Re: Device loses barrier support (was: Fixed patch for simplebarriers.)

From: Alan Cox
Date: Fri Dec 05 2008 - 06:54:15 EST

On Fri, 5 Dec 2008 02:37:39 +0100
Andi Kleen <andi@xxxxxxxxxxxxxx> 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.

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