mac80211: clean up mesh sta allocation warning

This refactoring fixes a "scheduling while atomic" warning
when allocating a mesh station entry while holding the RCU
read lock. Fix this by creating a new function
mesh_sta_info_get(), which correctly handles the locking
and returns under RCU.

Also move some unnecessarily #ifdefed mesh station init
code from sta_info_alloc() to __mesh_sta_info_alloc().

Signed-off-by: Thomas Pedersen <thomas@cozybit.com>
[change code flow to make sparse happy]
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

1 files changed, 95 insertions, 63 deletions

diff --git a/net/mac80211/mesh_plink.c b/net/mac80211/mesh_plink.c
index 9e0416696a83..ef92d2705851 100644
--- a/net/mac80211/mesh_plink.c
+++ b/net/mac80211/mesh_plink.c
@@ -55,30 +55,6 @@ static inline void mesh_plink_fsm_restart(struct sta_info *sta)
         sta->plink_retries = 0;
 }
 
-/*
- * Allocate mesh sta entry and insert into station table
- */
-static struct sta_info *mesh_plink_alloc(struct ieee80211_sub_if_data *sdata,
-                                         u8 *hw_addr)
-{
-        struct sta_info *sta;
-
-        if (sdata->local->num_sta >= MESH_MAX_PLINKS)
-                return NULL;
-
-        sta = sta_info_alloc(sdata, hw_addr, GFP_KERNEL);
-        if (!sta)
-                return NULL;
-
-        sta_info_pre_move_state(sta, IEEE80211_STA_AUTH);
-        sta_info_pre_move_state(sta, IEEE80211_STA_ASSOC);
-        sta_info_pre_move_state(sta, IEEE80211_STA_AUTHORIZED);
-
-        set_sta_flag(sta, WLAN_STA_WME);
-
-        return sta;
-}
-
 /**
  * mesh_set_ht_prot_mode - set correct HT protection mode
  *
@@ -309,52 +285,24 @@ free:
         return err;
 }
 
-/**
- * mesh_peer_init - initialize new mesh peer and return resulting sta_info
- *
- * @sdata: local meshif
- * @addr: peer's address
- * @elems: IEs from beacon or mesh peering frame
- *
- * call under RCU
- */
-static struct sta_info *mesh_peer_init(struct ieee80211_sub_if_data *sdata,
-                                       u8 *addr,
-                                       struct ieee802_11_elems *elems)
+static void mesh_sta_info_init(struct ieee80211_sub_if_data *sdata,
+                               struct sta_info *sta,
+                               struct ieee802_11_elems *elems, bool insert)
 {
         struct ieee80211_local *local = sdata->local;
         enum ieee80211_band band = ieee80211_get_sdata_band(sdata);
         struct ieee80211_supported_band *sband;
         u32 rates, basic_rates = 0;
-        struct sta_info *sta;
-        bool insert = false;
 
         sband = local->hw.wiphy->bands[band];
         rates = ieee80211_sta_get_rates(local, elems, band, &basic_rates);
 
-        sta = sta_info_get(sdata, addr);
-        if (!sta) {
-                /* Userspace handles peer allocation when security is enabled */
-                if (sdata->u.mesh.security & IEEE80211_MESH_SEC_AUTHED) {
-                        cfg80211_notify_new_peer_candidate(sdata->dev, addr,
-                                                           elems->ie_start,
-                                                           elems->total_len,
-                                                           GFP_ATOMIC);
-                        return NULL;
-                }
-
-                sta = mesh_plink_alloc(sdata, addr);
-                if (!sta)
-                        return NULL;
-                insert = true;
-        }
-
         spin_lock_bh(&sta->lock);
         sta->last_rx = jiffies;
-        if (sta->plink_state == NL80211_PLINK_ESTAB) {
-                spin_unlock_bh(&sta->lock);
-                return sta;
-        }
+
+        /* rates and capabilities don't change during peering */
+        if (sta->plink_state == NL80211_PLINK_ESTAB)
+                goto out;
 
         sta->sta.supp_rates[band] = rates;
         if (elems->ht_cap_elem &&
@@ -379,22 +327,104 @@ static struct sta_info *mesh_peer_init(struct ieee80211_sub_if_data *sdata,
 
         if (insert)
                 rate_control_rate_init(sta);
+out:
         spin_unlock_bh(&sta->lock);
+}
+
+static struct sta_info *
+__mesh_sta_info_alloc(struct ieee80211_sub_if_data *sdata, u8 *hw_addr)
+{
+        struct sta_info *sta;
 
