Re: [PATCH][RFC] splice support

[Andrew Morton <akpm@osdl.org>]

Linus Torvalds <torvalds@osdl.org> wrote:
>
>  > - why is the `flags' arg to sys_splice() unsigned long?  Can it be `int'?
> 
>  flags are always unsigned long, haven't you noticed?

<does `man 2 open', gets confused>

> Besides, they should 
>  never be signed, if you do bitmasks and shifting on them: "int" is 
>  strictly worse than "unsigned" when we're talking flags.

Sure, but is there any gain in making flags 64-bit on 64-bit machines when
we cannot use more than 32 bits in there anyway?

> 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.