[PATCH 3/3] mac80211: Set lower memory limit for non-VHT devices

[Toke Høiland-Jørgensen]

Small devices can run out of memory from queueing too many packets. If
VHT is not supported by the PHY, having more than 4 MBytes of total
queue in the TXQ intermediate queues is not needed, and so we can safely
limit the memory usage in these cases and avoid OOM.

Signed-off-by: Toke Høiland-Jørgensen <t...@toke.dk>
---
 net/mac80211/tx.c | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/net/mac80211/tx.c b/net/mac80211/tx.c
index 1ff08be..82f41fc 100644
--- a/net/mac80211/tx.c
+++ b/net/mac80211/tx.c
@@ -1434,6 +1434,8 @@ int ieee80211_txq_setup_flows(struct ieee80211_local 
*local)
        struct fq *fq = &local->fq;
        int ret;
        int i;
+       bool supp_vht = false;
+       enum nl80211_band band;
 
        if (!local->ops->wake_tx_queue)
                return 0;
@@ -1442,6 +1444,22 @@ int ieee80211_txq_setup_flows(struct ieee80211_local 
*local)
        if (ret)
                return ret;
 
+       /*
+        * If the hardware doesn't support VHT, it is safe to limit the maximum
+        * queue size. 4 Mbytes is 64 max-size aggregates in 802.11n.
+        */
+       for (band = 0; band < NUM_NL80211_BANDS; band++) {
+               struct ieee80211_supported_band *sband;
+
+               sband = local->hw.wiphy->bands[band];
+               if (!sband)
+                       continue;
+
+               supp_vht = supp_vht || sband->vht_cap.vht_supported;
+       }
+       if (!supp_vht)
+               fq->memory_limit = 4 << 20; /* 4 Mbytes */
+
        codel_params_init(&local->cparams);
        local->cparams.interval = MS2TIME(100);
        local->cparams.target = MS2TIME(20);
-- 
2.9.3