Subject: Re: [PATCH 1/2] net: add network priority cgroup infrastructure

From: John Fastabend <[email-masked]>
Date: Thu, 17 Nov 2011 03:25:58 -0800

On 11/16/2011 12:51 PM, Neil Horman wrote:
> This patch adds in the infrastructure code to create the network priority
> cgroup.  The cgroup, in addition to the standard processes file creates two
> control files:
> 
> 1) prioidx - This is a read-only file that exports the index of this cgroup.
> This is a value that is both arbitrary and unique to a cgroup in this subsystem,
> and is used to index the per-device priority map
> 
> 2) priomap - This is a writeable file.  On read it reports a table of 2-tuples
> <name:priority> where name is the name of a network interface and priority is
> indicates the priority assigned to frames egresessing on the named interface and
> originating from a pid in this cgroup
> 
> This cgroup allows for skb priority to be set prior to a root qdisc getting
> selected. This is benenficial for DCB enabled systems, in that it allows for any
> application to use dcb configured priorities so without application modification
> 
> Signed-off-by: Neil Horman <[email-masked]>
> Signed-off-by: John Fastabend <[email-masked]>
> CC: Robert Love <[email-masked]>
> CC: "David S. Miller" <[email-masked]>
> ---
>  include/linux/cgroup_subsys.h |    8 +
>  include/linux/netdevice.h     |    4 +
>  include/net/netprio_cgroup.h  |   66 ++++++++
>  include/net/sock.h            |    3 +
>  net/Kconfig                   |    7 +
>  net/core/Makefile             |    1 +
>  net/core/dev.c                |   13 ++
>  net/core/netprio_cgroup.c     |  340 +++++++++++++++++++++++++++++++++++++++++
>  net/core/sock.c               |   22 +++-
>  net/socket.c                  |    2 +
>  10 files changed, 465 insertions(+), 1 deletions(-)
>  create mode 100644 include/net/netprio_cgroup.h
>  create mode 100644 net/core/netprio_cgroup.c
> 

Hi Neil,

couple more comments.

> diff --git a/include/linux/cgroup_subsys.h b/include/linux/cgroup_subsys.h
> index ac663c1..0bd390c 100644
> --- a/include/linux/cgroup_subsys.h
> +++ b/include/linux/cgroup_subsys.h
> @@ -59,8 +59,16 @@ SUBSYS(net_cls)
>  SUBSYS(blkio)
>  #endif
> 
> +/* */
> +
>  #ifdef CONFIG_CGROUP_PERF
>  SUBSYS(perf)
>  #endif
> 
>  /* */
> +
> +#ifdef CONFIG_NETPRIO_CGROUP
> +SUBSYS(net_prio)
> +#endif
> +
> +/* */
> diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
> index 0db1f5f..86e8c3f 100644
> --- a/include/linux/netdevice.h
> +++ b/include/linux/netdevice.h
> @@ -50,6 +50,7 @@
>  #ifdef CONFIG_DCB
>  #include <net/dcbnl.h>
>  #endif
> +#include <net/netprio_cgroup.h>
> 
>  struct vlan_group;
>  struct netpoll_info;
> @@ -1312,6 +1313,9 @@ struct net_device {
>         /* max exchange id for FCoE LRO by ddp */
>         unsigned int            fcoe_ddp_xid;
>  #endif
> +#if IS_ENABLED(CONFIG_NETPRIO_CGROUP)
> +       struct netprio_map *priomap;
> +#endif

Any reason not to annotate this? 'struct netprio_map __rcu *priomap;' and
then use rcu_dereference_protected() throughout.

