Date: Tue, 18 Jun 2024 13:08:53 +0100
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,
        chenxiang66@...ilicon.com, kangfenglong@...wei.com
Subject: Re: [PATCH v3] scsi: libsas: Fix exp-attached end device cannot be
 scanned in again after probe failed

On 18/06/2024 12:45, yangxingui wrote:
> Hi, John,
> 
> Thanks for your reply.
> 
> On 2024/6/18 16:55, John Garry wrote:
>> On 13/06/2024 13:23, Xingui Yang wrote:
>>
>> Sorry for delay in responding and asking further questions.
> It doesn't matter.
>>
>>> We found that it is judged as broadcast flutter when the exp-attached 
>>> end
>>> device reconnects after probe failed, as follows:
>>>
>>> [78779.654026] sas: broadcast received: 0
>>> [78779.654037] sas: REVALIDATING DOMAIN on port 0, pid:10
>>> [78779.654680] sas: ex 500e004aaaaaaa1f phy05 change count has changed
>>> [78779.662977] sas: ex 500e004aaaaaaa1f phy05 originated 
>>> BROADCAST(CHANGE)
>>> [78779.662986] sas: ex 500e004aaaaaaa1f phy05 new device attached
>>> [78779.663079] sas: ex 500e004aaaaaaa1f phy05:U:8 attached: 
>>> 500e004aaaaaaa05 (stp)
>>> [78779.693542] hisi_sas_v3_hw 0000:b4:02.0: dev[16:5] found
>>> [78779.701155] sas: done REVALIDATING DOMAIN on port 0, pid:10, res 0x0
>>> [78779.707864] sas: Enter sas_scsi_recover_host busy: 0 failed: 0
>>> ...
>>> [78835.161307] sas: --- Exit sas_scsi_recover_host: busy: 0 failed: 0 
>>> tries: 1
>>> [78835.171344] sas: sas_probe_sata: for exp-attached device 
>>> 500e004aaaaaaa05 returned -19
>>> [78835.180879] hisi_sas_v3_hw 0000:b4:02.0: dev[16:5] is gone
>>> [78835.187487] sas: broadcast received: 0
>>> [78835.187504] sas: REVALIDATING DOMAIN on port 0, pid:10
>>> [78835.188263] sas: ex 500e004aaaaaaa1f phy05 change count has changed
>>> [78835.195870] sas: ex 500e004aaaaaaa1f phy05 originated 
>>> BROADCAST(CHANGE)
>>> [78835.195875] sas: ex 500e004aaaaaaa1f rediscovering phy05
>>> [78835.196022] sas: ex 500e004aaaaaaa1f phy05:U:A attached: 
>>> 500e004aaaaaaa05 (stp)
>>> [78835.196026] sas: ex 500e004aaaaaaa1f phy05 broadcast flutter
>>> [78835.197615] sas: done REVALIDATING DOMAIN on port 0, pid:10, res 0x0
>>>
>>> The cause of the problem is that the related ex_phy's 
>>> attached_sas_addr was
>>> not cleared after the end device probe failed. In order to solve the 
>>> above
>>> problem, a function sas_ex_unregister_end_dev() is defined to clear the
>>> ex_phy information and unregister the end device after the 
>>> exp-attached end
>>> device probe failed.
>>
>> Can you just manually clear the ex_phy's attached_sas_addr at the 
>> appropiate point (along with calling sas_unregister_dev())? It seems 
>> that we are using heavy-handed approach in calling 
>> sas_unregister_devs_sas_addr(), which does the clearing and much more.
> 
> I just tried it and it worked. If we only clear ex_phy's 
> attached_sas_addr, there is no need to call sas_destruct_ports(). We are 
> currently using sas_unregister_devs_sas_addr() which will add the port 
> to sas_port_del_list, so we need to call sas_destruct_ports() separately 
> to delete the port.
> 
> Should we also delete the port after the devices probe failed?

I'm not sure. Please check it.

sas_fail_probe() would still call sas_unregister_dev(), as required.

And you said that the sas_fail_probe() probe call would be asynchronous 
to sas_revalidate_domainin(). I actually expected you to have the new 
call to sas_destruct_ports() at the top of sas_revalidate_domainin(), 
like v2, but it is in sas_probe_devices().

Anyway, please check whether you require this additional call to delete 
the port.

> 
> Maybe I can update another version and only clear ex_phy's 
> attached_sas_addr based on your suggestions.
>>
>>>
>>> As devices may probe failed after done REVALIDATING DOMAIN when call
>>> sas_probe_devices(). Then after its port is added to the 
>>> sas_port_del_list,
>>> the port will not be deleted until the end of the next REVALIDATING 
>>> DOMAIN
>>> and sas_destruct_ports() is called. A warning about creating a duplicate
>>> port will occur in the new REVALIDATING DOMAIN when the end device
>>> reconnects. Therefore, the previous destroy_list and sas_port_del_list
>>> should be handled after devices probe failed.
>>>
>>> Signed-off-by: Xingui Yang <yangxingui@...wei.com>
>>> ---
>>> Changes since v2:
>>> - Add a helper for calling sas_destruct_devices() and 
>>> sas_destruct_ports(),
>>>    and put the new call at the end of sas_probe_devices() based on 
>>> John's
>>>    suggestion.
>>>
>>> Changes since v1:
>>> - Simplify the process of getting ex_phy id based on Jason's suggestion.
>>> - Update commit information.
>>> ---
>>>   drivers/scsi/libsas/sas_discover.c | 32 +++++++++++++++++++-----------
>>>   drivers/scsi/libsas/sas_expander.c |  8 ++++++++
>>>   drivers/scsi/libsas/sas_internal.h |  6 +++++-
>>>   3 files changed, 33 insertions(+), 13 deletions(-)
>>>
>>> diff --git a/drivers/scsi/libsas/sas_discover.c 
>>> b/drivers/scsi/libsas/sas_discover.c
>>> index 8fb7c41c0962..8c517e47d2b9 100644
>>> --- a/drivers/scsi/libsas/sas_discover.c
>>> +++ b/drivers/scsi/libsas/sas_discover.c
>>> @@ -17,6 +17,22 @@
>>>   #include <scsi/sas_ata.h>
>>>   #include "scsi_sas_internal.h"
>>> +static void sas_destruct_ports(struct asd_sas_port *port)
>>> +{
>>> +    struct sas_port *sas_port, *p;
>>> +
>>> +    list_for_each_entry_safe(sas_port, p, &port->sas_port_del_list, 
>>> del_list) {
>>> +        list_del_init(&sas_port->del_list);
>>> +        sas_port_delete(sas_port);
>>> +    }
>>> +}
>>> +
>>> +static void sas_destruct_devices_and_ports(struct asd_sas_port *port)
>>
>> "and" in a function name never sounds right.
>>
>> Can you just call sas_destruct_port(), as it takes a port arg? Maybe 
>> rename sas_destruct_ports() to sas_delete_ports(), as it does "delete" 
>> - this may avoid some confusion in names.
> As described above, if we only clear ex_phy's attached_sas_addr, we do 
> not need to call sas_destruct_ports().

Thanks,
John

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