From mboxrd@z Thu Jan  1 00:00:00 1970
From: Al Viro <viro@ZenIV.linux.org.uk>
Subject: Re: [PATCH 1/4] cifs: make cifs_lookup return a dentry
Date: Sat, 22 May 2010 15:46:15 +0100
Message-ID: <20100522144615.GN31073@ZenIV.linux.org.uk>
References: <1274466317-28231-1-git-send-email-jlayton@redhat.com>
 <1274466317-28231-2-git-send-email-jlayton@redhat.com>
 <20100522133051.GL31073@ZenIV.linux.org.uk>
 <20100522100836.28b95cff@tlielax.poochiereds.net>
Mime-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Cc: linux-cifs-client@lists.samba.org, linux-fsdevel@vger.kernel.org
To: Jeff Layton <jlayton@redhat.com>
Return-path: <linux-fsdevel-owner@vger.kernel.org>
Received: from zeniv.linux.org.uk ([195.92.253.2]:39294 "EHLO
	ZenIV.linux.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
	with ESMTP id S1753807Ab0EVOqR (ORCPT
	<rfc822;linux-fsdevel@vger.kernel.org>);
	Sat, 22 May 2010 10:46:17 -0400
Content-Disposition: inline
In-Reply-To: <20100522100836.28b95cff@tlielax.poochiereds.net>
Sender: linux-fsdevel-owner@vger.kernel.org
List-ID: <linux-fsdevel.vger.kernel.org>

On Sat, May 22, 2010 at 10:08:36AM -0400, Jeff Layton wrote:
> On Sat, 22 May 2010 14:30:51 +0100
> Al Viro <viro@ZenIV.linux.org.uk> wrote:
> 
> > On Fri, May 21, 2010 at 02:25:14PM -0400, Jeff Layton wrote:
> > > cifs_lookup doesn't actually return a dentry. It instantiates the one
> > > that's passed in, but callers don't have any way to know if the lookup
> > > succeeded.
> > 
> > Huh?  Of course they do - ->lookup() has every right to do just that;
> > d_add() and return NULL is perfectly legitimate.
> 
> OK, bad description on my part... Is one way of doing this preferred
> over another?

Non-NULL, non ERR_PTR() strongly implies that you have found a different
dentry and tell the caller to use it instead; returning the argument (after
having cached it and bumped its refcount) will work, but it's pretty much
a deliberate obfuscation.