linux-kernel - Re: [PATCH 1/1] Drivers: base: memory: Export symbols for onlining memory blocks

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Date:	Mon, 22 Jul 2013 14:37:16 +0200
From:	Michal Hocko <mhocko@...e.cz>
To:	"K. Y. Srinivasan" <kys@...rosoft.com>
Cc:	gregkh@...uxfoundation.org, linux-kernel@...r.kernel.org,
	devel@...uxdriverproject.org, olaf@...fle.de, apw@...onical.com,
	andi@...stfloor.org, akpm@...ux-foundation.org, linux-mm@...ck.org,
	kamezawa.hiroyuki@...il.com, hannes@...xchg.org,
	yinghan@...gle.com, jasowang@...hat.com, kay@...y.org
Subject: Re: [PATCH 1/1] Drivers: base: memory: Export symbols for onlining
 memory blocks

On Fri 19-07-13 12:23:05, K. Y. Srinivasan wrote:
> The current machinery for hot-adding memory requires having udev
> rules to bring the memory segments online. Export the necessary functionality
> to to bring the memory segment online without involving user space code. 

Why? Who is going to use it and for what purpose?
If you need to do it from the kernel cannot you use usermod helper
thread?

Besides that this is far from being complete. memory_block_change_state
seems to depend on device_hotplug_lock and find_memory_block is
currently called with mem_sysfs_mutex held. None of them is exported
AFAICS.

> Signed-off-by: K. Y. Srinivasan <kys@...rosoft.com>
> ---
>  drivers/base/memory.c  |    5 ++++-
>  include/linux/memory.h |    4 ++++
>  2 files changed, 8 insertions(+), 1 deletions(-)
> 
> diff --git a/drivers/base/memory.c b/drivers/base/memory.c
> index 2b7813e..a8204ac 100644
> --- a/drivers/base/memory.c
> +++ b/drivers/base/memory.c
> @@ -328,7 +328,7 @@ static int __memory_block_change_state_uevent(struct memory_block *mem,
>  	return ret;
>  }
>  
> -static int memory_block_change_state(struct memory_block *mem,
> +int memory_block_change_state(struct memory_block *mem,
>  		unsigned long to_state, unsigned long from_state_req,
>  		int online_type)
>  {
> @@ -341,6 +341,8 @@ static int memory_block_change_state(struct memory_block *mem,
>  
>  	return ret;
>  }
> +EXPORT_SYMBOL(memory_block_change_state);
> +
>  static ssize_t
>  store_mem_state(struct device *dev,
>  		struct device_attribute *attr, const char *buf, size_t count)
> @@ -540,6 +542,7 @@ struct memory_block *find_memory_block(struct mem_section *section)
>  {
>  	return find_memory_block_hinted(section, NULL);
>  }
> +EXPORT_SYMBOL(find_memory_block);
>  
>  static struct attribute *memory_memblk_attrs[] = {
>  	&dev_attr_phys_index.attr,
> diff --git a/include/linux/memory.h b/include/linux/memory.h
> index 85c31a8..8e3ede5 100644
> --- a/include/linux/memory.h
> +++ b/include/linux/memory.h
> @@ -115,6 +115,10 @@ extern void unregister_memory_notifier(struct notifier_block *nb);
>  extern int register_memory_isolate_notifier(struct notifier_block *nb);
>  extern void unregister_memory_isolate_notifier(struct notifier_block *nb);
>  extern int register_new_memory(int, struct mem_section *);
> +extern int memory_block_change_state(struct memory_block *mem,
> +		unsigned long to_state, unsigned long from_state_req,
> +		int online_type);
> +
>  #ifdef CONFIG_MEMORY_HOTREMOVE
>  extern int unregister_memory_section(struct mem_section *);
>  #endif
> -- 
> 1.7.4.1
> 
> --
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-- 
Michal Hocko
SUSE Labs
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