1 files changed, 5 insertions, 0 deletions

diff --git a/mm/debug.c b/mm/debug.c
index 74c7cae4f683..9feb699c5d25 100644
--- a/mm/debug.c
+++ b/mm/debug.c
@@ -42,6 +42,11 @@ const struct trace_print_flags vmaflag_names[] = {
 
 void __dump_page(struct page *page, const char *reason)
 {
+        /*
+         * Avoid VM_BUG_ON() in page_mapcount().
+         * page->_mapcount space in struct page is used by sl[aou]b pages to
+         * encode own info.
+         */
         int mapcount = PageSlab(page) ? 0 : page_mapcount(page);
 
         pr_emerg("page:%p count:%d mapcount:%d mapping:%p index:%#lx",