Andrea Arcangeli wrote:
>
> On Tue, Nov 28, 2000 at 10:50:06AM +1100, Neil Brown wrote:
> > However, there is only one "unplug-all-devices"(*) call in the API
> > that a reader or write can make. It is not possible to unplug a
> > particular device, or better still, to unplug a particular request.
>
> This isn't totally true. When we run out of requests on a certain
> device and we must startup the I/O to release some of them, we unplug
> only the _single_ device and we don't unplug-all-devices anymore.
>
> So during writes to disk (without using O_SYNC that isn't supported
> by 2.4.0-test11 anyways :) you never unplug-all-devices, but you only
> unplug finegrined at the harddisk level.
>
> That isn't true for reads of course, for reads it's the highlevel FS/VM layer
> that unplugs the queue and it only knows about the run_task_queue(&tq_disk) but
> Jens has patches to fix it too :).
>
> Andrea
but the point is that you have a confounding interface for the task that he has.
We need vm to push the FS which pushes raid, and the FS needs to know about or even
contain the
stripe cache.
Hans
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