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

From: Yasuaki Ishimatsu <[email-masked]>
Date: Fri, 6 Jul 2012 17:27:40 +0900

Hi Wen,

2012/07/04 19:01, Wen Congyang wrote:
> 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 <[email-masked]>
>>>>>> CC: Jiang Liu <[email-masked]>
>>>>>> CC: Len Brown <[email-masked]>
>>>>>> CC: Benjamin Herrenschmidt <[email-masked]>
>>>>>> CC: Paul Mackerras <[email-masked]>
>>>>>> CC: Christoph Lameter <[email-masked]>
>>>>>> Cc: Minchan Kim <[email-masked]>
>>>>>> CC: Andrew Morton <[email-masked]>
>>>>>> CC: KOSAKI Motohiro <[email-masked]>
>>>>>> Signed-off-by: Yasuaki Ishimatsu <[email-masked]>
>>>>>>
>>>>>> ---
>>>>>>     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).

How did you check it? Could you send your debug patch?

Thanks,
Yasuaki Ishimatsu

> 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 -------------------------------------------------------------
>>>>>>      */
>>>>>>
>>>>>> --
>>>>>> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
>>>>>> the body of a message to [email-masked]
>>>>>> More majordomo info at  http://vger.kernel.org/majordomo-info.html
>>>>>> Please read the FAQ at  http://www.tux.org/lkml/
>>>>>>
>>>>>
>>>>> --
>>>>> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
>>>>> the body of a message to [email-masked]
>>>>> More majordomo info at  http://vger.kernel.org/majordomo-info.html
>>>>> Please read the FAQ at  http://www.tux.org/lkml/
>>>>>
>>>>
>>>>
>>>>
>>>>
>>>
>>> --
>>> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
>>> the body of a message to [email-masked]
>>> More majordomo info at  http://vger.kernel.org/majordomo-info.html
>>> Please read the FAQ at  http://www.tux.org/lkml/
>>>
>>
>>
>>
>>
> 
> --
> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
> the body of a message to [email-masked]
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
> Please read the FAQ at  http://www.tux.org/lkml/
>