linux-kernel - Re: [PATCH 2/4] sysfs: Only take active references on attributes.

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Message-ID: <20100215081527.GD12076@hack.private>
Date:	Mon, 15 Feb 2010 16:15:27 +0800
From:	Américo Wang <xiyou.wangcong@...il.com>
To:	Américo Wang <xiyou.wangcong@...il.com>
Cc:	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Greg Kroah-Hartman <gregkh@...e.de>,
	"Tejun Heo <tj@...nel.org> Neil Brown" <neilb@...e.de>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/4] sysfs: Only take active references on attributes.

On Mon, Feb 15, 2010 at 03:27:45PM +0800, Américo Wang wrote:
>On Thu, Feb 11, 2010 at 03:20:00PM -0800, Eric W. Biederman wrote:
>>
>>If we exclude directories and symlinks from the set of sysfs
>>dirents where we need active references we are left with
>>sysfs attributes (binary or not).
>>
>>- Tweak sysfs_deactivate to only do something on attributes
>>- Move lockdep initialization into sysfs_file_add_mode to
>>  limit it to just attributes.
>
>Why?
>
>If I read your patch correctly, s_active will be useless
>for non-attributes sysfs entries? For sysfs dir, maybe,
>since it can only be removed by sysfs_remove_dir(),
>but not sure about sysfs symlinks...
>

For sysfs dir's, opening it will not get s_active,
since it doesn't have .open member. But it does
put s_active when removing it. This seems buggy?

For symlinks, it seems sysfs totally ignores s_active,
thus is safe for this patch.

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