>         /* phy device may attach itself for hardware timestamping */
>         struct phy_device *phydev;
> 
> diff --git a/include/net/netprio_cgroup.h b/include/net/netprio_cgroup.h
> new file mode 100644
> index 0000000..6b65936
> --- /dev/null
> +++ b/include/net/netprio_cgroup.h
> @@ -0,0 +1,66 @@
> +/*
> + * netprio_cgroup.h                    Control Group Priority set
> + *
> + *
> + * Authors:    Neil Horman <[email-masked]>
> + *
> + * This program is free software; you can redistribute it and/or modify it
> + * under the terms of the GNU General Public License as published by the Free
> + * Software Foundation; either version 2 of the License, or (at your option)
> + * any later version.
> + *
> + */
> +
> +#ifndef _NETPRIO_CGROUP_H
> +#define _NETPRIO_CGROUP_H
> +#include <linux/module.h>
> +#include <linux/cgroup.h>
> +#include <linux/hardirq.h>
> +#include <linux/rcupdate.h>
> +
> +struct cgroup_netprio_state
> +{
> +       struct cgroup_subsys_state css;
> +       u32 prioidx;
> +};
> +
> +struct netprio_map {
> +       struct rcu_head rcu;
> +       u32 priomap_len;
> +       u32 priomap[];
> +};
> +
> +#ifdef CONFIG_CGROUPS
> +
> +#ifndef CONFIG_NETPRIO_CGROUP
> +extern int net_prio_subsys_id;
> +#endif
> +
> +extern void sock_update_netprioidx(struct sock *sk);
> +extern void skb_update_prio(struct sk_buff *skb);
> +
> +static inline struct cgroup_netprio_state
> +               *task_netprio_state(struct task_struct *p)
> +{
> +#if IS_ENABLED(CONFIG_NETPRIO_CGROUP)
> +       return container_of(task_subsys_state(p, net_prio_subsys_id),
> +                           struct cgroup_netprio_state, css);
> +#else
> +       return NULL;
> +#endif
> +}
> +
> +#else
> +
> +#define sock_update_netprioidx(sk)
> +#define skb_update_prio(skb)
> +
> +static inline struct cgroup_netprio_state
> +               *task_netprio_state(struct task_struct *p)
> +{
> +       return NULL;
> +}
> +
> +#endif
> +
> +#endif  /* _NET_CLS_CGROUP_H */
> diff --git a/include/net/sock.h b/include/net/sock.h
> index 5ac682f..87b24aa 100644
> --- a/include/net/sock.h
> +++ b/include/net/sock.h
> @@ -321,6 +321,9 @@ struct sock {
>         unsigned short          sk_ack_backlog;
>         unsigned short          sk_max_ack_backlog;
>         __u32                   sk_priority;
> +#ifdef CONFIG_CGROUPS
> +       __u32                   sk_cgrp_prioidx;
> +#endif
>         struct pid              *sk_peer_pid;
>         const struct cred       *sk_peer_cred;
>         long                    sk_rcvtimeo;
> diff --git a/net/Kconfig b/net/Kconfig
> index a073148..63d2c5d 100644
> --- a/net/Kconfig
> +++ b/net/Kconfig
> @@ -232,6 +232,13 @@ config XPS
>         depends on SMP && SYSFS && USE_GENERIC_SMP_HELPERS
>         default y
> 
> +config NETPRIO_CGROUP
> +       tristate "Network priority cgroup"
> +       depends on CGROUPS
> +       ---help---
> +         Cgroup subsystem for use in assigning processes to network priorities on
> +         a per-interface basis
> +
>  config HAVE_BPF_JIT
>         bool
> 
> diff --git a/net/core/Makefile b/net/core/Makefile
> index 0d357b1..3606d40 100644
> --- a/net/core/Makefile
> +++ b/net/core/Makefile
> @@ -19,3 +19,4 @@ obj-$(CONFIG_FIB_RULES) += fib_rules.o
>  obj-$(CONFIG_TRACEPOINTS) += net-traces.o
>  obj-$(CONFIG_NET_DROP_MONITOR) += drop_monitor.o
>  obj-$(CONFIG_NETWORK_PHY_TIMESTAMPING) += timestamping.o
> +obj-$(CONFIG_NETPRIO_CGROUP) += netprio_cgroup.o
> diff --git a/net/core/dev.c b/net/core/dev.c
> index b7ba81a..a1dca83 100644
> --- a/net/core/dev.c
> +++ b/net/core/dev.c
> @@ -2456,6 +2456,17 @@ static inline int __dev_xmit_skb(struct sk_buff *skb, struct Qdisc *q,
>         return rc;
>  }
> 
> +#ifdef CONFIG_CGROUPS
> +void skb_update_prio(struct sk_buff *skb)
> +{
> +       struct netprio_map *map = rcu_dereference(skb->dev->priomap);
> +
> +       if ((!skb->priority) && (skb->sk) && map)
> +               skb->priority = map->priomap[skb->sk->sk_cgrp_prioidx];
> +}
> +EXPORT_SYMBOL_GPL(skb_update_prio);
> +#endif
> +
>  static DEFINE_PER_CPU(int, xmit_recursion);
>  #define RECURSION_LIMIT 10
> 
> @@ -2496,6 +2507,8 @@ int dev_queue_xmit(struct sk_buff *skb)
>          */
>         rcu_read_lock_bh();
> 
> +       skb_update_prio(skb);
> +
>         txq = dev_pick_tx(dev, skb);
>         q = rcu_dereference_bh(txq->qdisc);
> 
> diff --git a/net/core/netprio_cgroup.c b/net/core/netprio_cgroup.c
> new file mode 100644
> index 0000000..14e896c
> --- /dev/null
> +++ b/net/core/netprio_cgroup.c
> @@ -0,0 +1,340 @@
> +/*
> + * net/sched/cls_cgroup.c      Control Group Classifier
          ^^^^^^^^^^^^^^^^^^
should be netprio_cgroup.c presumably.

