On 2023/7/5 0:38, Andrew Morton wrote:
> On Tue, 4 Jul 2023 20:36:00 +0800 Miaohe Lin <linmiaohe@xxxxxxxxxx> wrote:
>
>> On 2023/7/4 20:13, Matthew Wilcox wrote:
>>> On Tue, Jul 04, 2023 at 07:18:23PM +0800, Miaohe Lin wrote:
>>>> @@ -470,6 +470,8 @@ static int page_outside_zone_boundaries(struct zone *zone, struct page *page)
>>>> sp = zone->spanned_pages;
>>>> if (!zone_spans_pfn(zone, pfn))
>>>> ret = 1;
>>>> + else
>>>> + ret = 0;
>>>
>>> Surely 'ret = zone_spans_pfn(zone, pfn);' ?
>>
>> Do you mean 'ret = !zone_spans_pfn(zone, pfn);'? This format looks fine to me.
>>
>>>
>>> Also, did you spot this by inspection or do you have a test-case or bug
>>> report? Should this have a Fixes: tag?
>>
>> This is from code inspection. The race window should be really small thus hard to trigger
>> in real world. And yes, it seems Fixes tag is a really ancient commit:
>>
>> Fixes: bdc8cb984576 ("[PATCH] memory hotplug locking: zone span seqlock")
>>
>
> Thanks. I updated the changelog:
>
> : If pfn is outside zone boundaries in the first round, ret will be set to
> : 1. But if pfn is changed to inside the zone boundaries in zone span
> : seqretry path, ret is still set to 1 leading to false page outside zone
> : error info.
> :
> : This is from code inspection. The race window should be really small thus
> : hard to trigger in real world.
> :
> : Link: https://lkml.kernel.org/r/20230704111823.940331-1-linmiaohe@xxxxxxxxxx
> : Fixes: bdc8cb984576 ("[PATCH] memory hotplug locking: zone span seqlock")
>
> and I made the change suggested by Matthew:
>
> --- a/mm/page_alloc.c~mm-page_alloc-avoid-false-page-outside-zone-error-info-fix
> +++ a/mm/page_alloc.c
> @@ -468,10 +468,7 @@ static int page_outside_zone_boundaries(
> seq = zone_span_seqbegin(zone);
> start_pfn = zone->zone_start_pfn;
> sp = zone->spanned_pages;
> - if (!zone_spans_pfn(zone, pfn))
> - ret = 1;
> - else
> - ret = 0;
> + ret = !zone_spans_pfn(zone, pfn);
> } while (zone_span_seqretry(zone, seq));
These changes look good to me. Thanks for doing this.
