mac80211: Fix sleeping allocation under lock in mesh_path_node_copy.

The mesh_path_node_copy() can be called like this:
mesh_path_add
 `- write_lock(&pathtbl_resize_lock); /* ! */
 `- mesh_table_grow
     `- ->copy_node
           `- mesh_path_node_copy

thus, the GFP_KERNEL is not suitable here.

The acceptable fix, I suppose, is make this allocation GPF_ATOMIC -
the mpath_node being allocated is 4 pointers, i.e. this allocation
is small enough to survive even under a moderate memory pressure.
Signed-off-by: NPavel Emelyanov <xemul@openvz.org>
Signed-off-by: NJohn W. Linville <linville@tuxdriver.com>

net/mac80211/mesh_pathtbl.c

@@ -469,7 +469,7 @@ static int mesh_path_node_copy(struct hlist_node *p, struct mesh_table *newtbl)
 	struct mpath_node *node, *new_node;
 	u32 hash_idx;
 
-	new_node = kmalloc(sizeof(struct mpath_node), GFP_KERNEL);
+	new_node = kmalloc(sizeof(struct mpath_node), GFP_ATOMIC);
 	if (new_node == NULL)
 		return -ENOMEM;