If an RPC call is interrupted, assume that the server hasn't processed
the RPC call so that the next time we use the slot, we know that if we
get a NFS4ERR_SEQ_MISORDERED or NFS4ERR_SEQ_FALSE_RETRY, we just have
to bump the sequence number.
Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>

Shave a few bytes off the slot table size by moving the RPC timestamp
into the sequence results.
Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>

Look for sudden changes in the first and second derivatives in order
to eliminate outlier changes to target_highest_slotid (which are
due to out-of-order RPC replies).
Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>

Currently, we see a lot of bouncing for the value of highest_used_slotid
due to the fact that slots are getting freed, instead of getting instantly
transmitted to the next waiting task.
Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>

This means that we end up statically allocating 128 bytes for the
bitmap on each slot table.
For a server that supports 1MB write and read I/O sizes this means
that we can completely fill the maximum 1GB TCP send/receive
windows.
Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>

Clean up. Gather NFSv4.1 slot definitions in fs/nfs/nfs4session.h.
Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>

NFSv4.1 session management is getting complex enough to deserve
a separate file.
Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>