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SubjectRe: [PATCH v5 02/14] memory-hotplug: check whether all memory blocks are offlined or not when removing memory
(2012/12/24 21:09), Tang Chen wrote:
> From: Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com>
>
> We remove the memory like this:
> 1. lock memory hotplug
> 2. offline a memory block
> 3. unlock memory hotplug
> 4. repeat 1-3 to offline all memory blocks
> 5. lock memory hotplug
> 6. remove memory(TODO)
> 7. unlock memory hotplug
>
> All memory blocks must be offlined before removing memory. But we don't hold
> the lock in the whole operation. So we should check whether all memory blocks
> are offlined before step6. Otherwise, kernel maybe panicked.
>
> Signed-off-by: Wen Congyang <wency@cn.fujitsu.com>
> Signed-off-by: Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com>

Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>

a nitpick below.

> ---
> drivers/base/memory.c | 6 +++++
> include/linux/memory_hotplug.h | 1 +
> mm/memory_hotplug.c | 47 ++++++++++++++++++++++++++++++++++++++++
> 3 files changed, 54 insertions(+), 0 deletions(-)
>
> diff --git a/drivers/base/memory.c b/drivers/base/memory.c
> index 987604d..8300a18 100644
> --- a/drivers/base/memory.c
> +++ b/drivers/base/memory.c
> @@ -693,6 +693,12 @@ int offline_memory_block(struct memory_block *mem)
> return ret;
> }
>
> +/* return true if the memory block is offlined, otherwise, return false */
> +bool is_memblock_offlined(struct memory_block *mem)
> +{
> + return mem->state == MEM_OFFLINE;
> +}
> +
> /*
> * Initialize the sysfs support for memory devices...
> */
> diff --git a/include/linux/memory_hotplug.h b/include/linux/memory_hotplug.h
> index 4a45c4e..8dd0950 100644
> --- a/include/linux/memory_hotplug.h
> +++ b/include/linux/memory_hotplug.h
> @@ -247,6 +247,7 @@ extern int add_memory(int nid, u64 start, u64 size);
> 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 sparse_add_one_section(struct zone *zone, unsigned long start_pfn,
> int nr_pages);
> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
> index 62e04c9..d43d97b 100644
> --- a/mm/memory_hotplug.c
> +++ b/mm/memory_hotplug.c
> @@ -1430,6 +1430,53 @@ repeat:
> goto repeat;
> }
>
> + lock_memory_hotplug();
> +
> + /*
> + * we have offlined all memory blocks like this:
> + * 1. lock memory hotplug
> + * 2. offline a memory block
> + * 3. unlock memory hotplug
> + *
> + * repeat step1-3 to offline the memory block. All memory blocks
> + * must be offlined before removing memory. But we don't hold the
> + * lock in the whole operation. So we should check whether all
> + * memory blocks are offlined.
> + */
> +
> + for (pfn = start_pfn; pfn < end_pfn; pfn += PAGES_PER_SECTION) {

I prefer adding mem = NULL at the start of this for().

> + section_nr = pfn_to_section_nr(pfn);
> + if (!present_section_nr(section_nr))
> + continue;
> +
> + section = __nr_to_section(section_nr);
> + /* same memblock? */
> + if (mem)
> + if ((section_nr >= mem->start_section_nr) &&
> + (section_nr <= mem->end_section_nr))
> + continue;
> +

Thanks,
-Kame




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