Re: [PATCH 1/4] selftests/vm: Use memfd for hugetlb tests

[Axel Rasmussen <axelrasmussen@google.com>]

On Tue, Oct 4, 2022 at 2:41 PM Peter Xu <peterx@redhat.com> wrote:
>
> We already used memfd for shmem test, move it forward with hugetlb too so
> that we don't need user to specify the hugetlb file path explicitly when
> running hugetlb shared tests.
>
> Signed-off-by: Peter Xu <peterx@redhat.com>
> ---
>  tools/testing/selftests/vm/userfaultfd.c | 60 ++++++++----------------
>  1 file changed, 20 insertions(+), 40 deletions(-)
>
> diff --git a/tools/testing/selftests/vm/userfaultfd.c b/tools/testing/selftests/vm/userfaultfd.c
> index 74babdbc02e5..c0c6853cdce5 100644
> --- a/tools/testing/selftests/vm/userfaultfd.c
> +++ b/tools/testing/selftests/vm/userfaultfd.c
> @@ -93,10 +93,8 @@ static volatile bool test_uffdio_zeropage_eexist = true;
>  static bool test_uffdio_wp = true;
>  /* Whether to test uffd minor faults */
>  static bool test_uffdio_minor = false;
> -
>  static bool map_shared;
> -static int shm_fd;
> -static int huge_fd;
> +static int mem_fd;
>  static unsigned long long *count_verify;
>  static int uffd = -1;
>  static int uffd_flags, finished, *pipefd;
> @@ -260,35 +258,21 @@ static void hugetlb_release_pages(char *rel_area)
>
>  static void hugetlb_allocate_area(void **alloc_area, bool is_src)
>  {
> +       off_t size = nr_pages * page_size;
> +       off_t offset = is_src ? 0 : size;
>         void *area_alias = NULL;
>         char **alloc_area_alias;
>
> -       if (!map_shared)
> -               *alloc_area = mmap(NULL,
> -                       nr_pages * page_size,
> -                       PROT_READ | PROT_WRITE,
> -                       MAP_PRIVATE | MAP_ANONYMOUS | MAP_HUGETLB |
> -                               (is_src ? 0 : MAP_NORESERVE),
> -                       -1,
> -                       0);
> -       else
> -               *alloc_area = mmap(NULL,
> -                       nr_pages * page_size,
> -                       PROT_READ | PROT_WRITE,
> -                       MAP_SHARED |
> -                               (is_src ? 0 : MAP_NORESERVE),
> -                       huge_fd,
> -                       is_src ? 0 : nr_pages * page_size);
> +       *alloc_area = mmap(NULL, size, PROT_READ | PROT_WRITE,
> +                          (map_shared ? MAP_SHARED : MAP_PRIVATE) |
> +                          (is_src ? 0 : MAP_NORESERVE),
> +                          mem_fd, offset);
>         if (*alloc_area == MAP_FAILED)
>                 err("mmap of hugetlbfs file failed");
>
>         if (map_shared) {
> -               area_alias = mmap(NULL,
> -                       nr_pages * page_size,
> -                       PROT_READ | PROT_WRITE,
> -                       MAP_SHARED,
> -                       huge_fd,
> -                       is_src ? 0 : nr_pages * page_size);
> +               area_alias = mmap(NULL, size, PROT_READ | PROT_WRITE,
> +                                 MAP_SHARED, mem_fd, offset);
>                 if (area_alias == MAP_FAILED)
>                         err("mmap of hugetlb file alias failed");
>         }
> @@ -334,14 +318,14 @@ static void shmem_allocate_area(void **alloc_area, bool is_src)
>         }
>
>         *alloc_area = mmap(p, bytes, PROT_READ | PROT_WRITE, MAP_SHARED,
> -                          shm_fd, offset);
> +                          mem_fd, offset);
>         if (*alloc_area == MAP_FAILED)
>                 err("mmap of memfd failed");
>         if (test_collapse && *alloc_area != p)
>                 err("mmap of memfd failed at %p", p);
>
>         area_alias = mmap(p_alias, bytes, PROT_READ | PROT_WRITE, MAP_SHARED,
> -                         shm_fd, offset);
> +                         mem_fd, offset);
>         if (area_alias == MAP_FAILED)
>                 err("mmap of memfd alias failed");
>         if (test_collapse && area_alias != p_alias)
> @@ -1821,21 +1805,17 @@ int main(int argc, char **argv)
>         }
>         nr_pages = nr_pages_per_cpu * nr_cpus;
>
> -       if (test_type == TEST_HUGETLB && map_shared) {
> -               if (argc < 5)
> -                       usage();
> -               huge_fd = open(argv[4], O_CREAT | O_RDWR, 0755);
> -               if (huge_fd < 0)
> -                       err("Open of %s failed", argv[4]);
> -               if (ftruncate(huge_fd, 0))
> -                       err("ftruncate %s to size 0 failed", argv[4]);

We should also update the examples / help text near the top of the
file, since we're changing what arguments this accepts.

It might also be better to squash the changes to test arguments in
run_vmtests.sh into each patch, so if we're bisecting we'll have a
matching / working test + run_vmtests.sh combo at each commit.

> -       } else if (test_type == TEST_SHMEM) {
> -               shm_fd = memfd_create(argv[0], 0);
> -               if (shm_fd < 0)
> +       if (test_type == TEST_SHMEM || test_type == TEST_HUGETLB) {
> +               unsigned int memfd_flags = 0;
> +
> +               if (test_type == TEST_HUGETLB)
> +                       memfd_flags = MFD_HUGETLB;
> +               mem_fd = memfd_create(argv[0], memfd_flags);
> +               if (mem_fd < 0)
>                         err("memfd_create");
> -               if (ftruncate(shm_fd, nr_pages * page_size * 2))
> +               if (ftruncate(mem_fd, nr_pages * page_size * 2))
>                         err("ftruncate");
> -               if (fallocate(shm_fd,
> +               if (fallocate(mem_fd,
>                               FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE, 0,
>                               nr_pages * page_size * 2))
>                         err("fallocate");
> --
> 2.37.3
>

This is a nice simplification! Thanks for doing it. Besides the
comments above, the rest of the code here looks correct to me. Feel
free to take:

Reviewed-by: Axel Rasmussen <axelrasmussen@google.com>