linux-kernel - Re: network regression: cannot rename netdev twice

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Message-ID: <m18vko6jmv.fsf@fess.ebiederm.org>
Date:	Tue, 31 Jan 2012 06:18:00 -0800
From:	ebiederm@...ssion.com (Eric W. Biederman)
To:	Kay Sievers <kay.sievers@...y.org>
Cc:	Jiri Slaby <jslaby@...e.cz>, Greg KH <greg@...ah.com>,
	LKML <linux-kernel@...r.kernel.org>,
	ML netdev <netdev@...r.kernel.org>
Subject: Re: network regression: cannot rename netdev twice

Kay Sievers <kay.sievers@...y.org> writes:

> On Tue, Jan 31, 2012 at 12:17, Jiri Slaby <jslaby@...e.cz> wrote:
>> On 01/31/2012 12:13 PM, Kay Sievers wrote:
>
>>> This is a command sequence you type manually?
>>
>> Yea, and it is working with 3.3.0-rc1-next-20120124_64+. Not with
>> 3.3.0-rc1-next-20120131_64+.
>>
>>> You are sure that userspace is not working in the background,
>>> triggered by uevents, and comes into your way here?
>>
>> Note that krtek exists after the first command. But cannot be renamed
>> further.
>
> Yeah, I can confirm the problem here. I works fine with earlier
> kernels and fails with the latest -next:
>
> # uname -r
> 3.3.0-rc1-next-20120131+
> # modprobe dummy
> # ip link set dummy0 name foo0
> # ip link set foo0 name bar0
> RTNETLINK answers: No such file or directory

There is something weird going on when sysfs directories and symlinks
are renamed.  My guess is that I fat fingered something with one of my
last sysfs patches.  I will look more deeply once I have slept some
more.

The second network device renames fails because the first rename did not
work properly.  ls -l /sys/class/net/ /sys/virtual/net/ will let you see
what I mean.

Eric
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