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

Wen Congyang
2012-07-06T09:18:41Z

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 <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).
>
> 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 <wency@cn.fujitsu.com>
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 -------------------------------------------------------------
>>>>>>> */
>>>>>>>
>>>>>>> --
>>>>>>> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
>>>>>>> the body of a message to majordomo@vger.kernel.org
>>>>>>> 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 majordomo@vger.kernel.org
>>>>>> 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 majordomo@vger.kernel.org
>>>> 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 majordomo@vger.kernel.org
>> More majordomo info at http://vger.kernel.org/majordomo-info.html
>> Please read the FAQ at http://www.tux.org/lkml/
>>
>
>
>
>