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Date: Sun, 17 Sep 1995 19:48:54 +1000
From: Bruce Evans <bde@zeta.org.au>
Message-Id: <199509170948.TAA08597@godzilla.zeta.org.au>
To: current@freebsd.org
Subject: assorted cdrom driver and nfs bugs
Sender: owner-current@freebsd.org
Precedence: bulk

I tried this to demonstrate a bug in the SCSI cdrom driver:

    Mount a cdrom on cd0a.			# OK.
    Attempt to eject cdrom.			# OK, this fails because of
						  locking.
    dd if=/dev/rcd0a of=/dev/null count=1.	# Peek at complementary device
						# to demonstrate broken
						# close().
    Attempt to eject cdrom.			# BUG, this succeeds.

All or almost all cdrom drivers have this bug.  It is most easily fixed by
letting the slice driver keep track of opens.

Attempting to recover from this showed a bug in nfsv3:

    Reload cdrom.				# OK.
    umount /dev/cd0a.				# OK.
    Mount cdrom on cd0a again.			# OK.

Now on a client running nfsv3 with the cdrom nfs-mounted through all this:

    df.						# Panic (null pointer in
						  nfs_statfs()).
    Reboot client.				# OK
    df.						# Panic (as above).

Bruce