Re: Issue in sas_ex_discover_dev() for multiple level of SAS expanders in a domain

[Jason Yan <yanaijie@huawei.com>]

On 2024/5/8 16:29, Li, Eric (Honggang) wrote:
>> -----Original Message-----
>> From: John Garry <john.g.garry@oracle.com>
>> Sent: Wednesday, May 8, 2024 3:48 PM
>> To: Li, Eric (Honggang) <Eric.H.Li@Dell.com>; Jason Yan <yanaijie@huawei.com>;
>> james.bottomley@hansenpartnership.com; Martin K . Petersen <martin.petersen@oracle.com>
>> Cc: linux-scsi@vger.kernel.org
>> Subject: Re: Issue in sas_ex_discover_dev() for multiple level of SAS expanders in a domain
>>
>>
>> [EXTERNAL EMAIL]
>>
>> On 08/05/2024 01:59, Li, Eric (Honggang) wrote:
>>>>> Call to sas_ex_join_wide_port() makes the rest PHYs associated with
>>>>> that existing port
>>>> (making it become wideport) and set up sysfs between the PHY and
>>>> port. > Set PHY_STATE_DISCOVERED would make the rest PHYs not being
>>>> scanned/discovered again (as this wide port is already scanned).
>>>>
>>>> If you can just confirm that re-adding the code to set phy_state =
>>>> DISCOVERED is good enough to see the SAS disks again, then this can
>>>> be further discussed. >>
>>> OK. I will work on that and keep you updated.
>>
>> I expect a flow like this for scanning of the downstream expander:
>>
>> sas_discover_new(struct domain_device *dev [upstream expander], int
>> phy_id_a) -> sas_ex_discover_devices(single = -1) ->
>> sas_ex_discover_dev(phy_id_b) for each phy in @dev non-vacant and non-discovered ->
>> sas_ex_discover_expander( [downstream expander]) for first phy scanned which belongs to
>> downstream expander.
>>
>> And following that we have continue to scan phys in sas_ex_discover_devices(single = -1) ->
>> sas_ex_discover_dev(phy_id_b) ->
>> sas_ex_join_wide_port() ->  for each non-vacant and non-discovered phy in phy_id_b which
>> matches that downstream expander.
>>
>> Can you see why this does not actually work/occur?
>>
> 
> before calling sas_ex_join_wide_port(), sas_dev_present_in_domain() finds the attached_sas_address of PHY (phy_id_b) is already in the domain of that root port, and then disable all PHYs to that downstream expander (in sas_ex_disable_port(dev, attached_sas_addr))
> Therefore, I think we need to switch the order of function call to sas_ex_join_wide_port() and sas_dev_present_in_domain().

If this is true then all cascaded expanders will have this issue, I 
wonder why the test guys have not report it until now.

Thanks,
Jason

祝一切顺利

>