- /*
- * XXX: We invoke cgroup_add/rm_cftypes() under blkcg_pol_mutex
- * which ends up putting cgroup's internal cgroup_tree_mutex under
- * it; however, cgroup_tree_mutex is nested above cgroup file
- * active protection and grabbing blkcg_pol_mutex from a cgroup
- * file operation creates a possible circular dependency. cgroup
- * internal locking is planned to go through further simplification
- * and this issue should go away soon. For now, let's trylock
- * blkcg_pol_mutex and restart the write on failure.
- *
- * http://lkml.kernel.org/g/5363C04B.4010400@oracle.com
- */
- if (!mutex_trylock(&blkcg_pol_mutex))
- return restart_syscall();