iscsi client hangs performing I/O on a dead target

[Graham Todd]

Hi,

I believe the FreeBSD foundation is supporting development that may help
with this (the "Safe Removal of Active Disk Devices" project)? The focus
is on USB devices since, as noted in the newsletter, "[t]he removable USB
disk causing a crash turns out to be our #1 reported bug." :-)

Hopefully the work can be useful in a generic way since panics induced by
disappearing USB devices are easier to control than those caused by
disappearing network storage.

cheers,

From: http://www.freebsdfoundation.org/press/2008Dec-newsletter.shtm

... [snip] ...
The first project to get off the ground is to make FreeBSD tolerate the
removal of active disk devices, such as when a USB flash device with a
mounted filesystems is physically detached by a user. Currently the system
may panic in this situation. The work involves adding proper reference
counting to strategic portions of the kernel and modifying filesystems to
properly handle "device lost" errors.

Edward Tomasz Napierala is the developer working on this project.

...