vmscan: split file huge pages before paging them out

This is preparation of vmscan for file huge pages.  We cannot write out
huge pages, so we need to split them on the way out.

Link: http://lkml.kernel.org/r/1466021202-61880-22-git-send-email-kirill.shutemov@linux.intel.com
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 93ba33789ac69af390e62802d25211fc9c54e29e..21d417ccff69d4efb8154d78c976b97e353a3609 100644 (file)
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -1055,8 +1055,14 @@ static unsigned long shrink_page_list(struct list_head *page_list,
 
                        /* Adding to swap updated mapping */
                        mapping = page_mapping(page);
+               } else if (unlikely(PageTransHuge(page))) {
+                       /* Split file THP */
+                       if (split_huge_page_to_list(page, page_list))
+                               goto keep_locked;
                }
 
+               VM_BUG_ON_PAGE(PageTransHuge(page), page);
+
                /*
                 * The page is mapped into the page tables of one or more
                 * processes. Try to unmap it here.