On Tue, Aug 12, 2003 at 10:45:13PM +0200, Juergen Hannken-Illjes wrote:
> 	if ((error = vn_start_write(vp, &mp, V_WAIT | PCATCH)) != 0)
> 		return (error);
> 	do_the_write_operation
> 	vn_finished_write(mp);
> 
> or
> 
> restart:
> 	prepare_a_write_operation
> 	if (vn_start_write(nd.ni_dvp, &mp, V_NOWAIT) != 0) {
> 		abort_current_preparation
> 		if ((error = vn_start_write(NULL, &mp, V_XSLEEP | PCATCH)) != 0)
> 			return (error);
> 		goto restart;
> 	}
> 	do_the_write_operation
> 	vn_finished_write(mp);

I proposed a VOP_THROTTLE for something like this a long time ago.
It never made it, but I think throttling mechanisms can be built in
to this, and it can be used for a more generic snapshot solution
too. So, I support adding an interface like this.

- Frank