pkt_sched: Make qdisc grafting locking more specific.

Lock the root of the qdisc being operated upon.

All explicit references to qdisc_tree_lock() are now gone.
The only remaining uses are via the sch_tree_{lock,unlock}()
and tcf_tree_{lock,unlock}() macros.

Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 29 insertions, 12 deletions

diff --git a/net/sched/sch_api.c b/net/sched/sch_api.c
index 6958fe7c9a77..74924893ef7f 100644
--- a/net/sched/sch_api.c
+++ b/net/sched/sch_api.c
@@ -441,15 +441,29 @@ static struct Qdisc *
 dev_graft_qdisc(struct net_device *dev, struct Qdisc *qdisc)
 {
         struct netdev_queue *dev_queue;
+        spinlock_t *root_lock;
         struct Qdisc *oqdisc;
+        int ingress;
 
         if (dev->flags & IFF_UP)
                 dev_deactivate(dev);
 
-        qdisc_lock_tree(dev);
-        if (qdisc && qdisc->flags&TCQ_F_INGRESS) {
+        ingress = 0;
+        if (qdisc && qdisc->flags&TCQ_F_INGRESS)
+                ingress = 1;
+
+        if (ingress) {
                 dev_queue = &dev->rx_queue;
                 oqdisc = dev_queue->qdisc;
+        } else {
+                dev_queue = netdev_get_tx_queue(dev, 0);
+                oqdisc = dev_queue->qdisc_sleeping;
+        }
+
+        root_lock = qdisc_root_lock(oqdisc);
+        spin_lock_bh(root_lock);
+
+        if (ingress) {
                 /* Prune old scheduler */
                 if (oqdisc && atomic_read(&oqdisc->refcnt) <= 1) {
                         /* delete */
@@ -460,9 +474,6 @@ dev_graft_qdisc(struct net_device *dev, struct Qdisc *qdisc)
                 }
 
         } else {
-                dev_queue = netdev_get_tx_queue(dev, 0);
-                oqdisc = dev_queue->qdisc_sleeping;
-
                 /* Prune old scheduler */
                 if (oqdisc && atomic_read(&oqdisc->refcnt) <= 1)
                         qdisc_reset(oqdisc);
@@ -474,7 +485,7 @@ dev_graft_qdisc(struct net_device *dev, struct Qdisc *qdisc)
                 dev_queue->qdisc = &noop_qdisc;
         }
 
-        qdisc_unlock_tree(dev);
+        spin_unlock_bh(root_lock);
 
         if (dev->flags & IFF_UP)
                 dev_activate(dev);
@@ -765,10 +776,12 @@ static int tc_get_qdisc(struct sk_buff *skb, struct nlmsghdr *n, void *arg)
                 if ((err = qdisc_graft(dev, p, clid, NULL, &q)) != 0)
                         return err;
                 if (q) {
+                        spinlock_t *root_lock = qdisc_root_lock(q);
+
                         qdisc_notify(skb, n, clid, q, NULL);
-                        qdisc_lock_tree(dev);
+                        spin_unlock_bh(root_lock);
                         qdisc_destroy(q);
-                        qdisc_unlock_tree(dev);
+                        spin_unlock_bh(root_lock);
                 }
         } else {
                 qdisc_notify(skb, n, clid, NULL, q);
@@ -911,20 +924,24 @@ create_n_graft:
 graft:
         if (1) {
                 struct Qdisc *old_q = NULL;
+                spinlock_t *root_lock;
+
                 err = qdisc_graft(dev, p, clid, q, &old_q);
                 if (err) {
                         if (q) {
-                                qdisc_lock_tree(dev);
+                                root_lock = qdisc_root_lock(q);
+                                spin_lock_bh(root_lock);
                                 qdisc_destroy(q);
-                                qdisc_unlock_tree(dev);
+                                spin_unlock_bh(root_lock);
                         }
                         return err;
                 }
                 qdisc_notify(skb, n, clid, old_q, q);
                 if (old_q) {
-                        qdisc_lock_tree(dev);
+                        root_lock = qdisc_root_lock(old_q);
+                        spin_lock_bh(root_lock);
                         qdisc_destroy(old_q);
-                        qdisc_unlock_tree(dev);
+                        spin_unlock_bh(root_lock);
                 }
         }
         return 0;