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?
Better note that in the patch description, because currently it reads
like it's an actual fix "can be encountered".
> 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
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