From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755032Ab0EJChb (ORCPT ); Sun, 9 May 2010 22:37:31 -0400 Received: from mail.redflag-linux.com ([219.237.229.196]:49592 "EHLO mail.redflag-linux.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754992Ab0EJCh3 (ORCPT ); Sun, 9 May 2010 22:37:29 -0400 Message-ID: <4BE77149.8050307@redflag-linux.com> Date: Mon, 10 May 2010 10:36:57 +0800 From: =?UTF-8?B?Iua9mOWNq+W5syhQZXRlciBQYW4pIg==?= User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.9.1.7) Gecko/20100324 RedFlag/3.0.1-1rf2.dt8 Thunderbird/3.0.1 MIME-Version: 1.0 To: Jan Kara 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 References: <4BE2C5D5.2050207@redflag-linux.com> <20100507162348.GD3265@atrey.karlin.mff.cuni.cz> In-Reply-To: <20100507162348.GD3265@atrey.karlin.mff.cuni.cz> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 05/08/2010 12:23 AM, Jan Kara wrote: >> 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 You got the point! Many thanks. Regards -- Peter Pan Red Flag Software Co.,Ltd