Re: [PATCH][RFC] splice support

[Jens Axboe]

On Wed, Mar 29 2006, Andrew Morton wrote:
> Jens Axboe <axboe@xxxxxxx> 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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