Linux Storage and Filesystem workshop, day 1

For example mainline already has file systems where some of the stat()
information is never correct:
* Number of used blocks is correct only on block based file systems (i.e.
not in JFFS2, UBIFS etc)
* File size doesn't correspond to how much space the file takes from the
file system if file system uses compression
* Time information depends on mount options
* Is st_dev correct for union mounts of union file systems?

I think nowadays applications should consider stat() mostly as a "best
guess"...