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    SubjectRe: [RFC PATCH 2/12] memory-hogplug : check memory offline in offline_pages
    On 06/27/2012 01:44 PM, Yasuaki Ishimatsu wrote:
    > 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().
    >
    > CC: Len Brown <len.brown@intel.com>
    > CC: Benjamin Herrenschmidt <benh@kernel.crashing.org>
    > CC: Paul Mackerras <paulus@samba.org>
    > CC: Christoph Lameter <cl@linux.com>
    > Cc: Minchan Kim <minchan.kim@gmail.com>
    > CC: Andrew Morton <akpm@linux-foundation.org>
    > CC: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
    > CC: Wen Congyang <wency@cn.fujitsu.com>
    > Signed-off-by: Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com>
    >
    > ---
    > 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);
    Is it possible for __nr_to_section return NULL here?

    > + mem = find_memory_block(section);
    > + if (!mem)
    > + continue;
    > + if (mem->state == MEM_OFFLINE)
    > + continue;
    > + return false;
    > + }
    > +
    > + return true;
    > +}
    Need a put_dev(&mem->dev) for the last memory block device handled before return.

    > +
    > /*
    > * 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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    >




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