selftests/futex: Set the home_node in futex_numa_mpol

The test fails at the MPOL step if multiple nodes are available. The
reason is that mbind() sets the policy but the home_node, which is
retrieved by the futex code, is not set. This causes to retrieve the
current node and with multiple nodes it fails on one of the iterations.

Use numa_set_mempolicy_home_node() to set the expected node.
Use ksft_exit_fail_msg() to fail and exit in order not to confuse ktap.

Fixes: 3163369 ("selftests/futex: Add futex_numa_mpol")
Suggested-by: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20250528085521.1938355-3-bigeasy@linutronix.de

Author: Sebastian Andrzej Siewior

tools/testing/selftests/futex/functional/futex_numa_mpol.c

@@ -210,6 +210,10 @@ int main(int argc, char *argv[])
 		ret = mbind(futex_ptr, mem_size, MPOL_BIND, &nodemask,
 			    sizeof(nodemask) * 8, 0);
 		if (ret == 0) {
+			ret = numa_set_mempolicy_home_node(futex_ptr, mem_size, i, 0);
+			if (ret != 0)
+				ksft_exit_fail_msg("Failed to set home node: %m, %d\n", errno);
+
 			ksft_print_msg("Node %d test\n", i);
 			futex_numa->futex = 0;
 			futex_numa->numa = FUTEX_NO_NODE;
@@ -220,8 +224,8 @@ int main(int argc, char *argv[])
 			if (0)
 				test_futex_mpol(futex_numa, 0);
 			if (futex_numa->numa != i) {
-				ksft_test_result_fail("Returned NUMA node is %d expected %d\n",
-						      futex_numa->numa, i);
+				ksft_exit_fail_msg("Returned NUMA node is %d expected %d\n",
+						   futex_numa->numa, i);
 			}
 		}
 	}