[PATCH net-next v4 0/4] rtnetlink: preparation patches for further rtnl lock pushdown/removal

[PATCH net-next v4 0/4] rtnetlink: preparation patches for further rtnl lock pushdown/removal

[Florian Westphal]

Patches split large rtnl_fill_ifinfo into smaller chunks
to better see which parts

1. require rtnl
2. do not require it at all
3. rely on rtnl locking now but could be converted

Changes since v3:

I dropped the 'ifalias' patch, I have a change to decouple ifalias and
rtnl mutex, I will send it once this series has been merged.

[PATCH net-next v4 1/4] rtnetlink: add helper to put master and link ifindexes

[Florian Westphal]

rtnl_fill_ifinfo currently requires caller to hold the rtnl mutex.
Unfortunately the function is quite large which makes it harder to see
which spots require the lock, which spots assume it and which ones could
do without.

Add helpers to factor out the ifindex dumping, one can use rcu to avoid
rtnl dependency.

Reviewed-by: David Ahern <dsahern@gmail.com>
Signed-off-by: Florian Westphal <fw@strlen.de>
---
 No changes in v4.

 net/core/rtnetlink.c | 32 +++++++++++++++++++++++++++-----
 1 file changed, 27 insertions(+), 5 deletions(-)

diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
index a78fd61da0ec..c801212ee40e 100644
--- a/net/core/rtnetlink.c
+++ b/net/core/rtnetlink.c
@@ -1307,6 +1307,31 @@ static u32 rtnl_get_event(unsigned long event)
 	return rtnl_event_type;
 }
 
+static int put_master_ifindex(struct sk_buff *skb, struct net_device *dev)
+{
+	const struct net_device *upper_dev;
+	int ret = 0;
+
+	rcu_read_lock();
+
+	upper_dev = netdev_master_upper_dev_get_rcu(dev);
+	if (upper_dev)
+		ret = nla_put_u32(skb, IFLA_MASTER, upper_dev->ifindex);
+
+	rcu_read_unlock();
+	return ret;
+}
+
+static int nla_put_iflink(struct sk_buff *skb, const struct net_device *dev)
+{
+	int ifindex = dev_get_iflink(dev);
+
+	if (dev->ifindex == ifindex)
+		return 0;
+
+	return nla_put_u32(skb, IFLA_LINK, ifindex);
+}
+
 static int rtnl_fill_ifinfo(struct sk_buff *skb, struct net_device *dev,
 			    int type, u32 pid, u32 seq, u32 change,
 			    unsigned int flags, u32 ext_filter_mask,
@@ -1316,7 +1341,6 @@ static int rtnl_fill_ifinfo(struct sk_buff *skb, struct net_device *dev,
 	struct nlmsghdr *nlh;
 	struct nlattr *af_spec;
 	struct rtnl_af_ops *af_ops;
-	struct net_device *upper_dev = netdev_master_upper_dev_get(dev);
 
 	ASSERT_RTNL();
 	nlh = nlmsg_put(skb, pid, seq, type, sizeof(*ifm), flags);
@@ -1345,10 +1369,8 @@ static int rtnl_fill_ifinfo(struct sk_buff *skb, struct net_device *dev,
 #ifdef CONFIG_RPS
 	    nla_put_u32(skb, IFLA_NUM_RX_QUEUES, dev->num_rx_queues) ||
 #endif
-	    (dev->ifindex != dev_get_iflink(dev) &&
-	     nla_put_u32(skb, IFLA_LINK, dev_get_iflink(dev))) ||
-	    (upper_dev &&
-	     nla_put_u32(skb, IFLA_MASTER, upper_dev->ifindex)) ||
+	    nla_put_iflink(skb, dev) ||
+	    put_master_ifindex(skb, dev) ||
 	    nla_put_u8(skb, IFLA_CARRIER, netif_carrier_ok(dev)) ||
 	    (dev->qdisc &&
 	     nla_put_string(skb, IFLA_QDISC, dev->qdisc->ops->id)) ||
-- 
2.13.5

[PATCH net-next v4 2/4] rtnetlink: add helpers to dump vf information

[Florian Westphal]

similar to earlier patches, split out more parts of this function to
better see what is happening and where we assume rtnl is locked.

