cgroup: use ->subtree_control when testing no internal process rule
No internal process rule is enforced by cgroup_migrate_prepare_dst()
during process migration. It tests whether the target cgroup's
->child_subsys_mask is zero which is different from "subtree_control"
write path which tests ->subtree_control. This hasn't mattered
because up until now, both ->child_subsys_mask and ->subtree_control
are zero or non-zero at the same time. However, with the planned
addition of implicit controllers, this will no longer be true.
This patch prepares for the change by making
cgorup_migrate_prepare_dst() test ->subtree_control instead.
Signed-off-by: Tejun Heo <tj@kernel.org>
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 2b11436..ac5451e 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -2527,11 +2527,11 @@
lockdep_assert_held(&cgroup_mutex);
/*
- * Except for the root, subtree_ss_mask must be zero for a cgroup
+ * Except for the root, subtree_control must be zero for a cgroup
* with tasks so that child cgroups don't compete against tasks.
*/
if (dst_cgrp && cgroup_on_dfl(dst_cgrp) && cgroup_parent(dst_cgrp) &&
- dst_cgrp->subtree_ss_mask)
+ dst_cgrp->subtree_control)
return -EBUSY;
/* look up the dst cset for each src cset and link it to src */