rhashtable: Add rhashtable_free_and_destroy()

rhashtable_destroy() variant which stops rehashes, iterates over
the table and calls a callback to release resources.

Avoids need for nft_hash to embed rhashtable internals and allows to
get rid of the being_destroyed flag. It also saves a 2nd mutex
lock upon destruction.

Also fixes an RCU lockdep splash on nft set destruction due to
calling rht_for_each_entry_safe() without holding bucket locks.
Open code this loop as we need know that no mutations may occur in
parallel.

Signed-off-by: Thomas Graf <tgraf@suug.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 7 insertions, 18 deletions

diff --git a/net/netfilter/nft_hash.c b/net/netfilter/nft_hash.c
index 8577a37..f9ce219 100644
--- a/net/netfilter/nft_hash.c
+++ b/net/netfilter/nft_hash.c
@@ -188,26 +188,15 @@ static int nft_hash_init(const struct nft_set *set,
 	return rhashtable_init(priv, &params);
 }
 
-static void nft_hash_destroy(const struct nft_set *set)
+static void nft_free_element(void *ptr, void *arg)
 {
-	struct rhashtable *priv = nft_set_priv(set);
-	const struct bucket_table *tbl;
-	struct nft_hash_elem *he;
-	struct rhash_head *pos, *next;
-	unsigned int i;
-
-	/* Stop an eventual async resizing */
-	priv->being_destroyed = true;
-	mutex_lock(&priv->mutex);
-
-	tbl = rht_dereference(priv->tbl, priv);
-	for (i = 0; i < tbl->size; i++) {
-		rht_for_each_entry_safe(he, pos, next, tbl, i, node)
-			nft_hash_elem_destroy(set, he);
-	}
-	mutex_unlock(&priv->mutex);
+	nft_hash_elem_destroy((const struct nft_set *)arg, ptr);
+}
 
-	rhashtable_destroy(priv);
+static void nft_hash_destroy(const struct nft_set *set)
+{
+	rhashtable_free_and_destroy(nft_set_priv(set), nft_free_element,
+				    (void *)set);
 }
 
 static bool nft_hash_estimate(const struct nft_set_desc *desc, u32 features,