Re: [PATCH v3] selftests/mm: khugepaged: initialize file contents via mmap

[David Hildenbrand (Arm)]

On 4/28/26 12:00, Vineet Agarwal wrote:
> file_setup_area() currently allocates anonymous memory, fills it,
> and writes it into the backing file used for collapse testing.
> 
> Instead of copying data through write(), resize the file with
> ftruncate(), map it directly with MAP_SHARED, and initialize the
> mapped area in place.
> 
> This simplifies the setup path and avoids the need for explicit
> partial write handling.


Please

a) Wait a bit longer before you resend.

b) Don't send as reply to earlier revisions.

> 
> Signed-off-by: Vineet Agarwal <agarwal.vineet2006@xxxxxxxxx>
> ---
>  tools/testing/selftests/mm/khugepaged.c | 17 +++++++++++++----
>  1 file changed, 13 insertions(+), 4 deletions(-)
> 
> diff --git a/tools/testing/selftests/mm/khugepaged.c b/tools/testing/selftests/mm/khugepaged.c
> index 3fe7ef04ac62..57ca4224bd5a 100644
> --- a/tools/testing/selftests/mm/khugepaged.c
> +++ b/tools/testing/selftests/mm/khugepaged.c
> @@ -369,7 +369,6 @@ static void *file_setup_area(int nr_hpages)
>  	int fd;
>  	void *p;
>  	unsigned long size;
> -

Unrelated change.

>  	unlink(finfo.path);  /* Cleanup from previous failed tests */
>  	printf("Creating %s for collapse%s...", finfo.path,
>  	       finfo.type == VMA_SHMEM ? " (tmpfs)" : "");
> @@ -381,11 +380,21 @@ static void *file_setup_area(int nr_hpages)
>  	}
>  
>  	size = nr_hpages * hpage_pmd_size;
> -	p = alloc_mapping(nr_hpages);
> +	if (ftruncate(fd, size)) {
> +		perror("ftruncate()");
> +		close(fd);
> +		exit(EXIT_FAILURE);
> +	}
> +	p = mmap(BASE_ADDR, size, PROT_READ | PROT_WRITE,
> +		MAP_SHARED, fd, 0);
> +	if (p == MAP_FAILED || p != BASE_ADDR) {
> +		perror("mmap()");
> +		close(fd);
> +		exit(EXIT_FAILURE);
> +	}
>  	fill_memory(p, 0, size);
> -	write(fd, p, size);
> -	close(fd);
>  	munmap(p, size);
> +	close(fd);

That change is not strictly required. We can munmap() after close().

Apart from that LGTM.

-- 
Cheers,

David