mm/mempolicy: add nodes_empty check in SYSC_migrate_pages

As in manpage of migrate_pages, the errno should be set to EINVAL when
none of the node IDs specified by new_nodes are on-line and allowed by
the process's current cpuset context, or none of the specified nodes
contain memory.  However, when test by following case:

	new_nodes = 0;
	old_nodes = 0xf;
	ret = migrate_pages(pid, old_nodes, new_nodes, MAX);

The ret will be 0 and no errno is set.  As the new_nodes is empty, we
should expect EINVAL as documented.

To fix the case like above, this patch check whether target nodes AND
current task_nodes is empty, and then check whether AND
node_states[N_MEMORY] is empty.

Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Yisheng Xie <[email protected]>
Acked-by: Vlastimil Babka <[email protected]>
Cc: Andi Kleen <[email protected]>
Cc: Chris Salls <[email protected]>
Cc: Christopher Lameter <[email protected]>
Cc: David Rientjes <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Naoya Horiguchi <[email protected]>
Cc: Tan Xiaojun <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

Author: Yisheng Xie

mm/mempolicy.c

@@ -1433,10 +1433,14 @@ SYSCALL_DEFINE4(migrate_pages, pid_t, pid, unsigned long, maxnode,
 		goto out_put;
 	}
 
-	if (!nodes_subset(*new, node_states[N_MEMORY])) {
-		err = -EINVAL;
+	task_nodes = cpuset_mems_allowed(current);
+	nodes_and(*new, *new, task_nodes);
+	if (nodes_empty(*new))
+		goto out_put;
+
+	nodes_and(*new, *new, node_states[N_MEMORY]);
+	if (nodes_empty(*new))
 		goto out_put;
-	}
 
 	err = security_task_movememory(task);
 	if (err)