[PATCH 4.16 14/55] net_sched: fq: take care of throttled flows before reuse

Greg Kroah-Hartman
2018-05-18T08:17:28Z

From: Eric Dumazet <edumazet@google.com>

[ Upstream commit 7df40c2673a1307c3260aab6f9d4b9bf97ca8fd7 ]

Normally, a socket can not be freed/reused unless all its TX packets
left qdisc and were TX-completed. However connect(AF_UNSPEC) allows
this to happen.

With commit fc59d5bdf1e3 ("pkt_sched: fq: clear time_next_packet for
reused flows") we cleared f->time_next_packet but took no special
action if the flow was still in the throttled rb-tree.

Since f->time_next_packet is the key used in the rb-tree searches,
blindly clearing it might break rb-tree integrity. We need to make
sure the flow is no longer in the rb-tree to avoid this problem.

Fixes: fc59d5bdf1e3 ("pkt_sched: fq: clear time_next_packet for reused flows")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
net/sched/sch_fq.c | 37 +++++++++++++++++++++++++------------
1 file changed, 25 insertions(+), 12 deletions(-)

--- a/net/sched/sch_fq.c
+++ b/net/sched/sch_fq.c
@@ -128,6 +128,28 @@ static bool fq_flow_is_detached(const st
return f->next == &detached;
}

+static bool fq_flow_is_throttled(const struct fq_flow *f)
+{
+ return f->next == &throttled;
+}
+
+static void fq_flow_add_tail(struct fq_flow_head *head, struct fq_flow *flow)
+{
+ if (head->first)
+ head->last->next = flow;
+ else
+ head->first = flow;
+ head->last = flow;
+ flow->next = NULL;
+}
+
+static void fq_flow_unset_throttled(struct fq_sched_data *q, struct fq_flow *f)
+{
+ rb_erase(&f->rate_node, &q->delayed);
+ q->throttled_flows--;
+ fq_flow_add_tail(&q->old_flows, f);
+}
+
static void fq_flow_set_throttled(struct fq_sched_data *q, struct fq_flow *f)
{
struct rb_node **p = &q->delayed.rb_node, *parent = NULL;
@@ -155,15 +177,6 @@ static void fq_flow_set_throttled(struct

static struct kmem_cache *fq_flow_cachep __read_mostly;

-static void fq_flow_add_tail(struct fq_flow_head *head, struct fq_flow *flow)
-{
- if (head->first)
- head->last->next = flow;
- else
- head->first = flow;
- head->last = flow;
- flow->next = NULL;
-}

/* limit number of collected flows per round */
#define FQ_GC_MAX 8
@@ -267,6 +280,8 @@ static struct fq_flow *fq_classify(struc
f->socket_hash != sk->sk_hash)) {
f->credit = q->initial_quantum;
f->socket_hash = sk->sk_hash;
+ if (fq_flow_is_throttled(f))
+ fq_flow_unset_throttled(q, f);
f->time_next_packet = 0ULL;
}
return f;
@@ -438,9 +453,7 @@ static void fq_check_throttled(struct fq
q->time_next_delayed_flow = f->time_next_packet;
break;
}
- rb_erase(p, &q->delayed);
- q->throttled_flows--;
- fq_flow_add_tail(&q->old_flows, f);
+ fq_flow_unset_throttled(q, f);
}
}