> > there's no problem to having a routine that won't fail.
> > and there's no problem not to checking its failure.
> 
> I agree that there's no problem in having a routine that can't fail, nor 
> ignoring any "error" return value in such a case. I still feel, though, 
> that vn_lock() isn't that routine.

afaik, vn_lock(LK_RETRY) is *currently* supposed not to fail.
(if someone try to acquire a drained lock, its a bug in the caller.)
is there a way to change your feeling? :-)

> Maybe, maybe not. One advantage of our node locking protocol is that the 
> locking is visable to the caller. So the caller can use the lock to 
> perform a sequence of actions atomically.

no.
you shouldn't use vnode locking for such purpose because
VOPs are allowed to be no-op as genfs_nolock.
(i know that our nfsd does such.  it should be changed, IMO.)

> > btw, please answer my first question.
> > are you going to add checks on every vn_lock(LK_RETRY)?
> 
> Not at the present time. While I think that would be a good and correct
> thing, I do not have the time nor energy to change each occurrence.

i see.  thanks.
as i still disagree,
please have a discussion here (tech-kern@) before doing so..

YAMAMOTO Takashi