Reviewed-by: David Ahern <dsahern@gmail.com>
Signed-off-by: Florian Westphal <fw@strlen.de>
---
 No changes in v4.

 net/core/rtnetlink.c | 50 +++++++++++++++++++++++++++++++-------------------
 1 file changed, 31 insertions(+), 19 deletions(-)

diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
index c801212ee40e..d504e78cd01f 100644
--- a/net/core/rtnetlink.c
+++ b/net/core/rtnetlink.c
@@ -1211,6 +1211,36 @@ static noinline_for_stack int rtnl_fill_vfinfo(struct sk_buff *skb,
 	return -EMSGSIZE;
 }
 
+static noinline_for_stack int rtnl_fill_vf(struct sk_buff *skb,
+					   struct net_device *dev,
+					   u32 ext_filter_mask)
+{
+	struct nlattr *vfinfo;
+	int i, num_vfs;
+
+	if (!dev->dev.parent || ((ext_filter_mask & RTEXT_FILTER_VF) == 0))
+		return 0;
+
+	num_vfs = dev_num_vf(dev->dev.parent);
+	if (nla_put_u32(skb, IFLA_NUM_VF, num_vfs))
+		return -EMSGSIZE;
+
+	if (!dev->netdev_ops->ndo_get_vf_config)
+		return 0;
+
+	vfinfo = nla_nest_start(skb, IFLA_VFINFO_LIST);
+	if (!vfinfo)
+		return -EMSGSIZE;
+
+	for (i = 0; i < num_vfs; i++) {
+		if (rtnl_fill_vfinfo(skb, dev, i, vfinfo))
+			return -EMSGSIZE;
+	}
+
+	nla_nest_end(skb, vfinfo);
+	return 0;
+}
+
 static int rtnl_fill_link_ifmap(struct sk_buff *skb, struct net_device *dev)
 {
 	struct rtnl_link_ifmap map;
@@ -1407,27 +1437,9 @@ static int rtnl_fill_ifinfo(struct sk_buff *skb, struct net_device *dev,
 	if (rtnl_fill_stats(skb, dev))
 		goto nla_put_failure;
 
-	if (dev->dev.parent && (ext_filter_mask & RTEXT_FILTER_VF) &&
-	    nla_put_u32(skb, IFLA_NUM_VF, dev_num_vf(dev->dev.parent)))
+	if (rtnl_fill_vf(skb, dev, ext_filter_mask))
 		goto nla_put_failure;
 
-	if (dev->netdev_ops->ndo_get_vf_config && dev->dev.parent &&
-	    ext_filter_mask & RTEXT_FILTER_VF) {
-		int i;
-		struct nlattr *vfinfo;
-		int num_vfs = dev_num_vf(dev->dev.parent);
-
-		vfinfo = nla_nest_start(skb, IFLA_VFINFO_LIST);
-		if (!vfinfo)
-			goto nla_put_failure;
-		for (i = 0; i < num_vfs; i++) {
-			if (rtnl_fill_vfinfo(skb, dev, i, vfinfo))
-				goto nla_put_failure;
-		}
-
-		nla_nest_end(skb, vfinfo);
-	}
-
 	if (rtnl_port_fill(skb, dev, ext_filter_mask))
 		goto nla_put_failure;
 
-- 
2.13.5

[PATCH net-next v4 3/4] rtnetlink: add helpers to dump netnsid information

[Florian Westphal]

Reviewed-by: David Ahern <dsahern@gmail.com>
Signed-off-by: Florian Westphal <fw@strlen.de>
---
 No changes in v4.

