Re: [PATCH v2] cgroup/cpuset: Fix update_prstate() always returning 0 on partition errors

[Tao Cui <cui.tao@linux.dev>]

Hi Michal,

You are absolutely right. Looking at this again, this patch is total
suckage.

Returning 0 here is the correct declarative UAPI behavior. The invalid
state records intent and can recover later when resources become
available. Returning -EINVAL would only make things worse since the
state has already been mutated.

Sorry for the noise. I'll drop this patch.

--
Tao

在 2026/6/2 15:46, Michal Koutný 写道:
> Hi.
> 
> On Tue, Jun 02, 2026 at 12:55:21PM +0800, Tao Cui <cui.tao@linux.dev> wrote:
>> update_prstate() stores the error code in cs->prs_err and transitions
>> the partition to an invalid state, but always returns 0. The caller
>> cpuset_partition_write() uses "return retval ?: nbytes", so the write
>> syscall always appears to succeed from userspace even when the partition
>> became invalid.
>> Return -EINVAL when err is set so userspace can detect
>> the failure immediately.
> 
> This is quite a visible UAPI change (a write can succeed to invalidate a
> partition) and users are meant to watch for cpuset.cpus.partition state
> anyway for asynchronous changes.
> 
> I'd not change this gratuitously.
> 
> Michal
>