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

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Date:	Tue, 17 Jan 2012 09:35:00 -0800
From:	Tejun Heo <tj@...nel.org>
To:	Chris Mason <chris.mason@...cle.com>
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 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

Thanks.

-- 
tejun
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