[ANN] unionfs patchset-19-20070504 release, it is now MPSAFE and transparent mode as default

Danny Braniss danny at cs.huji.ac.il
Mon May 7 07:01:11 UTC 2007

> On Sun, May 06, 2007 at 11:30:34AM +0200, Roman Divacky wrote:
> > > Hi,
> > > 	So far I've tested it under -current, in my diskless env. where
> > > /etc & /compat/linux are unionfs'ed with a mfs, and so all seems OK.
> >=20
> > there's an XXX in the linuxulator code saying:
> >=20
> > XXX Untested vs. mount -o union; probably does the wrong thing.
> >=20
> > can you confirm that it works ok with unionfs from daichi?
> There are to quite different union-kind things in kernel. One is the -o uni=
> on
> option for the mount, see mount(2). Second is unionfs proper.
> The first thing (-o union) requires support in namei and related syscalls,
> like getdirentries. It is implemented for native freebsd getdirentries (both
> current and 4-compat variants), but, AFAIR, is _not_ implemented in
> compat syscalls implementations for sysv, linux, xenix etc. And, in fact,
> making that compat syscalls behave is somewhat tricky due to cookies and
> differences between supposed output formats for ABIs.
> Unionfs shall have no real difference in behaviour what used from processes
> using compat ABIs.

well, it seems that there is a problem:
I have /compat/linux union mounted with a memory fs - because / is diskless, 
and linux likes to write
to etc, var), so far, so good, but
	mount -t linprocfs linproc /compat/linux/proc
mountd[874]: can't delete exports for /home/dist/local/amd64=FreeBSD_7.0/compat
/linux/proc: Invalid argument unionfs does not support mount update

though I don't think the problem is in the unionfs code ...


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