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Commit 1a574231 authored by Tejun Heo's avatar Tejun Heo
Browse files

cgroup: make hierarchy_id use cyclic idr 



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: default avatarTejun Heo <tj@kernel.org>
Acked-by: default avatarLi Zefan <lizefan@huawei.com>
parent 54e7b4eb

kernel/cgroup.c

+8 −20
Original line number Diff line number Diff line
@@ -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;

	}

}