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Date: Thu, 28 Jun 2012 14:32:45 +0800
From: Wen Congyang <wency@...fujitsu.com>
To: Yasuaki Ishimatsu <isimatu.yasuaki@...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
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.
> + 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
Wen Congyang
> +
> + return 0;
> +}
> +
> /*
> * Sysfs functions -------------------------------------------------------------
> */
>
> --
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