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cgroup: use ->subtree_control when testing no internal process rule

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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>
This commit is contained in:
Tejun Heo 2016-02-23 10:00:51 -05:00
parent f17fc25f2b
commit 62716ea0f2
1 changed files with 2 additions and 2 deletions
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4
kernel/cgroup.c
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@ -2527,11 +2527,11 @@ static int cgroup_migrate_prepare_dst(struct cgroup *dst_cgrp,
lockdep_assert_held(&cgroup_mutex); 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. * with tasks so that child cgroups don't compete against tasks.
*/ */
if (dst_cgrp && cgroup_on_dfl(dst_cgrp) && cgroup_parent(dst_cgrp) && if (dst_cgrp && cgroup_on_dfl(dst_cgrp) && cgroup_parent(dst_cgrp) &&
dst_cgrp->subtree_ss_mask) dst_cgrp->subtree_control)
return -EBUSY; return -EBUSY;
/* look up the dst cset for each src cset and link it to src */ /* look up the dst cset for each src cset and link it to src */