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

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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
This commit is contained in:
Tejun Heo 2013-06-25 11:53:37 -07:00
parent 30159ec7a9
commit fc76df7061
1 changed files with 6 additions and 4 deletions
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10
kernel/cgroup.c
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@ -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);