[RFC PATCH 18/24] mm/hugetlb: Clear PageHWPoison on the non-error memory page

[Muchun Song <songmuchun@bytedance.com>]

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 need to clear PageHWPoison on the non-error pages.
We use the head[3].mapping to record the real error page index and
clear non-error page PageHWPoison later.

Signed-off-by: Muchun Song <songmuchun@bytedance.com>
---
 mm/hugetlb.c | 33 +++++++++++++++++++++++++++++++++
 1 file changed, 33 insertions(+)

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 34706cec21ec..8666cedf9a7b 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -1847,6 +1847,21 @@ static inline void free_gigantic_page_comm(struct hstate *h, struct page *page)
 {
 	free_gigantic_page(page, huge_page_order(h));
 }
+
+static inline bool subpage_hwpoison(struct page *head, struct page *page)
+{
+	return page_private(head + 4) == page - head;
+}
+
+static inline void set_subpage_hwpoison(struct page *head, struct page *page)
+{
+	set_page_private(head + 4, page - head);
+}
+
+static inline void clear_subpage_hwpoison(struct page *head)
+{
+	set_page_private(head + 4, 0);
+}
 #else
 static inline void hugetlb_vmemmap_init(struct hstate *h)
 {
@@ -1894,6 +1909,19 @@ static inline void free_gigantic_page_comm(struct hstate *h, struct page *page)
 	free_gigantic_page(page, huge_page_order(h));
 	spin_lock(&hugetlb_lock);
 }
+
+static inline bool subpage_hwpoison(struct page *head, struct page *page)
+{
+	return true;
+}
+
+static inline void set_subpage_hwpoison(struct page *head, struct page *page)
+{
+}
+
+static inline void clear_subpage_hwpoison(struct page *head)
+{
+}
 #endif
 
 static void update_and_free_page(struct hstate *h, struct page *page)
@@ -1918,6 +1946,9 @@ static void __free_hugepage(struct hstate *h, struct page *page)
 				1 << PG_referenced | 1 << PG_dirty |
 				1 << PG_active | 1 << PG_private |
 				1 << PG_writeback);
+
+		if (PageHWPoison(page + i) && !subpage_hwpoison(page, page + i))
+			ClearPageHWPoison(page + i);
 	}
 	VM_BUG_ON_PAGE(hugetlb_cgroup_from_page(page), page);
 	VM_BUG_ON_PAGE(hugetlb_cgroup_from_page_rsvd(page), page);
@@ -2107,6 +2138,7 @@ static void prep_new_huge_page(struct hstate *h, struct page *page, int nid)
 	free_huge_page_vmemmap(h, page);
 	/* Must be called before the initialization of @page->lru */
 	vmemmap_pgtable_free(h, page);
+	clear_subpage_hwpoison(page);
 
 	INIT_LIST_HEAD(&page->lru);
 	set_compound_page_dtor(page, HUGETLB_PAGE_DTOR);
@@ -2477,6 +2509,7 @@ int dissolve_free_huge_page(struct page *page)
 			SetPageHWPoison(page);
 			ClearPageHWPoison(head);
 		}
+		set_subpage_hwpoison(head, page);
 		list_del(&head->lru);
 		h->free_huge_pages--;
 		h->free_huge_pages_node[nid]--;
-- 
2.20.1