- Move the encoding/decoding of the actual COMPOUND XDR header out of
   encode_compound()/decode_compound().

 - Make each NFSv4 operation 'decode_' routine also take care of
   decoding its own header, and checking it for correctness.
   Also allows us to get rid of the 'nfserr' parameter...

This fixes a couple of incorrect XDR buffer reservations.  The values
passed to RESERVE_SPACE() must reflect precisely the number of bytes
that we wish to send down the wire.

Here is the a pre-patch in the attempt to get rid of 'struct
nfs4_compound', and the associated horrible union in 'struct
nfs4_op'.

It splits out the fields that are meant to do buffer overflow checking
and iovec adjusting on the XDR received/sent data. It moves support
for that nto the dedicated structure 'xdr_stream', and the associated
functions 'xdr_reserve_space()', 'xdr_inline_decode()'.

The patch also expands out the all macros ENCODE_HEAD, ENCODE_TAIL,
ADJUST_ARGS and DECODE_HEAD, as well as most of the DECODE_TAILs.

Given Andi Kleen's patch that introduces of VFS-level support for
nanosecond time resolutions, we should finally be able to export the
existing NFS client level support to userland.

In order to do so, the following patch will convert all NFS private 'raw
u64' values into the kernel-supported struct timespec directly in the
xdr_encode/xdr_decode routines.

It adds support for the nanosecond field in NFS 'setattr' calls, and in
nfs_refresh_inode().

Finally, there are a few cleanups in the nfs_refresh_inode code that
convert multiple use of the NFS_*(inode) macros into a single
dereference of NFS_I(inode).

stat64 has been changed to return jiffies granuality as nsec in previously
unused fields. This allows make to make better decisions on when
to recompile a file. Follows losely the Solaris API.

CURRENT_TIME has been redefined to return struct timespec.  The users
who don't use it in a inode/attr context have been changed to use a new
get_seconds() function.  CURRENT_TIME is implemented by an out-of-line
function.

There is a small performance penalty in this patch.  The previous
filemap code had an optimization to flush atime only once a second.
This is currently gone, which will increase flushes a bit.  I believe
the correct solution if it should be a problem is to have per super
block fields that give an arbitary atime flush granuality - so that you
can set it to be only flushed once a hour if you prefer that.  I will
work on that later in separate patches if the need should arise.

struct inode and the attr struct has been changed to store struct
timespec instead of time_t for [cma]time.  Not all file systems support
this granuality, but some like XFS,NFSv3,CIFS,JFS do.  The others will
currently truncate the nsec part on flushing to disk.  There was some
discussion on this rounding on l-k previously.  I went for simple
truncation because there is not much evidence IMHO that the more
complicated roundings have any advantages.  In practice application will
be rather unlikely to notice the rounding anyways - they can only see a
difference when an inode is flush from memory and reloaded in less than
a second, which is rather unlikely.

The "procedure number" has been used for 2 purposes in the kernel
client RPC implementation:

  1) As a number to pass to the server in the RPC header.

  2) As an index into the "procedure array" of type 'struct
     rpc_procinfo', from which the RPC layer can find the XDR
     encode/decode functions, buffer size, and all the other static
     data that it needs to construct the on-wire RPC message.

This works fine for NFSv2, v3 and for the NLM locking code for which
there is a one-to-one mapping between NFS file operations, and RPC
procedures.
For NFSv4 on the other hand, the mapping is many-to-one, since there
is only one RPC procedure number: NFSPROC4_COMPOUND.

For efficiency purposes, we want to have a one-to-one mapping between
NFS file operations and the corresponding XDR encode/decode routines,
but currently this is not possible because of (2). The result is the
mess that is 'struct nfs4_op' and encode/decode_compound.

In the process eliminating (2), we might as well change to passing a
pointer to the appropriate procedure array entry instead of an
index. This change can be made transparent

The appended patch therefore does the following:

   - Substitute a pointer to the rpc_procinfo instead of the RPC
     procedure number in the struct rpc_message.
   - Make the RPC procedure number an entry in the struct
     rpc_procinfo.
   - Clean out the largely unused (except in some obscure lockd
     debugging code) p_name field. The latter was just a stringified
     version of the RPC procedure name, so for those lockd cases, we
     can use the RPC procedure number instead.

Thanks again to davem...

Now that all the hooks are in place, this large patch imports all
of the new code for the NFSv4 client.
  nfs4proc.c   - procedure vectors
  nfs4xdr.c    - XDR
  nfs4state.c  - state bookkeeping (very minimal for now)
  nfs4renewd.c - a daemon (implemented as an rpc_task) to keep
                 state from expiring on the server

Note: The RPCSEC_GSS authentication code is not yet included here.
  For the moment we make do with AUTH_UNIX aka. AUTH_SYS.

  Neither is the code to do upcalls to userland in order to do
  uid/gid <-> name mappings. Instead, stubs have been added to
  translate everything to 'nobody:nobody' == '-2:-2'