mm/huge_memory: use helper macro IS_ERR_OR_NULL in split_huge_pages_pid

Use helper macro IS_ERR_OR_NULL to check the validity of page to simplify
the code. Minor readability improvement.

Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Miaohe Lin <[email protected]>
Reviewed-by: Muchun Song <[email protected]>
Cc: Matthew Wilcox <[email protected]>
Cc: Yang Shi <[email protected]>
Cc: Zach O'Keefe <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

Author: MiaoheLin

mm/huge_memory.c

@@ -2958,9 +2958,7 @@ static int split_huge_pages_pid(int pid, unsigned long vaddr_start,
 		/* FOLL_DUMP to ignore special (like zero) pages */
 		page = follow_page(vma, addr, FOLL_GET | FOLL_DUMP);
 
-		if (IS_ERR(page))
-			continue;
-		if (!page || is_zone_device_page(page))
+		if (IS_ERR_OR_NULL(page) || is_zone_device_page(page))
 			continue;
 
 		if (!is_transparent_hugepage(page))