From: Justin Maggard Subject: Re: 2.6.33.1: ext4 disk free weirdness Date: Mon, 29 Mar 2010 10:43:09 -0700 Message-ID: <150c16851003291043l2fa17795o3b8339b2e04514ba@mail.gmail.com> References: <20100329045748.GR2657@zip.com.au> <4BB0BDD2.3080100@redhat.com> <20100329145311.GA4671@thunk.org> <4BB0C0D2.1080303@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: QUOTED-PRINTABLE Cc: ext4 development To: Eric Sandeen Return-path: Received: from mail-gw0-f46.google.com ([74.125.83.46]:36718 "EHLO mail-gw0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753490Ab0C2RnK convert rfc822-to-8bit (ORCPT ); Mon, 29 Mar 2010 13:43:10 -0400 Received: by gwaa18 with SMTP id a18so4173562gwa.19 for ; Mon, 29 Mar 2010 10:43:10 -0700 (PDT) In-Reply-To: <4BB0C0D2.1080303@redhat.com> Sender: linux-ext4-owner@vger.kernel.org List-ID: On Mon, Mar 29, 2010 at 8:01 AM, Eric Sandeen wrot= e: > tytso@mit.edu wrote: >> On Mon, Mar 29, 2010 at 09:48:50AM -0500, Eric Sandeen wrote: >>> CaT wrote: >>>> Using kernel 2.6.33.1. Am rsyncing from /data/mirror (a raid0 moun= t) to >>>> /dev/sda1 (a usb HD). Both filesystems formatted as ext3 but mount= ed as >>>> ext4. /mnt filesystem is only being added to and currently large f= iles >>>> (iso files 700MB-4.4GB) are being copied. When I remounted /mnt as= ext3 >>>> I could not duplicate the issue and the amount of disk used stabil= ised >>>> at 182G. The df results, whilst /mnt is mounted as ext4, are below= : >>> I would say this is likely speculative allocation due to delalloc >>> (ext4 has to reserve worst-case metadata amounts to prepare for >>> delalloc writeback). =A0When the file data actually gets written ou= t, >>> the worst-case reservation is freed up again. =A0We also flush and >>> switch to nodelalloc when the filesystem is pretty close to full. >>> see ext4_nonda_switch() for example. >>> >>> This looks pretty severe though, more than I would expect >>> from that behavior. >> >> This is fixed in commit d330a5bef, which which got merged post >> 2.6.34-rc2, and which we need to get into 2.6.33 stable. =A0If you >> cherry-pick that commit, I think you'll see that it fixes this >> problem. > > Oh, right, spaced that one. =A0Thanks for the reminder Ted. =A0:) > > And from now on ext3-mounted-as-ext4 is special-cased so you won't ge= t > delalloc, and you won't get this behavior at all (nor will you get > any delalloc benefits, FWIW). > Out of curiosity, when you say ext3-mounted-as-ext4, are you referring to filesystems without ext4 features mounted -t ext4, or filesystems mounted -t ext3 when CONFIG_EXT4_USE_FOR_EXT23 is defined? -Justin -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" i= n the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html