From: "Darrick J. Wong" <darrick.wong@oracle.com>
To: Trond Myklebust <trondmy@hammerspace.com>
Cc: "linux-fsdevel@vger.kernel.org" <linux-fsdevel@vger.kernel.org>,
"linux-nfs@vger.kernel.org" <linux-nfs@vger.kernel.org>
Subject: Re: Question about clone_range() metadata stability
Date: Wed, 27 Nov 2019 12:21:36 -0800 [thread overview]
Message-ID: <20191127202136.GV6211@magnolia> (raw)
In-Reply-To: <f063089fb62c219ea6453c7b9b0aaafd50946dae.camel@hammerspace.com>
On Wed, Nov 27, 2019 at 06:38:46PM +0000, Trond Myklebust wrote:
> Hi all
>
> A quick question about clone_range() and guarantees around metadata
> stability.
>
> Are users required to call fsync/fsync_range() after calling
> clone_range() in order to guarantee that the cloned range metadata is
> persisted?
Yes.
> I'm assuming that it is required in order to guarantee that
> data is persisted.
Data and metadata. XFS and ocfs2's reflink implementations will flush
the page cache before starting the remap, but they both require fsync to
force the log/journal to disk.
(AFAICT the same reasoning applies to btrfs, but don't trust my word for
it.)
> I'm asking because knfsd currently just does a call to
> vfs_clone_file_range() when parsing a NFSv4.2 CLONE operation. It does
> not call fsync()/fsync_range() on the destination file, and since the
> NFSv4.2 protocol does not require you to perform any other operation in
> order to persist data/metadata, I'm worried that we may be corrupting
> the cloned file if the NFS server crashes at the wrong moment after the
> client has been told the clone completed.
That analysis seems correct.
--D
> Cheers
> Trond
> --
> Trond Myklebust
> Linux NFS client maintainer, Hammerspace
> trond.myklebust@hammerspace.com
>
>
next prev parent reply other threads:[~2019-11-27 20:21 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-11-27 18:38 Question about clone_range() metadata stability Trond Myklebust
2019-11-27 20:21 ` Darrick J. Wong [this message]
2019-11-29 12:43 ` Filipe Manana
2019-12-01 21:05 ` Dave Chinner
2019-12-02 17:09 ` Darrick J. Wong
2019-12-03 7:36 ` Trond Myklebust
2019-12-03 16:35 ` Darrick J. Wong
2019-12-03 23:00 ` Trond Myklebust
2019-12-06 1:31 ` Dave Chinner
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