Re: [PATCH v2] mm/page_vma_mapped_walk: Use ptep_get_lockless() for lockless access

[Wei Yang]

On Fri, May 08, 2026 at 07:15:45AM +0200, Alexander Gordeev wrote:
>On Fri, May 08, 2026 at 01:00:40AM +0000, Wei Yang wrote:
>> On Thu, May 07, 2026 at 12:32:09PM +0200, Alexander Gordeev wrote:
>> >On Thu, May 07, 2026 at 09:34:33AM +0000, Wei Yang wrote:
>> >> >@@ -310,7 +310,7 @@ bool page_vma_mapped_walk(struct page_vma_mapped_walk *pvmw)
>> >> > 				goto restart;
>> >> > 			}
>> >> > 			pvmw->pte++;
>> >> >-		} while (pte_none(ptep_get(pvmw->pte)));
>> >> >+		} while (pte_none(ptep_get_lockless(pvmw->pte)));
>> >> 
>> >> As Oscar mentioned in lkml.org/lkml/2026/4/27/630, map_pte() may take the
>> >> lock. So probably it is not right?
>> >
>> >If I read the code correctly map_pte() might take the lock, but also
>> >might not take it. If it took the lock and uses ptep_get_lockless(),
>> >then it is fine. But if it did not take the lock and uses ptep_get(),
>> >then it is an issue.
>> >
>> 
>> So the rule here is:
>> 
>>   * ptep_get_lockless() could be used for locked and not locked
>>   * ptep_get() only used when locked
>> 
>> Right?
>
>Yes, this is my assumption.
>

Thanks, if so, it looks good.

>> >> > 
>> >> > 		if (!pvmw->ptl) {
>> >> > 			spin_lock(ptl);
>> >> >-- 
>> >> >2.51.0
>> >> >
>> >> 
>> >> -- 
>> >> Wei Yang
>> >
>> >Thanks!
>> 
>> -- 
>> Wei Yang
>> Help you, Help me

-- 
Wei Yang
Help you, Help me