Date: Sun, 22 Jul 2007 23:23:41 +1000 From: Norberto Meijome <freebsd@meijome.net> To: "M. Warner Losh" <imp@bsdimp.com> Cc: LoN_Kamikaze@gmx.de, olli@lurza.secnetix.de, freebsd-stable@freebsd.org, idiotbg@gmail.com, josh@tcbug.org Subject: Re: removing external usb hdd without unmounting causes reboot? Message-ID: <20070722232341.0bdfd6da@localhost> In-Reply-To: <20070721.204413.-432837168.imp@bsdimp.com> References: <200707190943.55428.idiotbg@gmail.com> <20070719.090250.1387160138.imp@bsdimp.com> <20070721110603.3878d933@localhost> <20070721.204413.-432837168.imp@bsdimp.com>
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On Sat, 21 Jul 2007 20:44:13 -0600 (MDT)
"M. Warner Losh" <imp@bsdimp.com> wrote:
> In message: <20070721110603.3878d933@localhost>
> Norberto Meijome <freebsd@meijome.net> writes:
> : On Thu, 19 Jul 2007 09:02:50 -0600 (MDT)
> : "M. Warner Losh" <imp@bsdimp.com> wrote:
> :
> : > In message: <200707190943.55428.idiotbg@gmail.com>
> : > Momchil Ivanov <idiotbg@gmail.com> writes:
> : > : What is then the reason for the kernel not being able to unmount a
> : > : filesystem whose provider is no longer present?
> : >
> : > The problem is that the device driver has wound down, deallocated
> : > memory, etc. Now the kernel comes along with stale references to the
> : > device and panic ensues. It is really just that simple. There's no
> : > replacement of the now-dead device with dead calls.
> : >
> : > And even if you fixed that, most of the file systems in the tree today
> : > do not tolerate errors on writes at all and that also leads to
> : > panics. This is why firewire freezes the I/Os rather than failing
> : > them (and why umount -f on a firewire drive hangs).
> :
> : Please point me to the correct RTFM, because I feel this worth it :)
>
> src/sys/fs/..., src/sys/kern/... and src/sys/vm/... are your best bets.
>
> : Is there a reason why the kernel cannot check 'upwards' if a device
> : is being used, ie mounted ? and prevent the unloading of the device
> : driver ?
>
> Check, sure, it can check. But what does a simple check accomplish if
> the filesystem panics if the underlying media returns an error? The
> problem isn't as simple as just looking in one place or another, but
> rather systemic in nature.
>
thanks Warner. What do you estimate is the cost (time, at least) to investigate
and fix this issue? SoC project? 4 mth project?
cheers,
B
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