Commit 0083d27b authored by Tejun Heo's avatar Tejun Heo
Browse files

cgroup: Improve cftype add/rm error handling 



Let's track whether a cftype is currently added or not using a new flag
__CFTYPE_ADDED so that duplicate operations can be failed safely and
consistently allow using empty cftypes.

Signed-off-by: default avatarTejun Heo <tj@kernel.org>
parent a8c52eba

include/linux/cgroup-defs.h

+1 −0
Original line number Diff line number Diff line
@@ -131,6 +131,7 @@ enum { 
	/* internal flags, do not use outside cgroup core proper */

	__CFTYPE_ONLY_ON_DFL	= (1 << 16),	/* only on default hierarchy */

	__CFTYPE_NOT_ON_DFL	= (1 << 17),	/* not on default hierarchy */

	__CFTYPE_ADDED		= (1 << 18),

};



/*

kernel/cgroup/cgroup.c

+20 −7
Original line number Diff line number Diff line
@@ -4198,19 +4198,26 @@ static void cgroup_exit_cftypes(struct cftype *cfts) 
		cft->ss = NULL;



		/* revert flags set by cgroup core while adding @cfts */

		cft->flags &= ~(__CFTYPE_ONLY_ON_DFL | __CFTYPE_NOT_ON_DFL);

		cft->flags &= ~(__CFTYPE_ONLY_ON_DFL | __CFTYPE_NOT_ON_DFL |

				__CFTYPE_ADDED);

	}

}



static int cgroup_init_cftypes(struct cgroup_subsys *ss, struct cftype *cfts)

{

	struct cftype *cft;

	int ret = 0;



	for (cft = cfts; cft->name[0] != '\0'; cft++) {

		struct kernfs_ops *kf_ops;



		WARN_ON(cft->ss || cft->kf_ops);



		if (cft->flags & __CFTYPE_ADDED) {

			ret = -EBUSY;

			break;

		}



		if ((cft->flags & CFTYPE_PRESSURE) && !cgroup_psi_enabled())

			continue;
@@ -4226,26 +4233,26 @@ static int cgroup_init_cftypes(struct cgroup_subsys *ss, struct cftype *cfts) 
		if (cft->max_write_len && cft->max_write_len != PAGE_SIZE) {

			kf_ops = kmemdup(kf_ops, sizeof(*kf_ops), GFP_KERNEL);

			if (!kf_ops) {

				cgroup_exit_cftypes(cfts);

				return -ENOMEM;

				ret = -ENOMEM;

				break;

			}

			kf_ops->atomic_write_len = cft->max_write_len;

		}



		cft->kf_ops = kf_ops;

		cft->ss = ss;

		cft->flags |= __CFTYPE_ADDED;

	}



	return 0;

	if (ret)

		cgroup_exit_cftypes(cfts);

	return ret;

}



static int cgroup_rm_cftypes_locked(struct cftype *cfts)

{

	lockdep_assert_held(&cgroup_mutex);



	if (!cfts || !cfts[0].ss)

		return -ENOENT;



	list_del(&cfts->node);

	cgroup_apply_cftypes(cfts, false);

	cgroup_exit_cftypes(cfts);
@@ -4267,6 +4274,12 @@ int cgroup_rm_cftypes(struct cftype *cfts) 
{

	int ret;



	if (!cfts || cfts[0].name[0] == '\0')

		return 0;



	if (!(cfts[0].flags & __CFTYPE_ADDED))

		return -ENOENT;



	mutex_lock(&cgroup_mutex);

	ret = cgroup_rm_cftypes_locked(cfts);

	mutex_unlock(&cgroup_mutex);