> + *
> + *             This program is free software; you can redistribute it and/or
> + *             modify it under the terms of the GNU General Public License
> + *             as published by the Free Software Foundation; either version
> + *             2 of the License, or (at your option) any later version.
> + *
> + * Authors:    Thomas Graf <[email-masked]>
> + */
> +
> +#include <linux/module.h>
> +#include <linux/slab.h>
> +#include <linux/types.h>
> +#include <linux/string.h>
> +#include <linux/errno.h>
> +#include <linux/skbuff.h>
> +#include <linux/cgroup.h>
> +#include <linux/rcupdate.h>
> +#include <linux/atomic.h>
> +#include <net/rtnetlink.h>
> +#include <net/pkt_cls.h>
> +#include <net/sock.h>
> +#include <net/netprio_cgroup.h>
> +
> +static struct cgroup_subsys_state *cgrp_create(struct cgroup_subsys *ss,
> +                                              struct cgroup *cgrp);
> +static void cgrp_destroy(struct cgroup_subsys *ss, struct cgroup *cgrp);
> +static int cgrp_populate(struct cgroup_subsys *ss, struct cgroup *cgrp);
> +
> +struct cgroup_subsys net_prio_subsys = {
> +       .name           = "net_prio",
> +       .create         = cgrp_create,
> +       .destroy        = cgrp_destroy,
> +       .populate       = cgrp_populate,
> +#ifdef CONFIG_NETPRIO_CGROUP
> +       .subsys_id      = net_prio_subsys_id,
> +#endif
> +       .module         = THIS_MODULE
> +};
> +
> +#define PRIOIDX_SZ 128
> +
> +static unsigned long prioidx_map[PRIOIDX_SZ];
> +static DEFINE_SPINLOCK(prioidx_map_lock);
> +static atomic_t max_prioidx = ATOMIC_INIT(0);
> +
> +static inline struct cgroup_netprio_state *cgrp_netprio_state(struct cgroup *cgrp)
> +{
> +       return container_of(cgroup_subsys_state(cgrp, net_prio_subsys_id),
> +                           struct cgroup_netprio_state, css);
> +}
> +
> +static int get_prioidx(u32 *prio)
> +{
> +       unsigned long flags;
> +       u32 prioidx;
> +
> +       spin_lock_irqsave(&prioidx_map_lock, flags);
> +       prioidx = find_first_zero_bit(prioidx_map, sizeof(unsigned long) * PRIOIDX_SZ);
> +       set_bit(prioidx, prioidx_map);
> +       spin_unlock_irqrestore(&prioidx_map_lock, flags);
> +       if (prioidx == sizeof(unsigned long) * PRIOIDX_SZ)
> +               return -ENOSPC;
> +
> +       atomic_set(&max_prioidx, prioidx);
> +       *prio = prioidx;
> +       return 0;
> +}
> +
> +static void put_prioidx(u32 idx)
> +{
> +       unsigned long flags;
> +       spin_lock_irqsave(&prioidx_map_lock, flags);
> +       clear_bit(idx, prioidx_map);
> +       spin_unlock_irqrestore(&prioidx_map_lock, flags);
> +}
> +
> +static void extend_netdev_table(struct net_device *dev, u32 new_len)
> +{
> +       size_t new_size = sizeof(struct netprio_map) +
> +                          ((sizeof(u32) * new_len));
> +       struct netprio_map *new_priomap = kzalloc(new_size, GFP_KERNEL);
> +       struct netprio_map *old_priomap;
> +       int i;
> +
> +       old_priomap  = rcu_dereference_protected(dev->priomap, 1);

