NFSD: Fix bad update of layout in nfsd4_return_file_layout

With return layout as, (seg is return layout, lo is record layout)
seg->offset <= lo->offset and layout_end(seg) < layout_end(lo),
nfsd should update lo's offset to seg's end,
and,
seg->offset > lo->offset and layout_end(seg) >= layout_end(lo),
nfsd should update lo's end to seg's offset.

Fixes: 9cf514ccfa ("nfsd: implement pNFS operations")
Signed-off-by: Kinglong Mee <[e-mail]>
Reviewed-by: Christoph Hellwig <[e-mail]>
Signed-off-by: J. Bruce Fields <[e-mail]>

fs/nfsd/nfs4layouts.c

···
 			list_move_tail(&lp->lo_perstate, reaplist);
 			return;
 		}
-		end = seg->offset;
+		lo->offset = layout_end(seg);
 	} else {
 		/* retain the whole layout segment on a split. */
 		if (layout_end(seg) < end) {
 			dprintk("%s: split not supported\n", __func__);
 			return;
 		}
-
-		lo->offset = layout_end(seg);
+		end = seg->offset;
 	}
 
 	layout_update_len(lo, end);