linux-kernel - [ 048/127] mm/ia64: fix a memory block size bug

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Date:	Fri, 28 Sep 2012 13:33:41 -0700
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	alan@...rguk.ukuu.org.uk, Jianguo Wu <wujianguo@...wei.com>,
	Jiang Liu <jiang.liu@...wei.com>,
	"Luck, Tony" <tony.luck@...el.com>, Michal Hocko <mhocko@...e.cz>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: [ 048/127] mm/ia64: fix a memory block size bug

3.0-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Jianguo Wu <wujianguo@...wei.com>

commit 05cf96398e1b6502f9e191291b715c7463c9d5dd upstream.

I found following definition in include/linux/memory.h, in my IA64
platform, SECTION_SIZE_BITS is equal to 32, and MIN_MEMORY_BLOCK_SIZE
will be 0.

  #define MIN_MEMORY_BLOCK_SIZE     (1 << SECTION_SIZE_BITS)

Because MIN_MEMORY_BLOCK_SIZE is int type and length of 32bits,
so MIN_MEMORY_BLOCK_SIZE(1 << 32) will will equal to 0.
Actually when SECTION_SIZE_BITS >= 31, MIN_MEMORY_BLOCK_SIZE will be wrong.
This will cause wrong system memory infomation in sysfs.
I think it should be:

  #define MIN_MEMORY_BLOCK_SIZE     (1UL << SECTION_SIZE_BITS)

And "echo offline > memory0/state" will cause following call trace:

  kernel BUG at mm/memory_hotplug.c:885!
  sh[6455]: bugcheck! 0 [1]
  Pid: 6455, CPU 0, comm:                   sh
  psr : 0000101008526030 ifs : 8000000000000fa4 ip  : [<a0000001008c40f0>]    Not tainted (3.6.0-rc1)
  ip is at offline_pages+0x210/0xee0
  Call Trace:
    show_stack+0x80/0xa0
    show_regs+0x640/0x920
    die+0x190/0x2c0
    die_if_kernel+0x50/0x80
    ia64_bad_break+0x3d0/0x6e0
    ia64_native_leave_kernel+0x0/0x270
    offline_pages+0x210/0xee0
    alloc_pages_current+0x180/0x2a0

Signed-off-by: Jianguo Wu <wujianguo@...wei.com>
Signed-off-by: Jiang Liu <jiang.liu@...wei.com>
Cc: "Luck, Tony" <tony.luck@...el.com>
Reviewed-by: Michal Hocko <mhocko@...e.cz>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 include/linux/memory.h |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/include/linux/memory.h
+++ b/include/linux/memory.h
@@ -20,7 +20,7 @@
 #include <linux/compiler.h>
 #include <linux/mutex.h>
 
-#define MIN_MEMORY_BLOCK_SIZE     (1 << SECTION_SIZE_BITS)
+#define MIN_MEMORY_BLOCK_SIZE     (1UL << SECTION_SIZE_BITS)
 
 struct memory_block {
 	unsigned long start_section_nr;


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