net: sch: api: add extack support in tcf_block_get

This patch adds extack support for the function tcf_block_get which is
a common used function in the tc subsystem. Callers which are interested
in the receiving error can assign extack to get a more detailed
information why tcf_block_get failed.

Cc: David Ahern <dsahern@gmail.com>
Acked-by: Jamal Hadi Salim <jhs@mojatatu.com>
Signed-off-by: Alexander Aring <aring@mojatatu.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/sched/cls_api.c b/net/sched/cls_api.c
index 22b977d..4591b87 100644
--- a/net/sched/cls_api.c
+++ b/net/sched/cls_api.c
@@ -281,20 +281,24 @@ static void tcf_block_offload_unbind(struct tcf_block *block, struct Qdisc *q,
 }
 
 int tcf_block_get_ext(struct tcf_block **p_block, struct Qdisc *q,
-		      struct tcf_block_ext_info *ei)
+		      struct tcf_block_ext_info *ei,
+		      struct netlink_ext_ack *extack)
 {
 	struct tcf_block *block = kzalloc(sizeof(*block), GFP_KERNEL);
 	struct tcf_chain *chain;
 	int err;
 
-	if (!block)
+	if (!block) {
+		NL_SET_ERR_MSG(extack, "Memory allocation for block failed");
 		return -ENOMEM;
+	}
 	INIT_LIST_HEAD(&block->chain_list);
 	INIT_LIST_HEAD(&block->cb_list);
 
 	/* Create chain 0 by default, it has to be always present. */
 	chain = tcf_chain_create(block, 0);
 	if (!chain) {
+		NL_SET_ERR_MSG(extack, "Failed to create new tcf chain");
 		err = -ENOMEM;
 		goto err_chain_create;
 	}
@@ -321,7 +325,8 @@ static void tcf_chain_head_change_dflt(struct tcf_proto *tp_head, void *priv)
 }
 
 int tcf_block_get(struct tcf_block **p_block,
-		  struct tcf_proto __rcu **p_filter_chain, struct Qdisc *q)
+		  struct tcf_proto __rcu **p_filter_chain, struct Qdisc *q,
+		  struct netlink_ext_ack *extack)
 {
 	struct tcf_block_ext_info ei = {
 		.chain_head_change = tcf_chain_head_change_dflt,
@@ -329,7 +334,7 @@ int tcf_block_get(struct tcf_block **p_block,
 	};
 
 	WARN_ON(!p_filter_chain);
-	return tcf_block_get_ext(p_block, q, &ei);
+	return tcf_block_get_ext(p_block, q, &ei, extack);
 }
 EXPORT_SYMBOL(tcf_block_get);