This always has rtnl_lock hence the '1' so use rtnl_dereference().

> +

also extra white line.

> +
> +       if (!new_priomap) {
> +               printk(KERN_WARNING "Unable to alloc new priomap!\n");
> +               return;
> +       }
> +
> +       for (i = 0;
> +            dev->priomap && (i < dev->priomap->priomap_len);
               ^^^^^^^^^^^^         ^^^^^^^^^^^^^ 
probably should use old_priomap here.

> +            i++)
> +               new_priomap->priomap[i] = dev->priomap->priomap[i];
> +
> +       new_priomap->priomap_len = new_len;
> +
> +       rcu_assign_pointer(dev->priomap, new_priomap);
> +       if (old_priomap)
> +               kfree_rcu(old_priomap, rcu);
> +

remove extra line.

> +}
> +
> +static void update_netdev_tables(void)
> +{
> +       struct net_device *dev;
> +       u32 max_len = atomic_read(&max_prioidx);
> +
> +       rtnl_lock();
> +
> +       for_each_netdev(&init_net, dev) {
> +               if ((!dev->priomap) ||
> +                   (dev->priomap->priomap_len < max_len))
> +                       extend_netdev_table(dev, max_len);

With __rcu change add rtnl_dereference()

> +       }
> +
> +       rtnl_unlock();
> +}
> +
> +static struct cgroup_subsys_state *cgrp_create(struct cgroup_subsys *ss,
> +                                                struct cgroup *cgrp)
> +{
> +       struct cgroup_netprio_state *cs;
> +       int ret;
> +
> +       cs = kzalloc(sizeof(*cs), GFP_KERNEL);
> +       if (!cs)
> +               return ERR_PTR(-ENOMEM);
> +
> +       if (cgrp->parent && cgrp_netprio_state(cgrp->parent)->prioidx)
> +               return ERR_PTR(-EINVAL);
> +
> +       ret = get_prioidx(&cs->prioidx);
> +       if (ret != 0) {
> +               printk(KERN_WARNING "No space in priority index array\n");
> +               return ERR_PTR(ret);
> +       }
> +
> +       return &cs->css;
> +}
> +
> +static void cgrp_destroy(struct cgroup_subsys *ss, struct cgroup *cgrp)
> +{
> +       struct cgroup_netprio_state *cs;
> +       struct net_device *dev;
> +
> +       cs = cgrp_netprio_state(cgrp);
> +       rtnl_lock();
> +       for_each_netdev(&init_net, dev) {
> +               if (dev->priomap)

ditto rtnl_dereference()

> +                       dev->priomap->priomap[cs->prioidx] = 0;
> +       }
> +       rtnl_unlock();
> +       put_prioidx(cs->prioidx);
> +out_free:
> +       kfree(cs);
> +}
> +
> +static u64 read_prioidx(struct cgroup *cgrp, struct cftype *cft)
> +{
> +       return (u64)cgrp_netprio_state(cgrp)->prioidx;
> +}
> +
> +static int read_priomap(struct cgroup *cont, struct cftype *cft,
> +                       struct cgroup_map_cb *cb)
> +{
> +       struct net_device *dev;
> +       u32 prioidx = cgrp_netprio_state(cont)->prioidx;
> +       u32 priority;
> +
> +       /*
> +        * Stub until I add the per-interface priority map
> +        */

we have a per interface map now... so drop the comments.

