inetpeer: remove AVL implementation in favor of RB tree (b145425f) · Commits · 戴 / test

include/net/inetpeer.h

+2 −9

Original line number	Diff line number	Diff line
		@@ -33,18 +33,12 @@ struct inetpeer_addr {
		};

		struct inet_peer {
		/* group together avl_left,avl_right,v4daddr to speedup lookups */
		struct inet_peer __rcu avl_left, avl_right;
		struct rb_node rb_node;
		struct inetpeer_addr daddr;
		__u32 avl_height;

		u32 metrics[RTAX_MAX];
		u32 rate_tokens; /* rate limiting for ICMP */
		unsigned long rate_last;
		union {
		struct list_head gc_list;
		struct rcu_head gc_rcu;
		};
		/*
		* Once inet_peer is queued for deletion (refcnt == 0), following field
		* is not available: rid
		@@ -55,7 +49,6 @@ struct inet_peer {
		atomic_t rid; /* Frag reception counter */
		};
		struct rcu_head rcu;
		struct inet_peer *gc_next;
		};

		/* following fields might be frequently dirtied */
		@@ -64,7 +57,7 @@ struct inet_peer {
		};

		struct inet_peer_base {
		struct inet_peer __rcu *root;
		struct rb_root rb_root;
		seqlock_t lock;
		int total;
		};

net/ipv4/inetpeer.c

+90 −338

Original line number	Diff line number	Diff line
		@@ -33,7 +33,7 @@
		* also be removed if the pool is overloaded i.e. if the total amount of
		* entries is greater-or-equal than the threshold.
		*
		* Node pool is organised as an AVL tree.
		* Node pool is organised as an RB tree.
		* Such an implementation has been chosen not just for fun. It's a way to
		* prevent easy and efficient DoS attacks by creating hash collisions. A huge
		* amount of long living nodes in a single hash slot would significantly delay
		@@ -45,7 +45,7 @@
		* AND reference count being 0.
		* 3. Global variable peer_total is modified under the pool lock.
		* 4. struct inet_peer fields modification:
		* avl_left, avl_right, avl_parent, avl_height: pool lock
		* rb_node: pool lock
		* refcnt: atomically against modifications on other CPU;
		* usually under some other lock to prevent node disappearing
		* daddr: unchangeable
		@@ -53,30 +53,15 @@

		static struct kmem_cache *peer_cachep __read_mostly;

		static LIST_HEAD(gc_list);
		static const int gc_delay = 60 * HZ;
		static struct delayed_work gc_work;
		static DEFINE_SPINLOCK(gc_lock);

		#define node_height(x) x->avl_height

		#define peer_avl_empty ((struct inet_peer *)&peer_fake_node)
		#define peer_avl_empty_rcu ((struct inet_peer __rcu __force *)&peer_fake_node)
		static const struct inet_peer peer_fake_node = {
		.avl_left = peer_avl_empty_rcu,
		.avl_right = peer_avl_empty_rcu,
		.avl_height = 0
		};

		void inet_peer_base_init(struct inet_peer_base *bp)
		{
		bp->root = peer_avl_empty_rcu;
		bp->rb_root = RB_ROOT;
		seqlock_init(&bp->lock);
		bp->total = 0;
		}
		EXPORT_SYMBOL_GPL(inet_peer_base_init);

		#define PEER_MAXDEPTH 40 /* sufficient for about 2^27 nodes */
		#define PEER_MAX_GC 32

		/* Exported for sysctl_net_ipv4. */
		int inet_peer_threshold __read_mostly = 65536 + 128; /* start to throw entries more
		@@ -84,53 +69,6 @@ int inet_peer_threshold __read_mostly = 65536 + 128; /* start to throw entries m
		int inet_peer_minttl __read_mostly = 120 * HZ; /* TTL under high load: 120 sec */
		int inet_peer_maxttl __read_mostly = 10 * 60 * HZ; /* usual time to live: 10 min */

		static void inetpeer_gc_worker(struct work_struct *work)
		{
		struct inet_peer p, n, *c;
		struct list_head list;

		spin_lock_bh(&gc_lock);
		list_replace_init(&gc_list, &list);
		spin_unlock_bh(&gc_lock);

		if (list_empty(&list))
		return;

		list_for_each_entry_safe(p, n, &list, gc_list) {

		if (need_resched())
		cond_resched();

		c = rcu_dereference_protected(p->avl_left, 1);
		if (c != peer_avl_empty) {
		list_add_tail(&c->gc_list, &list);
		p->avl_left = peer_avl_empty_rcu;
		}

