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net: sched: use reference counting for tcf blocks on rules update

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In order to remove dependency on rtnl lock on rules update path, always
take reference to block while using it on rules update path. Change
tcf_block_get() error handling to properly release block with reference
counting, instead of just destroying it, in order to accommodate potential
concurrent users.

Signed-off-by: Vlad Buslov <vladbu@mellanox.com>
Acked-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Vlad Buslov 2018-09-24 19:22:58 +03:00 committed by David S. Miller
parent 0607e43994
commit 787ce6d02d
1 changed files with 21 additions and 17 deletions
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38
net/sched/cls_api.c
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@ -622,7 +622,7 @@ static struct tcf_block *tcf_block_find(struct net *net, struct Qdisc **q,
int err = 0;
if (ifindex == TCM_IFINDEX_MAGIC_BLOCK) {
block = tcf_block_lookup(net, block_index);
block = tcf_block_refcnt_get(net, block_index);
if (!block) {
NL_SET_ERR_MSG(extack, "Block of given index was not found");
return ERR_PTR(-EINVAL);
@ -702,6 +702,14 @@ static struct tcf_block *tcf_block_find(struct net *net, struct Qdisc **q,
err = -EOPNOTSUPP;
goto errout_qdisc;
}
/* Always take reference to block in order to support execution
* of rules update path of cls API without rtnl lock. Caller
* must release block when it is finished using it. 'if' block
* of this conditional obtain reference to block by calling
* tcf_block_refcnt_get().
*/
refcount_inc(&block->refcnt);
}
return block;
@ -716,6 +724,9 @@ errout_qdisc:
static void tcf_block_release(struct Qdisc *q, struct tcf_block *block)
{
if (!IS_ERR_OR_NULL(block))
tcf_block_refcnt_put(block);
if (q)
qdisc_put(q);
}
@ -785,21 +796,16 @@ int tcf_block_get_ext(struct tcf_block **p_block, struct Qdisc *q,
{
struct net *net = qdisc_net(q);
struct tcf_block *block = NULL;
bool created = false;
int err;
if (ei->block_index) {
if (ei->block_index)
/* block_index not 0 means the shared block is requested */
block = tcf_block_lookup(net, ei->block_index);
if (block)
refcount_inc(&block->refcnt);
}
block = tcf_block_refcnt_get(net, ei->block_index);
if (!block) {
block = tcf_block_create(net, q, ei->block_index, extack);
if (IS_ERR(block))
return PTR_ERR(block);
created = true;
if (tcf_block_shared(block)) {
err = tcf_block_insert(block, net, extack);
if (err)
@ -829,14 +835,8 @@ err_block_offload_bind:
err_chain0_head_change_cb_add:
tcf_block_owner_del(block, q, ei->binder_type);
err_block_owner_add:
if (created) {
if (tcf_block_shared(block))
tcf_block_remove(block, net);
err_block_insert:
kfree_rcu(block, rcu);
} else {
refcount_dec(&block->refcnt);
}
tcf_block_refcnt_put(block);
return err;
}
EXPORT_SYMBOL(tcf_block_get_ext);
@ -1730,7 +1730,7 @@ static int tc_dump_tfilter(struct sk_buff *skb, struct netlink_callback *cb)
return err;
if (tcm->tcm_ifindex == TCM_IFINDEX_MAGIC_BLOCK) {
block = tcf_block_lookup(net, tcm->tcm_block_index);
block = tcf_block_refcnt_get(net, tcm->tcm_block_index);
if (!block)
goto out;
/* If we work with block index, q is NULL and parent value
@ -1789,6 +1789,8 @@ static int tc_dump_tfilter(struct sk_buff *skb, struct netlink_callback *cb)
}
}
if (tcm->tcm_ifindex == TCM_IFINDEX_MAGIC_BLOCK)
tcf_block_refcnt_put(block);
cb->args[0] = index;
out:
@ -2055,7 +2057,7 @@ static int tc_dump_chain(struct sk_buff *skb, struct netlink_callback *cb)
return err;
if (tcm->tcm_ifindex == TCM_IFINDEX_MAGIC_BLOCK) {
block = tcf_block_lookup(net, tcm->tcm_block_index);
block = tcf_block_refcnt_get(net, tcm->tcm_block_index);
if (!block)
goto out;
/* If we work with block index, q is NULL and parent value
@ -2122,6 +2124,8 @@ static int tc_dump_chain(struct sk_buff *skb, struct netlink_callback *cb)
index++;
}
if (tcm->tcm_ifindex == TCM_IFINDEX_MAGIC_BLOCK)
tcf_block_refcnt_put(block);
cb->args[0] = index;
out: