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Date: Fri, 23 Aug 2019 21:50:47 +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, jakub.kicinski@...ronome.com,
pablo@...filter.org, Vlad Buslov <vladbu@...lanox.com>
Subject: [PATCH net-next v2 01/10] net: sched: protect block offload-related fields with rw_semaphore
In order to remove dependency on rtnl lock, extend tcf_block with 'cb_lock'
rwsem and use it to protect flow_block->cb_list and related counters from
concurrent modification. The lock is taken in read mode for read-only
traversal of cb_list in tc_setup_cb_call() and write mode in all other
cases. This approach ensures that:
- cb_list is not changed concurrently while filters is being offloaded on
block.
- block->nooffloaddevcnt is checked while holding the lock in read mode,
but is only changed by bind/unbind code when holding the cb_lock in write
mode to prevent concurrent modification.
Signed-off-by: Vlad Buslov <vladbu@...lanox.com>
---
Changes from V1 to V2:
- Rename 'errout' label to 'err_unlock'.
include/net/sch_generic.h | 2 ++
net/sched/cls_api.c | 45 +++++++++++++++++++++++++++++++--------
2 files changed, 38 insertions(+), 9 deletions(-)
diff --git a/include/net/sch_generic.h b/include/net/sch_generic.h
index d9f359af0b93..a3eaf5f9d28f 100644
--- a/include/net/sch_generic.h
+++ b/include/net/sch_generic.h
@@ -13,6 +13,7 @@
#include <linux/refcount.h>
#include <linux/workqueue.h>
#include <linux/mutex.h>
+#include <linux/rwsem.h>
#include <net/gen_stats.h>
#include <net/rtnetlink.h>
#include <net/flow_offload.h>
@@ -396,6 +397,7 @@ struct tcf_block {
refcount_t refcnt;
struct net *net;
struct Qdisc *q;
+ struct rw_semaphore cb_lock; /* protects cb_list and offload counters */
struct flow_block flow_block;
struct list_head owner_list;
bool keep_dst;
diff --git a/net/sched/cls_api.c b/net/sched/cls_api.c
index e0d8b456e9f5..959b7ca1ca02 100644
--- a/net/sched/cls_api.c
+++ b/net/sched/cls_api.c
@@ -568,9 +568,11 @@ static void tc_indr_block_ing_cmd(struct net_device *dev,
bo.block = &block->flow_block;
+ down_write(&block->cb_lock);
cb(dev, cb_priv, TC_SETUP_BLOCK, &bo);
tcf_block_setup(block, &bo);
+ up_write(&block->cb_lock);
}
static struct tcf_block *tc_dev_ingress_block(struct net_device *dev)
@@ -661,6 +663,7 @@ static int tcf_block_offload_bind(struct tcf_block *block, struct Qdisc *q,
struct net_device *dev = q->dev_queue->dev;
int err;
+ down_write(&block->cb_lock);
if (!dev->netdev_ops->ndo_setup_tc)
goto no_offload_dev_inc;
@@ -669,24 +672,31 @@ static int tcf_block_offload_bind(struct tcf_block *block, struct Qdisc *q,
*/
if (!tc_can_offload(dev) && tcf_block_offload_in_use(block)) {
NL_SET_ERR_MSG(extack, "Bind to offloaded block failed as dev has offload disabled");
- return -EOPNOTSUPP;
+ err = -EOPNOTSUPP;
+ goto err_unlock;
}
err = tcf_block_offload_cmd(block, dev, ei, FLOW_BLOCK_BIND, extack);
if (err == -EOPNOTSUPP)
goto no_offload_dev_inc;
if (err)
- return err;
+ goto err_unlock;
tc_indr_block_call(block, dev, ei, FLOW_BLOCK_BIND, extack);
