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

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Message-ID: <f095aa1c-f233-40f9-ad0f-fcd8fe69a80d@oracle.com>
Date: Wed, 28 Feb 2024 18:13:08 +0000
From: John Garry <john.g.garry@...cle.com>
To: Xingui Yang <yangxingui@...wei.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

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))

It's odd to call sas_set_ex_phy() if we got res == -ECOMM. I mean, in 
this this case disc_resp is not filled in as the command did not 
execute, right? I know that is what the current code does, but it is 
strange.

> +		sas_set_ex_phy(dev, phy_id, disc_resp);

So can we just call this here when we know that the SMP command was 
executed properly?

Thanks,
John

> +
>   	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);
>   		return res;
>   	} else if (SAS_ADDR(sas_addr) == SAS_ADDR(phy->attached_sas_addr) &&
>   		   dev_type_flutter(type, phy->attached_dev_type)) {