linux-kernel - Re: [PATCH] selftests/mm: refactor common code and improve test skipping in guard

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Message-ID: <1efa2f5a-d93f-439a-9363-ff3a24a5e209@lucifer.local>
Date: Mon, 14 Jul 2025 15:20:08 +0100
From: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
To: wang lian <lianux.mm@...il.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>, Mark Brown <broonie@...nel.org>,
        David Hildenbrand <david@...hat.com>, SeongJae Park <sj@...nel.org>,
        Zi Yan <ziy@...dia.com>, linux-kernel@...r.kernel.org,
        Christian Brauner <brauner@...nel.org>, Jann Horn <jannh@...gle.com>,
        Liam Howlett <Liam.Howlett@...cle.com>, Shuah Khan <shuah@...nel.org>,
        Vlastimil Babka <vbabka@...e.cz>, gkwang <gkwang@...x-info.com>,
        p1ucky0923 <p1ucky0923@...il.com>, ryncsn <ryncsn@...il.com>,
        "zijing . zhang" <zijing.zhang@...ton.me>,
        linux-kselftest@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH] selftests/mm: refactor common code and improve test
 skipping in guard_region

On Mon, Jul 14, 2025 at 09:00:09PM +0800, wang lian wrote:
> Move the generic `FORCE_READ` macro from `guard-regions.c` to the shared
> `vm_util.h` header to promote code reuse.
>
> In `guard-regions.c`, replace `ksft_exit_skip()` with the `SKIP()` macro
> to ensure only the current test is skipped on permission failure, instead
> of terminating the entire test binary.
>
> Signed-off-by: wang lian <lianux.mm@...il.com>

LGTM, so:

Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>

> ---
>  tools/testing/selftests/mm/guard-regions.c | 9 +--------
>  tools/testing/selftests/mm/vm_util.h       | 7 +++++++
>  2 files changed, 8 insertions(+), 8 deletions(-)
>
> diff --git a/tools/testing/selftests/mm/guard-regions.c b/tools/testing/selftests/mm/guard-regions.c
> index 93af3d3760f9..b0d42eb04e3a 100644
> --- a/tools/testing/selftests/mm/guard-regions.c
> +++ b/tools/testing/selftests/mm/guard-regions.c
> @@ -35,13 +35,6 @@
>  static volatile sig_atomic_t signal_jump_set;
>  static sigjmp_buf signal_jmp_buf;
>
> -/*
> - * Ignore the checkpatch warning, we must read from x but don't want to do
> - * anything with it in order to trigger a read page fault. We therefore must use
> - * volatile to stop the compiler from optimising this away.
> - */
> -#define FORCE_READ(x) (*(volatile typeof(x) *)x)
> -
>  /*
>   * How is the test backing the mapping being tested?
>   */
> @@ -582,7 +575,7 @@ TEST_F(guard_regions, process_madvise)
>
>  	/* OK we don't have permission to do this, skip. */
>  	if (count == -1 && errno == EPERM)
> -		ksft_exit_skip("No process_madvise() permissions, try running as root.\n");
> +		SKIP(return, "No process_madvise() permissions, try running as root.\n");

Lol oops! :P yes thi is better.

>
>  	/* Returns the number of bytes advised. */
>  	ASSERT_EQ(count, 6 * page_size);
> diff --git a/tools/testing/selftests/mm/vm_util.h b/tools/testing/selftests/mm/vm_util.h
> index 2b154c287591..c20298ae98ea 100644
> --- a/tools/testing/selftests/mm/vm_util.h
> +++ b/tools/testing/selftests/mm/vm_util.h
> @@ -18,6 +18,13 @@
>  #define PM_SWAP                       BIT_ULL(62)
>  #define PM_PRESENT                    BIT_ULL(63)
>
> +/*
> + * Ignore the checkpatch warning, we must read from x but don't want to do
> + * anything with it in order to trigger a read page fault. We therefore must use
> + * volatile to stop the compiler from optimising this away.
> + */
> +#define FORCE_READ(x) (*(volatile typeof(x) *)x)
> +

Cool makes sense to share this.

If this contradicts previous review, take this review to be the correct one
:P

>  extern unsigned int __page_size;
>  extern unsigned int __page_shift;
>
> --
> 2.43.0
>