[PATCH] Make udf(4) MPSAFE and use shared lookups
Attilio Rao
attilio at freebsd.org
Thu Nov 20 14:02:31 PST 2008
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;
The other parts look good (except that IIRC stlye wants all multi-line
comments to be preceeded by a white, empty line).
Thanks,
Attilio
--
Peace can only be achieved by understanding - A. Einstein
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