mac80211: compute chanctx refcount on-the-fly

It doesn't make much sense to store refcount in
the chanctx structure. One still needs to hold
chanctx_mtx to get the value safely. Besides,
refcount isn't on performance critical paths.

This will make implementing chanctx reservation
refcounting a little easier.

Signed-off-by: Michal Kazior <michal.kazior@tieto.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

4 files changed, 49 insertions, 17 deletions

diff --git a/net/mac80211/cfg.c b/net/mac80211/cfg.c
index 9620d4fba0d1..4d15a1566cd5 100644
--- a/net/mac80211/cfg.c
+++ b/net/mac80211/cfg.c
@@ -3251,7 +3251,7 @@ int ieee80211_channel_switch(struct wiphy *wiphy, struct net_device *dev,
 
         /* don't handle for multi-VIF cases */
         chanctx = container_of(conf, struct ieee80211_chanctx, conf);
-        if (chanctx->refcount > 1) {
+        if (ieee80211_chanctx_refcount(local, chanctx) > 1) {
                 mutex_unlock(&local->chanctx_mtx);
                 return -EBUSY;
         }
diff --git a/net/mac80211/chan.c b/net/mac80211/chan.c
index e4166b3af5d4..d8b1b8614842 100644
--- a/net/mac80211/chan.c
+++ b/net/mac80211/chan.c
@@ -9,6 +9,41 @@
 #include "ieee80211_i.h"
 #include "driver-ops.h"
 
+static int ieee80211_chanctx_num_assigned(struct ieee80211_local *local,
+                                          struct ieee80211_chanctx *ctx)
+{
+        struct ieee80211_sub_if_data *sdata;
+        int num = 0;
+
+        lockdep_assert_held(&local->chanctx_mtx);
+
+        list_for_each_entry(sdata, &ctx->assigned_vifs, assigned_chanctx_list)
+                num++;
+
+        return num;
+}
+
+static int ieee80211_chanctx_num_reserved(struct ieee80211_local *local,
+                                          struct ieee80211_chanctx *ctx)
+{
+        struct ieee80211_sub_if_data *sdata;
+        int num = 0;
+
+        lockdep_assert_held(&local->chanctx_mtx);
+
+        list_for_each_entry(sdata, &ctx->reserved_vifs, reserved_chanctx_list)
+                num++;
+
+        return num;
+}
+
+int ieee80211_chanctx_refcount(struct ieee80211_local *local,
+                               struct ieee80211_chanctx *ctx)
+{
+        return ieee80211_chanctx_num_assigned(local, ctx) +
+               ieee80211_chanctx_num_reserved(local, ctx);
+}
+
 static int ieee80211_num_chanctx(struct ieee80211_local *local)
 {
         struct ieee80211_chanctx *ctx;
@@ -463,7 +498,7 @@ static void ieee80211_free_chanctx(struct ieee80211_local *local,
 {
         lockdep_assert_held(&local->chanctx_mtx);
 
-        WARN_ON_ONCE(ctx->refcount != 0);
+        WARN_ON_ONCE(ieee80211_chanctx_refcount(local, ctx) != 0);
 
         list_del_rcu(&ctx->list);
         ieee80211_del_chanctx(local, ctx);
@@ -542,7 +577,6 @@ static int ieee80211_assign_vif_chanctx(struct ieee80211_sub_if_data *sdata,
         if (conf) {
                 curr_ctx = container_of(conf, struct ieee80211_chanctx, conf);
 
-                curr_ctx->refcount--;
                 drv_unassign_vif_chanctx(local, sdata, curr_ctx);
                 conf = NULL;
                 list_del(&sdata->assigned_chanctx_list);
@@ -553,7 +587,6 @@ static int ieee80211_assign_vif_chanctx(struct ieee80211_sub_if_data *sdata,
                 if (ret)
                         goto out;
 
-                new_ctx->refcount++;
                 conf = &new_ctx->conf;
                 list_add(&sdata->assigned_chanctx_list,
                          &new_ctx->assigned_vifs);
@@ -564,14 +597,14 @@ out:
 
         sdata->vif.bss_conf.idle = !conf;
 
-        if (curr_ctx && curr_ctx->refcount > 0) {
+        if (curr_ctx && ieee80211_chanctx_num_assigned(local, curr_ctx) > 0) {
                 ieee80211_recalc_chanctx_chantype(local, curr_ctx);
                 ieee80211_recalc_smps_chanctx(local, curr_ctx);
                 ieee80211_recalc_radar_chanctx(local, curr_ctx);
                 ieee80211_recalc_chanctx_min_def(local, curr_ctx);
         }
 
-        if (new_ctx && new_ctx->refcount > 0) {
+        if (new_ctx && ieee80211_chanctx_num_assigned(local, new_ctx) > 0) {
                 ieee80211_recalc_txpower(sdata);
                 ieee80211_recalc_chanctx_min_def(local, new_ctx);
         }
@@ -603,7 +636,7 @@ static void __ieee80211_vif_release_channel(struct ieee80211_sub_if_data *sdata)
                 ieee80211_vif_unreserve_chanctx(sdata);
 
         ieee80211_assign_vif_chanctx(sdata, NULL);
-        if (ctx->refcount == 0)
+        if (ieee80211_chanctx_refcount(local, ctx) == 0)
                 ieee80211_free_chanctx(local, ctx);
 }
 
