Re: [PATCH v3] mm, memcg: fix error return value of mem_cgroup_css_alloc()

[Yafang Shao <laoar.shao@gmail.com>]

On Tue, Apr 7, 2020 at 7:23 AM Andrew Morton <akpm@linux-foundation.org> wrote:
>
> On Tue,  7 Apr 2020 00:56:03 +0800 Yafang Shao <laoar.shao@gmail.com> wrote:
>
> > When I run my memcg testcase which creates lots of memcgs, I found
> > there're unexpected out of memory logs while there're still enough
> > available free memory. The error log is,
> > mkdir: cannot create directory 'foo.65533': Cannot allocate memory
> >
> > The reason is when we try to create more than MEM_CGROUP_ID_MAX memcgs, an
> > -ENOMEM errno will be set by mem_cgroup_css_alloc(), but the right errno
> > should be -EBUSY "Device or resource busy". That is same with
> > memcg_alloc_cache_id().
> >
> > As the errno really misled me, we should make it right. After this patch,
> > the error log will be,
> > mkdir: cannot create directory 'foo.65533': Device or resource busy
>
> Thanks.
>
> Was a -stable backport considered?

I only backported to our kernel version 4.18, but I'm not sure whether
it will apply to -stable or not.
Seems this issue is introduced long time ago. I will try to backport
it to -stable.
Should I try it based on 5.5.y and 5.6.y only ? Or all the LTS kernel
versions ?

Thanks
Yafang