Hi Matthew,
>>>> diff --git a/mm/huge_memory.c b/mm/huge_memory.c
>>>> index 9859aa4f7553..c6d4d0cdf4b3 100644
>>>> --- a/mm/huge_memory.c
>>>> +++ b/mm/huge_memory.c
>>>> @@ -766,28 +766,6 @@ pmd_t maybe_pmd_mkwrite(pmd_t pmd, struct vm_area_struct *vma)
>>>> return pmd;
>>>> }
>>>>
>>>> -#ifdef CONFIG_MEMCG
>>>> -static inline
>>>> -struct deferred_split *get_deferred_split_queue(struct folio *folio)
>>>> -{
>>>> - struct mem_cgroup *memcg = folio_memcg(folio);
>>>> - struct pglist_data *pgdat = NODE_DATA(folio_nid(folio));
>>>> -
>>>> - if (memcg)
>>>> - return &memcg->deferred_split_queue;
>>>> - else
>>>> - return &pgdat->deferred_split_queue;
>>>> -}
>>>> -#else
>>>> -static inline
>>>> -struct deferred_split *get_deferred_split_queue(struct folio *folio)
>>>> -{
>>>> - struct pglist_data *pgdat = NODE_DATA(folio_nid(folio));
>>>> -
>>>> - return &pgdat->deferred_split_queue;
>>>> -}
>>>> -#endif
>>>> -
>>>> void folio_prep_large_rmappable(struct folio *folio)
>>>> {
>>>> if (!folio || !folio_test_large(folio))
>>>> diff --git a/mm/internal.h b/mm/internal.h
>>>> index d1c69119b24f..8fa36e84463a 100644
>>>> --- a/mm/internal.h
>>>> +++ b/mm/internal.h
>>>> @@ -1107,6 +1107,29 @@ struct page *follow_trans_huge_pmd(struct vm_area_struct *vma,
>>>> unsigned long addr, pmd_t *pmd,
>>>> unsigned int flags);
>>>>
>>>> +#ifdef CONFIG_MEMCG
>>>> +static inline
>>>> +struct deferred_split *get_deferred_split_queue(struct folio *folio)
>>>> +{
>>>> + struct mem_cgroup *memcg = folio_memcg(folio);
>>>> + struct pglist_data *pgdat = NODE_DATA(folio_nid(folio));
>>>> +
>>>> + if (memcg)
>>>> + return &memcg->deferred_split_queue;
>>>> + else
>>>> + return &pgdat->deferred_split_queue;
>>>> +}
>>>> +#else
>>>> +static inline
>>>> +struct deferred_split *get_deferred_split_queue(struct folio *folio)
>>>> +{
>>>> + struct pglist_data *pgdat = NODE_DATA(folio_nid(folio));
>>>> +
>>>> + return &pgdat->deferred_split_queue;
>>>> +}
>>>> +#endif
>>>
>>> I found this breaks the build when CONFIG_TRANSPARENT_HUGEPAGE is not set, with
>>> below error:
>>>
>>> .../lib/../mm/internal.h: In function 'get_deferred_split_queue':
>>> .../lib/../mm/internal.h:1127:22: error: 'struct pglist_data' has no member named 'deferred_split_queue'
>>> 1127 | return &pgdat->deferred_split_queue;
>>> | ^~
>>>
>>> Since the code was in hugepage.c, maybe the above chunk need to be wrapped by
>>> #ifdef CONFIG_TRANSPARENT_HUGEPAGE? I confirmed below change is fixing the
>>> build on my setup.
>>
>> Thanks. Will fix it in the next version.
>
> Actually, since get_deferred_split_queue() is used in mm/migrate.c, that
> part needs to be guarded by CONFIG_TRANSPARENT_HUGEPAGE as well.
_deferred_list is not hidden behind CONFIG_TRANSPARENT_HUGEPAGE but
its users are all behind CONFIG_TRANSPARENT_HUGEPAGE. Should it be moved
as well? Or the other way around, moving _deferred_list users out?
Large folios should work without THP, since they would be like THP without
PMD mappings, namely mTHP. But mTHP is considered a subset of THP. It seems
confusing. Maybe hiding _deferred_list behind CONFIG_TRANSPARENT_HUGEPAGE
is better, or just do not change.
--
Best Regards,
Yan, Zi
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