shm_open
static void shm_open(struct vm_area_struct *vma);
.open = shm_open, /* callback for a new vm-area open */
fd = shm_open("/tmp_shmem", O_CREAT | O_RDWR, 0644);
fd = shm_open(filename, O_CREAT | O_RDWR, 0600);
shm_fd = shm_open(data->filename, O_CREAT | O_RDWR, 0666);