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net: core: rcu-ify rtnl af_ops
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rtnl af_ops currently rely on rtnl mutex: unregister (called from module
exit functions) takes the rtnl mutex and all users that do af_ops lookup
also take the rtnl mutex. IOW, parallel rmmod will block until doit()
callback is done.

As none of the af_ops implementation sleep we can use rcu instead.

doit functions that need the af_ops can now use rcu instead of the
rtnl mutex provided the mutex isn't needed for other reasons.

Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: David S. Miller <davem@davemloft.net>
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Florian Westphal authored and David S. Miller committed Oct 16, 2017
1 parent 070cbf5 commit 5fa85a0
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Showing 2 changed files with 48 additions and 18 deletions.
62 changes: 46 additions & 16 deletions net/core/rtnetlink.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -453,7 +453,7 @@ static const struct rtnl_af_ops *rtnl_af_lookup(const int family)
{
const struct rtnl_af_ops *ops;

list_for_each_entry(ops, &rtnl_af_ops, list) {
list_for_each_entry_rcu(ops, &rtnl_af_ops, list) {
if (ops->family == family)
return ops;
}
Expand All @@ -470,7 +470,7 @@ static const struct rtnl_af_ops *rtnl_af_lookup(const int family)
void rtnl_af_register(struct rtnl_af_ops *ops)
{
rtnl_lock();
list_add_tail(&ops->list, &rtnl_af_ops);
list_add_tail_rcu(&ops->list, &rtnl_af_ops);
rtnl_unlock();
}
EXPORT_SYMBOL_GPL(rtnl_af_register);
Expand All @@ -482,8 +482,10 @@ EXPORT_SYMBOL_GPL(rtnl_af_register);
void rtnl_af_unregister(struct rtnl_af_ops *ops)
{
rtnl_lock();
list_del(&ops->list);
list_del_rcu(&ops->list);
rtnl_unlock();

synchronize_rcu();
}
EXPORT_SYMBOL_GPL(rtnl_af_unregister);

Expand All @@ -496,13 +498,15 @@ static size_t rtnl_link_get_af_size(const struct net_device *dev,
/* IFLA_AF_SPEC */
size = nla_total_size(sizeof(struct nlattr));

list_for_each_entry(af_ops, &rtnl_af_ops, list) {
rcu_read_lock();
list_for_each_entry_rcu(af_ops, &rtnl_af_ops, list) {
if (af_ops->get_link_af_size) {
/* AF_* + nested data */
size += nla_total_size(sizeof(struct nlattr)) +
af_ops->get_link_af_size(dev, ext_filter_mask);
}
}
rcu_read_unlock();

return size;
}
Expand Down Expand Up @@ -1393,7 +1397,7 @@ static int rtnl_fill_link_af(struct sk_buff *skb,
if (!af_spec)
return -EMSGSIZE;

list_for_each_entry(af_ops, &rtnl_af_ops, list) {
list_for_each_entry_rcu(af_ops, &rtnl_af_ops, list) {
struct nlattr *af;
int err;

Expand Down Expand Up @@ -1516,12 +1520,16 @@ static int rtnl_fill_ifinfo(struct sk_buff *skb, struct net_device *dev,
nla_put_s32(skb, IFLA_NEW_NETNSID, *new_nsid) < 0)
goto nla_put_failure;

rcu_read_lock();
if (rtnl_fill_link_af(skb, dev, ext_filter_mask))
goto nla_put_failure;
goto nla_put_failure_rcu;
rcu_read_unlock();

nlmsg_end(skb, nlh);
return 0;

nla_put_failure_rcu:
rcu_read_unlock();
nla_put_failure:
nlmsg_cancel(skb, nlh);
return -EMSGSIZE;
Expand Down Expand Up @@ -1783,17 +1791,27 @@ static int validate_linkmsg(struct net_device *dev, struct nlattr *tb[])
nla_for_each_nested(af, tb[IFLA_AF_SPEC], rem) {
const struct rtnl_af_ops *af_ops;

