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Subject: Re: [PATCH v2 4/7] scsi: libsas: split the replacement of sas disks
 in two steps
To:     Jason Yan <yanaijie@huawei.com>, <martin.petersen@oracle.com>,
        <jejb@linux.vnet.ibm.com>
References: <20190130082412.9357-1-yanaijie@huawei.com>
 <20190130082412.9357-5-yanaijie@huawei.com>
 <17908564-35f2-4c5d-e9e4-4fe109fae4cc@huawei.com>
 <5C5257AC.3040303@huawei.com>
CC:     <linux-scsi@vger.kernel.org>, <linux-kernel@vger.kernel.org>,
        <zhaohongjiang@huawei.com>, <hare@suse.com>,
        <dan.j.williams@intel.com>, <jthumshirn@suse.de>, <hch@lst.de>,
        <huangdaode@hisilicon.com>, <chenxiang66@hisilicon.com>,
        <xiexiuqi@huawei.com>, <tj@kernel.org>, <miaoxie@huawei.com>,
        Ewan Milne <emilne@redhat.com>, Tomas Henzl <thenzl@redhat.com>
From:   John Garry <john.garry@huawei.com>
Message-ID: <7ad77303-9960-5b8c-f26e-fc825ac57621@huawei.com>
Date:   Thu, 31 Jan 2019 10:29:17 +0000
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On 31/01/2019 02:04, Jason Yan wrote:
>
>
> On 2019/1/31 1:22, John Garry wrote:
>> On 30/01/2019 08:24, Jason Yan wrote:
>>> Now if a new device replaced a old device, the sas address will change.
>>
>> Hmmm... not if it's a SATA disk, which would have some same invented SAS
>> address.
>>
>
> Yes, it's only for a SAS disk.
>
>>> We unregister the old device and discover the new device in one
>>> revalidation process. But after we deferred the sas_port_delete(), the
>>> sas port is not deleted when we registering the new port and device.
>>> The sas port cannot be added because the name of the new port is the
>>> same as the old.
>>>
>>> Fix this by doing the replacement in two steps. The first revalidation
>>> only delete the old device and trigger a new revalidation. The second
>>> revalidation discover the new device. To keep the event processing
>>> synchronised to the original event,
>>
>> Did I originally suggest this? It seems to needlessly make the code more
>> complicated.
>>
>
> Yes, my first version was raise a new bcast event, and you said it's not
> synchronised to the original event.  Shall I get back to that approach?

Not sure. This patch seems to fix something closely related to that in 
"scsi: libsas: fix issue of swapping two sas disks", which I will check 
further.

EOM

>
>> we wrapped a loop and added a new
>>> parameter to see if we should revalidate again.
>>>
>>> Signed-off-by: Jason Yan <yanaijie@huawei.com>
>>> CC: chenxiang <chenxiang66@hisilicon.com>
>>> CC: John Garry <john.garry@huawei.com>
>>> CC: Johannes Thumshirn <jthumshirn@suse.de>
>>> CC: Ewan Milne <emilne@redhat.com>
>>> CC: Christoph Hellwig <hch@lst.de>
>>> CC: Tomas Henzl <thenzl@redhat.com>
>>> CC: Dan Williams <dan.j.williams@intel.com>
>>> CC: Hannes Reinecke <hare@suse.com>
>>> ---
>>>  drivers/scsi/libsas/sas_discover.c | 20 +++++++++++++++-----
>>>  drivers/scsi/libsas/sas_expander.c | 20 ++++++++++++++------
>>>  include/scsi/libsas.h              |  2 +-
>>>  3 files changed, 30 insertions(+), 12 deletions(-)
>>>
>>> diff --git a/drivers/scsi/libsas/sas_discover.c
