linux-kernel - Re: [PATCH] selftests/mm: Replace obsolete memalign() with posix

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Date:   Wed, 12 Apr 2023 10:25:19 +0200
From:   David Hildenbrand <david@...hat.com>
To:     Deming Wang <wangdeming@...pur.com>, akpm@...ux-foundation.org,
        shuah@...nel.org
Cc:     linux-mm@...ck.org, linux-kselftest@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] selftests/mm: Replace obsolete memalign() with
 posix_memalign()

On 12.04.23 09:27, Deming Wang wrote:
> memalign() is obsolete according to its manpage.
> 
> Replace memalign() with posix_memalign() and remove malloc.h include
> that was there for memalign().
> 
> As a pointer is passed into posix_memalign(), initialize *p to NULL
> to silence a warning about the function's return value being used as
> uninitialized (which is not valid anyway because the error is properly
> checked before p is returned).

I don't follow how that comment here applies to the patch. What is p? 
Where is it initialized to NULL?

> 
> Signed-off-by: Deming Wang <wangdeming@...pur.com>
> ---
>   tools/testing/selftests/mm/soft-dirty.c | 4 ++--
>   1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/tools/testing/selftests/mm/soft-dirty.c b/tools/testing/selftests/mm/soft-dirty.c
> index 21d8830c5f24..4bb7421141a2 100644
> --- a/tools/testing/selftests/mm/soft-dirty.c
> +++ b/tools/testing/selftests/mm/soft-dirty.c
> @@ -80,8 +80,8 @@ static void test_hugepage(int pagemap_fd, int pagesize)
>   	int i, ret;
>   	size_t hpage_len = read_pmd_pagesize();
>   
> -	map = memalign(hpage_len, hpage_len);
> -	if (!map)
> +	ret = posix_memalign((void *)(&map), hpage_len, hpage_len);

posix_memalign expects an "void **memptr", casting to "void *" looks 
weird. Further, you can drop the parentheses around &map.

ret = posix_memalign((void **)&map, hpage_len, hpage_len);


> +	if (ret < 0)
>   		ksft_exit_fail_msg("memalign failed\n");

Better adjust the comment to "posix_memalign() failed\n"

-- 
Thanks,

David / dhildenb