On Wed, Aug 07, 2024 at 02:46:46PM +0100, Usama Arif wrote:
> From: Yu Zhao <yuzhao@xxxxxxxxxx>
>
> If a tail page has only two references left, one inherited from the
> isolation of its head and the other from lru_add_page_tail() which we
> are about to drop, it means this tail page was concurrently zapped.
> Then we can safely free it and save page reclaim or migration the
> trouble of trying it.
>
> Signed-off-by: Yu Zhao <yuzhao@xxxxxxxxxx>
> Tested-by: Shuang Zhai <zhais@xxxxxxxxxx>
> Signed-off-by: Usama Arif <usamaarif642@xxxxxxxxx>
> ---
> mm/huge_memory.c | 27 +++++++++++++++++++++++++++
> 1 file changed, 27 insertions(+)
>
> diff --git a/mm/huge_memory.c b/mm/huge_memory.c
> index 0167dc27e365..35c1089d8d61 100644
> --- a/mm/huge_memory.c
> +++ b/mm/huge_memory.c
> @@ -2923,7 +2923,9 @@ static void __split_huge_page(struct page *page, struct list_head *list,
> unsigned int new_nr = 1 << new_order;
> int order = folio_order(folio);
> unsigned int nr = 1 << order;
> + struct folio_batch free_folios;
>
> + folio_batch_init(&free_folios);
> /* complete memcg works before add pages to LRU */
> split_page_memcg(head, order, new_order);
>
> @@ -3007,6 +3009,26 @@ static void __split_huge_page(struct page *page, struct list_head *list,
> if (subpage == page)
> continue;
> folio_unlock(new_folio);
> + /*
> + * If a folio has only two references left, one inherited
> + * from the isolation of its head and the other from
> + * lru_add_page_tail() which we are about to drop, it means this
> + * folio was concurrently zapped. Then we can safely free it
> + * and save page reclaim or migration the trouble of trying it.
> + */
> + if (list && page_ref_freeze(subpage, 2)) {
folio_ref_freeze(new_folio, 2)?
Otherwise looks good to me
Acked-by: Johannes Weiner <hannes@xxxxxxxxxxx>
