Date:	Fri, 03 Apr 2009 16:09:14 -0400
From:	Jeff Garzik <jeff@...zik.org>
To:	Niel Lambrechts <niel.lambrechts@...il.com>
CC:	Tejun Heo <tj@...nel.org>,
	"linux.kernel" <linux-kernel@...r.kernel.org>
Subject: Re: 2.6.29 regression: ATA bus errors on resume

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.

	Jeff



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