linux-kernel - Re: [PATCH] selftests/mm/cow: Fix the incorrect error handling

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Message-ID: <4a068856-328f-48ae-9b1c-0ec7d65dde6b@redhat.com>
Date: Tue, 11 Mar 2025 10:19:32 +0100
From: David Hildenbrand <david@...hat.com>
To: Cyan Yang <cyan.yang@...ive.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/cow: Fix the incorrect error handling

On 11.03.25 03:37, Cyan Yang wrote:
> There are two error handlings did not check the correct return value.
> This patch will fix them.
> 
> Fixes: f4b5fd6946e244cdedc3bbb9a1f24c8133b2077a ("selftests/vm: anon_cow: THP tests")
> Signed-off-by: Cyan Yang <cyan.yang@...ive.com>
> ---
>   tools/testing/selftests/mm/cow.c | 4 ++--
>   1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/tools/testing/selftests/mm/cow.c b/tools/testing/selftests/mm/cow.c
> index 9446673645eb..16fcadc090a4 100644
> --- a/tools/testing/selftests/mm/cow.c
> +++ b/tools/testing/selftests/mm/cow.c
> @@ -876,13 +876,13 @@ static void do_run_with_thp(test_fn fn, enum thp_run thp_run, size_t thpsize)
>   		mremap_size = thpsize / 2;
>   		mremap_mem = mmap(NULL, mremap_size, PROT_NONE,
>   				  MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
> -		if (mem == MAP_FAILED) {
> +		if (mremap_mem == MAP_FAILED) {
>   			ksft_test_result_fail("mmap() failed\n");
>   			goto munmap;
>   		}

Yes, that check is wrong.

>   		tmp = mremap(mem + mremap_size, mremap_size, mremap_size,
>   			     MREMAP_MAYMOVE | MREMAP_FIXED, mremap_mem);
> -		if (tmp != mremap_mem) {
> +		if (tmp == MAP_FAILED) {
>   			ksft_test_result_fail("mremap() failed\n");
>   			goto munmap;
>   		}

As Dev says, this one is just fine. Leave it as it is.

-- 
Cheers,

David / dhildenb