vnode refcnt bug?

[Erez Zadok]

Please see this short thread of discussion on amd-dev.  I've included two
messages from this thread.  It suggests that fbsd5 may have a vnode refcount
bug (a vnode isn't held where it should).

I've not personally investigated this bug.  Does anyone on fs@ has come
across such a possible bug?

Thanks
Erez.

------- Forwarded Message

Date:    Tue, 25 Nov 2003 18:41:40 +0100
From:    scholler at fnb.tu-darmstadt.de (Ulrich Scholler)
To:      amd-dev at cs.columbia.edu
Subject: Re: amd unmounting out from under a cwd

Hi,

On Tue Nov 25, 2003 at 12:29:27 -0500, Andrew Siegel wrote:
> What's happening is: I cd into an automounted directory,
> the mount occurs normally, and I leave my shell there.
> 5 minutes later, amd unmounts that mount point out from
> under me.  The shell no longer has a working directory:
> 
>    zayin abs % pwd
>    pwd: .: No such file or directory
> 
> 
> I have several hundred machines here (Redhat 7.3, IRIX 6.5.12,
> FreeBSD 4) running amd (mostly 6.0.9), all with the same
> configuration file and maps, and this is the only one that
> shows this problem, making me think it's something about
> FreeBSD 5.1.
> 
> I'm attaching a debugging log.  The directory that is being
> mounted and then incorrectly unmounted is /u/abs.

Are you sure that your shell's cwd is actually /u/abs?  Some programs
seem to dereference the symlink and set the cwd to the actual mount
point.  amd is perfectly right to unmount it, since it is not accessed
via the amd-provided symlink.

Regards,

uLI
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------- Forwarded Message

Date:    Tue, 25 Nov 2003 11:24:42 -0700
From:    John E Hein <jhein at timing.com>
To:      Andrew Siegel <abs at blueskystudios.com>
Cc:      amd-dev at cs.columbia.edu
Subject: amd unmounting out from under a cwd

Andrew Siegel wrote at 12:29 -0500 on Nov 25:
 > I've got a problem that I've never seen before with amd
 > under FreeBSD 5.1.  Versions 6.0.7 (as delivered with the
 > FreeBSD 5.1 distribution) and 6.1b4 (compiled by me) share
 > this problem.

Definitely a FreeBSD 5.* problem.  I've noticed it since using early
versions of 5.  I haven't tracked it down yet since it's been more of
an inconvenience than anything (for instance, 'pushd /tmp ; popd'
"fixes" it).
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------- End of Forwarded Message