Hello!
This is reworked Mark Fasheh's patch + my earlier patch.
It allows one to specify which specific struct stat fields are needed
out of the fstatat call, and also a request to obtain most uptodate
information for inode (for NFS mostly).
Also it adds AT_STAT_SELF flag to mean that the stat should be executed not
on a path, but on the passed filedecriptor itself.
A first real kernel user for this added in loop block driver that does
not care about size or anything else besides rdev and inode number.
I see various architectures replicate bits of vfs_*stat* in some compat
code, I am not sure if we need to update those as well or not.
This patch does away with all the extra syscalls.