From: "Ahmed S. Darwish" <a.darwish@linutronix.de>
Date: Mon, 20 Jul 2020 17:55:21 +0200
Subject: netfilter: nft_set_rbtree: Use sequence counter with associated
 rwlock
Patch-mainline: v5.9-rc1
Git-commit: b901892b51317b321c7bc96e2ccd2f522d1380ee
References: bsc#1176564 bsc#1162702

A sequence counter write side critical section must be protected by some
form of locking to serialize writers. A plain seqcount_t does not
contain the information of which lock must be held when entering a write
side critical section.

Use the new seqcount_rwlock_t data type, which allows to associate a
rwlock with the sequence counter. This enables lockdep to verify that
the rwlock used for writer serialization is held when the write side
critical section is entered.

If lockdep is disabled this lock association is compiled out and has
neither storage size nor runtime overhead.

Signed-off-by: Ahmed S. Darwish <a.darwish@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20200720155530.1173732-16-a.darwish@linutronix.de
Acked-by: Daniel Wagner <dwagner@suse.de>
---
 net/netfilter/nft_set_rbtree.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/net/netfilter/nft_set_rbtree.c
+++ b/net/netfilter/nft_set_rbtree.c
@@ -18,7 +18,7 @@
 struct nft_rbtree {
 	struct rb_root		root;
 	rwlock_t		lock;
-	seqcount_t		count;
+	seqcount_rwlock_t	count;
 	struct delayed_work	gc_work;
 };
 
@@ -426,7 +426,7 @@ static int nft_rbtree_init(const struct
 	struct nft_rbtree *priv = nft_set_priv(set);
 
 	rwlock_init(&priv->lock);
-	seqcount_init(&priv->count);
+	seqcount_rwlock_init(&priv->count, &priv->lock);
 	priv->root = RB_ROOT;
 
 	INIT_DEFERRABLE_WORK(&priv->gc_work, nft_rbtree_gc);