mac80211: allow station add/remove to sleep

Many drivers would like to sleep during station
addition and removal, and currently have a high
complexity there from not being able to.

This introduces two new callbacks sta_add() and
sta_remove() that drivers can implement instead
of using sta_notify() and that can sleep, and
the new sta_add() callback is also allowed to
fail.

The reason we didn't do this previously is that
the IBSS code wants to insert stations from the
RX path, which is a tasklet, so cannot sleep.
This patch will keep the station allocation in
that path, but moves adding the station to the
driver out of line. Since the addition can now
fail, we can have IBSS peer structs the driver
rejected -- in that case we still talk to the
station but never tell the driver about it in
the control.sta pointer. If there will ever be
a driver that has a low limit on the number of
stations and that cannot talk to any stations
that are not known to it, we need to do come up
with a new strategy of handling larger IBSSs,
maybe quicker expiry or rejecting peers.

Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

1 files changed, 13 insertions, 9 deletions

diff --git a/net/mac80211/ibss.c b/net/mac80211/ibss.c
index 85c4ba14c77..f3e94248674 100644
--- a/net/mac80211/ibss.c
+++ b/net/mac80211/ibss.c
@@ -275,10 +275,12 @@ static void ieee80211_rx_bss_info(struct ieee80211_sub_if_data *sdata,
 				    (unsigned long long) supp_rates,
 				    (unsigned long long) sta->sta.supp_rates[band]);
 #endif
-		} else
-			ieee80211_ibss_add_sta(sdata, mgmt->bssid, mgmt->sa, supp_rates);
-
-		rcu_read_unlock();
+			rcu_read_unlock();
+		} else {
+			rcu_read_unlock();
+			ieee80211_ibss_add_sta(sdata, mgmt->bssid, mgmt->sa,
+					       supp_rates, GFP_KERNEL);
+		}
 	}
 
 	bss = ieee80211_bss_info_update(local, rx_status, mgmt, len, elems,
@@ -368,7 +370,8 @@ static void ieee80211_rx_bss_info(struct ieee80211_sub_if_data *sdata,
 		       sdata->name, mgmt->bssid);
 #endif
 		ieee80211_sta_join_ibss(sdata, bss);
-		ieee80211_ibss_add_sta(sdata, mgmt->bssid, mgmt->sa, supp_rates);
+		ieee80211_ibss_add_sta(sdata, mgmt->bssid, mgmt->sa,
+				       supp_rates, GFP_KERNEL);
 	}
 
  put_bss:
@@ -381,7 +384,8 @@ static void ieee80211_rx_bss_info(struct ieee80211_sub_if_data *sdata,
  * must be callable in atomic context.
  */
 struct sta_info *ieee80211_ibss_add_sta(struct ieee80211_sub_if_data *sdata,
-					u8 *bssid,u8 *addr, u32 supp_rates)
+					u8 *bssid,u8 *addr, u32 supp_rates,
+					gfp_t gfp)
 {
 	struct ieee80211_if_ibss *ifibss = &sdata->u.ibss;
 	struct ieee80211_local *local = sdata->local;
@@ -410,7 +414,7 @@ struct sta_info *ieee80211_ibss_add_sta(struct ieee80211_sub_if_data *sdata,
 	       wiphy_name(local->hw.wiphy), addr, sdata->name);
 #endif
 
-	sta = sta_info_alloc(sdata, addr, GFP_ATOMIC);
+	sta = sta_info_alloc(sdata, addr, gfp);
 	if (!sta)
 		return NULL;
 
@@ -422,9 +426,9 @@ struct sta_info *ieee80211_ibss_add_sta(struct ieee80211_sub_if_data *sdata,
 
 	rate_control_rate_init(sta);
 
+	/* If it fails, maybe we raced another insertion? */
 	if (sta_info_insert(sta))
-		return NULL;
-
+		return sta_info_get(sdata, addr);
 	return sta;
 }