Device loses barrier support (was: Fixed patch for simple barriers.)

[Christoph Hellwig]

On Thu, Dec 04, 2008 at 06:48:38PM +0100, Andi Kleen wrote:
> I think. Just the low level xfs_buf interface happens to use the asynchronous
> callbacks instead of calling into the block layer directly like jbd et.al.
> do.

Only delwri buffers are delayed in XFS, but the journaling code only
uses async buffers which *synchronously* call into the block layer, but
just don't wait for it to complete..