[PATCH nf 2/2] netfilter: nft_set_pipapo: prevent soft lockup during gc walk

[Florian Westphal <fw@strlen.de>]

The gc scan+shrinking process can take a very long time.

Add an upper ceiling: If we've queued up some elements for removal
already give up after spending up to 10s on gc compaction.

Note this intentionally doesn't add a call to cond_resched();
PREEMPT_NONE and _VOLUNTARY preemption models have been removed
recently.

Reported-by: Yiming Qian <yimingqian591@gmail.com>
Fixes: 3c4287f62044 ("nf_tables: Add set type for arbitrary concatenation of ranges")
Signed-off-by: Florian Westphal <fw@strlen.de>
---
 net/netfilter/nft_set_pipapo.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/net/netfilter/nft_set_pipapo.c b/net/netfilter/nft_set_pipapo.c
index d850166b8e45..0cd91f809655 100644
--- a/net/netfilter/nft_set_pipapo.c
+++ b/net/netfilter/nft_set_pipapo.c
@@ -1686,6 +1686,7 @@ static void nft_pipapo_gc_deactivate(struct net *net, struct nft_set *set,
  */
 static void pipapo_gc_scan(struct nft_set *set, struct nft_pipapo_match *m)
 {
+	unsigned long stop_time = jiffies + 10 * HZ;
 	struct nft_pipapo *priv = nft_set_priv(set);
 	struct net *net = read_pnet(&set->net);
 	unsigned int rules_f0, first_rule = 0;
@@ -1697,6 +1698,9 @@ static void pipapo_gc_scan(struct nft_set *set, struct nft_pipapo_match *m)
 		const struct nft_pipapo_field *f;
 		unsigned int i, start, rules_fx;
 
+		if (priv->to_free && time_after(jiffies, stop_time))
+			return;
+
 		start = first_rule;
 		rules_fx = rules_f0;
 
-- 
2.52.0