Re: 2.6.17-rc5-mm3-lockdep - locking error in quotaon

[Jan Kara <jack@suse.cz>]

> On Mon, 2006-06-05 at 13:00 -0400, Valdis.Kletnieks@vt.edu wrote:
> > Using the -lockdep patch that Ingo had a few days ago, plus Stefan Richter's
> > two patches for ieee1394 (which fixed the *first* locking issue I hit)....
> 
> > [  219.535000] quotaon/1374 is trying to release lock (&inode->i_mutex) at:
> > [  219.535000]  [<c0382ba2>] mutex_unlock+0xd/0xf
> > [  219.535000] but the next lock to release is:
> > [  219.535000]  (&s->s_dquot.dqonoff_mutex){--..}, at: [<c0382a09>] mutex_lock+0xd/0xf
> 
> 
> ok the quota code is playing fun games with unlock order..
> 
> 
> 
> The quota code nests 3 mutexes but releases them in a totally different
> order; mark this as such in the code.
  Yes, it does. It was hard enough to get it to *lock* everything in
the right order and thus avoid all those nasty lock inversion problems so
unlocking is sometimes a bit arbitrary :)..

> Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
  Signed-off-by: Jan Kara <jack@suse.cz>
 
> ---
>  fs/dquot.c |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> Index: linux-2.6.17-rc5-mm3/fs/dquot.c
> ===================================================================
> --- linux-2.6.17-rc5-mm3.orig/fs/dquot.c
> +++ linux-2.6.17-rc5-mm3/fs/dquot.c
> @@ -1475,7 +1475,7 @@ static int vfs_quota_on_inode(struct ino
>  		goto out_file_init;
>  	}
>  	mutex_unlock(&dqopt->dqio_mutex);
> -	mutex_unlock(&inode->i_mutex);
> +	mutex_unlock_non_nested(&inode->i_mutex);
>  	set_enable_flags(dqopt, type);
>  
>  	add_dquot_ref(sb, type);
> 
-- 
Jan Kara <jack@suse.cz>
SuSE CR Labs
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