[PATCH 2/4] mm: Handle hugetlb correctly in is_page_hwpoison()

["Matthew Wilcox (Oracle)" <willy@infradead.org>]

Checking to see whether a page inside a hugetlb folio is hardware
poisoned is more complicated than I realised.  The correct logic was
in is_raw_hwpoison_page_in_hugepage().  Make is_page_hwpoison() the
official entry point for "is this page hwpoison", no matter what kind
of folio it belongs to.  Rename is_raw_hwpoison_page_in_hugepage() to
hugetlb_page_hwpoison(), and remove the attempt to handle non-hugetlb
folios from it.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
---
 fs/hugetlbfs/inode.c       |  4 ++--
 include/linux/hugetlb.h    |  5 -----
 include/linux/page-flags.h | 24 +++++++++++++++++++-----
 mm/memory-failure.c        |  9 ++++-----
 4 files changed, 25 insertions(+), 17 deletions(-)

diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c
index 1760df6f2709..725bb945a440 100644
--- a/fs/hugetlbfs/inode.c
+++ b/fs/hugetlbfs/inode.c
@@ -198,7 +198,7 @@ static size_t adjust_range_hwpoison(struct folio *folio, size_t offset,
 	struct page *page = folio_page(folio, offset / PAGE_SIZE);
 	size_t safe_bytes;
 
-	if (is_raw_hwpoison_page_in_hugepage(page))
+	if (hugetlb_page_hwpoison(folio, page))
 		return 0;
 	/* Safe to read the remaining bytes in this page. */
 	safe_bytes = PAGE_SIZE - (offset % PAGE_SIZE);
@@ -206,7 +206,7 @@ static size_t adjust_range_hwpoison(struct folio *folio, size_t offset,
 
 	/* Check each remaining page as long as we are not done yet. */
 	for (; safe_bytes < bytes; safe_bytes += PAGE_SIZE, page++)
-		if (is_raw_hwpoison_page_in_hugepage(page))
+		if (hugetlb_page_hwpoison(folio, page))
 			break;
 
 	return min(safe_bytes, bytes);
diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
index 2abaf99321e9..5df0bb618b05 100644
--- a/include/linux/hugetlb.h
+++ b/include/linux/hugetlb.h
@@ -1070,11 +1070,6 @@ void hugetlb_register_node(struct node *node);
 void hugetlb_unregister_node(struct node *node);
 #endif
 
-/*
- * Check if a given raw @page in a hugepage is HWPOISON.
- */
-bool is_raw_hwpoison_page_in_hugepage(struct page *page);
-
 static inline unsigned long huge_page_mask_align(struct file *file)
 {
 	return PAGE_MASK & ~huge_page_mask(hstate_file(file));
diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h
index 7223f6f4e2b4..b0b451b4e632 100644
--- a/include/linux/page-flags.h
+++ b/include/linux/page-flags.h
@@ -1068,6 +1068,9 @@ static inline bool PageHuge(const struct page *page)
 	return folio_test_hugetlb(page_folio(page));
 }
 
+#ifdef CONFIG_MEMORY_FAILURE
+bool hugetlb_page_hwpoison(const struct folio *folio, const struct page *page);
+
 /*
  * Check if a page is currently marked HWPoisoned. Note that this check is
  * best effort only and inherently racy: there is no way to synchronize with
@@ -1075,13 +1078,24 @@ static inline bool PageHuge(const struct page *page)
  */
 static inline bool is_page_hwpoison(const struct page *page)
 {
-	const struct folio *folio;
+	const struct folio *folio = page_folio(page);
+
+	if (folio_test_hugetlb(folio))
+		return hugetlb_page_hwpoison(folio, page);
+	return PageHWPoison(page);
+}
+#else
+static inline bool hugetlb_page_hwpoison(const struct folio *folio,
+		const struct page *page)
+{
+	return false;
+}
 
-	if (PageHWPoison(page))
-		return true;
-	folio = page_folio(page);
-	return folio_test_hugetlb(folio) && PageHWPoison(&folio->page);
+static inline bool is_page_hwpoison(const struct page *page)
+{
+	return false;
 }
+#endif
 
 static inline bool folio_contain_hwpoisoned_page(struct folio *folio)
 {
diff --git a/mm/memory-failure.c b/mm/memory-failure.c
index 51508a55c405..0980791108a4 100644
--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -1822,19 +1822,18 @@ static inline struct llist_head *raw_hwp_list_head(struct folio *folio)
 	return (struct llist_head *)&folio->_hugetlb_hwpoison;
 }
 
-bool is_raw_hwpoison_page_in_hugepage(struct page *page)
+/*
+ * Check if a given @page in a hugetlb folio is HWPOISON.
+ */
+bool hugetlb_page_hwpoison(const struct folio *folio, const struct page *page)
 {
 	struct llist_head *raw_hwp_head;
 	struct raw_hwp_page *p;
-	struct folio *folio = page_folio(page);
 	bool ret = false;
 
 	if (!folio_test_hwpoison(folio))
 		return false;
 
-	if (!folio_test_hugetlb(folio))
-		return PageHWPoison(page);
-
 	/*
 	 * When RawHwpUnreliable is set, kernel lost track of which subpages
 	 * are HWPOISON. So return as if ALL subpages are HWPOISONed.
-- 
2.47.3