[044/118] mm/gup_benchmark: use proper FOLL_WRITE flags instead of hard-coding "1"

Commit Message

Andrew Morton Jan. 31, 2020, 6:13 a.m. UTC

From: John Hubbard <[e-mail]>
Subject: mm/gup_benchmark: use proper FOLL_WRITE flags instead of hard-coding "1"

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.

Link: http://lkml.kernel.org/r/[e-mail]
Signed-off-by: John Hubbard <[e-mail]>
Reviewed-by: Ira Weiny <[e-mail]>
Cc: Alex Williamson <[e-mail]>
Cc: Aneesh Kumar K.V <[e-mail]>
Cc: Björn Töpel <[e-mail]>
Cc: Christoph Hellwig <[e-mail]>
Cc: Daniel Vetter <[e-mail]>
Cc: Dan Williams <[e-mail]>
Cc: Hans Verkuil <[e-mail]>
Cc: Jan Kara <[e-mail]>
Cc: Jason Gunthorpe <[e-mail]>
Cc: Jason Gunthorpe <[e-mail]>
Cc: Jens Axboe <[e-mail]>
Cc: Jerome Glisse <[e-mail]>
Cc: Jonathan Corbet <[e-mail]>
Cc: Kirill A. Shutemov <[e-mail]>
Cc: Leon Romanovsky <[e-mail]>
Cc: Mauro Carvalho Chehab <[e-mail]>
Cc: Mike Rapoport <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
---

 mm/gup_benchmark.c                         |    9 ++++++---
 tools/testing/selftests/vm/gup_benchmark.c |    6 +++++-
 2 files changed, 11 insertions(+), 4 deletions(-)

Patch

--- a/mm/gup_benchmark.c~mm-gup_benchmark-use-proper-foll_write-flags-instead-of-hard-coding-1
+++ a/mm/gup_benchmark.c
@@ -49,18 +49,21 @@  static int __gup_benchmark_ioctl(unsigne
 			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:
--- a/tools/testing/selftests/vm/gup_benchmark.c~mm-gup_benchmark-use-proper-foll_write-flags-instead-of-hard-coding-1
+++ a/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)