linux-kernel - Re: [PATCH] proc: proc_get_inode should de

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Message-Id: <20090223152555.a499b76a.akpm@linux-foundation.org>
Date:	Mon, 23 Feb 2009 15:25:55 -0800
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Krzysztof Sachanowicz <analyzer1@...il.com>
Cc:	linux-kernel@...r.kernel.org, marcin.pilipczuk@...il.com,
	torvalds@...ux-foundation.org,
	Alexey Dobriyan <adobriyan@...il.com>
Subject: Re: [PATCH] proc: proc_get_inode should de_put when inode already
 initialized

On Mon, 23 Feb 2009 22:21:55 +0100
Krzysztof Sachanowicz <analyzer1@...il.com> wrote:

> de_get is called before every proc_get_inode, but corresponding de_put is 
> called only when dropping last reference to an inode. This might cause 
> something like
> remove_proc_entry: /proc/stats busy, count=14496
> to be printed to the syslog.
> 
> The fix is to call de_put in case of an already initialized inode in 
> proc_get_inode.
> 
> Signed-off-by: Krzysztof Sachanowicz <analyzer1@...il.com>
> Tested-by: Marcin Pilipczuk <marcin.pilipczuk@...il.com>
> ---
> --- linux-2.6.29-rc6.orig/fs/proc/inode.c	2009-02-23 20:43:32.000000000 +0100
> +++ linux-2.6.29-rc6/fs/proc/inode.c	2009-02-23 20:46:37.000000000 +0100
> @@ -485,8 +485,10 @@ struct inode *proc_get_inode(struct supe
>  			}
>  		}
>  		unlock_new_inode(inode);
> -	} else
> +	} else {
>  	       module_put(de->owner);
> +	       de_put(de);
> +	}
>  	return inode;
>  
>  out_ino:

This code area looks quite different in linux-next, although the
changes there are removing proc_dir_entry.owner altogether and aren't
obviously targetted at fixing this bug.

Also...

It's unpleasing to have the de_get() inside the caller and the de_put()
inside the callee - it is better to have them both happening at the
same level.  If it is the case that "de_get is called before every
proc_get_inode", then perhaps that operation should simply be moved
into proc_get_inode().


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