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

Yasuaki Ishimatsu
2012-07-04T05:53:01Z

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.

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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>>>
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>>
>>
>>
>>
>
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