[PATCH 02/18] xstat: Add a pair of system calls to make extended file stats available [ver #6]

[Jim Rees]

Linus Torvalds wrote:

  I personally think that Unix ctime is insane. There is no real reason
  why "write()" should change mtime, but "chmod" changes ctime. It was
  just a random decision way back when...

I believe it was done that way so "dump" could backup just the inode and not
the data if only the inode had changed.  Full history here:

http://blog.plover.com/Unix/ctime.html