From: Eric Sandeen Subject: Re: [PATCH] fix bogus BUG_ONs in in mballoc code Date: Thu, 12 Mar 2009 21:08:02 -0500 Message-ID: <49B9C002.9090008@redhat.com> References: <49B93E44.8070109@ph.tum.de> <49B958A1.6060805@redhat.com> <20090313010940.GO17104@mit.edu> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: Thiemo Nagel , Ext4 Developers List To: Theodore Tso Return-path: Received: from mx2.redhat.com ([66.187.237.31]:39582 "EHLO mx2.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754271AbZCMCIJ (ORCPT ); Thu, 12 Mar 2009 22:08:09 -0400 In-Reply-To: <20090313010940.GO17104@mit.edu> Sender: linux-ext4-owner@vger.kernel.org List-ID: Theodore Tso wrote: > On Thu, Mar 12, 2009 at 01:46:57PM -0500, Eric Sandeen wrote: >> Thiemo Nagel reported that: >> >> # dd if=/dev/zero of=image.ext4 bs=1M count=2 >> # mkfs.ext4 -v -F -b 1024 -m 0 -g 512 -G 4 -I 128 -N 1 \ >> -O large_file,dir_index,flex_bg,extent,sparse_super image.ext4 >> # mount -o loop image.ext4 mnt/ >> # dd if=/dev/zero of=mnt/file >> >> oopsed, with a BUG_ON in ext4_mb_normalize_request because >> size == EXT4_BLOCKS_PER_GROUP >> >> It appears to me (esp. after talking to Andreas) that the BUG_ON >> is bogus; a request of exactly EXT4_BLOCKS_PER_GROUP should >> be allowed, though larger sizes do indicate a problem. >> >> Fix that an another (apparently rare) codepath with a similar check. > > Hmm.... is this at all likely to happen with a standard ext4 > filesystem parameters? Or was this triggered because of the > artifially set -g 512 parameter? The question is whether we should > try pushing this to Linus at this point, or let this wait until the > merge window opens. > > Opinions? > > = Ted > < I wondered the same thing, and will admit to probably not digging deep enough on this one. I think the fix is ok as is but you are asking the right questions. Maybe a clusterfs mballoc expert can chime in and save us some time? :) -=Eric