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

[Dev Jain]

On 11/03/25 8:07 am, 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@xxxxxxxxxx>
> ---
>   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;
>   		}
>   		tmp = mremap(mem + mremap_size, mremap_size, mremap_size,
>   			     MREMAP_MAYMOVE | MREMAP_FIXED, mremap_mem);
> -		if (tmp != mremap_mem) {

This is fine. We are checking whether we were able to mremap tmp to 
mremap_mem.

> +		if (tmp == MAP_FAILED) {
>   			ksft_test_result_fail("mremap() failed\n");
>   			goto munmap;
>   		}