cgroup: rename cgroup_subsys_state->dput_work and its callback function

css (cgroup_subsys_state) will become RCU protected and there will be
two stages which require punting to work item during release.  To
prepare for using the work item for multiple times, rename
css->dput_work to css->destroy_work and css_dput_fn() to
css_free_work_fn() and move work item initialization from css init to
right before the actual usage.

This reorganization doesn't introduce any behavior change.

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

2 files changed, 11 insertions, 12 deletions

diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
index 8ec5b0f38292..12d66fee26f8 100644
--- a/include/linux/cgroup.h
+++ b/include/linux/cgroup.h
@@ -80,7 +80,7 @@ struct cgroup_subsys_state {
         struct css_id __rcu *id;
 
         /* Used to put @cgroup->dentry on the last css_put() */
-        struct work_struct dput_work;
+        struct work_struct destroy_work;
 };
 
 /* bits in struct cgroup_subsys_state flags field */
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 49ad96ee08e1..0b280978f097 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -4259,10 +4259,10 @@ err:
         return ret;
 }
 
-static void css_dput_fn(struct work_struct *work)
+static void css_free_work_fn(struct work_struct *work)
 {
         struct cgroup_subsys_state *css =
-                container_of(work, struct cgroup_subsys_state, dput_work);
+                container_of(work, struct cgroup_subsys_state, destroy_work);
 
         cgroup_dput(css->cgroup);
 }
@@ -4272,7 +4272,14 @@ static void css_release(struct percpu_ref *ref)
         struct cgroup_subsys_state *css =
                 container_of(ref, struct cgroup_subsys_state, refcnt);
 
-        schedule_work(&css->dput_work);
+        /*
+         * css holds an extra ref to @cgrp->dentry which is put on the last
+         * css_put().  dput() requires process context, which css_put() may
+         * be called without.  @css->destroy_work will be used to invoke
+         * dput() asynchronously from css_put().
+         */
+        INIT_WORK(&css->destroy_work, css_free_work_fn);
+        schedule_work(&css->destroy_work);
 }
 
 static void init_cgroup_css(struct cgroup_subsys_state *css,
@@ -4287,14 +4294,6 @@ static void init_cgroup_css(struct cgroup_subsys_state *css,
                 css->flags |= CSS_ROOT;
         BUG_ON(cgroup_css(cgrp, ss->subsys_id));
         cgrp->subsys[ss->subsys_id] = css;
-
-        /*
-         * css holds an extra ref to @cgrp->dentry which is put on the last
-         * css_put().  dput() requires process context, which css_put() may
-         * be called without.  @css->dput_work will be used to invoke
-         * dput() asynchronously from css_put().
-         */
-        INIT_WORK(&css->dput_work, css_dput_fn);
 }
 
 /* invoke ->css_online() on a new CSS and mark it online if successful */