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cgroup: make hierarchy_id use cyclic idr

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We want to be able to lookup a hierarchy from its id and cyclic
allocation is a whole lot simpler with idr.  Convert to idr and use
idr_alloc_cyclc().

Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
This commit is contained in:
Tejun Heo 2013-04-14 11:36:58 -07:00
parent 54e7b4eb15
commit 1a57423166
1 changed files with 8 additions and 20 deletions
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28
kernel/cgroup.c
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@ -194,8 +194,7 @@ static int root_count;
* rules as other root ops - both cgroup_mutex and cgroup_root_mutex for
* writes, either for reads.
*/
static DEFINE_IDA(hierarchy_ida);
static int next_hierarchy_id;
static DEFINE_IDR(cgroup_hierarchy_idr);
/* dummytop is a shorthand for the dummy hierarchy's top cgroup */
#define dummytop (&rootnode.top_cgroup)
@ -1432,27 +1431,16 @@ static void init_cgroup_root(struct cgroupfs_root *root)
static int cgroup_init_root_id(struct cgroupfs_root *root)
{
int ret;
int id;
lockdep_assert_held(&cgroup_mutex);
lockdep_assert_held(&cgroup_root_mutex);
do {
if (!ida_pre_get(&hierarchy_ida, GFP_KERNEL))
return -ENOMEM;
/* Try to allocate the next unused ID */
ret = ida_get_new_above(&hierarchy_ida, next_hierarchy_id,
&root->hierarchy_id);
if (ret == -ENOSPC)
/* Try again starting from 0 */
ret = ida_get_new(&hierarchy_ida, &root->hierarchy_id);
if (!ret) {
next_hierarchy_id = root->hierarchy_id + 1;
} else if (ret != -EAGAIN) {
/* Can only get here if the 31-bit IDR is full ... */
BUG_ON(ret);
}
} while (ret);
id = idr_alloc_cyclic(&cgroup_hierarchy_idr, root, 2, 0, GFP_KERNEL);
if (id < 0)
return id;
root->hierarchy_id = id;
return 0;
}
@ -1462,7 +1450,7 @@ static void cgroup_exit_root_id(struct cgroupfs_root *root)
lockdep_assert_held(&cgroup_root_mutex);
if (root->hierarchy_id) {
ida_remove(&hierarchy_ida, root->hierarchy_id);
idr_remove(&cgroup_hierarchy_idr, root->hierarchy_id);
root->hierarchy_id = 0;
}
}