[PATCH] Make udf(4) MPSAFE and use shared lookups
Attilio Rao
attilio at freebsd.org
Thu Nov 20 14:33:23 PST 2008
2008/11/20, John Baldwin <jhb at freebsd.org>:
> 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
> >
> > @@ -589,6 +582,22 @@
> > 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.
Yeah, we could fix that also.
Thanks,
Attilio
--
Peace can only be achieved by understanding - A. Einstein
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