650-Shrink-the-size-of-ack_frame_id-for-tx_time_est.patch

From 6912daed05e1370af5253aea6f2116805c0e57f8 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Toke=20H=C3=B8iland-J=C3=B8rgensen?= <toke@redhat.com>
Date: Wed, 23 Oct 2019 11:59:00 +0200
Subject: [PATCH] mac80211: Shrink the size of ack_frame_id to make room for
 tx_time_est
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To implement airtime queue limiting, we need to keep a running account of
the estimated airtime of all skbs queued into the device. Do to this
correctly, we need to store the airtime estimate into the skb so we can
decrease the outstanding balance when the skb is freed. This means that the
time estimate must be stored somewhere that will survive for the lifetime
of the skb.

To get this, decrease the size of the ack_frame_id field to 6 bits, and
lower the size of the ID space accordingly. This leaves 10 bits for use for
tx_time_est, which is enough to store a maximum of 4096 us, if we shift the
values so they become units of 4us.

Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com>
Link: https://lore.kernel.org/r/157182474063.150713.16132669599100802716.stgit@toke.dk
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
---
 include/net/mac80211.h | 4 +++-
 net/mac80211/cfg.c     | 2 +-
 net/mac80211/tx.c      | 2 +-
 3 files changed, 5 insertions(+), 3 deletions(-)

--- a/include/net/mac80211.h
+++ b/include/net/mac80211.h
@@ -961,6 +961,7 @@ ieee80211_rate_get_vht_nss(const struct
  * @band: the band to transmit on (use for checking for races)
  * @hw_queue: HW queue to put the frame on, skb_get_queue_mapping() gives the AC
  * @ack_frame_id: internal frame ID for TX status, used internally
+ * @tx_time_est: TX time estimate in units of 4us, used internally
  * @control: union part for control data
  * @control.rates: TX rates array to try
  * @control.rts_cts_rate_idx: rate for RTS or CTS
@@ -1001,7 +1002,8 @@ struct ieee80211_tx_info {

    u8 hw_queue;

-   u16 ack_frame_id;
+   u16 ack_frame_id:6;
+   u16 tx_time_est:10;

    union {
        struct {
--- a/net/mac80211/cfg.c
+++ b/net/mac80211/cfg.c
@@ -3437,7 +3437,7 @@ int ieee80211_attach_ack_skb(struct ieee

    spin_lock_irqsave(&local->ack_status_lock, spin_flags);
    id = idr_alloc(&local->ack_status_frames, ack_skb,
-              1, 0x10000, GFP_ATOMIC);
+              1, 0x40, GFP_ATOMIC);
    spin_unlock_irqrestore(&local->ack_status_lock, spin_flags);

    if (id < 0) {
--- a/net/mac80211/tx.c
+++ b/net/mac80211/tx.c
@@ -2731,7 +2731,7 @@ static struct sk_buff *ieee80211_build_h

            spin_lock_irqsave(&local->ack_status_lock, flags);
            id = idr_alloc(&local->ack_status_frames, ack_skb,
-                      1, 0x10000, GFP_ATOMIC);
+                      1, 0x40, GFP_ATOMIC);
            spin_unlock_irqrestore(&local->ack_status_lock, flags);

            if (id >= 0) {