selftests/vm: gup_test: fix test flag

In gup_test both gup_flags and test_flags use the same flags field.
This is broken.

Farther, in the actual gup_test.c all the passed gup_flags are erased
and unconditionally replaced with FOLL_WRITE.

Which means that test_flags are ignored, and code like this always
performs pin dump test:

155 if (gup->flags & GUP_TEST_FLAG_DUMP_PAGES_USE_PIN)
156 nr = pin_user_pages(addr, nr, gup->flags,
157 pages + i, NULL);
158 else
159 nr = get_user_pages(addr, nr, gup->flags,
160 pages + i, NULL);
161 break;

Add a new test_flags field, to allow raw gup_flags to work. Add a new
subcommand for DUMP_USER_PAGES_TEST to specify that pin test should be
performed.

Remove unconditional overwriting of gup_flags via FOLL_WRITE. But,
preserve the previous behaviour where FOLL_WRITE was the default flag,
and add a new option "-W" to unset FOLL_WRITE.

Rename flags with gup_flags.

With the fix, dump works like this:

root@virtme:/# gup_test -c
---- page #0, starting from user virt addr: 0x7f8acb9e4000
page:00000000d3d2ee27 refcount:2 mapcount:1 mapping:0000000000000000
index:0x0 pfn:0x100bcf
anon flags: 0x300000000080016(referenced|uptodate|lru|swapbacked)
raw: 0300000000080016 ffffd0e204021608 ffffd0e208df2e88 ffff8ea04243ec61
raw: 0000000000000000 0000000000000000 0000000200000000 0000000000000000
page dumped because: gup_test: dump_pages() test
DUMP_USER_PAGES_TEST: done

root@virtme:/# gup_test -c -p
---- page #0, starting from user virt addr: 0x7fd19701b000
page:00000000baed3c7d refcount:1025 mapcount:1 mapping:0000000000000000
index:0x0 pfn:0x108008
anon flags: 0x300000000080014(uptodate|lru|swapbacked)
raw: 0300000000080014 ffffd0e204200188 ffffd0e205e09088 ffff8ea04243ee71
raw: 0000000000000000 0000000000000000 0000040100000000 0000000000000000
page dumped because: gup_test: dump_pages() test
DUMP_USER_PAGES_TEST: done

Refcount shows the difference between pin vs no-pin case.
Also change type of nr from int to long, as it counts number of pages.

Link: https://lkml.kernel.org/r/[e-mail]
Signed-off-by: Pavel Tatashin <[e-mail]>
Reviewed-by: John Hubbard <[e-mail]>
Cc: Dan Williams <[e-mail]>
Cc: David Hildenbrand <[e-mail]>
Cc: David Rientjes <[e-mail]>
Cc: Ingo Molnar <[e-mail]>
Cc: Ira Weiny <[e-mail]>
Cc: James Morris <[e-mail]>
Cc: Jason Gunthorpe <[e-mail]>
Cc: Jason Gunthorpe <[e-mail]>
Cc: Joonsoo Kim <[e-mail]>
Cc: Matthew Wilcox <[e-mail]>
Cc: Mel Gorman <[e-mail]>
Cc: Michal Hocko <[e-mail]>
Cc: Michal Hocko <[e-mail]>
Cc: Mike Kravetz <[e-mail]>
Cc: Oscar Salvador <[e-mail]>
Cc: Peter Zijlstra <[e-mail]>
Cc: Sasha Levin <[e-mail]>
Cc: Steven Rostedt (VMware) <[e-mail]>
Cc: Tyler Hicks <[e-mail]>
Cc: Vlastimil Babka <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

mm/gup_test.c

···
 {
 	ktime_t start_time, end_time;
 	unsigned long i, nr_pages, addr, next;
-	int nr;
+	long nr;
 	struct page **pages;
 	int ret = 0;
 	bool needs_mmap_lock =
···
 			nr = (next - addr) / PAGE_SIZE;
 		}
 
