linux-kernel - Re: Broken link in /sys/class/net/ [was: [GIT] Networking]

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Message-ID: <4EADB864.3060702@suse.cz>
Date:	Sun, 30 Oct 2011 21:49:40 +0100
From:	Jiri Slaby <jslaby@...e.cz>
To:	"Eric W. Biederman" <ebiederm@...ssion.com>
CC:	Jiri Slaby <jirislaby@...il.com>, Greg KH <gregkh@...e.de>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	David Miller <davem@...emloft.net>,
	Mikulas Patocka <mpatocka@...hat.com>,
	akpm@...ux-foundation.org, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: Broken link in /sys/class/net/ [was: [GIT] Networking]

On 10/30/2011 05:49 AM, Eric W. Biederman wrote:
> Jiri Slaby <jslaby@...e.cz> writes:
> 
>> On 10/25/2011 03:13 PM, Greg KH wrote:
>>> On Tue, Oct 25, 2011 at 01:46:11PM +0200, Linus Torvalds wrote:
>>>> Anyway, after that rant about really bad practices, let me say that I
>>>> did fix up the conflict and I think it's right. But I won't guarantee
>>>> it, so please check the changes to fs/sysfs/dir.c.
>>>
>>> I think it looks ok, I've booted the merge result, and am typing and
>>> sending this from the new kernel, and it hasn't crashed yet :)
>>
>> Hi, maybe this was not caused by the merge, but the patch[1] causes this
>> mess in /sys/class/net/ for me:
>> l????????? ? ?    ?    ?             ? eth1
>>
>> This happens after one renames a net device -- the new name is eth1 here.
>>
>> [1] 4f72c0cab40 (sysfs: use rb-tree for name lookups)
> 
> This looks pretty fixable but today sysfs_rename does not do anything
> with the to move a renamed entry to a different position in the rbtree.
> 
> If the directory itself changes sysfs_rename should be fine, and it
> looks like a trivial patch to always apply the directory rename logic
> in sysfs_rename. 
> 
> I think all we need is something like the untested patch below to fix
> the network device rename problem.

Looks like it works. Thanks.

> diff --git a/fs/sysfs/dir.c b/fs/sysfs/dir.c
> index 48ffbdf..a294068 100644
> --- a/fs/sysfs/dir.c
> +++ b/fs/sysfs/dir.c
> @@ -865,14 +865,13 @@ int sysfs_rename(struct sysfs_dirent *sd,
>  		sd->s_name = new_name;
>  	}
>  
> -	/* Remove from old parent's list and insert into new parent's list. */
> -	if (sd->s_parent != new_parent_sd) {
> -		sysfs_unlink_sibling(sd);
> -		sysfs_get(new_parent_sd);
> -		sysfs_put(sd->s_parent);
> -		sd->s_parent = new_parent_sd;
> -		sysfs_link_sibling(sd);
> -	}
> +	/* Move to the appropriate place in the appropriate directories rbtree. */
> +	sysfs_unlink_sibling(sd);
> +	sysfs_get(new_parent_sd);
> +	sysfs_put(sd->s_parent);
> +	sd->s_parent = new_parent_sd;
> +	sysfs_link_sibling(sd);
> +
>  	sd->s_ns = new_ns;
>  
>  	error = 0;
> 


-- 
js
suse labs
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