cgroup: Make cgroup_get_from_id() prettier

Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=2077665

commit 7e1eb54
Author: Tejun Heo <tj@kernel.org>
Date:   Fri, 23 Sep 2022 07:23:06 -1000

    cgroup: Make cgroup_get_from_id() prettier

    After merging 836ac87d ("cgroup: fix cgroup_get_from_id") into for-6.1, its
    combination with two commits in for-6.1 - 4534dee ("cgroup: cgroup: Honor
    caller's cgroup NS when resolving cgroup id") and fa7e439 ("cgroup:
    Homogenize cgroup_get_from_id() return value") - makes the gotos in the
    error handling path too ugly while not adding anything of value.

    All that the gotos are saving is one extra kernfs_put() call. Let's remove
    the gotos and perform error returns directly.

    Signed-off-by: Tejun Heo <tj@kernel.org>
    Cc: Ming Lei <ming.lei@redhat.com>
    Cc: Michal Koutný <mkoutny@suse.com>

Signed-off-by: Waiman Long <longman@redhat.com>

Author: Waiman-Long

kernel/cgroup/cgroup.c

@@ -6026,14 +6026,16 @@ void cgroup_path_from_kernfs_id(u64 id, char *buf, size_t buflen)
 struct cgroup *cgroup_get_from_id(u64 id)
 {
 	struct kernfs_node *kn;
-	struct cgroup *cgrp = NULL, *root_cgrp;
+	struct cgroup *cgrp, *root_cgrp;
 
 	kn = kernfs_find_and_get_node_by_id(cgrp_dfl_root.kf_root, id);
 	if (!kn)
-		goto out;
+		return ERR_PTR(-ENOENT);
 
-	if (kernfs_type(kn) != KERNFS_DIR)
-		goto put;
+	if (kernfs_type(kn) != KERNFS_DIR) {
+		kernfs_put(kn);
+		return ERR_PTR(-ENOENT);
+	}
 
 	rcu_read_lock();
 
@@ -6042,21 +6044,20 @@ struct cgroup *cgroup_get_from_id(u64 id)
 		cgrp = NULL;
 
 	rcu_read_unlock();
-put:
 	kernfs_put(kn);
 
 	if (!cgrp)
-		goto out;
+		return ERR_PTR(-ENOENT);
 
 	spin_lock_irq(&css_set_lock);
 	root_cgrp = current_cgns_cgroup_from_root(&cgrp_dfl_root);
 	spin_unlock_irq(&css_set_lock);
 	if (!cgroup_is_descendant(cgrp, root_cgrp)) {
 		cgroup_put(cgrp);
-		cgrp = NULL;
+		return ERR_PTR(-ENOENT);
 	}
-out:
-	return cgrp ?: ERR_PTR(-ENOENT);
+
+	return cgrp;
 }
 EXPORT_SYMBOL_GPL(cgroup_get_from_id);