selftests/mm: drop global mem_fd in uffd tests

Drop it by creating the memfd dynamically in the tests.

Link: https://lkml.kernel.org/r/20230412164331.328584-1-peterx@redhat.comSigned-off-by: Peter Xu <peterx@redhat.com>
Reviewed-by: Mike Rapoport (IBM) <rppt@kernel.org>
Cc: Axel Rasmussen <axelrasmussen@google.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Dmitry Safonov <0x7f454c46@gmail.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Zach O'Keefe <zokeefe@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

tools/testing/selftests/mm/uffd-common.c

@@ -12,12 +12,32 @@
 volatile bool test_uffdio_copy_eexist = true;
 unsigned long nr_cpus, nr_pages, nr_pages_per_cpu, page_size, hpage_size;
 char *area_src, *area_src_alias, *area_dst, *area_dst_alias, *area_remap;
-int mem_fd, uffd = -1, uffd_flags, finished, *pipefd, test_type;
+int uffd = -1, uffd_flags, finished, *pipefd, test_type;
 bool map_shared, test_collapse, test_dev_userfaultfd;
 bool test_uffdio_wp = true, test_uffdio_minor = false;
 unsigned long long *count_verify;
 uffd_test_ops_t *uffd_test_ops;
 
+static int uffd_mem_fd_create(off_t mem_size, bool hugetlb)
+{
+	unsigned int memfd_flags = 0;
+	int mem_fd;
+
+	if (hugetlb)
+		memfd_flags = MFD_HUGETLB;
+	mem_fd = memfd_create("uffd-test", memfd_flags);
+	if (mem_fd < 0)
+		err("memfd_create");
+	if (ftruncate(mem_fd, mem_size))
+		err("ftruncate");
+	if (fallocate(mem_fd,
+		      FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE, 0,
+		      mem_size))
+		err("fallocate");
+
+	return mem_fd;
+}
+
 static void anon_release_pages(char *rel_area)
 {
 	if (madvise(rel_area, nr_pages * page_size, MADV_DONTNEED))
@@ -51,6 +71,7 @@ static void hugetlb_allocate_area(void **alloc_area, bool is_src)
 	off_t offset = is_src ? 0 : size;
 	void *area_alias = NULL;
 	char **alloc_area_alias;
+	int mem_fd = uffd_mem_fd_create(size * 2, true);
 
 	*alloc_area = mmap(NULL, size, PROT_READ | PROT_WRITE,
 			   (map_shared ? MAP_SHARED : MAP_PRIVATE) |
@@ -73,6 +94,8 @@ static void hugetlb_allocate_area(void **alloc_area, bool is_src)
 	}
 	if (area_alias)
 		*alloc_area_alias = area_alias;
+
+	close(mem_fd);
 }
 
 static void hugetlb_alias_mapping(__u64 *start, size_t len, unsigned long offset)
@@ -95,6 +118,7 @@ static void shmem_allocate_area(void **alloc_area, bool is_src)
 	size_t bytes = nr_pages * page_size;
 	unsigned long offset = is_src ? 0 : bytes;
 	char *p = NULL, *p_alias = NULL;
+	int mem_fd = uffd_mem_fd_create(bytes * 2, false);
 
 	if (test_collapse) {
 		p = BASE_PMD_ADDR;
@@ -124,6 +148,8 @@ static void shmem_allocate_area(void **alloc_area, bool is_src)
 		area_src_alias = area_alias;
 	else
 		area_dst_alias = area_alias;
+
+	close(mem_fd);
 }
 
 static void shmem_alias_mapping(__u64 *start, size_t len, unsigned long offset)

tools/testing/selftests/mm/uffd-common.h

@@ -87,7 +87,7 @@ typedef struct uffd_test_ops uffd_test_ops_t;
 
 extern unsigned long nr_cpus, nr_pages, nr_pages_per_cpu, page_size, hpage_size;
 extern char *area_src, *area_src_alias, *area_dst, *area_dst_alias, *area_remap;
-extern int mem_fd, uffd, uffd_flags, finished, *pipefd, test_type;
+extern int uffd, uffd_flags, finished, *pipefd, test_type;
 extern bool map_shared, test_collapse, test_dev_userfaultfd;
 extern bool test_uffdio_wp, test_uffdio_minor;
 extern unsigned long long *count_verify;

tools/testing/selftests/mm/uffd-stress.c

@@ -1090,21 +1090,6 @@ int main(int argc, char **argv)
 	}
 	nr_pages = nr_pages_per_cpu * nr_cpus;
 
-	if (test_type == TEST_SHMEM || test_type == TEST_HUGETLB) {
-		unsigned int memfd_flags = 0;
-
-		if (test_type == TEST_HUGETLB)
-			memfd_flags = MFD_HUGETLB;
-		mem_fd = memfd_create(argv[0], memfd_flags);
-		if (mem_fd < 0)
-			err("memfd_create");
-		if (ftruncate(mem_fd, nr_pages * page_size * 2))
-			err("ftruncate");
-		if (fallocate(mem_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);
 	return userfaultfd_stress();