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 <jhubb...@nvidia.com>
---
 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

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