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

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Date:   Wed, 30 Jan 2019 17:36:20 +0000
From:   John Garry <john.garry@...wei.com>
To:     Jason Yan <yanaijie@...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 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.

>
> 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;
>