mac80211: avoid unnecessary beacon deref on CSA counter update

The beacon struct is already available in many contexts that
are also already in an RCU read-locked section. Avoid that by
using the existing beacon struct pointer directly.

Signed-off-by: Wojciech Dubowik <Wojciech.Dubowik@neratec.com>
[rewrite subject/add commit message]
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

diff --git a/net/mac80211/tx.c b/net/mac80211/tx.c
index 87b9b4e..7c6832f 100644 (file)
--- a/net/mac80211/tx.c
+++ b/net/mac80211/tx.c
@@ -3210,6 +3210,16 @@ static void ieee80211_set_csa(struct ieee80211_sub_if_data *sdata,
        rcu_read_unlock();
 }
 
+static u8 __ieee80211_csa_update_counter(struct beacon_data *beacon)
+{
+       beacon->csa_current_counter--;
+
+       /* the counter should never reach 0 */
+       WARN_ON_ONCE(!beacon->csa_current_counter);
+
+       return beacon->csa_current_counter;
+}
+
 u8 ieee80211_csa_update_counter(struct ieee80211_vif *vif)
 {
        struct ieee80211_sub_if_data *sdata = vif_to_sdata(vif);
@@ -3228,11 +3238,7 @@ u8 ieee80211_csa_update_counter(struct ieee80211_vif *vif)
        if (!beacon)
                goto unlock;
 
-       beacon->csa_current_counter--;
-
-       /* the counter should never reach 0 */
-       WARN_ON_ONCE(!beacon->csa_current_counter);
-       count = beacon->csa_current_counter;
+       count = __ieee80211_csa_update_counter(beacon);
 
 unlock:
        rcu_read_unlock();
@@ -3332,7 +3338,7 @@ __ieee80211_beacon_get(struct ieee80211_hw *hw,
                if (beacon) {
                        if (beacon->csa_counter_offsets[0]) {
                                if (!is_template)
-                                       ieee80211_csa_update_counter(vif);
+                                       __ieee80211_csa_update_counter(beacon);
 
                                ieee80211_set_csa(sdata, beacon);
                        }
@@ -3378,7 +3384,7 @@ __ieee80211_beacon_get(struct ieee80211_hw *hw,
 
                if (beacon->csa_counter_offsets[0]) {
                        if (!is_template)
-                               ieee80211_csa_update_counter(vif);
+                               __ieee80211_csa_update_counter(beacon);
 
                        ieee80211_set_csa(sdata, beacon);
                }
@@ -3408,7 +3414,7 @@ __ieee80211_beacon_get(struct ieee80211_hw *hw,
                                 * for now we leave it consistent with overall
                                 * mac80211's behavior.
                                 */
-                               ieee80211_csa_update_counter(vif);
+                               __ieee80211_csa_update_counter(beacon);
 
                        ieee80211_set_csa(sdata, beacon);
                }