cgroup: collapse cgroup_create() into croup_mkdir()

cgroup_mkdir() is the sole user of cgroup_create().  Let's collapse
the latter into the former.  This will help simplifying locking.
While at it, remove now stale comment about inode locking.

This patch doesn't introduce any functional changes.

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

diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 1d6106c..580d348 100644 (file)
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -4235,30 +4235,24 @@ err_free_css:
        return err;
 }
 
-/**
- * cgroup_create - create a cgroup
- * @parent: cgroup that will be parent of the new cgroup
- * @name: name of the new cgroup
- * @mode: mode to set on new cgroup
- */
-static long cgroup_create(struct cgroup *parent, const char *name,
-                         umode_t mode)
+static int cgroup_mkdir(struct kernfs_node *parent_kn, const char *name,
+                       umode_t mode)
 {
-       struct cgroup *cgrp;
+       struct cgroup *parent = parent_kn->priv, *cgrp;
        struct cgroup_root *root = parent->root;
-       int ssid, ret;
        struct cgroup_subsys *ss;
        struct kernfs_node *kn;
-
-       mutex_lock(&cgroup_tree_mutex);
+       int ssid, ret;
 
        /*
-        * Only live parents can have children.  Note that the liveliness
-        * check isn't strictly necessary because cgroup_mkdir() and
-        * cgroup_rmdir() are fully synchronized by i_mutex; however, do it
-        * anyway so that locking is contained inside cgroup proper and we
-        * don't get nasty surprises if we ever grow another caller.
+        * cgroup_mkdir() grabs cgroup_tree_mutex which nests outside
+        * kernfs active_ref and cgroup_create() already synchronizes
+        * properly against removal through cgroup_lock_live_group().
+        * Break it before calling cgroup_create().
         */
+       cgroup_get(parent);
+       kernfs_break_active_protection(parent_kn);
+       mutex_lock(&cgroup_tree_mutex);
        if (!cgroup_lock_live_group(parent)) {
                ret = -ENODEV;
                goto out_unlock_tree;
@@ -4357,6 +4351,8 @@ out_unlock:
        mutex_unlock(&cgroup_mutex);
 out_unlock_tree:
        mutex_unlock(&cgroup_tree_mutex);
+       kernfs_unbreak_active_protection(parent_kn);
+       cgroup_put(parent);
        return ret;
 
 out_destroy:
@@ -4364,28 +4360,6 @@ out_destroy:
        goto out_unlock;
 }
 
-static int cgroup_mkdir(struct kernfs_node *parent_kn, const char *name,
-                       umode_t mode)
-{
-       struct cgroup *parent = parent_kn->priv;
-       int ret;
-
-       /*
-        * cgroup_create() grabs cgroup_tree_mutex which nests outside
-        * kernfs active_ref and cgroup_create() already synchronizes
-        * properly against removal through cgroup_lock_live_group().
-        * Break it before calling cgroup_create().
-        */
-       cgroup_get(parent);
-       kernfs_break_active_protection(parent_kn);
-
-       ret = cgroup_create(parent, name, mode);
-
-       kernfs_unbreak_active_protection(parent_kn);
-       cgroup_put(parent);
-       return ret;
-}
-
 /*
  * This is called when the refcnt of a css is confirmed to be killed.
  * css_tryget_online() is now guaranteed to fail.