f2fs: support checkpoint error injection

This patch adds to support checkpoint error injection in f2fs for testing
fatal error tolerance, it will be useful that it can simulate abnormal
power off by f2fs itself instead of calling godown ioctl by running apps.

Signed-off-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
index fbcc172..fc886f0 100644
--- a/fs/f2fs/segment.c
+++ b/fs/f2fs/segment.c
@@ -345,6 +345,11 @@
  */
 void f2fs_balance_fs(struct f2fs_sb_info *sbi, bool need)
 {
+#ifdef CONFIG_F2FS_FAULT_INJECTION
+	if (time_to_inject(sbi, FAULT_CHECKPOINT))
+		f2fs_stop_checkpoint(sbi, false);
+#endif
+
 	if (!need)
 		return;