netdev - Re: 2.6.24-rc3: find complains about /proc/net

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Date:	Tue, 20 Nov 2007 18:19:12 -0700
From:	ebiederm@...ssion.com (Eric W. Biederman)
To:	Pavel Emelyanov <xemul@...nvz.org>
Cc:	"Rafael J. Wysocki" <rjw@...k.pl>, Pavel Machek <pavel@....cz>,
	kernel list <linux-kernel@...r.kernel.org>,
	netdev <netdev@...r.kernel.org>
Subject: Re: 2.6.24-rc3: find complains about /proc/net

Pavel Emelyanov <xemul@...nvz.org> writes:

> Rafael J. Wysocki wrote:
>> On Monday, 19 of November 2007, Pavel Machek wrote:
>>> Hi!
>>>
>>> I think that this worked before:
>>>
>>> root@amd:/proc# find . -name "timer_info"
>>> find: WARNING: Hard link count is wrong for ./net: this may be a bug
>>> in your filesystem driver.  Automatically turning on find's -noleaf
>>> option.  Earlier results may have failed to include directories that
>>> should have been searched.
>>> root@amd:/proc#
>> 
>> I'm seeing that too.
>
> I have a better things with 2.6.24-rc3 ;)
>
> # cd /proc/net
> # ls ..
> ls: reading directory ..: Not a directory
>
> and this
>
> # cd /proc
> # find
> ...
> ./net
> find: . changed during execution of find
> # find net
> find: net changed during execution of find
> # find net/
> <this works ok however>
>
> Moreover. Program that opens /proc/net and dumps the /proc/self/fd
> files produces the following:
>
> # cd /
> # a.out /proc/net
> ...
> lr-x------  1 root root 64 Nov 20 18:02 3 -> /proc/net/net (deleted)
> ...
> # cd /proc/net
> # a.out .
> ...
> lr-x------  1 root root 64 Nov 20 18:03 3 -> /proc/net/net (deleted)
> ...
> # a.out ..
> ...
> lr-x------  1 root root 64 Nov 20 18:03 3 -> /proc/net
> ...
>
> This all is somehow related to the shadow proc files.
> E.g. the first problem (with -ENOTDIR) is due to the shadow /proc/net
> dentry doesn't implement the .readdir method:
>
> static const struct file_operations proc_net_dir_operations = {
>         .read                   = generic_read_dir,
> };
>
> And I haven't managed to find out why the rest problems
> occur...
>
> Eric, do you have fixes for it?

Duh.  There is one other possible solution I forgot to mention and
at least as a first pass it should be relatively simple.  Have the
mount of proc capture the network namespace.  I'm not certain
if it is what we want long term but it should be simple and relatively
easy to implement.

I don't like capturing the network namespace when we mount proc but
it is easier then implementing /proc/self/net.  Which is the other
real alternative.

Eric
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