linux-kernel - Re: [PATCH] scsi: libsas: no need to join wide port again in sas_ex_discover

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Message-ID: <1860c624-1216-bb84-7091-d41a4d43f244@huawei.com>
Date:   Mon, 20 May 2019 11:54:51 +0100
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>,
        <hare@...e.com>, <dan.j.williams@...el.com>, <jthumshirn@...e.de>,
        <hch@....de>, <huangdaode@...ilicon.com>,
        <chenxiang66@...ilicon.com>, <miaoxie@...wei.com>,
        <zhaohongjiang@...wei.com>
Subject: Re: [PATCH] scsi: libsas: no need to join wide port again in
 sas_ex_discover_dev()

On 18/05/2019 10:40, Jason Yan wrote:
> Since we are processing events synchronously now, the second call of
> sas_ex_join_wide_port() in sas_ex_discover_dev() is not needed. There
> will be no races with other works in disco workqueue. So remove the
> second sas_ex_join_wide_port().
>
> I did not change the return value of 'res' to error when discover failed
> because we need to continue to discover other phys if one phy discover
> failed. So let's keep that logic as before and just add a debug log to
> detect the failure.
>
> Signed-off-by: Jason Yan <yanaijie@...wei.com>
> ---
>  drivers/scsi/libsas/sas_expander.c | 24 +++---------------------
>  1 file changed, 3 insertions(+), 21 deletions(-)
>
> diff --git a/drivers/scsi/libsas/sas_expander.c b/drivers/scsi/libsas/sas_expander.c
> index 83f2fd70ce76..8f90dd497dfe 100644
> --- a/drivers/scsi/libsas/sas_expander.c
> +++ b/drivers/scsi/libsas/sas_expander.c
> @@ -1116,27 +1116,9 @@ static int sas_ex_discover_dev(struct domain_device *dev, int phy_id)
>  		break;
>  	}
>
> -	if (child) {
> -		int i;
> -
> -		for (i = 0; i < ex->num_phys; i++) {
> -			if (ex->ex_phy[i].phy_state == PHY_VACANT ||
> -			    ex->ex_phy[i].phy_state == PHY_NOT_PRESENT)
> -				continue;
> -			/*
> -			 * Due to races, the phy might not get added to the
> -			 * wide port, so we add the phy to the wide port here.
> -			 */
> -			if (SAS_ADDR(ex->ex_phy[i].attached_sas_addr) ==
> -			    SAS_ADDR(child->sas_addr)) {
> -				ex->ex_phy[i].phy_state= PHY_DEVICE_DISCOVERED;
> -				if (sas_ex_join_wide_port(dev, i))
> -					pr_debug("Attaching ex phy%02d to wide port %016llx\n",
> -						 i, SAS_ADDR(ex->ex_phy[i].attached_sas_addr));
> -			}
> -		}
> -	}

This change looks ok.

> -
> +	if (!child)
> +		pr_debug("Ex %016llx phy%02d failed to discover\n",
> +			 SAS_ADDR(dev->sas_addr), phy_id);

nit:
/s/Ex/ex/

In case of "second fanout expander...", before this, we don't attempt to 
discover, and just disable the PHY. In that case, is the log proper?

And, if indeed proper, it would seem to merit a higher log level than 
debug, maybe notice is better.


>  	return res;
>  }
>
>