[PATCH v4 20/23] mm/gup_benchmark: use proper FOLL_WRITE flags instead of hard-coding "1"

[John Hubbard]

Fix the gup benchmark flags to use the symbolic FOLL_WRITE,
instead of a hard-coded "1" value.

Also, clean up the filtering of gup flags a little, by just doing
it once before issuing any of the get_user_pages*() calls. This
makes it harder to overlook, instead of having little "gup_flags & 1"
phrases in the function calls.

Signed-off-by: John Hubbard <jhubbard@xxxxxxxxxx>
---
 mm/gup_benchmark.c                         | 9 ++++++---
 tools/testing/selftests/vm/gup_benchmark.c | 6 +++++-
 2 files changed, 11 insertions(+), 4 deletions(-)

diff --git a/mm/gup_benchmark.c b/mm/gup_benchmark.c
index 7dd602d7f8db..7fc44d25eca7 100644
--- a/mm/gup_benchmark.c
+++ b/mm/gup_benchmark.c
@@ -48,18 +48,21 @@ static int __gup_benchmark_ioctl(unsigned int cmd,
 			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 & 1,
+			nr = get_user_pages_fast(addr, nr, gup->flags,
 						 pages + i);
 			break;
 		case GUP_LONGTERM_BENCHMARK:
 			nr = get_user_pages(addr, nr,
-					    (gup->flags & 1) | FOLL_LONGTERM,
+					    gup->flags | FOLL_LONGTERM,
 					    pages + i, NULL);
 			break;
 		case GUP_BENCHMARK:
-			nr = get_user_pages(addr, nr, gup->flags & 1, pages + i,
+			nr = get_user_pages(addr, nr, gup->flags, pages + i,
 					    NULL);
 			break;
 		default:
diff --git a/tools/testing/selftests/vm/gup_benchmark.c b/tools/testing/selftests/vm/gup_benchmark.c
index 485cf06ef013..389327e9b30a 100644
--- a/tools/testing/selftests/vm/gup_benchmark.c
+++ b/tools/testing/selftests/vm/gup_benchmark.c
@@ -18,6 +18,9 @@
 #define GUP_LONGTERM_BENCHMARK	_IOWR('g', 2, struct gup_benchmark)
 #define GUP_BENCHMARK		_IOWR('g', 3, struct gup_benchmark)
 
+/* Just the flags we need, copied from mm.h: */
+#define FOLL_WRITE	0x01	/* check pte is writable */
+
 struct gup_benchmark {
 	__u64 get_delta_usec;
 	__u64 put_delta_usec;
@@ -85,7 +88,8 @@ int main(int argc, char **argv)
 	}
 
 	gup.nr_pages_per_call = nr_pages;
-	gup.flags = write;
+	if (write)
+		gup.flags |= FOLL_WRITE;
 
 	fd = open("/sys/kernel/debug/gup_benchmark", O_RDWR);
 	if (fd == -1)
-- 
2.24.0