From mboxrd@z Thu Jan 1 00:00:00 1970 From: Bill Davidsen Subject: Re: [PATCH] ext4: fix loop in do_split() Date: Sat, 29 Nov 2008 19:36:52 -0500 Message-ID: <4931E024.2010500@tmr.com> References: <49310D34.1000205@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: tytso@mit.edu, adilger@sun.com, linux-ext4@vger.kernel.org, linux-kernel@vger.kernel.org To: roel kluin Return-path: Received: from mail.tmr.com ([64.65.253.246]:57243 "EHLO partygirl.tmr.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755590AbYK3AhW (ORCPT ); Sat, 29 Nov 2008 19:37:22 -0500 In-Reply-To: <49310D34.1000205@gmail.com> Sender: linux-ext4-owner@vger.kernel.org List-ID: roel kluin wrote: > unsigned i >= 0 is always true > > Signed-off-by: Roel Kluin > --- > diff --git a/fs/ext4/namei.c b/fs/ext4/namei.c > index 63adcb7..389cf60 100644 > --- a/fs/ext4/namei.c > +++ b/fs/ext4/namei.c > @@ -1198,7 +1198,7 @@ static struct ext4_dir_entry_2 *do_split(handle_t *handle, struct inode *dir, > /* Split the existing block in the middle, size-wise */ > size = 0; > move = 0; > - for (i = count-1; i >= 0; i--) { > + for (i = count-1; i < count; i--) { > /* is more than half of this entry in 2nd half of the block? */ > if (size + map[i].size/2 > blocksize/2) > break; > While this unsigned wrap method is technically valid, it certainly isn't obvious, and making code readable should be a goal as well as making it correct. After all, code which is hard to read is hard to understand, making it hard to maintain. I therefore suggest the simpler form: for (i = count; i--; ) { which gives the same i values inside the loop, but does assume that the reader remembers that i is unsigned, and intuitively understand wraparound while passing zero. -- Bill Davidsen "We have more to fear from the bungling of the incompetent than from the machinations of the wicked." - from Slashdot