cgroup/cpuset: Fix error handling in remote_partition_disable()

When remote_partition_disable() is called to disable a remote partition,
it always sets the partition to an invalid partition state. It should
only do so if an error code (prs_err) has been set. Correct that and
add proper error code in places where remote_partition_disable() is
called due to error.

Fixes: 181c8e0 ("cgroup/cpuset: Introduce remote partition")
Signed-off-by: Waiman Long <[email protected]>
Signed-off-by: Tejun Heo <[email protected]>

Author: Waiman-Long

kernel/cgroup/cpuset.c

@@ -1406,6 +1406,7 @@ static int remote_partition_enable(struct cpuset *cs, int new_prs,
 	list_add(&cs->remote_sibling, &remote_children);
 	spin_unlock_irq(&callback_lock);
 	update_unbound_workqueue_cpumask(isolcpus_updated);
+	cs->prs_err = 0;
 
 	/*
 	 * Propagate changes in top_cpuset's effective_cpus down the hierarchy.
@@ -1436,9 +1437,11 @@ static void remote_partition_disable(struct cpuset *cs, struct tmpmasks *tmp)
 	list_del_init(&cs->remote_sibling);
 	isolcpus_updated = partition_xcpus_del(cs->partition_root_state,
 					       NULL, tmp->new_cpus);
-	cs->partition_root_state = -cs->partition_root_state;
-	if (!cs->prs_err)
-		cs->prs_err = PERR_INVCPUS;
+	if (cs->prs_err)
+		cs->partition_root_state = -cs->partition_root_state;
+	else
+		cs->partition_root_state = PRS_MEMBER;
+
 	reset_partition_data(cs);
 	spin_unlock_irq(&callback_lock);
 	update_unbound_workqueue_cpumask(isolcpus_updated);
@@ -1471,8 +1474,10 @@ static void remote_cpus_update(struct cpuset *cs, struct cpumask *newmask,
 
 	WARN_ON_ONCE(!cpumask_subset(cs->effective_xcpus, subpartitions_cpus));
 
-	if (cpumask_empty(newmask))
+	if (cpumask_empty(newmask)) {
+		cs->prs_err = PERR_CPUSEMPTY;
 		goto invalidate;
+	}
 
 	adding   = cpumask_andnot(tmp->addmask, newmask, cs->effective_xcpus);
 	deleting = cpumask_andnot(tmp->delmask, cs->effective_xcpus, newmask);
@@ -1482,10 +1487,15 @@ static void remote_cpus_update(struct cpuset *cs, struct cpumask *newmask,
 	 * not allocated to other partitions and there are effective_cpus
 	 * left in the top cpuset.
 	 */
-	if (adding && (!capable(CAP_SYS_ADMIN) ||
-		       cpumask_intersects(tmp->addmask, subpartitions_cpus) ||
-		       cpumask_subset(top_cpuset.effective_cpus, tmp->addmask)))
-		goto invalidate;
+	if (adding) {
+		if (!capable(CAP_SYS_ADMIN))
+			cs->prs_err = PERR_ACCESS;
+		else if (cpumask_intersects(tmp->addmask, subpartitions_cpus) ||
+			 cpumask_subset(top_cpuset.effective_cpus, tmp->addmask))
+			cs->prs_err = PERR_NOCPUS;
+		if (cs->prs_err)
+			goto invalidate;
+	}
 
 	spin_lock_irq(&callback_lock);
 	if (adding)
@@ -1601,7 +1611,7 @@ static bool prstate_housekeeping_conflict(int prstate, struct cpumask *new_cpus)
  * The partcmd_update command is used by update_cpumasks_hier() with newmask
  * NULL and update_cpumask() with newmask set. The partcmd_invalidate is used
  * by update_cpumask() with NULL newmask. In both cases, the callers won't
- * check for error and so partition_root_state and prs_error will be updated
+ * check for error and so partition_root_state and prs_err will be updated
  * directly.
  */
 static int update_parent_effective_cpumask(struct cpuset *cs, int cmd,
@@ -3739,6 +3749,7 @@ static void cpuset_hotplug_update_tasks(struct cpuset *cs, struct tmpmasks *tmp)
 
 	if (remote && cpumask_empty(&new_cpus) &&
 	    partition_is_populated(cs, NULL)) {
+		cs->prs_err = PERR_HOTPLUG;
 		remote_partition_disable(cs, tmp);
 		compute_effective_cpumask(&new_cpus, cs, parent);
 		remote = false;