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shutdown). There are still problems with device access and a PR will be filed. - Kill checkalias(). Allow multiple vnodes to reference a single device. - Don't play dangerous tricks with block vnodes to ensure that only one vnode can describe a block device. Instead, prohibit concurrent opens of block devices. As a bonus remove the unreliable code that prevents multiple file system mounts on the same device. It's no longer needed. - Track opens by vnode and by device. Issue cdev_close() when the last open goes away, instead of abusing vnode::v_usecount to tell if the device is open.