http://bugs.gentoo.org/210392

--- lib/qpxtransport/qpx_transport.cpp
+++ lib/qpxtransport/qpx_transport.cpp
@@ -215,6 +215,21 @@
 #define KERNEL_BROKEN 0
 	if (use_sg_io)
 	{
+		/* see linux-2.6.23/block/scsi_ioctl.c:36 */
+		static const unsigned char scsi_command_size[8] =
+		{
+				6, 10, 10, 12,
+				16, 12, 10, 10
+		};
+		char cmdsize, opcode;
+
+		opcode = cgc.cmd[0];
+		/* see linux-2.6.23/include/scsi/scsi.h:25 */
+		cmdsize = scsi_command_size[((opcode) >> 5) & 7];
+		if ((sg_io.cmd_len > 0) && (sg_io.cmd_len < cmdsize)) {
+			sg_io.cmd_len = cmdsize;
+		}
+
 		sg_io.dxferp		= buf;
 		sg_io.dxfer_len		= sz;
 		sg_io.dxfer_direction	= use_sg_io[dir];