From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757013Ab0EGQXv (ORCPT ); Fri, 7 May 2010 12:23:51 -0400 Received: from ksp.mff.cuni.cz ([195.113.26.206]:48232 "EHLO atrey.karlin.mff.cuni.cz" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1756847Ab0EGQXt (ORCPT ); Fri, 7 May 2010 12:23:49 -0400 Date: Fri, 7 May 2010 18:23:48 +0200 From: Jan Kara To: =?utf-8?B?Iua9mOWNq+W5syhQZXRlciBQYW4pIg==?= Cc: tj@kernel.org, Christoph Lameter , hch@lst.de, akpm@linux-foundation.org, adilger@sun.com, linux-ext4@vger.kernel.org, linux-kernel@vger.kernel.org, kernel-janitors@vger.kernel.org Subject: Re: [PATCH] ext2/ext3:useless code for return value Message-ID: <20100507162348.GD3265@atrey.karlin.mff.cuni.cz> References: <4BE2C5D5.2050207@redflag-linux.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <4BE2C5D5.2050207@redflag-linux.com> User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > When rsv is the right hand side of goal, we should return NULL, > because now rsv's prev is NULL, or we return rsv. > > Signed-off-by: Peter Pan(潘卫平) > > --- > fs/ext2/balloc.c | 6 +----- > fs/ext3/balloc.c | 6 +----- > 2 files changed, 2 insertions(+), 10 deletions(-) > > diff --git a/fs/ext2/balloc.c b/fs/ext2/balloc.c > index 3cf038c..023990f 100644 > --- a/fs/ext2/balloc.c > +++ b/fs/ext2/balloc.c > @@ -323,11 +323,7 @@ search_reserve_window(struct rb_root *root, > ext2_fsblk_t goal) > * side of the interval containing the goal. If it's the RHS, > * we need to back up one. > */ > - if (rsv->rsv_start > goal) { > - n = rb_prev(&rsv->rsv_node); > - rsv = rb_entry(n, struct ext2_reserve_window_node, rsv_node); > - } > - return rsv; > + return (rsv->rsv_start < goal) ? rsv : NULL; Hmm, I'm not sure I understand your reasoning. Suppose we have an RB-tree with two intervals 0-10, 20-30. Interval 0-10 is in the root. Now we search for goal 15. In the root we go to right because 10<15, in the next node we go to left because 15 < 20. Then the loop terminates. Now your code would return NULL but previous code would return rb_prev of interval 20-30 which is 0-10. And that is what we want as far as I understand what we expect from the function... Honza -- Jan Kara SuSE CR Labs