Re: [RFC PATCH v4 4/13] memory-hotplug : remove /sys/firmware/memmap/X sysfs

[Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com>]

Hi Wen,

2012/07/18 19:33, Wen Congyang wrote:
> At 07/18/2012 06:09 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>
>> CC: Wen Congyang <wency@cn.fujitsu.com>
>> Signed-off-by: Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com>
>>
>> ---
>>   drivers/firmware/memmap.c    |   78 ++++++++++++++++++++++++++++++++++++++++++-
>>   include/linux/firmware-map.h |    6 +++
>>   mm/memory_hotplug.c          |    9 +++-
>>   3 files changed, 90 insertions(+), 3 deletions(-)
>>
>> Index: linux-3.5-rc6/mm/memory_hotplug.c
>> ===================================================================
>> --- linux-3.5-rc6.orig/mm/memory_hotplug.c	2012-07-18 17:20:05.670024283 +0900
>> +++ linux-3.5-rc6/mm/memory_hotplug.c	2012-07-18 17:51:03.933189930 +0900
>> @@ -1012,9 +1012,9 @@ int offline_memory(u64 start, u64 size)
>>   	return offline_pages(start_pfn, end_pfn, 120 * HZ);
>>   }
>>   
>> -int remove_memory(int nid, u64 start, u64 size)
>> +int __ref remove_memory(int nid, u64 start, u64 size)
>>   {
>> -	int ret = -EBUSY;
>> +	int ret = 0;
>>   	lock_memory_hotplug();
>>   	/*
>>   	 * The memory might become online by other task, even if you offine it.
>> @@ -1025,8 +1025,13 @@ int remove_memory(int nid, u64 start, u6
>>   			"because the memmory range is online\n",
>>   			start, start + size);
>>   		ret = -EAGAIN;
>> +		goto out;
>>   	}
>>   
>> +	/* remove memmap entry */
>> +	firmware_map_remove(start, start + size, "System RAM");
>> +
>> +out:
>>   	unlock_memory_hotplug();
>>   	return ret;
>>   
>> Index: linux-3.5-rc6/include/linux/firmware-map.h
>> ===================================================================
>> --- linux-3.5-rc6.orig/include/linux/firmware-map.h	2012-07-18 17:19:37.007382563 +0900
>> +++ linux-3.5-rc6/include/linux/firmware-map.h	2012-07-18 17:42:20.804730245 +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-rc6/drivers/firmware/memmap.c
>> ===================================================================
>> --- linux-3.5-rc6.orig/drivers/firmware/memmap.c	2012-07-18 17:19:43.618300182 +0900
>> +++ linux-3.5-rc6/drivers/firmware/memmap.c	2012-07-18 17:42:20.846729721 +0900
>> @@ -21,6 +21,7 @@
>>   #include <linux/types.h>
>>   #include <linux/bootmem.h>
>>   #include <linux/slab.h>
>> +#include <linux/mm.h>
>>   
>>   /*
>>    * Data types ------------------------------------------------------------------
>> @@ -79,7 +80,22 @@ static const struct sysfs_ops memmap_att
>>   	.show = memmap_attr_show,
>>   };
>>   
>> +#define to_memmap_entry(obj) container_of(obj, struct firmware_map_entry, kobj)
>> +
>> +static void release_firmware_map_entry(struct kobject *kobj)
>> +{
>> +	struct firmware_map_entry *entry = to_memmap_entry(kobj);
>> +	struct page *page;
>> +
>> +	page = virt_to_page(entry);
>> +	if (PageSlab(page) || PageCompound(page))
>> +		kfree(entry);
> 
> IIRC, this function's implementation is changed. Why do you do it?
> If PageCompound(page), should we check page->first_page's flags?

I forgot to write the change to change log. Jiang and Christoph discussed
how to find the slab page:

- https://lkml.org/lkml/2012/7/6/333

Then, Christoph proposed this method.  So I changed it.

Thanks,
Yasuaki Ishimatsu

> 
> Thanks
> Wen Congyang
> 
>> +
>> +	/* There is no way to free memory allocated from bootmem*/
>> +}
>> +
>>   static struct kobj_type memmap_ktype = {
>> +	.release	= release_firmware_map_entry,
>>   	.sysfs_ops	= &memmap_attr_ops,
>>   	.default_attrs	= def_attrs,
>>   };
>> @@ -123,6 +139,16 @@ 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 +170,31 @@ 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 +247,32 @@ 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.
>> + * @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 - 1, type);
>> +	if (!entry)
>> +		return -EINVAL;
>> +
>> +	firmware_map_remove_entry(entry);
>> +
>> +	/* remove the memmap entry */
>> +	remove_sysfs_fw_map_entry(entry);
>> +
>> +	return 0;
>> +}
>> +
>>   /*
>>    * Sysfs functions -------------------------------------------------------------
>>    */
>> @@ -218,7 +295,6 @@ static ssize_t type_show(struct firmware
>>   }
>>   
>>   #define to_memmap_attr(_attr) container_of(_attr, struct memmap_attribute, attr)
>> -#define to_memmap_entry(obj) container_of(obj, struct firmware_map_entry, kobj)
>>   
>>   static ssize_t memmap_attr_show(struct kobject *kobj,
>>   				struct attribute *attr, char *buf)
>>
>> --
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> 



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