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

[Huang, Ying]

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.

--
Best Regards,
Huang, Ying