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Commit 7bd8490e authored by Eric Dumazet's avatar Eric Dumazet Committed by Pablo Neira Ayuso
Browse files

netfilter: xt_hashlimit: perform garbage collection from process context 



xt_hashlimit cannot be used with large hash tables, because garbage
collector is run from a timer. If table is really big, its possible
to hold cpu for more than 500 msec, which is unacceptable.

Switch to a work queue, and use proper scheduling points to remove
latencies spikes.

Later, we also could switch to a smoother garbage collection done
at lookup time, one bucket at a time...

Signed-off-by: default avatarEric Dumazet <edumazet@google.com>
Cc: Florian Westphal <fw@strlen.de>
Cc: Patrick McHardy <kaber@trash.net>
Reviewed-by: default avatarFlorian Westphal <fw@strlen.de>
Signed-off-by: default avatarPablo Neira Ayuso <pablo@netfilter.org>
parent 5b96af77

net/netfilter/xt_hashlimit.c

+16 −15
Original line number Diff line number Diff line
@@ -104,7 +104,7 @@ struct xt_hashlimit_htable { 
	spinlock_t lock;		/* lock for list_head */

	u_int32_t rnd;			/* random seed for hash */

	unsigned int count;		/* number entries in table */

	struct timer_list timer;	/* timer for gc */

	struct delayed_work gc_work;



	/* seq_file stuff */

	struct proc_dir_entry *pde;
@@ -213,7 +213,7 @@ dsthash_free(struct xt_hashlimit_htable *ht, struct dsthash_ent *ent) 
	call_rcu_bh(&ent->rcu, dsthash_free_rcu);

	ht->count--;

}

static void htable_gc(unsigned long htlong);

static void htable_gc(struct work_struct *work);



static int htable_create(struct net *net, struct xt_hashlimit_mtinfo1 *minfo,

			 u_int8_t family)
@@ -273,9 +273,9 @@ static int htable_create(struct net *net, struct xt_hashlimit_mtinfo1 *minfo, 
	}

	hinfo->net = net;



	setup_timer(&hinfo->timer, htable_gc, (unsigned long)hinfo);

	hinfo->timer.expires = jiffies + msecs_to_jiffies(hinfo->cfg.gc_interval);

	add_timer(&hinfo->timer);

	INIT_DEFERRABLE_WORK(&hinfo->gc_work, htable_gc);

	queue_delayed_work(system_power_efficient_wq, &hinfo->gc_work,

			   msecs_to_jiffies(hinfo->cfg.gc_interval));



	hlist_add_head(&hinfo->node, &hashlimit_net->htables);
@@ -300,29 +300,30 @@ static void htable_selective_cleanup(struct xt_hashlimit_htable *ht, 
{

	unsigned int i;



	/* lock hash table and iterate over it */

	spin_lock_bh(&ht->lock);

	for (i = 0; i < ht->cfg.size; i++) {

		struct dsthash_ent *dh;

		struct hlist_node *n;



		spin_lock_bh(&ht->lock);

		hlist_for_each_entry_safe(dh, n, &ht->hash[i], node) {

			if ((*select)(ht, dh))

				dsthash_free(ht, dh);

		}

	}

		spin_unlock_bh(&ht->lock);

		cond_resched();

	}

}



/* hash table garbage collector, run by timer */

static void htable_gc(unsigned long htlong)

static void htable_gc(struct work_struct *work)

{

	struct xt_hashlimit_htable *ht = (struct xt_hashlimit_htable *)htlong;

	struct xt_hashlimit_htable *ht;



	ht = container_of(work, struct xt_hashlimit_htable, gc_work.work);



	htable_selective_cleanup(ht, select_gc);



	/* re-add the timer accordingly */

	ht->timer.expires = jiffies + msecs_to_jiffies(ht->cfg.gc_interval);

	add_timer(&ht->timer);

	queue_delayed_work(system_power_efficient_wq,

			   &ht->gc_work, msecs_to_jiffies(ht->cfg.gc_interval));

}



static void htable_remove_proc_entry(struct xt_hashlimit_htable *hinfo)
@@ -341,7 +342,7 @@ static void htable_remove_proc_entry(struct xt_hashlimit_htable *hinfo) 


static void htable_destroy(struct xt_hashlimit_htable *hinfo)

{

	del_timer_sync(&hinfo->timer);

	cancel_delayed_work_sync(&hinfo->gc_work);

	htable_remove_proc_entry(hinfo);

	htable_selective_cleanup(hinfo, select_all);

	kfree(hinfo->name);