Re: [Patch v4 11/12] memory-hotplug: remove sysfs file of node

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On 11/27/2012 06:00 PM, Wen Congyang wrote:
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@xxxxxxxxxx>
CC: Jiang Liu<liuj97@xxxxxxxxx>
CC: Len Brown<len.brown@xxxxxxxxx>
CC: Christoph Lameter<cl@xxxxxxxxx>
Cc: Minchan Kim<minchan.kim@xxxxxxxxx>
CC: Andrew Morton<akpm@xxxxxxxxxxxxxxxxxxxx>
CC: KOSAKI Motohiro<kosaki.motohiro@xxxxxxxxxxxxxx>
CC: Yasuaki Ishimatsu<isimatu.yasuaki@xxxxxxxxxxxxxx>
Signed-off-by: Wen Congyang<wency@xxxxxxxxxxxxxx>

Reviewed-by: Tang Chen <tangchen@xxxxxxxxxxxxxx>

---
  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 aa97d56..449663e 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>

@@ -1288,7 +1289,58 @@ 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;
@@ -1335,6 +1387,8 @@ repeat:

  	arch_remove_memory(start, size);

+	try_offline_node(nid);
+
  	unlock_memory_hotplug();

  	return 0;
@@ -1344,7 +1398,7 @@ 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;
  }

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