scsi: core: add scsi_host_(block,unblock) helper function

Add helper functions to call scsi_internal_device_block()/
scsi_internal_device_unblock() for all attached devices on a SCSI host.

Link: https://lore.kernel.org/r/20200228075318.91255-9-hare@suse.deReviewed-by: NChristoph Hellwig <hch@lst.de>
Reviewed-by: NBart Van Assche <bvanassche@acm.org>
Signed-off-by: NHannes Reinecke <hare@suse.de>
Signed-off-by: NMartin K. Petersen <martin.petersen@oracle.com>

drivers/scsi/scsi_lib.c

@@ -2845,6 +2845,36 @@ scsi_target_unblock(struct device *dev, enum scsi_device_state new_state)
 }
 EXPORT_SYMBOL_GPL(scsi_target_unblock);
 
+int
+scsi_host_block(struct Scsi_Host *shost)
+{
+	struct scsi_device *sdev;
+	int ret = 0;
+
+	shost_for_each_device(sdev, shost) {
+		ret = scsi_internal_device_block(sdev);
+		if (ret)
+			break;
+	}
+	return ret;
+}
+EXPORT_SYMBOL_GPL(scsi_host_block);
+
+int
+scsi_host_unblock(struct Scsi_Host *shost, int new_state)
+{
+	struct scsi_device *sdev;
+	int ret = 0;
+
+	shost_for_each_device(sdev, shost) {
+		ret = scsi_internal_device_unblock(sdev, new_state);
+		if (ret)
+			break;
+	}
+	return ret;
+}
+EXPORT_SYMBOL_GPL(scsi_host_unblock);
+
 /**
  * scsi_kmap_atomic_sg - find and atomically map an sg-elemnt
  * @sgl:	scatter-gather list

include/scsi/scsi_host.h

@@ -758,6 +758,8 @@ static inline int scsi_host_scan_allowed(struct Scsi_Host *shost)
 
 extern void scsi_unblock_requests(struct Scsi_Host *);
 extern void scsi_block_requests(struct Scsi_Host *);
+extern int scsi_host_block(struct Scsi_Host *shost);
+extern int scsi_host_unblock(struct Scsi_Host *shost, int new_state);
 
 struct class_container;