ceph: clear page dirty before invalidate page

clear_page_dirty_for_io(page) before mapping->a_ops->invalidatepage().
invalidatepage() clears page's private flag, if dirty flag is not
cleared, the page may cause BUG_ON failure in ceph_set_page_dirty().

Cc: stable@vger.kernel.org
Link: https://tracker.ceph.com/issues/40862Signed-off-by: Erqi Chen <chenerqi@gmail.com>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>

fs/ceph/addr.c

@@ -913,8 +913,9 @@ static int ceph_writepages_start(struct address_space *mapping,
 			if (page_offset(page) >= ceph_wbc.i_size) {
 				dout("%p page eof %llu\n",
 				     page, ceph_wbc.i_size);
-				if (ceph_wbc.size_stable ||
-				    page_offset(page) >= i_size_read(inode))
+				if ((ceph_wbc.size_stable ||
+				    page_offset(page) >= i_size_read(inode)) &&
+				    clear_page_dirty_for_io(page))
 					mapping->a_ops->invalidatepage(page,
 								0, PAGE_SIZE);
 				unlock_page(page);