		c = rcu_dereference_protected(p->avl_right, 1);
		if (c != peer_avl_empty) {
		list_add_tail(&c->gc_list, &list);
		p->avl_right = peer_avl_empty_rcu;
		}

		n = list_entry(p->gc_list.next, struct inet_peer, gc_list);

		if (refcount_read(&p->refcnt) == 1) {
		list_del(&p->gc_list);
		kmem_cache_free(peer_cachep, p);
		}
		}

		if (list_empty(&list))
		return;

		spin_lock_bh(&gc_lock);
		list_splice(&list, &gc_list);
		spin_unlock_bh(&gc_lock);

		schedule_delayed_work(&gc_work, gc_delay);
		}

		/* Called from ip_output.c:ip_init */
		void __init inet_initpeers(void)
		{
		@@ -153,225 +91,62 @@ void __init inet_initpeers(void)
		sizeof(struct inet_peer),
		0, SLAB_HWCACHE_ALIGN \| SLAB_PANIC,
		NULL);

		INIT_DEFERRABLE_WORK(&gc_work, inetpeer_gc_worker);
		}

		#define rcu_deref_locked(X, BASE) \
		rcu_dereference_protected(X, lockdep_is_held(&(BASE)->lock.lock))

		/*
		* Called with local BH disabled and the pool lock held.
		*/
		#define lookup(_daddr, _stack, _base) \
		({ \
		struct inet_peer *u; \
		struct inet_peer __rcu **v; \
		\
		stackptr = _stack; \
		*stackptr++ = &_base->root; \
		for (u = rcu_deref_locked(_base->root, _base); \
		u != peer_avl_empty;) { \
		int cmp = inetpeer_addr_cmp(_daddr, &u->daddr); \
		if (cmp == 0) \
		break; \
		if (cmp == -1) \
		v = &u->avl_left; \
		else \
		v = &u->avl_right; \
		*stackptr++ = v; \
		u = rcu_deref_locked(*v, _base); \
		} \
		u; \
		})

		/*
		* Called with rcu_read_lock()
		* Because we hold no lock against a writer, its quite possible we fall
		* in an endless loop.
		* But every pointer we follow is guaranteed to be valid thanks to RCU.
		* We exit from this function if number of links exceeds PEER_MAXDEPTH
		*/
		static struct inet_peer lookup_rcu(const struct inetpeer_addr daddr,
		struct inet_peer_base *base)
		/* Called with rcu_read_lock() or base->lock held */
		static struct inet_peer lookup(const struct inetpeer_addr daddr,
		struct inet_peer_base *base,
		unsigned int seq,
		struct inet_peer *gc_stack[],
		unsigned int *gc_cnt,
		struct rb_node **parent_p,
		struct rb_node ***pp_p)
		{
		struct inet_peer *u = rcu_dereference(base->root);
		int count = 0;
		struct rb_node *pp, parent;
		struct inet_peer *p;

		while (u != peer_avl_empty) {
		int cmp = inetpeer_addr_cmp(daddr, &u->daddr);
		pp = &base->rb_root.rb_node;
		parent = NULL;
		while (*pp) {
		int cmp;

		parent = rcu_dereference_raw(*pp);
		p = rb_entry(parent, struct inet_peer, rb_node);
		cmp = inetpeer_addr_cmp(daddr, &p->daddr);
		if (cmp == 0) {
		/* Before taking a reference, check if this entry was
		* deleted (refcnt=0)
		*/
		if (!refcount_inc_not_zero(&u->refcnt)) {
		u = NULL;
		if (!refcount_inc_not_zero(&p->refcnt))
		break;
		return p;
		}
		return u;
		if (gc_stack) {
		if (*gc_cnt < PEER_MAX_GC)
		gc_stack[(*gc_cnt)++] = p;
		} else if (unlikely(read_seqretry(&base->lock, seq))) {
		break;
		}
		if (cmp == -1)
		u = rcu_dereference(u->avl_left);
		pp = &(*pp)->rb_left;
		else
		u = rcu_dereference(u->avl_right);
		if (unlikely(++count == PEER_MAXDEPTH))
		break;
		pp = &(*pp)->rb_right;
		}
		*parent_p = parent;
		*pp_p = pp;
		return NULL;
		}

