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

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Date: Fri, 23 Feb 2024 12:04:01 +0800
From: yangxingui <yangxingui@...wei.com>
To: John Garry <john.g.garry@...cle.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] scsi: libsas: Fix disk not being scanned in after being
 removed

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?
as follow:
+++ b/drivers/scsi/libsas/sas_expander.c
@@ -1940,6 +1940,7 @@ static int sas_rediscover_dev(struct domain_device 
*dev, int phy_id,
         struct expander_device *ex = &dev->ex_dev;
         struct ex_phy *phy = &ex->ex_phy[phy_id];
         enum sas_device_type type = SAS_PHY_UNUSED;
+       struct smp_disc_resp *disc_resp;
         u8 sas_addr[SAS_ADDR_SIZE];
         char msg[80] = "";
         int res;
@@ -1951,33 +1952,41 @@ static int sas_rediscover_dev(struct 
domain_device *dev, int phy_id,
                  SAS_ADDR(dev->sas_addr), phy_id, msg);

         memset(sas_addr, 0, SAS_ADDR_SIZE);
-       res = sas_get_phy_attached_dev(dev, phy_id, sas_addr, &type);
+       disc_resp = alloc_smp_resp(DISCOVER_RESP_SIZE);
+       if (!disc_resp)
+               return -ENOMEM;
+       res = sas_get_phy_discover(dev, phy_id, disc_resp);
..
-               /*
-                * 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);
-               return res;
+		if (res == 0)
+               	sas_set_ex_phy(dev, phy_id, disc_resp);
+               goto out;

..

+out:
+	kfree(disc_resp);
+	return res;

Thanks.
Xingui