[Unionfs] unionfs with mmap support breaks apt-get

[Shaya Potter]

On Thu, 2006-03-23 at 09:55 -0500, Shaya Potter wrote:
> On Thu, 2006-03-23 at 10:20 +0100, Michael Prokop wrote:
> > * Shaya Potter <spotter at cs.columbia.edu> [20060323 00:10]:
> > > On Wed, 2006-03-22 at 23:37 +0100, Michael Prokop wrote:
> > 
> > > > starting with mmap support in unionfs the current cvs snapshots
> > > > cause problems with apt-get on Debian running kernel 2.6.16.
> > 
> > > > Running 'apt-get update; apt-get upgrade' results in:
> > 
> > > > [...]
> > > > E: I wasn't able to locate file for the $FOO package. This might
> > > > mean you need to manually fix this package.
> > 
> > > > I had no time to take a closer look at apt's sources, but it
> > > > definitely uses mmap. So far I just tracked down that it's related
> > > > to the mmap support within unionfs:
> > 
> > > really? I use it w/ apt-get all the time.
> > [...]
> > 
> > Yes. I'm running dpkg version 1.13.17, apt version 0.6.43.3 using an
> > up2date Debian unstable system with kernel 2.6.16 and unionfs with
> > the "Knoppix-like layout" in Live-CD mode.
> 
> ok, I've reproduced this problem w/ plain unionfs-1.1.3 (seems I have
> been using it by accident, instead of my patched for mmap stuff).

just reran it w/ my mmap code (i.e my patched code, not the way it got
integrated) and apt-get seems to work fine.

blade12:/osdi06/fs# ls base
bin   dev  home    lib         media  opt   proc  sbin   srv  tmp  var
boot  etc  initrd  lost+found  mnt    post  root  shaya  sys  usr
blade12:/osdi06/fs# ls 1
blade12:/osdi06/fs# mount -t unionfs -o dirs=1=rw:base=ro none union/
blade12:/osdi06/fs# cd union/
blade12:/osdi06/fs/union# ls
bin   dev  home    lib         media  opt   proc  sbin   srv  tmp  var
boot  etc  initrd  lost+found  mnt    post  root  shaya  sys  usr
blade12:/osdi06/fs/union# apt-get install foo2zjs
Reading Package Lists... Done
Building Dependency Tree... Done
Recommended packages:
  foomatic-db-engine
The following NEW packages will be installed:
  foo2zjs
0 upgraded, 1 newly installed, 0 to remove and 460 not upgraded.
Need to get 741kB of archives.
After unpacking 2478kB of additional disk space will be used.
Get:1 http://mirror.cc.columbia.edu testing/main foo2zjs 20060124dfsg-1
[741kB]
Fetched 741kB in 0s (3704kB/s)

Selecting previously deselected package foo2zjs.
(Reading database ...

74972 files and directories currently installed.)
Unpacking foo2zjs (from .../foo2zjs_20060124dfsg-1_i386.deb) ...
Setting up foo2zjs (20060124dfsg-1) ...

blade12:/osdi06/fs/union#
blade12:/osdi06/fs/union# cd ..
blade12:/osdi06/fs# ls base/
bin   dev  home    lib         media  opt   proc  sbin   srv  tmp  var
boot  etc  initrd  lost+found  mnt    post  root  shaya  sys  usr
blade12:/osdi06/fs# ls 1
root  tmp  var