linux-kernel - Re: [PATCH 07/11] gfs2: pass correct dentry to finish_open() in __gfs2

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Date:	Mon, 16 Sep 2013 15:34:22 +0200
From:	Miklos Szeredi <miklos@...redi.hu>
To:	Steven Whitehouse <swhiteho@...hat.com>
Cc:	viro@...IV.linux.org.uk, linux-fsdevel@...r.kernel.org,
	linux-kernel@...r.kernel.org, mszeredi@...e.cz,
	stable@...r.kernel.org
Subject: Re: [PATCH 07/11] gfs2: pass correct dentry to finish_open() in
 __gfs2_lookup()

On Mon, Sep 16, 2013 at 02:13:14PM +0100, Steven Whitehouse wrote:
> Hi,
> 
> On Mon, 2013-09-16 at 14:52 +0200, Miklos Szeredi wrote:
> > From: Miklos Szeredi <mszeredi@...e.cz>
> > 
> > AFAICS if d_splice_alias() returned non-NULL, this code would Oops
> > (finish_open expects an instantiated dentry).
> > 
> > Signed-off-by: Miklos Szeredi <mszeredi@...e.cz>
> > Cc: Steven Whitehouse <swhiteho@...hat.com>
> > Cc: stable@...r.kernel.org
> > ---
> >  fs/gfs2/inode.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/fs/gfs2/inode.c b/fs/gfs2/inode.c
> > index 6d7f976..abe7dae 100644
> > --- a/fs/gfs2/inode.c
> > +++ b/fs/gfs2/inode.c
> > @@ -774,7 +774,7 @@ static struct dentry *__gfs2_lookup(struct inode *dir, struct dentry *dentry,
> >  
> >  	d = d_splice_alias(inode, dentry);
> >  	if (file && S_ISREG(inode->i_mode))
> > -		error = finish_open(file, dentry, gfs2_open_common, opened);
> > +		error = finish_open(file, d ? d : dentry, gfs2_open_common, opened);
> >  
> >  	gfs2_glock_dq_uninit(&gh);
> >  	if (error)
> 
> Not sure I understand why this is required... when the inode is a
> regular file, d can only be an error (if the inode is an error) or it
> will be NULL.

Okay, you're right.  Still, something like the following should make this clear
and ensure things don't break in the future.

Thanks,
Miklos

---
 fs/gfs2/inode.c |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

--- a/fs/gfs2/inode.c
+++ b/fs/gfs2/inode.c
@@ -775,8 +775,10 @@ static struct dentry *__gfs2_lookup(stru
 	}
 
 	d = d_splice_alias(inode, dentry);
-	if (file && S_ISREG(inode->i_mode))
+	if (file && S_ISREG(inode->i_mode)) {
+		BUG_ON(d);
 		error = finish_open(file, dentry, gfs2_open_common, opened);
+	}
 
 	gfs2_glock_dq_uninit(&gh);
 	if (error)
--
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