Time Stamping

All time stamps on files are stamped and propagated to other SFTs when the 
file is closed or committed (flushed). If a file is opened at time 1, 
written to at time 2, and closed at time 3, the last write time will be 
time 3. Subdirectories only have creation time stamps. 

The sfi_tstamp field of the file instance structure sffsi contains six 
flags :     

 Name            Value   Description
 ----------------------------------------------------------------
 ST_SCREAT       1       stamp creation time
 ----------------------------------------------------------------
 ST_PCREAT       2       propagate creation time
 ----------------------------------------------------------------
 ST_SWRITE       4       stamp last write time
 ----------------------------------------------------------------
 ST_PWRITE       8       propagate last write time
 ----------------------------------------------------------------
 ST_SREAD        16      stamp last read time
 ----------------------------------------------------------------
 ST_PREAD        32      propagate last read time

These flags are cleared when an SFT is created, and some of them may 
eventually be set by a file system worker routine. They are examined when 
the file is closed or flushed. 

For each time stamp, there are three meaningful actions:     

 ST_Sxxx    ST_Pxxx    Action
 --------------------------------------------------------------
 clear      clear      don't do anything
 --------------------------------------------------------------
 set        set        stamp and propagate (to other SFTs and
                       disk)
 --------------------------------------------------------------
 clear      set        don't stamp, but propagate existing
                       value