kern/77026: umount-ing non-existent device panics system
mi at aldan.algebra.com
Wed Feb 2 10:10:22 PST 2005
>Synopsis: umount-ing non-existent device panics system
>Arrival-Date: Wed Feb 02 18:10:21 GMT 2005
>Originator: Mikhail Teterin
>Release: FreeBSD 5.3-STABLE i386
Virtual Estates, Inc.
Every once in a while, a user forgets to umount the file system
on a USB "flash-drive" before pulling the device out.
The umass-device duly disappears upont the pull-out, but the
mount-entry does not. Trying to umount such "fantom" devices
results in "device not configured" errors.
umount-ing with the `-f' switch crashes the system.
I doubt, this is a USB-specific problem -- it is just the
easiest way to reproduce the problem. CD-ROMs have hardware
protection against this, but disconnecting a hard
disk and rescanning the bus will, most probably, lead to the
Note, that this happens even when no writes await and no
files are open on the removed devices. `mount -oro -u',
for example, succeds.
Remember to umount. Still, panic is hardly a reasonable
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