netdev - [PATCH net-next 11/13] net: sched: implement tcf_block_get() and tcf_block

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Message-Id: <1536220742-25650-12-git-send-email-vladbu@mellanox.com>
Date:   Thu,  6 Sep 2018 10:59:00 +0300
From:   Vlad Buslov <vladbu@...lanox.com>
To:     netdev@...r.kernel.org
Cc:     jhs@...atatu.com, xiyou.wangcong@...il.com, jiri@...nulli.us,
        davem@...emloft.net, stephen@...workplumber.org,
        ktkhai@...tuozzo.com, paulmck@...ux.vnet.ibm.com,
        nicolas.dichtel@...nd.com, leon@...nel.org,
        gregkh@...uxfoundation.org, mark.rutland@....com, fw@...len.de,
        dsahern@...il.com, lucien.xin@...il.com,
        jakub.kicinski@...ronome.com, christian.brauner@...ntu.com,
        jbenc@...hat.com, Vlad Buslov <vladbu@...lanox.com>
Subject: [PATCH net-next 11/13] net: sched: implement tcf_block_get() and tcf_block_put()

Implement get/put function for blocks that only take/release the reference
and perform deallocation. These functions are intended to be used by
unlocked rules update path to always hold reference to block while working
with it. They use on new fine-grained locking mechanisms introduced in
previous patches in this set, instead of relying on global protection
provided by rtnl lock.

Extract code that is common with tcf_block_detach_ext() into common
function __tcf_block_put().

Signed-off-by: Vlad Buslov <vladbu@...lanox.com>
Acked-by: Jiri Pirko <jiri@...lanox.com>
---
 net/sched/cls_api.c | 70 ++++++++++++++++++++++++++++++++++++-----------------
 1 file changed, 48 insertions(+), 22 deletions(-)

diff --git a/net/sched/cls_api.c b/net/sched/cls_api.c
index f06aa9313a58..5d9f91331d26 100644
--- a/net/sched/cls_api.c
+++ b/net/sched/cls_api.c
@@ -537,6 +537,19 @@ static struct tcf_block *tcf_block_lookup(struct net *net, u32 block_index)
 	return idr_find(&tn->idr, block_index);
 }
 
+static struct tcf_block *tcf_block_get(struct net *net, u32 block_index)
+{
+	struct tcf_block *block;
+
+	rcu_read_lock();
+	block = tcf_block_lookup(net, block_index);
+	if (block && !refcount_inc_not_zero(&block->refcnt))
+		block = NULL;
+	rcu_read_unlock();
+
+	return block;
+}
+
 static void tcf_qdisc_put(struct Qdisc *q, bool rtnl_held)
 {
 	if (!q)
@@ -573,6 +586,40 @@ static void tcf_block_put_all_chains(struct tcf_block *block)
 	}
 }
 
+static void __tcf_block_put(struct tcf_block *block, struct Qdisc *q,
+			    struct tcf_block_ext_info *ei)
+{
+	if (refcount_dec_and_test(&block->refcnt)) {
+		/* Flushing/putting all chains will cause the block to be
+		 * deallocated when last chain is freed. However, if chain_list
+		 * is empty, block has to be manually deallocated. After block
+		 * reference counter reached 0, it is no longer possible to
+		 * increment it or add new chains to block.
+		 */
+		bool free_block = list_empty(&block->chain_list);
+
+		if (tcf_block_shared(block))
+			tcf_block_remove(block, block->net);
+		if (!free_block)
+			tcf_block_flush_all_chains(block);
+
+		if (q)
+			tcf_block_offload_unbind(block, q, ei);
+
+		if (free_block)
+			kfree_rcu(block, rcu);
+		else
+			tcf_block_put_all_chains(block);
+	} else if (q) {
+		tcf_block_offload_unbind(block, q, ei);
+	}
+}
+
+static void tcf_block_put(struct tcf_block *block)
+{
+	__tcf_block_put(block, NULL, NULL);
+}
+
 /* Find tcf block.
  * Set q, parent, cl when appropriate.
  */
@@ -835,28 +882,7 @@ void tcf_block_detach_ext(struct tcf_block *block, struct Qdisc *q,
 	tcf_chain0_head_change_cb_del(block, ei);
 	tcf_block_owner_del(block, q, ei->binder_type);
 
-	if (refcount_dec_and_test(&block->refcnt)) {
-		/* Flushing/putting all chains will cause the block to be
-		 * deallocated when last chain is freed. However, if chain_list
-		 * is empty, block has to be manually deallocated. After block
-		 * reference counter reached 0, it is no longer possible to
-		 * increment it or add new chains to block.
-		 */
-		bool free_block = list_empty(&block->chain_list);
-
-		if (tcf_block_shared(block))
-			tcf_block_remove(block, block->net);
-		if (!free_block)
-			tcf_block_flush_all_chains(block);
-		tcf_block_offload_unbind(block, q, ei);
-
-		if (free_block)
-			kfree_rcu(block, rcu);
-		else
-			tcf_block_put_all_chains(block);
-	} else {
-		tcf_block_offload_unbind(block, q, ei);
-	}
+	__tcf_block_put(block, q, ei);
 }
 EXPORT_SYMBOL(tcf_block_detach_ext);
 
-- 
2.7.5