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Re: Replace lockmgr for vnodes
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.
> Now I should schedule a few weeks of idle time to read your other mail ...
David A. Holland
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