On Wed, 27 May 2009, James Bottomley wrote: > Hardly ... our current refcounting is on destruction (releases). This > problem is an instance of visibility (the del calls) we need the > visibility teardown to work nicely. We currently have no refcounting on > the visibility. Even if we did (and we could add a ref on when the > underlying device del calls are done), what happens if the target needs > to become visible again. Apparently the generic device infrastructure > can't accept doing an add on a previously del'd device. Definitely not. > The most obvious way of fixing this is to have a special case for > targets of dying hosts ... they could call del early on the > understanding that they're never getting new underlying devices. That > would allow the wait to trigger on the last target del, which is what is > optimal. I don't understand all the subtle issues here. In other contexts, the solution would be to initialize a refcount to 1 when the target is allocated, increment it when a device is added, and decrement it when a device is removed or the host is removed. When the refcount goes to 0, the target is deleted. Why wouldn't this kind of approach work? Alan Stern -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
