fq.h: Port memory limit mechanism from fq_codel

The reusable fairness queueing implementation (fq.h) lacks the memory
usage limit that the fq_codel qdisc has. This means that small
devices (e.g. WiFi routers) can run out of memory when flooded with a
large number of packets. This ports the memory limit feature from
fq_codel to fq.h.

Signed-off-by: Toke Høiland-Jørgensen <toke@toke.dk>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

include/net/fq.h

@@ -72,9 +72,12 @@ struct fq {
 	u32 flows_cnt;
 	u32 perturbation;
 	u32 limit;
+	u32 memory_limit;
+	u32 memory_usage;
 	u32 quantum;
 	u32 backlog;
 	u32 overlimit;
+	u32 overmemory;
 	u32 collisions;
 };