Re: [PATCH v3 3/3] mm/migrate: move common code to numa_migrate_check (was numa_migrate_prep)

[David Hildenbrand]

On 12.08.24 04:20, Huang, Ying wrote:
> David Hildenbrand <david@xxxxxxxxxx> writes:
>
> > On 09.08.24 16:59, Zi Yan wrote:
> > > do_numa_page() and do_huge_pmd_numa_page() share a lot of common code. To
> > > reduce redundancy, move common code to numa_migrate_prep() and rename
> > > the function to numa_migrate_check() to reflect its functionality.
> > > Now do_huge_pmd_numa_page() also checks shared folios to set
> > > TNF_SHARED flag.
> >
> > Yeah, I was also wondering why we didn't check that in the PMD case.
>
> IIUC, before commit 728be28fae8c ("mm: migrate: remove THP mapcount
> check in numamigrate_isolate_page()"), we don't allow to migrate THP
> with mapcount > 1.  So, it's unnecessary to set TNF_SHARED flag at that
> time.  However, after that commit, we need to do it.

Thanks for the pointer, rings a bell. Indeed, the check was remove for a 
different purpose, so introducing a check for setting the flag makes sense.

--
Cheers,

David / dhildenb