Re: [PATCH v4 3/3] mm: hugetlb: fix GFP mask propagation to CMA

[Kefeng Wang <wangkefeng.wang@huawei.com>]

On 11/13/2026 2:56 PM, Qi Zheng wrote:
> 
> 
> On 11/13/26 11:56 AM, Kefeng Wang wrote:
>>
>>
>> On 11/13/2026 10:30 AM, Qi Zheng wrote:
>>>
>>>
>>> On 11/12/26 7:27 PM, Kefeng Wang wrote:
>>>>
>>>>
>>>> On 11/11/2026 2:46 PM, Qi Zheng wrote:
>>>>> From: Qi Zheng <zhengqi.arch@bytedance.com>
>>>>>
>>>>> cma_alloc_frozen_compound() uses GFP_KERNEL, allowing direct reclaim
>>>>> during the first MPOL_PREFERRED_MANY allocation attempt even though
>>>>> the caller clears __GFP_DIRECT_RECLAIM.
>>>>
>>>> MPOL_PREFERRED_MANY is only used for the partner allocator. Without 
>>>> your
>>>
>>> It's doesn't seem so.
>>>
>>> Gigantic surplus allocations already use MPOL_PREFERRED_MANY, following
>>> eb02f14c4a2b ("mm/hugetlb: allow overcommitting gigantic hugepages"),
>>> which predates 9bda131c6093.
>>>
>>> alloc_buddy_hugetlb_folio
>>> --> MPOL_PREFERRED_MANY
>>>      --> gfp_t gfp = gfp_mask & ~(__GFP_DIRECT_RECLAIM | __GFP_NOFAIL);
>>>          folio = alloc_surplus_hugetlb_folio(h, gfp, mpoli->nid, 
>>> nodemask);
>>>          --> alloc_fresh_hugetlb_folio
>>>              --> only_alloc_fresh_hugetlb_folio
>>>                  --> alloc_gigantic_frozen_folio
>>>                      --> hugetlb_cma_alloc_frozen_folio
>>>                          --> cma_alloc_frozen_compound
>>>
>>> Before 9bda131c6093, cma_alloc_folio() forwarded the caller's GFP mask.
>>> The conversion to cma_alloc_frozen_compound() replaced it with
>>> GFP_KERNEL, re-enabling direct reclaim during the preferred-node
>>> attempt.
>>
>> Oh, I forgot about that commit. The naming and some of the comments 
>> are misleading because alloc_buddy_hugetlb_folio/ 
>> alloc_surplus_hugetlb_folio
>> can allocate both buddy and gigantic folios (which can be allocated from
>> CMA).
>>
>> Maybe rename alloc_buddy_hugetlb_folio to hugetlb_alloc_surplus_folio,
>> or other names...
> 
> Naming is difficult. ;)
> 
> The Hugetlb implementation seems quite messy in many places; let’s focus
> on fixing the issues first.
> 

Indeed. thanks for you confirm.