@@ -735,7 +768,7 @@ int ieee80211_vif_use_channel(struct ieee80211_sub_if_data *sdata,
         ret = ieee80211_assign_vif_chanctx(sdata, ctx);
         if (ret) {
                 /* if assign fails refcount stays the same */
-                if (ctx->refcount == 0)
+                if (ieee80211_chanctx_refcount(local, ctx) == 0)
                         ieee80211_free_chanctx(local, ctx);
                 goto out;
         }
@@ -759,7 +792,7 @@ static int __ieee80211_vif_change_channel(struct ieee80211_sub_if_data *sdata,
                                      IEEE80211_CHAN_DISABLED))
                 return -EINVAL;
 
-        if (ctx->refcount != 1)
+        if (ieee80211_chanctx_refcount(local, ctx) != 1)
                 return -EINVAL;
 
         if (sdata->vif.bss_conf.chandef.width != chandef->width) {
@@ -865,7 +898,7 @@ int ieee80211_vif_unreserve_chanctx(struct ieee80211_sub_if_data *sdata)
         list_del(&sdata->reserved_chanctx_list);
         sdata->reserved_chanctx = NULL;
 
-        if (--ctx->refcount == 0)
+        if (ieee80211_chanctx_refcount(sdata->local, ctx) == 0)
                 ieee80211_free_chanctx(sdata->local, ctx);
 
         return 0;
@@ -894,7 +927,7 @@ int ieee80211_vif_reserve_chanctx(struct ieee80211_sub_if_data *sdata,
 
         new_ctx = ieee80211_find_reservation_chanctx(local, chandef, mode);
         if (!new_ctx) {
-                if (curr_ctx->refcount == 1 &&
+                if (ieee80211_chanctx_refcount(local, curr_ctx) == 1 &&
                     (local->hw.flags & IEEE80211_HW_CHANGE_RUNNING_CHANCTX)) {
                         /* if we're the only users of the chanctx and
                          * the driver supports changing a running
@@ -915,7 +948,6 @@ int ieee80211_vif_reserve_chanctx(struct ieee80211_sub_if_data *sdata,
         }
 
         list_add(&sdata->reserved_chanctx_list, &new_ctx->reserved_vifs);
-        new_ctx->refcount++;
         sdata->reserved_chanctx = new_ctx;
         sdata->reserved_chandef = *chandef;
         sdata->reserved_radar_required = radar_required;
@@ -961,7 +993,6 @@ int ieee80211_vif_use_reserved_context(struct ieee80211_sub_if_data *sdata,
         sdata->vif.bss_conf.chandef = sdata->reserved_chandef;
 
         /* unref our reservation */
-        ctx->refcount--;
         sdata->reserved_chanctx = NULL;
         sdata->radar_required = sdata->reserved_radar_required;
         list_del(&sdata->reserved_chanctx_list);
@@ -974,11 +1005,11 @@ int ieee80211_vif_use_reserved_context(struct ieee80211_sub_if_data *sdata,
                         goto out;
         } else {
                 ret = ieee80211_assign_vif_chanctx(sdata, ctx);
-                if (old_ctx->refcount == 0)
+                if (ieee80211_chanctx_refcount(local, old_ctx) == 0)
                         ieee80211_free_chanctx(local, old_ctx);
                 if (ret) {
                         /* if assign fails refcount stays the same */
-                        if (ctx->refcount == 0)
+                        if (ieee80211_chanctx_refcount(local, ctx) == 0)
                                 ieee80211_free_chanctx(local, ctx);
                         goto out;
                 }
diff --git a/net/mac80211/ieee80211_i.h b/net/mac80211/ieee80211_i.h
index 3eaf6d7fad52..b455f62d357a 100644
--- a/net/mac80211/ieee80211_i.h
+++ b/net/mac80211/ieee80211_i.h
@@ -695,7 +695,6 @@ struct ieee80211_chanctx {
         struct list_head reserved_vifs;
 
         enum ieee80211_chanctx_mode mode;
-        int refcount;
         bool driver_present;
 
         struct ieee80211_chanctx_conf conf;
@@ -1803,6 +1802,8 @@ void ieee80211_vif_release_channel(struct ieee80211_sub_if_data *sdata);
 void ieee80211_vif_vlan_copy_chanctx(struct ieee80211_sub_if_data *sdata);
 void ieee80211_vif_copy_chanctx_to_vlans(struct ieee80211_sub_if_data *sdata,
                                          bool clear);
+int ieee80211_chanctx_refcount(struct ieee80211_local *local,
+                               struct ieee80211_chanctx *ctx);
 
 void ieee80211_recalc_smps_chanctx(struct ieee80211_local *local,
                                    struct ieee80211_chanctx *chanctx);
diff --git a/net/mac80211/mlme.c b/net/mac80211/mlme.c
index dee50aefd6e8..98755ce49af3 100644
--- a/net/mac80211/mlme.c
+++ b/net/mac80211/mlme.c
@@ -1089,7 +1089,7 @@ ieee80211_sta_process_chanswitch(struct ieee80211_sub_if_data *sdata,
         }
         chanctx = container_of(rcu_access_pointer(sdata->vif.chanctx_conf),
                                struct ieee80211_chanctx, conf);
-        if (chanctx->refcount > 1) {
+        if (ieee80211_chanctx_refcount(local, chanctx) > 1) {
                 sdata_info(sdata,
                            "channel switch with multiple interfaces on the same channel, disconnecting\n");
                 ieee80211_queue_work(&local->hw,