From: NeilBrown <neilb@suse.de>
To: Jan Kara <jack@suse.cz>
Cc: "Darrick J. Wong" <darrick.wong@oracle.com>,
axboe@kernel.dk, lucho@ionkov.net, ericvh@gmail.com,
tytso@mit.edu, rminnich@sandia.gov, viro@zeniv.linux.org.uk,
martin.petersen@oracle.com, 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
Subject: Re: [PATCH 4/4] ext3: Warn if mounting rw on a disk requiring stable page writes
Date: Thu, 22 Nov 2012 08:47:13 +1100 [thread overview]
Message-ID: <20121122084713.69e5b1fc@notabene.brown> (raw)
In-Reply-To: <20121121213333.GF30250@quack.suse.cz>
[-- Attachment #1: Type: text/plain, Size: 3334 bytes --]
On Wed, 21 Nov 2012 22:33:33 +0100 Jan Kara <jack@suse.cz> wrote:
> 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 <darrick.wong@oracle.com>
> > > > ---
> > > > 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
Given this restriction, there is no way that I can change md/raid5 to set the
"stable pages" flag and stop copying pages into the stripe-cache. ext3 on
raid5 will be much too common to allow this breakage.
I would really like to be able to say "I prefer stable pages, but they aren't
a requirement as long as I know which is which" ....
NeilBrown
[-- Attachment #2: signature.asc --]
[-- Type: application/pgp-signature, Size: 828 bytes --]
next prev parent reply other threads:[~2012-11-22 19:05 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-11-21 2:00 [PATCH v2.1 0/3] mm/fs: Implement faster stable page writes on filesystems Darrick J. Wong
2012-11-21 2:00 ` [PATCH 1/4] bdi: Track users that require stable page writes Darrick J. Wong
2012-11-21 7:54 ` Christoph Hellwig
2012-11-21 10:52 ` Christoph Hellwig
2012-11-21 10:56 ` Christoph Hellwig
2012-11-21 21:52 ` Darrick J. Wong
2012-11-21 22:06 ` NeilBrown
2012-11-22 2:33 ` [PATCH] " Darrick J. Wong
2012-11-22 7:08 ` Christoph Hellwig
2012-11-21 2:00 ` [PATCH 2/4] mm: Only enforce stable page writes if the backing device requires it Darrick J. Wong
2012-11-21 10:57 ` Christoph Hellwig
2012-11-21 2:00 ` [PATCH 3/4] 9pfs: Fix filesystem to wait for stable page writeback Darrick J. Wong
2012-11-21 2:00 ` [PATCH 4/4] ext3: Warn if mounting rw on a disk requiring stable page writes Darrick J. Wong
2012-11-21 2:15 ` Jan Kara
2012-11-21 21:13 ` Darrick J. Wong
2012-11-21 21:33 ` Jan Kara
2012-11-21 21:47 ` NeilBrown [this message]
2012-11-22 1:47 ` Darrick J. Wong
2012-11-22 2:36 ` [RFC PATCH 1/2] mm: Introduce page flag to indicate stable page status Darrick J. Wong
2012-11-22 2:36 ` [RFC PATCH 2/2] jbd: Stabilize pages during writes when in ordered mode Darrick J. Wong
2012-11-22 9:19 ` Jan Kara
2012-11-22 9:12 ` [PATCH 4/4] ext3: Warn if mounting rw on a disk requiring stable page writes Jan Kara
2012-11-27 2:17 ` Darrick J. Wong
2012-12-05 12:12 ` Jan Kara
2012-12-08 1:09 ` Darrick J. Wong
2012-12-10 10:41 ` Jan Kara
2012-11-22 23:15 ` Dave Chinner
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20121122084713.69e5b1fc@notabene.brown \
--to=neilb@suse.de \
--cc=adilger.kernel@dilger.ca \
--cc=axboe@kernel.dk \
--cc=bharrosh@panasas.com \
--cc=darrick.wong@oracle.com \
--cc=david@fromorbit.com \
--cc=ericvh@gmail.com \
--cc=jack@suse.cz \
--cc=jlayton@samba.org \
--cc=linux-ext4@vger.kernel.org \
--cc=linux-fsdevel@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=lucho@ionkov.net \
--cc=martin.petersen@oracle.com \
--cc=rminnich@sandia.gov \
--cc=tytso@mit.edu \
--cc=v9fs-developer@lists.sourceforge.net \
--cc=viro@zeniv.linux.org.uk \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).