ceph: redirty page before returning AOP_WRITEPAGE_ACTIVATE

The page has been marked clean before writepage is called.  If we don't
redirty it before postponing the write, it might never get written.

Cc: stable@vger.kernel.org
Fixes: 503d4fa6 ("ceph: remove reliance on bdi congestion")
Signed-off-by: NeilBrown <neilb@suse.de>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Reviewed-by: Xiubo Li <xiubli@redhat.org>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>

fs/ceph/addr.c

@@ -795,8 +795,10 @@ static int ceph_writepage(struct page *page, struct writeback_control *wbc)
 	ihold(inode);
 
 	if (wbc->sync_mode == WB_SYNC_NONE &&
-	    ceph_inode_to_fs_client(inode)->write_congested)
+	    ceph_inode_to_fs_client(inode)->write_congested) {
+		redirty_page_for_writepage(wbc, page);
 		return AOP_WRITEPAGE_ACTIVATE;
+	}
 
 	wait_on_page_fscache(page);