linux-kernel - Re: [PATCH] writeback: verify that underlying dev exists before getting its name

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Message-ID: <20150904173650.GF25329@mtj.duckdns.org>
Date:	Fri, 4 Sep 2015 13:36:50 -0400
From:	Tejun Heo <tj@...nel.org>
To:	Sasha Levin <sasha.levin@...cle.com>
Cc:	rostedt@...dmis.org, mingo@...hat.com, axboe@...com,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] writeback: verify that underlying dev exists before
 getting its name

Hello,

On Fri, Sep 04, 2015 at 01:20:42PM -0400, Sasha Levin wrote:
> > Do you have backtrace of this happening?  There's a bug in cleanup
> > path which causes oops (patch is being tested) and this may just be a
> > symptom of the same problem.
> 
> [268773.335933] kasan: GPF could be caused by NULL-ptr deref or user memory accessgeneral protection fault: 0000 [#1] PREEMPT SMP DEBUG_PAGEALLOC KASAN
> [268773.337986] Modules linked in:
> [268773.338470] CPU: 3 PID: 12812 Comm: trinity-c10 Not tainted 4.2.0-next-20150902-sasha-00045-gd0866f3-dirty #2528
> [268773.339903] task: ffff8802f56e4000 ti: ffff880322e10000 task.ti: ffff880322e10000
> [268773.340943] RIP: 0010:[<ffffffffaa8b8284>]  [<ffffffffaa8b8284>] trace_event_raw_event_writeback_dirty_page+0x1b4/0x420

Hmm.... did this happen while or around a device removal event?  I'm
trying to figure out whether an unregistered bdi can have inodes.

Thanks.

-- 
tejun
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