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

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Message-Id: <46D78DAB-6120-4698-BC51-3A48E20EDB0E@kernel.dk>
Date:	Thu, 31 Jan 2008 19:16:54 +0100
From:	Jens Axboe <axboe@...nel.dk>
To:	Kiyoshi Ueda <k-ueda@...jp.nec.com>
Cc:	"jens.axboe@...cle.com" <jens.axboe@...cle.com>,
	"nai.xia@...il.com" <nai.xia@...il.com>,
	"rdreier@...co.com" <rdreier@...co.com>,
	"bzolnier@...il.com" <bzolnier@...il.com>,
	"bbpetkov@...oo.de" <bbpetkov@...oo.de>,
	"flo@...822.org" <flo@...822.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"j-nomura@...jp.nec.com" <j-nomura@...jp.nec.com>,
	"linux-ide@...r.kernel.org" <linux-ide@...r.kernel.org>,
	"mingo@...e.hu" <mingo@...e.hu>,
	"clameter@....com" <clameter@....com>,
	"travis@....com" <travis@....com>,
	"k-ueda@...jp.nec.com" <k-ueda@...jp.nec.com>
Subject: Re: kernel BUG at ide-cd.c:1726 in 2.6.24-03863-g0ba6c33 &&  -g8561b089



On 31/01/2008, at 18.04, Kiyoshi Ueda <k-ueda@...jp.nec.com> wrote:

> Hi Jens,
>
> On Thu, 31 Jan 2008 14:05:58 +0100, Jens Axboe wrote:
>> On Thu, Jan 31 2008, Nai Xia wrote:
>>> My dmesg relevant info is quite similar:
>>>
>>> [    6.875041] Freeing unused kernel memory: 320k freed
>>> [    8.143120] ide-cd: rq still having bio: dev hdc: type=2,  
>>> flags=114c8
>>> [    8.144439]
>>> [    8.144439] sector 10824201199534213, nr/cnr 0/0
>>> [    8.144439] bio cf029280, biotail cf029280, buffer 00000000, data
>>> 00000000, len 158
>>> [    8.144439] cdb: 12 00 00 00 fe 00 00 00 00 00 00 00 00 00 00 00
>>> [    8.144439] backup: data_len=158  bi_size=158
>>> [    8.160756] ide-cd: rq still having bio: dev hdc: type=2,  
>>> flags=114c8
>>> [    8.160756]
>>> [    8.160756] sector 2669858, nr/cnr 0/0
>>> [    8.160756] bio cf029300, biotail cf029300, buffer 00000000, data
>>> 00000000, len 158
>>> [    8.160756] cdb: 12 01 00 00 fe 00 00 00 00 00 00 00 00 00 00 00
>>> [    8.160756] backup: data_len=158  bi_size=158
>>> [   14.851101] eth0: link up
>>> [   27.121883] eth0: no IPv6 routers present
>>>
>>>
>>> And by the way, Kiyoshi,
>>> This can be reproduced in a typical setup vmware workstation 6.02  
>>> with
>>> a vritual IDE cdrom,
>>> in case you wanna catch that with your own eyes. :-)
>>> Thanks for your trying hard to correct this annoying bug.
>>
>> The below fix should be enough. It's perfectly legal to have leftover
>> byte counts when the drive signals completion, happens all the time  
>> for
>> eg user issued commands where you don't know an exact byte count.
>>
>> diff --git a/drivers/ide/ide-cd.c b/drivers/ide/ide-cd.c
>> index 74c6087..bee05a3 100644
>> --- a/drivers/ide/ide-cd.c
>> +++ b/drivers/ide/ide-cd.c
>> @@ -1722,7 +1722,7 @@ static ide_startstop_t cdrom_newpc_intr 
>> (ide_drive_t *drive)
>>     */
>>    if ((stat & DRQ_STAT) == 0) {
>>        spin_lock_irqsave(&ide_lock, flags);
>> -        if (__blk_end_request(rq, 0, 0))
>> +        if (__blk_end_request(rq, 0, rq->data_len))
>>            BUG();
>>        HWGROUP(drive)->rq = NULL;
>>        spin_unlock_irqrestore(&ide_lock, flags);
>
> OK, I undarstand the leftover is legal.
>
> By the way, is it safe to always return success if there is a  
> leftover?
> I thought we might have to complete the rq with -EIO in such case.

data_len being non zero should pass the residual count back to the  
issuer. 
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