kern/131441: unionfs and/or nullfs not combineable

[Hannes Hauswedell]

>Number:         131441
>Category:       kern
>Synopsis:       unionfs and/or nullfs not combineable
>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 Feb 06 00:40:01 UTC 2009
>Closed-Date:
>Last-Modified:
>Originator:     Hannes Hauswedell
>Release:        7.1-Release
>Organization:
>Environment:
FreeBSD serv.lan.home 7.1-RELEASE FreeBSD 7.1-RELEASE #0: Thu Jan  1 14:37:25 UTC 2009     root at logan.cse.buffalo.edu:/usr/obj/usr/src/sys/GENERIC  i386
>Description:
Contrary to what mount_unionfs(8) reads [1] you cannot mount a unionfs over a tree that contains mounted nullfses further down. (Well you can, but those nullfses will dissappear).

This is the same with just using nullfses oder just unionfses.

I don't know if this is intentional or if it can be changed, but I thought I'd report it.

[1] "The union file system manipulates the namespace, rather than individual file systems. The union operation applies recursively down the directory tree now rooted at uniondir Thus any file systems which are mounted under uniondir will take part in the union operation."
>How-To-Repeat:
%cd /tmp/
%mkdir TEST1
%mkdir TEST1/SUB
%mount_nullfs /bin/ /tmp/TEST1/SUB/
%mkdir /tmp/TEST2
%ls /tmp/TEST1/SUB/
[          chmod      dd         ed         kenv       ls         pgrep      rcp        rmail      sleep      test
cat        cp         df         expr       kill       mkdir      pkill      realpath   rmdir      stty       unlink
chflags    csh        domainname getfacl    link       mv         ps         red        setfacl    sync       uuidgen
chio       date       echo       hostname   ln         pax        pwd        rm         sh         tcsh
%mount_unionfs /tmp/TEST2 /tmp/TEST1
%ls /tmp/TEST1/SUB/
%
>Fix:


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