Re: [RFC PATCH v2 2/13] memory-hotplug : add physical memory hotplug code to acpi_memory_device_remove

Yasuaki Ishimatsu
2012-07-03T07:40:59Z

Hi Wen,

2012/07/03 15:21, Wen Congyang wrote:
> At 07/03/2012 01:54 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>
>> Signed-off-by: Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com>
>>
>> ---
>> drivers/acpi/acpi_memhotplug.c | 26 +++++++++++++++++++++++++-
>> drivers/base/memory.c | 38 ++++++++++++++++++++++++++++++++++++++
>> include/linux/memory.h | 5 +++++
>> include/linux/memory_hotplug.h | 1 +
>> mm/memory_hotplug.c | 8 ++++++++
>> 5 files changed, 77 insertions(+), 1 deletion(-)
>>
>> Index: linux-3.5-rc4/drivers/acpi/acpi_memhotplug.c
>> ===================================================================
>> --- linux-3.5-rc4.orig/drivers/acpi/acpi_memhotplug.c 2012-07-03 14:21:49.458374960 +0900
>> +++ linux-3.5-rc4/drivers/acpi/acpi_memhotplug.c 2012-07-03 14:21:58.329264059 +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);
>> + if (result)
>> + return result;
>> +
>> + list_del(&info->list);
>> + kfree(info);
>> + }
>> +
>> kfree(mem_device);
>
> The caller does not care the return value, and after this function returns, the
> memory device will be unbound from this driver, so we should free all memory
> allocated for driver data.

We can ignore return value of remove_memory() because I think that it should
return 0. But we cannot ignore return value of offline_memory() because
kernel panic will occurs if kernel removes online memory. How do we deal with
online memory?

>>
>> return 0;
>> Index: linux-3.5-rc4/include/linux/memory_hotplug.h
>> ===================================================================
>> --- linux-3.5-rc4.orig/include/linux/memory_hotplug.h 2012-07-03 14:21:49.471374796 +0900
>> +++ linux-3.5-rc4/include/linux/memory_hotplug.h 2012-07-03 14:21:58.330264047 +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-rc4/mm/memory_hotplug.c
>> ===================================================================
>> --- linux-3.5-rc4.orig/mm/memory_hotplug.c 2012-07-03 14:21:49.466374860 +0900
>> +++ linux-3.5-rc4/mm/memory_hotplug.c 2012-07-03 14:21:58.332264022 +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-rc4/drivers/base/memory.c
>> ===================================================================
>> --- linux-3.5-rc4.orig/drivers/base/memory.c 2012-07-03 14:21:49.459374948 +0900
>> +++ linux-3.5-rc4/drivers/base/memory.c 2012-07-03 14:21:58.335263984 +0900
>> @@ -70,6 +70,44 @@ 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);
>
> The second parameter should be NULL. Otherwise, the mem->dev.kobj will
> be put twice:
> 1. we put it when mem->state is MEM_OFFLINE
> 2. we put it in find_memory_block_hinted().

Ah, O.K.
How about it?

+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);

Thanks,
Yasuaki Ishimatsu

>
> Thanks
> Wen Congyang
>
>> + if (!mem)
>> + continue;
>> + if (mem->state == MEM_OFFLINE) {
>> + kobject_put(&mem->dev.kobj);
>> + continue;
>> + }
>> +
>> + kobject_put(&mem->dev.kobj);
>> + return false;
>> + }
>> +
>> + return true;
>> +}
>> +EXPORT_SYMBOL(is_memblk_offline);
>> +
>> /*
>> * register_memory - Setup a sysfs device for a memory block
>> */
>> Index: linux-3.5-rc4/include/linux/memory.h
>> ===================================================================
>> --- linux-3.5-rc4.orig/include/linux/memory.h 2012-07-03 14:21:45.998418215 +0900
>> +++ linux-3.5-rc4/include/linux/memory.h 2012-07-03 14:21:58.340263922 +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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>