linux-kernel - Re: [PATCH RFC v3 16/22] ata: libata-scsi: Allocate sdev early in port probe

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Message-ID: <6c0a4a75-786a-c946-57f2-c511bd765bcc@opensource.wdc.com>
Date:   Thu, 27 Oct 2022 10:34:43 +0900
From:   Damien Le Moal <damien.lemoal@...nsource.wdc.com>
To:     John Garry <john.garry@...wei.com>, axboe@...nel.dk,
        jejb@...ux.ibm.com, martin.petersen@...cle.com,
        jinpu.wang@...ud.ionos.com, hare@...e.de, bvanassche@....org,
        hch@....de, ming.lei@...hat.com, niklas.cassel@....com
Cc:     linux-block@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-ide@...r.kernel.org, linux-scsi@...r.kernel.org,
        linuxarm@...wei.com
Subject: Re: [PATCH RFC v3 16/22] ata: libata-scsi: Allocate sdev early in
 port probe

On 10/25/22 19:18, John Garry wrote:
> Currently the per-ata device sdev is allocated as part of the scsi target
> scan, which is after the ata port probe.
> 
> However it is useful to have the sdev available in the port probe. As an
> example of an advantage, if the request queue is available in the probe
> (which it would be if the sdev is available), then it is possible to use
> a SCSI cmnd for ATA internal commands. The benefit of this is then we can
> put the ATA qc structure in the SCSI cmnd private data. It will also be
> useful if we want to send ATA internal commands as requests.
> 
> Export scsi_target_reap() so that it can be used to put the extra
> reference we get when allocating the sdev.
> 
> Signed-off-by: John Garry <john.garry@...wei.com>
> ---
>  drivers/ata/libata-eh.c   |  1 +
>  drivers/ata/libata-scsi.c | 23 +++++++++--------------
>  drivers/scsi/scsi_scan.c  |  1 +
>  3 files changed, 11 insertions(+), 14 deletions(-)
> 
> diff --git a/drivers/ata/libata-eh.c b/drivers/ata/libata-eh.c
> index 08e11bc312c2..1ed5b1b64792 100644
> --- a/drivers/ata/libata-eh.c
> +++ b/drivers/ata/libata-eh.c
> @@ -3446,6 +3446,7 @@ static int ata_eh_schedule_probe(struct ata_device *dev)
>  
>  	ata_eh_detach_dev(dev);
>  	ata_dev_init(dev);
> +	ata_scsi_setup_sdev(dev);
>  	ehc->did_probe_mask |= (1 << dev->devno);
>  	ehc->i.action |= ATA_EH_RESET;
>  	ehc->saved_xfer_mode[dev->devno] = 0;
> diff --git a/drivers/ata/libata-scsi.c b/drivers/ata/libata-scsi.c
> index efdba852e363..476e0ef4bd29 100644
> --- a/drivers/ata/libata-scsi.c
> +++ b/drivers/ata/libata-scsi.c
> @@ -1109,7 +1109,12 @@ int ata_scsi_dev_config(struct scsi_device *sdev, struct ata_device *dev)
>  	if (dev->flags & ATA_DFLAG_TRUSTED)
>  		sdev->security_supported = 1;
>  
> -	dev->sdev = sdev;
> +	/*
> +	 * Put extra reference which we get when allocating the starget
> +	 * initially
> +	 */
> +	scsi_target_reap(scsi_target(sdev));
> +
>  	return 0;
>  }
>  
> @@ -4289,26 +4294,16 @@ void ata_scsi_scan_host(struct ata_port *ap, int sync)
>   repeat:
>  	ata_for_each_link(link, ap, EDGE) {
>  		ata_for_each_dev(dev, link, ENABLED) {
> -			struct scsi_device *sdev;
> +			struct Scsi_Host *shost = ap->scsi_host;
>  			int channel = 0, id = 0;
>  
> -			if (dev->sdev)
> -				continue;
> -
>  			if (ata_is_host_link(link))
>  				id = dev->devno;
>  			else
>  				channel = link->pmp;
>  
> -			sdev = __scsi_add_device(ap->scsi_host, channel, id, 0,
> -						 NULL);
> -			if (!IS_ERR(sdev)) {
> -				dev->sdev = sdev;
> -				ata_scsi_assign_ofnode(dev, ap);

Is there something equivalent to what this function does inside
scsi_scan_target() ? I had a quick look but did not see anything...

> -				scsi_device_put(sdev);
> -			} else {
> -				dev->sdev = NULL;
> -			}
> +			scsi_scan_target(&shost->shost_gendev, channel, id,
> +					 0, SCSI_SCAN_INITIAL);
>  		}
>  	}
>  
> diff --git a/drivers/scsi/scsi_scan.c b/drivers/scsi/scsi_scan.c
> index b795c138f2c1..da7bc14b030c 100644
> --- a/drivers/scsi/scsi_scan.c
> +++ b/drivers/scsi/scsi_scan.c
> @@ -598,6 +598,7 @@ void scsi_target_reap(struct scsi_target *starget)
>  	BUG_ON(starget->state == STARGET_DEL);
>  	scsi_target_reap_ref_put(starget);
>  }
> +EXPORT_SYMBOL_GPL(scsi_target_reap);
>  
>  /**
>   * scsi_sanitize_inquiry_string - remove non-graphical chars from an

-- 
Damien Le Moal
Western Digital Research