NFSv4.1: filelayout driver specific code for COMMIT

Implement all the hooks created in the previous patches.
This requires exporting quite a few functions and adding a few
structure fields.

Signed-off-by: Fred Isaman <iisaman@netapp.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

diff --cc fs/nfs/inode.c
Simple merge

diff --cc fs/nfs/internal.h
Simple merge

diff --cc fs/nfs/nfs4filelayout.c
Simple merge

diff --cc fs/nfs/pnfs.c
Simple merge

diff --cc fs/nfs/write.c
Simple merge

diff --cc include/linux/nfs_fs.h
Simple merge

diff --cc include/linux/nfs_xdr.h
Simple merge