mac80211: implement chanctx reservation

In order to support channel switch with multiple vifs and multiple
contexts, we implement a concept of channel context reservation.  This
allows us to reserve a channel context to be used later.

The reservation functionality is not tied directly to channel switch
and may be used in other situations (eg. reserving a channel context
during IBSS join).

We first check if an existing compatible context exists and if it
does, we reserve it.  If there is no compatible context we create a
new one and reserve it.

Additionally, split ieee80211_vif_copy_chanctx_to_vlans() so we can
call it while already holding the chanctx mutex.

Signed-off-by: Luciano Coelho <luciano.coelho@intel.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

diff --git a/net/mac80211/chan.c b/net/mac80211/chan.c
index 35079c8..baad756 100644 (file)
--- a/net/mac80211/chan.c
+++ b/net/mac80211/chan.c
@@ -426,6 +426,9 @@ static void __ieee80211_vif_release_channel(struct ieee80211_sub_if_data *sdata)
 
        ctx = container_of(conf, struct ieee80211_chanctx, conf);
 
+       if (sdata->reserved_chanctx)
+               ieee80211_vif_unreserve_chanctx(sdata);
+
        ieee80211_assign_vif_chanctx(sdata, NULL);
        if (ctx->refcount == 0)
                ieee80211_free_chanctx(local, ctx);
@@ -635,6 +638,166 @@ int ieee80211_vif_change_channel(struct ieee80211_sub_if_data *sdata,
        return ret;
 }
 
+static void
+__ieee80211_vif_copy_chanctx_to_vlans(struct ieee80211_sub_if_data *sdata,
+                                     bool clear)
+{
+       struct ieee80211_local *local = sdata->local;
+       struct ieee80211_sub_if_data *vlan;
+       struct ieee80211_chanctx_conf *conf;
+
+       if (WARN_ON(sdata->vif.type != NL80211_IFTYPE_AP))
+               return;
+
+       lockdep_assert_held(&local->mtx);
+
+       /* Check that conf exists, even when clearing this function
+        * must be called with the AP's channel context still there
+        * as it would otherwise cause VLANs to have an invalid
+        * channel context pointer for a while, possibly pointing
+        * to a channel context that has already been freed.
+        */
+       conf = rcu_dereference_protected(sdata->vif.chanctx_conf,
+                               lockdep_is_held(&local->chanctx_mtx));
+       WARN_ON(!conf);
+
+       if (clear)
+               conf = NULL;
+
+       list_for_each_entry(vlan, &sdata->u.ap.vlans, u.vlan.list)
+               rcu_assign_pointer(vlan->vif.chanctx_conf, conf);
+}
+
+void ieee80211_vif_copy_chanctx_to_vlans(struct ieee80211_sub_if_data *sdata,
+                                        bool clear)
+{
+       struct ieee80211_local *local = sdata->local;
+
+       mutex_lock(&local->chanctx_mtx);
+
+       __ieee80211_vif_copy_chanctx_to_vlans(sdata, clear);
+
+       mutex_unlock(&local->chanctx_mtx);
+}
+
+int ieee80211_vif_unreserve_chanctx(struct ieee80211_sub_if_data *sdata)
+{
+       lockdep_assert_held(&sdata->local->chanctx_mtx);
+
+       if (WARN_ON(!sdata->reserved_chanctx))
+               return -EINVAL;
+
+       if (--sdata->reserved_chanctx->refcount == 0)
+               ieee80211_free_chanctx(sdata->local, sdata->reserved_chanctx);
+
+       sdata->reserved_chanctx = NULL;
+
+       return 0;
+}
+
+int ieee80211_vif_reserve_chanctx(struct ieee80211_sub_if_data *sdata,
+                                 const struct cfg80211_chan_def *chandef,
+                                 enum ieee80211_chanctx_mode mode)
+{
+       struct ieee80211_local *local = sdata->local;
+       struct ieee80211_chanctx_conf *conf;
+       struct ieee80211_chanctx *new_ctx, *curr_ctx;
+       int ret = 0;
+
+       mutex_lock(&local->chanctx_mtx);
+
+       conf = rcu_dereference_protected(sdata->vif.chanctx_conf,
+                                        lockdep_is_held(&local->chanctx_mtx));
+       if (!conf) {
+               ret = -EINVAL;
+               goto out;
+       }
+
+       curr_ctx = container_of(conf, struct ieee80211_chanctx, conf);
+
+       /* try to find another context with the chandef we want */
+       new_ctx = ieee80211_find_chanctx(local, chandef, mode);
+       if (!new_ctx) {
+               /* create a new context */
+               new_ctx = ieee80211_new_chanctx(local, chandef, mode);
+               if (IS_ERR(new_ctx)) {
+                       ret = PTR_ERR(new_ctx);
+                       goto out;
+               }
+       }
+
+       new_ctx->refcount++;
+       sdata->reserved_chanctx = new_ctx;
+       sdata->reserved_chandef = *chandef;
+out:
+       mutex_unlock(&local->chanctx_mtx);
+       return ret;
+}
+
+int ieee80211_vif_use_reserved_context(struct ieee80211_sub_if_data *sdata,
+                                      u32 *changed)
+{
+       struct ieee80211_local *local = sdata->local;
+       struct ieee80211_chanctx *ctx;
+       struct ieee80211_chanctx *old_ctx;
+       struct ieee80211_chanctx_conf *conf;
+       int ret;
+       u32 tmp_changed = *changed;
+
+       /* TODO: need to recheck if the chandef is usable etc.? */
+
+       lockdep_assert_held(&local->mtx);
+
+       mutex_lock(&local->chanctx_mtx);
+
+       ctx = sdata->reserved_chanctx;
+       if (WARN_ON(!ctx)) {
+               ret = -EINVAL;
+               goto out;
+       }
+
+       conf = rcu_dereference_protected(sdata->vif.chanctx_conf,
+                                        lockdep_is_held(&local->chanctx_mtx));
+       if (!conf) {
+               ret = -EINVAL;
+               goto out;
+       }
+
+       old_ctx = container_of(conf, struct ieee80211_chanctx, conf);
+
+       if (sdata->vif.bss_conf.chandef.width != sdata->reserved_chandef.width)
+               tmp_changed |= BSS_CHANGED_BANDWIDTH;
+
+       sdata->vif.bss_conf.chandef = sdata->reserved_chandef;
+
+       /* unref our reservation before assigning */
+       ctx->refcount--;
+       sdata->reserved_chanctx = NULL;
+
+       ret = ieee80211_assign_vif_chanctx(sdata, ctx);
+       if (old_ctx->refcount == 0)
+               ieee80211_free_chanctx(local, old_ctx);
+       if (ret) {
+               /* if assign fails refcount stays the same */
+               if (ctx->refcount == 0)
+                       ieee80211_free_chanctx(local, ctx);
+               goto out;
+       }
+
+       if (sdata->vif.type == NL80211_IFTYPE_AP)
+               __ieee80211_vif_copy_chanctx_to_vlans(sdata, false);
+
+       *changed = tmp_changed;
+
+       ieee80211_recalc_chanctx_chantype(local, ctx);
+       ieee80211_recalc_smps_chanctx(local, ctx);
+       ieee80211_recalc_radar_chanctx(local, ctx);
+       ieee80211_recalc_chanctx_min_def(local, ctx);
+out:
+       mutex_unlock(&local->chanctx_mtx);
+       return ret;
+}
+
 int ieee80211_vif_change_bandwidth(struct ieee80211_sub_if_data *sdata,
                                   const struct cfg80211_chan_def *chandef,
                                   u32 *changed)
@@ -714,40 +877,6 @@ void ieee80211_vif_vlan_copy_chanctx(struct ieee80211_sub_if_data *sdata)
        mutex_unlock(&local->chanctx_mtx);
 }
 