> +       rcu_read_lock();
> +       for_each_netdev_rcu(&init_net, dev) {
> +               priority = dev->priomap ? dev->priomap->priomap[prioidx] : 0;

This really needs a rcu_dereference() AFAICT.

> +               cb->fill(cb, dev->name, priority);
> +       }
> +       rcu_read_unlock();
> +       return 0;
> +}
> +
> +static int write_priomap(struct cgroup *cgrp, struct cftype *cft,
> +                        const char *buffer)
> +{
> +       char *devname = kstrdup(buffer, GFP_KERNEL);
> +       int ret = -EINVAL;
> +       u32 prioidx = cgrp_netprio_state(cgrp)->prioidx;
> +       unsigned long priority;
> +       char *priostr;
> +       struct net_device *dev;
> +
> +       devname = kstrdup(buffer, GFP_KERNEL);
> +       if (!devname)
> +               return -ENOMEM;
> +
> +       /*
> +        * Minimally sized valid priomap string
> +        */
> +       if (strlen(devname) < 3)
> +               goto out_free_devname;
> +
> +       priostr = strstr(devname, " ");
> +       if (!priostr)
> +               goto out_free_devname;
> +
> +       /*
> +        *Separate the devname from the associated priority
> +        *and advance the priostr poitner to the priority value
> +        */
> +       *priostr = '\0';
> +       priostr++;
> +
> +       /*
> +        * If the priostr points to NULL, we're at the end of the passed
> +        * in string, and its not a valid write
> +        */
> +       if (*priostr == '\0')
> +               goto out_free_devname;
> +
> +       ret = kstrtoul(priostr, 10, &priority);
> +       if (ret < 0)
> +               goto out_free_devname;
> +
> +       ret = -ENODEV;
> +
> +       dev = dev_get_by_name(&init_net, devname);
> +       if (!dev)
> +               goto out_free_devname;
> +
> +       update_netdev_tables();
> +       ret = 0;
> +       if (dev->priomap)
> +               dev->priomap->priomap[prioidx] = priority;
> +

Whats protecting this? This needs a dereference and rcu_read_lock() I think.

> +       dev_put(dev);
> +
> +out_free_devname:
> +       kfree(devname);
> +       return ret;
> +}
> +
> +static struct cftype ss_files[] = {
> +       {
> +               .name = "prioidx",
> +               .read_u64 = read_prioidx,
> +       },
> +       {
> +               .name = "ifpriomap",
> +               .read_map = read_priomap,
> +               .write_string = write_priomap,
> +       },
> +};
> +
> +static int cgrp_populate(struct cgroup_subsys *ss, struct cgroup *cgrp)
> +{
> +       return cgroup_add_files(cgrp, ss, ss_files, ARRAY_SIZE(ss_files));
> +}
> +
> +static int netprio_device_event(struct notifier_block *unused,
> +                               unsigned long event, void *ptr)
> +{
> +       struct net_device *dev = ptr;
> +       struct netprio_map *old;
> +       u32 max_len = atomic_read(&max_prioidx);
> +
> +       old = rcu_dereference_protected(dev->priomap, 1);
> +       /*
> +        * Note this is called with rtnl_lock held so we have update side
> +        * protection on our rcu assignments
> +        */
> +
> +       switch (event) {
> +
> +       case NETDEV_REGISTER:
> +               if (max_len)
> +                       extend_netdev_table(dev, max_len);
> +               break;
> +       case NETDEV_UNREGISTER:
> +               rcu_assign_pointer(dev->priomap, NULL);
> +               if (old)
> +                       kfree_rcu(old, rcu);
> +               break;
> +       }
> +       return NOTIFY_DONE;
> +}
> +
> +static struct notifier_block netprio_device_notifier = {
> +       .notifier_call = netprio_device_event
> +};
> +
> +static int __init init_cgroup_netprio(void)
> +{
> +       int ret;
> +
> +       ret = cgroup_load_subsys(&net_prio_subsys);
> +       if (ret)
> +               goto out;
> +#ifndef CONFIG_NETPRIO_CGROUP
> +       smp_wmb();
> +       net_prio_subsys_id = net_prio_subsys.subsys_id;
> +#endif
> +
> +       register_netdevice_notifier(&netprio_device_notifier);
> +
> +out:
> +       return ret;
> +}
> +
> +static void __exit exit_cgroup_netprio(void)
> +{
> +       struct netprio_map *old;
> +       struct net_device *dev;
> +
> +       unregister_netdevice_notifier(&netprio_device_notifier);
> +
> +       cgroup_unload_subsys(&net_prio_subsys);
> +
> +#ifndef CONFIG_NETPRIO_CGROUP
> +       net_prio_subsys_id = -1;
> +       synchronize_rcu();
> +#endif
> +
> +       rtnl_lock();
> +       for_each_netdev(&init_net, dev) {
> +               old = dev->priomap;

