Re: bug in md write barrier support?

[Jens Axboe]

On Thu, Sep 09 2004, Alan Cox wrote:
> On Iau, 2004-09-09 at 09:29, Jens Axboe wrote:
> > > why does this seem broken? semantics of "cache flush guarantees that all
> > > io submitted prior to it hits the spindle" are quite sane imo; no
> > > guarantee of later submitted IO.. compare the unix "sync" command; same
> > > level of semantics.
> > 
> > Depends on your angle, I think it breaks the principle of least
> > surprise.
> 
> As far as I can ascertain raid controllers in general follow this set of
> semantics. Its less of an issue for many of them with battery backup
> obviously.
> 
> It also makes a lot of sense at the hardware level for performance
> especially when dealing with raid.

Yes. As long as the required semantics aren't explicitly guaranteed in
the specification, we should not rely on it.

-- 
Jens Axboe

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