linux-kernel - Re: [PATCH v4] scsi: libsas: Fix exp-attached end device cannot be scanned in again after probe failed

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Date: Wed, 19 Jun 2024 08:50:44 +0100
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 v4] scsi: libsas: Fix exp-attached end device cannot be
 scanned in again after probe failed

On 19/06/2024 04:28, Xingui Yang wrote:
> The expander phy will be treated as broadcast flutter in the next
> revalidation after the exp-attached end device probe failed, as follows:
> 
> [78779.654026] sas: broadcast received: 0
> [78779.654037] sas: REVALIDATING DOMAIN on port 0, pid:10
> [78779.654680] sas: ex 500e004aaaaaaa1f phy05 change count has changed
> [78779.662977] sas: ex 500e004aaaaaaa1f phy05 originated BROADCAST(CHANGE)
> [78779.662986] sas: ex 500e004aaaaaaa1f phy05 new device attached
> [78779.663079] sas: ex 500e004aaaaaaa1f phy05:U:8 attached: 500e004aaaaaaa05 (stp)
> [78779.693542] hisi_sas_v3_hw 0000:b4:02.0: dev[16:5] found
> [78779.701155] sas: done REVALIDATING DOMAIN on port 0, pid:10, res 0x0
> [78779.707864] sas: Enter sas_scsi_recover_host busy: 0 failed: 0
> ...
> [78835.161307] sas: --- Exit sas_scsi_recover_host: busy: 0 failed: 0 tries: 1
> [78835.171344] sas: sas_probe_sata: for exp-attached device 500e004aaaaaaa05 returned -19
> [78835.180879] hisi_sas_v3_hw 0000:b4:02.0: dev[16:5] is gone
> [78835.187487] sas: broadcast received: 0
> [78835.187504] sas: REVALIDATING DOMAIN on port 0, pid:10
> [78835.188263] sas: ex 500e004aaaaaaa1f phy05 change count has changed
> [78835.195870] sas: ex 500e004aaaaaaa1f phy05 originated BROADCAST(CHANGE)
> [78835.195875] sas: ex 500e004aaaaaaa1f rediscovering phy05
> [78835.196022] sas: ex 500e004aaaaaaa1f phy05:U:A attached: 500e004aaaaaaa05 (stp)
> [78835.196026] sas: ex 500e004aaaaaaa1f phy05 broadcast flutter
> [78835.197615] sas: done REVALIDATING DOMAIN on port 0, pid:10, res 0x0
> 
> The cause of the problem is that the related ex_phy's attached_sas_addr was
> not cleared after the end device probe failed, so reset it.
> 
> Signed-off-by: Xingui Yang <yangxingui@...wei.com>

Apart from a couple of comments, below:
Reviewed-by: John Garry <john.g.garry@...cle.com>

> ---
> Changes since v3:
> - Just manually clear the ex_phy's attached_sas_addr instead of calling
>    sas_unregister_devs_sas_addr() and deleting the port.
> - Update commit information.
> 
> Changes since v2:
> - Add a helper for calling sas_destruct_devices() and sas_destruct_ports(),
>    and put the new call at the end of sas_probe_devices() based on John's
>    suggestion.
> 
> Changes since v1:
> - Simplify the process of getting ex_phy id based on Jason's suggestion.
> - Update commit information.
> ---
>   drivers/scsi/libsas/sas_internal.h | 14 ++++++++++++++
>   1 file changed, 14 insertions(+)
> 
> diff --git a/drivers/scsi/libsas/sas_internal.h b/drivers/scsi/libsas/sas_internal.h
> index 85948963fb97..7c0931ccea23 100644
> --- a/drivers/scsi/libsas/sas_internal.h
> +++ b/drivers/scsi/libsas/sas_internal.h
> @@ -145,6 +145,20 @@ static inline void sas_fail_probe(struct domain_device *dev, const char *func, i
>   		func, dev->parent ? "exp-attached" :
>   		"direct-attached",
>   		SAS_ADDR(dev->sas_addr), err);
> +
> +	/* if the device probe failed, the expander phy attached address

please use standard comment format, i.e. /* goes on a line on its own

> +	 * need to be reset so that the phy will not be treated as flutter

/s/need to be reset/needs to be reset/

> +	 * in the next revalidation
> +	 */
> +	if (dev->parent && !dev_is_expander(dev->dev_type)) {
> +		struct domain_device *parent = dev->parent;
> +		struct expander_device *ex_dev = &parent->ex_dev;
> +		struct sas_phy *phy = dev->phy;
> +		struct ex_phy *ex_phy = &ex_dev->ex_phy[phy->number];

this could all be put on fewer lines, or even 1, like:

struct ex_phy *ex_phy = &dev->ex_dev.ex_phy[phy->number];

you could even add a helper, like:

static inline struct ex_phy *sas_expander_ex_phy(struct domain_device
  *parent, int phy_id)
  {
  struct expander_device *ex_dev = &parent->ex_dev;

  return &ex_dev->ex_phy[phy_id];
  }

However, I am not sure how helpful it will be, since we often require a 
struct expander_device pointer when we would be using that helper.


> +
> +		memset(ex_phy->attached_sas_addr, 0, SAS_ADDR_SIZE);
> +	}
> +
>   	sas_unregister_dev(dev->port, dev);
>   }
>