f2fs: fix to wait all node page writeback

There is a race condition that we may miss to wait for all node pages
writeback, fix it.

- fsync()				- shrink
 - f2fs_do_sync_file
					 - __write_node_page
					  - set_page_writeback(page#0)
					  : remove DIRTY/TOWRITE flag
  - f2fs_fsync_node_pages
  : won't find page #0 as TOWRITE flag was removeD
  - f2fs_wait_on_node_pages_writeback
  : wont' wait page #0 writeback as it was not in fsync_node_list list.
					   - f2fs_add_fsync_node_entry

Fixes: 50fa53ec ("f2fs: fix to avoid broken of dnode block list")
Signed-off-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

fs/f2fs/node.c

@@ -1562,15 +1562,16 @@ static int __write_node_page(struct page *page, bool atomic, bool *submitted,
 	if (atomic && !test_opt(sbi, NOBARRIER))
 		fio.op_flags |= REQ_PREFLUSH | REQ_FUA;
 
-	set_page_writeback(page);
-	ClearPageError(page);
-
+	/* should add to global list before clearing PAGECACHE status */
 	if (f2fs_in_warm_node_list(sbi, page)) {
 		seq = f2fs_add_fsync_node_entry(sbi, page);
 		if (seq_id)
 			*seq_id = seq;
 	}
 
+	set_page_writeback(page);
+	ClearPageError(page);
+
 	fio.old_blkaddr = ni.blk_addr;
 	f2fs_do_write_node_page(nid, &fio);
 	set_node_addr(sbi, &ni, fio.new_blkaddr, is_fsync_dnode(page));