removing external usb hdd without unmounting causes reboot?

[Josh Paetzel]

On Thursday 19 July 2007, M. Warner Losh wrote:
> In message: <20070718170559.GA11915 at eos.sc1.parodius.com>
>
>             Jeremy Chadwick <koitsu at freebsd.org> writes:
> : If someone wants to work on this and needs devices/toys (thumb
> : drives, external enclosures + hard disks), let me know, I will be
> : more than happy to buy them the hardware needed.
>
> Willing to fund the work on it too?  This is a volunteer project,
> and you have to motivate people to work on this.  Tirades in
> mailing lists has proven to be ineffective in the past.
>
> I've looked at the issue, and generically, if a device goes away,
> it is *HARD* to not panic.  The same thing happens if you eject a
> CF card in a PC Card adapter in a PC Card slot.
>
> The best one can do without massive buffer cache work is what
> firewire does: it has one attachment to handle all umass devices. 
> When the device goes away, it pauses all operations to that device.
>  If the device comes back, it resumes the I/O .  If the device
> never comes back, then the I/O never finishes.
>
> Warner
>

Just curious, but what, if any, is the performance hit with this 
strategy?  I could care less about performance on a usb stick, but if 
we are talking about changes that are going to affect all filesystems 
regardless of storage device implimentation then I'm sort of 
interested.

eg: I wouldn't be happy trading filesystem performance for avoiding a 
panic that is trivial to avoid in the first place.

-- 
Thanks,

Josh Paetzel
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