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net_sched: remove tc class reference counting

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For TC classes, their ->get() and ->put() are always paired, and the
reference counting is completely useless, because:

1) For class modification and dumping paths, we already hold RTNL lock,
   so all of these ->get(),->change(),->put() are atomic.

2) For filter bindiing/unbinding, we use other reference counter than
   this one, and they should have RTNL lock too.

3) For ->qlen_notify(), it is special because it is called on ->enqueue()
   path, but we already hold qdisc tree lock there, and we hold this
   tree lock when graft or delete the class too, so it should not be gone
   or changed until we release the tree lock.

Therefore, this patch removes ->get() and ->put(), but:

1) Adds a new ->find() to find the pointer to a class by classid, no
   refcnt.

2) Move the original class destroy upon the last refcnt into ->delete(),
   right after releasing tree lock. This is fine because the class is
   already removed from hash when holding the lock.

For those who also use ->put() as ->unbind(), just rename them to reflect
this change.

Cc: Jamal Hadi Salim <jhs@mojatatu.com>
Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
Acked-by: Jiri Pirko <jiri@mellanox.com>
Acked-by: Jamal Hadi Salim <jhs@mojatatu.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
WANG Cong
2017-08-24 16:51:29 -07:00
committed by David S. Miller
parent 14546ba1e5
commit 143976ce99
21 changed files with 106 additions and 262 deletions
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17
net/sched/cls_api.c
View File

@@ -586,7 +586,7 @@ replay:
/* Do we search for filter, attached to class? */
if (TC_H_MIN(parent)) {
cl = cops->get(q, parent);
cl = cops->find(q, parent);
if (cl == 0)
return -ENOENT;
}
@@ -716,8 +716,6 @@ replay:
errout:
if (chain)
tcf_chain_put(chain);
if (cl)
cops->put(q, cl);
if (err == -EAGAIN)
/* Replay the request. */
goto replay;
@@ -822,17 +820,17 @@ static int tc_dump_tfilter(struct sk_buff *skb, struct netlink_callback *cb)
goto out;
cops = q->ops->cl_ops;
if (!cops)
goto errout;
goto out;
if (!cops->tcf_block)
goto errout;
goto out;
if (TC_H_MIN(tcm->tcm_parent)) {
cl = cops->get(q, tcm->tcm_parent);
cl = cops->find(q, tcm->tcm_parent);
if (cl == 0)
goto errout;
goto out;
}
block = cops->tcf_block(q, cl);
if (!block)
goto errout;
goto out;
index_start = cb->args[0];
index = 0;
@@ -847,9 +845,6 @@ static int tc_dump_tfilter(struct sk_buff *skb, struct netlink_callback *cb)
cb->args[0] = index;
errout:
if (cl)
cops->put(q, cl);
out:
return skb->len;
}