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SubjectRe: [PATCH][RFC] splice support
On Wed, Mar 29 2006, Andrew Morton wrote:
> Jens Axboe <axboe@suse.de> wrote:
> >
> > > > Right now "flags" doesn't do anything at all, and you should just pass in
> > > > zero.
> > >
> > > In that case perhaps we should be enforcing flags==0 so that future
> > > flags-using applications will reliably fail on old flags-not-understanding
> > > kernels.
> > >
> > > But that won't work if we later define a bit in flags to mean "behave like
> > > old kernels used to". So perhaps we should require that bits 0-15 of
> > > `flags' be zero and not care about bits 16-31.
> > >
> > > IOW: it might be best to make `flags' just go away, and add new syscalls in
> > > the future as appropriate.
> >
> > Not if flags == 0 maintains the same behaviour. The only flag I can
> > think of right now is the 'move' or 'gift' flag, meaning that the caller
> > wants to migrate pages from the pipe instead of copying them. I'd
> > imagine we'd get that in way before 2.6.17 anyways, so I think we're
> > fine.
>
> OK.. Do you plan to make it reject unrecognised flags?

Depends, not sure if eg a 'move' flag should be a hard or soft
indication. Say we can't move a page and the caller asked us to migrate,
we'd probably just do the sane thing and copy that one page. It would be
silly to fail that request entirely.

--
Jens Axboe

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