[Unionfs] unionfs with mmap support breaks apt-get

[Shaya Potter]

On Wed, 2006-03-22 at 18:02 -0500, Shaya Potter wrote:
> On Wed, 2006-03-22 at 23:37 +0100, Michael Prokop wrote:
> > Hello,
> > 
> > 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.  I'm unsure I have time to
> look into it right now, as I have a bunch of deadlines near (thesis
> proposal, osdi * 2) and with passover coming, a bit overwhelmed for the
> near future.

oh, an interesting thing about apt-get is that it seems to be the only
program I know of that seems to write files via mmap. (i.e.
SHARED/WRITE), and therefore will not work on file system's that don't
support shared write mappings (i.e. gfs/ocfs2 at least).