linux-kernel - Re: [v1 resend 03/12] mm/thp: zone_device awareness in THP handling code

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Message-ID: <5c77bf07-3a8d-4bda-9281-ac9f4bf76381@nvidia.com>
Date: Sun, 6 Jul 2025 11:21:32 +1000
From: Balbir Singh <balbirs@...dia.com>
To: Mika Penttilä <mpenttil@...hat.com>, linux-mm@...ck.org
Cc: akpm@...ux-foundation.org, linux-kernel@...r.kernel.org,
 Karol Herbst <kherbst@...hat.com>, Lyude Paul <lyude@...hat.com>,
 Danilo Krummrich <dakr@...nel.org>, David Airlie <airlied@...il.com>,
 Simona Vetter <simona@...ll.ch>, Jérôme Glisse
 <jglisse@...hat.com>, Shuah Khan <shuah@...nel.org>,
 David Hildenbrand <david@...hat.com>, Barry Song <baohua@...nel.org>,
 Baolin Wang <baolin.wang@...ux.alibaba.com>,
 Ryan Roberts <ryan.roberts@....com>, Matthew Wilcox <willy@...radead.org>,
 Peter Xu <peterx@...hat.com>, Zi Yan <ziy@...dia.com>,
 Kefeng Wang <wangkefeng.wang@...wei.com>, Jane Chu <jane.chu@...cle.com>,
 Alistair Popple <apopple@...dia.com>, Donet Tom <donettom@...ux.ibm.com>
Subject: Re: [v1 resend 03/12] mm/thp: zone_device awareness in THP handling
 code

On 7/4/25 14:46, Mika Penttilä wrote:
> On 7/4/25 02:35, Balbir Singh wrote:
>>  
>> @@ -2899,20 +2923,25 @@ static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd,
>>  		return __split_huge_zero_page_pmd(vma, haddr, pmd);
>>  	}
>>  
>> -	pmd_migration = is_pmd_migration_entry(*pmd);
>> -	if (unlikely(pmd_migration)) {
>> -		swp_entry_t entry;
>>  
>> +	present = pmd_present(*pmd);
>> +	if (unlikely(!present)) {
>> +		swp_entry = pmd_to_swp_entry(*pmd);
>>  		old_pmd = *pmd;
>> -		entry = pmd_to_swp_entry(old_pmd);
>> -		page = pfn_swap_entry_to_page(entry);
>> -		write = is_writable_migration_entry(entry);
>> +
>> +		folio = pfn_swap_entry_folio(swp_entry);
>> +		VM_BUG_ON(!is_migration_entry(swp_entry) &&
>> +				!is_device_private_entry(swp_entry));
>> +		page = pfn_swap_entry_to_page(swp_entry);
>> +		write = is_writable_migration_entry(swp_entry);
> 
> Shouldn't write include is_writable_device_private_entry() also?
> 
> 

Good point, will fix.

Balbir