if (!(af_ops = rtnl_af_lookup(nla_type(af))))
rcu_read_lock();
af_ops = rtnl_af_lookup(nla_type(af));
if (!af_ops) {
rcu_read_unlock();
return -EAFNOSUPPORT;
}

if (!af_ops->set_link_af)
if (!af_ops->set_link_af) {
rcu_read_unlock();
return -EOPNOTSUPP;
}

if (af_ops->validate_link_af) {
err = af_ops->validate_link_af(dev, af);
if (err < 0)
if (err < 0) {
rcu_read_unlock();
return err;
}
}

rcu_read_unlock();
}
}

Expand Down Expand Up @@ -2251,13 +2269,18 @@ static int do_setlink(const struct sk_buff *skb,
nla_for_each_nested(af, tb[IFLA_AF_SPEC], rem) {
const struct rtnl_af_ops *af_ops;

rcu_read_lock();

if (!(af_ops = rtnl_af_lookup(nla_type(af))))
BUG();

err = af_ops->set_link_af(dev, af);
if (err < 0)
if (err < 0) {
rcu_read_unlock();
goto errout;
}

rcu_read_unlock();
status |= DO_SETLINK_NOTIFY;
}
}
Expand Down Expand Up @@ -4004,25 +4027,30 @@ static int rtnl_fill_statsinfo(struct sk_buff *skb, struct net_device *dev,
if (!attr)
goto nla_put_failure;

list_for_each_entry(af_ops, &rtnl_af_ops, list) {
rcu_read_lock();
list_for_each_entry_rcu(af_ops, &rtnl_af_ops, list) {
if (af_ops->fill_stats_af) {
struct nlattr *af;
int err;

af = nla_nest_start(skb, af_ops->family);
if (!af)
if (!af) {
rcu_read_unlock();
goto nla_put_failure;

}
err = af_ops->fill_stats_af(skb, dev);

if (err == -ENODATA)
if (err == -ENODATA) {
nla_nest_cancel(skb, af);
else if (err < 0)
} else if (err < 0) {
rcu_read_unlock();
goto nla_put_failure;
}

nla_nest_end(skb, af);
}
}
rcu_read_unlock();

nla_nest_end(skb, attr);

Expand Down Expand Up @@ -4091,7 +4119,8 @@ static size_t if_nlmsg_stats_size(const struct net_device *dev,
/* for IFLA_STATS_AF_SPEC */
size += nla_total_size(0);

list_for_each_entry(af_ops, &rtnl_af_ops, list) {
rcu_read_lock();
list_for_each_entry_rcu(af_ops, &rtnl_af_ops, list) {
if (af_ops->get_stats_af_size) {
size += nla_total_size(
af_ops->get_stats_af_size(dev));
Expand All @@ -4100,6 +4129,7 @@ static size_t if_nlmsg_stats_size(const struct net_device *dev,
size += nla_total_size(0);
}
}
rcu_read_unlock();
}

return size;
Expand Down
4 changes: 2 additions & 2 deletions net/ipv4/devinet.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -1757,7 +1757,7 @@ static int inet_validate_link_af(const struct net_device *dev,
struct nlattr *a, *tb[IFLA_INET_MAX+1];
int err, rem;

if (dev && !__in_dev_get_rtnl(dev))
if (dev && !__in_dev_get_rcu(dev))
return -EAFNOSUPPORT;

err = nla_parse_nested(tb, IFLA_INET_MAX, nla, inet_af_policy, NULL);
Expand All @@ -1781,7 +1781,7 @@ static int inet_validate_link_af(const struct net_device *dev,

static int inet_set_link_af(struct net_device *dev, const struct nlattr *nla)
{
struct in_device *in_dev = __in_dev_get_rtnl(dev);
struct in_device *in_dev = __in_dev_get_rcu(dev);
struct nlattr *a, *tb[IFLA_INET_MAX+1];
int rem;

Expand Down

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