[PATCH-next v2 3/6] cgroup/cpuset: Do housekeeping check before converting invalid partition to valid

[Waiman Long <longman@redhat.com>]

When a hotplug event happens or when update_cpumasks_hier() is called, an
invalid partition may be converted back to valid. However check against
housekeeping conflict isn't being done which can lead to a partition
state that violates the housekeeping rules. Update the code to allow
reviving an invalid partition only if it can pass the housekeeping check.

Fixes: 4a74e418881f ("cgroup/cpuset: Check partition conflict with housekeeping setup")
Signed-off-by: Waiman Long <longman@redhat.com>
---
 kernel/cgroup/cpuset.c | 18 ++++++++++++++++--
 1 file changed, 16 insertions(+), 2 deletions(-)

diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
index 1c0441fa3bea..fb41cd76add6 100644
--- a/kernel/cgroup/cpuset.c
+++ b/kernel/cgroup/cpuset.c
@@ -1374,6 +1374,13 @@ static bool prstate_housekeeping_conflict(int new_prs, int parent_prs,
 	cpumask_var_t full_hk_cpus;
 	int res;
 
+	/*
+	 * For a currently invalid partition state, do the check assuming that
+	 * it may be converted back to valid.
+	 */
+	if (new_prs < 0)
+		new_prs = -new_prs;
+
 	if (housekeeping_enabled(HK_TYPE_DOMAIN_BOOT) && (new_prs == PRS_ROOT) &&
 	    !cpumask_subset(add_cpus, housekeeping_cpumask(HK_TYPE_DOMAIN_BOOT)))
 		return true;
@@ -1956,9 +1963,16 @@ static int update_parent_effective_cpumask(struct cpuset *cs, int cmd,
 			bool exclusive = true;
 
 			/*
-			 * Convert invalid partition to valid has to
-			 * pass the cpu exclusivity test.
+			 * Convert invalid partition to valid has to pass the
+			 * cpu exclusivity test as well as the housekeeping
+			 * check.
 			 */
+			if (prstate_housekeeping_conflict(cs->partition_root_state,
+							  parent->partition_root_state,
+							  xcpus, NULL)) {
+				part_error = PERR_HKEEPING;
+				goto write_error;
+			}
 			rcu_read_lock();
 			cpuset_for_each_child(child, css, parent) {
 				if (child == cs)
-- 
2.55.0