cpuset: introduce ->css_on/offline()

Add cpuset_css_on/offline() and rearrange css init/exit such that,

* Allocation and clearing to the default values happen in css_alloc().
  Allocation now uses kzalloc().

* Config inheritance and registration happen in css_online().

* css_offline() undoes what css_online() did.

* css_free() frees.

This doesn't introduce any visible behavior changes.  This will help
cleaning up locking.

Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>

1 files changed, 44 insertions, 22 deletions

diff --git a/kernel/cpuset.c b/kernel/cpuset.c
index 5372b6f5e5b3..1d7a611ff771 100644
--- a/kernel/cpuset.c
+++ b/kernel/cpuset.c
@@ -1790,15 +1790,12 @@ static struct cftype files[] = {
 
 static struct cgroup_subsys_state *cpuset_css_alloc(struct cgroup *cont)
 {
-        struct cgroup *parent_cg = cont->parent;
-        struct cgroup *tmp_cg;
-        struct cpuset *parent, *cs;
+        struct cpuset *cs;
 
-        if (!parent_cg)
+        if (!cont->parent)
                 return &top_cpuset.css;
-        parent = cgroup_cs(parent_cg);
 
-        cs = kmalloc(sizeof(*cs), GFP_KERNEL);
+        cs = kzalloc(sizeof(*cs), GFP_KERNEL);
         if (!cs)
                 return ERR_PTR(-ENOMEM);
         if (!alloc_cpumask_var(&cs->cpus_allowed, GFP_KERNEL)) {
@@ -1806,22 +1803,34 @@ static struct cgroup_subsys_state *cpuset_css_alloc(struct cgroup *cont)
                 return ERR_PTR(-ENOMEM);
         }
 
-        cs->flags = 0;
-        if (is_spread_page(parent))
-                set_bit(CS_SPREAD_PAGE, &cs->flags);
-        if (is_spread_slab(parent))
-                set_bit(CS_SPREAD_SLAB, &cs->flags);
         set_bit(CS_SCHED_LOAD_BALANCE, &cs->flags);
         cpumask_clear(cs->cpus_allowed);
         nodes_clear(cs->mems_allowed);
         fmeter_init(&cs->fmeter);
         cs->relax_domain_level = -1;
+        cs->parent = cgroup_cs(cont->parent);
+
+        return &cs->css;
+}
+
+static int cpuset_css_online(struct cgroup *cgrp)
+{
+        struct cpuset *cs = cgroup_cs(cgrp);
+        struct cpuset *parent = cs->parent;
+        struct cgroup *tmp_cg;
+
+        if (!parent)
+                return 0;
+
+        if (is_spread_page(parent))
+                set_bit(CS_SPREAD_PAGE, &cs->flags);
+        if (is_spread_slab(parent))
+                set_bit(CS_SPREAD_SLAB, &cs->flags);
 
-        cs->parent = parent;
         number_of_cpusets++;
 
-        if (!test_bit(CGRP_CPUSET_CLONE_CHILDREN, &cont->flags))
-                goto skip_clone;
+        if (!test_bit(CGRP_CPUSET_CLONE_CHILDREN, &cgrp->flags))
+                return 0;
 
         /*
          * Clone @parent's configuration if CGRP_CPUSET_CLONE_CHILDREN is
@@ -1836,19 +1845,34 @@ static struct cgroup_subsys_state *cpuset_css_alloc(struct cgroup *cont)
          * changed to grant parent->cpus_allowed-sibling_cpus_exclusive
          * (and likewise for mems) to the new cgroup.
          */
-        list_for_each_entry(tmp_cg, &parent_cg->children, sibling) {
+        list_for_each_entry(tmp_cg, &cgrp->parent->children, sibling) {
                 struct cpuset *tmp_cs = cgroup_cs(tmp_cg);
 
                 if (is_mem_exclusive(tmp_cs) || is_cpu_exclusive(tmp_cs))
-                        goto skip_clone;
+                        return 0;
         }
 
         mutex_lock(&callback_mutex);
         cs->mems_allowed = parent->mems_allowed;
         cpumask_copy(cs->cpus_allowed, parent->cpus_allowed);
         mutex_unlock(&callback_mutex);
-skip_clone:
-        return &cs->css;
+
+        return 0;
+}
+
+static void cpuset_css_offline(struct cgroup *cgrp)
+{
+        struct cpuset *cs = cgroup_cs(cgrp);
+
+        /* css_offline is called w/o cgroup_mutex, grab it */
+        cgroup_lock();
+
+        if (is_sched_load_balance(cs))
+                update_flag(CS_SCHED_LOAD_BALANCE, cs, 0);
+
+        number_of_cpusets--;
+
+        cgroup_unlock();
 }
 
 /*
@@ -1861,10 +1885,6 @@ static void cpuset_css_free(struct cgroup *cont)
 {
         struct cpuset *cs = cgroup_cs(cont);
 
-        if (is_sched_load_balance(cs))
-                update_flag(CS_SCHED_LOAD_BALANCE, cs, 0);
-
-        number_of_cpusets--;
         free_cpumask_var(cs->cpus_allowed);
         kfree(cs);
 }
@@ -1872,6 +1892,8 @@ static void cpuset_css_free(struct cgroup *cont)
 struct cgroup_subsys cpuset_subsys = {
         .name = "cpuset",
         .css_alloc = cpuset_css_alloc,
+        .css_online = cpuset_css_online,
+        .css_offline = cpuset_css_offline,
         .css_free = cpuset_css_free,
         .can_attach = cpuset_can_attach,
         .attach = cpuset_attach,