linux-kernel - Re: [PATCH v2 6/7] scsi: libsas: reset the phy address if discover failed

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Date:   Thu, 31 Jan 2019 10:13:08 +0800
From:   Jason Yan <yanaijie@...wei.com>
To:     John Garry <john.garry@...wei.com>, <martin.petersen@...cle.com>,
        <jejb@...ux.vnet.ibm.com>
CC:     <linux-scsi@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <zhaohongjiang@...wei.com>, <hare@...e.com>,
        <dan.j.williams@...el.com>, <jthumshirn@...e.de>, <hch@....de>,
        <huangdaode@...ilicon.com>, <chenxiang66@...ilicon.com>,
        <xiexiuqi@...wei.com>, <tj@...nel.org>, <miaoxie@...wei.com>,
        Xiaofei Tan <tanxiaofei@...wei.com>,
        Ewan Milne <emilne@...hat.com>, Tomas Henzl <thenzl@...hat.com>
Subject: Re: [PATCH v2 6/7] scsi: libsas: reset the phy address if discover
 failed



On 2019/1/31 1:36, John Garry wrote:
> On 30/01/2019 08:24, Jason Yan wrote:
>> When we failed to discover the device, the phy address is still kept
>> in ex_phy. So when the next time we revalidate this phy the
>> address and device type is the same, it will be considered as flutter
>> and will not be discovered again. So the device will not be brought up.
>>
>> Fix this by reset the phy address to the initial value. Then
>> in the next revalidation the device will be discovered agian.
>
> Why fail to discover the device? I wonder in which scenario you have
> seen this, such that it is worth rediscovery.
>

The test guys have seen this for several times, especially after LLDD 
changed the logic of lldd_dev_found and may return error now.


>>
>> Tested-by: Chen Liangfei <chenliangfei1@...wei.com>
>> Signed-off-by: Jason Yan <yanaijie@...wei.com>
>> CC: Xiaofei Tan <tanxiaofei@...wei.com>
>> CC: John Garry <john.garry@...wei.com>
>> CC: Johannes Thumshirn <jthumshirn@...e.de>
>> CC: Ewan Milne <emilne@...hat.com>
>> CC: Christoph Hellwig <hch@....de>
>> CC: Tomas Henzl <thenzl@...hat.com>
>> CC: Dan Williams <dan.j.williams@...el.com>
>> CC: Hannes Reinecke <hare@...e.com>
>> ---
>>  drivers/scsi/libsas/sas_expander.c | 7 +++++++
>>  1 file changed, 7 insertions(+)
>>
>> diff --git a/drivers/scsi/libsas/sas_expander.c
>> b/drivers/scsi/libsas/sas_expander.c
>> index 6e56ebdc2148..e781941a7088 100644
>> --- a/drivers/scsi/libsas/sas_expander.c
>> +++ b/drivers/scsi/libsas/sas_expander.c
>> @@ -1100,6 +1100,13 @@ static int sas_ex_discover_dev(struct
>> domain_device *dev, int phy_id)
>>                           i, SAS_ADDR(ex->ex_phy[i].attached_sas_addr));
>>              }
>>          }
>> +    } else {
>> +        /* if we failed to discover this device, we have to
>> +         * reset the expander phy attached address so that we
>> +         * will not treat the phy as flutter in the next
>> +         * revalidation
>> +         */
>> +        memset(ex_phy->attached_sas_addr, 0, SAS_ADDR_SIZE);
>>      }
>>
>>      return res;
>>
>
>
>
> .
>