Re: [RFC PATCH 1/2] mm/fake-numa: fix under-allocation detection logic in uniform split

[Sang-Heon Jeon <ekffu200098@gmail.com>]

Hello, Mike

On Tue, Apr 14, 2026 at 9:37 PM Mike Rapoport <rppt@kernel.org> wrote:
>
> Hi,
>
> On Tue, Apr 14, 2026 at 12:44:37AM +0900, Sang-Heon Jeon wrote:
> > When split NUMA node uniformly, split_nodes_size_interleave_uniform()
> > returns the next absolute node ID, not the number of nodes created.
> >
> > The previous under-allocation detection logic compares next absolute node
>
> I'd replace "previous" with "existing"

That's good :) I'll replace it.

> > ID (ret) and request count (n), which only works when nid starts at 0.
> >
> > Fix under-allocation detection logic to compare the number of actually
> > created nodes (ret - nid) against the request count (n).
>
> It would be nice to have an example of memory configuration and
> numa=fake=nU that demonstrates the issue.

Sure, I'll add it.

> > Signed-off-by: Sang-Heon Jeon <ekffu200098@gmail.com>
> > Reported-by: Donghyeon Lee <asd142513@gmail.com>
> > Reported-by: Munhui Chae <mochae@student.42seoul.kr>
> > Fixes: cc9aec03e58f ("x86/numa_emulation: Introduce uniform split capability") # 4.19
> > ---
> >  mm/numa_emulation.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/mm/numa_emulation.c b/mm/numa_emulation.c
> > index 703c8fa05048..e7f856c8f2a1 100644
> > --- a/mm/numa_emulation.c
> > +++ b/mm/numa_emulation.c
> > @@ -416,7 +416,7 @@ void __init numa_emulation(struct numa_meminfo *numa_meminfo, int numa_dist_cnt)
> >                                       n, &pi.blk[0], nid);
> >                       if (ret < 0)
> >                               break;
> > -                     if (ret < n) {
> > +                     if (ret - nid < n) {
> >                               pr_info("%s: phys: %d only got %d of %ld nodes, failing\n",
> >                                               __func__, i, ret, n);
> >                               ret = -1;
> > --
> > 2.43.0
> >
>
> --
> Sincerely yours,
> Mike.

Thanks for your kind review.

Best Regards,
Sang-Heon Jeon