netprio_cgroup: allow nesting and inherit config on cgroup creation

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>
Acked-by: David S. Miller <davem@davemloft.net>

diff --git a/Documentation/cgroups/net_prio.txt b/Documentation/cgroups/net_prio.txt
index 01b3226..a82cbd2 100644 (file)
--- 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 (file)
--- 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;
 
        rtnl_lock();
-       for_each_netdev(&init_net, dev)
-               WARN_ON_ONCE(netprio_set_prio(cgrp, dev, 0));
+       /*
+        * Inherit prios from the parent.  As all prios are set during
+        * onlining, there is no need to clear them on offline.
+        */
+       for_each_netdev(&init_net, dev) {
+               u32 prio = netprio_prio(parent, dev);
+
+               ret = netprio_set_prio(cgrp, dev, prio);
+               if (ret)
+                       break;
+       }
        rtnl_unlock();
-       kfree(cs);
+       return ret;
+}
+
+static void cgrp_css_free(struct cgroup *cgrp)
+{
+       kfree(cgrp_netprio_state(cgrp));
 }
 
 static u64 read_prioidx(struct cgroup *cgrp, struct cftype *cft)
@@ -237,21 +252,12 @@ static struct cftype ss_files[] = {
 struct cgroup_subsys net_prio_subsys = {
        .name           = "net_prio",
        .css_alloc      = cgrp_css_alloc,
+       .css_online     = cgrp_css_online,
        .css_free       = cgrp_css_free,
        .attach         = net_prio_attach,
        .subsys_id      = net_prio_subsys_id,
        .base_cftypes   = ss_files,
        .module         = THIS_MODULE,
-
-       /*
-        * net_prio has artificial limit on the number of cgroups and
-        * disallows nesting making it impossible to co-mount it with other
-        * hierarchical subsystems.  Remove the artificially low PRIOIDX_SZ
-        * limit and properly nest configuration such that children follow
-        * their parents' configurations by default and are allowed to
-        * override and remove the following.
-        */
-       .broken_hierarchy = true,
 };
 
 static int netprio_device_event(struct notifier_block *unused,