From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from frost.carfax.org.uk ([85.119.82.111]:56369 "EHLO frost.carfax.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932109AbbKXXGq (ORCPT ); Tue, 24 Nov 2015 18:06:46 -0500 Date: Tue, 24 Nov 2015 23:06:41 +0000 From: Hugo Mills To: Christoph Anton Mitterer Cc: Eric Sandeen , Austin S Hemmelgarn , Duncan <1i5t5.duncan@cox.net>, linux-btrfs@vger.kernel.org Subject: Re: shall distros run btrfsck on boot? Message-ID: <20151124230641.GW24333@carfax.org.uk> References: <1448340211.14125.44.camel@scientia.net> <56549AFB.3040904@redhat.com> <1448385809.21291.22.camel@scientia.net> <5654CAE0.5040907@gmail.com> <5654E427.6060708@redhat.com> <20151124223349.GV24333@carfax.org.uk> <1448406109.21291.97.camel@scientia.net> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="8fFQOkr0mRRE6sJ/" In-Reply-To: <1448406109.21291.97.camel@scientia.net> Sender: linux-btrfs-owner@vger.kernel.org List-ID: --8fFQOkr0mRRE6sJ/ Content-Type: text/plain; charset=us-ascii Content-Disposition: inline On Wed, Nov 25, 2015 at 12:01:49AM +0100, Christoph Anton Mitterer wrote: > On Tue, 2015-11-24 at 22:33 +0000, Hugo Mills wrote: > > whereas a read-only mount of a journalling FS _must_ modify the disk > > data after an unclean shitdown, in order to be useful (because the FS > > isn't consistent without the journal replay). > I've always considered that rather a bug,... or at least a very > annoying handling in ext* > If I specify "read-only" than nothing should ever be written. > If that's not possible because of an unclean shutdown and a journal > that needs to be replayed, the mount should (without any further > special option) rather fail then mount it pseudo-read-only. At one point, I _think_, btrfs did replay the log tree unconditionally, even on a RO mount, but it doesn't any more. There was certainly some discussion on the point. It's actually quite handy sometimes -- if you have a corrupt log tree, you can check it by mounting RO (when it works) and RW (when it fails because the log tree is broken), and the do btrfs-zero-log to clear it. For the record, this is about the only good use for btrfs-zero-log. It doesn't magically fix anything else. (Yes, this is another futile attempt at killing the persistent "btrfs-zero-log fixes everything" meme that's been doing the rounds for the last few years). Hugo. -- Hugo Mills | Never underestimate the bandwidth of a Volvo filled hugo@... carfax.org.uk | with backup tapes. http://carfax.org.uk/ | PGP: E2AB1DE4 | --8fFQOkr0mRRE6sJ/ Content-Type: application/pgp-signature; name="signature.asc" Content-Description: Digital signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.12 (GNU/Linux) iQIcBAEBAgAGBQJWVO2BAAoJEFheFHXiqx3kowUP/Aj108zjFmNOArmP66rXeJfW sJTNZ/GGyVA1ylLyv4akZ+Yd0VCiWKFsjJ/uviN49b4vY+qyxeTMzRwy4OLgT++D QsBWUygXwDuF/Rt/js87BWz1Y55zk1Od2OFUgcLmWXo5Xij5AiaauEIIe7UZ7xiM 2gsoc7Qw0TTCqfmoL/5OimFHkM30EUH7MtWqvLhdgKYdujY9o1QH0mZx5l8AMYW/ x7ZCPr5xz38K7c4zOcEh9gfFcIJentM37T70cHORwGDXEVqTOWaYGyPOcGyGITgr LUrLIQw5cuVy1azdRG4KDYQ9GP0yOJ3Vh2vzvNGpU0oI/4hNh1VhZMOMNVY/qvgp fzKYnrjoGFF58t0IJitgV8UF61qmR0wA0T0N1QT/qOs26lP65sZ2emwA7K3GCtQP 9ENxUcYt6u9Hq4CAXxjvqWclUW7r5QCU/GKFvKl2/i2hi6WdlijZPjYy2Wz7j13h KtVQH9gq3PlqgMJdY1uGnL/lHjT3WgLfgf/rGY3O3JUOrkr/yU1bFDCzZBigz7De HRUXhUaLJPreatkvM1BLRjSwWRyY5TNxKUiu7aQY5VSw2WM6g8tUMlPjREChnI1c Oiuw0RjUlqqo8F3UjsBEe0ewdtifeukDbjjgwKybnt89BMQSJSyqazyf+FGvi7T3 3lB0A9HgAa+7qoPfZt2j =H3Eu -----END PGP SIGNATURE----- --8fFQOkr0mRRE6sJ/--