net: core: decouple ifalias get/set from rtnl lock
Subsystems (2)
PATCH v3 1/1 net: core: decouple ifalias get/set from rtnl lock
Device alias can be set by either rtnetlink (rtnl is held) or sysfs.
rtnetlink hold the rtnl mutex, sysfs acquires it for this purpose. Add an extra mutex for it and use rcu to protect concurrent accesses.
This allows the sysfs path to not take rtnl and would later allow to not hold it when dumping ifalias.
Based on suggestion from Eric Dumazet.
---
Changes since v2:
- use rcu_swap_protected
Change since v1:
- don't use a sequence lock, instead use kmalloc+kfree_rcu
- add comment for dev_get_alias
- add comment why we use kfree and not kfree_rcu to free dev->alias during netdevice destruction
include/linux/netdevice.h | 8 +++++++- net/core/dev.c | 52 +++++++++++++++++++++++++++++++++++------------ net/core/net-sysfs.c | 17 ++++++++-------- net/core/rtnetlink.c | 13 ++++++++++-- 4 files changed, 65 insertions(+), 25 deletions(-)
include/linux/netdevice.h +7 -1
@@ -826,6 +826,11 @@ struct xfrmdev_ops { };#endif +struct dev_ifalias { +struct rcu_head rcuhead; +char ifalias[]; +}; +/* * This structure defines the management hooks for network devices. * The following hooks can be defined; unless noted otherwise, they are
@@ -1632,7 +1637,7 @@ enum netdev_priv_flags {struct net_device {char name[IFNAMSIZ ];struct hlist_node name_hlist; -char *ifalias; +struct dev_ifalias __rcu *ifalias;/* * I/O specific fields * FIXME: Merge these and struct ifmap into one
@@ -3275,6 +3280,7 @@ void __dev_notify_flags(struct net_device *, unsigned int old_flags, unsigned int gchanges);int dev_change_name (struct net_device *,const char *);int dev_set_alias (struct net_device *,const char *,size_t ); +int dev_get_alias (const struct net_device *,char *,size_t );int dev_change_net_namespace (struct net_device *,struct net *,const char *);int __dev_set_mtu (struct net_device *,int );int dev_set_mtu (struct net_device *,int );
net/core/dev.c +39 -13
74 lines not on this page · raw message
net/core/net-sysfs.c +8 -9
@@ -391,10 +391,7 @@ static ssize_t ifalias_store(struct device *dev, struct device_attribute *attr,if (len >0 && buf[len -1 ] =='\n' ) --count; -if (!rtnl_trylock ()) -return restart_syscall (); ret =dev_set_alias (netdev, buf, count); -rtnl_unlock ();return ret <0 ? ret : len; }
@@ -403,13 +400,12 @@ static ssize_t ifalias_show(struct device *dev, struct device_attribute *attr, char *buf) { const struct net_device *netdev = to_net_dev(dev); +char tmp[IFALIASZ ];ssize_t ret =0 ; -if (!rtnl_trylock ()) -return restart_syscall (); -if (netdev->ifalias) - ret =sprintf (buf,"%s\n" , netdev->ifalias); -rtnl_unlock (); + ret =dev_get_alias (netdev, tmp,sizeof (tmp)); +if (ret >0 ) + ret =sprintf (buf,"%s\n" , tmp);return ret; }static DEVICE_ATTR_RW (ifalias);
@@ -1488,7 +1484,10 @@ static void netdev_release(struct device *d)BUG_ON (dev->reg_state !=NETREG_RELEASED ); -kfree (dev->ifalias); +/* no need to wait for rcu grace period: +* device is dead and about to be freed. +*/ +kfree (rcu_access_pointer (dev->ifalias));netdev_freemem (dev); }
net/core/rtnetlink.c +11 -2
@@ -1366,6 +1366,16 @@ static int nla_put_iflink(struct sk_buff *skb, const struct net_device *dev)return nla_put_u32 (skb,IFLA_LINK , ifindex); } +static noinline_for_stack int nla_put_ifalias(struct sk_buff *skb, +struct net_device *dev) +{ +char buf[IFALIASZ ]; +int ret; + + ret =dev_get_alias (dev, buf,sizeof (buf)); +return ret >0 ?nla_put_string (skb,IFLA_IFALIAS , buf) :0 ; +} +static int rtnl_fill_link_netnsid (struct sk_buff *skb,const struct net_device *dev) {
@@ -1425,8 +1435,7 @@ static int rtnl_fill_ifinfo(struct sk_buff *skb, struct net_device *dev,nla_put_u8 (skb,IFLA_CARRIER ,netif_carrier_ok (dev)) || (dev->qdisc &&nla_put_string (skb,IFLA_QDISC , dev->qdisc->ops->id)) || - (dev->ifalias && -nla_put_string (skb,IFLA_IFALIAS , dev->ifalias)) || +nla_put_ifalias (skb, dev) ||nla_put_u32 (skb,IFLA_CARRIER_CHANGES ,atomic_read (&dev->carrier_changes)) || nla_put_u8(skb, IFLA_PROTO_DOWN, dev->proto_down))
Signature · 1 line
2.13.6
From: Florian Westphal <[email protected]>
Date: Mon, 2 Oct 2017 23:50:05 +0200
Quoted 11 lines
Device alias can be set by either rtnetlink (rtnl is held) or sysfs.
rtnetlink hold the rtnl mutex, sysfs acquires it for this purpose. Add an extra mutex for it and use rcu to protect concurrent accesses.
This allows the sysfs path to not take rtnl and would later allow to not hold it when dumping ifalias.
Based on suggestion from Eric Dumazet.
Signed-off-by Florian Westphal <[email protected]>
Applied, thanks Florian.