[PATCH v10 2/3] mm/hwpoison: introduce copy_mc_highpage

[Jiaqi Yan <jiaqiyan@google.com>]

Similar to how copy_mc_user_highpage is implemented for
copy_user_highpage on #MC supported architecture, introduce
the #MC handled version of copy_highpage.

This helper has immediate usage when khugepaged wants to copy
file-backed memory pages and tolerate #MC.

Signed-off-by: Jiaqi Yan <jiaqiyan@google.com>
---
 include/linux/highmem.h | 54 +++++++++++++++++++++++++++++++----------
 1 file changed, 41 insertions(+), 13 deletions(-)

diff --git a/include/linux/highmem.h b/include/linux/highmem.h
index 1128b7114931f..7cbecae39b3eb 100644
--- a/include/linux/highmem.h
+++ b/include/linux/highmem.h
@@ -315,7 +315,29 @@ static inline void copy_user_highpage(struct page *to, struct page *from,
 
 #endif
 
+#ifndef __HAVE_ARCH_COPY_HIGHPAGE
+
+static inline void copy_highpage(struct page *to, struct page *from)
+{
+	char *vfrom, *vto;
+
+	vfrom = kmap_local_page(from);
+	vto = kmap_local_page(to);
+	copy_page(vto, vfrom);
+	kmsan_copy_page_meta(to, from);
+	kunmap_local(vto);
+	kunmap_local(vfrom);
+}
+
+#endif
+
 #ifdef copy_mc_to_kernel
+/*
+ * If architecture supports machine check exception handling, define the
+ * #MC versions of copy_user_highpage and copy_highpage. They copy a memory
+ * page with #MC in source page (@from) handled, and return the number
+ * of bytes not copied if there was a #MC, otherwise 0 for success.
+ */
 static inline int copy_mc_user_highpage(struct page *to, struct page *from,
 					unsigned long vaddr, struct vm_area_struct *vma)
 {
@@ -332,29 +354,35 @@ static inline int copy_mc_user_highpage(struct page *to, struct page *from,
 
 	return ret;
 }
-#else
-static inline int copy_mc_user_highpage(struct page *to, struct page *from,
-					unsigned long vaddr, struct vm_area_struct *vma)
-{
-	copy_user_highpage(to, from, vaddr, vma);
-	return 0;
-}
-#endif
 
-#ifndef __HAVE_ARCH_COPY_HIGHPAGE
-
-static inline void copy_highpage(struct page *to, struct page *from)
+static inline int copy_mc_highpage(struct page *to, struct page *from)
 {
+	unsigned long ret;
 	char *vfrom, *vto;
 
 	vfrom = kmap_local_page(from);
 	vto = kmap_local_page(to);
-	copy_page(vto, vfrom);
-	kmsan_copy_page_meta(to, from);
+	ret = copy_mc_to_kernel(vto, vfrom, PAGE_SIZE);
+	if (!ret)
+		kmsan_copy_page_meta(to, from);
 	kunmap_local(vto);
 	kunmap_local(vfrom);
+
+	return ret;
+}
+#else
+static inline int copy_mc_user_highpage(struct page *to, struct page *from,
+					unsigned long vaddr, struct vm_area_struct *vma)
+{
+	copy_user_highpage(to, from, vaddr, vma);
+	return 0;
 }
 
+static inline int copy_mc_highpage(struct page *to, struct page *from)
+{
+	copy_highpage(to, from);
+	return 0;
+}
 #endif
 
 static inline void memcpy_page(struct page *dst_page, size_t dst_off,
-- 
2.40.0.rc0.216.gc4246ad0f0-goog