[PATCH v2] cgroup/cpuset: Clarify the delegation rules of partition

[Waiman Long]

Creation of remote partition is currently not allowed without privilege.
On the other hand, creation of local partition is allowed without
privilege as long as its parent is also a partition root.

The current setup allows a delegator to delegate an exclusive set of
CPUs to the delegatee by making the root of a delegated sub-hierarchy
a partition root. The delegatee is then allowed to create a local
sub-partition underneath it if necessary. Creation of a remote
partition is not currently allowed across delegation boundary without
privilege. Clarify the partition delegation rules by stating the current
behavior in cgroup-v2.rst file.

Signed-off-by: Waiman Long <longman@xxxxxxxxxx>
---
 Documentation/admin-guide/cgroup-v2.rst | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/Documentation/admin-guide/cgroup-v2.rst b/Documentation/admin-guide/cgroup-v2.rst
index 6efd0095ed99..5b4ebde6fffe 100644
--- a/Documentation/admin-guide/cgroup-v2.rst
+++ b/Documentation/admin-guide/cgroup-v2.rst
@@ -2599,8 +2599,7 @@ Cpuset Interface Files
 
   cpuset.cpus.partition
 	A read-write single value file which exists on non-root
-	cpuset-enabled cgroups.  This flag is owned by the parent cgroup
-	and is not delegatable.
+	cpuset-enabled cgroups.
 
 	It accepts only the following input values when written to.
 
@@ -2708,6 +2707,15 @@ Cpuset Interface Files
 	their parent is switched back to a partition root with a proper
 	value in "cpuset.cpus" or "cpuset.cpus.exclusive".
 
+	This file is owned by the parent cgroup and is not delegatable.
+	The delegator can delegate an exclusive set of CPUs to the
+	delegatee by making the root of a delegated sub-hierarchy a
+	partition root. The delegatee is then allowed to create a local
+	sub-partition underneath it if needed. The delegator should
+	not set "cpuset.cpus.exclusive" at the root without making it
+	a partition root as the creation of remote partition is not
+	allowed without privilege.
+
 	Poll and inotify events are triggered whenever the state of
 	"cpuset.cpus.partition" changes.  That includes changes caused
 	by write to "cpuset.cpus.partition", cpu hotplug or other
-- 
2.53.0