I think D28306 does not work because it sets the size
to va_size (n_vattr.na_size) and not n_size for the
write case.
This patch adds an "nsize" argument to ncl_pager_setsize()
so that the correct size can be passed in.
For the other calls, va_size/n_vattr.na_size is passed in,
so the semantics only changes for the write case added
by D28306.