mac80211: track reserved vifs in chanctx

This can be useful. Provides a more straghtforward
way to iterate over interfaces taking part in
chanctx reservation and allows tracking chanctx
usage explicitly.

The structure is protected by local->chanctx_mtx.

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

net/mac80211/chan.c

@@ -277,6 +277,7 @@ ieee80211_new_chanctx(struct ieee80211_local *local,
 		return ERR_PTR(-ENOMEM);
 
 	INIT_LIST_HEAD(&ctx->assigned_vifs);
+	INIT_LIST_HEAD(&ctx->reserved_vifs);
 	ctx->conf.def = *chandef;
 	ctx->conf.rx_chains_static = 1;
 	ctx->conf.rx_chains_dynamic = 1;
@@ -731,16 +732,19 @@ void ieee80211_vif_copy_chanctx_to_vlans(struct ieee80211_sub_if_data *sdata,
 
 int ieee80211_vif_unreserve_chanctx(struct ieee80211_sub_if_data *sdata)
 {
+	struct ieee80211_chanctx *ctx = sdata->reserved_chanctx;
+
 	lockdep_assert_held(&sdata->local->chanctx_mtx);
 
-	if (WARN_ON(!sdata->reserved_chanctx))
+	if (WARN_ON(!ctx))
 		return -EINVAL;
 
-	if (--sdata->reserved_chanctx->refcount == 0)
-		ieee80211_free_chanctx(sdata->local, sdata->reserved_chanctx);
-
+	list_del(&sdata->reserved_chanctx_list);
 	sdata->reserved_chanctx = NULL;
 
+	if (--ctx->refcount == 0)
+		ieee80211_free_chanctx(sdata->local, ctx);
+
 	return 0;
 }
 
@@ -788,6 +792,7 @@ 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;
@@ -837,6 +842,7 @@ int ieee80211_vif_use_reserved_context(struct ieee80211_sub_if_data *sdata,
 	ctx->refcount--;
 	sdata->reserved_chanctx = NULL;
 	sdata->radar_required = sdata->reserved_radar_required;
+	list_del(&sdata->reserved_chanctx_list);
 
 	if (old_ctx == ctx) {
 		/* This is our own context, just change it */

net/mac80211/ieee80211_i.h

@@ -692,6 +692,7 @@ struct ieee80211_chanctx {
 	struct rcu_head rcu_head;
 
 	struct list_head assigned_vifs;
+	struct list_head reserved_vifs;
 
 	enum ieee80211_chanctx_mode mode;
 	int refcount;
@@ -759,6 +760,7 @@ struct ieee80211_sub_if_data {
 	struct cfg80211_chan_def csa_chandef;
 
 	struct list_head assigned_chanctx_list; /* protected by chanctx_mtx */
+	struct list_head reserved_chanctx_list; /* protected by chanctx_mtx */
 
 	/* context reservation -- protected with chanctx_mtx */
 	struct ieee80211_chanctx *reserved_chanctx;

net/mac80211/iface.c

@@ -1292,6 +1292,7 @@ static void ieee80211_setup_sdata(struct ieee80211_sub_if_data *sdata,
 	INIT_WORK(&sdata->recalc_smps, ieee80211_recalc_smps_work);
 	INIT_WORK(&sdata->csa_finalize_work, ieee80211_csa_finalize_work);
 	INIT_LIST_HEAD(&sdata->assigned_chanctx_list);
+	INIT_LIST_HEAD(&sdata->reserved_chanctx_list);
 
 	switch (type) {
 	case NL80211_IFTYPE_P2P_GO: