panic when mounting device >= 2 times

[Alexander Best]

Andriy Gapon schrieb am 2009-10-14:
> on 14/10/2009 14:21 Alexander Best said the following:
> > could somebody have a look at this PR please:
> > http://www.freebsd.org/cgi/query-pr.cgi?pr=kern/108968

> > this still exists in -CURRENT.

> This is because of serious and long-standing brokenness (probably
> from time of
> introduction of GEOM) in g_vfs_open/g_vfs_close.
> The essence:
> 1. we allow multiple concurrent read-only mounts of a device
> 2. but even a read-only mount mangles bufobj of device vnode
> 3. Bug!
> Trivial fix with POLA violation - prohibit concurrent RO mounts.
> Non-trivial fix - _somehow_ avoid changing or depending on device
> vnode bufobj.

> See this for even more evil example of this problem:
> http://lists.freebsd.org/pipermail/freebsd-fs/2009-February/005676.html

thanks a lot for the hint. unfortunately i'm not a programmer and thus won't
be able to help with this problem. :-(

cheers.
alex