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: Eric Dumazet <edumazet@google.com>
Cc: Florian Westphal <fw@strlen.de>
Cc: Patrick McHardy <kaber@trash.net>
Reviewed-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

1 files changed, 16 insertions, 15 deletions

diff --git a/net/netfilter/xt_hashlimit.c b/net/netfilter/xt_hashlimit.c
index a3910fc2122b..47dc6836830a 100644
--- a/net/netfilter/xt_hashlimit.c
+++ b/net/netfilter/xt_hashlimit.c
@@ -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();
         }
-        spin_unlock_bh(&ht->lock);
 }
 
-/* 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);