linux-kernel - Re: [PATCH] selftests/mm: fix split huge page tests

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Date:   Tue, 7 Mar 2023 11:22:16 +0100
From:   David Hildenbrand <david@...hat.com>
To:     Zi Yan <ziy@...dia.com>, Andrew Morton <akpm@...ux-foundation.org>,
        linux-mm@...ck.org
Cc:     linux-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org,
        Shuah Khan <shuah@...nel.org>,
        Zach O'Keefe <zokeefe@...gle.com>
Subject: Re: [PATCH] selftests/mm: fix split huge page tests

On 06.03.23 17:09, Zi Yan wrote:
> From: Zi Yan <ziy@...dia.com>
> 
> Fixed two inputs to check_anon_huge() and one if condition, so the tests
> work as expected.
> 
> Fixes: c07c343cda8e ("selftests/vm: dedup THP helpers")
> Signed-off-by: Zi Yan <ziy@...dia.com>
> Cc: Zach O'Keefe <zokeefe@...gle.com>
> ---
>   tools/testing/selftests/mm/split_huge_page_test.c | 6 +++---
>   1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/tools/testing/selftests/mm/split_huge_page_test.c b/tools/testing/selftests/mm/split_huge_page_test.c
> index 76e1c36dd9e5..b8558c7f1a39 100644
> --- a/tools/testing/selftests/mm/split_huge_page_test.c
> +++ b/tools/testing/selftests/mm/split_huge_page_test.c
> @@ -106,7 +106,7 @@ void split_pmd_thp(void)
>   	for (i = 0; i < len; i++)
>   		one_page[i] = (char)i;
>   
> -	if (!check_huge_anon(one_page, 1, pmd_pagesize)) {
> +	if (!check_huge_anon(one_page, 4, pmd_pagesize)) {
>   		printf("No THP is allocated\n");
>   		exit(EXIT_FAILURE);
>   	}
> @@ -122,7 +122,7 @@ void split_pmd_thp(void)
>   		}
>   
>   
> -	if (check_huge_anon(one_page, 0, pmd_pagesize)) {
> +	if (!check_huge_anon(one_page, 0, pmd_pagesize)) {
>   		printf("Still AnonHugePages not split\n");
>   		exit(EXIT_FAILURE);
>   	}
> @@ -169,7 +169,7 @@ void split_pte_mapped_thp(void)
>   	for (i = 0; i < len; i++)
>   		one_page[i] = (char)i;
>   
> -	if (!check_huge_anon(one_page, 1, pmd_pagesize)) {
> +	if (!check_huge_anon(one_page, 4, pmd_pagesize)) {
>   		printf("No THP is allocated\n");
>   		exit(EXIT_FAILURE);
>   	}

Hard to read. It should probably be "get_huge_anon()" to then check for 
the value in the caller manually. Negative value could be used as an 
indicator for an error obtaining the value.

Anyhow, was briefly confused about the 4 ("magic value" also apprearing 
in "size_t len = 4 * pmd_pagesize;") but it seems to be the right thing 
to do.

Acked-by: David Hildenbrand <david@...hat.com>

-- 
Thanks,

David / dhildenb