net_sched: move dev_graft_qdisc() to sch_generic.c

It will be used in a following patch by the multiqueue qdisc.

Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 25 insertions, 0 deletions

diff --git a/net/sched/sch_generic.c b/net/sched/sch_generic.c
index a91f079fb47a..e7c47ceb0098 100644
--- a/net/sched/sch_generic.c
+++ b/net/sched/sch_generic.c
@@ -623,6 +623,31 @@ void qdisc_destroy(struct Qdisc *qdisc)
 }
 EXPORT_SYMBOL(qdisc_destroy);
 
+/* Attach toplevel qdisc to device queue. */
+struct Qdisc *dev_graft_qdisc(struct netdev_queue *dev_queue,
+                              struct Qdisc *qdisc)
+{
+        struct Qdisc *oqdisc = dev_queue->qdisc_sleeping;
+        spinlock_t *root_lock;
+
+        root_lock = qdisc_lock(oqdisc);
+        spin_lock_bh(root_lock);
+
+        /* Prune old scheduler */
+        if (oqdisc && atomic_read(&oqdisc->refcnt) <= 1)
+                qdisc_reset(oqdisc);
+
+        /* ... and graft new one */
+        if (qdisc == NULL)
+                qdisc = &noop_qdisc;
+        dev_queue->qdisc_sleeping = qdisc;
+        rcu_assign_pointer(dev_queue->qdisc, &noop_qdisc);
+
+        spin_unlock_bh(root_lock);
+
+        return oqdisc;
+}
+
 static void attach_one_default_qdisc(struct net_device *dev,
                                      struct netdev_queue *dev_queue,
                                      void *_unused)