Re: cfq crashing on boot with CONFIG_DEBUG_PAGE_ALLOC (linus master)

From: Chris Mason
Date: Tue Jan 17 2012 - 12:59:17 EST


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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