>>> b/drivers/scsi/libsas/sas_discover.c
>>> index ffc571a12916..c825c89fbddd 100644
>>> --- a/drivers/scsi/libsas/sas_discover.c
>>> +++ b/drivers/scsi/libsas/sas_discover.c
>>> @@ -498,12 +498,10 @@ static void sas_discover_domain(struct
>>> work_struct *work)
>>>           task_pid_nr(current), error);
>>>  }
>>>
>>> -static void sas_revalidate_domain(struct work_struct *work)
>>> +static void sas_do_revalidate_domain(struct asd_sas_port *port, bool
>>> *retry)
>>>  {
>>> -    struct sas_discovery_event *ev = to_sas_discovery_event(work);
>>> -    struct asd_sas_port *port = ev->port;
>>> -    struct sas_ha_struct *ha = port->ha;
>>>      struct domain_device *ddev = port->port_dev;
>>> +    struct sas_ha_struct *ha = port->ha;
>>>
>>>      /* prevent revalidation from finding sata links in recovery */
>>>      mutex_lock(&ha->disco_mutex);
>>> @@ -520,7 +518,7 @@ static void sas_revalidate_domain(struct
>>> work_struct *work)
>>>
>>>      if (ddev && (ddev->dev_type == SAS_FANOUT_EXPANDER_DEVICE ||
>>>               ddev->dev_type == SAS_EDGE_EXPANDER_DEVICE))
>>> -        sas_ex_revalidate_domain(ddev);
>>> +        sas_ex_revalidate_domain(ddev, retry);
>>>
>>>      pr_debug("done REVALIDATING DOMAIN on port %d, pid:%d\n",
>>>           port->id, task_pid_nr(current));
>>> @@ -532,6 +530,18 @@ static void sas_revalidate_domain(struct
>>> work_struct *work)
>>>      sas_probe_devices(port);
>>>  }
>>>
>>> +static void sas_revalidate_domain(struct work_struct *work)
>>> +{
>>> +    struct sas_discovery_event *ev = to_sas_discovery_event(work);
>>> +    struct asd_sas_port *port = ev->port;
>>> +    bool retry;
>>> +
>>> +    do {
>>> +        retry = false;
>>> +        sas_do_revalidate_domain(port, &retry);
>>> +    } while (retry);
>>> +}
>>> +
>>>  /* ---------- Events ---------- */
>>>
>>>  static void sas_chain_work(struct sas_ha_struct *ha, struct sas_work
>>> *sw)
>>> diff --git a/drivers/scsi/libsas/sas_expander.c
>>> b/drivers/scsi/libsas/sas_expander.c
>>> index 5cd720f93f96..cdbf8d8a28bf 100644
>>> --- a/drivers/scsi/libsas/sas_expander.c
>>> +++ b/drivers/scsi/libsas/sas_expander.c
>>> @@ -1994,7 +1994,8 @@ static bool dev_type_flutter(enum
>>> sas_device_type new, enum sas_device_type old)
>>>      return false;
>>>  }
>>>
>>> -static int sas_rediscover_dev(struct domain_device *dev, int phy_id,
>>> bool last)
>>> +static int sas_unregister(struct domain_device *dev, int phy_id, bool
>>> last,
>>> +                  bool *retry)
>>>  {
>>>      struct expander_device *ex = &dev->ex_dev;
>>>      struct ex_phy *phy = &ex->ex_phy[phy_id];
>>> @@ -2045,7 +2046,12 @@ static int sas_rediscover_dev(struct
>>> domain_device *dev, int phy_id, bool last)
>>>          SAS_ADDR(phy->attached_sas_addr));
>>>      sas_unregister_devs_sas_addr(dev, phy_id, last);
>>>
>>> -    return sas_discover_new(dev, phy_id);
>>> +    /* force the next revalidation find this phy and bring it up */
>>> +    phy->phy_change_count = -1;
>>> +    ex->ex_change_count = -1;
>>> +    *retry = true;
>>
>> Ohh, sorry to say, but that's a real hack :)
>>
>
> This is the way sas_resume_port() already in use.
