Re: [PATCH cgroup/for-next v2 0/5] cgroup/cpuset: Support multiple source/destination cpusets for cpuset_*attach()

[Waiman Long]

On 5/16/26 12:24 AM, Waiman Long wrote:
> Sashiko AI review of another cpuset patch had found that cpuset_attach()
> and cpuset_can_attach() can be passed a cgroup_taskset with tasks
> migrating from one source cpuset to multiple destination cpusets and
> vice versa.  Further testing of the cpuset code indicates that this is
> indeed the case when the v2 cpuset controller is enabled or disabled.
>
> Unfortunately, cpuset_attach() and cpuset_can_attach() still assume that
> there will be one source and one destinaton cpuset which may result in
> inocrrect behavior.
>
> This patch series is created to fix this issue. The first 2 patches are
> just preparatory patches to make the remaining patches easier to review.
>
> Patch 3 adds a new attach_old_cs field into task_struct to track the
> old cpuset to be used in case when cpuset_migrate_mm() needs to be
> called in cpuset_attach().
>
> Patch 4 moves mpol_rebind_mm() and cpuset_migrate_mm() inside
> cpuset_attach_task() to make CLONE_INTO_CGROUP flag of clone(2) works
> more like moving task from one cpuset to another one, while also make
> supporting multiple source and destination cpusets easier.
>
> Patch 5 makes the necessary changes to enable the support of multiple
> source and destination cpusets by keeping all the source and destination
> cpusets found during task iterations in two singly linked lists for
> source and destination cpusets respectively.

Sorry, I forgot to add the change log. It is basically to address all 
the AI review comments [1] for my v1 patch.

The 2 major changes are to move cpuset_migrate_mm() into 
cpuset_attach_task() and add a new field in task_struct to record the 
old cpuset to be used by cpuset_migrate_mm(). There also some other 
minor changes.

[1] 
https://lore.kernel.org/lkml/4f49602d35d987e029b8e92a577f0c60@xxxxxxxxxx/

Cheers,
Longman

> Waiman Long (5):
>    cgroup/cpuset: Add a cpuset_reserve_dl_bw() helper
>    cgroup/cpuset: Expand the scope of cpuset_can_attach_check()
>    cgroup/cpuset: Replace cpuset_attach_old_cs by a new attach_old_cs
>      field in task_struct
>    cgroup/cpuset: Move mpol_rebind_mm/cpuset_migrate_mm() calls inside
>      cpuset_attach_task()
>    cgroup/cpuset: Support multiple source/destination cpusets for
>      cpuset_*attach()
>
>   include/linux/sched.h           |   3 +
>   kernel/cgroup/cpuset-internal.h |   6 +
>   kernel/cgroup/cpuset.c          | 358 +++++++++++++++++++++-----------
>   3 files changed, 249 insertions(+), 118 deletions(-)