Add roll-forward recovery process for encrypted dentry, so the first fsync
issued to an encrypted file does not need writing checkpoint.

This improves the performance of the following test at thousands of small
files: open -> write -> fsync -> close
Signed-off-by: NShuoran Liu <liushuoran@huawei.com>
Acked-by: NChao Yu <yuchao0@huawei.com>
[Jaegeuk Kim: modify kernel message to show encrypted names]
Signed-off-by: NJaegeuk Kim <jaegeuk@kernel.org>