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    SubjectRe: [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@google.com>
    >>>>>> CC: Jiang Liu <liuj97@gmail.com>
    >>>>>> 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/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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    >>>
    >>>
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    >>
    >
    >
    >
    >



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