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

Kostik Belousov kostikbel at gmail.com
Sun May 6 16:01:02 UTC 2007

[Cc: list trimmed to something reasonable]

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.
> there's an XXX in the linuxulator code saying:
> XXX Untested vs. mount -o union; probably does the wrong thing.
> 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 union
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.
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