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On Tue, Mar 29, 2005 at 11:01:21AM -0800, Cliff Wright wrote:
>  Some questions have come up. The driver code has NOTE 1 which says
> "This uses the VOP_BMAP/VOP_STRATEGY interface to the vnode
> instead of a simple VOP_RDWR.
> We do this to avoid distorting the local buffer cache."
> I used vn_rdwr because it was simpler, so what distortion am I causing?

The problem is that the buffer cache then contains two copies of the
data - once for the vnd file, and once for the file in the filesystem
mounted off the vnd device.

vnd needs some structural rework to address a couple of other known
problems, too.  In that process, it's possible that some recent work
by Chuck Silvers makes using the higher-level vnops without causing
this cache pollution feasible, and that would certainly simplify vnd.

--
Dan.
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