <cl@xxxxxxxxxxxxxxxxxxxx>
Cc: Mel Gorman <mel@xxxxxxxxx>
Cc: Minchan Kim <minchan.kim@xxxxxxxxx>
Cc: Yinghai Lu <yinghai@xxxxxxxxxx>
Cc: Sergei Shtylyov <sshtylyov@xxxxxxxxxx>
Cc: Russell King <rmk@xxxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/mmzone.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff -puN include/linux/mmzone.h~mm-fix-nr_section_roots-==-0-when-using-using-sparsemem-extreme include/linux/mmzone.h
--- a/include/linux/mmzone.h~mm-fix-nr_section_roots-==-0-when-using-using-sparsemem-extreme
+++ a/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
_
Patches currently in -mm which might be from mroberto@xxxxxxxxxxxxxxxxxxxxx are
mm-fix-nr_section_roots-==-0-when-using-using-sparsemem-extreme.patch
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