Re: [PATCH v3 1/3] mm: mprotect: always skip dma pinned folio in prot_numa_skip()

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

On 2025/10/15 23:32, Lorenzo Stoakes wrote:
> On Wed, Oct 15, 2025 at 08:35:14PM +0800, Kefeng Wang wrote:
>> If the folio(even not CoW folio) is dma pinned, it can't be
>> migrated, so always skip pinned folio to avoid a waste of cycles
>> when folios migration.
> 
> NIT: 'when folios migration' -> 'when folios are migrated'.
> 
> Maybe worth saying 'due to elevated reference count?'
> 

Hope Andrew could help to update the changelog.

>>
>> Reviewed-by: Sidhartha Kumar <sidhartha.kumar@oracle.com>
>> Acked-by: David Hildenbrand <david@redhat.com>
>> Reviewed-by: Lance Yang <lance.yang@linux.dev>
>> Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
> 
> LGTM though so:
> 
> Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>

Thanks all.

> 
>> ---
>>   mm/mprotect.c | 9 ++++++---
>>   1 file changed, 6 insertions(+), 3 deletions(-)
>>
>> diff --git a/mm/mprotect.c b/mm/mprotect.c
>> index 113b48985834..bb59a42809b8 100644
>> --- a/mm/mprotect.c
>> +++ b/mm/mprotect.c
>> @@ -136,9 +136,12 @@ static bool prot_numa_skip(struct vm_area_struct *vma, unsigned long addr,
>>   	if (folio_is_zone_device(folio) || folio_test_ksm(folio))
>>   		goto skip;
>>
>> -	/* Also skip shared copy-on-write pages */
>> -	if (is_cow_mapping(vma->vm_flags) &&
>> -	    (folio_maybe_dma_pinned(folio) || folio_maybe_mapped_shared(folio)))
>> +	/* Also skip shared copy-on-write folios */
>> +	if (is_cow_mapping(vma->vm_flags) && folio_maybe_mapped_shared(folio))
>> +		goto skip;
>> +
>> +	/* Folios are pinned and can't be migrated */
>> +	if (folio_maybe_dma_pinned(folio))
>>   		goto skip;
>>
>>   	/*
>> --
>> 2.27.0
>>
>>
>