Re: [PATCH] selftests/mm: Fix mmap() return value check in run_migration_benchmark

[Mike Rapoport <rppt@kernel.org>]

On Tue, May 12, 2026 at 06:13:05PM +0800, Hongfu Li wrote:
> mmap() returns MAP_FAILED on error, not NULL.  The current check uses
> !buffer->ptr, which evaluates to false when mmap() fails (since
> MAP_FAILED is (void *)-1, not 0), so the error path is never taken.
> 
> Signed-off-by: Hongfu Li <lihongfu@kylinos.cn>

Acked-by: Mike Rapoport (Microsoft) <rppt@kernel.org>

> ---
>  tools/testing/selftests/mm/hmm-tests.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/tools/testing/selftests/mm/hmm-tests.c b/tools/testing/selftests/mm/hmm-tests.c
> index 788689497e92..d72adba5c74e 100644
> --- a/tools/testing/selftests/mm/hmm-tests.c
> +++ b/tools/testing/selftests/mm/hmm-tests.c
> @@ -2688,7 +2688,7 @@ static inline int run_migration_benchmark(int fd, int use_thp, size_t buffer_siz
>  	buffer->ptr = mmap(NULL, buffer_size, PROT_READ | PROT_WRITE,
>  			  MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
>  
> -	if (!buffer->ptr)
> +	if (buffer->ptr == MAP_FAILED)
>  		return -1;
>  
>  	/* Apply THP hint if requested */
> -- 
> 2.25.1
> 

-- 
Sincerely yours,
Mike.