linux-kernel - Re: [PATCH v2] ata: libata-scsi: Fix get identity data failed

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Date:   Fri, 5 May 2023 17:17:25 +0900
From:   Damien Le Moal <dlemoal@...nel.org>
To:     Xingui Yang <yangxingui@...wei.com>, jejb@...ux.ibm.com,
        martin.petersen@...cle.com, john.g.garry@...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,
        kangfenglong@...wei.com
Subject: Re: [PATCH v2] ata: libata-scsi: Fix get identity data failed

On 2023/05/05 11:57, Xingui Yang wrote:
> The function ata_get_identity() uses the helper ata_scsi_find_dev() to get
> the ata_device structure of a scsi device. However, when the ata device is
> managed by libsas, ata_scsi_find_dev() returns NULL, turning
> ata_get_identity() into a nop and always returns -ENOMSG.

What do you do to hit the issue ? A while back for me it was the queue depth
setting causing problems. As Garry mentioned, this led to patch 141f3d6256e5
("ata: libata-sata: Fix device queue depth control").

> 
> Fix this by checking whether ATA_FLAG_SAS_HOST is set for ap->flags in
> ata_scsi_find_dev(), as the flag is only used in libsas. If
> ATA_FLAG_SAS_HOST is set, use sas_to_ata_dev() to find associated ATA
> device.
> 
> Signed-off-by: Xingui Yang <yangxingui@...wei.com>
> ---
> Changes to v1 
> - Let ata_scsi_find_dev() return the correct value and don't keep replacing
> calls to ata_scsi_find_dev().
> 
>  drivers/ata/libata-scsi.c | 12 ++++++++++--
>  drivers/ata/libata.h      |  2 +-
>  2 files changed, 11 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/ata/libata-scsi.c b/drivers/ata/libata-scsi.c
> index 7bb12deab70c..aa580ea341fa 100644
> --- a/drivers/ata/libata-scsi.c
> +++ b/drivers/ata/libata-scsi.c
> @@ -26,6 +26,7 @@
>  #include <scsi/scsi_device.h>
>  #include <scsi/scsi_tcq.h>
>  #include <scsi/scsi_transport.h>
> +#include <scsi/libsas.h>
>  #include <linux/libata.h>
>  #include <linux/hdreg.h>
>  #include <linux/uaccess.h>
> @@ -2745,10 +2746,17 @@ static struct ata_device *__ata_scsi_find_dev(struct ata_port *ap,
>   *	Associated ATA device, or %NULL if not found.
>   */
>  struct ata_device *
> -ata_scsi_find_dev(struct ata_port *ap, const struct scsi_device *scsidev)

Why drop the const ?

> +ata_scsi_find_dev(struct ata_port *ap, struct scsi_device *scsidev)
>  {
> -	struct ata_device *dev = __ata_scsi_find_dev(ap, scsidev);
> +	struct ata_device *dev;
> +
> +	if (ap->flags & ATA_FLAG_SAS_HOST) {
> +		struct domain_device *ddev = sdev_to_domain_dev(scsidev);
> +
> +		return sas_to_ata_dev(ddev);

Do you really need the ddev variable ? Also, this really should be a libsas
helper. I beleive this pattern is repeated in several places in libsas, so that
would nicely clean things up.

> +	}
>  
> +	dev = __ata_scsi_find_dev(ap, scsidev);
>  	if (unlikely(!dev || !ata_dev_enabled(dev)))
>  		return NULL;
>  
> diff --git a/drivers/ata/libata.h b/drivers/ata/libata.h
> index 926d0d33cd29..6d66f46da064 100644
> --- a/drivers/ata/libata.h
> +++ b/drivers/ata/libata.h
> @@ -109,7 +109,7 @@ static inline void ata_acpi_bind_dev(struct ata_device *dev) {}
>  
>  /* libata-scsi.c */
>  extern struct ata_device *ata_scsi_find_dev(struct ata_port *ap,
> -					    const struct scsi_device *scsidev);
> +					    struct scsi_device *scsidev);
>  extern int ata_scsi_add_hosts(struct ata_host *host,
>  			      const struct scsi_host_template *sht);
>  extern void ata_scsi_scan_host(struct ata_port *ap, int sync);

-- 
Damien Le Moal
Western Digital Research