>
>> Could we just add a flag for the expander PHY to force a discovery
>> instead of this?
>>
>
> of course we can add a flag instead of this, but I don't think it worth
> to do this. We have to change the logic of sas_find_bcast_dev() and
> sas_find_bcast_phy() to achieve this. Or we have to add a new function
> to find out which PHY's flag is set.
>
>> I assume that you need to do this as the expander PHY change count will
>> not be modified for the next revalidation (so no discovery on that PHY).
>>
>
> To save one instruction(assign), we have to add two(check and assign)?
> And how to predict if the PHY change count will be modified or not?
> It's unnessesary to do this.
>
>>> +
>>> +    return 0;
>>>  }
>>>
>>>  /**
>>> @@ -2062,7 +2068,8 @@ static int sas_rediscover_dev(struct
>>> domain_device *dev, int phy_id, bool last)
>>>   * first phy,for other phys in this port, we add it to the port to
>>>   * forming the wide-port.
>>>   */
>>> -static void sas_rediscover(struct domain_device *dev, const int phy_id)
>>> +static void sas_rediscover(struct domain_device *dev, const int phy_id,
>>> +               bool *retry)
>>>  {
>>>      struct expander_device *ex = &dev->ex_dev;
>>>      struct ex_phy *changed_phy = &ex->ex_phy[phy_id];
>>> @@ -2087,7 +2094,7 @@ static void sas_rediscover(struct domain_device
>>> *dev, const int phy_id)
>>>                  break;
>>>              }
>>>          }
>>> -        res = sas_rediscover_dev(dev, phy_id, last);
>>> +        res = sas_unregister(dev, phy_id, last, retry);
>>>      } else
>>>          res = sas_discover_new(dev, phy_id);
>>>
>>> @@ -2098,13 +2105,14 @@ static void sas_rediscover(struct
>>> domain_device *dev, const int phy_id)
>>>  /**
>>>   * sas_ex_revalidate_domain - revalidate the domain
>>>   * @port_dev: port domain device.
>>> + * @retry: do we need to revalidate again
>>>   *
>>>   * NOTE: this process _must_ quit (return) as soon as any connection
>>>   * errors are encountered.  Connection recovery is done elsewhere.
>>>   * Discover process only interrogates devices in order to discover the
>>>   * domain.
>>>   */
>>> -void sas_ex_revalidate_domain(struct domain_device *port_dev)
>>> +void sas_ex_revalidate_domain(struct domain_device *port_dev, bool
>>> *retry)
>>>  {
>>>      int res;
>>>      struct domain_device *dev = NULL;
>>> @@ -2119,7 +2127,7 @@ void sas_ex_revalidate_domain(struct
>>> domain_device *port_dev)
>>>              res = sas_find_bcast_phy(dev, &phy_id, i, true);
>>>              if (phy_id == -1)
>>>                  break;
>>> -            sas_rediscover(dev, phy_id);
>>> +            sas_rediscover(dev, phy_id, retry);
>>>              i = phy_id + 1;
>>>          } while (i < ex->num_phys);
>>>      }
>>> diff --git a/include/scsi/libsas.h b/include/scsi/libsas.h
>>> index e557bcb0c266..deb75765e555 100644
>>> --- a/include/scsi/libsas.h
>>> +++ b/include/scsi/libsas.h
>>> @@ -692,7 +692,7 @@ int  sas_discover_root_expander(struct
>>> domain_device *);
>>>
>>>  void sas_init_ex_attr(void);
>>>
>>> -void sas_ex_revalidate_domain(struct domain_device *);
>>> +void sas_ex_revalidate_domain(struct domain_device *port_dev, bool
>>> *retry);
>>>
>>>  void sas_unregister_domain_devices(struct asd_sas_port *port, int
>>> gone);
>>>  void sas_init_disc(struct sas_discovery *disc, struct asd_sas_port *);
>>>
>>
>>
>>
>> .
>>
>
>
> .
>