From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jan Kara Subject: Re: [PATCH 4/4] ext3: Warn if mounting rw on a disk requiring stable page writes Date: Wed, 21 Nov 2012 22:33:33 +0100 Message-ID: <20121121213333.GF30250@quack.suse.cz> References: <20121121020027.10225.43206.stgit@blackbox.djwong.org> <20121121020056.10225.15220.stgit@blackbox.djwong.org> <20121121021543.GI10507@quack.suse.cz> <20121121211319.GA32202@blackbox.djwong.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Jan Kara , axboe@kernel.dk, lucho@ionkov.net, ericvh@gmail.com, tytso@mit.edu, rminnich@sandia.gov, viro@zeniv.linux.org.uk, martin.petersen@oracle.com, neilb@suse.de, david@fromorbit.com, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, adilger.kernel@dilger.ca, bharrosh@panasas.com, jlayton@samba.org, v9fs-developer@lists.sourceforge.net, linux-ext4@vger.kernel.org To: "Darrick J. Wong" Return-path: Received: from cantor2.suse.de ([195.135.220.15]:39246 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756624Ab2KVTPA (ORCPT ); Thu, 22 Nov 2012 14:15:00 -0500 Content-Disposition: inline In-Reply-To: <20121121211319.GA32202@blackbox.djwong.org> Sender: linux-fsdevel-owner@vger.kernel.org List-ID: On Wed 21-11-12 13:13:19, Darrick J. Wong wrote: > On Wed, Nov 21, 2012 at 03:15:43AM +0100, Jan Kara wrote: > > On Tue 20-11-12 18:00:56, Darrick J. Wong wrote: > > > ext3 doesn't properly isolate pages from changes during writeback. Since the > > > recommended fix is to use ext4, for now we'll just print a warning if the user > > > tries to mount in write mode. > > > > > > Signed-off-by: Darrick J. Wong > > > --- > > > fs/ext3/super.c | 8 ++++++++ > > > 1 file changed, 8 insertions(+) > > > > > > > > > diff --git a/fs/ext3/super.c b/fs/ext3/super.c > > > index 5366393..5b3725d 100644 > > > --- a/fs/ext3/super.c > > > +++ b/fs/ext3/super.c > > > @@ -1325,6 +1325,14 @@ static int ext3_setup_super(struct super_block *sb, struct ext3_super_block *es, > > > "forcing read-only mode"); > > > res = MS_RDONLY; > > > } > > > + if (!read_only && > > > + queue_requires_stable_pages(bdev_get_queue(sb->s_bdev))) { > > > + ext3_msg(sb, KERN_ERR, > > > + "error: ext3 cannot safely write data to a disk " > > > + "requiring stable pages writes; forcing read-only " > > > + "mode. Upgrading to ext4 is recommended."); > > > + res = MS_RDONLY; > > > + } > > > if (read_only) > > > return res; > > > if (!(sbi->s_mount_state & EXT3_VALID_FS)) > > Why this? ext3 should be fixed by your change to > > filemap_page_mkwrite()... Or does testing show otherwise? > > Yes, it's still broken even with this new set of changes. Now that I think > about it a little more, I recall that writeback mode was actually fine, so this > is a little harsh. > > Hm... looking at the ordered code a little more, it looks like > ext3_ordered_write_end is calling journal_dirty_data_fn, which (I guess?) tries > to write mapped buffers back through the journal? Taking it out seems to fix > ordered mode, though I have a suspicion that it might very well break ordered > mode too. Oh, right. kjournald writing buffers directly (without setting PageWriteback) will break things. So please, change warning to: /* * In data=ordered mode, kjournald writes buffers without setting * PageWriteback bit thus generic code does not properly wait for * writeback of those buffers to finish. */ if (!read_only && test_opt(sb, DATA_FLAGS) == EXT3_MOUNT_ORDERED_DATA && queue_requires_stable_pages(bdev_get_queue(sb->s_bdev))) { ext3_msg(sb, KERN_ERR, "error: data=ordered mode does not support stable " "page writes required by the disk; forcing read-only " "mode. Upgrading to ext4 is recommended."); res = MS_RDONLY; } then you need a similar check in ext3_remount() so that filesystem cannot be remounted read-write. Honza -- Jan Kara SUSE Labs, CR