--- /dev/null
+From: Alexander Duyck <alexander.h.duyck@redhat.com>
+Date: Thu, 22 Jan 2015 15:51:26 -0800
+Subject: [PATCH] fib_trie: Add collapse() and should_collapse() to resize
+
+This patch really does two things.
+
+First it pulls the logic for determining if we should collapse one node out
+of the tree and the actual code doing the collapse into a separate pair of
+functions. This helps to make the changes to these areas more readable.
+
+Second it encodes the upper 32b of the empty_children value onto the
+full_children value in the case of bits == KEYLENGTH. By doing this we are
+able to handle the case of a 32b node where empty_children would appear to
+be 0 when it was actually 1ul << 32.
+
+Signed-off-by: Alexander Duyck <alexander.h.duyck@redhat.com>
+Signed-off-by: David S. Miller <davem@davemloft.net>
+---
+
+--- a/net/ipv4/fib_trie.c
++++ b/net/ipv4/fib_trie.c
+@@ -83,7 +83,8 @@
+
+ #define MAX_STAT_DEPTH 32
+
+-#define KEYLENGTH (8*sizeof(t_key))
++#define KEYLENGTH (8*sizeof(t_key))
++#define KEY_MAX ((t_key)~0)
+
+ typedef unsigned int t_key;
+
+@@ -102,8 +103,8 @@ struct tnode {
+ union {
+ /* The fields in this struct are valid if bits > 0 (TNODE) */
+ struct {
+- unsigned int full_children; /* KEYLENGTH bits needed */
+- unsigned int empty_children; /* KEYLENGTH bits needed */
++ t_key empty_children; /* KEYLENGTH bits needed */
++ t_key full_children; /* KEYLENGTH bits needed */
+ struct tnode __rcu *child[0];
+ };
+ /* This list pointer if valid if bits == 0 (LEAF) */
+@@ -302,6 +303,16 @@ static struct tnode *tnode_alloc(size_t
+ return vzalloc(size);
+ }
+
++static inline void empty_child_inc(struct tnode *n)
++{
++ ++n->empty_children ? : ++n->full_children;
++}
++
++static inline void empty_child_dec(struct tnode *n)
++{
++ n->empty_children-- ? : n->full_children--;
++}
++
+ static struct tnode *leaf_new(t_key key)
+ {
+ struct tnode *l = kmem_cache_alloc(trie_leaf_kmem, GFP_KERNEL);
+@@ -335,7 +346,7 @@ static struct leaf_info *leaf_info_new(i
+
+ static struct tnode *tnode_new(t_key key, int pos, int bits)
+ {
+- size_t sz = offsetof(struct tnode, child[1 << bits]);
++ size_t sz = offsetof(struct tnode, child[1ul << bits]);
+ struct tnode *tn = tnode_alloc(sz);
+ unsigned int shift = pos + bits;
+
+@@ -348,8 +359,10 @@ static struct tnode *tnode_new(t_key key
+ tn->pos = pos;
+ tn->bits = bits;
+ tn->key = (shift < KEYLENGTH) ? (key >> shift) << shift : 0;
+- tn->full_children = 0;
+- tn->empty_children = 1<<bits;
++ if (bits == KEYLENGTH)
++ tn->full_children = 1;
++ else
++ tn->empty_children = 1ul << bits;
+ }
+
+ pr_debug("AT %p s=%zu %zu\n", tn, sizeof(struct tnode),
+@@ -375,11 +388,11 @@ static void put_child(struct tnode *tn,
+
+ BUG_ON(i >= tnode_child_length(tn));
+
+- /* update emptyChildren */
++ /* update emptyChildren, overflow into fullChildren */
+ if (n == NULL && chi != NULL)
+- tn->empty_children++;
+- else if (n != NULL && chi == NULL)
+- tn->empty_children--;
++ empty_child_inc(tn);
++ if (n != NULL && chi == NULL)
++ empty_child_dec(tn);
+
+ /* update fullChildren */
+ wasfull = tnode_full(tn, chi);