		/* Called with local BH disabled and the pool lock held. */
		#define lookup_rightempty(start, base) \
		({ \
		struct inet_peer *u; \
		struct inet_peer __rcu **v; \
		*stackptr++ = &start->avl_left; \
		v = &start->avl_left; \
		for (u = rcu_deref_locked(*v, base); \
		u->avl_right != peer_avl_empty_rcu;) { \
		v = &u->avl_right; \
		*stackptr++ = v; \
		u = rcu_deref_locked(*v, base); \
		} \
		u; \
		})

		/* Called with local BH disabled and the pool lock held.
		* Variable names are the proof of operation correctness.
		* Look into mm/map_avl.c for more detail description of the ideas.
		*/
		static void peer_avl_rebalance(struct inet_peer __rcu **stack[],
		struct inet_peer __rcu ***stackend,
		struct inet_peer_base *base)
		{
		struct inet_peer __rcu **nodep;
		struct inet_peer node, l, *r;
		int lh, rh;

		while (stackend > stack) {
		nodep = *--stackend;
		node = rcu_deref_locked(*nodep, base);
		l = rcu_deref_locked(node->avl_left, base);
		r = rcu_deref_locked(node->avl_right, base);
		lh = node_height(l);
		rh = node_height(r);
		if (lh > rh + 1) { /* l: RH+2 */
		struct inet_peer ll, lr, lrl, lrr;
		int lrh;
		ll = rcu_deref_locked(l->avl_left, base);
		lr = rcu_deref_locked(l->avl_right, base);
		lrh = node_height(lr);
		if (lrh <= node_height(ll)) { /* ll: RH+1 */
		RCU_INIT_POINTER(node->avl_left, lr); /* lr: RH or RH+1 */
		RCU_INIT_POINTER(node->avl_right, r); /* r: RH */
		node->avl_height = lrh + 1; /* RH+1 or RH+2 */
		RCU_INIT_POINTER(l->avl_left, ll); /* ll: RH+1 */
		RCU_INIT_POINTER(l->avl_right, node); /* node: RH+1 or RH+2 */
		l->avl_height = node->avl_height + 1;
		RCU_INIT_POINTER(*nodep, l);
		} else { /* ll: RH, lr: RH+1 */
		lrl = rcu_deref_locked(lr->avl_left, base);/* lrl: RH or RH-1 */
		lrr = rcu_deref_locked(lr->avl_right, base);/* lrr: RH or RH-1 */
		RCU_INIT_POINTER(node->avl_left, lrr); /* lrr: RH or RH-1 */
		RCU_INIT_POINTER(node->avl_right, r); /* r: RH */
		node->avl_height = rh + 1; /* node: RH+1 */
		RCU_INIT_POINTER(l->avl_left, ll); /* ll: RH */
		RCU_INIT_POINTER(l->avl_right, lrl); /* lrl: RH or RH-1 */
		l->avl_height = rh + 1; /* l: RH+1 */
		RCU_INIT_POINTER(lr->avl_left, l); /* l: RH+1 */
		RCU_INIT_POINTER(lr->avl_right, node); /* node: RH+1 */
		lr->avl_height = rh + 2;
		RCU_INIT_POINTER(*nodep, lr);
		}
		} else if (rh > lh + 1) { /* r: LH+2 */
		struct inet_peer rr, rl, rlr, rll;
		int rlh;
		rr = rcu_deref_locked(r->avl_right, base);
		rl = rcu_deref_locked(r->avl_left, base);
		rlh = node_height(rl);
		if (rlh <= node_height(rr)) { /* rr: LH+1 */
		RCU_INIT_POINTER(node->avl_right, rl); /* rl: LH or LH+1 */
		RCU_INIT_POINTER(node->avl_left, l); /* l: LH */
		node->avl_height = rlh + 1; /* LH+1 or LH+2 */
		RCU_INIT_POINTER(r->avl_right, rr); /* rr: LH+1 */
		RCU_INIT_POINTER(r->avl_left, node); /* node: LH+1 or LH+2 */
		r->avl_height = node->avl_height + 1;
		RCU_INIT_POINTER(*nodep, r);
		} else { /* rr: RH, rl: RH+1 */
		rlr = rcu_deref_locked(rl->avl_right, base);/* rlr: LH or LH-1 */
		rll = rcu_deref_locked(rl->avl_left, base);/* rll: LH or LH-1 */
		RCU_INIT_POINTER(node->avl_right, rll); /* rll: LH or LH-1 */
		RCU_INIT_POINTER(node->avl_left, l); /* l: LH */
		node->avl_height = lh + 1; /* node: LH+1 */
		RCU_INIT_POINTER(r->avl_right, rr); /* rr: LH */
		RCU_INIT_POINTER(r->avl_left, rlr); /* rlr: LH or LH-1 */
		r->avl_height = lh + 1; /* r: LH+1 */
		RCU_INIT_POINTER(rl->avl_right, r); /* r: LH+1 */
		RCU_INIT_POINTER(rl->avl_left, node); /* node: LH+1 */
		rl->avl_height = lh + 2;
		RCU_INIT_POINTER(*nodep, rl);
		}
		} else {
		node->avl_height = (lh > rh ? lh : rh) + 1;
		}
		}
		}

