linux-kernel - Re: [RFC 06/10] mm: debug_vm_pgtable: use pgtable_has_pmd

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Message-ID: <ab64a25a-0fd8-4e2f-81fb-7f948e0cddbc@kernel.org>
Date: Wed, 3 Dec 2025 23:09:40 +0100
From: "David Hildenbrand (Red Hat)" <david@...nel.org>
To: Luiz Capitulino <luizcap@...hat.com>, linux-kernel@...r.kernel.org,
 linux-mm@...ck.org
Cc: ryan.roberts@....com, akpm@...ux-foundation.org,
 lorenzo.stoakes@...cle.com
Subject: Re: [RFC 06/10] mm: debug_vm_pgtable: use pgtable_has_pmd_leaves()

On 11/17/25 18:40, David Hildenbrand (Red Hat) wrote:
> On 06.11.25 22:28, Luiz Capitulino wrote:
>> debug_vm_pgtable calls has_transparent_hugepage() in multiple places to
>> check if PMD-sized pages are supported, use pgtable_has_pmd_leaves()
> 
> Is that code even dealing with pages? Likely we really only want to
> check whether PMD leaves are supported, independent of any pages.

I recall that some arch protect certain pmd_* helpers under 
CONFIG_TRANSPARENT_HUGEPAGE.

But it's certainly something to explore, to see if we can just get rid 
of that without causing compile-time or runtime issues.

> 
>> instead.
>>
>> Signed-off-by: Luiz Capitulino <luizcap@...hat.com>
>> ---
>>    mm/debug_vm_pgtable.c | 20 ++++++++++----------
>>    1 file changed, 10 insertions(+), 10 deletions(-)
>>
>> diff --git a/mm/debug_vm_pgtable.c b/mm/debug_vm_pgtable.c
>> index 830107b6dd08..241b36c78ac9 100644
>> --- a/mm/debug_vm_pgtable.c
>> +++ b/mm/debug_vm_pgtable.c
>> @@ -170,7 +170,7 @@ static void __init pmd_basic_tests(struct pgtable_debug_args *args, int idx)
>>    	unsigned long val = idx, *ptr = &val;
>>    	pmd_t pmd;
>>    
>> -	if (!has_transparent_hugepage())
>> +	if (!pgtable_has_pmd_leaves())
>>    		return;
> 
> 
> All of these are currently protected by CONFIG_TRANSPARENT_HUGEPAGE, right?

IIUC, yes.


-- 
Cheers

David