1 files changed, 50 insertions, 22 deletions

diff --git a/net/core/netprio_cgroup.c b/net/core/netprio_cgroup.c
index 9409cdf9f268..b2af0d099663 100644
--- a/net/core/netprio_cgroup.c
+++ b/net/core/netprio_cgroup.c
@@ -87,6 +87,51 @@ static int extend_netdev_table(struct net_device *dev, u32 target_idx)
         return 0;
 }
 
+/**
+ * netprio_prio - return the effective netprio of a cgroup-net_device pair
+ * @cgrp: cgroup part of the target pair
+ * @dev: net_device part of the target pair
+ *
+ * Should be called under RCU read or rtnl lock.
+ */
+static u32 netprio_prio(struct cgroup *cgrp, struct net_device *dev)
+{
+        struct netprio_map *map = rcu_dereference_rtnl(dev->priomap);
+
+        if (map && cgrp->id < map->priomap_len)
+                return map->priomap[cgrp->id];
+        return 0;
+}
+
+/**
+ * netprio_set_prio - set netprio on a cgroup-net_device pair
+ * @cgrp: cgroup part of the target pair
+ * @dev: net_device part of the target pair
+ * @prio: prio to set
+ *
+ * Set netprio to @prio on @cgrp-@dev pair.  Should be called under rtnl
+ * lock and may fail under memory pressure for non-zero @prio.
+ */
+static int netprio_set_prio(struct cgroup *cgrp, struct net_device *dev,
+                            u32 prio)
+{
+        struct netprio_map *map;
+        int ret;
+
+        /* avoid extending priomap for zero writes */
+        map = rtnl_dereference(dev->priomap);
+        if (!prio && (!map || map->priomap_len <= cgrp->id))
+                return 0;
+
+        ret = extend_netdev_table(dev, cgrp->id);
+        if (ret)
+                return ret;
+
+        map = rtnl_dereference(dev->priomap);
+        map->priomap[cgrp->id] = prio;
+        return 0;
+}
+
 static struct cgroup_subsys_state *cgrp_css_alloc(struct cgroup *cgrp)
 {
         struct cgroup_netprio_state *cs;
@@ -105,14 +150,10 @@ static void cgrp_css_free(struct cgroup *cgrp)
 {
         struct cgroup_netprio_state *cs = cgrp_netprio_state(cgrp);
         struct net_device *dev;
-        struct netprio_map *map;
 
         rtnl_lock();
-        for_each_netdev(&init_net, dev) {
-                map = rtnl_dereference(dev->priomap);
-                if (map && cgrp->id < map->priomap_len)
-                        map->priomap[cgrp->id] = 0;
-        }
+        for_each_netdev(&init_net, dev)
+                WARN_ON_ONCE(netprio_set_prio(cgrp, dev, 0));
         rtnl_unlock();
         kfree(cs);
 }
@@ -126,16 +167,10 @@ static int read_priomap(struct cgroup *cont, struct cftype *cft,
                         struct cgroup_map_cb *cb)
 {
         struct net_device *dev;
-        u32 id = cont->id;
-        u32 priority;
-        struct netprio_map *map;
 
         rcu_read_lock();
-        for_each_netdev_rcu(&init_net, dev) {
-                map = rcu_dereference(dev->priomap);
-                priority = (map && id < map->priomap_len) ? map->priomap[id] : 0;
-                cb->fill(cb, dev->name, priority);
-        }
+        for_each_netdev_rcu(&init_net, dev)
+                cb->fill(cb, dev->name, netprio_prio(cont, dev));
         rcu_read_unlock();
         return 0;
 }
@@ -145,7 +180,6 @@ static int write_priomap(struct cgroup *cgrp, struct cftype *cft,
 {
         char devname[IFNAMSIZ + 1];
         struct net_device *dev;
-        struct netprio_map *map;
         u32 prio;
         int ret;
 
@@ -158,14 +192,8 @@ static int write_priomap(struct cgroup *cgrp, struct cftype *cft,
 
         rtnl_lock();
 
-        ret = extend_netdev_table(dev, cgrp->id);
-        if (ret)
-                goto out_unlock;
+        ret = netprio_set_prio(cgrp, dev, prio);
 
-        map = rtnl_dereference(dev->priomap);
-        if (map)
-                map->priomap[cgrp->id] = prio;
-out_unlock:
         rtnl_unlock();
         dev_put(dev);
         return ret;