f2fs: flush journal nat entries for nat_bits during unmount

Let's flush journal nat entries for speed up in the next run.
Reviewed-by: NChao Yu <yuchao0@huawei.com>
Signed-off-by: NJaegeuk Kim <jaegeuk@kernel.org>

fs/f2fs/node.c

@@ -2582,6 +2582,13 @@ void f2fs_flush_nat_entries(struct f2fs_sb_info *sbi, struct cp_control *cpc)
 	nid_t set_idx = 0;
 	LIST_HEAD(sets);
 
+	/* during unmount, let's flush nat_bits before checking dirty_nat_cnt */
+	if (enabled_nat_bits(sbi, cpc)) {
+		down_write(&nm_i->nat_tree_lock);
+		remove_nats_in_journal(sbi);
+		up_write(&nm_i->nat_tree_lock);
+	}
+
 	if (!nm_i->dirty_nat_cnt)
 		return;