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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@mellanox.com>
Acked-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
alistair/sunxi64-5.4-dsi
Vlad Buslov 2019-08-26 16:44:57 +03:00 committed by David S. Miller
parent 0846e1616f
commit 4f8116c850
2 changed files with 38 additions and 9 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
include/net/sch_generic.h
View File

@ -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;

45
net/sched/cls_api.c
View File

@ -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);