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

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
>  >
>  > _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.

Yeah, we could fix that also.

Thanks,
Attilio


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