mm: migrate: drop unused argument of migrate_page_move_mapping()

All callers of migrate_page_move_mapping() now pass NULL for 'head'
argument.  Drop it.

Link: http://lkml.kernel.org/r/20181211172143.7358-7-jack@suse.cz
Signed-off-by: Jan Kara <jack@suse.cz>
Acked-by: Mel Gorman <mgorman@suse.de>
Cc: Michal Hocko <mhocko@suse.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/mm/migrate.c b/mm/migrate.c
index 8dd5760..4389696 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -399,8 +399,7 @@ static int expected_page_refs(struct page *page)
  * 3 for pages with a mapping and PagePrivate/PagePrivate2 set.
  */
 int migrate_page_move_mapping(struct address_space *mapping,
-		struct page *newpage, struct page *page,
-		struct buffer_head *head, enum migrate_mode mode,
+		struct page *newpage, struct page *page, enum migrate_mode mode,
 		int extra_count)
 {
 	XA_STATE(xas, &mapping->i_pages, page_index(page));
@@ -687,7 +686,7 @@ int migrate_page(struct address_space *mapping,
 
 	BUG_ON(PageWriteback(page));	/* Writeback must be complete */
 
-	rc = migrate_page_move_mapping(mapping, newpage, page, NULL, mode, 0);
+	rc = migrate_page_move_mapping(mapping, newpage, page, mode, 0);
 
 	if (rc != MIGRATEPAGE_SUCCESS)
 		return rc;
@@ -790,7 +789,7 @@ static int __buffer_migrate_page(struct address_space *mapping,
 		}
 	}
 
-	rc = migrate_page_move_mapping(mapping, newpage, page, NULL, mode, 0);
+	rc = migrate_page_move_mapping(mapping, newpage, page, mode, 0);
 	if (rc != MIGRATEPAGE_SUCCESS)
 		goto unlock_buffers;