cgroup: factor out cgroup_create() out of cgroup_mkdir()

We're in the process of refactoring cgroup and css management paths to
separate them out to eventually allow cgroups which aren't visible
through cgroup fs.  This patch factors out cgroup_create() out of
cgroup_mkdir().  cgroup_create() contains all internal object creation
and initialization.  cgroup_mkdir() uses cgroup_create() to create the
internal cgroup and adds interface directory and file creation.

This patch doesn't cause any behavior differences.

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

diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index a6d484a..e1b3d0f 100644 (file)
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -4888,33 +4888,19 @@ err_free_css:
        return ERR_PTR(err);
 }
 
-static int cgroup_mkdir(struct kernfs_node *parent_kn, const char *name,
-                       umode_t mode)
+static struct cgroup *cgroup_create(struct cgroup *parent)
 {
-       struct cgroup *parent, *cgrp, *tcgrp;
-       struct cgroup_root *root;
+       struct cgroup_root *root = parent->root;
        struct cgroup_subsys *ss;
-       struct kernfs_node *kn;
-       int level, ssid, ret;
-
-       /* Do not accept '\n' to prevent making /proc/<pid>/cgroup unparsable.
-        */
-       if (strchr(name, '\n'))
-               return -EINVAL;
-
-       parent = cgroup_kn_lock_live(parent_kn);
-       if (!parent)
-               return -ENODEV;
-       root = parent->root;
-       level = parent->level + 1;
+       struct cgroup *cgrp, *tcgrp;
+       int level = parent->level + 1;
+       int ssid, ret;
 
        /* allocate the cgroup and its ID, 0 is reserved for the root */
        cgrp = kzalloc(sizeof(*cgrp) +
                       sizeof(cgrp->ancestor_ids[0]) * (level + 1), GFP_KERNEL);
-       if (!cgrp) {
-               ret = -ENOMEM;
-               goto out_unlock;
-       }
+       if (!cgrp)
+               return ERR_PTR(-ENOMEM);
 
        ret = percpu_ref_init(&cgrp->self.refcnt, css_release, 0, GFP_KERNEL);
        if (ret)
@@ -4978,6 +4964,40 @@ static int cgroup_mkdir(struct kernfs_node *parent_kn, const char *name,
                cgroup_refresh_subtree_ss_mask(cgrp);
        }
 
+       return cgrp;
+
+out_cancel_ref:
+       percpu_ref_exit(&cgrp->self.refcnt);
+out_free_cgrp:
+       kfree(cgrp);
+       return ERR_PTR(ret);
+out_destroy:
+       cgroup_destroy_locked(cgrp);
+       return ERR_PTR(ret);
+}
+
+static int cgroup_mkdir(struct kernfs_node *parent_kn, const char *name,
+                       umode_t mode)
+{
+       struct cgroup *parent, *cgrp;
+       struct cgroup_subsys *ss;
+       struct kernfs_node *kn;
+       int ssid, ret;
+
+       /* do not accept '\n' to prevent making /proc/<pid>/cgroup unparsable */
+       if (strchr(name, '\n'))
+               return -EINVAL;
+
+       parent = cgroup_kn_lock_live(parent_kn);
+       if (!parent)
+               return -ENODEV;
+
+       cgrp = cgroup_create(parent);
+       if (IS_ERR(cgrp)) {
+               ret = PTR_ERR(cgrp);
+               goto out_unlock;
+       }
+
        /* create the directory */
        kn = kernfs_create_dir(parent->kn, name, mode, cgrp);
        if (IS_ERR(kn)) {
@@ -5012,17 +5032,11 @@ static int cgroup_mkdir(struct kernfs_node *parent_kn, const char *name,
        ret = 0;
        goto out_unlock;
 
-out_cancel_ref:
-       percpu_ref_exit(&cgrp->self.refcnt);
-out_free_cgrp:
-       kfree(cgrp);
+out_destroy:
+       cgroup_destroy_locked(cgrp);
 out_unlock:
        cgroup_kn_unlock(parent_kn);
        return ret;
-
-out_destroy:
-       cgroup_destroy_locked(cgrp);
-       goto out_unlock;
 }
 
 /*