Problem (potential bug) in the vnode disk driver, stable branch

Momtchil Momtchev momtchil.momtchev at
Thu Mar 25 10:18:42 PST 2004


	We've stumbled on what appears to be a bug in the vnode disk driver. It 
happens rarely and we aren't able to reproduce it atm, but we've seen it 
already a few times on different kernels, compiled with different options.
	If you can read russian, there's also a brief description of what appears to 
be exactly the same problem at Theirs is on 
FreeBSD 4.3, we are running FreeBSD 4.9.

	What happens is that after mounting a file as a filesystem through the vn 
driver, everything will run fine, then eventually (after a few days, weeks or 
even months) the filesystem is going to get "disconnected" in a strange way 
with every attempt to access it returning an I/O error.

	vnconfig will report "device not configured":

#/usr/sbin/vnconfig -c /dev/vn0c /somefile
vnconfig: /dev/vn0c: Device not configured
#vnconfig -u /dev/vn0c
vnconfig: /dev/vn0c: Device not configured

	umount/mount will fail too.

	We are still trying to find a way to reliably reproduce the problem in order 
to fill a standard bug report.
	ATM we don't have any idea what could trigger it.
	The main problem is that it happens very rarely and we can't really afford to 
run a kernel with all the debugging enabled on thousands of hosts (to catch 
the few which will crash).

	Anyone seen this before? Any comments will be appreciated.

Momtchil Momtchev, R&D Engineer <momtchil.momtchev at>

Netasq - Secure Internet Connectivity
Tél : +33 320 619 630
Fax : +33 320 619 639

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