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

[yangxingui]

Hi, John

On 2023/11/29 20:54, John Garry wrote:
> On 28/11/2023 03:45, yangxingui wrote:
> > On 2023/11/28 3:28, John Garry wrote:
> > > On 24/11/2023 02:27, yangxingui wrote:
> > > > > We already do this in sas_ex_join_wide_port(), right?
> > > > No, If the addr of ex_phy matches dev->parent, 
> > > > sas_ex_join_wide_port() will not be called, but 
> > > > sas_add_parent_port() will be called  as follows:
> > > > static int sas_ex_discover_dev(struct domain_device *dev, int phy_id)
> > > > {
> > > >          struct expander_device *ex = &dev->ex_dev;
> > > >          struct ex_phy *ex_phy = &ex->ex_phy[phy_id];
> > > >          struct domain_device *child = NULL;
> > > >          int res = 0;
> > > >
> > > >      <...>
> > > >          /* Parent and domain coherency */
> > > >          if (!dev->parent && sas_phy_match_port_addr(dev->port, 
> > > > ex_phy)) {
> > > >                  sas_add_parent_port(dev, phy_id);
> > > >                  return 0;
> > > >          }
> > > >          if (dev->parent && sas_phy_match_dev_addr(dev->parent, 
> > > > ex_phy)) {
> > > >                  sas_add_parent_port(dev, phy_id);
> > > >                  if (ex_phy->routing_attr == TABLE_ROUTING)
> > > >                          sas_configure_phy(dev, phy_id, 
> > > > dev->port->sas_addr, 1);
> > > >                  return 0;
> > > >          }
> > > >      <...>
> > > > }
> > > >
> > > > > I am not saying that what we do now does not have a problem - I am 
> > > > > just trying to understand what currently happens
> > > >
> > > > ok, because ex_phy->port is not set when calling 
> > > > sas_add_parent_port(), when deleting phy from the parent wide port, 
> > > > it is not removed from the phy_list of the parent wide port as follows:
> > > > static void sas_unregister_devs_sas_addr(struct domain_device *parent,
> > > >                                           int phy_id, bool last)
> > > > {
> > > >      <...>
> > > >      // Since ex_phy->port is not set, this branch will not be enter
> > >
> > > But then how does this ever work? It is because we follow path 
> > > sas_rediscover_dev() -> sas_discover_new() -> 
> > > sas_ex_discover_devices() -> sas_ex_discover_dev() -> 
> > > sas_add_parent_port(), and not sas_rediscover_dev() -> 
> > > sas_discover_new() -> sas_ex_join_wide_port()? If so, is that because 
> > > ephy->sas_attached_phy == 0 in sas_discover_new() -> 
> > > sas_ex_join_wide_port() and it fails?
> > >
> > > BTW, about something mentioned earlier - adding the phy19 with SAS_ADDR 
> >
> > Yes,
> > 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;
                }
        }
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;
+}
+
 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.

> 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.


Thanks,
Xingui