Re: [PATCH 7/7] netprio_cgroup: allow nesting and inherit config on cgroup creation

Daniel Wagner
2012-11-20T08:57:18Z

Hi Tejun,

On 20.11.2012 09:30, Tejun Heo wrote:
> Inherit netprio configuration from ->css_online(), allow nesting and
> remove .broken_hierarchy marking. This makes netprio_cgroup's
> behavior match netcls_cgroup's.
>
> Note that this patch changes userland-visible behavior. Nesting is
> allowed and the first level cgroups below the root cgroup behave
> differently - they inherit priorities from the root cgroup on creation
> instead of starting with 0. This is unfortunate but not doing so is
> much crazier.
>
> Signed-off-by: Tejun Heo <tj@kernel.org>

Tested and Acked-by: Daniel Wagner <daniel.wagner@bmw-carit.de>

> ---
> Documentation/cgroups/net_prio.txt | 2 ++
> net/core/netprio_cgroup.c | 42 ++++++++++++++++++++++----------------
> 2 files changed, 26 insertions(+), 18 deletions(-)
>
> diff --git a/Documentation/cgroups/net_prio.txt b/Documentation/cgroups/net_prio.txt
> index 01b3226..a82cbd2 100644
> --- a/Documentation/cgroups/net_prio.txt
> +++ b/Documentation/cgroups/net_prio.txt
> @@ -51,3 +51,5 @@ One usage for the net_prio cgroup is with mqprio qdisc allowing application
> traffic to be steered to hardware/driver based traffic classes. These mappings
> can then be managed by administrators or other networking protocols such as
> DCBX.
> +
> +A new net_prio cgroup inherits the parent's configuration.
> diff --git a/net/core/netprio_cgroup.c b/net/core/netprio_cgroup.c
> index b2af0d0..bde53da 100644
> --- a/net/core/netprio_cgroup.c
> +++ b/net/core/netprio_cgroup.c
> @@ -136,9 +136,6 @@ static struct cgroup_subsys_state *cgrp_css_alloc(struct cgroup *cgrp)
> {
> struct cgroup_netprio_state *cs;
>
> - if (cgrp->parent && cgrp->parent->id)
> - return ERR_PTR(-EINVAL);
> -
> cs = kzalloc(sizeof(*cs), GFP_KERNEL);
> if (!cs)
> return ERR_PTR(-ENOMEM);
> @@ -146,16 +143,34 @@ static struct cgroup_subsys_state *cgrp_css_alloc(struct cgroup *cgrp)
> return &cs->css;
> }
>
> -static void cgrp_css_free(struct cgroup *cgrp)
> +static int cgrp_css_online(struct cgroup *cgrp)
> {
> - struct cgroup_netprio_state *cs = cgrp_netprio_state(cgrp);
> + struct cgroup *parent = cgrp->parent;
> struct net_device *dev;
> + int ret = 0;
> +
> + if (!parent)
> + return 0;

BTW, parent is always != NULL, because the root cgroup will be attached
to the dummytop cgroup.

This is the reason why there are this check in netprio_prio()

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];

is necessary.

cheer,
daniel