diff --git a/mm/memory.c b/mm/memory.c
index a54b2c498444dca8d8b41bb59d65640915f1a684..db09106ed44b7a4aa46d058c76d89a84d1322b42 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -2553,6 +2553,10 @@ static int do_swap_page(struct mm_struct *mm, struct vm_area_struct *vma,
 		ret = VM_FAULT_MAJOR;
 		count_vm_event(PGMAJFAULT);
 	} else if (PageHWPoison(page)) {
+		/*
+		 * hwpoisoned dirty swapcache pages are kept for killing
+		 * owner processes (which may be unknown at hwpoison time)
+		 */
 		ret = VM_FAULT_HWPOISON;
 		delayacct_clear_flag(DELAYACCT_PF_SWAPIN);
 		goto out_release;