Re: [PATCH v3] mm: migrate: requeue destination folio on deferred split queue

[Usama Arif]

On 13/03/2026 03:52, Andrew Morton wrote:
> On Thu, 12 Mar 2026 17:16:30 -0700 SeongJae Park <sj@xxxxxxxxxx> wrote:
> 
>>> By the time migrate_folio_move() runs, partially mapped folios without a
>>> pin have already been split by migrate_pages_batch().  So only two cases
>>> remain on the deferred list at this point:
>>>   1. Partially mapped folios with a pin (split failed).
>>>   2. Fully mapped but potentially underused folios.
>>> The recorded partially_mapped state is forwarded to deferred_split_folio()
>>> so that the destination folio is correctly re-queued in both cases.
>>>
>>> Reported-by: Johannes Weiner <hannes@xxxxxxxxxxx>
>>> Fixes: dafff3f4c850 ("mm: split underused THPs")
>>
>> Seems the commit is merged in 6.12.  And I assume the user impact on
>> THP-shrinker enabled systems is visible.  If so, should we Cc stable@ ?
> 
> I think the user impact should be visible to backport, but the
> changelog is elusive on details?
> 


The original patches added THPs to deferred_list at fault/collapse, they
got removed but not added back to the list after migration.
This patch adds them to the deferred_list on migration. The user would
not expect the THPs to get removed from deferred_list on migration, so
this fixes user expectations.

I have CC-ed stable@xxxxxxxxxxxxxxx to this email. Should I resend the patch
with CC stable in commit message?