Re: [PATCH 1/1] mm/page_alloc: add scheduling point to free_unref_page_list

[Matthew Wilcox]

On Tue, Mar 01, 2022 at 08:38:25PM -0500, wangjianxing wrote:
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index 3589febc6..1b96421c8 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -3479,6 +3479,9 @@ void free_unref_page_list(struct list_head *list)
>  		 */
>  		if (++batch_count == SWAP_CLUSTER_MAX) {
>  			local_unlock_irqrestore(&pagesets.lock, flags);
> +
> +			cond_resched();

This isn't safe.  This path can be called from interrupt context
(otherwise we'd be using local_unlock_irq() instead of irqrestore()).