-void ieee80211_vif_copy_chanctx_to_vlans(struct ieee80211_sub_if_data *sdata,
-                                        bool clear)
-{
-       struct ieee80211_local *local = sdata->local;
-       struct ieee80211_sub_if_data *vlan;
-       struct ieee80211_chanctx_conf *conf;
-
-       lockdep_assert_held(&local->mtx);
-
-       if (WARN_ON(sdata->vif.type != NL80211_IFTYPE_AP))
-               return;
-
-       mutex_lock(&local->chanctx_mtx);
-
-       /*
-        * Check that conf exists, even when clearing this function
-        * must be called with the AP's channel context still there
-        * as it would otherwise cause VLANs to have an invalid
-        * channel context pointer for a while, possibly pointing
-        * to a channel context that has already been freed.
-        */
-       conf = rcu_dereference_protected(sdata->vif.chanctx_conf,
-                               lockdep_is_held(&local->chanctx_mtx));
-       WARN_ON(!conf);
-
-       if (clear)
-               conf = NULL;
-
-       list_for_each_entry(vlan, &sdata->u.ap.vlans, u.vlan.list)
-               rcu_assign_pointer(vlan->vif.chanctx_conf, conf);
-
-       mutex_unlock(&local->chanctx_mtx);
-}
-
 void ieee80211_iter_chan_contexts_atomic(
        struct ieee80211_hw *hw,
        void (*iter)(struct ieee80211_hw *hw,

diff --git a/net/mac80211/ieee80211_i.h b/net/mac80211/ieee80211_i.h
index c422f81..3dd2111 100644 (file)
--- a/net/mac80211/ieee80211_i.h
+++ b/net/mac80211/ieee80211_i.h
@@ -756,6 +756,10 @@ struct ieee80211_sub_if_data {
        bool csa_radar_required;
        struct cfg80211_chan_def csa_chandef;
 
+       /* context reservation -- protected with chanctx_mtx */
+       struct ieee80211_chanctx *reserved_chanctx;
+       struct cfg80211_chan_def reserved_chandef;
+
        /* used to reconfigure hardware SM PS */
        struct work_struct recalc_smps;
 
@@ -1771,6 +1775,15 @@ ieee80211_vif_use_channel(struct ieee80211_sub_if_data *sdata,
                          const struct cfg80211_chan_def *chandef,
                          enum ieee80211_chanctx_mode mode);
 int __must_check
+ieee80211_vif_reserve_chanctx(struct ieee80211_sub_if_data *sdata,
+                             const struct cfg80211_chan_def *chandef,
+                             enum ieee80211_chanctx_mode mode);
+int __must_check
+ieee80211_vif_use_reserved_context(struct ieee80211_sub_if_data *sdata,
+                                  u32 *changed);
+int ieee80211_vif_unreserve_chanctx(struct ieee80211_sub_if_data *sdata);
+
+int __must_check
 ieee80211_vif_change_bandwidth(struct ieee80211_sub_if_data *sdata,
                               const struct cfg80211_chan_def *chandef,
                               u32 *changed);