-		/* Filter out most gup flags: only allow a tiny subset here: */
-		gup->flags &= FOLL_WRITE;
-
 		switch (cmd) {
 		case GUP_FAST_BENCHMARK:
-			nr = get_user_pages_fast(addr, nr, gup->flags,
+			nr = get_user_pages_fast(addr, nr, gup->gup_flags,
 						 pages + i);
 			break;
 		case GUP_BASIC_TEST:
-			nr = get_user_pages(addr, nr, gup->flags, pages + i,
+			nr = get_user_pages(addr, nr, gup->gup_flags, pages + i,
 					    NULL);
 			break;
 		case PIN_FAST_BENCHMARK:
-			nr = pin_user_pages_fast(addr, nr, gup->flags,
+			nr = pin_user_pages_fast(addr, nr, gup->gup_flags,
 						 pages + i);
 			break;
 		case PIN_BASIC_TEST:
-			nr = pin_user_pages(addr, nr, gup->flags, pages + i,
+			nr = pin_user_pages(addr, nr, gup->gup_flags, pages + i,
 					    NULL);
 			break;
 		case PIN_LONGTERM_BENCHMARK:
 			nr = pin_user_pages(addr, nr,
-					    gup->flags | FOLL_LONGTERM,
+					    gup->gup_flags | FOLL_LONGTERM,
 					    pages + i, NULL);
 			break;
 		case DUMP_USER_PAGES_TEST:
-			if (gup->flags & GUP_TEST_FLAG_DUMP_PAGES_USE_PIN)
-				nr = pin_user_pages(addr, nr, gup->flags,
+			if (gup->test_flags & GUP_TEST_FLAG_DUMP_PAGES_USE_PIN)
+				nr = pin_user_pages(addr, nr, gup->gup_flags,
 						    pages + i, NULL);
 			else
-				nr = get_user_pages(addr, nr, gup->flags,
+				nr = get_user_pages(addr, nr, gup->gup_flags,
 						    pages + i, NULL);
 			break;
 		default:
···
 
 	start_time = ktime_get();
 
-	put_back_pages(cmd, pages, nr_pages, gup->flags);
+	put_back_pages(cmd, pages, nr_pages, gup->test_flags);
 
 	end_time = ktime_get();
 	gup->put_delta_usec = ktime_us_delta(end_time, start_time);

mm/gup_test.h

···
 	__u64 addr;
 	__u64 size;
 	__u32 nr_pages_per_call;
-	__u32 flags;
+	__u32 gup_flags;
+	__u32 test_flags;
 	/*
 	 * Each non-zero entry is the number of the page (1-based: first page is
 	 * page 1, so that zero entries mean "do nothing") from the .addr base.

tools/testing/selftests/vm/gup_test.c

···
 {
 	struct gup_test gup = { 0 };
 	unsigned long size = 128 * MB;
-	int i, fd, filed, opt, nr_pages = 1, thp = -1, repeats = 1, write = 0;
+	int i, fd, filed, opt, nr_pages = 1, thp = -1, repeats = 1, write = 1;
 	unsigned long cmd = GUP_FAST_BENCHMARK;
 	int flags = MAP_PRIVATE;
 	char *file = "/dev/zero";
 	char *p;
 
-	while ((opt = getopt(argc, argv, "m:r:n:F:f:abctTLUuwSH")) != -1) {
+	while ((opt = getopt(argc, argv, "m:r:n:F:f:abctTLUuwWSHp")) != -1) {
 		switch (opt) {
 		case 'a':
 			cmd = PIN_FAST_BENCHMARK;
···
 			 */
 			gup.which_pages[0] = 1;
 			break;
+		case 'p':
+			/* works only with DUMP_USER_PAGES_TEST */
+			gup.test_flags |= GUP_TEST_FLAG_DUMP_PAGES_USE_PIN;
+			break;
 		case 'F':
 			/* strtol, so you can pass flags in hex form */
-			gup.flags = strtol(optarg, 0, 0);
+			gup.gup_flags = strtol(optarg, 0, 0);
 			break;
 		case 'm':
 			size = atoi(optarg) * MB;
···
 			break;
 		case 'w':
 			write = 1;
+			break;
+		case 'W':
+			write = 0;
 			break;
 		case 'f':
 			file = optarg;
···
 
 	gup.nr_pages_per_call = nr_pages;
 	if (write)
-		gup.flags |= FOLL_WRITE;
+		gup.gup_flags |= FOLL_WRITE;
 
 	fd = open("/sys/kernel/debug/gup_test", O_RDWR);
 	if (fd == -1) {