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Subject: Re: [PATCH] scsi: libsas: Fix disk not being scanned in after being
 removed
To: yangxingui <yangxingui@huawei.com>, John Garry <john.g.garry@oracle.com>,
	<jejb@linux.ibm.com>, <martin.petersen@oracle.com>,
	<damien.lemoal@opensource.wdc.com>
CC: <linux-scsi@vger.kernel.org>, <linux-kernel@vger.kernel.org>,
	<linuxarm@huawei.com>, <prime.zeng@hisilicon.com>,
	<chenxiang66@hisilicon.com>, <kangfenglong@huawei.com>
References: <20240221073159.29408-1-yangxingui@huawei.com>
 <d765d2c5-3451-4519-a5e1-9e8f28dcd6b3@oracle.com>
 <cdf241a7-8504-5b87-2d18-d2a971f6ebb9@huawei.com>
 <8dc34f04-943b-26fd-01bc-34fb98803503@huawei.com>
 <b2ab5439-361b-4160-4e73-171026ecc486@huawei.com>
From: Jason Yan <yanaijie@huawei.com>
Message-ID: <8138ab55-1c43-8df1-dafd-95b16b7b3ce4@huawei.com>
Date: Tue, 27 Feb 2024 15:16:58 +0800
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On 2024/2/27 11:06, yangxingui wrote:
> Hi Jason,
> 
> On 2024/2/23 15:04, Jason Yan wrote:
>> 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@huawei.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?
> The value of the negotiated link rate has two possible values ​​in the 
> current processing branch: SAS_LINK_RATE_UNKNOWN and SAS_PHY_DISABLED, 
> and both come from disc_resp. If we do not use disc_resp, but set a 
> fixed value SAS_PHY_DISABLED for it, it may not be appropriate.

OK, makes sense.

> 
> Thanks,
> Xingui
> 
> .