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On Mon, Jun 21, 2004 at 09:09:10AM +0900, YAMAMOTO Takashi wrote:
> > > i think that having some tricks in VOP_LOCK/UNLOCK/ISLOCKED is enough.
> > > (in addition to stopping exporting v_vnlock, of course.)
> >=20
> > What "tricks" could merge locks A and B into B?
>=20
> something like this:
> 	ffs_lock(...)
> 	{
>=20
> 		genfs_lock(vp, ...);
> 		if (vp is snapshot) {
> 			lockmgr(snaplk, ...);
> 		}
> 	}

That 1) forces all callers to pay a (slight) penalty for snapshot support=
=20
being present, even if they never use it, and 2) it destroys our ability=20
to use v_vnlock. v_vnlock makes life much nicer for layered file systems,=
=20
as it lets us readily access one lock for a stack of vnodes.

Take care,

Bill

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