mm: memory-failure: fix unexpected return value in soft_offline_page()

When page_handle_poison() fails to handle the hugepage or free page in
retry path, soft_offline_page() will return 0 while -EBUSY is expected in
this case.

Consequently the user will think soft_offline_page succeeds while it in
fact failed.  So the user will not try again later in this case.

Link: https://lkml.kernel.org/r/[email protected]
Fixes: b94e028 ("mm,hwpoison: try to narrow window race for free pages")
Signed-off-by: Miaohe Lin <[email protected]>
Acked-by: Naoya Horiguchi <[email protected]>
Cc: <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

Author: MiaoheLin

mm/memory-failure.c

@@ -2741,10 +2741,13 @@ int soft_offline_page(unsigned long pfn, int flags)
 	if (ret > 0) {
 		ret = soft_offline_in_use_page(page);
 	} else if (ret == 0) {
-		if (!page_handle_poison(page, true, false) && try_again) {
-			try_again = false;
-			flags &= ~MF_COUNT_INCREASED;
-			goto retry;
+		if (!page_handle_poison(page, true, false)) {
+			if (try_again) {
+				try_again = false;
+				flags &= ~MF_COUNT_INCREASED;
+				goto retry;
+			}
+			ret = -EBUSY;
 		}
 	}