If the times differ, the local file system cache is invalidated and {TAIL ~ the modification time} is then read from {HEAD ~ the storage device} and again compared 
If the times differ , the local file system cache is invalidated and { TAIL ~ the modification time } is then read from { HEAD ~ the storage device } and again compared
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH