Re: [PATCH v8 14/14] mm: thp: always enable mTHP support

[Luiz Capitulino <luizcap@redhat.com>]

On 10/2/26 11:13 PM, Lance Yang wrote:
> 
> On Thu, Sep 17, 2026 at 09:45:35PM -0400, Luiz Capitulino wrote:
>> If PMD-sized pages are not supported on an architecture (ie. the
>> arch implements arch_has_pmd_leaves() and it returns false) then the
>> current code disables all THP, including mTHP.
>>
>> This commit fixes this by allowing mTHP to be always enabled for all
>> archs. When PMD-sized pages are not supported, its sysfs entry won't be
>> created and their mapping will be disallowed at page-fault time.
>>
>> Similarly, this commit implements the following changes for shmem in
>> shmem_allowable_huge_orders():
>>
>> - Drop the pgtable_has_pmd_leaves() check so that mTHP sizes are
>>    considered
>> - Filter out PMD and PUD orders from allowable orders when
>>    PMD-sized pages are not supported by the CPU
> 
> Nit: "and PUD" can go.
> 
> David mentioned
> 
> "
> There is no need to disable PUD-orders, as shmem does not support PUD-orders
> (unlike DAX). So you can keep it simpler here.
> "
> 
> in v4
> 
> https://lore.kernel.org/all/ff7bcd65-d444-4da1-890e-75504303ec3f@kernel.org/

Yes, I changed the code and didn't update the changelog. Fixed now,
thanks Lance.

> 
> Cheers, Lance