Re: [PATCH v3 03/12] mm/huge_memory: move THP gfp limit helper into header

[Zi Yan]

On 21 Apr 2026, at 13:21, Kairui Song wrote:

> On Tue, Apr 21, 2026 at 9:14 PM Zi Yan <ziy@xxxxxxxxxx> wrote:
>>
>> On 21 Apr 2026, at 2:16, Kairui Song via B4 Relay wrote:
>>
>>> From: Kairui Song <kasong@xxxxxxxxxxx>
>>>
>>> Shmem has some special requirements for THP GFP and has to limit it in
>>> certain zones or provide a more lenient fallback.
>>>
>>> We'll use this helper for generic swap THP allocation, which needs to
>>> support shmem. For a typical GFP_HIGHUSER_MOVABLE swap-in, this helper
>>> is basically a no-op. But it's necessary for certain shmem users, mostly
>>> drivers.
>>>
>>> No feature change.
>>>
>>> Signed-off-by: Kairui Song <kasong@xxxxxxxxxxx>
>>> ---
>>>  include/linux/huge_mm.h | 30 ++++++++++++++++++++++++++++++
>>>  mm/shmem.c              | 30 +++---------------------------
>>>  2 files changed, 33 insertions(+), 27 deletions(-)
>>>
>>> diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h
>>> index 2949e5acff35..ffe5a120eee4 100644
>>> --- a/include/linux/huge_mm.h
>>> +++ b/include/linux/huge_mm.h
>>> @@ -237,6 +237,31 @@ static inline bool thp_vma_suitable_order(struct vm_area_struct *vma,
>>>       return true;
>>>  }
>>>
>>> +/*
>>> + * Make sure huge_gfp is always more limited than limit_gfp.
>>> + * Some shmem users want THP allocation to be done less aggressively
>>> + * and only in certain zone.
>>> + */
>>> +static inline gfp_t thp_limit_gfp_mask(gfp_t huge_gfp, gfp_t limit_gfp)
>>
>> Would it be better to rename it to thp_swap_limit_gfp_mask() or something
>> more descriptive? I am just worried about misuses in the future due to
>> the generic thp prefix.
>
> Good idea, I wasn't sure if this might be helpful for any other user,
> but for now naming it more descriptive does help to avoid misuse.
>
> How about thp_shmem_limit_gfp_mask? Ordinary swap is fine with thp
> gfp, only shmem is a bit special.
>

Sounds good to me. Thanks.

>>
>> Otherwise, LGTM.
>>
>> Reviewed-by: Zi Yan <ziy@xxxxxxxxxx>
>
> Thanks!


Best Regards,
Yan, Zi