cgroup: reserve ID 0 for dummy_root and 1 for unified hierarchy
Before 1a57423166 ("cgroup: make hierarchy_id use cyclic idr"),
hierarchy IDs were allocated from 0. As the dummy hierarchy was
always the one first initialized, it got assigned 0 and all other
hierarchies from 1. The patch accidentally changed the minimum
useable ID to 2.
Let's restore ID 0 for dummy_root and while at it reserve 1 for
unified hierarchy.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Cc: stable@vger.kernel.org
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index cef6881..f9c99ab 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -1425,14 +1425,15 @@
init_cgroup_housekeeping(cgrp);
}
-static int cgroup_init_root_id(struct cgroupfs_root *root)
+static int cgroup_init_root_id(struct cgroupfs_root *root, int start, int end)
{
int id;
lockdep_assert_held(&cgroup_mutex);
lockdep_assert_held(&cgroup_root_mutex);
- id = idr_alloc_cyclic(&cgroup_hierarchy_idr, root, 2, 0, GFP_KERNEL);
+ id = idr_alloc_cyclic(&cgroup_hierarchy_idr, root, start, end,
+ GFP_KERNEL);
if (id < 0)
return id;
@@ -1635,7 +1636,8 @@
if (ret)
goto unlock_drop;
- ret = cgroup_init_root_id(root);
+ /* ID 0 is reserved for dummy root, 1 for unified hierarchy */
+ ret = cgroup_init_root_id(root, 2, 0);
if (ret)
goto unlock_drop;
@@ -4898,7 +4900,7 @@
key = css_set_hash(init_css_set.subsys);
hash_add(css_set_table, &init_css_set.hlist, key);
- BUG_ON(cgroup_init_root_id(&cgroup_dummy_root));
+ BUG_ON(cgroup_init_root_id(&cgroup_dummy_root, 0, 1));
mutex_unlock(&cgroup_root_mutex);
mutex_unlock(&cgroup_mutex);