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

[Alan Cox]

On Fri, 5 Dec 2008 02:37:39 +0100
Andi Kleen <andi at firstfloor.org> wrote:

> > * barrier support in md-raid1 deviates from the specification at 
> > Documentation/block/barrier.txt. The specification says that requests 
> > submitted after the barrier request hit the media after the barrier 
> > request hits the media. The reality is that the barrier request can be 
> > randomly aborted and the requests submitted after it hit the media before 
> > the barrier request.
> 
> Yes the spec should be probably updated.
> 
> But also see Linus' rant from yesterday about code vs documentation.
> When in doubt the code wins.

Not when the fundamental design of the code is broken and trashes
performance. The documented behaviour is strongly desirable.

Alan