selftests/mm: gup_tests: option to GUP all pages in a single call

We recently missed detecting an issue during early testing because the
default (!all) tests would not trigger it and even when running "all"
tests it only would happen sometimes because of races.

So let's allow for an easy way to specify "GUP all pages in a single
call", extend the test matrix and extend our default (!all) tests.

By GUP'ing all pages in a single call, with the default size of 128MiB
we'll cover multiple leaf page tables / PMDs on architectures with sane
THP sizes.

Link: https://lkml.kernel.org/r/[e-mail]
Signed-off-by: David Hildenbrand <[e-mail]>
Cc: Jason Gunthorpe <[e-mail]>
Cc: John Hubbard <[e-mail]>
Cc: Peter Xu <[e-mail]>
Cc: Lorenzo Stoakes <[e-mail]>
Cc: "Liam R. Howlett" <[e-mail]>
Cc: Vlastimil Babka <[e-mail]>
Cc: Mike Rapoport <[e-mail]>
Cc: Suren Baghdasaryan <[e-mail]>
Cc: Michal Hocko <[e-mail]>
Cc: Shuah Khan <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>

tools/testing/selftests/mm/gup_test.c

···
 			break;
 		case 'n':
 			nr_pages = atoi(optarg);
+			if (nr_pages < 0)
+				nr_pages = size / psize();
 			break;
 		case 't':
 			thp = 1;

tools/testing/selftests/mm/run_vmtests.sh

···
                     # -n: How many pages to fetch together?  512 is special
                     # because it's default thp size (or 2M on x86), 123 to
                     # just test partial gup when hit a huge in whatever form
-                    for num in "-n 1" "-n 512" "-n 123"; do
+                    for num in "-n 1" "-n 512" "-n 123" "-n -1"; do
                         CATEGORY="gup_test" run_test ./gup_test \
                                 $huge $test_cmd $write $share $num
                     done
···
     run_gup_matrix
 else
     # get_user_pages_fast() benchmark
-    CATEGORY="gup_test" run_test ./gup_test -u
+    CATEGORY="gup_test" run_test ./gup_test -u -n 1
+    CATEGORY="gup_test" run_test ./gup_test -u -n -1
     # pin_user_pages_fast() benchmark
-    CATEGORY="gup_test" run_test ./gup_test -a
+    CATEGORY="gup_test" run_test ./gup_test -a -n 1
+    CATEGORY="gup_test" run_test ./gup_test -a -n -1
 fi
 # Dump pages 0, 19, and 4096, using pin_user_pages:
 CATEGORY="gup_test" run_test ./gup_test -ct -F 0x1 0 19 0x1000