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Message-Id: <20190204123301.4223-8-vladbu@mellanox.com>
Date: Mon, 4 Feb 2019 14:32:52 +0200
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, ast@...nel.org, daniel@...earbox.net,
Vlad Buslov <vladbu@...lanox.com>
Subject: [PATCH net-next v3 07/16] net: sched: introduce reference counting for tcf_proto
In order to remove dependency on rtnl lock and allow concurrent tcf_proto
modification, extend tcf_proto with reference counter. Implement helper
get/put functions for tcf proto and use them to modify cls API to always
take reference to tcf_proto while using it. Only release reference to
parent chain after releasing last reference to tp.
Signed-off-by: Vlad Buslov <vladbu@...lanox.com>
---
Changes from V2 to V3:
- Add local tp_next var to tcf_chain_flush() and use it to store
tp->next pointer dereferenced with rcu_dereference_protected() to
satisfy kbuild test robot.
- Reset tp pointer to NULL at the beginning of tc_new_tfilter() to
prevent its uninitialized usage in error handling code. This code
was already implemented in patch 10, but must be in patch 8 to
preserve code bisectability.
- Put parent chain in tcf_proto_destroy(). In previous version this
code was implemented in patch 1 which was removed in V3.
include/net/sch_generic.h | 1 +
net/sched/cls_api.c | 53 ++++++++++++++++++++++++++++++++++++++---------
2 files changed, 44 insertions(+), 10 deletions(-)
diff --git a/include/net/sch_generic.h b/include/net/sch_generic.h
index 85993d7efee6..4372c08fc4d9 100644
--- a/include/net/sch_generic.h
+++ b/include/net/sch_generic.h
@@ -322,6 +322,7 @@ struct tcf_proto {
void *data;
const struct tcf_proto_ops *ops;
struct tcf_chain *chain;
+ refcount_t refcnt;
struct rcu_head rcu;
};
diff --git a/net/sched/cls_api.c b/net/sched/cls_api.c
index d3fa1043b7fd..90a59b5966fe 100644
--- a/net/sched/cls_api.c
+++ b/net/sched/cls_api.c
@@ -172,6 +172,7 @@ static struct tcf_proto *tcf_proto_create(const char *kind, u32 protocol,
tp->protocol = protocol;
tp->prio = prio;
tp->chain = chain;
+ refcount_set(&tp->refcnt, 1);
err = tp->ops->init(tp);
if (err) {
@@ -185,14 +186,29 @@ static struct tcf_proto *tcf_proto_create(const char *kind, u32 protocol,
return ERR_PTR(err);
}
+static void tcf_proto_get(struct tcf_proto *tp)
+{
+ refcount_inc(&tp->refcnt);
+}
+
+static void tcf_chain_put(struct tcf_chain *chain);
+
static void tcf_proto_destroy(struct tcf_proto *tp,
struct netlink_ext_ack *extack)
{
tp->ops->destroy(tp, extack);
+ tcf_chain_put(tp->chain);
module_put(tp->ops->owner);
kfree_rcu(tp, rcu);
}
+static void tcf_proto_put(struct tcf_proto *tp,
+ struct netlink_ext_ack *extack)
+{
+ if (refcount_dec_and_test(&tp->refcnt))
+ tcf_proto_destroy(tp, extack);
+}
+
#define ASSERT_BLOCK_LOCKED(block) \
lockdep_assert_held(&(block)->lock)
@@ -437,18 +453,18 @@ static void tcf_chain_put_explicitly_created(struct tcf_chain *chain)
static void tcf_chain_flush(struct tcf_chain *chain)
{
- struct tcf_proto *tp;
+ struct tcf_proto *tp, *tp_next;
mutex_lock(&chain->filter_chain_lock);
tp = tcf_chain_dereference(chain->filter_chain, chain);
+ RCU_INIT_POINTER(chain->filter_chain, NULL);
tcf_chain0_head_change(chain, NULL);
mutex_unlock(&chain->filter_chain_lock);
while (tp) {
- RCU_INIT_POINTER(chain->filter_chain, tp->next);
- tcf_proto_destroy(tp, NULL);
- tp = rtnl_dereference(chain->filter_chain);
- tcf_chain_put(chain);
+ tp_next = rcu_dereference_protected(tp->next, 1);
+ tcf_proto_put(tp, NULL);
+ tp = tp_next;
}
}
@@ -1492,9 +1508,9 @@ static void tcf_chain_tp_insert(struct tcf_chain *chain,
{
if (*chain_info->pprev == chain->filter_chain)
tcf_chain0_head_change(chain, tp);
+ tcf_proto_get(tp);
RCU_INIT_POINTER(tp->next, tcf_chain_tp_prev(chain, chain_info));
rcu_assign_pointer(*chain_info->pprev, tp);
- tcf_chain_hold(chain);
}
static void tcf_chain_tp_remove(struct tcf_chain *chain,
@@ -1506,7 +1522,6 @@ static void tcf_chain_tp_remove(struct tcf_chain *chain,
if (tp == chain->filter_chain)
tcf_chain0_head_change(chain, next);
RCU_INIT_POINTER(*chain_info->pprev, next);
- tcf_chain_put(chain);
}
static struct tcf_proto *tcf_chain_tp_find(struct tcf_chain *chain,
@@ -1533,7 +1548,12 @@ static struct tcf_proto *tcf_chain_tp_find(struct tcf_chain *chain,
}
}
chain_info->pprev = pprev;
- chain_info->next = tp ? tp->next : NULL;
+ if (tp) {
+ chain_info->next = tp->next;
+ tcf_proto_get(tp);
+ } else {
+ chain_info->next = NULL;
+ }
return tp;
}
@@ -1691,6 +1711,7 @@ static int tc_new_tfilter(struct sk_buff *skb, struct nlmsghdr *n,
prio = TC_H_MAJ(t->tcm_info);
prio_allocate = false;
parent = t->tcm_parent;
+ tp = NULL;
cl = 0;
if (prio == 0) {
@@ -1808,6 +1829,12 @@ static int tc_new_tfilter(struct sk_buff *skb, struct nlmsghdr *n,
errout:
if (chain)
tcf_chain_put(chain);
+ if (chain) {
+ if (tp && !IS_ERR(tp))
+ tcf_proto_put(tp, NULL);
+ if (!tp_created)
+ tcf_chain_put(chain);
+ }
tcf_block_release(q, block);
if (err == -EAGAIN)
/* Replay the request. */
@@ -1938,8 +1965,11 @@ static int tc_del_tfilter(struct sk_buff *skb, struct nlmsghdr *n,
}
errout:
- if (chain)
+ if (chain) {
+ if (tp && !IS_ERR(tp))
+ tcf_proto_put(tp, NULL);
tcf_chain_put(chain);
+ }
tcf_block_release(q, block);
return err;
@@ -2030,8 +2060,11 @@ static int tc_get_tfilter(struct sk_buff *skb, struct nlmsghdr *n,
}
errout:
- if (chain)
+ if (chain) {
+ if (tp && !IS_ERR(tp))
+ tcf_proto_put(tp, NULL);
tcf_chain_put(chain);
+ }
tcf_block_release(q, block);
return err;
}
--
2.13.6
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