Re: [RFC PATCH v2 4/13] memory-hotplug : remove /sys/firmware/memmap/X sysfs

Wen Congyang
2012-07-04T09:57:24Z

At 07/04/2012 01:52 PM, Yasuaki Ishimatsu Wrote:
> Hi Wen,
>
> 2012/07/04 14:08, Wen Congyang wrote:
>> At 07/04/2012 12:45 PM, Yasuaki Ishimatsu Wrote:
>>> Hi Wen,
>>>
>>> 2012/07/03 15:35, Wen Congyang wrote:
>>>> At 07/03/2012 01:56 PM, Yasuaki Ishimatsu Wrote:
>>>>> When (hot)adding memory into system, /sys/firmware/memmap/X/{end, start, type}
>>>>> sysfs files are created. But there is no code to remove these files. The patch
>>>>> implements the function to remove them.
>>>>>
>>>>> Note : The code does not free firmware_map_entry since there is no way to free
>>>>> memory which is allocated by bootmem.
>>>>>
>>>>> 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/firmware/memmap.c | 70 +++++++++++++++++++++++++++++++++++++++++++
>>>>> include/linux/firmware-map.h | 6 +++
>>>>> mm/memory_hotplug.c | 6 +++
>>>>> 3 files changed, 81 insertions(+), 1 deletion(-)
>>>>>
>>>>> Index: linux-3.5-rc4/mm/memory_hotplug.c
>>>>> ===================================================================
>>>>> --- linux-3.5-rc4.orig/mm/memory_hotplug.c 2012-07-03 14:22:00.190240794 +0900
>>>>> +++ linux-3.5-rc4/mm/memory_hotplug.c 2012-07-03 14:22:03.549198802 +0900
>>>>> @@ -661,7 +661,11 @@ EXPORT_SYMBOL_GPL(add_memory);
>>>>>
>>>>> int remove_memory(int nid, u64 start, u64 size)
>>>>> {
>>>>> - return -EBUSY;
>>>>> + lock_memory_hotplug();
>>>>> + /* remove memmap entry */
>>>>> + firmware_map_remove(start, start + size - 1, "System RAM");
>>>>> + unlock_memory_hotplug();
>>>>> + return 0;
>>>>>
>>>>> }
>>>>> EXPORT_SYMBOL_GPL(remove_memory);
>>>>> Index: linux-3.5-rc4/include/linux/firmware-map.h
>>>>> ===================================================================
>>>>> --- linux-3.5-rc4.orig/include/linux/firmware-map.h 2012-07-03 14:21:45.766421116 +0900
>>>>> +++ linux-3.5-rc4/include/linux/firmware-map.h 2012-07-03 14:22:03.550198789 +0900
>>>>> @@ -25,6 +25,7 @@
>>>>>
>>>>> int firmware_map_add_early(u64 start, u64 end, const char *type);
>>>>> int firmware_map_add_hotplug(u64 start, u64 end, const char *type);
>>>>> +int firmware_map_remove(u64 start, u64 end, const char *type);
>>>>>
>>>>> #else /* CONFIG_FIRMWARE_MEMMAP */
>>>>>
>>>>> @@ -38,6 +39,11 @@ static inline int firmware_map_add_hotpl
>>>>> return 0;
>>>>> }
>>>>>
>>>>> +static inline int firmware_map_remove(u64 start, u64 end, const char *type)
>>>>> +{
>>>>> + return 0;
>>>>> +}
>>>>> +
>>>>> #endif /* CONFIG_FIRMWARE_MEMMAP */
>>>>>
>>>>> #endif /* _LINUX_FIRMWARE_MAP_H */
>>>>> Index: linux-3.5-rc4/drivers/firmware/memmap.c
>>>>> ===================================================================
>>>>> --- linux-3.5-rc4.orig/drivers/firmware/memmap.c 2012-07-03 14:21:45.761421180 +0900
>>>>> +++ linux-3.5-rc4/drivers/firmware/memmap.c 2012-07-03 14:22:03.569198549 +0900
>>>>> @@ -79,7 +79,16 @@ static const struct sysfs_ops memmap_att
>>>>> .show = memmap_attr_show,
>>>>> };
>>>>>
>>>>> +static void release_firmware_map_entry(struct kobject *kobj)
>>>>> +{
>>>>> + /*
>>>>> + * FIXME : There is no idea.
>>>>> + * How to free the entry which allocated bootmem?
>>>>> + */
>>>>
>>>> I find a function free_bootmem(), but I am not sure whether it can work here.
>>>
>>> It cannot work here.
>>>
>>>> Another problem: how to check whether the entry uses bootmem?
>>>
>>> When firmware_map_entry is allocated by kzalloc(), the page has PG_slab.
>>
>> This is not true. In my test, I find the page does not have PG_slab sometimes.
>
> I think that it depends on the allocated size. firmware_map_entry size is
> smaller than PAGE_SIZE. So the page has PG_Slab.

