Re: [PATCH 1/7] Make DISCARD_BARRIER and DISCARD_NOBARRIER writesinstead of reads

From: Matthew Wilcox
Date: Thu Sep 03 2009 - 13:56:27 EST

On Thu, Sep 03, 2009 at 06:52:20PM +0100, David Woodhouse wrote:
> On Sat, 2009-08-29 at 19:03 -0400, Christoph Hellwig wrote:
> >
> > The commands are conceptually writes, and in the case of IDE and SCSI
> > commands actually are writes. They were only reads because we thought
> > that would interact better with the elevators. Now the elevators know
> > about discard requests, that advantage no longer exists.
> Can you drop the final sentence of that? It isn't true, and I never said
> it.

No, but you wouldn't give me a changelog entry, so I had to make
something up.

> s/. Now.*/, but that isn't necessary, and making them writes makes it
> easier for the low-level IDE and SCSI code to cope with the fact that
> the command has to be sent with a payload./


Matthew Wilcox Intel Open Source Technology Centre
"Bill, look, we understand that you're interested in selling us this
operating system, but compare it to ours. We can't possibly take such
a retrograde step."
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