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Message-ID: <5004DCC2.4030905@cn.fujitsu.com>
Date: Tue, 17 Jul 2012 11:32:18 +0800
From: Wen Congyang <wency@...fujitsu.com>
To: Yasuaki Ishimatsu <isimatu.yasuaki@...fujitsu.com>
CC: linux-mm@...ck.org, linux-kernel@...r.kernel.org,
linuxppc-dev@...ts.ozlabs.org, linux-acpi@...r.kernel.org,
rientjes@...gle.com, liuj97@...il.com, len.brown@...el.com,
benh@...nel.crashing.org, paulus@...ba.org, cl@...ux.com,
minchan.kim@...il.com, akpm@...ux-foundation.org,
kosaki.motohiro@...fujitsu.com
Subject: Re: [RFC PATCH v3 2/13] memory-hotplug : add physical memory hotplug
code to acpi_memory_device_remove
At 07/17/2012 11:08 AM, Yasuaki Ishimatsu Wrote:
> Hi Wen,
>
> 2012/07/17 11:32, Wen Congyang wrote:
>> At 07/17/2012 09:54 AM, Yasuaki Ishimatsu Wrote:
>>> Hi Wen,
>>>
>>> 2012/07/17 10:44, Yasuaki Ishimatsu wrote:
>>>> Hi Wen,
>>>>
>>>> 2012/07/13 12:35, Wen Congyang wrote:
>>>>> At 07/09/2012 06:24 PM, Yasuaki Ishimatsu Wrote:
>>>>>> acpi_memory_device_remove() has been prepared to remove physical memory.
>>>>>> But, the function only frees acpi_memory_device currentlry.
>>>>>>
>>>>>> The patch adds following functions into acpi_memory_device_remove():
>>>>>> - offline memory
>>>>>> - remove physical memory (only return -EBUSY)
>>>>>> - free acpi_memory_device
>>>>>>
>>>>>> CC: David Rientjes <rientjes@...gle.com>
>>>>>> CC: Jiang Liu <liuj97@...il.com>
>>>>>> CC: Len Brown <len.brown@...el.com>
>>>>>> CC: Benjamin Herrenschmidt <benh@...nel.crashing.org>
>>>>>> CC: Paul Mackerras <paulus@...ba.org>
>>>>>> CC: Christoph Lameter <cl@...ux.com>
>>>>>> Cc: Minchan Kim <minchan.kim@...il.com>
>>>>>> CC: Andrew Morton <akpm@...ux-foundation.org>
>>>>>> CC: KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
>>>>>> CC: Wen Congyang <wency@...fujitsu.com>
>>>>>> Signed-off-by: Yasuaki Ishimatsu <isimatu.yasuaki@...fujitsu.com>
>>>>>>
>>>>>> ---
>>>>>> drivers/acpi/acpi_memhotplug.c | 26 +++++++++++++++++++++++++-
>>>>>> drivers/base/memory.c | 39 +++++++++++++++++++++++++++++++++++++++
>>>>>> include/linux/memory.h | 5 +++++
>>>>>> include/linux/memory_hotplug.h | 1 +
>>>>>> mm/memory_hotplug.c | 8 ++++++++
>>>>>> 5 files changed, 78 insertions(+), 1 deletion(-)
>>>>>>
>>>>>> Index: linux-3.5-rc6/drivers/acpi/acpi_memhotplug.c
>>>>>> ===================================================================
>>>>>> --- linux-3.5-rc6.orig/drivers/acpi/acpi_memhotplug.c 2012-07-09 18:08:29.946888653 +0900
>>>>>> +++ linux-3.5-rc6/drivers/acpi/acpi_memhotplug.c 2012-07-09 18:08:43.470719531 +0900
>>>>>> @@ -29,6 +29,7 @@
>>>>>> #include <linux/module.h>
>>>>>> #include <linux/init.h>
>>>>>> #include <linux/types.h>
>>>>>> +#include <linux/memory.h>
>>>>>> #include <linux/memory_hotplug.h>
>>>>>> #include <linux/slab.h>
>>>>>> #include <acpi/acpi_drivers.h>
>>>>>> @@ -452,12 +453,35 @@ static int acpi_memory_device_add(struct
>>>>>> static int acpi_memory_device_remove(struct acpi_device *device, int type)
>>>>>> {
>>>>>> struct acpi_memory_device *mem_device = NULL;
>>>>>> -
>>>>>> + struct acpi_memory_info *info, *tmp;
>>>>>> + int result;
>>>>>> + int node;
>>>>>>
>>>>>> if (!device || !acpi_driver_data(device))
>>>>>> return -EINVAL;
>>>>>>
>>>>>> mem_device = acpi_driver_data(device);
>>>>>> +
>>>>>> + node = acpi_get_node(mem_device->device->handle);
>>>>>> +
>>>>>> + list_for_each_entry_safe(info, tmp, &mem_device->res_list, list) {
>>>>>> + if (!info->enabled)
>>>>>> + continue;
>>>>>> +
>>>>>> + if (!is_memblk_offline(info->start_addr, info->length)) {
>>>>>> + result = offline_memory(info->start_addr, info->length);
>>>>>> + if (result)
>>>>>> + return result;
>>>>>> + }
>>>>>> +
>>>>>> + result = remove_memory(node, info->start_addr, info->length);
>>>>>
>>>>> The user may online the memory between offline_memory() and remove_memory().
