linux-kernel - Re: [PATCH v4] scsi: libsas: Fix the failure of adding phy with zero-address to port

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Date:   Mon, 4 Dec 2023 19:49:06 +0800
From:   yangxingui <yangxingui@...wei.com>
To:     John Garry <john.g.garry@...cle.com>, <yanaijie@...wei.com>,
        <jejb@...ux.ibm.com>, <martin.petersen@...cle.com>,
        <damien.lemoal@...nsource.wdc.com>
CC:     <linux-scsi@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <linuxarm@...wei.com>, <prime.zeng@...ilicon.com>,
        <kangfenglong@...wei.com>, <chenxiang66@...ilicon.com>
Subject: Re: [PATCH v4] scsi: libsas: Fix the failure of adding phy with
 zero-address to port

Hi, John

On 2023/12/1 17:22, John Garry wrote:
> On 30/11/2023 03:53, yangxingui wrote:
>>>>
>>>> For phy19, when the phy is attached and added to the parent wide 
>>>> port, the path is:
>>>> sas_rediscover()
>>>>      ->sas_discover_new()
>>>>          ->sas_ex_discover_devices()
>>>>              ->sas_ex_discover_dev()
>>>>                  -> sas_add_parent_port().
>>>
>>> ok, so then the change to set ex_phy->port = ex->parent_port looks 
>>> ok. Maybe we can put this in a helper with the sas_port_add_phy() 
>>> call, as it is duplicated in sas_ex_join_wide_port()
>>>
>>> Do we also need to set ex_phy->phy_state (like sas_ex_join_wide_port())?
>>
>> Well, okay, as follows?
>> +++ b/drivers/scsi/libsas/sas_expander.c
>> @@ -856,9 +856,7 @@ static bool sas_ex_join_wide_port(struct 
>> domain_device *parent, int phy_id)
>>
>>                  if (!memcmp(phy->attached_sas_addr, 
>> ephy->attached_sas_addr,
>>                              SAS_ADDR_SIZE) && ephy->port) {
>> -                       sas_port_add_phy(ephy->port, phy->phy);
>> -                       phy->port = ephy->port;
>> -                       phy->phy_state = PHY_DEVICE_DISCOVERED;
>> +                       sas_port_add_ex_phy(ephy->port, phy);
>>                          return true;
> 
> this looks ok. How about adding this helper and using it in a separate 
> change?
Okay, then I will update the version.
> 
>>                  }
>>          }
>> diff --git a/drivers/scsi/libsas/sas_internal.h 
>> b/drivers/scsi/libsas/sas_internal.h
>> index e860d5b19880..39ffa60a9a01 100644
>> --- a/drivers/scsi/libsas/sas_internal.h
>> +++ b/drivers/scsi/libsas/sas_internal.h
>> @@ -189,6 +189,13 @@ static inline void sas_phy_set_target(struct 
>> asd_sas_phy *p, struct domain_devic
>>          }
>>   }
>>
>> +static inline void sas_port_add_ex_phy(struct sas_port *port, struct 
>> ex_phy *ex_phy)
>> +{
>> +       sas_port_add_phy(port, ex_phy->phy);
>> +       ex_phy->port = port;
>> +       ex_phy->phy_state = PHY_DEVICE_DISCOVERED;
>> +}
> 
> I'd prefer sas_expander.c, but sas_add_parent_port() is here... having 
> said that, sas_add_parent_port() is only used in sas_expander.c
Okay, then I will update the version and move it to sas_expander.c .

> 
>> +
>>   static inline void sas_add_parent_port(struct domain_device *dev, 
>> int phy_id)
>>   {
>>          struct expander_device *ex = &dev->ex_dev;
>> @@ -201,8 +208,7 @@ static inline void sas_add_parent_port(struct 
>> domain_device *dev, int phy_id)
>>                  BUG_ON(sas_port_add(ex->parent_port));
>>                  sas_port_mark_backlink(ex->parent_port);
>>          }
>> -       sas_port_add_phy(ex->parent_port, ex_phy->phy);
>> +       sas_port_add_ex_phy(ex->parent_port, ex_phy);
>>   }
>>
>>>
>>>> And the path called when it is removed from parent wide port is:
>>>> sas_rediscover()
>>>>      ->sas_unregister_devs_sas_addr() // The sas address of phy19 
>>>> becomes 0. Since ex_phy->port is NULL, phy19 is not removed from the 
>>>> parent wide port's phy_list.
>>>>
>>>> For phy0, it is connected to a new sata device.
>>>> sas_rediscover()
>>>>      ->sas_discover_new()->sas_ex_phy_discover()
>>>>                              ->sas_ex_phy_discover_helper()
>>>>                                  ->sas_set_ex_phy() // The device 
>>>> type is stp. Since the linkrate is 5 and less than 1.5G, sas_address 
>>>> is set to 0.
>>>
>>> Then when we get the proper linkrate later, will we then rediscover 
>>> and set the proper SAS address? I am just wondering if this change is 
>>> really required?
>> Yes, but in fact it has not reached that stage yet. After setting the 
>> address to 0, it will continue to create a new port and try to add 
>> other phys with the same address as it to this new port.
> 
> creating a port for SAS address == 0 and adding phys seems incorrect, 
> right?
Yes. There are three possible ways to solve the problem of creating a 
port with a zero address:
1. Use the sas address obtained by querying the expander instead of the 
zero address.
2. Forbid the phy with an address of 0 to create a port.
3. When the rate is less than 1.5G, do not let it enter 
sas_ex_discover_end_dev().

Because when the device type is not empty, its SAS address is legal, and 
we are currently using the first one.
> 
>>
>>>
>>> BTW, Even with the change to set ex_phy->port = ex->parent_port, are 
>>> we still joining the host-attached expander phy (19) to a port with 
>>> SAS address == 0?
>> Yes, in order to avoid this situation, in the current patch, we will 
>> not force the SAS address to be set to 0 when the device type is not 
>> NULL, but will still use the address obtained after requesting the 
>> expander.
> 
> ok, let me check that again later today.
OK.

Thanks
Xingui