From: Chris Mason <chris.mason@oracle.com>
To: Patrick Goetz <pgoetz@math.utexas.edu>
Cc: linux-btrfs@vger.kernel.org
Subject: Re: Atomicity or the ext4 open-write-close-rename debacle
Date: Wed, 08 Apr 2009 19:12:52 -0400 [thread overview]
Message-ID: <1239232372.31826.4.camel@think.oraclecorp.com> (raw)
In-Reply-To: <49DCECD5.3030801@math.utexas.edu>
On Wed, 2009-04-08 at 13:28 -0500, Patrick Goetz wrote:
> Chris Mason wrote:
> >
> > With 2.6.30, extra ordering is added to btrfs, making sure that metadata
> > and data are both atomically replaced during a rename. In other words,
> > for renames it will work like ext3 data=ordered mode.
> >
>
> Thanks for the speedy response.
>
> After spending several hours slogging through the discussion on Ted
> Tso's blog and spending much more time than anticipated learning about
> FUA, write barriers, fsync vs. fdatasync, how fsync is implemented in
> linux, etc., I'm curious about the technical details of how this is
> accomplished. Any place where I can find this short of reading through
> the source code?
The rename flushing is pretty simple. When one file replaces another
during rename, btrfs puts the new file into a list of things that must
be flushed before the transaction commits.
This way, we know the data is on disk before the rename metadata changes
are on disk.
-chris
prev parent reply other threads:[~2009-04-08 23:12 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-04-08 15:21 Atomicity or the ext4 open-write-close-rename debacle Patrick Goetz
2009-04-08 16:28 ` Chris Mason
2009-04-08 18:28 ` Patrick Goetz
2009-04-08 23:12 ` Chris Mason [this message]
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