fib_trie: Remove checks for index >= tnode_child_length from tnode_get_child

For some reason the compiler doesn't seem to understand that when we are in
a loop that runs from tnode_child_length - 1 to 0 we don't expect the value
of tn->bits to change.  As such every call to tnode_get_child was rerunning
tnode_chile_length which ended up consuming quite a bit of space in the
resultant assembly code.

I have gone though and verified that in all cases where tnode_get_child
is used we are either winding though a fixed loop from tnode_child_length -
1 to 0, or are in a fastpath case where we are verifying the value by
either checking for any remaining bits after shifting index by bits and
testing for leaf, or by using tnode_child_length.

size net/ipv4/fib_trie.o
Before:
   text	   data	    bss	    dec	    hex	filename
  15506	    376	      8	  15890	   3e12	net/ipv4/fib_trie.o

After:
   text	   data	    bss	    dec	    hex	filename
  14827	    376	      8	  15211	   3b6b	net/ipv4/fib_trie.o

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 0c88df09d25d3d4e5bea877bdcf586cfc32a6c83..87fc9a466fa21c718722de1c189c289049d7be48 100644 (file)
--- a/net/ipv4/fib_trie.c
+++ b/net/ipv4/fib_trie.c
@@ -186,8 +186,6 @@ static inline unsigned long tnode_child_length(const struct tnode *tn)
 static inline struct tnode *tnode_get_child(const struct tnode *tn,
                                            unsigned long i)
 {
-       BUG_ON(i >= tnode_child_length(tn));
-
        return rtnl_dereference(tn->child[i]);
 }
 
@@ -195,8 +193,6 @@ static inline struct tnode *tnode_get_child(const struct tnode *tn,
 static inline struct tnode *tnode_get_child_rcu(const struct tnode *tn,
                                                unsigned long i)
 {
-       BUG_ON(i >= tnode_child_length(tn));
-
        return rcu_dereference_rtnl(tn->child[i]);
 }
 
@@ -371,7 +367,7 @@ static inline int tnode_full(const struct tnode *tn, const struct tnode *n)
  */
 static void put_child(struct tnode *tn, unsigned long i, struct tnode *n)
 {
-       struct tnode *chi = rtnl_dereference(tn->child[i]);
+       struct tnode *chi = tnode_get_child(tn, i);
        int isfull, wasfull;
 
        BUG_ON(i >= tnode_child_length(tn));
@@ -867,7 +863,7 @@ static struct tnode *fib_find_node(struct trie *t, u32 key)
                if (IS_LEAF(n))
                        break;
 
-               n = rcu_dereference_rtnl(n->child[index]);
+               n = tnode_get_child_rcu(n, index);
        }
 
        return n;
@@ -934,7 +930,7 @@ static struct list_head *fib_insert_node(struct trie *t, u32 key, int plen)
                }
 
                tp = n;
-               n = rcu_dereference_rtnl(n->child[index]);
+               n = tnode_get_child_rcu(n, index);
        }
 
        l = leaf_new(key);
@@ -1215,7 +1211,7 @@ int fib_table_lookup(struct fib_table *tb, const struct flowi4 *flp,
                        cindex = index;
                }
 
-               n = rcu_dereference(n->child[index]);
+               n = tnode_get_child_rcu(n, index);
                if (unlikely(!n))
                        goto backtrace;
        }
@@ -1835,7 +1831,7 @@ static void trie_collect_stats(struct trie *t, struct trie_stat *s)
                        if (n->bits < MAX_STAT_DEPTH)
                                s->nodesizes[n->bits]++;
 
-                       for (i = 0; i < tnode_child_length(n); i++) {
+                       for (i = tnode_child_length(n); i--;) {
                                if (!rcu_access_pointer(n->child[i]))
                                        s->nullpointers++;
                        }