Re: [patch 2.6.15-rc2] blk: request poisoning

From: Nick Piggin
Date: Mon Nov 21 2005 - 02:58:48 EST

Jens Axboe wrote:
On Mon, Nov 21 2005, Nick Piggin wrote:

This patch should make request poisoning more useful
and more easily extendible in the block layer.

Don't think I have hardware that will trigger a requeue,
but otherwise it has been moderately tested. Comments?

I like the idea, but I'm a little worried that it actually introduces
more problems than it solves. See the mail from yesterday for instance,
perfectly fine code but 'as' poisoning triggered.

And the merging bits already look really ugly :/

So I guess my question is, did this code ever find any driver problems?

I think it found a few things here and there. Requeueing had a
couple of bugs, and I think a couple of things turned up back when
AS was a new concept to the block layer.

I think it is useful to try to enforce a coherent usage of the block
interface by drivers. For example, the IDE thing may have been a non
issue, but you might imagine some io scheduler or future accounting
(or something) in the block layer actually does need the request to
go through elv_set_request / blk_init_request.

Up to you really. I'm going to rip the code out of as-iosched.c so
I just thought it may still be useful for the block layer.


SUSE Labs, Novell Inc.

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