Message-ID: <49D6777F.3090305@gmail.com>
Date:	Fri, 03 Apr 2009 22:54:23 +0200
From:	Niel Lambrechts <niel.lambrechts@...il.com>
To:	Jeff Garzik <jeff@...zik.org>
CC:	Tejun Heo <tj@...nel.org>,
	"linux.kernel" <linux-kernel@...r.kernel.org>
Subject: Re: 2.6.29 regression: ATA bus errors on resume

On 04/03/2009 10:09 PM, Jeff Garzik wrote:
> Niel Lambrechts wrote:
>> On 03/30/2009 04:40 PM, Jeff Garzik wrote:
>>> Niel Lambrechts wrote:
>>>> On 03/30/2009 11:00 AM, Tejun Heo wrote:
>>>>> Hello,
>>>>>
>>>>> For some reason, I can't find the original thread, so replying here.
>>>>>
>>>>> Niel Lambrechts wrote:
>>>>>>>>>> The ext4 errors are interleaved with hardware errors, and the
>>>>>>>>>> ext4
>>>>>>>>>> errors are about I/O errors.
>>>>>>>>>>
>>>>>>>>>> EXT4-fs error (device sda6): __ext4_get_inode_loc: unable to
>>>>>>>>>> read inode block - inode=2346519
>>>>>>>>>> EXT4-fs error (device sda6) in ext4_reserve_inode_write: IO
>>>>>>>>>> failure
>>>>>>>>>>
>>>>>>>>>> This looks more like a hibernation problem than an ext4 problem.
>>>>>>>>>> Looks like the hard drive is being left in some inconsistent
>>>>>>>>>> state
>>>>>>>>>> after resuming from hibernation.
>>>>> Yeap, ext4 is just the victim here.
>>>>>
>>>>>>>>> ata1.00: irq_stat 0x00400008, PHY RDY changed
>>>>>>>>> ata1: SError: { PHYRdyChg CommWake }
>>>>>>>> Your SATA hardware flags a connect-or-disconnect event ("PHY
>>>>>>>> RDY"), which requires us to abort a bunch of queued commands:
>>>>>>>>
>>>>>>>>> ata1.00: cmd 60/18:00:77:88:6f/00:00:0e:00:00/40 tag 0 ncq
>>>>>>>>> 12288 in
>>>>>>>>>          res 50/00:30:07:b3:10/00:00:0c:00:00/40 Emask 0x10 (ATA
>>>>>>>>> bus error)
>>>>>>>> [...]
>>>>> ...
>>>>>>>> The SCSI subsystem aborts each of the queued commands.
>>>>>>> No .. this is the SCSI subsystem receives an ABORTED COMMAND
>>>>>>> return in
>>>>>>> sense data for each of the outstanding I/Os
>>>>>>>
>>>>>>> The only place these are generated is in ata_sense_to_error()
>>>>>>> which only
>>>>>>> occurs if there's some type of ata error.
>>>>>>>
>>>>>>> If I had to theorise, I'd say the system suspended with commands
>>>>>>> outstanding to the device.  On resume, the device gets reset and
>>>>>>> returns
>>>>>>> some type of ATA error which gets translated to ABORTED COMMAND
>>>>>>> which
>>>>>>> causes a failure.
>>>>>>>
>>>>>>> In the mid layer, we translate ABORTED_COMMAND into a retry
>>>>>>> until the
>>>>>>> command runs out of them ... could it be there's a race readying
>>>>>>> the
>>>>>>> device and we run through the retries before it can accept the
>>>>>>> command?
>>>>> When libata-eh thinks that the problem isn't worth retrying, it sets
>>>>> scmd->retries to scmd->allowed so that it gets aborted immediately.
>>>>> The code is in ata_eh_qc_complete().
>>>>>
>>>>> Whether a command is to be retried or not is determined with
>>>>> ATA_QCFLAG_RETRY which is set in ata_eh_link_autopsy() for each
>>>>> failed
>>>>> command.  Immediate-failure criteria is pretty strict - only driver
>>>>> software errors (AC_ERR_INVALID) and PC or other special commands
>>>>> which failed which got aborted by the device get the immediate pink
>>>>> slip.  In this case, the commands are from FS and failed with
>>>>> AC_ERR_ATA_BUS, so it definitely doesn't fit into the criteria.
>>>>> Strange.
>>>>>
>>>>> How reproducible is the problem?  Are you interested in trying out
>>>>> some debug patches?
>>>> Hi Tejun,
>>>>
>>>> I think I should be able to reproduce when actively using X with
>>>> 2.6.29,
>>>> and I have an external disk where I could backup to / boot from if the
>>>> corruption became a problem.
>>>>
>>>> These issues are keeping me from 2.6.29 so I'll gladly help where I
>>>> can,
>>>> if you can please provide me the patches and the .config settings that
>>>> may be required?
>>>>
>>>> Niel
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>>>>
>>> Any chance you could use bisect to narrow down the problem commit?
>>>
>>> http://kernel.org/pub/software/scm/git/docs/v1.4.4.4/howto/isolate-bugs-with-bisect.txt
>>>
>>>
>>>
>>> This should identify which patch caused your problems, if you have a
>>> known good starting point (such as 2.6.28).
>> I'm struggling with this - my good kernel is 2.6.28.9 and as far as I
>> can tell the closest thing good kernel I can tell git to use is 2.6.28
>> base itself. So now what happens is that resume entirely fails during
>> some of the bisects due to entirely other regressions that are present
>> in older and newer kernels than mine, so I can't test the real issue! :(
>
> "git help bisect" or "man git-bisect" has a wealth of information.
>
> Most notably, you can use "git bisect skip" if the current commit
> cannot be tested, and thus cannot be declared good or bad.
Thanks Jeff, still finding my way around git, it was not that clear to
me if there is a way to tell git that 2.6.28.9 was good, to me it looked
like the main kernel only consists of the RC and the final release, not
any subsequent patches?

Anyhow, Tejun's patch is holding up well apart from the glitch I
reported on yesterday - I guess it could have simply been part of the
debugging output Tejun included in the patch and not a real issue.

I haven't heard from him (yet),  but I wonder if you might know if the
results give enough of a clue for a patch that could be included in say
2.6.29.1?

Thanks!
Niel


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