Re: [PATCH 4/5] uapi: always define F_GETLK64/F_SETLK64/F_SETLKW64 in fcntl.h

[Christoph Hellwig]

On Tue, Jan 11, 2022 at 04:33:30PM +0100, Arnd Bergmann wrote:
> This is a very subtle change to the exported UAPI header contents:
> On 64-bit architectures, the three unusable numbers are now always
> shown, rather than depending on a user-controlled symbol.

Well, the change is bigger and less subtle.  Before this change the
constants were never visible to userspace at all (except on mips),
because the #ifdef CONFIG_64BIT it never set for userspace builds.

> This is probably what we want here for compatibility reasons, but I think
> it should be explained in the changelog text, and I'd like Jeff or Bruce
> to comment on it as well: the alternative here would be to make the
> uapi definition depend on __BITS_PER_LONG==32, which is
> technically the right thing to do but more a of a change.

I can change this to #if __BITS_PER_LONG==32 || defined(__KERNEL__),
but it will still be change in what userspace sees.