Subject: unmounting filesystem but already underlying device is gone.
To: None <firstname.lastname@example.org>
From: enami tsugutomo <email@example.com>
Date: 09/25/1999 23:18:41
If I or kernel on reboot tries to umount a filesytem but its
underlying device is already gone (eg, due to vdevgone), we get panic
due to null pointer dereference.
The unmount vfs call tries to clear SI_MOUNTEDON bit of v_specflags,
but v_specinfo is already deallocated and NULL is assgined.
So, what is the right way to avoid this? If I check vnode type and
make sure it is not VBAD before touching v_specflags prevent me from
crash, but I wonder if it is right way or not...