cgroup: remove cftype_set

cftype_set was added primarily to allow registering the same cftype
array more than once for different subsystems.  Nobody uses or needs
such thing and it's already broken because each cftype has ->ss
pointer which is initialized during registration.

Let's add list_head ->node to cftype and use the first cftype entry in
the array to link them instead of allocating separate cftype_set.
While at it, trigger WARN if cft seems previously initialized during
registration.

This simplifies cftype handling a bit.

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

1 files changed, 13 insertions, 28 deletions

diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index a2cbd1549995..506ebd61d1c2 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -1016,12 +1016,12 @@ static void cgroup_clear_dir(struct cgroup *cgrp, unsigned long subsys_mask)
 	int i;
 
 	for_each_subsys(ss, i) {
-		struct cftype_set *set;
+		struct cftype *cfts;
 
 		if (!test_bit(i, &subsys_mask))
 			continue;
-		list_for_each_entry(set, &ss->cftsets, node)
-			cgroup_addrm_files(cgrp, set->cfts, false);
+		list_for_each_entry(cfts, &ss->cfts, node)
+			cgroup_addrm_files(cgrp, cfts, false);
 	}
 }
 
@@ -2392,6 +2392,8 @@ static int cgroup_init_cftypes(struct cgroup_subsys *ss, struct cftype *cfts)
 	for (cft = cfts; cft->name[0] != '\0'; cft++) {
 		struct kernfs_ops *kf_ops;
 
+		WARN_ON(cft->ss || cft->kf_ops);
+
 		if (cft->seq_start)
 			kf_ops = &cgroup_kf_ops;
 		else
@@ -2430,26 +2432,15 @@ static int cgroup_init_cftypes(struct cgroup_subsys *ss, struct cftype *cfts)
  */
 int cgroup_rm_cftypes(struct cftype *cfts)
 {
-	struct cftype *found = NULL;
-	struct cftype_set *set;
-
 	if (!cfts || !cfts[0].ss)
 		return -ENOENT;
 
 	cgroup_cfts_prepare();
+	list_del(&cfts->node);
+	cgroup_cfts_commit(cfts, false);
 
-	list_for_each_entry(set, &cfts[0].ss->cftsets, node) {
-		if (set->cfts == cfts) {
-			list_del(&set->node);
-			kfree(set);
-			found = cfts;
-			break;
-		}
-	}
-
-	cgroup_cfts_commit(found, false);
 	cgroup_exit_cftypes(cfts);
-	return found ? 0 : -ENOENT;
+	return 0;
 }
 
 /**
@@ -2468,20 +2459,14 @@ int cgroup_rm_cftypes(struct cftype *cfts)
  */
 int cgroup_add_cftypes(struct cgroup_subsys *ss, struct cftype *cfts)
 {
-	struct cftype_set *set;
 	int ret;
 
-	set = kzalloc(sizeof(*set), GFP_KERNEL);
-	if (!set)
-		return -ENOMEM;
-
 	ret = cgroup_init_cftypes(ss, cfts);
 	if (ret)
 		return ret;
 
 	cgroup_cfts_prepare();
-	set->cfts = cfts;
-	list_add_tail(&set->node, &ss->cftsets);
+	list_add_tail(&cfts->node, &ss->cfts);
 	ret = cgroup_cfts_commit(cfts, true);
 	if (ret)
 		cgroup_rm_cftypes(cfts);
@@ -3574,13 +3559,13 @@ static int cgroup_populate_dir(struct cgroup *cgrp, unsigned long subsys_mask)
 
 	/* process cftsets of each subsystem */
 	for_each_subsys(ss, i) {
-		struct cftype_set *set;
+		struct cftype *cfts;
 
 		if (!test_bit(i, &subsys_mask))
 			continue;
 
-		list_for_each_entry(set, &ss->cftsets, node) {
-			ret = cgroup_addrm_files(cgrp, set->cfts, true);
+		list_for_each_entry(cfts, &ss->cfts, node) {
+			ret = cgroup_addrm_files(cgrp, cfts, true);
 			if (ret < 0)
 				goto err;
 		}
@@ -4169,7 +4154,7 @@ static void __init cgroup_init_subsys(struct cgroup_subsys *ss)
 	mutex_lock(&cgroup_tree_mutex);
 	mutex_lock(&cgroup_mutex);
 
-	INIT_LIST_HEAD(&ss->cftsets);
+	INIT_LIST_HEAD(&ss->cfts);
 
 	/* Create the top cgroup state for this subsystem */
 	ss->root = &cgroup_dummy_root;