linux-kernel - Re: cfq crashing on boot with CONFIG_DEBUG_PAGE

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Date:	Tue, 17 Jan 2012 12:59:10 -0500
From:	Chris Mason <chris.mason@...cle.com>
To:	Tejun Heo <tj@...nel.org>
Cc:	Jens Axboe <axboe@...nel.dk>, LKML <linux-kernel@...r.kernel.org>
Subject: Re: cfq crashing on boot with CONFIG_DEBUG_PAGE_ALLOC (linus master)

On Tue, Jan 17, 2012 at 09:35:00AM -0800, Tejun Heo wrote:
> On Tue, Jan 17, 2012 at 11:10:24AM -0500, Chris Mason wrote:
> > Hi everyone,
> > 
> > Looks like cfq is using stale pages, I'm getting crashes on boot with
> > CONFIG_DEBUG_PAGE_ALLOC enabled.  The oops leads to crashing in
> > cfqq_type, and if you add some fuzz for inlining, it looks like we're
> > here:
> > 
> > (gdb) list *cfq_insert_request+0x3f5
> > 0xffffffff812683d8 is in cfq_insert_request (block/cfq-iosched.c:3131).
> > 3126	
> > 3127		/*
> > 3128		 * workload type is changed, don't save slice, otherwise preempt
> > 3129		 * doesn't happen
> > 3130		 */
> > 3131		if (cfqq_type(old_cfqq) != cfqq_type(cfqq))
> > 3132			cfqq->cfqg->saved_workload_slice = 0;
> > 3133	
> > 3134		/*
> > 3135		 * Put the new queue at the front of the of the current list,
> > 
> > It seems like the most likely reason is that old_cfqq was previously
> > freed:
> > 
> >         struct cfq_queue *old_cfqq = cfqd->active_queue;
> 
> Does the following patch resolve the problem?
> 
>   http://article.gmane.org/gmane.linux.kernel.next/20340/raw

Sorry, same oops with this applied.

-chris

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