Re: [RFC PATCH v3 2/13] memory-hotplug : add physical memory hotplugcode to acpi_memory_device_remove
From: Yasuaki Ishimatsu
Date: Tue Jul 17 2012 - 00:52:16 EST
Hi Wen,
2012/07/17 12:32, Wen Congyang wrote:
> 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@xxxxxxxxxx>
>>>>>>> CC: Jiang Liu <liuj97@xxxxxxxxx>
>>>>>>> CC: Len Brown <len.brown@xxxxxxxxx>
>>>>>>> CC: Benjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx>
>>>>>>> CC: Paul Mackerras <paulus@xxxxxxxxx>
>>>>>>> CC: Christoph Lameter <cl@xxxxxxxxx>
>>>>>>> Cc: Minchan Kim <minchan.kim@xxxxxxxxx>
>>>>>>> CC: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
>>>>>>> CC: KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx>
>>>>>>> CC: Wen Congyang <wency@xxxxxxxxxxxxxx>
>>>>>>> Signed-off-by: Yasuaki Ishimatsu <isimatu.yasuaki@xxxxxxxxxxxxxx>
>>>>>>>
>>>>>>> ---
>>>>>>> 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?
It seems you do not understand my concern.
When memory_remove() and offline_pages() run to same memory simultaneously,
offline_pages runs to removed memory.
memory_remove() | offline_pages()
-----------------------------------------------------------
lock_memory_hotplug() |
| wait at lock_memory_hotplug()
remove memory |
unlock_memory_hotplug() |
| wake up and start offline_pages()
| offline page
| => but the memory has already removed
| by memory_remove()
In this case, offline_page() may access removed memory.
Thanks,
Yasuaki Ishimatsu
>
> 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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>>>>>
>>>>>
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