The NFSv4 server currently supports read delegation using VFS lease
which is implemented using file_lock.
This patch series add write delegation support for NFSv4 server by:
. remove the check for F_WRLCK in generic_add_lease to allow
file_lock to be used for write delegation.
. grant write delegation for OPEN with NFS4_SHARE_ACCESS_WRITE
if there is no conflict with other OPENs.
. add XDR support for sending and receiving CB_GETATTR.
. handle GETATTR from another client on a file that has outstanding
write delegation by using CB_GETATTR to get the latest change_info
and size for the GETATTR reply.
Write delegation conflict with another OPEN, REMOVE, RENAME and SETATTR
are handled the same as read delegation using notify_change, try_break_deleg.
