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

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Date:   Fri, 1 Dec 2023 09:22:48 +0000
From:   John Garry <john.g.garry@...cle.com>
To:     yangxingui <yangxingui@...wei.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

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?

>                  }
>          }
> 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

> +
>   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?

> 
>>
>> 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.

Thanks,
John