kern/177658: FreeBSD panics after get full filesystem with ufs snapshot

[José García Juanino]

>Number:         177658
>Category:       kern
>Synopsis:       FreeBSD panics after get full filesystem with ufs snapshot
>Confidential:   no
>Severity:       non-critical
>Priority:       low
>Responsible:    freebsd-bugs
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Fri Apr 05 17:10:00 UTC 2013
>Closed-Date:
>Last-Modified:
>Originator:     José García Juanino
>Release:        FreeBSD 9.1 RELEASE
>Organization:
>Environment:
FreeBSD golem.boecillo.eemea.ericsson.se 9.1-RELEASE FreeBSD 9.1-RELEASE #0 r243825: Tue Dec  4 09:23:10 UTC 2012     root at farrell.cse.buffalo.edu:/usr/obj/usr/src/sys/GENERIC  amd64

>Description:
Reproducible panic: FreeBSD panics after get full filesystem with a ufs snapshot.

kernel and userland is standard, with no tweaks, only in /boot/loader.conf:

geom_concat_load="YES"

(the affected filesystem is gconcated of several partitions).

In sysctl.conf, I have:

kern.ipc.somaxconn=256
kern.maxfiles=25000


>How-To-Repeat:
In a ufs filesystem with soft updates and some snapshot taken previously, do some heavy write activity. The snapshot will grow a lot; if that snapshot fill up the filesystem you will get a panic. Full backtrace in http://pastebin.com/MZP2Femp.

This PR is pretty similar to kern/162362.


>Fix:


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