On Fri 20-11-20 14:43:19, Muchun Song wrote:
> Because we reuse the first tail page, if we set PageHWPosion on a
> tail page. It indicates that we may set PageHWPoison on a series
> of pages. So we can use the head[4].mapping to record the real
> error page index and set the raw error page PageHWPoison later.
This really begs more explanation. Maybe I misremember but If there
is a HWPoison hole in a hugepage then the whole page is demolished, no?
If that is the case then why do we care about tail pages?
> Signed-off-by: Muchun Song <songmuc...@bytedance.com>
> ---
> mm/hugetlb.c | 11 +++--------
> mm/hugetlb_vmemmap.h | 39 +++++++++++++++++++++++++++++++++++++++
> 2 files changed, 42 insertions(+), 8 deletions(-)
>
> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> index 055604d07046..b853aacd5c16 100644
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
> @@ -1383,6 +1383,7 @@ static void __free_hugepage(struct hstate *h, struct
> page *page)
> int i;
>
> alloc_huge_page_vmemmap(h, page);
> + subpage_hwpoison_deliver(page);
>
> for (i = 0; i < pages_per_huge_page(h); i++) {
> page[i].flags &= ~(1 << PG_locked | 1 << PG_error |
> @@ -1944,14 +1945,8 @@ int dissolve_free_huge_page(struct page *page)
> int nid = page_to_nid(head);
> if (h->free_huge_pages - h->resv_huge_pages == 0)
> goto out;
> - /*
> - * Move PageHWPoison flag from head page to the raw error page,
> - * which makes any subpages rather than the error page reusable.
> - */
> - if (PageHWPoison(head) && page != head) {
> - SetPageHWPoison(page);
> - ClearPageHWPoison(head);
> - }
> +
> + set_subpage_hwpoison(head, page);
> list_del(&head->lru);
> h->free_huge_pages--;
> h->free_huge_pages_node[nid]--;
> diff --git a/mm/hugetlb_vmemmap.h b/mm/hugetlb_vmemmap.h
> index 779d3cb9333f..65e94436ffff 100644
> --- a/mm/hugetlb_vmemmap.h
> +++ b/mm/hugetlb_vmemmap.h
> @@ -20,6 +20,29 @@ void __init gather_vmemmap_pgtable_init(struct
> huge_bootmem_page *m,
> void alloc_huge_page_vmemmap(struct hstate *h, struct page *head);
> void free_huge_page_vmemmap(struct hstate *h, struct page *head);
>
> +static inline void subpage_hwpoison_deliver(struct page *head)
> +{
> + struct page *page = head;
> +
> + if (PageHWPoison(head))
> + page = head + page_private(head + 4);
> +
> + /*
> + * Move PageHWPoison flag from head page to the raw error page,
> + * which makes any subpages rather than the error page reusable.
> + */
> + if (page != head) {
> + SetPageHWPoison(page);
> + ClearPageHWPoison(head);
> + }
> +}
> +
> +static inline void set_subpage_hwpoison(struct page *head, struct page *page)
> +{
> + if (PageHWPoison(head))
> + set_page_private(head + 4, page - head);
> +}
> +
> static inline unsigned int free_vmemmap_pages_per_hpage(struct hstate *h)
> {
> return h->nr_free_vmemmap_pages;
> @@ -56,6 +79,22 @@ static inline void free_huge_page_vmemmap(struct hstate
> *h, struct page *head)
> {
> }
>
> +static inline void subpage_hwpoison_deliver(struct page *head)
> +{
> +}
> +
> +static inline void set_subpage_hwpoison(struct page *head, struct page *page)
> +{
> + /*
> + * Move PageHWPoison flag from head page to the raw error page,
> + * which makes any subpages rather than the error page reusable.
> + */
> + if (PageHWPoison(head) && page != head) {
> + SetPageHWPoison(page);
> + ClearPageHWPoison(head);
> + }
> +}
> +
> static inline unsigned int free_vmemmap_pages_per_hpage(struct hstate *h)
> {
> return 0;
> --
> 2.11.0
>
--
Michal Hocko
SUSE Labs
