Re: [PATCH v7 08/19] scsi: detect support for command duration limits

[Damien Le Moal <dlemoal@kernel.org>]

On 7/31/25 20:48, Diangang Li wrote:
> On Tue, Jul 22, 2025 at 06:37:50PM +0900, Damien Le Moal wrote:
>> On 7/22/25 6:32 PM, Friedrich Weber wrote:
>>> On 14/07/2025 04:48, Damien Le Moal wrote:
>>>> On 7/10/25 5:41 PM, Friedrich Weber wrote:
>>>>> Thanks for looking into this, it is definitely a strange problem.
>>>>>
>>>>> Considering these drives don't support CDL anyway: Do you think it would
>>>>> be possible to provide an "escape hatch" to disable only the CDL checks
>>>>> (a module parameter?) so hotplug can work for the user again for their
>>>>> device? If I see correctly, disabling just the CDL checks is not
>>>>> possible (without recompiling the kernel) -- scsi_mod.dev_flags can be
>>>>> used to disable RSOC, but I guess that has other unintended consequences
>>>>> too, so a more "targeted" escape hatch would be nice.
>>>>
>>>> Could you test the attached patch ? That should solve the issue.
>>>>
>>>
>>> Thanks for the patch! The user tested it on top of a 6.15.6 kernel and
>>> with the SAS3008 HBA, and indeed:
>>>
>>> - under 6.15.6, hotplug fails with the log messages mentioned in my
>>> first message,
>>> - with your patch on top, hotplug works again.
>>
>> OK. Will post a proper patch then (tomorrow).
>> Thanks for testing.
>>
> 
> Hi Damien,
> 
> Are you planning to post a formal patch to upstream?

I initially thought that the issue was due to some problem with the HBA SAT
(SCSI to ATA translation). However, the drives that trigger the issue are SAS
drives, so there is no command translation and it is much less likely that the
issue is related to the HBA. So I am relunctant to take a big hammer and disable
CDL for mpt3sas for SAS drive. HBAs driven by that driver do *not* support CDL
for ATA, so disabling CDL would not be an issue for SATA disks. But there is no
good reasons to disable CDL for SAS drives.

This is being handled as a drive issue now, off-list.

-- 
Damien Le Moal
Western Digital Research