pkt_sched: fq: do not hold qdisc lock while allocating memory

Resizing fq hash table allocates memory while holding qdisc spinlock,
with BH disabled.

This is definitely not good, as allocation might sleep.

We can drop the lock and get it when needed, we hold RTNL so no other
changes can happen at the same time.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Fixes: afe4fd062416 ("pkt_sched: fq: Fair Queue packet scheduler")
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/sched/sch_fq.c b/net/sched/sch_fq.c
index 08ef7a42c0e411657e789cb140fad522aef97ed1..21e251766eb1a099c8f603c1f7bb5d33ec5b04a2 100644 (file)
--- a/net/sched/sch_fq.c
+++ b/net/sched/sch_fq.c
@@ -601,6 +601,7 @@ static int fq_resize(struct Qdisc *sch, u32 log)
 {
        struct fq_sched_data *q = qdisc_priv(sch);
        struct rb_root *array;
+       void *old_fq_root;
        u32 idx;
 
        if (q->fq_root && log == q->fq_trees_log)
@@ -615,13 +616,19 @@ static int fq_resize(struct Qdisc *sch, u32 log)
        for (idx = 0; idx < (1U << log); idx++)
                array[idx] = RB_ROOT;
 
-       if (q->fq_root) {
-               fq_rehash(q, q->fq_root, q->fq_trees_log, array, log);
-               fq_free(q->fq_root);
-       }
+       sch_tree_lock(sch);
+
+       old_fq_root = q->fq_root;
+       if (old_fq_root)
+               fq_rehash(q, old_fq_root, q->fq_trees_log, array, log);
+
        q->fq_root = array;
        q->fq_trees_log = log;
 
+       sch_tree_unlock(sch);
+
+       fq_free(old_fq_root);
+
        return 0;
 }
 
@@ -697,9 +704,11 @@ static int fq_change(struct Qdisc *sch, struct nlattr *opt)
                q->flow_refill_delay = usecs_to_jiffies(usecs_delay);
        }
 
-       if (!err)
+       if (!err) {
+               sch_tree_unlock(sch);
                err = fq_resize(sch, fq_log);
-
+               sch_tree_lock(sch);
+       }
        while (sch->q.qlen > sch->limit) {
                struct sk_buff *skb = fq_dequeue(sch);