-        if (insert && sta_info_insert(sta))
+        if (sdata->local->num_sta >= MESH_MAX_PLINKS)
                 return NULL;
 
+        sta = sta_info_alloc(sdata, hw_addr, GFP_KERNEL);
+        if (!sta)
+                return NULL;
+
+        sta->plink_state = NL80211_PLINK_LISTEN;
+        init_timer(&sta->plink_timer);
+
+        sta_info_pre_move_state(sta, IEEE80211_STA_AUTH);
+        sta_info_pre_move_state(sta, IEEE80211_STA_ASSOC);
+        sta_info_pre_move_state(sta, IEEE80211_STA_AUTHORIZED);
+
+        set_sta_flag(sta, WLAN_STA_WME);
+
+        return sta;
+}
+
+static struct sta_info *
+mesh_sta_info_alloc(struct ieee80211_sub_if_data *sdata, u8 *addr,
+                    struct ieee802_11_elems *elems)
+{
+        struct sta_info *sta = NULL;
+
+        /* Userspace handles peer allocation when security is enabled */
+        if (sdata->u.mesh.security & IEEE80211_MESH_SEC_AUTHED)
+                cfg80211_notify_new_peer_candidate(sdata->dev, addr,
+                                                   elems->ie_start,
+                                                   elems->total_len,
+                                                   GFP_KERNEL);
+        else
+                sta = __mesh_sta_info_alloc(sdata, addr);
+
         return sta;
 }
 
+/*
+ * mesh_sta_info_get - return mesh sta info entry for @addr.
+ *
+ * @sdata: local meshif
+ * @addr: peer's address
+ * @elems: IEs from beacon or mesh peering frame.
+ *
+ * Return existing or newly allocated sta_info under RCU read lock.
+ * (re)initialize with given IEs.
+ */
+static struct sta_info *
+mesh_sta_info_get(struct ieee80211_sub_if_data *sdata,
+                  u8 *addr, struct ieee802_11_elems *elems) __acquires(RCU)
+{
+        struct sta_info *sta = NULL;
+
+        rcu_read_lock();
+        sta = sta_info_get(sdata, addr);
+        if (sta) {
+                mesh_sta_info_init(sdata, sta, elems, false);
+        } else {
+                rcu_read_unlock();
+                /* can't run atomic */
+                sta = mesh_sta_info_alloc(sdata, addr, elems);
+                if (!sta) {
+                        rcu_read_lock();
+                        return NULL;
+                }
+
+                if (sta_info_insert_rcu(sta))
+                        return NULL;
+        }
+
+        return sta;
+}
+
+/*
+ * mesh_neighbour_update - update or initialize new mesh neighbor.
+ *
+ * @sdata: local meshif
+ * @addr: peer's address
+ * @elems: IEs from beacon or mesh peering frame
+ *
+ * Initiates peering if appropriate.
+ */
 void mesh_neighbour_update(struct ieee80211_sub_if_data *sdata,
                            u8 *hw_addr,
                            struct ieee802_11_elems *elems)
 {
         struct sta_info *sta;
 
-        rcu_read_lock();
-        sta = mesh_peer_init(sdata, hw_addr, elems);
+        sta = mesh_sta_info_get(sdata, hw_addr, elems);
         if (!sta)
                 goto out;
 
@@ -632,6 +662,7 @@ void mesh_rx_plink_frame(struct ieee80211_sub_if_data *sdata, struct ieee80211_m
             (ftype == WLAN_SP_MESH_PEERING_CLOSE && ie_len == 8))
                 memcpy(&llid, PLINK_GET_PLID(elems.peering), 2);
 
+        /* WARNING: Only for sta pointer, is dropped & re-acquired */
         rcu_read_lock();
 
         sta = sta_info_get(sdata, mgmt->sa);
@@ -735,8 +766,9 @@ void mesh_rx_plink_frame(struct ieee80211_sub_if_data *sdata, struct ieee80211_m
         }
 
         if (event == OPN_ACPT) {
+                rcu_read_unlock();
                 /* allocate sta entry if necessary and update info */
-                sta = mesh_peer_init(sdata, mgmt->sa, &elems);
+                sta = mesh_sta_info_get(sdata, mgmt->sa, &elems);
                 if (!sta) {
                         mpl_dbg(sdata, "Mesh plink: failed to init peer!\n");
                         rcu_read_unlock();