rhashtable: Free bucket tables asynchronously after rehash

There is in fact no need to wait for an RCU grace period in the
rehash function, since all insertions are guaranteed to go into
the new table through spin locks.

This patch uses call_rcu to free the old/rehashed table at our
leisure.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 6 insertions, 3 deletions

diff --git a/lib/rhashtable.c b/lib/rhashtable.c
index e55bbc84c449..36fb0910bec2 100644
--- a/lib/rhashtable.c
+++ b/lib/rhashtable.c
@@ -141,6 +141,11 @@ static void bucket_table_free(const struct bucket_table *tbl)
         kvfree(tbl);
 }
 
+static void bucket_table_free_rcu(struct rcu_head *head)
+{
+        bucket_table_free(container_of(head, struct bucket_table, rcu));
+}
+
 static struct bucket_table *bucket_table_alloc(struct rhashtable *ht,
                                                size_t nbuckets)
 {
@@ -288,9 +293,7 @@ static void rhashtable_rehash(struct rhashtable *ht,
          * table, and thus no references to the old table will
          * remain.
          */
-        synchronize_rcu();
-
-        bucket_table_free(old_tbl);
+        call_rcu(&old_tbl->rcu, bucket_table_free_rcu);
 }
 
 /**