linux-kernel - Re: kernel BUG at ide-cd.c:1726 in 2.6.24-03863-g0ba6c33 && -g8561b089

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Message-Id: <20080129.182356.70224412.k-ueda@ct.jp.nec.com>
Date:	Tue, 29 Jan 2008 18:23:56 -0500 (EST)
From:	Kiyoshi Ueda <k-ueda@...jp.nec.com>
To:	bzolnier@...il.com, rdreier@...co.com
Cc:	nai.xia@...il.com, flo@...822.org, linux-kernel@...r.kernel.org,
	jens.axboe@...cle.com, j-nomura@...jp.nec.com, k-ueda@...jp.nec.com
Subject: Re: kernel BUG at ide-cd.c:1726 in 2.6.24-03863-g0ba6c33 &&
 -g8561b089

Hi Bart, 

On Tue, 29 Jan 2008 14:22:53 -0800, Roland Dreier wrote:
> Hi, I saw the same BUG from ide-cd on one of my systems.  I applied
> the debugging patch to replace the BUG with blk_dump_rq_flags(), and I
> got the output below (full boot log and .config attached to this
> email).
> 
> Please let me know if there's anything else that would help debug the
> problem.

Thank you for the information, Roland.

 
> [    4.072271] Uniform CD-ROM driver Revision: 3.20
> [    4.098236] ide-cd: rq still having bio: dev hda: type=2, flags=114c8
> [    4.100269]
> [    4.100269] sector 1949759, nr/cnr 0/0
> [    4.100269] bio ffff8102418cc600, biotail ffff8102418cc600, buffer 0000000000000000, d8
> [    4.100269] cdb: 12 00 00 00 fe 00 00 00 00 00 00 00 00 00 00 00
> [    4.101005] ide-cd: rq still having bio: dev hda: type=2, flags=114c8
> [    4.104269]
> [    4.104269] sector 1949759, nr/cnr 0/0
> [    4.104269] bio ffff8102418cc600, biotail ffff8102418cc600, buffer 0000000000000000, d2
> [    4.104269] cdb: 12 00 00 00 fe 00 00 00 00 00 00 00 00 00 00 00
> [    4.109203] ide-cd: rq still having bio: dev hda: type=2, flags=114c8
> [    4.112270]
> [    4.112270] sector 1949759, nr/cnr 0/0
> [    4.112270] bio ffff8102418cc600, biotail ffff8102418cc600, buffer 0000000000000000, d8
> [    4.112270] cdb: 12 01 00 00 fe 00 00 00 00 00 00 00 00 00 00 00
> [    4.112945] ide-cd: rq still having bio: dev hda: type=2, flags=114c8
> [    4.116270]
> [    4.116270] sector 1949759, nr/cnr 0/0
> [    4.116270] bio ffff8102418cc600, biotail ffff8102418cc600, buffer 0000000000000000, d2
> [    4.116270] cdb: 12 01 00 00 fe 00 00 00 00 00 00 00 00 00 00 00

Bart,
This means that the rq still has a bio even after DRQ_STAT is cleared.
The original ide-cd code was calling only end_that_request_last() there.
So I thought that the rq should have no bio when DRQ_STAT is cleared,
otherwise the bio leaks.

Was my understanding wrong and is that correct behavior in ide-cd?

Thanks,
Kiyoshi Ueda
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