rtnl_dereference() here also if adding __rcu

> +               rcu_assign_pointer(dev->priomap, NULL);
> +               if (old)
> +                       kfree_rcu(old, rcu);
> +       }
> +       rtnl_unlock();
> +}
> +
> +module_init(init_cgroup_netprio);
> +module_exit(exit_cgroup_netprio);
> +MODULE_LICENSE("GPL v2");
> diff --git a/net/core/sock.c b/net/core/sock.c
> index 5a08762..77a4888 100644
> --- a/net/core/sock.c
> +++ b/net/core/sock.c
> @@ -125,6 +125,7 @@
>  #include <net/xfrm.h>
>  #include <linux/ipsec.h>
>  #include <net/cls_cgroup.h>
> +#include <net/netprio_cgroup.h>
> 
>  #include <linux/filter.h>
> 
> @@ -221,10 +222,16 @@ __u32 sysctl_rmem_default __read_mostly = SK_RMEM_MAX;
>  int sysctl_optmem_max __read_mostly = sizeof(unsigned long)*(2*UIO_MAXIOV+512);
>  EXPORT_SYMBOL(sysctl_optmem_max);
> 
> -#if defined(CONFIG_CGROUPS) && !defined(CONFIG_NET_CLS_CGROUP)
> +#if defined(CONFIG_CGROUPS)
> +#if !defined(CONFIG_NET_CLS_CGROUP)
>  int net_cls_subsys_id = -1;
>  EXPORT_SYMBOL_GPL(net_cls_subsys_id);
>  #endif
> +#if !defined(CONFIG_NETPRIO_CGROUP)
> +int net_prio_subsys_id = -1;
> +EXPORT_SYMBOL_GPL(net_prio_subsys_id);
> +#endif
> +#endif
> 
>  static int sock_set_timeout(long *timeo_p, char __user *optval, int optlen)
>  {
> @@ -1111,6 +1118,18 @@ void sock_update_classid(struct sock *sk)
>                 sk->sk_classid = classid;
>  }
>  EXPORT_SYMBOL(sock_update_classid);
> +
> +void sock_update_netprioidx(struct sock *sk)
> +{
> +       struct cgroup_netprio_state *state;
> +       if (in_interrupt())
> +               return;
> +       rcu_read_lock();
> +       state = task_netprio_state(current);
> +       sk->sk_cgrp_prioidx = state ? state->prioidx : 0;
> +       rcu_read_unlock();
> +}
> +EXPORT_SYMBOL_GPL(sock_update_netprioidx);
>  #endif
> 
>  /**
> @@ -1138,6 +1157,7 @@ struct sock *sk_alloc(struct net *net, int family, gfp_t priority,
>                 atomic_set(&sk->sk_wmem_alloc, 1);
> 
>                 sock_update_classid(sk);
> +               sock_update_netprioidx(sk);
>         }
> 
>         return sk;
> diff --git a/net/socket.c b/net/socket.c
> index 2877647..108716f 100644
> --- a/net/socket.c
> +++ b/net/socket.c
> @@ -549,6 +549,8 @@ static inline int __sock_sendmsg_nosec(struct kiocb *iocb, struct socket *sock,
> 
>         sock_update_classid(sock->sk);
> 
> +       sock_update_netprioidx(sock->sk);
> +
>         si->sock = sock;
>         si->scm = NULL;
>         si->msg = msg;
> --
> 1.7.6.4
>