Re: [PATCH] Make udf(4) MPSAFE and use shared lookups

On Thursday 20 November 2008 05:02:29 pm Attilio Rao wrote:
> 2008/11/20, John Baldwin <jhb_at_freebsd.org>:
> > So this patch is fairly minimal since udf(4) is currently read-only.  The
> >  changes include:
> >
> >  * Set VV_ROOT in udf_vget() if we ever return a vnode instead of doing it 
only
> >   in udf_root().  This matches the behavior of other operating systems and
> >   correctly tags the root vnode with VV_ROOT in the unlikely case that we
> >   create the vnode during a call to ufs_vget() that does not come from
> >   ufs_root().
> >  * If the hash lookup in ufs_vget() fails, ensure an exclusive vnode lock 
is
> >   used while creating the new vnode (same as UFS).
> >  * Allow lock recursion (XXX: not really sure this is needed actually).
> >  * Allow shared vnode locks on non-fifos.
> >  * Honor the requested locking flags (shared vs exclusive) instead of 
always
> >   using exclusive vnode locks during a lookup operation.
> >  * Handle "." lookups the same way other filesystems do by just bumping 
the
> >   reference on 'dvp' rather than calling udf_vget().
> >
> >  http://www.FreeBSD.org/~jhb/patches/udf_mpsafe.patch
> 
> _at__at_ -589,6 +582,22 _at__at_
>  	if (error || *vpp != NULL)
>  		return (error);
> 
> +	/*
> +	 * We must promote to an exclusive lock for vnode creation.  This
> +	 * can happen if lookup is passed LOCKSHARED.
> + 	 */
> +	if ((flags & LK_TYPE_MASK) == LK_SHARED) {
> +		flags &= ~LK_TYPE_MASK;
> +		flags |= LK_EXCLUSIVE;
> +	}
> +
> 
> On -CURRENT, operations are bitwise (differently from 7.x and such).
> What you want to do is just:
> flag = (flag & ~LK_SHARED) | LK_EXCLUSIVE;

I just copied and pasted from UFS in HEAD.

-- 
John Baldwin