		/* Called with local BH disabled and the pool lock held. */
		#define link_to_pool(n, base) \
		do { \
		n->avl_height = 1; \
		n->avl_left = peer_avl_empty_rcu; \
		n->avl_right = peer_avl_empty_rcu; \
		/* lockless readers can catch us now */ \
		rcu_assign_pointer(**--stackptr, n); \
		peer_avl_rebalance(stack, stackptr, base); \
		} while (0)

		static void inetpeer_free_rcu(struct rcu_head *head)
		{
		kmem_cache_free(peer_cachep, container_of(head, struct inet_peer, rcu));
		}

		static void unlink_from_pool(struct inet_peer p, struct inet_peer_base base,
		struct inet_peer __rcu **stack[PEER_MAXDEPTH])
		{
		struct inet_peer __rcu *stackptr, *delp;

		if (lookup(&p->daddr, stack, base) != p)
		BUG();
		delp = stackptr - 1; /* delp[0] == p /
		if (p->avl_left == peer_avl_empty_rcu) {
		*delp[0] = p->avl_right;
		--stackptr;
		} else {
		/* look for a node to insert instead of p */
		struct inet_peer *t;
		t = lookup_rightempty(p, base);
		BUG_ON(rcu_deref_locked(*stackptr[-1], base) != t);
		**--stackptr = t->avl_left;
		/* t is removed, t->daddr > x->daddr for any
		* x in p->avl_left subtree.
		* Put t in the old place of p. */
		RCU_INIT_POINTER(*delp[0], t);
		t->avl_left = p->avl_left;
		t->avl_right = p->avl_right;
		t->avl_height = p->avl_height;
		BUG_ON(delp[1] != &p->avl_left);
		delp[1] = &t->avl_left; /* was &p->avl_left */
		}
		peer_avl_rebalance(stack, stackptr, base);
		base->total--;
		call_rcu(&p->rcu, inetpeer_free_rcu);
		}

		/* perform garbage collect on all items stacked during a lookup */
		static int inet_peer_gc(struct inet_peer_base *base,
		struct inet_peer __rcu **stack[PEER_MAXDEPTH],
		struct inet_peer __rcu ***stackptr)
		static void inet_peer_gc(struct inet_peer_base *base,
		struct inet_peer *gc_stack[],
		unsigned int gc_cnt)
		{
		struct inet_peer p, gchead = NULL;
		struct inet_peer *p;
		__u32 delta, ttl;
		int cnt = 0;
		int i;

		if (base->total >= inet_peer_threshold)
		ttl = 0; /* be aggressive */
		@@ -379,43 +154,38 @@ static int inet_peer_gc(struct inet_peer_base *base,
		ttl = inet_peer_maxttl
		- (inet_peer_maxttl - inet_peer_minttl) / HZ *
		base->total / inet_peer_threshold * HZ;
		stackptr--; /* last stack slot is peer_avl_empty */
		while (stackptr > stack) {
		stackptr--;
		p = rcu_deref_locked(**stackptr, base);
		if (refcount_read(&p->refcnt) == 1) {
		smp_rmb();
		for (i = 0; i < gc_cnt; i++) {
		p = gc_stack[i];
		delta = (__u32)jiffies - p->dtime;
		if (delta >= ttl && refcount_dec_if_one(&p->refcnt)) {
		p->gc_next = gchead;
		gchead = p;
		}
		if (delta < ttl \|\| !refcount_dec_if_one(&p->refcnt))
		gc_stack[i] = NULL;
		}
		for (i = 0; i < gc_cnt; i++) {
		p = gc_stack[i];
		if (p) {
		rb_erase(&p->rb_node, &base->rb_root);
		base->total--;
		call_rcu(&p->rcu, inetpeer_free_rcu);
		}
		while ((p = gchead) != NULL) {
		gchead = p->gc_next;
		cnt++;
		unlink_from_pool(p, base, stack);
		}
		return cnt;
		}

		struct inet_peer inet_getpeer(struct inet_peer_base base,
		const struct inetpeer_addr *daddr,
		int create)
		{
		struct inet_peer __rcu stack[PEER_MAXDEPTH], *stackptr;
		struct inet_peer *p;
		unsigned int sequence;
		int invalidated, gccnt = 0;
		struct inet_peer p, gc_stack[PEER_MAX_GC];
		struct rb_node *pp, parent;
		unsigned int gc_cnt, seq;
		int invalidated;