In my test, I add printk in the function firmware_map_add_hotplug() to display
page's flags. And sometimes the page is not allocated by slab(I use PageSlab()
to verify it).

Thanks
Wen Congyang

>
> Thanks,
> Yasuaki Ishimatsu
>
>>
>> Thanks
>> Wen Congyang.
>>
>>> So we can check whether the entry was allocated by bootmem or not.
>>> If the eantry was allocated by kzalloc(), we can free the entry by kfree().
>>> But if the entry was allocated by bootmem, we have no way to free the entry.
>>>
>>> Thanks,
>>> Yasuaki Ishimatsu
>>>
>>>>
>>>> Thanks
>>>> Wen Congyang
>>>>
>>>>> +}
>>>>> +
>>>>> static struct kobj_type memmap_ktype = {
>>>>> + .release = release_firmware_map_entry,
>>>>> .sysfs_ops = &memmap_attr_ops,
>>>>> .default_attrs = def_attrs,
>>>>> };
>>>>> @@ -123,6 +132,16 @@ static int firmware_map_add_entry(u64 st
>>>>> return 0;
>>>>> }
>>>>>
>>>>> +/**
>>>>> + * firmware_map_remove_entry() - Does the real work to remove a firmware
>>>>> + * memmap entry.
>>>>> + * @entry: removed entry.
>>>>> + **/
>>>>> +static inline void firmware_map_remove_entry(struct firmware_map_entry *entry)
>>>>> +{
>>>>> + list_del(&entry->list);
>>>>> +}
>>>>> +
>>>>> /*
>>>>> * Add memmap entry on sysfs
>>>>> */
>>>>> @@ -144,6 +163,31 @@ static int add_sysfs_fw_map_entry(struct
>>>>> return 0;
>>>>> }
>>>>>
>>>>> +/*
>>>>> + * Remove memmap entry on sysfs
>>>>> + */
>>>>> +static inline void remove_sysfs_fw_map_entry(struct firmware_map_entry *entry)
>>>>> +{
>>>>> + kobject_put(&entry->kobj);
>>>>> +}
>>>>> +
>>>>> +/*
>>>>> + * Search memmap entry
>>>>> + */
>>>>> +
>>>>> +struct firmware_map_entry * __meminit
>>>>> +find_firmware_map_entry(u64 start, u64 end, const char *type)
>>>>> +{
>>>>> + struct firmware_map_entry *entry;
>>>>> +
>>>>> + list_for_each_entry(entry, &map_entries, list)
>>>>> + if ((entry->start == start) && (entry->end == end) &&
>>>>> + (!strcmp(entry->type, type)))
>>>>> + return entry;
>>>>> +
>>>>> + return NULL;
>>>>> +}
>>>>> +
>>>>> /**
>>>>> * firmware_map_add_hotplug() - Adds a firmware mapping entry when we do
>>>>> * memory hotplug.
>>>>> @@ -196,6 +240,32 @@ int __init firmware_map_add_early(u64 st
>>>>> return firmware_map_add_entry(start, end, type, entry);
>>>>> }
>>>>>
>>>>> +/**
>>>>> + * firmware_map_remove() - remove a firmware mapping entry
>>>>> + * @start: Start of the memory range.
>>>>> + * @end: End of the memory range (inclusive).
>>>>> + * @type: Type of the memory range.
>>>>> + *
>>>>> + * removes a firmware mapping entry.
>>>>> + *
>>>>> + * Returns 0 on success, or -EINVAL if no entry.
>>>>> + **/
>>>>> +int __meminit firmware_map_remove(u64 start, u64 end, const char *type)
>>>>> +{
>>>>> + struct firmware_map_entry *entry;
>>>>> +
>>>>> + entry = find_firmware_map_entry(start, end, type);
>>>>> + if (!entry)
>>>>> + return -EINVAL;
>>>>> +
>>>>> + /* remove the memmap entry */
>>>>> + remove_sysfs_fw_map_entry(entry);
>>>>> +
>>>>> + firmware_map_remove_entry(entry);
>>>>> +
>>>>> + return 0;
>>>>> +}
>>>>> +
>>>>> /*
>>>>> * Sysfs functions -------------------------------------------------------------
>>>>> */
>>>>>
>>>>> --
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