cpuset: fix failure to enable isolated partition when containing isolcpus

The 'isolcpus' parameter specified at boot time can be assigned to an
isolated partition. While it is valid put the 'isolcpus' in an isolated
partition, attempting to change a member cpuset to an isolated partition
will fail if the cpuset contains any 'isolcpus'.

For example, the system boots with 'isolcpus=9', and the following
configuration works correctly:

  # cd /sys/fs/cgroup/
  # mkdir test
  # echo 1 > test/cpuset.cpus
  # echo isolated > test/cpuset.cpus.partition
  # cat test/cpuset.cpus.partition
  isolated
  # echo 9 > test/cpuset.cpus
  # cat test/cpuset.cpus.partition
  isolated
  # cat test/cpuset.cpus
  9

However, the following steps to convert a member cpuset to an isolated
partition will fail:

  # cd /sys/fs/cgroup/
  # mkdir test
  # echo 9 > test/cpuset.cpus
  # echo isolated > test/cpuset.cpus.partition
  # cat test/cpuset.cpus.partition
  isolated invalid (partition config conflicts with housekeeping setup)

The issue occurs because the new partition state (new_prs) is used for
validation against housekeeping constraints before it has been properly
updated. To resolve this, move the assignment of new_prs before the
housekeeping validation check when enabling a root partition.

Fixes: 4a74e418881f ("cgroup/cpuset: Check partition conflict with housekeeping setup")
Signed-off-by: Chen Ridong <chenridong@huawei.com>
Reviewed-by: Waiman Long <longman@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>

diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
index 44231cb1d83fe8cc7b168e93f43f0096700bffae..2b7e2f17577eada0882bed636597206de84a15b2 100644 (file)
--- a/kernel/cgroup/cpuset.c
+++ b/kernel/cgroup/cpuset.c
@@ -1806,6 +1806,7 @@ static int update_parent_effective_cpumask(struct cpuset *cs, int cmd,
                xcpus = tmp->delmask;
                if (compute_excpus(cs, xcpus))
                        WARN_ON_ONCE(!cpumask_empty(cs->exclusive_cpus));
+               new_prs = (cmd == partcmd_enable) ? PRS_ROOT : PRS_ISOLATED;
 
                /*
                 * Enabling partition root is not allowed if its
@@ -1838,7 +1839,6 @@ static int update_parent_effective_cpumask(struct cpuset *cs, int cmd,
 
                deleting = true;
                subparts_delta++;
-               new_prs = (cmd == partcmd_enable) ? PRS_ROOT : PRS_ISOLATED;
        } else if (cmd == partcmd_disable) {
                /*
                 * May need to add cpus back to parent's effective_cpus