[NETNS]: Cleanup list walking in setup_net and cleanup_net

I proposed introducing a list_for_each_entry_continue_reverse macro
to be used in setup_net() when unrolling the failed ->init callback.

Here is the macro and some more cleanup in the setup_net() itself
to remove one variable from the stack :) The same thing is for the
cleanup_net() - the existing list_for_each_entry_reverse() is used.

Minor, but the code looks nicer.

Signed-off-by: Pavel Emelyanov <xemul@openvz.org>
Acked-by: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 18 insertions, 8 deletions

diff --git a/include/linux/list.h b/include/linux/list.h
index f29fc9c1a964..ad9dcb9e3375 100644
--- a/include/linux/list.h
+++ b/include/linux/list.h
@@ -525,6 +525,20 @@ static inline void list_splice_init_rcu(struct list_head *list,
              pos = list_entry(pos->member.next, typeof(*pos), member))
 
 /**
+ * list_for_each_entry_continue_reverse - iterate backwards from the given point
+ * @pos:        the type * to use as a loop cursor.
+ * @head:       the head for your list.
+ * @member:     the name of the list_struct within the struct.
+ *
+ * Start to iterate over list of given type backwards, continuing after
+ * the current position.
+ */
+#define list_for_each_entry_continue_reverse(pos, head, member)         \
+        for (pos = list_entry(pos->member.prev, typeof(*pos), member);  \
+             prefetch(pos->member.prev), &pos->member != (head);        \
+             pos = list_entry(pos->member.prev, typeof(*pos), member))
+
+/**
  * list_for_each_entry_from - iterate over list of given type from the current point
  * @pos:        the type * to use as a loop cursor.
  * @head:       the head for your list.
diff --git a/net/core/net_namespace.c b/net/core/net_namespace.c
index 1fc513c4c79e..0e6cb02d7b77 100644
--- a/net/core/net_namespace.c
+++ b/net/core/net_namespace.c
@@ -56,7 +56,6 @@ static void net_free(struct net *net)
 static void cleanup_net(struct work_struct *work)
 {
         struct pernet_operations *ops;
-        struct list_head *ptr;
         struct net *net;
 
         net = container_of(work, struct net, work);
@@ -69,8 +68,7 @@ static void cleanup_net(struct work_struct *work)
         net_unlock();
 
         /* Run all of the network namespace exit methods */
-        list_for_each_prev(ptr, &pernet_list) {
-                ops = list_entry(ptr, struct pernet_operations, list);
+        list_for_each_entry_reverse(ops, &pernet_list, list) {
                 if (ops->exit)
                         ops->exit(net);
         }
@@ -102,7 +100,6 @@ static int setup_net(struct net *net)
 {
         /* Must be called with net_mutex held */
         struct pernet_operations *ops;
-        struct list_head *ptr;
         int error;
 
         memset(net, 0, sizeof(struct net));
@@ -110,8 +107,7 @@ static int setup_net(struct net *net)
         atomic_set(&net->use_count, 0);
 
         error = 0;
-        list_for_each(ptr, &pernet_list) {
-                ops = list_entry(ptr, struct pernet_operations, list);
+        list_for_each_entry(ops, &pernet_list, list) {
                 if (ops->init) {
                         error = ops->init(net);
                         if (error < 0)
@@ -120,12 +116,12 @@ static int setup_net(struct net *net)
         }
 out:
         return error;
+
 out_undo:
         /* Walk through the list backwards calling the exit functions
          * for the pernet modules whose init functions did not fail.
          */
-        for (ptr = ptr->prev; ptr != &pernet_list; ptr = ptr->prev) {
-                ops = list_entry(ptr, struct pernet_operations, list);
+        list_for_each_entry_continue_reverse(ops, &pernet_list, list) {
                 if (ops->exit)
                         ops->exit(net);
         }