linux-ext4 - Re: [Cluster-devel] fallocate vs O

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Message-ID: <20111116155755.GA22284@quack.suse.cz>
Date:	Wed, 16 Nov 2011 16:57:55 +0100
From:	Jan Kara <jack@...e.cz>
To:	Christoph Hellwig <hch@...radead.org>
Cc:	Jan Kara <jack@...e.cz>, Steven Whitehouse <swhiteho@...hat.com>,
	linux-btrfs@...r.kernel.org, linux-ext4@...r.kernel.org,
	mfasheh@...e.com, jlbec@...lplan.org, cluster-devel@...hat.com
Subject: Re: [Cluster-devel] fallocate vs O_(D)SYNC

On Wed 16-11-11 08:42:34, Christoph Hellwig wrote:
> On Wed, Nov 16, 2011 at 02:39:15PM +0100, Jan Kara wrote:
> > > This would work fine with XFS and be equivalent to what it does for
> > > O_DSYNC now.  But I'd rather see every filesystem do the right thing
> > > and make sure the update actually is on disk when doing O_(D)SYNC
> > > operations.
> >   OK, I don't really have a strong opinion here. Are you afraid that just
> > calling fsync() need not be enough to push all updates fallocate did to
> > disk?
> 
> No, the point is that you should not have to call fsync when doing
> O_SYNC I/O.  That's the whole point of it.
  I agree with you that userspace shouldn't have to call fsync. What I
meant is that sys_fallocate() or do_fallocate() can call
generic_write_sync(file, pos, len), and that would be completely
transparent to userspace.

									Honza
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