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    Subject[PATCH 6/8] netprio_cgroup: implement netprio[_set]_prio() helpers
    Date
    Introduce two helpers - netprio_prio() and netprio_set_prio() - which
    hide the details of priomap access and expansion. This will help
    implementing hierarchy support.

    Signed-off-by: Tejun Heo <tj@kernel.org>
    ---
    net/core/netprio_cgroup.c | 72 ++++++++++++++++++++++++++++++++---------------
    1 file changed, 50 insertions(+), 22 deletions(-)

    diff --git a/net/core/netprio_cgroup.c b/net/core/netprio_cgroup.c
    index 9409cdf..b2af0d0 100644
    --- a/net/core/netprio_cgroup.c
    +++ b/net/core/netprio_cgroup.c
    @@ -87,6 +87,51 @@ static int extend_netdev_table(struct net_device *dev, u32 target_idx)
    return 0;
    }

    +/**
    + * netprio_prio - return the effective netprio of a cgroup-net_device pair
    + * @cgrp: cgroup part of the target pair
    + * @dev: net_device part of the target pair
    + *
    + * Should be called under RCU read or rtnl lock.
    + */
    +static u32 netprio_prio(struct cgroup *cgrp, struct net_device *dev)
    +{
    + struct netprio_map *map = rcu_dereference_rtnl(dev->priomap);
    +
    + if (map && cgrp->id < map->priomap_len)
    + return map->priomap[cgrp->id];
    + return 0;
    +}
    +
    +/**
    + * netprio_set_prio - set netprio on a cgroup-net_device pair
    + * @cgrp: cgroup part of the target pair
    + * @dev: net_device part of the target pair
    + * @prio: prio to set
    + *
    + * Set netprio to @prio on @cgrp-@dev pair. Should be called under rtnl
    + * lock and may fail under memory pressure for non-zero @prio.
    + */
    +static int netprio_set_prio(struct cgroup *cgrp, struct net_device *dev,
    + u32 prio)
    +{
    + struct netprio_map *map;
    + int ret;
    +
    + /* avoid extending priomap for zero writes */
    + map = rtnl_dereference(dev->priomap);
    + if (!prio && (!map || map->priomap_len <= cgrp->id))
    + return 0;
    +
    + ret = extend_netdev_table(dev, cgrp->id);
    + if (ret)
    + return ret;
    +
    + map = rtnl_dereference(dev->priomap);
    + map->priomap[cgrp->id] = prio;
    + return 0;
    +}
    +
    static struct cgroup_subsys_state *cgrp_css_alloc(struct cgroup *cgrp)
    {
    struct cgroup_netprio_state *cs;
    @@ -105,14 +150,10 @@ static void cgrp_css_free(struct cgroup *cgrp)
    {
    struct cgroup_netprio_state *cs = cgrp_netprio_state(cgrp);
    struct net_device *dev;
    - struct netprio_map *map;

    rtnl_lock();
    - for_each_netdev(&init_net, dev) {
    - map = rtnl_dereference(dev->priomap);
    - if (map && cgrp->id < map->priomap_len)
    - map->priomap[cgrp->id] = 0;
    - }
    + for_each_netdev(&init_net, dev)
    + WARN_ON_ONCE(netprio_set_prio(cgrp, dev, 0));
    rtnl_unlock();
    kfree(cs);
    }
    @@ -126,16 +167,10 @@ static int read_priomap(struct cgroup *cont, struct cftype *cft,
    struct cgroup_map_cb *cb)
    {
    struct net_device *dev;
    - u32 id = cont->id;
    - u32 priority;
    - struct netprio_map *map;

    rcu_read_lock();
    - for_each_netdev_rcu(&init_net, dev) {
    - map = rcu_dereference(dev->priomap);
    - priority = (map && id < map->priomap_len) ? map->priomap[id] : 0;
    - cb->fill(cb, dev->name, priority);
    - }
    + for_each_netdev_rcu(&init_net, dev)
    + cb->fill(cb, dev->name, netprio_prio(cont, dev));
    rcu_read_unlock();
    return 0;
    }
    @@ -145,7 +180,6 @@ static int write_priomap(struct cgroup *cgrp, struct cftype *cft,
    {
    char devname[IFNAMSIZ + 1];
    struct net_device *dev;
    - struct netprio_map *map;
    u32 prio;
    int ret;

    @@ -158,14 +192,8 @@ static int write_priomap(struct cgroup *cgrp, struct cftype *cft,

    rtnl_lock();

    - ret = extend_netdev_table(dev, cgrp->id);
    - if (ret)
    - goto out_unlock;
    + ret = netprio_set_prio(cgrp, dev, prio);

    - map = rtnl_dereference(dev->priomap);
    - if (map)
    - map->priomap[cgrp->id] = prio;
    -out_unlock:
    rtnl_unlock();
    dev_put(dev);
    return ret;
    --
    1.7.11.7


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