[PATCH 7/7] cgroup: Implement cgroup_file_show()

Tejun Heo
2022-08-20T00:06:50Z

Add cgroup_file_show() which allows toggling visibility of a cgroup file
using the new kernfs_deactivate(). This will be used to hide psi interface
files on cgroups where it's disabled.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Chengming Zhou <zhouchengming@bytedance.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
---
include/linux/cgroup.h | 1 +
kernel/cgroup/cgroup.c | 23 +++++++++++++++++++++++
2 files changed, 24 insertions(+)

diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
index ed53bfe7c46c..f61dd135efbe 100644
--- a/include/linux/cgroup.h
+++ b/include/linux/cgroup.h
@@ -114,6 +114,7 @@ int cgroup_add_dfl_cftypes(struct cgroup_subsys *ss, struct cftype *cfts);
int cgroup_add_legacy_cftypes(struct cgroup_subsys *ss, struct cftype *cfts);
int cgroup_rm_cftypes(struct cftype *cfts);
void cgroup_file_notify(struct cgroup_file *cfile);
+void cgroup_file_show(struct cgroup_file *cfile, bool show);

int task_cgroup_path(struct task_struct *task, char *buf, size_t buflen);
int cgroupstats_build(struct cgroupstats *stats, struct dentry *dentry);
diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c
index ffaccd6373f1..eb096499c72b 100644
--- a/kernel/cgroup/cgroup.c
+++ b/kernel/cgroup/cgroup.c
@@ -4339,6 +4339,29 @@ void cgroup_file_notify(struct cgroup_file *cfile)
spin_unlock_irqrestore(&cgroup_file_kn_lock, flags);
}

+/**
+ * cgroup_file_show - show or hide a hidden cgroup file
+ * @cfile: target cgroup_file obtained by setting cftype->file_offset
+ * @show: whether to show or hide
+ */
+void cgroup_file_show(struct cgroup_file *cfile, bool show)
+{
+ struct kernfs_node *kn;
+
+ spin_lock_irq(&cgroup_file_kn_lock);
+ kn = cfile->kn;
+ kernfs_get(kn);
+ spin_unlock_irq(&cgroup_file_kn_lock);
+
+ if (show)
+ kernfs_activate(kn);
+ else
+ kernfs_deactivate(kn);
+
+ kernfs_put(kn);
+}
+
+
/**
* css_next_child - find the next child of a given css
* @pos: the current position (%NULL to initiate traversal)
--
2.37.2