[SCSI] SCSI sd: fix module init/exit error handling

- Properly handle and unwind errors in init_sd(). Fixes leaks on error,
if class_register() or scsi_register_driver() failed.

- Ensure that exit_sd() execution order is the perfect inverse of
initialization order.

FIXME: If some-but-not-all register_blkdev() calls fail, we wind up
calling unregister_blkdev() for block devices we did not register.
This was a pre-existing bug.

Signed-off-by: Jeff Garzik <[e-mail]>
Signed-off-by: James Bottomley <[e-mail]>

drivers/scsi/sd.c

···
  **/
 static int __init init_sd(void)
 {
-	int majors = 0, i;
+	int majors = 0, i, err;
 
 	SCSI_LOG_HLQUEUE(3, printk("init_sd: sd driver entry point\n"));
 
···
 	if (!majors)
 		return -ENODEV;
 
-	class_register(&sd_disk_class);
+	err = class_register(&sd_disk_class);
+	if (err)
+		goto err_out;
 
-	return scsi_register_driver(&sd_template.gendrv);
+	err = scsi_register_driver(&sd_template.gendrv);
+	if (err)
+		goto err_out_class;
+
+	return 0;
+
+err_out_class:
+	class_unregister(&sd_disk_class);
+err_out:
+	for (i = 0; i < SD_MAJORS; i++)
+		unregister_blkdev(sd_major(i), "sd");
+	return err;
 }
 
 /**
···
 	SCSI_LOG_HLQUEUE(3, printk("exit_sd: exiting sd driver\n"));
 
 	scsi_unregister_driver(&sd_template.gendrv);
+	class_unregister(&sd_disk_class);
+
 	for (i = 0; i < SD_MAJORS; i++)
 		unregister_blkdev(sd_major(i), "sd");
-
-	class_unregister(&sd_disk_class);
 }
 
 module_init(init_sd);