selftests/mm: call uffd_test_ctx_clear at the end of the test

uffd_test_ctx_clear() is being called from uffd_test_ctx_init() to unmap
areas used in the previous test run.  This approach is problematic because
while unmapping areas uffd_test_ctx_clear() uses page_size and nr_pages
which might differ from one test run to another.  Fix this by calling
uffd_test_ctx_clear() after each test is done.

Link: https://lkml.kernel.org/r/20231206103702.3873743-4-surenb@google.com
Signed-off-by: Suren Baghdasaryan <surenb@google.com>
Reviewed-by: Peter Xu <peterx@redhat.com>
Reviewed-by: Axel Rasmussen <axelrasmussen@google.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Brian Geffon <bgeffon@google.com>
Cc: Christian Brauner <brauner@kernel.org>
Cc: David Hildenbrand <david@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jann Horn <jannh@google.com>
Cc: Kalesh Singh <kaleshsingh@google.com>
Cc: Liam R. Howlett <Liam.Howlett@oracle.com>
Cc: Lokesh Gidra <lokeshgidra@google.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport (IBM) <rppt@kernel.org>
Cc: Nicolas Geoffray <ngeoffray@google.com>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: ZhangPeng <zhangpeng362@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

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

@@ -262,7 +262,7 @@ static inline void munmap_area(void **area)
 	*area = NULL;
 }
 
-static void uffd_test_ctx_clear(void)
+void uffd_test_ctx_clear(void)
 {
 	size_t i;
 
@@ -298,8 +298,6 @@ int uffd_test_ctx_init(uint64_t features, const char **errmsg)
 	unsigned long nr, cpu;
 	int ret;
 
-	uffd_test_ctx_clear();
-
 	ret = uffd_test_ops->allocate_area((void **)&area_src, true);
 	ret |= uffd_test_ops->allocate_area((void **)&area_dst, false);
 	if (ret) {

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

@@ -105,6 +105,7 @@ extern uffd_test_ops_t *uffd_test_ops;
 
 void uffd_stats_report(struct uffd_args *args, int n_cpus);
 int uffd_test_ctx_init(uint64_t features, const char **errmsg);
+void uffd_test_ctx_clear(void);
 int userfaultfd_open(uint64_t *features);
 int uffd_read_msg(int ufd, struct uffd_msg *msg);
 void wp_range(int ufd, __u64 start, __u64 len, bool wp);

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

@@ -323,8 +323,10 @@ static int userfaultfd_stress(void)
 		uffd_stats_reset(args, nr_cpus);
 
 		/* bounce pass */
-		if (stress(args))
+		if (stress(args)) {
+			uffd_test_ctx_clear();
 			return 1;
+		}
 
 		/* Clear all the write protections if there is any */
 		if (test_uffdio_wp)
@@ -354,6 +356,7 @@ static int userfaultfd_stress(void)
 
 		uffd_stats_report(args, nr_cpus);
 	}
+	uffd_test_ctx_clear();
 
 	return 0;
 }

tools/testing/selftests/mm/uffd-unit-tests.c

@@ -1319,6 +1319,7 @@ int main(int argc, char *argv[])
 				continue;
 			}
 			test->uffd_fn(&args);
+			uffd_test_ctx_clear();
 		}
 	}