Re: [PATCH 2/6] selftests/bpf: libarena: Inline nonatomic bitmap operations

> diff --git a/tools/testing/selftests/bpf/libarena/include/libarena/bitmap.h b/tools/testing/selftests/bpf/libarena/include/libarena/bitmap.h
> index 8c5936ae9958..163e2b83d943 100644
> --- a/tools/testing/selftests/bpf/libarena/include/libarena/bitmap.h
> +++ b/tools/testing/selftests/bpf/libarena/include/libarena/bitmap.h
> @@ -1,6 +1,8 @@
>  // SPDX-License-Identifier: LGPL-2.1 OR BSD-2-Clause
>  #pragma once
>
> +#include <bpf_atomic.h>
> +

Does this break host-includability?  The other libarena headers (common.h,
buddy.h, asan.h) deliberately keep themselves dual-use: common.h has an
explicit #else /* ! __BPF__ */ arm that defines __arena to nothing, and
buddy.h/asan.h fence their function declarations behind #ifdef __BPF__
while leaving structs visible.

Including bpf_atomic.h unconditionally pulls in vmlinux.h and
bpf/bpf_helpers.h:

tools/testing/selftests/bpf/bpf_atomic.h:
  #include <vmlinux.h>
  #include <bpf/bpf_helpers.h>
  #include <bpf_may_goto.h>

  extern bool CONFIG_X86_64 __kconfig __weak;

None of that is usable from a host compile. The Makefile adds both
-I$(CURDIR)/libarena/include and -I$(INCLUDE_DIR) (where vmlinux.h lives)
to COMMON_CFLAGS, so a host TU that includes bitmap.h would pull vmlinux.h
into a build that also has libc/uapi headers, under -Wall -Werror.

No host TU currently includes bitmap.h, so this is latent rather than
breaking the build right now, but it silently removes a property the
neighboring headers maintain.

The include is also redundant: all three existing consumers (bitmap.bpf.c,
test_bitmap.bpf.c, test_parallel_bitmap.bpf.c) already include
libarena/common.h, which pulls bpf_atomic.h indirectly via
bpf_arena_spin_lock.h at line 8. And it doesn't make the header
self-contained anyway - bitmap.h still relies on the includer for __arena,
u64, size_t, and bool.

Would #include <libarena/common.h>, or wrapping the new include and the
three inline bodies in #ifdef __BPF__ the way buddy.h does, keep the
dual-use property intact?

[ ... ]


---
AI reviewed your patch. Please fix the bug or email reply why it's not a bug.
See: https://github.com/kernel-patches/vmtest/blob/master/ci/claude/README.md

CI run summary: https://github.com/kernel-patches/bpf/actions/runs/32062809860