userfaultfd/selftests: dropping VERIFY check in locking_thread

It tries to check against all zeros and looped for quite a few times.
However after that we'll verify the same page with count_verify, while
count_verify can never be zero.  So it means if it's a zero page we'll
detect it anyways with below code.

There's yet another place we conditionally check the fault flag - just do
it unconditionally.

Link: https://lkml.kernel.org/r/20210412232753.1012412-4-peterx@redhat.com
Signed-off-by: Peter Xu <peterx@redhat.com>
Reviewed-by: Axel Rasmussen <axelrasmussen@google.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Brian Geffon <bgeffon@google.com>
Cc: "Dr . David Alan Gilbert" <dgilbert@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jerome Glisse <jglisse@redhat.com>
Cc: Joe Perches <joe@perches.com>
Cc: Kirill A. Shutemov <kirill@shutemov.name>
Cc: Lokesh Gidra <lokeshgidra@google.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Mike Rapoport <rppt@linux.vnet.ibm.com>
Cc: Mina Almasry <almasrymina@google.com>
Cc: Oliver Upton <oupton@google.com>
Cc: Shaohua Li <shli@fb.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Cc: Wang Qing <wangqing@vivo.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/tools/testing/selftests/vm/userfaultfd.c b/tools/testing/selftests/vm/userfaultfd.c
index 5cae66e..387b936 100644 (file)
--- a/tools/testing/selftests/vm/userfaultfd.c
+++ b/tools/testing/selftests/vm/userfaultfd.c
@@ -430,58 +430,6 @@ static void *locking_thread(void *arg)
                } else
                        page_nr += 1;
                page_nr %= nr_pages;
-
-               if (bounces & BOUNCE_VERIFY) {
-                       count = *area_count(area_dst, page_nr);
-                       if (!count) {
-                               fprintf(stderr,
-                                       "page_nr %lu wrong count %Lu %Lu\n",
-                                       page_nr, count,
-                                       count_verify[page_nr]);
-                               exit(1);
-                       }
-
-
-                       /*
-                        * We can't use bcmp (or memcmp) because that
-                        * returns 0 erroneously if the memory is
-                        * changing under it (even if the end of the
-                        * page is never changing and always
-                        * different).
-                        */
-#if 1
-                       if (!my_bcmp(area_dst + page_nr * page_size, zeropage,
-                                    page_size)) {
-                               fprintf(stderr,
-                                       "my_bcmp page_nr %lu wrong count %Lu %Lu\n",
-                                       page_nr, count, count_verify[page_nr]);
-                               exit(1);
-                       }
-#else
-                       unsigned long loops;
-
-                       loops = 0;
-                       /* uncomment the below line to test with mutex */
-                       /* pthread_mutex_lock(area_mutex(area_dst, page_nr)); */
-                       while (!bcmp(area_dst + page_nr * page_size, zeropage,
-                                    page_size)) {
-                               loops += 1;
-                               if (loops > 10)
-                                       break;
-                       }
-                       /* uncomment below line to test with mutex */
-                       /* pthread_mutex_unlock(area_mutex(area_dst, page_nr)); */
-                       if (loops) {
-                               fprintf(stderr,
-                                       "page_nr %lu all zero thread %lu %p %lu\n",
-                                       page_nr, cpu, area_dst + page_nr * page_size,
-                                       loops);
-                               if (loops > 10)
-                                       exit(1);
-                       }
-#endif
-               }
-
                pthread_mutex_lock(area_mutex(area_dst, page_nr));
                count = *area_count(area_dst, page_nr);
                if (count != count_verify[page_nr]) {
@@ -613,8 +561,7 @@ static void uffd_handle_page_fault(struct uffd_msg *msg,
                stats->minor_faults++;
        } else {
                /* Missing page faults */
-               if (bounces & BOUNCE_VERIFY &&
-                   msg->arg.pagefault.flags & UFFD_PAGEFAULT_FLAG_WRITE) {
+               if (msg->arg.pagefault.flags & UFFD_PAGEFAULT_FLAG_WRITE) {
                        fprintf(stderr, "unexpected write fault\n");
                        exit(1);
                }