[PATCH -stable,4.19.x 18/40] netfilter: nft_set_rbtree: use read spinlock to avoid datapath contention

Pablo Neira Ayuso
2024-06-13T01:02:30Z

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>
---
net/netfilter/nft_set_rbtree.c | 6 ++----
1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/net/netfilter/nft_set_rbtree.c b/net/netfilter/nft_set_rbtree.c
index 8bda3f25360b..69fb57f6a23f 100644
--- a/net/netfilter/nft_set_rbtree.c
+++ b/net/netfilter/nft_set_rbtree.c
@@ -629,8 +629,7 @@ 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. */
@@ -679,8 +678,7 @@ static void nft_rbtree_gc(struct work_struct *work)
}

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);
--
2.30.2