blktrace: perform cleanup after setup error

Currently even if BLKTRACESETUP ioctl has failed user must call
BLKTRACETEARDOWN to be shure what all staff was cleaned, which
is contr-intuitive.
Let's setup ioctl make necessery cleanup by it self.
Signed-off-by: NDmitry Monakhov <dmonakhov@openvz.org>
Signed-off-by: NJens Axboe <jens.axboe@oracle.com>

kernel/trace/blktrace.c

@@ -540,9 +540,10 @@ int blk_trace_setup(struct request_queue *q, char *name, dev_t dev,
 	if (ret)
 		return ret;
 
-	if (copy_to_user(arg, &buts, sizeof(buts)))
+	if (copy_to_user(arg, &buts, sizeof(buts))) {
+		blk_trace_remove(q);
 		return -EFAULT;
-
+	}
 	return 0;
 }
 EXPORT_SYMBOL_GPL(blk_trace_setup);