Re: [REGRESSION] mremap() fails VMA expansion when VM_MIXEDMAP is set

[Luiz Capitulino]

On 10/23/26 4:19 AM, Lorenzo Stoakes (ARM) wrote:
> On Fri, Oct 23, 2026 at 09:16:12AM +0200, Vlastimil Babka (SUSE) wrote:
> > On 10/23/26 04:31, Luiz Capitulino wrote:
>
> > > This regression was introduced in v6.1 by commit ca3d76b0aa80 ("mm: add merging
> > > after mremap resize"). This commit changed mremap() to use vma_merge() instead
> > > of vma_adjust() for the expansion case. However, vma_merge() returns NULL for
> > > a VMA that has any of the VM_SPECIAL flags set.
> >
> > Hi,
> >
> > 6.1 was a rather long time ago. How was it discovered just now? I.e. what
> > use case broke by the change and prompted creating the reproducer?
> >
> > Vlastimil
> > Thanks,
>
> Thanks, I have the same questions :)
>
> Do always include that kind of information and whether it was an LLM-discovered
> thing or whether you had an actual workload that was impacted, etc.

Will do the next time, I claried the use-case in my response to
Vlastimil.

> --
> Cheers, Lorenzo