+@@ -630,6 +643,24 @@ static int halve(struct trie *t, struct
+ return 0;
+ }
+
++static void collapse(struct trie *t, struct tnode *oldtnode)
++{
++ struct tnode *n, *tp;
++ unsigned long i;
++
++ /* scan the tnode looking for that one child that might still exist */
++ for (n = NULL, i = tnode_child_length(oldtnode); !n && i;)
++ n = tnode_get_child(oldtnode, --i);
++
++ /* compress one level */
++ tp = node_parent(oldtnode);
++ put_child_root(tp, t, oldtnode->key, n);
++ node_set_parent(n, tp);
++
++ /* drop dead node */
++ node_free(oldtnode);
++}
++
+ static unsigned char update_suffix(struct tnode *tn)
+ {
+ unsigned char slen = tn->pos;
+@@ -729,10 +760,12 @@ static bool should_inflate(const struct
+
+ /* Keep root node larger */
+ threshold *= tp ? inflate_threshold : inflate_threshold_root;
+- used += tn->full_children;
+ used -= tn->empty_children;
++ used += tn->full_children;
+
+- return tn->pos && ((50 * used) >= threshold);
++ /* if bits == KEYLENGTH then pos = 0, and will fail below */
++
++ return (used > 1) && tn->pos && ((50 * used) >= threshold);
+ }
+
+ static bool should_halve(const struct tnode *tp, const struct tnode *tn)
+@@ -744,13 +777,29 @@ static bool should_halve(const struct tn
+ threshold *= tp ? halve_threshold : halve_threshold_root;
+ used -= tn->empty_children;
+
+- return (tn->bits > 1) && ((100 * used) < threshold);
++ /* if bits == KEYLENGTH then used = 100% on wrap, and will fail below */
++
++ return (used > 1) && (tn->bits > 1) && ((100 * used) < threshold);
++}
++
++static bool should_collapse(const struct tnode *tn)
++{
++ unsigned long used = tnode_child_length(tn);
++
++ used -= tn->empty_children;
++
++ /* account for bits == KEYLENGTH case */
++ if ((tn->bits == KEYLENGTH) && tn->full_children)
++ used -= KEY_MAX;
++
++ /* One child or none, time to drop us from the trie */
++ return used < 2;
+ }
+
+ #define MAX_WORK 10
+ static void resize(struct trie *t, struct tnode *tn)
+ {
+- struct tnode *tp = node_parent(tn), *n = NULL;
++ struct tnode *tp = node_parent(tn);
+ struct tnode __rcu **cptr;
+ int max_work = MAX_WORK;
+
+@@ -764,14 +813,6 @@ static void resize(struct trie *t, struc
+ cptr = tp ? &tp->child[get_index(tn->key, tp)] : &t->trie;
+ BUG_ON(tn != rtnl_dereference(*cptr));
+
+- /* No children */
+- if (tn->empty_children > (tnode_child_length(tn) - 1))
+- goto no_children;
+-
+- /* One child */
+- if (tn->empty_children == (tnode_child_length(tn) - 1))
+- goto one_child;
+-
+ /* Double as long as the resulting node has a number of
+ * nonempty nodes that are above the threshold.
+ */
+@@ -807,19 +848,8 @@ static void resize(struct trie *t, struc
+ }
+
+ /* Only one child remains */
+- if (tn->empty_children == (tnode_child_length(tn) - 1)) {
+- unsigned long i;
+-one_child:
+- for (i = tnode_child_length(tn); !n && i;)
+- n = tnode_get_child(tn, --i);
+-no_children:
+- /* compress one level */
+- put_child_root(tp, t, tn->key, n);
+- node_set_parent(n, tp);
+-
+- /* drop dead node */
+- tnode_free_init(tn);
+- tnode_free(tn);
++ if (should_collapse(tn)) {
++ collapse(t, tn);
+ return;
+ }
+
projects / openwrt / staging / chunkeey.git / blobdiff