[SCSI] libfc: Fix wrong scsi return status under FC_DATA_UNDRUN

This bug is exposed when there is a link flap in LLD. Particularly, when it
happens right after a SCSI write command is sent out, no FCP_DATA is sent,
causing fsp->status_code to be set as FC_DATA_UNDRUN in fc_fcp_complete_locked
even no SCSI status is received. Consequently, fc_io_compl treats this as DID_OK.
This results in SCSI returning successful to the initial I/O request even
there is no DATA actually sent. Particularly, if you run an I/O tool w/ data
verification on, the read back for verification is gonna fail.

This is fixed here by checking when FC_DATA_UNDRUN happens, SCSI status is
received w/ FC_SRB_RCV_STATUS set in fsp->state.

Signed-off-by: Yi Zou <yi.zou@intel.com>
Signed-off-by: Robert Love <robert.w.love@intel.com>
Signed-off-by: James Bottomley <James.Bottomley@suse.de>

drivers/scsi/libfc/fc_fcp.c

@@ -1849,7 +1849,8 @@ static void fc_io_compl(struct fc_fcp_pkt *fsp)
 			 * scsi status is good but transport level
 			 * underrun.
 			 */
-			sc_cmd->result = DID_OK << 16;
+			sc_cmd->result = (fsp->state & FC_SRB_RCV_STATUS ?
+					  DID_OK : DID_ERROR) << 16;
 		} else {
 			/*
 			 * scsi got underrun, this is an error