From: Matt Mackall Subject: Re: Add a norecovery option to ext3/4? Date: Tue, 10 Apr 2007 11:44:51 -0500 Message-ID: <20070410164451.GC10459@waste.org> References: <20070409000556.GA13980@implementation> <461A5F13.7040705@cfl.rr.com> <461A760B.1040103@redhat.com> <20070410072253.GA28665@lazybastard.org> <20070410112718.GF13650@thunk.org> <20070410120825.GA29487@lazybastard.org> Mime-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: QUOTED-PRINTABLE Cc: Theodore Tso , Eric Sandeen , Phillip Susi , Samuel Thibault , linux-ext4@vger.kernel.org, linux-kernel@vger.kernel.org To: =?iso-8859-1?Q?J=F6rn?= Engel Return-path: Content-Disposition: inline In-Reply-To: <20070410120825.GA29487@lazybastard.org> Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-ext4.vger.kernel.org On Tue, Apr 10, 2007 at 02:08:26PM +0200, J=F6rn Engel wrote: > On Tue, 10 April 2007 07:27:18 -0400, Theodore Tso wrote: > >=20 > > I suppose what you could do is to read in the journal, and use it t= o > > create an remapping table so that when you want to read block #5126= , > > and block number 5126 is in the journal, to read the journal versio= n > > of the block instead of the one on disk. That would allow for safe > > access to a filesystem being mounted read-only without the journal > > being present. >=20 > Another option would be to access the medium through a mapping inode, > replay the journal into the mapping inode and _not_ flush the dirty > pages. But as long as a remapping table is sufficient for ext3 journ= al > format, such a table should be simpler and faster. Or you could make a snapshot with device-mapper and then mount it. Requires some free disk space somewhere (or a hack with loop on tmpfs), but should be doable today. --=20 Mathematics is the supreme nostalgia of our time.