Re: UNMAP is a hint

Matthew Wilcox
2008-11-10T17:30:20Z

On Mon, Nov 10, 2008 at 12:05:57PM -0500, Black_David@emc.com wrote:
> > On Mon, 2008-11-10 at 19:31 +1100, Dave Chinner wrote:
> > > I think this is the crux of the issue. IMO, it's not much of a
> standard
> > > when the spirit of the standard is to allow everyone to implement
> > > different, non-deterministic behaviour....
> >
> > I disagree. The discard request is a _hint_ from the upper layers, and
> > the storage device can act on that hint as it sees fit. There's
> nothing
> > wrong with that; it doesn't make it "not much of a standard".
>
> Bingo! That is exactly the spirit and thinking behind the UNMAP
> proposal.

While that may be, it's hardly the spirit that Ric (at least) has been
promoting with dire warnings about how 'Enterprise class' customers will
react if Linux does the wrong thing for EMC arrays with discard/trim/unmap.

--
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."