		/* Attempt a lockless lookup first.
		* Because of a concurrent writer, we might not find an existing entry.
		*/
		rcu_read_lock();
		sequence = read_seqbegin(&base->lock);
		p = lookup_rcu(daddr, base);
		invalidated = read_seqretry(&base->lock, sequence);
		seq = read_seqbegin(&base->lock);
		p = lookup(daddr, base, seq, NULL, &gc_cnt, &parent, &pp);
		invalidated = read_seqretry(&base->lock, seq);
		rcu_read_unlock();

		if (p)
		@@ -428,20 +198,13 @@ struct inet_peer inet_getpeer(struct inet_peer_base base,
		/* retry an exact lookup, taking the lock before.
		* At least, nodes should be hot in our cache.
		*/
		parent = NULL;
		write_seqlock_bh(&base->lock);
		relookup:
		p = lookup(daddr, stack, base);
		if (p != peer_avl_empty) {
		refcount_inc(&p->refcnt);
		write_sequnlock_bh(&base->lock);
		return p;
		}
		if (!gccnt) {
		gccnt = inet_peer_gc(base, stack, stackptr);
		if (gccnt && create)
		goto relookup;
		}
		p = create ? kmem_cache_alloc(peer_cachep, GFP_ATOMIC) : NULL;

		gc_cnt = 0;
		p = lookup(daddr, base, seq, gc_stack, &gc_cnt, &parent, &pp);
		if (!p && create) {
		p = kmem_cache_alloc(peer_cachep, GFP_ATOMIC);
		if (p) {
		p->daddr = *daddr;
		refcount_set(&p->refcnt, 2);
		@@ -452,12 +215,14 @@ relookup:
		* calculation of tokens is at its maximum.
		*/
		p->rate_last = jiffies - 60*HZ;
		INIT_LIST_HEAD(&p->gc_list);

		/* Link the node. */
		link_to_pool(p, base);
		rb_link_node(&p->rb_node, parent, pp);
		rb_insert_color(&p->rb_node, &base->rb_root);
		base->total++;
		}
		}
		if (gc_cnt)
		inet_peer_gc(base, gc_stack, gc_cnt);
		write_sequnlock_bh(&base->lock);

		return p;
		@@ -467,8 +232,9 @@ EXPORT_SYMBOL_GPL(inet_getpeer);
		void inet_putpeer(struct inet_peer *p)
		{
		p->dtime = (__u32)jiffies;
		smp_mb__before_atomic();
		refcount_dec(&p->refcnt);

		if (refcount_dec_and_test(&p->refcnt))
		call_rcu(&p->rcu, inetpeer_free_rcu);
		}
		EXPORT_SYMBOL_GPL(inet_putpeer);

		@@ -513,30 +279,16 @@ bool inet_peer_xrlim_allow(struct inet_peer *peer, int timeout)
		}
		EXPORT_SYMBOL(inet_peer_xrlim_allow);

		static void inetpeer_inval_rcu(struct rcu_head *head)
		{
		struct inet_peer *p = container_of(head, struct inet_peer, gc_rcu);

		spin_lock_bh(&gc_lock);
		list_add_tail(&p->gc_list, &gc_list);
		spin_unlock_bh(&gc_lock);

		schedule_delayed_work(&gc_work, gc_delay);
		}

		void inetpeer_invalidate_tree(struct inet_peer_base *base)
		{
		struct inet_peer *root;

		write_seqlock_bh(&base->lock);
		struct inet_peer p, n;

		root = rcu_deref_locked(base->root, base);
		if (root != peer_avl_empty) {
		base->root = peer_avl_empty_rcu;
		base->total = 0;
		call_rcu(&root->gc_rcu, inetpeer_inval_rcu);
		rbtree_postorder_for_each_entry_safe(p, n, &base->rb_root, rb_node) {
		inet_putpeer(p);
		cond_resched();
		}

		write_sequnlock_bh(&base->lock);
		base->rb_root = RB_ROOT;
		base->total = 0;
		}
		EXPORT_SYMBOL(inetpeer_invalidate_tree);

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