1 files changed, 58 insertions, 5 deletions

diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 87167e40c4fa..fd684bfd154d 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -4426,6 +4426,60 @@ out_err:
         return ret;
 }
 
+static void cgroup_procs_release(struct kernfs_open_file *of)
+{
+        if (of->priv) {
+                css_task_iter_end(of->priv);
+                kfree(of->priv);
+        }
+}
+
+static void *cgroup_procs_next(struct seq_file *s, void *v, loff_t *pos)
+{
+        struct kernfs_open_file *of = s->private;
+        struct css_task_iter *it = of->priv;
+        struct task_struct *task;
+
+        do {
+                task = css_task_iter_next(it);
+        } while (task && !thread_group_leader(task));
+
+        return task;
+}
+
+static void *cgroup_procs_start(struct seq_file *s, loff_t *pos)
+{
+        struct kernfs_open_file *of = s->private;
+        struct cgroup *cgrp = seq_css(s)->cgroup;
+        struct css_task_iter *it = of->priv;
+
+        /*
+         * When a seq_file is seeked, it's always traversed sequentially
+         * from position 0, so we can simply keep iterating on !0 *pos.
+         */
+        if (!it) {
+                if (WARN_ON_ONCE((*pos)++))
+                        return ERR_PTR(-EINVAL);
+
+                it = kzalloc(sizeof(*it), GFP_KERNEL);
+                if (!it)
+                        return ERR_PTR(-ENOMEM);
+                of->priv = it;
+                css_task_iter_start(&cgrp->self, it);
+        } else if (!(*pos)++) {
+                css_task_iter_end(it);
+                css_task_iter_start(&cgrp->self, it);
+        }
+
+        return cgroup_procs_next(s, NULL, NULL);
+}
+
+static int cgroup_procs_show(struct seq_file *s, void *v)
+{
+        seq_printf(s, "%d\n", task_tgid_vnr(v));
+        return 0;
+}
+
 /*
  * Stuff for reading the 'tasks'/'procs' files.
  *
@@ -4914,11 +4968,10 @@ static struct cftype cgroup_dfl_base_files[] = {
         {
                 .name = "cgroup.procs",
                 .file_offset = offsetof(struct cgroup, procs_file),
-                .seq_start = cgroup_pidlist_start,
-                .seq_next = cgroup_pidlist_next,
-                .seq_stop = cgroup_pidlist_stop,
-                .seq_show = cgroup_pidlist_show,
-                .private = CGROUP_FILE_PROCS,
+                .release = cgroup_procs_release,
+                .seq_start = cgroup_procs_start,
+                .seq_next = cgroup_procs_next,
+                .seq_show = cgroup_procs_show,
                 .write = cgroup_procs_write,
         },
         {