linux-kernel - Re: [GIT PULL] Core block IO bits for 2.6.39

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Date:	Thu, 24 Mar 2011 20:36:15 +0100
From:	Jens Axboe <jaxboe@...ionio.com>
To:	Markus Trippelsdorf <markus@...ppelsdorf.de>
CC:	Linus Torvalds <torvalds@...ux-foundation.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Chris Mason <chris.mason@...cle.com>
Subject: Re: [GIT PULL] Core block IO bits for 2.6.39 - early Oops

On 2011-03-24 20:34, Markus Trippelsdorf wrote:
> On 2011.03.24 at 19:58 +0100, Jens Axboe wrote:
>> On 2011-03-24 19:54, Markus Trippelsdorf wrote:
>>> On 2011.03.24 at 19:51 +0100, Jens Axboe wrote:
>>>> On 2011-03-24 19:36, Jens Axboe wrote:
>>>>> On 2011-03-24 19:30, Markus Trippelsdorf wrote:
>>>>>> On 2011.03.24 at 14:43 +0100, Jens Axboe wrote:
>>>>>>>
>>>>>>> This is the main pull request for the block IO layer and friends for
>>>>>>> 2.6.39.
>>>>>>
>>>>>> This merge results in an early oops on my system (amd64, xfs).
>>>>>> See the attached photo.
>>>>>>
>>>>>
>>>>> Auch. Can you ensure that you have CONFIG_DEBUGINFO=y in your .config
>>>>> and then do:
>>>>>
>>>>> $ gdb vmlinux
>>>>> ...
>>>>> l *cfq_insert_request+0x32
>>>>>
>>>>> and send that output?
>>>>
>>>> I took a closer look at the oops, and it most likely looks like q ==
>>>> NULL (offset 0x18 == q->elevator). You left out the Code part, so I
>>>> can't verify that for certain. Which makes very little sense. I take it
>>>> this is 100% reproducible? When you send the gdb output, please also
>>>> attach your .config.
>>>
>>> Yes, it's 100% reproducible here. My .config follows:
>>
>> Can you try this patch and see if it makes a difference?
> 
> There's no patch ;-)

Oh, here it is.

>> If you boot without the patch and add elevator=noop, does it then work?
> 
> It works insofar as the Oops is gone. But my xfs partitions apparently
> still get corrupted (I had to run xfs_repair on several of them, because
> they would not mount otherwise).

That's very worrying.

diff --git a/block/elevator.c b/block/elevator.c
index c387d31..77669ad 100644
--- a/block/elevator.c
+++ b/block/elevator.c
@@ -691,8 +691,10 @@ void elv_insert(struct request_queue *q, struct request *rq, int where)
 		 * queue already, we are done - rq has now been freed,
 		 * so no need to do anything further.
 		 */
+#if 0
 		if (elv_attempt_insert_merge(q, rq))
 			break;
+#endif
 	case ELEVATOR_INSERT_SORT:
 		BUG_ON(rq->cmd_type != REQ_TYPE_FS &&
 		       !(rq->cmd_flags & REQ_DISCARD));

-- 
Jens Axboe

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