Subject: Re: [PATCH] barrier patch set
From: Chris Mason <mason@suse.com>
To: "Stephen C. Tweedie" <sct@redhat.com>
Cc: Jeff Garzik <jgarzik@pobox.com>,
       Bartlomiej Zolnierkiewicz <B.Zolnierkiewicz@elka.pw.edu.pl>,
       Jens Axboe <axboe@suse.de>, Linux Kernel <linux-kernel@vger.kernel.org>
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On Wed, 2004-03-31 at 09:08, Stephen C. Tweedie wrote:
> Hi,
> 
> On Tue, 2004-03-30 at 23:21, Jeff Garzik wrote:
> 
> > For IDE, O_DIRECT and O_SYNC can use special "FUA" commands, which don't 
> > return until the data is on the platter.
> 
> fsync() is still really nasty, because that can require that we wait on
> IO that was submitted by the VM before we knew that there was a
> synchronous IO wait coming.  

Yes, it gets ugly in a hurry.  Jeff, look at the whole thread about the
O_DIRECT read vs buffered write races.  I don't think we can use FUA for
fsync or O_SYNC without using it for every write.

We might be able to get away with using it on O_DIRECT.

-chris


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