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

Jan Kara jack at suse.cz
Wed Nov 16 15:57:55 UTC 2011


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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