From: Alexander Duyck Date: Wed, 31 Dec 2014 10:56:49 -0800 Subject: [PATCH] fib_trie: Push tnode flushing down to inflate/halve This change pushes the tnode freeing down into the inflate and halve functions. It makes more sense here as we have a better grasp of what is going on and when a given cluster of nodes is ready to be freed. I believe this may address a bug in the freeing logic as well. For some reason if the freelist got to a certain size we would call synchronize_rcu(). I'm assuming that what they meant to do is call synchronize_rcu() after they had handed off that much memory via call_rcu(). As such that is what I have updated the behavior to be. Signed-off-by: Alexander Duyck Signed-off-by: David S. Miller --- --- a/net/ipv4/fib_trie.c +++ b/net/ipv4/fib_trie.c @@ -147,8 +147,6 @@ struct trie { }; static void resize(struct trie *t, struct tnode *tn); -/* tnodes to free after resize(); protected by RTNL */ -static struct callback_head *tnode_free_head; static size_t tnode_free_size; /* @@ -307,32 +305,6 @@ static struct tnode *tnode_alloc(size_t return vzalloc(size); } -static void tnode_free_safe(struct tnode *tn) -{ - BUG_ON(IS_LEAF(tn)); - tn->rcu.next = tnode_free_head; - tnode_free_head = &tn->rcu; -} - -static void tnode_free_flush(void) -{ - struct callback_head *head; - - while ((head = tnode_free_head)) { - struct tnode *tn = container_of(head, struct tnode, rcu); - - tnode_free_head = head->next; - tnode_free_size += offsetof(struct tnode, child[1 << tn->bits]); - - node_free(tn); - } - - if (tnode_free_size >= PAGE_SIZE * sync_pages) { - tnode_free_size = 0; - synchronize_rcu(); - } -} - static struct tnode *leaf_new(t_key key) { struct tnode *l = kmem_cache_alloc(trie_leaf_kmem, GFP_KERNEL); @@ -433,17 +405,33 @@ static void put_child_root(struct tnode rcu_assign_pointer(t->trie, n); } -static void tnode_clean_free(struct tnode *tn) +static inline void tnode_free_init(struct tnode *tn) { - struct tnode *tofree; - unsigned long i; + tn->rcu.next = NULL; +} + +static inline void tnode_free_append(struct tnode *tn, struct tnode *n) +{ + n->rcu.next = tn->rcu.next; + tn->rcu.next = &n->rcu; +} - for (i = 0; i < tnode_child_length(tn); i++) { - tofree = tnode_get_child(tn, i); - if (tofree) - node_free(tofree); +static void tnode_free(struct tnode *tn) +{ + struct callback_head *head = &tn->rcu; + + while (head) { + head = head->next; + tnode_free_size += offsetof(struct tnode, child[1 << tn->bits]); + node_free(tn); + + tn = container_of(head, struct tnode, rcu); + } + + if (tnode_free_size >= PAGE_SIZE * sync_pages) { + tnode_free_size = 0; + synchronize_rcu(); } - node_free(tn); } static int inflate(struct trie *t, struct tnode *oldtnode) @@ -476,20 +464,23 @@ static int inflate(struct trie *t, struc inode->bits - 1); if (!left) goto nomem; + tnode_free_append(tn, left); right = tnode_new(inode->key | m, inode->pos, inode->bits - 1); - if (!right) { - node_free(left); + if (!right) goto nomem; - } + tnode_free_append(tn, right); put_child(tn, 2*i, left); put_child(tn, 2*i+1, right); } } + /* prepare oldtnode to be freed */ + tnode_free_init(oldtnode); + for (i = 0; i < olen; i++) { struct tnode *inode = tnode_get_child(oldtnode, i); struct tnode *left, *right; @@ -505,12 +496,13 @@ static int inflate(struct trie *t, struc continue; } + /* drop the node in the old tnode free list */ + tnode_free_append(oldtnode, inode); + /* An internal node with two children */ if (inode->bits == 1) { put_child(tn, 2*i, rtnl_dereference(inode->child[0])); put_child(tn, 2*i+1, rtnl_dereference(inode->child[1])); - - tnode_free_safe(inode); continue; } @@ -556,17 +548,19 @@ static int inflate(struct trie *t, struc put_child(tn, 2 * i, left); put_child(tn, 2 * i + 1, right); - tnode_free_safe(inode); - + /* resize child nodes */ resize(t, left); resize(t, right); } put_child_root(tp, t, tn->key, tn); - tnode_free_safe(oldtnode); + + /* we completed without error, prepare to free old node */ + tnode_free(oldtnode); return 0; nomem: - tnode_clean_free(tn); + /* all pointers should be clean so we are done */ + tnode_free(tn); return -ENOMEM; } @@ -599,17 +593,20 @@ static int halve(struct trie *t, struct struct tnode *newn; newn = tnode_new(left->key, oldtnode->pos, 1); - if (!newn) { - tnode_clean_free(tn); + tnode_free(tn); return -ENOMEM; } + tnode_free_append(tn, newn); put_child(tn, i/2, newn); } } + /* prepare oldtnode to be freed */ + tnode_free_init(oldtnode); + for (i = 0; i < olen; i += 2) { struct tnode *newBinNode; @@ -636,11 +633,14 @@ static int halve(struct trie *t, struct put_child(tn, i / 2, newBinNode); + /* resize child node */ resize(t, newBinNode); } put_child_root(tp, t, tn->key, tn); - tnode_free_safe(oldtnode); + + /* all pointers should be clean so we are done */ + tnode_free(oldtnode); return 0; } @@ -798,7 +798,8 @@ no_children: node_set_parent(n, tp); /* drop dead node */ - tnode_free_safe(tn); + tnode_free_init(tn); + tnode_free(tn); } } @@ -884,16 +885,12 @@ static void trie_rebalance(struct trie * while ((tp = node_parent(tn)) != NULL) { resize(t, tn); - - tnode_free_flush(); tn = tp; } /* Handle last (top) tnode */ if (IS_TNODE(tn)) resize(t, tn); - - tnode_free_flush(); } /* only used from updater-side */