Re: [Cluster-devel] fallocate vs O_(D)SYNC

[Chris Mason <chris.mason@oracle.com>]

On Wed, Nov 16, 2011 at 04:57:55PM +0100, Jan Kara wrote:
> 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.

We should do it per FS though, I'll patch up btrfs.

-chris