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

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@redhat.com