cpuset: fix a regression in validating config change

It's not allowed to clear masks of a cpuset if there're tasks in it,
but it's broken:

  # mkdir /cgroup/sub
  # echo 0 > /cgroup/sub/cpuset.cpus
  # echo 0 > /cgroup/sub/cpuset.mems
  # echo $$ > /cgroup/sub/tasks
  # echo > /cgroup/sub/cpuset.cpus
  (should fail)

This bug was introduced by commit 88fa523bff295f1d60244a54833480b02f775152
("cpuset: allow to move tasks to empty cpusets").

tj: Dropped temp bool variables and nestes the conditionals directly.

Signed-off-by: Li Zefan <lizefan@huawei.com>
Signed-off-by: Tejun Heo <tj@kernel.org>

diff --git a/kernel/cpuset.c b/kernel/cpuset.c
index 010a008..ea1966d 100644 (file)
--- a/kernel/cpuset.c
+++ b/kernel/cpuset.c
@@ -475,13 +475,17 @@ static int validate_change(const struct cpuset *cur, const struct cpuset *trial)
 
        /*
         * Cpusets with tasks - existing or newly being attached - can't
-        * have empty cpus_allowed or mems_allowed.
+        * be changed to have empty cpus_allowed or mems_allowed.
         */
        ret = -ENOSPC;
-       if ((cgroup_task_count(cur->css.cgroup) || cur->attach_in_progress) &&
-           (cpumask_empty(trial->cpus_allowed) &&
-            nodes_empty(trial->mems_allowed)))
-               goto out;
+       if ((cgroup_task_count(cur->css.cgroup) || cur->attach_in_progress)) {
+               if (!cpumask_empty(cur->cpus_allowed) &&
+                   cpumask_empty(trial->cpus_allowed))
+                       goto out;
+               if (!nodes_empty(cur->mems_allowed) &&
+                   nodes_empty(trial->mems_allowed))
+                       goto out;
+       }
 
        ret = 0;
 out: