Re: [Patch v3 2/2] mm/huge_memory: merge uniform_split_supported() and non_uniform_split_supported()

[Wei Yang <richard.weiyang@gmail.com>]

On Thu, Nov 06, 2025 at 07:46:14PM -0500, Zi Yan wrote:
>On 5 Nov 2025, at 22:41, Wei Yang wrote:
>
>> The functions uniform_split_supported() and
>> non_uniform_split_supported() share significantly similar logic.
>>
>> The only functional difference is that uniform_split_supported()
>> includes an additional check on the requested @new_order.
>>
>> The reason for this check comes from the following two aspects:
>>
>>   * some file system or swap cache just supports order-0 folio
>>   * the behavioral difference between uniform/non-uniform split
>>
>> The behavioral difference between uniform split and non-uniform:
>>
>>   * uniform split splits folio directly to @new_order
>>   * non-uniform split creates after-split folios with orders from
>>     folio_order(folio) - 1 to new_order.
>>
>> This means for non-uniform split or !new_order split we should check the
>> file system and swap cache respectively.
>>
>> This commit unifies the logic and merge the two functions into a single
>> combined helper, removing redundant code and simplifying the split
>> support checking mechanism.
>>
>> Signed-off-by: Wei Yang <richard.weiyang@gmail.com>
>> Cc: Zi Yan <ziy@nvidia.com>
>> Cc: "David Hildenbrand (Red Hat)" <david@kernel.org>
>>
>> ---
>> v3:
>>   * adjust to use split_type
>>   * rebase on Zi Yan fix lkml.kernel.org/r/20251105162910.752266-1-ziy@nvidia.com
>> v2:
>>   * remove need_check
>>   * update comment
>>   * add more explanation in change log
>> ---
>>  include/linux/huge_mm.h |  8 ++---
>>  mm/huge_memory.c        | 71 +++++++++++++++++------------------------
>>  2 files changed, 33 insertions(+), 46 deletions(-)
>>
>LGTM. Thanks. Reviewed-by: Zi Yan <ziy@nvidia.com>

Hi, Zi

I am thinking whether it is proper to move the check (new_order < min_order)
from __folio_split() to folio_split_supported(). So that we could bail out
early if file system couldn't split to new_order.

Not sure you like it or not.

-- 
Wei Yang
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