f2fs: no more dirty_nat_entires when flushing

After flushing dirty nat entries, it has to be no more dirty nat
entries.

Signed-off-by: Changman Lee <cm224.lee@samsung.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

fs/f2fs/node.c

@@ -1925,10 +1925,10 @@ static void __flush_nat_entry_set(struct f2fs_sb_info *sbi,
 	else
 		f2fs_put_page(page, 1);
 
-	if (!set->entry_cnt) {
-		radix_tree_delete(&NM_I(sbi)->nat_set_root, set->set);
-		kmem_cache_free(nat_entry_set_slab, set);
-	}
+	f2fs_bug_on(sbi, set->entry_cnt);
+
+	radix_tree_delete(&NM_I(sbi)->nat_set_root, set->set);
+	kmem_cache_free(nat_entry_set_slab, set);
 }
 
 /*