[PATCH] Make udf(4) MPSAFE and use shared lookups
John Baldwin
jhb at freebsd.org
Thu Nov 20 14:32:00 PST 2008
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.
--
John Baldwin
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