cgroup add cftype->open/release() callbacks

Pipe the newly added kernfs->open/release() callbacks through cftype.
While at it, as cleanup operations now can be performed from
->release() instead of ->seq_stop(), make the latter optional.

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

2 files changed, 26 insertions, 1 deletions

diff --git a/include/linux/cgroup-defs.h b/include/linux/cgroup-defs.h
index 861b4677fc5b..8a916dc96e84 100644
--- a/include/linux/cgroup-defs.h
+++ b/include/linux/cgroup-defs.h
@@ -388,6 +388,9 @@ struct cftype {
         struct list_head node;          /* anchored at ss->cfts */
         struct kernfs_ops *kf_ops;
 
+        int (*open)(struct kernfs_open_file *of);
+        void (*release)(struct kernfs_open_file *of);
+
         /*
          * read_u64() is a shortcut for the common case of returning a
          * single integer. Use it in place of read()
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 2ee9ec3051b2..87167e40c4fa 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -3503,6 +3503,23 @@ static int cgroup_events_show(struct seq_file *seq, void *v)
         return 0;
 }
 
+static int cgroup_file_open(struct kernfs_open_file *of)
+{
+        struct cftype *cft = of->kn->priv;
+
+        if (cft->open)
+                return cft->open(of);
+        return 0;
+}
+
+static void cgroup_file_release(struct kernfs_open_file *of)
+{
+        struct cftype *cft = of->kn->priv;
+
+        if (cft->release)
+                cft->release(of);
+}
+
 static ssize_t cgroup_file_write(struct kernfs_open_file *of, char *buf,
                                  size_t nbytes, loff_t off)
 {
@@ -3553,7 +3570,8 @@ static void *cgroup_seqfile_next(struct seq_file *seq, void *v, loff_t *ppos)
 
 static void cgroup_seqfile_stop(struct seq_file *seq, void *v)
 {
-        seq_cft(seq)->seq_stop(seq, v);
+        if (seq_cft(seq)->seq_stop)
+                seq_cft(seq)->seq_stop(seq, v);
 }
 
 static int cgroup_seqfile_show(struct seq_file *m, void *arg)
@@ -3575,12 +3593,16 @@ static int cgroup_seqfile_show(struct seq_file *m, void *arg)
 
 static struct kernfs_ops cgroup_kf_single_ops = {
         .atomic_write_len       = PAGE_SIZE,
+        .open                   = cgroup_file_open,
+        .release                = cgroup_file_release,
         .write                  = cgroup_file_write,
         .seq_show               = cgroup_seqfile_show,
 };
 
 static struct kernfs_ops cgroup_kf_ops = {
         .atomic_write_len       = PAGE_SIZE,
+        .open                   = cgroup_file_open,
+        .release                = cgroup_file_release,
         .write                  = cgroup_file_write,
         .seq_start              = cgroup_seqfile_start,
         .seq_next               = cgroup_seqfile_next,