linux-kernel - [PATCH]mm/ia64: fix a node distance bug

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Date:	Mon, 20 Aug 2012 14:21:23 +0800
From:	wujianguo <wujianguo106@...il.com>
To:	tony.luck@...el.com, fenghua.yu@...el.com
CC:	linux-ia64@...r.kernel.org, linux-kernel@...r.kernel.org,
	jiang.liu@...wei.com, guohanjun@...wei.com, qiuxishi@...wei.com,
	liuj97@...il.com
Subject: [PATCH]mm/ia64: fix a node distance bug

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

Hi all,
	When doing memory-hot-plug, We found node distance is wrong after offline
a node in IA64 platform. For example system has 4 nodes:
node distances:
node   0   1   2   3
  0:  10  21  21  32
  1:  21  10  32  21
  2:  21  32  10  21
  3:  32  21  21  10

linux-drf:/sys/devices/system/node/node0 # cat distance
10  21  21  32
linux-drf:/sys/devices/system/node/node1 # cat distance
21  10  32  21

After offline node2:
linux-drf:/sys/devices/system/node/node0 # cat distance
10 21 32
linux-drf:/sys/devices/system/node/node1 # cat distance
32 21 32	--------->expected value is: 21  10  21

In arch IA, we have following definition:
extern u8 numa_slit[MAX_NUMNODES * MAX_NUMNODES];
#define node_distance(from,to) (numa_slit[(from) * num_online_nodes() + (to)])

node distance is setup as following:
acpi_numa_arch_fixup()
{
	...
	memset(numa_slit, -1, sizeof(numa_slit));
	for (i = 0; i < slit_table->locality_count; i++) {
		if (!pxm_bit_test(i))
			continue;
		node_from = pxm_to_node(i);
		for (j = 0; j < slit_table->locality_count; j++) {
			if (!pxm_bit_test(j))
				continue;
			node_to = pxm_to_node(j);
			node_distance(node_from, node_to) =
			    slit_table->entry[i * slit_table->locality_count + j];
		}
	}
	...
}
	num_online_nodes() is a variable value, during system boot the return vale is 4,
but after offline node2, the return value is 3, so we read a wrong node distance value.
This patch is trying to fix this bug.

Signed-off-by: Jianguo Wu <wujianguo@...wei.com>
---
 arch/ia64/include/asm/numa.h |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/arch/ia64/include/asm/numa.h b/arch/ia64/include/asm/numa.h
index 6a8a27c..2e27ef1 100644
--- a/arch/ia64/include/asm/numa.h
+++ b/arch/ia64/include/asm/numa.h
@@ -59,7 +59,7 @@ extern struct node_cpuid_s node_cpuid[NR_CPUS];
  */

 extern u8 numa_slit[MAX_NUMNODES * MAX_NUMNODES];
-#define node_distance(from,to) (numa_slit[(from) * num_online_nodes() + (to)])
+#define node_distance(from,to) (numa_slit[(from) * MAX_NUMNODES + (to)])

 extern int paddr_to_nid(unsigned long paddr);

-- 
1.7.6.1



.



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