[045/192] userfaultfd/selftests: use memfd_create for shmem test type

Commit Message

Andrew Morton July 1, 2021, 1:49 a.m. UTC

From: Axel Rasmussen <[e-mail]>
Subject: userfaultfd/selftests: use memfd_create for shmem test type

This is a preparatory commit.  In the future, we want to be able to setup
alias mappings for area_src and area_dst in the shmem test, like we do in
the hugetlb_shared test.  With a VMA obtained via mmap(MAP_ANONYMOUS |
MAP_SHARED), it isn't clear how to do this.

So, mmap() with an fd, so we can create alias mappings.  Use memfd_create
instead of actually passing in a tmpfs path like hugetlb does, since it's
more convenient / simpler to run, and works just as well.

Future commits will:

1. Setup the alias mappings.
2. Extend our tests to actually take advantage of this, to test new
   userfaultfd behavior being introduced in this series.

Also, a small fix in the area we're changing: when the hugetlb setup fails
in main(), pass in the right argv[] so we actually print out the hugetlb
file path.

Link: https://lkml.kernel.org/r/[e-mail]
Signed-off-by: Axel Rasmussen <[e-mail]>
Reviewed-by: Peter Xu <[e-mail]>
Cc: Alexander Viro <[e-mail]>
Cc: Andrea Arcangeli <[e-mail]>
Cc: Brian Geffon <[e-mail]>
Cc: "Dr . David Alan Gilbert" <[e-mail]>
Cc: Hugh Dickins <[e-mail]>
Cc: Jerome Glisse <[e-mail]>
Cc: Joe Perches <[e-mail]>
Cc: Kirill A. Shutemov <[e-mail]>
Cc: Lokesh Gidra <[e-mail]>
Cc: Mike Kravetz <[e-mail]>
Cc: Mike Rapoport <[e-mail]>
Cc: Mina Almasry <[e-mail]>
Cc: Oliver Upton <[e-mail]>
Cc: Shaohua Li <[e-mail]>
Cc: Shuah Khan <[e-mail]>
Cc: Stephen Rothwell <[e-mail]>
Cc: Wang Qing <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
---

 tools/testing/selftests/vm/userfaultfd.c |   16 +++++++++++++++-
 1 file changed, 15 insertions(+), 1 deletion(-)

Patch

--- a/tools/testing/selftests/vm/userfaultfd.c~userfaultfd-selftests-use-memfd_create-for-shmem-test-type
+++ a/tools/testing/selftests/vm/userfaultfd.c
@@ -85,6 +85,7 @@  static bool test_uffdio_wp = false;
 static bool test_uffdio_minor = false;
 
 static bool map_shared;
+static int shm_fd;
 static int huge_fd;
 static char *huge_fd_off0;
 static unsigned long long *count_verify;
@@ -277,8 +278,11 @@  static void shmem_release_pages(char *re
 
 static void shmem_allocate_area(void **alloc_area)
 {
+	unsigned long offset =
+		alloc_area == (void **)&area_src ? 0 : nr_pages * page_size;
+
 	*alloc_area = mmap(NULL, nr_pages * page_size, PROT_READ | PROT_WRITE,
-			   MAP_ANONYMOUS | MAP_SHARED, -1, 0);
+			   MAP_SHARED, shm_fd, offset);
 	if (*alloc_area == MAP_FAILED)
 		err("mmap of memfd failed");
 }
@@ -1602,6 +1606,16 @@  int main(int argc, char **argv)
 			err("Open of %s failed", argv[4]);
 		if (ftruncate(huge_fd, 0))
 			err("ftruncate %s to size 0 failed", argv[4]);
+	} else if (test_type == TEST_SHMEM) {
+		shm_fd = memfd_create(argv[0], 0);
+		if (shm_fd < 0)
+			err("memfd_create");
+		if (ftruncate(shm_fd, nr_pages * page_size * 2))
+			err("ftruncate");
+		if (fallocate(shm_fd,
+			      FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE, 0,
+			      nr_pages * page_size * 2))
+			err("fallocate");
 	}
 	printf("nr_pages: %lu, nr_pages_per_cpu: %lu\n",
 	       nr_pages, nr_pages_per_cpu);