Re: Replace lockmgr for vnodes

[David Holland <dholland-tech%netbsd.org@localhost>]

On Wed, Mar 19, 2008 at 06:01:57PM +0200, Antti Kantee wrote:
 > > I doubt that. While namei is certainly a mess (and is the proximate
 > > cause of substantial mess in every fs function that receives a
 > > componentname) its locking is basically very simple. Whereas I think
 > > it's pretty safe to assume at this point that almost every rename
 > > implementation is wrong in some fashion.
 > 
 > I'd call the locking/calling convention anything but simple.  I did
 > rump_syscalls last week exactly because all my hand-crafted syscalls
 > had bugs in the calls to namei.  I don't think I even can list all
 > the rules off the top of my head.  Stuff like "LOCKPARENT returns dvp
 > locked unless no LOCKLEAF and dvp == vp" and "namei returns 0 for CREATE
 > depending on if dvp exists and is writable instead of whether vp exists"
 > always make me want to have more coffee (or vodka, depending on the
 > level of desperation).

Well, granted. But all that garbage is slated for disposal anyway; it
definitely has no place in the way things *should* be, which is what
we're theoretically talking about in this thread.

 > But I'll give you this.  Even though there are more calls to namei than
 > implementations of rename, they're generally a billion times easier to
 > test since triggering bugs doesn't depend on weird timings.

Indeed.

 > Now I should schedule a few weeks of idle time to read your other mail ...

Ayup :-)

-- 
David A. Holland
dholland%netbsd.org@localhost