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SubjectRe: [PATCH v2 4/7] scsi: libsas: split the replacement of sas disks in two steps
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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?

> 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 *);
>>
>
>
>
> .
>

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