[SCSI] libfc: fixed a read IO data integrity issue when a IO data frame lost

The fc_fcp_complete_locked detected data underrun in this case and set
the FC_DATA_UNDRUN but that was ignored by fc_io_compl for all cases
including read underrun.

Added code to not to ignore FC_DATA_UNDRUN for read IO and instead
suggested scsi-ml to retry cmd to  recover from lost data frame.

Not sure if it is okay to ignore FC_DATA_UNDRUN for other case, so let
code as is for other cases but removed or-ing with zero valued fsp->cdb_status
for those cases.
Signed-off-by: Vasu Dev <vasu.dev@intel.com>
Signed-off-by: Robert Love <robert.w.love@intel.com>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>

drivers/scsi/libfc/fc_fcp.c

@@ -1810,12 +1810,12 @@ static void fc_io_compl(struct fc_fcp_pkt *fsp)
 		sc_cmd->result = DID_ERROR << 16;
 		break;
 	case FC_DATA_UNDRUN:
-		if (fsp->cdb_status == 0) {
+		if ((fsp->cdb_status == 0) && !(fsp->req_flags & FC_SRB_READ)) {
 			/*
 			 * scsi status is good but transport level
-			 * underrun. for read it should be an error??
+			 * underrun.
 			 */
-			sc_cmd->result = (DID_OK << 16) | fsp->cdb_status;
+			sc_cmd->result = DID_OK << 16;
 		} else {
 			/*
 			 * scsi got underrun, this is an error