Re: [PATCH 3/3] include/uapi/linux/swab: Fix potentially missing __always_inline

Petr Vaněk
2021-07-28T13:53:39Z

On Tue, Jul 27, 2021 at 04:11:19PM +0200, Pavo Banicevic wrote:
> From: Matt Redfearn <matt.redfearn@mips.com>
>
> Commit bc27fb68aaad ("include/uapi/linux/byteorder, swab: force inlining
> of some byteswap operations") added __always_inline to swab functions
> and commit 283d75737837 ("uapi/linux/stddef.h: Provide __always_inline to
> userspace headers") added a definition of __always_inline for use in
> exported headers when the kernel's compiler.h is not available.
>
> However, since swab.h does not include stddef.h, if the header soup does
> not indirectly include it, the definition of __always_inline is missing,
> resulting in a compilation failure, which was observed compiling the
> perf tool using exported headers containing this commit:
>
> In file included from /usr/include/linux/byteorder/little_endian.h:12:0,
> from /usr/include/asm/byteorder.h:14,
> from tools/include/uapi/linux/perf_event.h:20,
> from perf.h:8,
> from builtin-bench.c:18:
> /usr/include/linux/swab.h:160:8: error: unknown type name `__always_inline'
> static __always_inline __u16 __swab16p(const __u16 *p)
>
> Fix this by replacing the inclusion of linux/compiler.h with
> linux/stddef.h to ensure that we pick up that definition if required,
> without relying on it's indirect inclusion. compiler.h is then included
> indirectly, via stddef.h.
>
> Fixes: 283d75737837 ("uapi/linux/stddef.h: Provide __always_inline to userspace headers")
>
> Signed-off-by: Matt Redfearn <matt.redfearn@mips.com>
> ---

I use this patch in order to fix __always_inline issue for kernels
5.12+, see https://lore.kernel.org/lkml/YPGXXt6Z3O1W0AYS@arkam/ .
I believe this is the correct solution.

Reviewed-by: Petr Vaněk <arkamar@atlas.cz>