fib_trie: Various clean-ups for handling slen

While doing further work on the fib_trie I noted a few items.

First I was using calls that were far more complicated than they needed to
be for determining when to push/pull the suffix length.  I have updated the
code to reflect the simplier logic.

The second issue is that I realised we weren't necessarily handling the
case of a leaf_info struct surviving a flush.  I have updated the logic so
that now we will call pull_suffix in the event of having a leaf info value
left in the leaf after flushing it.

Signed-off-by: Alexander Duyck <alexander.h.duyck@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/ipv4/fib_trie.c b/net/ipv4/fib_trie.c
index 7f342265968e8244603c69d921e5904ee3e8ce4d..3daf0224ff2e1821ce9c258a48db1c3d20437657 100644 (file)
--- a/net/ipv4/fib_trie.c
+++ b/net/ipv4/fib_trie.c
@@ -917,27 +917,20 @@ static void leaf_push_suffix(struct tnode *l)
 
 static void remove_leaf_info(struct tnode *l, struct leaf_info *old)
 {
-       struct hlist_node *prev;
-
-       /* record the location of the pointer to this object */
-       prev = rtnl_dereference(hlist_pprev_rcu(&old->hlist));
+       /* record the location of the previous list_info entry */
+       struct hlist_node **pprev = old->hlist.pprev;
+       struct leaf_info *li = hlist_entry(pprev, typeof(*li), hlist.next);
 
        /* remove the leaf info from the list */
        hlist_del_rcu(&old->hlist);
 
-       /* if we emptied the list this leaf will be freed and we can sort
-        * out parent suffix lengths as a part of trie_rebalance
-        */
-       if (hlist_empty(&l->list))
+       /* only access li if it is pointing at the last valid hlist_node */
+       if (hlist_empty(&l->list) || (*pprev))
                return;
 
-       /* if we removed the tail then we need to update slen */
-       if (!rcu_access_pointer(hlist_next_rcu(prev))) {
-               struct leaf_info *li = hlist_entry(prev, typeof(*li), hlist);
-
-               l->slen = KEYLENGTH - li->plen;
-               leaf_pull_suffix(l);
-       }
+       /* update the trie with the latest suffix length */
+       l->slen = KEYLENGTH - li->plen;
+       leaf_pull_suffix(l);
 }
 
 static void insert_leaf_info(struct tnode *l, struct leaf_info *new)
@@ -961,7 +954,7 @@ static void insert_leaf_info(struct tnode *l, struct leaf_info *new)
        }
 
        /* if we added to the tail node then we need to update slen */
-       if (!rcu_access_pointer(hlist_next_rcu(&new->hlist))) {
+       if (l->slen < (KEYLENGTH - new->plen)) {
                l->slen = KEYLENGTH - new->plen;
                leaf_push_suffix(l);
        }
@@ -1613,6 +1606,7 @@ static int trie_flush_leaf(struct tnode *l)
        struct hlist_head *lih = &l->list;
        struct hlist_node *tmp;
        struct leaf_info *li = NULL;
+       unsigned char plen = KEYLENGTH;
 
        hlist_for_each_entry_safe(li, tmp, lih, hlist) {
                found += trie_flush_list(&li->falh);
@@ -1620,8 +1614,14 @@ static int trie_flush_leaf(struct tnode *l)
                if (list_empty(&li->falh)) {
                        hlist_del_rcu(&li->hlist);
                        free_leaf_info(li);
+                       continue;
                }
+
+               plen = li->plen;
        }
+
+       l->slen = KEYLENGTH - plen;
+
        return found;
 }
 
@@ -1700,13 +1700,22 @@ int fib_table_flush(struct fib_table *tb)
        for (l = trie_firstleaf(t); l; l = trie_nextleaf(l)) {
                found += trie_flush_leaf(l);
 
-               if (ll && hlist_empty(&ll->list))
-                       trie_leaf_remove(t, ll);
+               if (ll) {
+                       if (hlist_empty(&ll->list))
+                               trie_leaf_remove(t, ll);
+                       else
+                               leaf_pull_suffix(ll);
+               }
+
                ll = l;
        }
 
-       if (ll && hlist_empty(&ll->list))
-               trie_leaf_remove(t, ll);
+       if (ll) {
+               if (hlist_empty(&ll->list))
+                       trie_leaf_remove(t, ll);
+               else
+                       leaf_pull_suffix(ll);
+       }
 
        pr_debug("trie_flush found=%d\n", found);
        return found;