From: Sasha Levin <sashal@kernel.org>
Date: Fri, 22 Sep 2023 17:01:15 +0000 (+0200)
Subject: netfilter: nft_set_rbtree: use read spinlock to avoid datapath contention
X-Git-Tag: archive/raspbian/5.10.197-1+rpi1^2~22
X-Git-Url: https://dgit.raspbian.org/?a=commitdiff_plain;h=c8a3c2e2dca69850ecb51f050bb38e3202d3f03a;p=linux.git

netfilter: nft_set_rbtree: use read spinlock to avoid datapath contention

commit 96b33300fba880ec0eafcf3d82486f3463b4b6da upstream.

rbtree GC does not modify the datastructure, instead it collects expired
elements and it enqueues a GC transaction. Use a read spinlock instead
to avoid data contention while GC worker is running.

Fixes: f6c383b8c31a ("netfilter: nf_tables: adapt set backend to use GC transaction API")
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

Gbp-Pq: Topic bugfix/all
Gbp-Pq: Name netfilter-nft_set_rbtree-use-read-spinlock-to-avoid-.patch
---

diff --git a/net/netfilter/nft_set_rbtree.c b/net/netfilter/nft_set_rbtree.c
index 535076b4de5..cc32e19b404 100644
--- a/net/netfilter/nft_set_rbtree.c
+++ b/net/netfilter/nft_set_rbtree.c
@@ -624,8 +624,7 @@ static void nft_rbtree_gc(struct work_struct *work)
 	if (!gc)
 		goto done;
 
-	write_lock_bh(&priv->lock);
-	write_seqcount_begin(&priv->count);
+	read_lock_bh(&priv->lock);
 	for (node = rb_first(&priv->root); node != NULL; node = rb_next(node)) {
 
 		/* Ruleset has been updated, try later. */
@@ -672,8 +671,7 @@ dead_elem:
 		nft_trans_gc_elem_add(gc, rbe);
 	}
 try_later:
-	write_seqcount_end(&priv->count);
-	write_unlock_bh(&priv->lock);
+	read_unlock_bh(&priv->lock);
 
 	if (gc)
 		nft_trans_gc_queue_async_done(gc);