selftest/vm: test that mremap fails on non-existent vma

Add a regression test that validates that mremap fails for vma's that
don't exist.

Link: https://lkml.kernel.org/r/20220427224439.23828-3-dossche.niels@gmail.comSigned-off-by: NNiels Dossche <dossche.niels@gmail.com>
Cc: Mina Almasry <almasrymina@google.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>

tools/testing/selftests/vm/hugepage-mremap.c

@@ -178,6 +178,12 @@ int main(int argc, char *argv[])
 
 	munmap(addr, length);
 
+	addr = mremap(addr, length, length, 0);
+	if (addr != MAP_FAILED) {
+		printf("mremap: Expected failure, but call succeeded\n");
+		exit(1);
+	}
+
 	close(fd);
 	unlink(argv[argc-1]);