Re: [PATCH 1/10] memory-hotplug : check whether memory is offline or not when removing memory

Wen Congyang
2012-10-19T10:44:35Z

At 10/06/2012 03:27 AM, KOSAKI Motohiro Wrote:
> On Thu, Oct 4, 2012 at 10:25 PM, Yasuaki Ishimatsu
> <isimatu.yasuaki@jp.fujitsu.com> wrote:
>> When calling remove_memory(), the memory should be offline. If the function
>> is used to online memory, kernel panic may occur.
>>
>> So the patch checks whether memory is offline or not.
>
> You don't explain WHY we need the check.

This patch is no necessary now, because the newest kernel has checked
it.

Thanks
Wen Congyang

>
>
>> CC: David Rientjes <rientjes@google.com>
>> CC: Jiang Liu <liuj97@gmail.com>
>> CC: Len Brown <len.brown@intel.com>
>> 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>
>> Signed-off-by: Wen Congyang <wency@cn.fujitsu.com>
>> Signed-off-by: Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com>
>>
>> ---
>> drivers/base/memory.c | 39 +++++++++++++++++++++++++++++++++++++++
>> include/linux/memory.h | 5 +++++
>> mm/memory_hotplug.c | 17 +++++++++++++++--
>> 3 files changed, 59 insertions(+), 2 deletions(-)
>>
>> Index: linux-3.6/drivers/base/memory.c
>> ===================================================================
>> --- linux-3.6.orig/drivers/base/memory.c 2012-10-04 14:22:57.000000000 +0900
>> +++ linux-3.6/drivers/base/memory.c 2012-10-04 14:45:46.653585860 +0900
>> @@ -70,6 +70,45 @@ void unregister_memory_isolate_notifier(
>> }
>> EXPORT_SYMBOL(unregister_memory_isolate_notifier);
>>
>> +bool is_memblk_offline(unsigned long start, unsigned long size)
>
> Don't use memblk. Usually memblk mean struct numa_meminfo for x86/numa.
> Maybe memory_range_offlined() is better.
>
> And, this function don't take struct memory_block, then this file may be no good
> place.
>
> And you need to write down function comment.
>
>
>> +{
>> + struct memory_block *mem = NULL;
>> + struct mem_section *section;
>> + unsigned long start_pfn, end_pfn;
>> + unsigned long pfn, section_nr;
>> +
>> + start_pfn = PFN_DOWN(start);
>> + end_pfn = PFN_UP(start + size);
>> +
>> + for (pfn = start_pfn; pfn < end_pfn; pfn += PAGES_PER_SECTION) {
>> + 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;
>> +
>> + mem = find_memory_block_hinted(section, mem);
>> + if (!mem)
>> + continue;
>> + if (mem->state == MEM_OFFLINE)
>> + continue;
>> +
>> + kobject_put(&mem->dev.kobj);
>> + return false;
>> + }
>> +
>> + if (mem)
>> + kobject_put(&mem->dev.kobj);
>> +
>> + return true;
>> +}
>> +EXPORT_SYMBOL(is_memblk_offline);
>> +
>> /*
>> * register_memory - Setup a sysfs device for a memory block
>> */
>> Index: linux-3.6/include/linux/memory.h
>> ===================================================================
>> --- linux-3.6.orig/include/linux/memory.h 2012-10-02 18:00:22.000000000 +0900
>> +++ linux-3.6/include/linux/memory.h 2012-10-04 14:44:40.902581028 +0900
>> @@ -106,6 +106,10 @@ static inline int memory_isolate_notify(
>> {
>> return 0;
>> }
>> +static inline bool is_memblk_offline(unsigned long start, unsigned long size)
>> +{
>> + return false;
>> +}
>> #else
>> extern int register_memory_notifier(struct notifier_block *nb);
>> extern void unregister_memory_notifier(struct notifier_block *nb);
>> @@ -120,6 +124,7 @@ 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 is_memblk_offline(unsigned long start, unsigned long size);
>> #define CONFIG_MEM_BLOCK_SIZE (PAGES_PER_SECTION<<PAGE_SHIFT)
>> enum mem_add_context { BOOT, HOTPLUG };
>> #endif /* CONFIG_MEMORY_HOTPLUG_SPARSE */
>> Index: linux-3.6/mm/memory_hotplug.c
>> ===================================================================
>> --- linux-3.6.orig/mm/memory_hotplug.c 2012-10-04 14:31:08.000000000 +0900
>> +++ linux-3.6/mm/memory_hotplug.c 2012-10-04 14:58:22.449687986 +0900
>> @@ -1045,8 +1045,21 @@ int offline_memory(u64 start, u64 size)
>>
>> int remove_memory(int nid, u64 start, u64 size)
>> {
>
> Your remove_memory() don't remove anything. that's strange.
>
>
>> - /* It is not implemented yet*/
>> - return 0;
>> + int ret = 0;
>> + lock_memory_hotplug();
>> + /*
>> + * The memory might become online by other task, even if you offine it.
>> + * So we check whether the memory has been onlined or not.
>> + */
>> + if (!is_memblk_offline(start, size)) {
>> + pr_warn("memory removing [mem %#010llx-%#010llx] failed, "
>> + "because the memmory range is online\n",
>> + start, start + size);
>
> No good warning. You should output which memory block can't be
> offlined, I think.
>
>
>> + ret = -EAGAIN;
>> + }
>> +
>> + unlock_memory_hotplug();
>> + return ret;
>> }
>> EXPORT_SYMBOL_GPL(remove_memory);
>> #else
>>
>> --
>> To unsubscribe, send a message with 'unsubscribe linux-mm' in
>> the body to majordomo@kvack.org. For more info on Linux MM,
>> see: http://www.linux-mm.org/ .
>> Don't email: email@kvack.org