Re: [v2 PATCH 2/2] mm: mempolicy: handle vma with unmovable pages mapped correctly in mbind

Vlastimil Babka
2019-07-16T12:07:33Z

On 6/22/19 2:20 AM, Yang Shi wrote:
> @@ -969,10 +975,21 @@ static long do_get_mempolicy(int *policy, nodemask_t *nmask,
> /*
> * page migration, thp tail pages can be passed.
> */
> -static void migrate_page_add(struct page *page, struct list_head *pagelist,
> +static int migrate_page_add(struct page *page, struct list_head *pagelist,
> unsigned long flags)
> {
> struct page *head = compound_head(page);
> +
> + /*
> + * Non-movable page may reach here. And, there may be
> + * temporaty off LRU pages or non-LRU movable pages.
> + * Treat them as unmovable pages since they can't be
> + * isolated, so they can't be moved at the moment. It
> + * should return -EIO for this case too.
> + */
> + if (!PageLRU(head) && (flags & MPOL_MF_STRICT))
> + return -EIO;
> +

Hm but !PageLRU() is not the only way why queueing for migration can
fail, as can be seen from the rest of the function. Shouldn't all cases
be reported?

> /*
> * Avoid migrating a page that is shared with others.
> */
> @@ -984,6 +1001,8 @@ static void migrate_page_add(struct page *page, struct list_head *pagelist,
> hpage_nr_pages(head));
> }
> }
> +
> + return 0;
> }
>
> /* page allocation callback for NUMA node migration */
> @@ -1186,9 +1205,10 @@ static struct page *new_page(struct page *page, unsigned long start)
> }
> #else
>
> -static void migrate_page_add(struct page *page, struct list_head *pagelist,
> +static int migrate_page_add(struct page *page, struct list_head *pagelist,
> unsigned long flags)
> {
> + return -EIO;
> }
>
> int do_migrate_pages(struct mm_struct *mm, const nodemask_t *from,
>