kern/168298: VirtualBox using AIO on a zvol crashes

[Pete French]

>Number:         168298
>Category:       kern
>Synopsis:       VirtualBox using AIO on a zvol crashes
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    freebsd-bugs
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Thu May 24 10:50:03 UTC 2012
>Closed-Date:
>Last-Modified:
>Originator:     Pete French
>Release:        FreeBSD 8.3-STABLE amd64
>Organization:
Ingresso Group Ltd
>Environment:
System: FreeBSD dilbert.london-internal.ingresso.co.uk 8.3-STABLE FreeBSD 8.3-STABLE #0: Sun May 6 14:15:46 BST 2012 petefrench at dilbert.london-internal.ingresso.co.uk:/usr/obj/usr/src/sys/GENERIC amd64

	virtualbox-ose-kmod-4.1.14

>Description:

	With AIO loaded ViryialBox will use this to access files. Running
	VirtualBox on to of a zvol as the raw disc crashes. This may be a bug
	in zvol+aio, hence the classification above. VirtualBox prduces an
	error message in it's logs about AIO before crashing.

>How-To-Repeat:

	Running VirtualBox over a zvol with AIO and then doing heavy
	disc write activity will provoke the problem in a few minutes. I made
	a posting to stable regarding this here:

	http://lists.freebsd.org/pipermail/freebsd-stable/2012-May/067648.html

	The zvol has compression enabled.
>Fix:

	Do not load the AIO kernel module. VirtualBox is stable if AIO
	is not being used.


>Release-Note:
>Audit-Trail:
>Unformatted: