[SCSI] host state model update: mediate host add/remove race

Add support to not allow additions to a host when it is being removed.
Signed-off-by: Mike Anderson <andmike@us.ibm.com>
Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>

drivers/scsi/hosts.c

@@ -133,7 +133,9 @@ EXPORT_SYMBOL(scsi_host_set_state);
  **/
 void scsi_remove_host(struct Scsi_Host *shost)
 {
+	down(&shost->scan_mutex);
 	scsi_host_set_state(shost, SHOST_CANCEL);
+	up(&shost->scan_mutex);
 	scsi_forget_host(shost);
 	scsi_proc_host_rm(shost);
 

drivers/scsi/scsi_scan.c

@@ -1251,9 +1251,12 @@ struct scsi_device *__scsi_add_device(struct Scsi_Host *shost, uint channel,
 
 	get_device(&starget->dev);
 	down(&shost->scan_mutex);
-	res = scsi_probe_and_add_lun(starget, lun, NULL, &sdev, 1, hostdata);
+	if (scsi_host_scan_allowed(shost)) {
+		res = scsi_probe_and_add_lun(starget, lun, NULL, &sdev, 1,
+					     hostdata);
 		if (res != SCSI_SCAN_LUN_PRESENT)
 			sdev = ERR_PTR(-ENODEV);
+	}
 	up(&shost->scan_mutex);
 	scsi_target_reap(starget);
 	put_device(&starget->dev);
@@ -1403,11 +1406,15 @@ int scsi_scan_host_selected(struct Scsi_Host *shost, unsigned int channel,
 		return -EINVAL;
 
 	down(&shost->scan_mutex);
+	if (scsi_host_scan_allowed(shost)) {
 		if (channel == SCAN_WILD_CARD)
-		for (channel = 0; channel <= shost->max_channel; channel++)
-			scsi_scan_channel(shost, channel, id, lun, rescan);
+			for (channel = 0; channel <= shost->max_channel;
+			     channel++)
+				scsi_scan_channel(shost, channel, id, lun,
+						  rescan);
 		else
 			scsi_scan_channel(shost, channel, id, lun, rescan);
+	}
 	up(&shost->scan_mutex);
 
 	return 0;

include/scsi/scsi_host.h

@@ -650,6 +650,15 @@ static inline struct device *scsi_get_device(struct Scsi_Host *shost)
         return shost->shost_gendev.parent;
 }
 
+/**
+ * scsi_host_scan_allowed - Is scanning of this host allowed
+ * @shost:	Pointer to Scsi_Host.
+ **/
+static inline int scsi_host_scan_allowed(struct Scsi_Host *shost)
+{
+	return shost->shost_state == SHOST_RUNNING;
+}
+
 extern void scsi_unblock_requests(struct Scsi_Host *);
 extern void scsi_block_requests(struct Scsi_Host *);