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Commit fc76df70 authored by Tejun Heo's avatar Tejun Heo
Browse files

cgroup: reserve ID 0 for dummy_root and 1 for unified hierarchy 



Before 1a574231 ("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: default avatarTejun Heo <tj@kernel.org>
Acked-by: default avatarLi Zefan <lizefan@huawei.com>
Cc: stable@vger.kernel.org
parent 30159ec7

kernel/cgroup.c

+6 −4
Original line number Diff line number Diff line
@@ -1425,14 +1425,15 @@ static void init_cgroup_root(struct cgroupfs_root *root) 
	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 @@ static struct dentry *cgroup_mount(struct file_system_type *fs_type, 
		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 @@ int __init cgroup_init(void) 
	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);