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SubjectRe: [PATCH v5 1/4] mm,hwpoison: drain pcplists before bailing out for non-buddy zero-refcount page
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On 10/13/20 4:44 PM, Oscar Salvador wrote:
> A page with 0-refcount and !PageBuddy could perfectly be a pcppage.
> Currently, we bail out with an error if we encounter such a page, meaning
> that we do not handle pcppages neither from hard-offline nor from
> soft-offline path.
>
> Fix this by draining pcplists whenever we find this kind of page and retry
> the check again. It might be that pcplists have been spilled into the
> buddy allocator and so we can handle it.
>
> Signed-off-by: Oscar Salvador <osalvador@suse.de>
> Acked-by: Naoya Horiguchi <naoya.horiguchi@nec.com>

Acked-by: Vlastimil Babka <vbabka@suse.cz>

> ---
> mm/memory-failure.c | 24 ++++++++++++++++++++++--
> 1 file changed, 22 insertions(+), 2 deletions(-)
>
> diff --git a/mm/memory-failure.c b/mm/memory-failure.c
> index c0bb186bba62..e2f12410c594 100644
> --- a/mm/memory-failure.c
> +++ b/mm/memory-failure.c
> @@ -946,13 +946,13 @@ static int page_action(struct page_state *ps, struct page *p,
> }
>
> /**
> - * get_hwpoison_page() - Get refcount for memory error handling:
> + * __get_hwpoison_page() - Get refcount for memory error handling:
> * @page: raw error page (hit by memory error)
> *
> * Return: return 0 if failed to grab the refcount, otherwise true (some
> * non-zero value.)
> */
> -static int get_hwpoison_page(struct page *page)
> +static int __get_hwpoison_page(struct page *page)
> {
> struct page *head = compound_head(page);
>
> @@ -982,6 +982,26 @@ static int get_hwpoison_page(struct page *page)
> return 0;
> }
>
> +static int get_hwpoison_page(struct page *p)
> +{
> + int ret;
> + bool drained = false;
> +
> +retry:
> + ret = __get_hwpoison_page(p);
> + if (!ret && !is_free_buddy_page(p) && !page_count(p) && !drained) {
> + /*
> + * The page might be in a pcplist, so try to drain those
> + * and see if we are lucky.
> + */
> + drain_all_pages(page_zone(p));
> + drained = true;
> + goto retry;
> + }
> +
> + return ret;
> +}
> +
> /*
> * Do all that is necessary to remove user space mappings. Unmap
> * the pages and send SIGBUS to the processes if the data was dirty.
>

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