From: NeilBrown <neilb@suse.de>
To: Jan Kara <jack@suse.cz>
Cc: "Darrick J. Wong" <darrick.wong@oracle.com>,
Theodore Ts'o <tytso@mit.edu>,
linux-ext4 <linux-ext4@vger.kernel.org>,
linux-fsdevel <linux-fsdevel@vger.kernel.org>
Subject: Re: [RFC PATCH 1/2] bdi: Create a flag to indicate that a backing device needs stable page writes
Date: Tue, 30 Oct 2012 10:48:37 +1100 [thread overview]
Message-ID: <20121030104837.2e4b06fc@notabene.brown> (raw)
In-Reply-To: <20121029183051.GJ18767@quack.suse.cz>
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On Mon, 29 Oct 2012 19:30:51 +0100 Jan Kara <jack@suse.cz> wrote:
> On Mon 29-10-12 19:13:58, Jan Kara wrote:
> > On Fri 26-10-12 18:35:24, Darrick J. Wong wrote:
> > > This creates BDI_CAP_STABLE_WRITES, which indicates that a device requires
> > > stable page writes. It also plumbs in a sysfs attribute so that admins can
> > > check the device status.
> > >
> > > Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
> > I guess Jens Axboe <axboe@kernel.dk> would be the best target for this
> > patch (so that he can merge it). The patch looks OK to me. You can add:
> > Reviewed-by: Jan Kara <jack@suse.cz>
> One more thing popped up in my mind: What about NFS, Ceph or md RAID5?
> These could (at least theoretically) care about stable writes as well. I'm
> not sure if they really started to use them but it would be good to at
> least let them know.
>
What exactly are the semantics of BDI_CAP_STABLE_WRITES ?
If I set it for md/RAID5, do I get a cast-iron guarantee that no byte in any
page submitted for write will ever change until after I call bio_endio()?
If so, is this true for all filesystems? - I would expect a bigger patch would
be needed for that.
If not, what exactly are the semantics?
Thanks,
NeilBrown
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next prev parent reply other threads:[~2012-10-29 23:48 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-10-26 10:19 semi-stable page writes Darrick J. Wong
2012-10-27 1:35 ` [RFC PATCH 1/2] bdi: Create a flag to indicate that a backing device needs stable " Darrick J. Wong
2012-10-29 18:13 ` Jan Kara
2012-10-29 18:30 ` Jan Kara
2012-10-29 23:48 ` NeilBrown [this message]
2012-10-30 0:10 ` Jan Kara
2012-10-30 0:34 ` NeilBrown
2012-10-30 13:38 ` Jan Kara
2012-10-30 21:49 ` NeilBrown
2012-10-30 4:10 ` Martin K. Petersen
2012-10-30 4:48 ` NeilBrown
2012-10-30 12:19 ` Martin K. Petersen
2012-10-30 20:14 ` Darrick J. Wong
2012-10-30 22:14 ` NeilBrown
2012-10-30 23:58 ` Boaz Harrosh
2012-10-31 8:56 ` Darrick J. Wong
2012-10-31 11:56 ` Jan Kara
2012-10-31 19:36 ` Darrick J. Wong
2012-10-31 23:12 ` Boaz Harrosh
2012-11-01 5:51 ` Darrick J. Wong
2012-11-01 6:25 ` Boaz Harrosh
2012-11-01 8:59 ` Jan Kara
2012-11-01 17:24 ` Boaz Harrosh
2012-11-01 22:42 ` Jan Kara
2012-10-30 22:40 ` Boaz Harrosh
2012-10-27 1:36 ` [RFC PATCH 2/2] mm: Gate stable page writes on the bdi flag Darrick J. Wong
2012-10-29 18:28 ` Jan Kara
2012-10-31 8:58 ` Darrick J. Wong
2012-10-29 22:01 ` semi-stable page writes Dave Chinner
2012-10-30 1:00 ` Theodore Ts'o
2012-10-30 23:30 ` Dave Chinner
2012-10-31 11:45 ` Jan Kara
2012-10-30 20:40 ` Darrick J. Wong
2012-10-30 23:43 ` Dave Chinner
2012-10-31 9:05 ` Darrick J. Wong
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