From: Dave Chinner <david@fromorbit.com>
To: Jan Kara <jack@suse.cz>
Cc: mingming cao <mingming@oracle.com>,
linux-fsdevel@vger.kernel.org, lsf-pc@lists.linux-foundation.org
Subject: Re: [Lsf-pc] [LSF/MM][ATTEND]filesystem -- reflink
Date: Fri, 17 Jan 2014 11:07:38 +1100 [thread overview]
Message-ID: <20140117000738.GC18112@dastard> (raw)
In-Reply-To: <20140115090312.GA6732@quack.suse.cz>
On Wed, Jan 15, 2014 at 10:03:12AM +0100, Jan Kara wrote:
> Hello,
>
> On Tue 14-01-14 23:16:20, mingming cao wrote:
> > I'd like to attend Linux storage and filesystem summit. I am
> > interested in discussion of general lockless direct io and more
> > interested in discussion of reflink support for filesystem. Btrfs
> > and OCFS2 has this support, My goal is explore what's best to way
> > this support for ext4. If there is any crossover work between
> > filesystem and vfs people, or filesystem and dm layer I am more than
> > happy to discuss about it too.
> There was a project for implementing COW for ext4 but it was a really
> major surgery and in the end didn't get to an upstreamable state. Reflink
> is somewhat simpler than general COW because it's only about fs data. In
> particular implementing reflink with a file granularity (i.e., a type of
> hardlink which is automatically converted to a copy when first opened for
> writing) is relatively simple to do but I'm not sure how useful it is.
> Doing reflink properly with block granularity is harder with block
> refcounting etc.
>
> Do you have any particular usecase in mind?
The use case I keep hearing for reflink in XFS is optimising
distributed filesystem snapshot implementations, which tend to
require file block level COW semantics on a per-file basis...
Cheers,
Dave.
--
Dave Chinner
david@fromorbit.com
prev parent reply other threads:[~2014-01-17 0:08 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-01-15 7:16 [LSF/MM][ATTEND]filesystem -- reflink mingming cao
2014-01-15 9:03 ` [Lsf-pc] " Jan Kara
2014-01-17 0:07 ` Dave Chinner [this message]
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