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Message-ID: <4FEC10CB.3060403@jp.fujitsu.com>
Date: Thu, 28 Jun 2012 17:07:39 +0900
From: Yasuaki Ishimatsu <isimatu.yasuaki@...fujitsu.com>
To: Wen Congyang <wency@...fujitsu.com>
CC: <linux-mm@...ck.org>, <linux-kernel@...r.kernel.org>,
<linuxppc-dev@...ts.ozlabs.org>, <linux-acpi@...r.kernel.org>,
<len.brown@...el.com>, <benh@...nel.crashing.org>,
<paulus@...ba.org>, <cl@...ux.com>, <minchan.kim@...il.com>,
<akpm@...ux-foundation.org>, <kosaki.motohiro@...fujitsu.com>
Subject: Re: [RFC PATCH 4/12] memory-hotplug : remove /sys/firmware/memmap/X
sysfs
Hi Wen,
2012/06/28 15:32, Wen Congyang wrote:
> At 06/27/2012 01:47 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: Len Brown <len.brown@...el.com>
>> CC: Benjamin Herrenschmidt <benh@...nel.crashing.org>
>> CC: Paul Mackerras <paulus@...ba.org>
>> CC: Christoph Lameter <cl@...ux.com>
>> Cc: Minchan Kim <minchan.kim@...il.com>
>> CC: Andrew Morton <akpm@...ux-foundation.org>
>> CC: KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
>> CC: Wen Congyang <wency@...fujitsu.com>
>> Signed-off-by: Yasuaki Ishimatsu <isimatu.yasuaki@...fujitsu.com>
>>
>> ---
>> drivers/firmware/memmap.c | 71 +++++++++++++++++++++++++++++++++++++++++++
>> include/linux/firmware-map.h | 6 +++
>> mm/memory_hotplug.c | 6 +++
>> 3 files changed, 82 insertions(+), 1 deletion(-)
>>
>> Index: linux-3.5-rc4/mm/memory_hotplug.c
>> ===================================================================
>> --- linux-3.5-rc4.orig/mm/memory_hotplug.c 2012-06-26 13:37:30.546288901 +0900
>> +++ linux-3.5-rc4/mm/memory_hotplug.c 2012-06-26 13:44:37.069955820 +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, "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 2012-06-25 04:53:04.000000000 +0900
>> +++ linux-3.5-rc4/include/linux/firmware-map.h 2012-06-26 13:44:37.070955807 +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 2012-06-25 04:53:04.000000000 +0900
>> +++ linux-3.5-rc4/drivers/firmware/memmap.c 2012-06-26 13:47:17.606948898 +0900
>> @@ -123,6 +123,16 @@ 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 +154,31 @@ 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_del(&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 +231,42 @@ int __init firmware_map_add_early(u64 st
>> return firmware_map_add_entry(start, end, type, entry);
>> }
>>
>> +void release_firmware_map_entry(struct firmware_map_entry *entry)
>> +{
>> + /*
>> + * FIXME : There is no idea.
>> + * How to free the entry which allocated bootmem?
>> + */
>> +}
>> +
>> +/**
>> + * 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);
>
> Hmm, we cannot find the entry easily, because the end can be:
> 1. start + size
> 2. start + size - 1
>
> So, We should fix this bug first.
This is not a bug.
start and size arguments of firmware_map_remove() include
acpi_memory_info->{start_addr, length}. And when creating a firmware_map_entry,
the entry is created by acpi_memory_info->{start_addr, length}. So I don't
think that we need care your comment.
>
>> + if (!entry)
>> + return -EINVAL;
>> +
>> + /* remove the memmap entry */
>> + remove_sysfs_fw_map_entry(entry);
>> +
>> + firmware_map_remove_entry(entry);
>> +
>> + release_firmware_map_entry(entry);
>
> I guess you want to free the memory in the above function. But I think it is
> not a good idea to free it here. We should free it when the entry->kobj's kref
> is decreased to 0.
Thanks.
I'll update your comment at next version.
Thanks,
Yasuaki Ishimatsu
>
> Thanks
> Wen Congyang
>
>> +
>> + return 0;
>> +}
>> +
>> /*
>> * Sysfs functions -------------------------------------------------------------
>> */
>>
>> --
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