commit cb5d04bc upstream.

With pgio refactoring in v3.15, .init_read and .init_write can be
called with valid pgio->pg_lseg. file layout was fixed at that time
by commit c6194271 (pnfs: filelayout: support non page aligned
layouts). But the generic helper still needs to be fixed.
Signed-off-by: Peng Tao <tao.peng@primarydata.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>