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

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Message-ID: <20111116133915.GD8195@quack.suse.cz>
Date:	Wed, 16 Nov 2011 14:39:15 +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 07:45:50, Christoph Hellwig wrote:
> On Wed, Nov 16, 2011 at 11:54:13AM +0100, Jan Kara wrote:
> >   Yeah, only that nobody calls that fsync() automatically if the fd is
> > O_SYNC if I'm right. But maybe calling fdatasync() on the range which was
> > fallocated from sys_fallocate() if the fd is O_SYNC would do the trick for
> > most filesystems? That would match how we treat O_SYNC for other operations
> > as well. I'm just not sure whether XFS wouldn't take unnecessarily big hit
> > with this.
> 
> 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?

								Honza
-- 
Jan Kara <jack@...e.cz>
SUSE Labs, CR
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