Re: CVS commit: src/sys/kern

[Juergen Hannken-Illjes <hannken%eis.cs.tu-bs.de@localhost>]

On Tue, Aug 17, 2010 at 04:35:31PM +0300, Antti Kantee wrote:
> On Tue Aug 17 2010 at 13:17:48 +0000, Juergen Hannken-Illjes wrote:
> > Module Name:        src
> > Committed By:       hannken
> > Date:               Tue Aug 17 13:17:48 UTC 2010
> > 
> > Modified Files:
> >     src/sys/kern: vfs_subr.c
> > 
> > Log Message:
> > Now that ffs on disk inodes get freed in the reclaim routine it is no longer
> > necessary for vget() to handle VI_INACTNOW as a special case.  Remove this
> > check and its support in vrelel().
> 
> Hi,
> 
> I didn't fully review your changes, so just to make sure: it's still
> possible to gain a reference during inactive, right?

Yes.

> > Getting another reference while the freelist is locked is an error.  Replace
> > the check with a KASSERT.
> > 
> 
> >     vp->v_freelisthd = NULL;
> >     mutex_exit(&vnode_free_list_lock);
> >  
> > -   if (vp->v_usecount != 0) {
> > -           /*
> > -            * was referenced again before we got the interlock
> > -            * Don't return to freelist - the holder of the last
> > -            * reference will destroy it.
> > -            */
> > -           mutex_exit(&vp->v_interlock);
> > -           mutex_enter(&vnode_free_list_lock);
> > -           goto retry;
> > -   }
> > +   KASSERT(vp->v_usecount == 0);
> 
> It's not obvious from your commit message what prevents it from gaining
> a reference after the lock is dropped.

The interlock is taken before the freelist lock is dropped and vnodes on
the free lists should never appear on other lists.

-- 
Juergen Hannken-Illjes - hannken%eis.cs.tu-bs.de@localhost - TU Braunschweig 
(Germany)