cgroup-cpuset-rebind-mm-mempolicy-to-effective_mems-not-mems_allowed.patch removed from -mm tree

The quilt patch titled
Subject: cgroup/cpuset: rebind mm mempolicy to effective_mems, not mems_allowed
has been removed from the -mm tree. Its filename was
cgroup-cpuset-rebind-mm-mempolicy-to-effective_mems-not-mems_allowed.patch

This patch was dropped because it was merged into mainline or a subsystem tree

------------------------------------------------------
From: Farhad Alemi <[email protected]>
Subject: cgroup/cpuset: rebind mm mempolicy to effective_mems, not mems_allowed
Date: Mon, 6 Jul 2026 10:20:23 +0200

Creating a child cpuset where cpuset.mems is never set leads to a div/0 when a VMA mempolicy with MPOL_F_RELATIVE_NODES rebinds in response to a CPU hotplug event.

Reproduction steps:
1) Create a cgroup w/ cpuset controls (do not set cpuset.mems)
2) Move the task into the child cpuset
3) Create a VMA mempolicy for that task with MPOL_F_RELATIVE_NODES
4) unplug and hotplug a cpu
echo 0 > /sys/devices/system/cpu/cpu1/online
echo 1 > /sys/devices/system/cpu/cpu1/online
5) mempolicy rebind does a div/0 in mpol_relative_nodemask on the call to __nodes_fold()

The cpuset code passes (cs->mems_allowed) which is not guaranteed to have nodes to the rebind routine. Use cs->effective_mems instead, which is guaranteed to have a non-empty nodemask once we reach that code path.

---

 kernel/cgroup/cpuset.c |    7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

@@ -2653,7 +2653,12 @@ void cpuset_update_tasks_nodemask(struct
 
 		migrate = is_memory_migrate(cs);
 
-		mpol_rebind_mm(mm, &cs->mems_allowed);
+		/*
+		 * For v1 we can have empty effective_mems, but we cannot
+		 * attach any tasks (see cpuset_can_attach_check()). For v2,
+		 * effective_mems is guaranteed to not be empty.
+		 */
+		mpol_rebind_mm(mm, &cs->effective_mems);
 		if (migrate)
 			cpuset_migrate_mm(mm, &cs->old_mems_allowed, &newmems);
 		else

_

Patches currently in -mm which might be from [email protected] are