kern/47022: namecache is confused, particularly for rename and rmdir

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

>Number:         47022
>Category:       kern
>Synopsis:       namecache is confused, particularly for rename and rmdir
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Sun Sep 30 21:20:01 +0000 2012
>Originator:     Taylor R Campbell <campbell+netbsd%mumble.net@localhost>
>Release:        NetBSD 6.99.11
>Organization:
>Environment:
Architecture: i386
Machine: i386
>Description:

        The rules for using the namecache are not clear, every file
        system's rename vop will cache_purge different sets of vnodes
        under different sets of conditions none of which is obviously
        correct, we probably overzealously clear the cache in various
        circumstances, and the whole thing shouldn't have its tendrils
        in the file systems at all anyway.

>How-To-Repeat:

        Code inspection.

>Fix:

        Yes, please!