On Sat, 25 May 2024 at 22:07, Linus Torvalds
<torvalds@xxxxxxxxxxxxxxxxxxxx> wrote:
>
> IOW, we could do something like the attached. I think it's actually
> almost a cleanup [..]
The reason I say that is this part of the patch:
-static inline struct fd __to_fd(unsigned long v)
+static inline struct fd __to_fd(struct rawfd raw)
{
- return (struct fd){(struct file *)(v & ~3),v & 3};
+ return (struct fd){fdfile(raw),fdflags(raw)};
}
which I think actually improves on our current situation.
No, my fdfile/fdflags functions aren't pretty, but they have more type
safety than the bare "unsigned long", and in that "__to_fd()" case I
think it actually makes that unpacking operation much more obvious.
It might be good to have the reverse "packing" helper inline function
too, so that __fdget() wouldn't do this:
return (struct rawfd) { FDPUT_FPUT | (unsigned long)file };
but instead have some kind of "mkrawfd()" helper that does the above,
and we'd have
return mkrawfd(file, FDPUT_FPUT);
instead. That would obviate my EMPTY_RAWFD macro, and we'd just use
"mkrawfd(NULL, 0)"?
Maybe this is bikeshedding. But I'd rather have this kind of explicit
one-word interface with a wrapped tagged pointer than have something
as subtle as your fd_empty() that magically generates better code in
certain very specific circumstances.
Linus
