Hi Wen,

2012/06/27 17:49, Wen Congyang wrote:

At 06/27/2012 01:44 PM, Yasuaki Ishimatsu Wrote:

quoted

When offline_pages() is called to offlined memory, the function fails since
all memory has been offlined. In this case, the function should succeed.
The patch adds the check function into offline_pages().

You miss such case: some pages are online, while some pages are offline.
offline_pages() will fail too in such case.

You are right. But current code fails, when the function is called to offline
memory. In this case, the function should succeed. So the patch confirms
whether the memory was offlined or not. And if memory has already been
offlined, offline_pages return 0.

Thanks,
Yasuaki Ishimatsu

Thanks
Wen Congyang

quoted

CC: Len Brown <redacted>
CC: Benjamin Herrenschmidt <benh@kernel.crashing.org>
CC: Paul Mackerras <redacted>
CC: Christoph Lameter <redacted>
Cc: Minchan Kim <redacted>
CC: Andrew Morton <akpm@linux-foundation.org>
CC: KOSAKI Motohiro <redacted>
CC: Wen Congyang <redacted>
Signed-off-by: Yasuaki Ishimatsu <redacted>

---
  drivers/base/memory.c  |   20 ++++++++++++++++++++
  include/linux/memory.h |    1 +
  mm/memory_hotplug.c    |    5 +++++
  3 files changed, 26 insertions(+)

Index: linux-3.5-rc4/drivers/base/memory.c
===================================================================

--- linux-3.5-rc4.orig/drivers/base/memory.c	2012-06-26 13:28:16.726211752 +0900
+++ linux-3.5-rc4/drivers/base/memory.c	2012-06-26 13:34:22.423639904 +0900

@@ -70,6 +70,26 @@ void unregister_memory_isolate_notifier(
  }
  EXPORT_SYMBOL(unregister_memory_isolate_notifier);

+bool memory_is_offline(unsigned long start_pfn, unsigned long end_pfn)
+{
+	struct memory_block *mem;
+	struct mem_section *section;
+	unsigned long pfn, section_nr;
+
+	for (pfn = start_pfn; pfn < end_pfn; pfn += PAGES_PER_SECTION) {
+		section_nr = pfn_to_section_nr(pfn);
+		section = __nr_to_section(section_nr);
+		mem = find_memory_block(section);
+		if (!mem)
+			continue;
+		if (mem->state == MEM_OFFLINE)
+			continue;
+		return false;
+	}
+
+	return true;
+}
+
  /*
   * register_memory - Setup a sysfs device for a memory block
   */

Index: linux-3.5-rc4/include/linux/memory.h
===================================================================

--- linux-3.5-rc4.orig/include/linux/memory.h	2012-06-25 04:53:04.000000000 +0900
+++ linux-3.5-rc4/include/linux/memory.h	2012-06-26 13:34:22.424639891 +0900

@@ -120,6 +120,7 @@ extern int memory_isolate_notify(unsigne
  extern struct memory_block *find_memory_block_hinted(struct mem_section *,
  							struct memory_block *);
  extern struct memory_block *find_memory_block(struct mem_section *);
+extern bool memory_is_offline(unsigned long start_pfn, unsigned long end_pfn);
  #define CONFIG_MEM_BLOCK_SIZE	(PAGES_PER_SECTION<<PAGE_SHIFT)
  enum mem_add_context { BOOT, HOTPLUG };
  #endif /* CONFIG_MEMORY_HOTPLUG_SPARSE */

Index: linux-3.5-rc4/mm/memory_hotplug.c
===================================================================

--- linux-3.5-rc4.orig/mm/memory_hotplug.c	2012-06-26 13:28:16.743211538 +0900
+++ linux-3.5-rc4/mm/memory_hotplug.c	2012-06-26 13:48:38.264940468 +0900

@@ -887,6 +887,11 @@ static int __ref offline_pages(unsigned

  	lock_memory_hotplug();

+	if (memory_is_offline(start_pfn, end_pfn)) {
+		ret = 0;
+		goto out;
+	}
+
  	zone = page_zone(pfn_to_page(start_pfn));
  	node = zone_to_nid(zone);
  	nr_pages = end_pfn - start_pfn;

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