+ up_write(&block->cb_lock);
return 0;
no_offload_dev_inc:
- if (tcf_block_offload_in_use(block))
- return -EOPNOTSUPP;
+ if (tcf_block_offload_in_use(block)) {
+ err = -EOPNOTSUPP;
+ goto err_unlock;
+ }
+ err = 0;
block->nooffloaddevcnt++;
tc_indr_block_call(block, dev, ei, FLOW_BLOCK_BIND, extack);
- return 0;
+err_unlock:
+ up_write(&block->cb_lock);
+ return err;
}
static void tcf_block_offload_unbind(struct tcf_block *block, struct Qdisc *q,
@@ -695,6 +705,7 @@ static void tcf_block_offload_unbind(struct tcf_block *block, struct Qdisc *q,
struct net_device *dev = q->dev_queue->dev;
int err;
+ down_write(&block->cb_lock);
tc_indr_block_call(block, dev, ei, FLOW_BLOCK_UNBIND, NULL);
if (!dev->netdev_ops->ndo_setup_tc)
@@ -702,10 +713,12 @@ static void tcf_block_offload_unbind(struct tcf_block *block, struct Qdisc *q,
err = tcf_block_offload_cmd(block, dev, ei, FLOW_BLOCK_UNBIND, NULL);
if (err == -EOPNOTSUPP)
goto no_offload_dev_dec;
+ up_write(&block->cb_lock);
return;
no_offload_dev_dec:
WARN_ON(block->nooffloaddevcnt-- == 0);
+ up_write(&block->cb_lock);
}
static int
@@ -820,6 +833,7 @@ static struct tcf_block *tcf_block_create(struct net *net, struct Qdisc *q,
return ERR_PTR(-ENOMEM);
}
mutex_init(&block->lock);
+ init_rwsem(&block->cb_lock);
flow_block_init(&block->flow_block);
INIT_LIST_HEAD(&block->chain_list);
INIT_LIST_HEAD(&block->owner_list);
@@ -1355,6 +1369,8 @@ tcf_block_playback_offloads(struct tcf_block *block, flow_setup_cb_t *cb,
struct tcf_proto *tp, *tp_prev;
int err;
+ lockdep_assert_held(&block->cb_lock);
+
for (chain = __tcf_get_next_chain(block, NULL);
chain;
chain_prev = chain,
@@ -1393,6 +1409,8 @@ static int tcf_block_bind(struct tcf_block *block,
struct flow_block_cb *block_cb, *next;
int err, i = 0;
+ lockdep_assert_held(&block->cb_lock);
+
list_for_each_entry(block_cb, &bo->cb_list, list) {
err = tcf_block_playback_offloads(block, block_cb->cb,
block_cb->cb_priv, true,
@@ -1427,6 +1445,8 @@ static void tcf_block_unbind(struct tcf_block *block,
{
struct flow_block_cb *block_cb, *next;
+ lockdep_assert_held(&block->cb_lock);
+
list_for_each_entry_safe(block_cb, next, &bo->cb_list, list) {
tcf_block_playback_offloads(block, block_cb->cb,
block_cb->cb_priv, false,
@@ -2987,19 +3007,26 @@ int tc_setup_cb_call(struct tcf_block *block, enum tc_setup_type type,
int ok_count = 0;
int err;
+ down_read(&block->cb_lock);
/* Make sure all netdevs sharing this block are offload-capable. */
- if (block->nooffloaddevcnt && err_stop)
- return -EOPNOTSUPP;
+ if (block->nooffloaddevcnt && err_stop) {
+ ok_count = -EOPNOTSUPP;
+ goto err_unlock;
+ }
list_for_each_entry(block_cb, &block->flow_block.cb_list, list) {
err = block_cb->cb(type, type_data, block_cb->cb_priv);
if (err) {
- if (err_stop)
- return err;
+ if (err_stop) {
+ ok_count = err;
+ goto err_unlock;
+ }
} else {
ok_count++;
}
}
+err_unlock:
+ up_read(&block->cb_lock);
return ok_count;
}
EXPORT_SYMBOL(tc_setup_cb_call);
--
2.21.0
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