[NET]: Move destructor from neigh->ops to neigh_params

struct neigh_ops currently has a destructor field, which no in-kernel
drivers outside of infiniband use.  The infiniband/ulp/ipoib in-tree
driver stashes some info in the neighbour structure (the results of
the second-stage lookup from ARP results to real link-level path), and
it uses neigh->ops->destructor to get a callback so it can clean up
this extra info when a neighbour is freed.  We've run into problems
with this: since the destructor is in an ops field that is shared
between neighbours that may belong to different net devices, there's
no way to set/clear it safely.

The following patch moves this field to neigh_parms where it can be
safely set, together with its twin neigh_setup.  Two additional
patches in the patch series update ipoib to use this new interface.

Signed-off-by: Michael S. Tsirkin <mst@mellanox.co.il>
Signed-off-by: Roland Dreier <rolandd@cisco.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

3 files changed, 4 insertions, 18 deletions

diff --git a/drivers/infiniband/ulp/ipoib/ipoib_main.c b/drivers/infiniband/ulp/ipoib/ipoib_main.c
index c3b5f79d1168..9d9cecd4753b 100644
--- a/drivers/infiniband/ulp/ipoib/ipoib_main.c
+++ b/drivers/infiniband/ulp/ipoib/ipoib_main.c
@@ -247,7 +247,6 @@ static void path_free(struct net_device *dev, struct ipoib_path *path)
                 if (neigh->ah)
                         ipoib_put_ah(neigh->ah);
                 *to_ipoib_neigh(neigh->neighbour) = NULL;
-                neigh->neighbour->ops->destructor = NULL;
                 kfree(neigh);
         }
 
@@ -530,7 +529,6 @@ static void neigh_add_path(struct sk_buff *skb, struct net_device *dev)
 err:
         *to_ipoib_neigh(skb->dst->neighbour) = NULL;
         list_del(&neigh->list);
-        neigh->neighbour->ops->destructor = NULL;
         kfree(neigh);
 
         ++priv->stats.tx_dropped;
@@ -769,21 +767,9 @@ static void ipoib_neigh_destructor(struct neighbour *n)
                 ipoib_put_ah(ah);
 }
 
-static int ipoib_neigh_setup(struct neighbour *neigh)
-{
-        /*
-         * Is this kosher?  I can't find anybody in the kernel that
-         * sets neigh->destructor, so we should be able to set it here
-         * without trouble.
-         */
-        neigh->ops->destructor = ipoib_neigh_destructor;
-
-        return 0;
-}
-
 static int ipoib_neigh_setup_dev(struct net_device *dev, struct neigh_parms *parms)
 {
-        parms->neigh_setup = ipoib_neigh_setup;
+        parms->neigh_destructor = ipoib_neigh_destructor;
 
         return 0;
 }
diff --git a/include/net/neighbour.h b/include/net/neighbour.h
index 6fa9ae190741..b0666d66293f 100644
--- a/include/net/neighbour.h
+++ b/include/net/neighbour.h
@@ -68,6 +68,7 @@ struct neigh_parms
         struct net_device *dev;
         struct neigh_parms *next;
         int     (*neigh_setup)(struct neighbour *);
+        void    (*neigh_destructor)(struct neighbour *);
         struct neigh_table *tbl;
 
         void    *sysctl_table;
@@ -145,7 +146,6 @@ struct neighbour
 struct neigh_ops
 {
         int                     family;
-        void                    (*destructor)(struct neighbour *);
         void                    (*solicit)(struct neighbour *, struct sk_buff*);
         void                    (*error_report)(struct neighbour *, struct sk_buff*);
         int                     (*output)(struct sk_buff*);
diff --git a/net/core/neighbour.c b/net/core/neighbour.c
index 6ba1cdea18e8..0c8666872d10 100644
--- a/net/core/neighbour.c
+++ b/net/core/neighbour.c
@@ -586,8 +586,8 @@ void neigh_destroy(struct neighbour *neigh)
                         kfree(hh);
         }
 
-        if (neigh->ops && neigh->ops->destructor)
-                (neigh->ops->destructor)(neigh);
+        if (neigh->parms->neigh_destructor)
+                (neigh->parms->neigh_destructor)(neigh);
 
         skb_queue_purge(&neigh->arp_queue);