linux-kernel - Re: [PATCH] scsi: libsas: Fix disk not being scanned in after being removed

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Date: Fri, 23 Feb 2024 15:04:00 +0800
From: Jason Yan <yanaijie@...wei.com>
To: yangxingui <yangxingui@...wei.com>, John Garry <john.g.garry@...cle.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] scsi: libsas: Fix disk not being scanned in after being
 removed

On 2024/2/23 12:04, yangxingui wrote:
> Hi, John
> 
> On 2024/2/22 20:41, John Garry wrote:
>> On 21/02/2024 07:31, Xingui Yang wrote:
>>> As of commit d8649fc1c5e4 ("scsi: libsas: Do discovery on empty PHY to
>>> update PHY info"), do discovery will send a new SMP_DISCOVER and update
>>> phy->phy_change_count. We found that if the disk is reconnected and phy
>>> change_count changes at this time, the disk scanning process will not be
>>> triggered.
>>>
>>> So update the PHY info with the last query results.
>>>
>>> Fixes: d8649fc1c5e4 ("scsi: libsas: Do discovery on empty PHY to 
>>> update PHY info")
>>> Signed-off-by: Xingui Yang <yangxingui@...wei.com>
>>> ---
>>>   drivers/scsi/libsas/sas_expander.c | 9 ++++-----
>>>   1 file changed, 4 insertions(+), 5 deletions(-)
>>>
>>> diff --git a/drivers/scsi/libsas/sas_expander.c 
>>> b/drivers/scsi/libsas/sas_expander.c
>>> index a2204674b680..9563f5589948 100644
>>> --- a/drivers/scsi/libsas/sas_expander.c
>>> +++ b/drivers/scsi/libsas/sas_expander.c
>>> @@ -1681,6 +1681,10 @@ int sas_get_phy_attached_dev(struct 
>>> domain_device *dev, int phy_id,
>>>           if (*type == 0)
>>>               memset(sas_addr, 0, SAS_ADDR_SIZE);
>>>       }
>>> +
>>> +    if ((SAS_ADDR(sas_addr) == 0) || (res == -ECOMM))
>>> +        sas_set_ex_phy(dev, phy_id, disc_resp);
>>> +
>>>       kfree(disc_resp);
>>>       return res;
>>>   }
>>> @@ -1972,11 +1976,6 @@ static int sas_rediscover_dev(struct 
>>> domain_device *dev, int phy_id,
>>>       if ((SAS_ADDR(sas_addr) == 0) || (res == -ECOMM)) {
>>>           phy->phy_state = PHY_EMPTY;
>>>           sas_unregister_devs_sas_addr(dev, phy_id, last);
>>> -        /*
>>> -         * Even though the PHY is empty, for convenience we discover
>>> -         * the PHY to update the PHY info, like negotiated linkrate.
>>> -         */
>>> -        sas_ex_phy_discover(dev, phy_id);
>>
>> It would be nice to be able to call sas_set_ex_phy() here (instead of 
>> sas_get_phy_attached_dev()), but I assume that you can't do that as 
>> the disc_resp memory is not available.
>>
>> If we were to manually set the PHY info here instead, how would that 
>> look?
> Yes, I think it is indeed better to use sas_set_ex_phy, as you said, 
> disc_resp memory is not available. Maybe we can use sas_get_phy_discover 
> instead of sas_get_phy_attached_dev so we can use disc_resp?

Can we directly set phy->negotiated_linkrate = SAS_PHY_DISABLED here? 
For an empty PHY the other variables means nothing, so why bother get 
and update them?

Thanks,
Jason