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

From: Wen Congyang <[email-masked]>
Date: Fri, 06 Jul 2012 17:20:25 +0800

At 07/06/2012 04:27 PM, Yasuaki Ishimatsu Wrote:
> 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?

When the memory is not allocated from slab, the flags is 0x10000000008000.

>>From 8dd51368d6c03edf7edc89cab17441e3741c39c7 Mon Sep 17 00:00:00 2001
From: Wen Congyang <[email-masked]>
Date: Wed, 4 Jul 2012 16:05:26 +0800
Subject: [PATCH] debug

---
 drivers/firmware/memmap.c |    7 +++++++
 1 files changed, 7 insertions(+), 0 deletions(-)

diff --git a/drivers/firmware/memmap.c b/drivers/firmware/memmap.c
index adc0710..993ba3f 100644
--- a/drivers/firmware/memmap.c
+++ b/drivers/firmware/memmap.c
@@ -21,6 +21,7 @@
 #include <linux/types.h>
 #include <linux/bootmem.h>
 #include <linux/slab.h>
+#include <linux/mm.h>
 
 /*
  * Data types ------------------------------------------------------------------
@@ -160,11 +161,17 @@ static int add_sysfs_fw_map_entry(struct firmware_map_entry *entry)
 int __meminit firmware_map_add_hotplug(u64 start, u64 end, const char *type)
 {
 	struct firmware_map_entry *entry;
+	struct page *entry_page;
 
 	entry = kzalloc(sizeof(struct firmware_map_entry), GFP_ATOMIC);
 	if (!entry)
 		return -ENOMEM;
 
+	entry_page = virt_to_page(entry);
+	printk(KERN_WARNING "flags: %lx\n", entry_page->flags);
+	if (PageSlab(entry_page)) {
+		printk(KERN_WARNING "page is allocated from slab\n");
+	}
 	firmware_map_add_entry(start, end, type, entry);
 	/* create the memmap entry */
 	add_sysfs_fw_map_entry(entry);
-- 
1.7.1

Thanks
Wen Congyang

> 
> 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 -------------------------------------------------------------
>>>>>>>      */
>>>>>>>
>>>>>>> --
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> 
> 
> 
>