- in the cases where we skip over the i/o loop, increment npages by ridx
so that when the cleanup code starts processing the pgs array at index 0
it'll actually process all of the pages.
- process the PG_RELEASED flag when unbusying pages.
- add some missing MP locking.
- use MIN() and MAX() instead of min() and max() since the latter are
functions which take arguments of type "int" but we call them with
values of type "off_t", so the values could be truncated.
- in the PGO_PASTEOF case, use the larger of the current file size and the
end of the requested range of pages as the file size for this request.
this fixes some problems with sparsing writes to large offsets.
8c14e1d2db