On 2021/9/6 17:27, David Hildenbrand wrote:
> On 04.09.21 11:20, Miaohe Lin wrote:
>> In start_isolate_page_range() undo path, pfn_to_online_page() just checks
>> the first pfn in a pageblock while __first_valid_page() will traverse the
>> pageblock until the first online pfn is found. So we may miss the call to
>> unset_migratetype_isolate() in undo path and pages will remain isolated
>> unexpectedly. Fix this by calling undo_isolate_page_range() and this will
>> also help to remove some duplicated codes.
>>
>> Fixes: 2ce13640b3f4 ("mm: __first_valid_page skip over offline pages")
>
> While that is true, we shouldn't ever trigger, neither via cma, virtio-mem nor memory offlining, because essentially all operate on MAX_ORDER -1 -aligned ranges without memory holes.
I think this should never trigger too. It's a theoretical issue. So is the Fixes tag necessary ?
>
>> Signed-off-by: Miaohe Lin <linmiaohe@xxxxxxxxxx>
>> ---
>> mm/page_isolation.c | 9 +--------
>> 1 file changed, 1 insertion(+), 8 deletions(-)
>>
>> diff --git a/mm/page_isolation.c b/mm/page_isolation.c
>> index 471e3a13b541..9bb562d5d194 100644
>> --- a/mm/page_isolation.c
>> +++ b/mm/page_isolation.c
>> @@ -202,14 +202,7 @@ int start_isolate_page_range(unsigned long start_pfn, unsigned long end_pfn,
>> }
>> return 0;
>> undo:
>> - for (pfn = start_pfn;
>> - pfn < undo_pfn;
>> - pfn += pageblock_nr_pages) {
>> - struct page *page = pfn_to_online_page(pfn);
>> - if (!page)
>> - continue;
>> - unset_migratetype_isolate(page, migratetype);
>> - }
>> + undo_isolate_page_range(start_pfn, undo_pfn, migratetype);
>>
>
> It'd be even cleaner to drop the label completely and call it from the single callsite. We can even avoid undo_pfn ...
>
> if (page && set_migratetype_isolate(page, migratetype, flags)) {
> undo_isolate_page_range(start_pfn, pfn, migratetype);
> return -EBUSY;
> }
>
Looks much better. Will do it later. Many thanks. :)
> If pfn == start_pfn, undo_isolate_page_range() will simply do nothing.
>
>> return -EBUSY;
>> }
>>
>
