I updated the patch and attached it on the mail.

2012/11/01 18:44, Wen Congyang wrote:

quoted

This patch introduces a new function try_offline_node() to
remove sysfs file of node when all memory sections of this
node are removed. If some memory sections of this node are
not removed, this function does nothing.

CC: David Rientjes <rientjes@google.com>
CC: Jiang Liu <redacted>
CC: Len Brown <redacted>
CC: Christoph Lameter <redacted>
Cc: Minchan Kim <redacted>
CC: Andrew Morton <akpm@linux-foundation.org>
CC: KOSAKI Motohiro <redacted>
CC: Yasuaki Ishimatsu <redacted>
Signed-off-by: Wen Congyang <redacted>
---
  drivers/acpi/acpi_memhotplug.c |  8 +++++-
  include/linux/memory_hotplug.h |  2 +-
  mm/memory_hotplug.c            | 58 ++++++++++++++++++++++++++++++++++++++++--
  3 files changed, 64 insertions(+), 4 deletions(-)

diff --git a/drivers/acpi/acpi_memhotplug.c b/drivers/acpi/acpi_memhotplug.c
index 24c807f..0780f99 100644
--- a/drivers/acpi/acpi_memhotplug.c
+++ b/drivers/acpi/acpi_memhotplug.c

@@ -310,7 +310,9 @@ static int acpi_memory_disable_device(struct acpi_memory_device *mem_device)
  {
  	int result;
  	struct acpi_memory_info *info, *n;
+	int node;
  
+	node = acpi_get_node(mem_device->device->handle);
  
  	/*
  	 * Ask the VM to offline this memory range.

@@ -318,7 +320,11 @@ static int acpi_memory_disable_device(struct acpi_memory_device *mem_device)
  	 */
  	list_for_each_entry_safe(info, n, &mem_device->res_list, list) {
  		if (info->enabled) {
-			result = remove_memory(info->start_addr, info->length);
+			if (node < 0)
+				node = memory_add_physaddr_to_nid(
+					info->start_addr);
+			result = remove_memory(node, info->start_addr,
+				info->length);
  			if (result)
  				return result;
  		}

diff --git a/include/linux/memory_hotplug.h b/include/linux/memory_hotplug.h
index d4c4402..7b4cfe6 100644
--- a/include/linux/memory_hotplug.h
+++ b/include/linux/memory_hotplug.h

@@ -231,7 +231,7 @@ extern int arch_add_memory(int nid, u64 start, u64 size);
  extern int offline_pages(unsigned long start_pfn, unsigned long nr_pages);
  extern int offline_memory_block(struct memory_block *mem);
  extern bool is_memblock_offlined(struct memory_block *mem);
-extern int remove_memory(u64 start, u64 size);
+extern int remove_memory(int node, u64 start, u64 size);
  extern int sparse_add_one_section(struct zone *zone, unsigned long start_pfn,
  								int nr_pages);
  extern void sparse_remove_one_section(struct zone *zone, struct mem_section *ms);

diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index 7bcced0..d965da3 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c

@@ -29,6 +29,7 @@
  #include <linux/suspend.h>
  #include <linux/mm_inline.h>
  #include <linux/firmware-map.h>
+#include <linux/stop_machine.h>
  
  #include <asm/tlbflush.h>
  

@@ -1299,7 +1300,58 @@ static int is_memblock_offlined_cb(struct memory_block *mem, void *arg)
  	return ret;
  }
  
-int __ref remove_memory(u64 start, u64 size)
+static int check_cpu_on_node(void *data)
+{
+	struct pglist_data *pgdat = data;
+	int cpu;
+
+	for_each_present_cpu(cpu) {
+		if (cpu_to_node(cpu) == pgdat->node_id)
+			/*
+			 * the cpu on this node isn't removed, and we can't
+			 * offline this node.
+			 */
+			return -EBUSY;
+	}
+
+	return 0;
+}
+
+/* offline the node if all memory sections of this node are removed */
+static void try_offline_node(int nid)
+{
+	unsigned long start_pfn = NODE_DATA(nid)->node_start_pfn;
+	unsigned long end_pfn = start_pfn + NODE_DATA(nid)->node_spanned_pages;
+	unsigned long pfn;
+
+	for (pfn = start_pfn; pfn < end_pfn; pfn += PAGES_PER_SECTION) {
+		unsigned long section_nr = pfn_to_section_nr(pfn);
+
+		if (!present_section_nr(section_nr))
+			continue;
+
+		if (pfn_to_nid(pfn) != nid)
+			continue;
+
+		/*
+		 * some memory sections of this node are not removed, and we
+		 * can't offline node now.
+		 */
+		return;
+	}
+
+	if (stop_machine(check_cpu_on_node, NODE_DATA(nid), NULL))
+		return;
+
+	/*
+	 * all memory/cpu of this node are removed, we can offline this
+	 * node now.
+	 */
+	node_set_offline(nid);
+	unregister_one_node(nid);
+}
+
+int __ref remove_memory(int nid, u64 start, u64 size)
  {
  	unsigned long start_pfn, end_pfn;
  	int ret = 0;

@@ -1346,6 +1398,8 @@ repeat:
  
  	arch_remove_memory(start, size);
  
+	try_offline_node(nid);
+
  	unlock_memory_hotplug();
  
  	return 0;

@@ -1355,7 +1409,7 @@ int offline_pages(unsigned long start_pfn, unsigned long nr_pages)
  {
  	return -EINVAL;
  }
-int remove_memory(u64 start, u64 size)
+int remove_memory(int nid, u64 start, u64 size)
  {
  	return -EINVAL;
  }

---
This patch introduces a new function try_offline_node() to
remove sysfs file of node when all memory sections of this
node are removed. If some memory sections of this node are
not removed, this function does nothing.

