U64 Ordering in File System Code of Btrfs

[nick]

Hey Guys,
Thanks for the help so far. I am wondering after reading the btrfs code for certain functions there seem to 
be a lot of u64 variable and function returns of this type. Is this common in file system due to the disk
being in a certain format and depending on the CPU being big or small endian that this needed to not reorder
the disk parts that are being read into main memory and preserve the data's ordering?
Cheers Nick