 net/core/rtnetlink.c | 30 +++++++++++++++++++-----------
 1 file changed, 19 insertions(+), 11 deletions(-)

diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
index d504e78cd01f..d524609c587c 100644
--- a/net/core/rtnetlink.c
+++ b/net/core/rtnetlink.c
@@ -1362,6 +1362,23 @@ static int nla_put_iflink(struct sk_buff *skb, const struct net_device *dev)
 	return nla_put_u32(skb, IFLA_LINK, ifindex);
 }
 
+static int rtnl_fill_link_netnsid(struct sk_buff *skb,
+				  const struct net_device *dev)
+{
+	if (dev->rtnl_link_ops && dev->rtnl_link_ops->get_link_net) {
+		struct net *link_net = dev->rtnl_link_ops->get_link_net(dev);
+
+		if (!net_eq(dev_net(dev), link_net)) {
+			int id = peernet2id_alloc(dev_net(dev), link_net);
+
+			if (nla_put_s32(skb, IFLA_LINK_NETNSID, id))
+				return -EMSGSIZE;
+		}
+	}
+
+	return 0;
+}
+
 static int rtnl_fill_ifinfo(struct sk_buff *skb, struct net_device *dev,
 			    int type, u32 pid, u32 seq, u32 change,
 			    unsigned int flags, u32 ext_filter_mask,
@@ -1451,17 +1468,8 @@ static int rtnl_fill_ifinfo(struct sk_buff *skb, struct net_device *dev,
 			goto nla_put_failure;
 	}
 
-	if (dev->rtnl_link_ops &&
-	    dev->rtnl_link_ops->get_link_net) {
-		struct net *link_net = dev->rtnl_link_ops->get_link_net(dev);
-
-		if (!net_eq(dev_net(dev), link_net)) {
-			int id = peernet2id_alloc(dev_net(dev), link_net);
-
-			if (nla_put_s32(skb, IFLA_LINK_NETNSID, id))
-				goto nla_put_failure;
-		}
-	}
+	if (rtnl_fill_link_netnsid(skb, dev))
+		goto nla_put_failure;
 
 	if (!(af_spec = nla_nest_start(skb, IFLA_AF_SPEC)))
 		goto nla_put_failure;
-- 
2.13.5

[PATCH net-next v4 4/4] rtnetlink: rtnl_have_link_slave_info doesn't need rtnl

[Florian Westphal]

it can be switched to rcu.

Reviewed-by: David Ahern <dsahern@gmail.com>
Signed-off-by: Florian Westphal <fw@strlen.de>
---
 No changes in v4.

 net/core/rtnetlink.c | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
index d524609c587c..e6955da0d58d 100644
--- a/net/core/rtnetlink.c
+++ b/net/core/rtnetlink.c
@@ -522,11 +522,15 @@ static size_t rtnl_link_get_af_size(const struct net_device *dev,
 static bool rtnl_have_link_slave_info(const struct net_device *dev)
 {
 	struct net_device *master_dev;
+	bool ret = false;
 
-	master_dev = netdev_master_upper_dev_get((struct net_device *) dev);
+	rcu_read_lock();
+
+	master_dev = netdev_master_upper_dev_get_rcu((struct net_device *)dev);
 	if (master_dev && master_dev->rtnl_link_ops)
-		return true;
-	return false;
+		ret = true;
+	rcu_read_unlock();
+	return ret;
 }
 
 static int rtnl_link_slave_info_fill(struct sk_buff *skb,
-- 
2.13.5

Re: [PATCH net-next v4 0/4] rtnetlink: preparation patches for further rtnl lock pushdown/removal

[David Miller]

From: Florian Westphal <fw@strlen.de>
Date: Tue, 26 Sep 2017 13:58:39 +0200

> Patches split large rtnl_fill_ifinfo into smaller chunks
> to better see which parts
> 
> 1. require rtnl
> 2. do not require it at all
> 3. rely on rtnl locking now but could be converted
> 
> Changes since v3:
> 
> I dropped the 'ifalias' patch, I have a change to decouple ifalias and
> rtnl mutex, I will send it once this series has been merged.

Series applied.