On 12 Jan 2022, at 6:01, David Hildenbrand wrote:
> On 05.01.22 22:47, Zi Yan wrote:
>> From: Zi Yan <ziy@xxxxxxxxxx>
>>
>> In isolate_migratepages_block(), a !PageLRU tail page can be encountered
>> when the page is larger than a pageblock. Use compound head page for the
>> checks inside and skip the entire compound page when isolation succeeds.
>>
>
> This will currently never happen, due to the way we always isolate
> MAX_ORDER -1 ranges, correct?
You are right.
>
> Better note that in the patch description, because currently it reads
> like it's an actual fix "can be encountered".
>
Will do. This is a preparation patch for the upcoming commits.
>> Signed-off-by: Zi Yan <ziy@xxxxxxxxxx>
>> ---
>> mm/compaction.c | 10 +++++++---
>> 1 file changed, 7 insertions(+), 3 deletions(-)
>>
>> diff --git a/mm/compaction.c b/mm/compaction.c
>> index b4e94cda3019..ad9053fbbe06 100644
>> --- a/mm/compaction.c
>> +++ b/mm/compaction.c
>> @@ -979,19 +979,23 @@ isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn,
>> * Skip any other type of page
>> */
>> if (!PageLRU(page)) {
>> + struct page *head = compound_head(page);
>> /*
>> * __PageMovable can return false positive so we need
>> * to verify it under page_lock.
>> */
>> - if (unlikely(__PageMovable(page)) &&
>> - !PageIsolated(page)) {
>> + if (unlikely(__PageMovable(head)) &&
>> + !PageIsolated(head)) {
>> if (locked) {
>> unlock_page_lruvec_irqrestore(locked, flags);
>> locked = NULL;
>> }
>>
>> - if (!isolate_movable_page(page, isolate_mode))
>> + if (!isolate_movable_page(head, isolate_mode)) {
>> + low_pfn += (1 << compound_order(head)) - 1 - (page - head);
>> + page = head;
>> goto isolate_success;
>> + }
>> }
>>
>> goto isolate_fail;
>
>
> --
> Thanks,
>
> David / dhildenb
--
Best Regards,
Yan, Zi
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