>>>>> So I think we should lock memory hotplug before check the memory's status
>>>>> and release it after remove_memory().
>>>>
>>>> How about get "mem_block->state_mutex" of removed memory? When offlining
>>>> memory, we need to change "memory_block->state" into "MEM_OFFLINE".
>>>> In this case, we get mem_block->state_mutex. So I think the mutex lock
>>>> is beneficial.
>>>
>>> It is not good idea since remove_memory frees mem_block structure...
>>> Do you have any ideas?
>>
>> Hmm, split offline_memory() to 2 functions: offline_pages() and __offline_pages()
>>
>> offline_pages()
>> lock_memory_hotplug();
>> __offline_pages();
>> unlock_memory_hotplug();
>>
>> and implement remove_memory() like this:
>> remove_memory()
>> lock_memory_hotplug()
>> if (!is_memblk_offline()) {
>> __offline_pages();
>> }
>> // cleanup
>> unlock_memory_hotplug();
>>
>> What about this?
>
> I also thought about it once. But a problem remains. Current offilne_pages()
> cannot realize the memory has been removed by remove_memory(). So even if
> protecting the race by lock_memory_hotplug(), offline_pages() can offline
> the removed memory. offline_pages() should have the means to know the memory
> was removed. But I don't have good idea.
We can not online/offline part of memory block, so what about this?
remove_memory()
lock_memory_hotplug()
for each memory block:
if (!is_memblk_offline()) {
__offline_pages();
}
// cleanup
unlock_memory_hotplug();
Thanks
Wen Congyang
>
> Thanks,
> Yasuaki Ishimatsu
>
>>
>> Thanks
>> Wen Congyang
>>>
>>> Thanks,
>>> Yasuaki Ishimatsu
>>>
>>>> Thanks,
>>>> Yasuaki Ishimatsu
>>>>
>>>>>
>>>>> Thanks
>>>>> Wen Congyang
>>>>>
>>>>>> + if (result)
>>>>>> + return result;
>>>>>> +
>>>>>> + list_del(&info->list);
>>>>>> + kfree(info);
>>>>>> + }
>>>>>> +
>>>>>> kfree(mem_device);
>>>>>>
>>>>>> return 0;
>>>>>> Index: linux-3.5-rc6/include/linux/memory_hotplug.h
>>>>>> ===================================================================
>>>>>> --- linux-3.5-rc6.orig/include/linux/memory_hotplug.h 2012-07-09 18:08:29.955888542 +0900
>>>>>> +++ linux-3.5-rc6/include/linux/memory_hotplug.h 2012-07-09 18:08:43.471719518 +0900
>>>>>> @@ -233,6 +233,7 @@ static inline int is_mem_section_removab
>>>>>> extern int mem_online_node(int nid);
>>>>>> extern int add_memory(int nid, u64 start, u64 size);
>>>>>> extern int arch_add_memory(int nid, u64 start, u64 size);
>>>>>> +extern int remove_memory(int nid, u64 start, u64 size);
>>>>>> extern int offline_memory(u64 start, u64 size);
>>>>>> extern int sparse_add_one_section(struct zone *zone, unsigned long start_pfn,
>>>>>> int nr_pages);
>>>>>> Index: linux-3.5-rc6/mm/memory_hotplug.c
>>>>>> ===================================================================
>>>>>> --- linux-3.5-rc6.orig/mm/memory_hotplug.c 2012-07-09 18:08:29.953888567 +0900
>>>>>> +++ linux-3.5-rc6/mm/memory_hotplug.c 2012-07-09 18:08:43.476719455 +0900
>>>>>> @@ -659,6 +659,14 @@ out:
>>>>>> }
>>>>>> EXPORT_SYMBOL_GPL(add_memory);
>>>>>>
>>>>>> +int remove_memory(int nid, u64 start, u64 size)
>>>>>> +{
>>>>>> + return -EBUSY;
>>>>>> +
>>>>>> +}
>>>>>> +EXPORT_SYMBOL_GPL(remove_memory);
>>>>>> +
>>>>>> +
>>>>>> #ifdef CONFIG_MEMORY_HOTREMOVE
>>>>>> /*
>>>>>> * A free page on the buddy free lists (not the per-cpu lists) has PageBuddy
>>>>>> Index: linux-3.5-rc6/drivers/base/memory.c
>>>>>> ===================================================================
>>>>>> --- linux-3.5-rc6.orig/drivers/base/memory.c 2012-07-09 18:08:29.947888640 +0900
>>>>>> +++ linux-3.5-rc6/drivers/base/memory.c 2012-07-09 18:10:54.880076739 +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)
>>>>>> +{
>>>>>> + 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 = start_pfn + PFN_DOWN(start);
>>>>>> +
>>>>>> + 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-3.5-rc6/include/linux/memory.h
>>>>>> ===================================================================
>>>>>> --- linux-3.5-rc6.orig/include/linux/memory.h 2012-07-08 09:23:56.000000000 +0900
>>>>>> +++ linux-3.5-rc6/include/linux/memory.h 2012-07-09 18:08:43.484719355 +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 */
>>>>>>
>>>>>>
>>>>>
>>>>> --
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>>>>> see: http://www.linux-mm.org/ .
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>>>>>
>>>>
>>>>
>>>>
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