CC: David Rientjes <rientjes@google.com>
CC: Jiang Liu <redacted>
CC: Len Brown <redacted>
CC: Christoph Lameter <redacted>
Cc: Minchan Kim <redacted>
CC: Andrew Morton <akpm@linux-foundation.org>
CC: KOSAKI Motohiro <redacted>
CC: Yasuaki Ishimatsu <redacted>
Signed-off-by: Wen Congyang <redacted>
---
 drivers/acpi/acpi_memhotplug.c |    9 +++++-
 include/linux/memory_hotplug.h |    2 -
 mm/memory_hotplug.c            |   58 +++++++++++++++++++++++++++++++++++++++--
 3 files changed, 65 insertions(+), 4 deletions(-)

Index: linux-3.7-rc6/drivers/acpi/acpi_memhotplug.c
===================================================================

--- linux-3.7-rc6.orig/drivers/acpi/acpi_memhotplug.c	2012-11-19 16:16:55.161912688 +0900
+++ linux-3.7-rc6/drivers/acpi/acpi_memhotplug.c	2012-11-19 16:17:05.346912109 +0900

@@ -295,6 +295,9 @@ static int acpi_memory_remove_memory(str
 {
 	int result = 0;
 	struct acpi_memory_info *info, *n;
+	int node;
+
+	node = acpi_get_node(mem_device->device->handle);
 
 	list_for_each_entry_safe(info, n, &mem_device->res_list, list) {
 		if (info->failed)

@@ -308,7 +311,11 @@ static int acpi_memory_remove_memory(str
 			 */
 			return -EBUSY;
 
-		result = remove_memory(info->start_addr, info->length);
+		if (node < 0)
+			node = memory_add_physaddr_to_nid(
+				info->start_addr);
+		result = remove_memory(node, info->start_addr,
+			info->length);
 		if (result)
 			return result;
 

Index: linux-3.7-rc6/include/linux/memory_hotplug.h
===================================================================

--- linux-3.7-rc6.orig/include/linux/memory_hotplug.h	2012-11-19 16:16:55.167912687 +0900
+++ linux-3.7-rc6/include/linux/memory_hotplug.h	2012-11-19 16:17:05.348912109 +0900

@@ -242,7 +242,7 @@ extern int arch_add_memory(int nid, u64 
 extern int offline_pages(unsigned long start_pfn, unsigned long nr_pages);
 extern int offline_memory_block(struct memory_block *mem);
 extern bool is_memblock_offlined(struct memory_block *mem);
-extern int remove_memory(u64 start, u64 size);
+extern int remove_memory(int node, u64 start, u64 size);
 extern int sparse_add_one_section(struct zone *zone, unsigned long start_pfn,
 								int nr_pages);
 extern void sparse_remove_one_section(struct zone *zone, struct mem_section *ms);

Index: linux-3.7-rc6/mm/memory_hotplug.c
===================================================================

--- linux-3.7-rc6.orig/mm/memory_hotplug.c	2012-11-19 16:16:55.164912687 +0900
+++ linux-3.7-rc6/mm/memory_hotplug.c	2012-11-19 16:17:05.356912108 +0900

@@ -29,6 +29,7 @@
 #include <linux/suspend.h>
 #include <linux/mm_inline.h>
 #include <linux/firmware-map.h>
+#include <linux/stop_machine.h>
 
 #include <asm/tlbflush.h>
 

@@ -1652,7 +1653,58 @@ static int is_memblock_offlined_cb(struc
 	return ret;
 }
 
-int __ref remove_memory(u64 start, u64 size)
+static int check_cpu_on_node(void *data)
+{
+	struct pglist_data *pgdat = data;
+	int cpu;
+
+	for_each_present_cpu(cpu) {
+		if (cpu_to_node(cpu) == pgdat->node_id)
+			/*
+			 * the cpu on this node isn't removed, and we can't
+			 * offline this node.
+			 */
+			return -EBUSY;
+	}
+
+	return 0;
+}
+
+/* offline the node if all memory sections of this node are removed */
+static void try_offline_node(int nid)
+{
+	unsigned long start_pfn = NODE_DATA(nid)->node_start_pfn;
+	unsigned long end_pfn = start_pfn + NODE_DATA(nid)->node_spanned_pages;
+	unsigned long pfn;
+
+	for (pfn = start_pfn; pfn < end_pfn; pfn += PAGES_PER_SECTION) {
+		unsigned long section_nr = pfn_to_section_nr(pfn);
+
+		if (!present_section_nr(section_nr))
+			continue;
+
+		if (pfn_to_nid(pfn) != nid)
+			continue;
+
+		/*
+		 * some memory sections of this node are not removed, and we
+		 * can't offline node now.
+		 */
+		return;
+	}
+
+	if (stop_machine(check_cpu_on_node, NODE_DATA(nid), NULL))
+		return;
+
+	/*
+	 * all memory/cpu of this node are removed, we can offline this
+	 * node now.
+	 */
+	node_set_offline(nid);
+	unregister_one_node(nid);
+}
+
+int __ref remove_memory(int nid, u64 start, u64 size)
 {
 	unsigned long start_pfn, end_pfn;
 	int ret = 0;

@@ -1699,6 +1751,8 @@ repeat:
 
 	arch_remove_memory(start, size);
 
+	try_offline_node(nid);
+
 	unlock_memory_hotplug();
 
 	return 0;

@@ -1708,7 +1762,7 @@ int offline_pages(unsigned long start_pf
 {
 	return -EINVAL;
 }
-int remove_memory(u64 start, u64 size)
+int remove_memory(int nid, u64 start, u64 size)
 {
 	return -EINVAL;
 }