Re: 2.6.0-test8, DEBUG_SLAB, oops in as_latter_request()

[Jens Axboe <axboe@suse.de>]

On Mon, Oct 20 2003, Nick Piggin wrote:
> 
> 
> Andrew Morton wrote:
> 
> >Peter Osterlund <petero2@telia.com> wrote:
> >
> >>I was running 2.6.0-test8 compiled with CONFIG_DEBUG_SLAB=y. When
> >>testing the CDRW packet writing driver, I got an oops in
> >>as_latter_request. (Full oops at the end of this message.) It is
> >>repeatable and happens because arq->rb_node.rb_right is uninitialized.
> >>
> >
> >deadline seems to have the same problem.
> >
> >We may as well squish this with the big hammer?
> >
> 
> Thanks for the report, Peter.
> 
> The request is a special request, so either blk_attempt_remerge should
> never be called on it, or blk_attempt_remerge (or as_latter_request) should
> check for this. Its up to Jens.
> 
> I would say to stick something like
> if (!rq_mergeable(rq))
>    return;
> 
> into blk_attempt_remerge.
> 
> I'd say we shouldn't expect drivers to try to get this right.

attempt_merge() already includes such a check. To me it looks really
buggy that elv_latter_request() cannot be called on non-fs requests, I'd
rather get that fixed like Peter suggests. elv_latter_request() should
work on all requests in the io sched queue, period.

-- 
Jens Axboe