On 13.04.22 20:28, Vlastimil Babka wrote:
> On 4/13/22 18:39, David Hildenbrand wrote:
>>>> @@ -3035,10 +3083,19 @@ void set_pmd_migration_entry(struct page_vma_mapped_walk *pvmw,
>>>>
>>>> flush_cache_range(vma, address, address + HPAGE_PMD_SIZE);
>>>> pmdval = pmdp_invalidate(vma, address, pvmw->pmd);
>>>> +
>>>> + anon_exclusive = PageAnon(page) && PageAnonExclusive(page);
>>>> + if (anon_exclusive && page_try_share_anon_rmap(page)) {
>>>> + set_pmd_at(mm, address, pvmw->pmd, pmdval);
>>>> + return;
>>>
>>> I am admittedly not too familiar with this code, but looks like this means
>>> we fail to migrate the THP, right? But we don't seem to be telling the
>>> caller, which is try_to_migrate_one(), so it will continue and not terminate
>>> the walk and return false?
>>
>> Right, we're not returning "false". Returning "false" would be an
>> optimization to make rmap_walk_anon() fail faster.
>
> Ah right, that's what I missed, it's an optimization and we will realize
> elsewhere afterwards that the page has still mappings and we can't migrate...
I'll include that patch in v4 (to be tested):
