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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>
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: <17908564-35f2-4c5d-e9e4-4fe109fae4cc@huawei.com>
Date:   Wed, 30 Jan 2019 17:22:47 +0000
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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.

> 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.

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 :)

Could we just add a flag for the expander PHY to force a discovery 
instead of this?

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).

> +
> +	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 *);
>