nfsd: replace call_rcu by kfree_rcu for simple kmem_cache_free callback

Since SLOB was removed and since
commit 6c6c47b ("mm, slab: call kvfree_rcu_barrier() from kmem_cache_destroy()"),
it is not necessary to use call_rcu when the callback only performs
kmem_cache_free. Use kfree_rcu() directly.

The changes were made using Coccinelle.

Signed-off-by: Julia Lawall <Julia.Lawall@inria.fr>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Acked-by: Paul E. McKenney <paulmck@kernel.org>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>

fs/nfsd/nfs4state.c

@@ -572,21 +572,14 @@ opaque_hashval(const void *ptr, int nbytes)
 	return x;
 }
 
-static void nfsd4_free_file_rcu(struct rcu_head *rcu)
-{
-	struct nfs4_file *fp = container_of(rcu, struct nfs4_file, fi_rcu);
-
-	kmem_cache_free(file_slab, fp);
-}
-
 void
 put_nfs4_file(struct nfs4_file *fi)
 {
 	if (refcount_dec_and_test(&fi->fi_ref)) {
 		nfsd4_file_hash_remove(fi);
 		WARN_ON_ONCE(!list_empty(&fi->fi_clnt_odstate));
 		WARN_ON_ONCE(!list_empty(&fi->fi_delegations));
-		call_rcu(&fi->fi_rcu, nfsd4_free_file_rcu);
+		kfree_rcu(fi, fi_rcu);
 	}
 }