3w-9xxx: fix command completion race

The 3w-9xxx driver needs to tear down the dma mappings before returning
the command to the midlayer, as there is no guarantee the sglist and
count are valid after that point. Also remove the dma mapping helpers
which have another inherent race due to the request_id index.

Signed-off-by: Christoph Hellwig <[e-mail]>
Cc: [e-mail]
Acked-by: Adam Radford <[e-mail]>
Signed-off-by: James Bottomley <[e-mail]>

drivers/scsi/3w-9xxx.c

···
 static int twa_scsiop_execute_scsi(TW_Device_Extension *tw_dev, int request_id, char *cdb, int use_sg, TW_SG_Entry *sglistarg);
 static void twa_scsiop_execute_scsi_complete(TW_Device_Extension *tw_dev, int request_id);
 static char *twa_string_lookup(twa_message_type *table, unsigned int aen_code);
-static void twa_unmap_scsi_data(TW_Device_Extension *tw_dev, int request_id);
 
 /* Functions */
 
···
 				}
 
 				/* Now complete the io */
+				scsi_dma_unmap(cmd);
+				cmd->scsi_done(cmd);
 				tw_dev->state[request_id] = TW_S_COMPLETED;
 				twa_free_request_id(tw_dev, request_id);
 				tw_dev->posted_request_count--;
-				tw_dev->srb[request_id]->scsi_done(tw_dev->srb[request_id]);
-				twa_unmap_scsi_data(tw_dev, request_id);
 			}
 
 			/* Check for valid status after each drain */
···
 		}
 	}
 } /* End twa_load_sgl() */
-
-/* This function will perform a pci-dma mapping for a scatter gather list */
-static int twa_map_scsi_sg_data(TW_Device_Extension *tw_dev, int request_id)
-{
-	int use_sg;
-	struct scsi_cmnd *cmd = tw_dev->srb[request_id];
-
-	use_sg = scsi_dma_map(cmd);
-	if (!use_sg)
-		return 0;
-	else if (use_sg < 0) {
-		TW_PRINTK(tw_dev->host, TW_DRIVER, 0x1c, "Failed to map scatter gather list");
-		return 0;
-	}
-
-	cmd->SCp.phase = TW_PHASE_SGLIST;
-	cmd->SCp.have_data_in = use_sg;
-
-	return use_sg;
-} /* End twa_map_scsi_sg_data() */
 
 /* This function will poll for a response interrupt of a request */
 static int twa_poll_response(TW_Device_Extension *tw_dev, int request_id, int seconds)
···
 		    (tw_dev->state[i] != TW_S_INITIAL) &&
 		    (tw_dev->state[i] != TW_S_COMPLETED)) {
 			if (tw_dev->srb[i]) {
-				tw_dev->srb[i]->result = (DID_RESET << 16);
-				tw_dev->srb[i]->scsi_done(tw_dev->srb[i]);
-				twa_unmap_scsi_data(tw_dev, i);
+				struct scsi_cmnd *cmd = tw_dev->srb[i];
+
+				cmd->result = (DID_RESET << 16);
+				scsi_dma_unmap(cmd);
+				cmd->scsi_done(cmd);
 			}
 		}
 	}
···
 	/* Save the scsi command for use by the ISR */
 	tw_dev->srb[request_id] = SCpnt;
 
-	/* Initialize phase to zero */
-	SCpnt->SCp.phase = TW_PHASE_INITIAL;
-
 	retval = twa_scsiop_execute_scsi(tw_dev, request_id, NULL, 0, NULL);
 	switch (retval) {
 	case SCSI_MLQUEUE_HOST_BUSY:
+		scsi_dma_unmap(SCpnt);
 		twa_free_request_id(tw_dev, request_id);
-		twa_unmap_scsi_data(tw_dev, request_id);
 		break;
 	case 1:
+		SCpnt->result = (DID_ERROR << 16);
+		scsi_dma_unmap(SCpnt);
+		done(SCpnt);
 		tw_dev->state[request_id] = TW_S_COMPLETED;
 		twa_free_request_id(tw_dev, request_id);
-		twa_unmap_scsi_data(tw_dev, request_id);
-		SCpnt->result = (DID_ERROR << 16);
-		done(SCpnt);
 		retval = 0;
 	}
 out:
···
 				command_packet->sg_list[0].address = TW_CPU_TO_SGL(tw_dev->generic_buffer_phys[request_id]);
 				command_packet->sg_list[0].length = cpu_to_le32(TW_MIN_SGL_LENGTH);
 			} else {
-				sg_count = twa_map_scsi_sg_data(tw_dev, request_id);
-				if (sg_count == 0)
+				sg_count = scsi_dma_map(srb);
+				if (sg_count < 0)
 					goto out;
 
 				scsi_for_each_sg(srb, sg, sg_count, i) {
···
 		      (table[index].text != (char *)0)); index++);
 	return(table[index].text);
 } /* End twa_string_lookup() */
-
-/* This function will perform a pci-dma unmap */
-static void twa_unmap_scsi_data(TW_Device_Extension *tw_dev, int request_id)
-{
-	struct scsi_cmnd *cmd = tw_dev->srb[request_id];
-
-	if (cmd->SCp.phase == TW_PHASE_SGLIST)
-		scsi_dma_unmap(cmd);
-} /* End twa_unmap_scsi_data() */
 
 /* This function gets called when a disk is coming on-line */
 static int twa_slave_configure(struct scsi_device *sdev)

drivers/scsi/3w-9xxx.h

···
 #define TW_CURRENT_DRIVER_BUILD 0
 #define TW_CURRENT_DRIVER_BRANCH 0
 
-/* Phase defines */
-#define TW_PHASE_INITIAL 0
-#define TW_PHASE_SINGLE  1
-#define TW_PHASE_SGLIST  2
-
 /* Misc defines */
 #define TW_9550SX_DRAIN_COMPLETED	      0xFFFF
 #define TW_SECTOR_SIZE                        512