From: Ric Wheeler Subject: Re: [PATCH] e2fsck: Discard free data and inode blocks. Date: Fri, 22 Oct 2010 07:30:46 -0400 Message-ID: <4CC175E6.5000700@gmail.com> References: <1287670556-23460-1-git-send-email-lczerner@redhat.com> <6388FD2D-50A8-42B9-A955-3824451ACBF4@dilger.ca> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: Andreas Dilger , linux-ext4@vger.kernel.org, tytso@mit.edu, sandeen@redhat.com To: Lukas Czerner Return-path: Received: from mail-gx0-f174.google.com ([209.85.161.174]:38467 "EHLO mail-gx0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751080Ab0JVL3d (ORCPT ); Fri, 22 Oct 2010 07:29:33 -0400 Received: by gxk23 with SMTP id 23so297375gxk.19 for ; Fri, 22 Oct 2010 04:29:32 -0700 (PDT) In-Reply-To: Sender: linux-ext4-owner@vger.kernel.org List-ID: On 10/22/2010 05:12 AM, Lukas Czerner wrote: > On Thu, 21 Oct 2010, Andreas Dilger wrote: > >> On 2010-10-21, at 08:15, Lukas Czerner wrote: >>> In Pass 5 when we are checking block and inode bitmaps we have great >>> opportunity to discard free space and unused inodes on the device, >>> because bitmaps has just been verified as valid. This commit takes >>> advantage of this opportunity and discards both, all free space and >>> unused inodes. >>> >>> I have added new option '-K' which when set, disables discard. Also when >>> the underlying device does not support discard, or BLKDISCARD ioctl >>> returns any kind of error, or when some errors occurred in bitmaps, the >>> discard is disabled. >> I'm always a bit nervous with patches like this, that will prevent data recovery after an e2fsck run (which seems like the opposite of what we want from e2fsck). >> >> Two suggestions: >> - it probably makes sense to disable this by default, and allow it to be >> specified on the command-line and e2fsck.conf >> - should we really have a short option, or a "-E discard" and "-E nodiscard" >> options, which allow us to change the default easily at some later time >> (which we can't do with a single -K flag) > Right, I agree it would be probably better to disable this by default. > > If we do disable it by default, I think that we might also want to be consistent and disable the discard support in mkfs by default as well? thanks! Ric