mac80211: use more bits for ack_frame_id

It turns out that this wasn't a good idea, I hit a test failure in
hwsim due to this. That particular failure was easily worked around,
but it raised questions: if an AP needs to, for example, send action
frames to each connected station, the current limit is nowhere near
enough (especially if those stations are sleeping and the frames are
queued for a while.)

Shuffle around some bits to make more room for ack_frame_id to allow
up to 8192 queued up frames, that's enough for queueing 4 frames to
each connected station, even at the maximum of 2007 stations on a
single AP.

We take the bits from band (which currently only 2 but I leave 3 in
case we add another band) and from the hw_queue, which can only need
4 since it has a limit of 16 queues.

Fixes: 6912daed ("mac80211: Shrink the size of ack_frame_id to make room for tx_time_est")
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Acked-by: Toke Høiland-Jørgensen <toke@redhat.com>
Link: https://lore.kernel.org/r/20200115122549.b9a4ef9f4980.Ied52ed90150220b83a280009c590b65d125d087c@changeidSigned-off-by: Johannes Berg <johannes.berg@intel.com>

include/net/mac80211.h

@@ -1004,12 +1004,11 @@ ieee80211_rate_get_vht_nss(const struct ieee80211_tx_rate *rate)
 struct ieee80211_tx_info {
 	/* common information */
 	u32 flags;
-	u8 band;
-
-	u8 hw_queue;
-
-	u16 ack_frame_id:6;
-	u16 tx_time_est:10;
+	u32 band:3,
+	    ack_frame_id:13,
+	    hw_queue:4,
+	    tx_time_est:10;
+	/* 2 free bits */
 
 	union {
 		struct {

net/mac80211/cfg.c

@@ -3450,7 +3450,7 @@ int ieee80211_attach_ack_skb(struct ieee80211_local *local, struct sk_buff *skb,
 
 	spin_lock_irqsave(&local->ack_status_lock, spin_flags);
 	id = idr_alloc(&local->ack_status_frames, ack_skb,
-		       1, 0x40, GFP_ATOMIC);
+		       1, 0x2000, GFP_ATOMIC);
 	spin_unlock_irqrestore(&local->ack_status_lock, spin_flags);
 
 	if (id < 0) {

net/mac80211/tx.c

@@ -2442,7 +2442,7 @@ static int ieee80211_store_ack_skb(struct ieee80211_local *local,
 
 		spin_lock_irqsave(&local->ack_status_lock, flags);
 		id = idr_alloc(&local->ack_status_frames, ack_skb,
-			       1, 0x40, GFP_ATOMIC);
+			       1, 0x2000, GFP_ATOMIC);
 		spin_unlock_irqrestore(&local->ack_status_lock, flags);
 
 		if (id >= 0) {