linux-kernel - Re: [PATCH 03/20] sysfs: Remove now unnecessary error reporting suppression.

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Date:	Wed, 20 May 2009 23:12:59 -0700
From:	ebiederm@...ssion.com (Eric W. Biederman)
To:	Tejun Heo <tj@...nel.org>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Greg Kroah-Hartman <gregkh@...e.de>,
	linux-kernel@...r.kernel.org,
	Cornelia Huck <cornelia.huck@...ibm.com>,
	linux-fsdevel@...r.kernel.org,
	"Eric W. Biederman" <ebiederm@...stanetworks.com>
Subject: Re: [PATCH 03/20] sysfs: Remove now unnecessary error reporting suppression.

Tejun Heo <tj@...nel.org> writes:

> Eric W. Biederman wrote:
>> From: Eric W. Biederman <ebiederm@...ssion.com>
>> 
>> Now that we use sysfs_rename_link in the places we previously
>> used sysfs_create_link_nowarn we can remove sysfs_create_link_nowarn
>> and all it's supporting infrastructure.
>
> I'm not entirely sure why implementing a rename helper means that we
> don't need nowarn version anymore.  Nothing really changed or is it
> that the nowarn version wasn't too necessary anyway?

nowarn was used exclusively in the hand coded version of rename.  By
switching the order I was able perform the operations such that even
if the operation is ultimately a noop and are attempt to recreate the
same link we won't have problems.

The two callers of device_rename are required (and do) perform locking
to ensure the rename operation is safe.  So the exact implementation
in the sysfs does not matter.  Although making it atomic would be
ideal.

The nowarn helpers existed because the order was backwards in
device rename and when a noop rename happened sysfs would mistakenly
think there was a problem and complain.  I think the upper
layers suppress that case now for a while at least it lead to
a lot of spurious warnings.

Eric
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