[PATCH v12 3/6] mm/hwpoison: return -EFAULT when copy fail in copy_mc_[user]_highpage()

[Tong Tiangen]

If hardware errors are encountered during page copying, returning the bytes
not copied is not meaningful, and the caller cannot do any processing on
the remaining data. Returning -EFAULT is more reasonable, which represents
a hardware error encountered during the copying.

Signed-off-by: Tong Tiangen <tongtiangen at huawei.com>
---
 include/linux/highmem.h | 8 ++++----
 mm/khugepaged.c         | 4 ++--
 2 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/include/linux/highmem.h b/include/linux/highmem.h
index 00341b56d291..64a567d5ad6f 100644
--- a/include/linux/highmem.h
+++ b/include/linux/highmem.h
@@ -335,8 +335,8 @@ static inline void copy_highpage(struct page *to, struct page *from)
 /*
  * 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.
+ * page with #MC in source page (@from) handled, and return -EFAULT 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)
@@ -352,7 +352,7 @@ static inline int copy_mc_user_highpage(struct page *to, struct page *from,
 	kunmap_local(vto);
 	kunmap_local(vfrom);
 
-	return ret;
+	return ret ? -EFAULT : 0;
 }
 
 static inline int copy_mc_highpage(struct page *to, struct page *from)
@@ -368,7 +368,7 @@ static inline int copy_mc_highpage(struct page *to, struct page *from)
 	kunmap_local(vto);
 	kunmap_local(vfrom);
 
-	return ret;
+	return ret ? -EFAULT : 0;
 }
 #else
 static inline int copy_mc_user_highpage(struct page *to, struct page *from,
diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index 774a97e6e2da..cce838e85967 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -798,7 +798,7 @@ static int __collapse_huge_page_copy(pte_t *pte, struct folio *folio,
 			continue;
 		}
 		src_page = pte_page(pteval);
-		if (copy_mc_user_highpage(page, src_page, src_addr, vma) > 0) {
+		if (copy_mc_user_highpage(page, src_page, src_addr, vma)) {
 			result = SCAN_COPY_MC;
 			break;
 		}
@@ -2042,7 +2042,7 @@ static int collapse_file(struct mm_struct *mm, unsigned long addr,
 			index++;
 			dst++;
 		}
-		if (copy_mc_highpage(dst, folio_page(folio, 0)) > 0) {
+		if (copy_mc_highpage(dst, folio_page(folio, 0))) {
 			result = SCAN_COPY_MC;
 			goto rollback;
 		}
-- 
2.25.1