IPoIB: Fix address handle refcounting for multicast groups

Multiple ipoib_neigh structures on mcast->neigh_list may point to the
same ah.  This means that ipoib_mcast_free() can't just make a list of
ah structs to free, since this might end up trying to add the same ah
to the list more than once.  Handle this in ipoib_multicast.c in the
same way as it is handled in ipoib_main.c for struct ipoib_path.

Signed-off-by: Eli Cohen <eli@mellanox.co.il>
Signed-off-by: Michael S. Tsirkin <mst@mellanox.co.il>
Signed-off-by: Roland Dreier <rolandd@cisco.com>

1 files changed, 7 insertions, 6 deletions

diff --git a/drivers/infiniband/ulp/ipoib/ipoib_multicast.c b/drivers/infiniband/ulp/ipoib/ipoib_multicast.c
index 6c6db759e79e..03b2ca64a40c 100644
--- a/drivers/infiniband/ulp/ipoib/ipoib_multicast.c
+++ b/drivers/infiniband/ulp/ipoib/ipoib_multicast.c
@@ -97,8 +97,6 @@ static void ipoib_mcast_free(struct ipoib_mcast *mcast)
         struct ipoib_dev_priv *priv = netdev_priv(dev);
         struct ipoib_neigh *neigh, *tmp;
         unsigned long flags;
-        LIST_HEAD(ah_list);
-        struct ipoib_ah *ah, *tah;
 
         ipoib_dbg_mcast(netdev_priv(dev),
                         "deleting multicast group " IPOIB_GID_FMT "\n",
@@ -107,8 +105,14 @@ static void ipoib_mcast_free(struct ipoib_mcast *mcast)
         spin_lock_irqsave(&priv->lock, flags);
 
         list_for_each_entry_safe(neigh, tmp, &mcast->neigh_list, list) {
+                /*
+                 * It's safe to call ipoib_put_ah() inside priv->lock
+                 * here, because we know that mcast->ah will always
+                 * hold one more reference, so ipoib_put_ah() will
+                 * never do more than decrement the ref count.
+                 */
                 if (neigh->ah)
-                        list_add_tail(&neigh->ah->list, &ah_list);
+                        ipoib_put_ah(neigh->ah);
                 *to_ipoib_neigh(neigh->neighbour) = NULL;
                 neigh->neighbour->ops->destructor = NULL;
                 kfree(neigh);
@@ -116,9 +120,6 @@ static void ipoib_mcast_free(struct ipoib_mcast *mcast)
 
         spin_unlock_irqrestore(&priv->lock, flags);
 
-        list_for_each_entry_safe(ah, tah, &ah_list, list)
-                ipoib_put_ah(ah);
-
         if (mcast->ah)
                 ipoib_put_ah(mcast->ah);