Re: [PATCH v2 6/9] userfaultfd/selftests: create alias mappings in the shmem test

[Peter Xu]

On Mon, Apr 12, 2021 at 10:17:18PM -0700, Axel Rasmussen wrote:
>  static void shmem_allocate_area(void **alloc_area)
>  {
> -	unsigned long offset =
> -		alloc_area == (void **)&area_src ? 0 : nr_pages * page_size;
> +	void *area_alias = NULL;
> +	bool is_src = alloc_area == (void **)&area_src;
> +	unsigned long offset = is_src ? 0 : nr_pages * page_size;
>  
>  	*alloc_area = mmap(NULL, nr_pages * page_size, PROT_READ | PROT_WRITE,
>  			   MAP_SHARED, shm_fd, offset);
>  	if (*alloc_area == MAP_FAILED)
>  		err("mmap of memfd failed");
> +
> +	area_alias = mmap(NULL, nr_pages * page_size, PROT_READ | PROT_WRITE,
> +			  MAP_SHARED, shm_fd, offset);
> +	if (area_alias == MAP_FAILED)
> +		err("mmap of memfd alias failed");
> +
> +	if (is_src)
> +		area_src_alias = area_alias;
> +	else
> +		area_dst_alias = area_alias;
> +}

It would be nice if shmem_allocate_area() could merge with
hugetlb_allocate_area() somehow, but not that urgent.

Reviewed-by: Peter Xu <peterx@xxxxxxxxxx>

-- 
Peter Xu