Re: kern/47040: renaming mount point panics in namei

[Taylor R Campbell <campbell+netbsd%mumble.net@localhost>]

   Date: Tue, 9 Oct 2012 15:19:56 +0000
   From: David Holland <dholland-bugs%netbsd.org@localhost>

   On Fri, Oct 05, 2012 at 02:00:08PM +0000, Taylor R Campbell wrote:
    >   I had a directory /foo/bar/current.ro, and I wanted to rename
    >   it to /foo/current.ro, so I ran
    > 
    >           % mv bar/current.ro .
    > 
    >   from /foo, forgetting that /foo/bar/current.ro had a file
    >   system mounted.  This immediately triggered a panic in namei:
    > 
    >           panic: leaf `current.ro' should be empty

   Which fs(es)?

/ is ffs sync, /foo is ffs async, and /foo/bar/current.ro is nullfs
mounted read-only from /foo/bar/current, which is not a mount point.