linux-kernel - Re: [PATCH RFC v3 1/7] ata: libata-scsi: Add ata_scsi_queue

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Date:   Thu, 27 Oct 2022 10:42:41 +0900
From:   Damien Le Moal <damien.lemoal@...nsource.wdc.com>
To:     John Garry <john.garry@...wei.com>, jejb@...ux.ibm.com,
        martin.petersen@...cle.com, hare@...e.de, bvanassche@....org,
        hch@....de, ming.lei@...hat.com, niklas.cassel@....com
Cc:     axboe@...nel.dk, jinpu.wang@...ud.ionos.com,
        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 1/7] ata: libata-scsi: Add
 ata_scsi_queue_internal()

On 10/25/22 19:32, John Garry wrote:
> Add a function to handle queued ATA internal SCSI cmnds - does much the
> same as ata_exec_internal_sg() does (which will be fixed up later to
> actually queue internal cmnds through this function).
> 
> Signed-off-by: John Garry <john.garry@...wei.com>
> ---
>  drivers/ata/libata-sata.c |  3 +++
>  drivers/ata/libata-scsi.c | 43 +++++++++++++++++++++++++++++++++++++++
>  drivers/ata/libata.h      |  3 ++-
>  include/linux/libata.h    |  6 ++++++
>  4 files changed, 54 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/ata/libata-sata.c b/drivers/ata/libata-sata.c
> index b6806d41a8c5..e8b828c56542 100644
> --- a/drivers/ata/libata-sata.c
> +++ b/drivers/ata/libata-sata.c
> @@ -1258,6 +1258,9 @@ int ata_sas_queuecmd(struct scsi_cmnd *cmd, struct ata_port *ap)
>  {
>  	int rc = 0;
>  
> +	if (blk_mq_is_reserved_rq(scsi_cmd_to_rq(cmd)))
> +		return ata_scsi_queue_internal(cmd, ap->link.device);
> +
>  	if (likely(ata_dev_enabled(ap->link.device)))
>  		rc = __ata_scsi_queuecmd(cmd, ap->link.device);
>  	else {
> diff --git a/drivers/ata/libata-scsi.c b/drivers/ata/libata-scsi.c
> index 476e0ef4bd29..30d7c90b0c35 100644
> --- a/drivers/ata/libata-scsi.c
> +++ b/drivers/ata/libata-scsi.c
> @@ -3965,6 +3965,49 @@ static inline ata_xlat_func_t ata_get_xlat_func(struct ata_device *dev, u8 cmd)
>  	return NULL;
>  }
>  
> +unsigned int ata_scsi_queue_internal(struct scsi_cmnd *scmd,
> +				     struct ata_device *dev)
> +{
> +	struct ata_link *link = dev->link;
> +	struct ata_port *ap = link->ap;
> +	struct ata_queued_cmd *qc;
> +
> +	/* no internal command while frozen */
> +	if (ap->pflags & ATA_PFLAG_FROZEN)
> +		goto did_err;
> +
> +	/* initialize internal qc */
> +	qc = __ata_qc_from_tag(ap, ATA_TAG_INTERNAL);
> +	link->preempted_tag = link->active_tag;
> +	link->preempted_sactive = link->sactive;
> +	ap->preempted_qc_active = ap->qc_active;
> +	ap->preempted_nr_active_links = ap->nr_active_links;
> +	link->active_tag = ATA_TAG_POISON;
> +	link->sactive = 0;
> +	ap->qc_active = 0;
> +	ap->nr_active_links = 0;
> +
> +	if (qc->dma_dir != DMA_NONE) {
> +		int n_elem;
> +
> +		n_elem = 1;
> +		qc->n_elem = n_elem;
> +		qc->sg = scsi_sglist(scmd);
> +		qc->nbytes = qc->sg->length;
> +		ata_sg_init(qc, qc->sg, n_elem);
> +	}
> +
> +	scmd->submitter = SUBMITTED_BY_BLOCK_LAYER;
> +
> +	ata_qc_issue(qc);

Arg, no ! This potentially mixes NCQ and non-NCQ commands, which is
forbidden by ATA spec. You need to use something like:

	if (ap->ops->qc_defer) {
		if ((rc = ap->ops->qc_defer(qc)))
			goto defer;
	}

	ata_qc_issue(qc);

which is done in __ata_scsi_queuecmd() -> ata_scsi_translate()

Unless you guarantee that ata_scsi_queue_internal() is always called
from libata EH context ?

> +
> +	return 0;
> +did_err:
> +	scmd->result = (DID_ERROR << 16);
> +	scsi_done(scmd);
> +	return 0;
> +}
> +
>  int __ata_scsi_queuecmd(struct scsi_cmnd *scmd, struct ata_device *dev)
>  {
>  	u8 scsi_op = scmd->cmnd[0];
> diff --git a/drivers/ata/libata.h b/drivers/ata/libata.h
> index 0c2df1e60768..15cd1cd618b8 100644
> --- a/drivers/ata/libata.h
> +++ b/drivers/ata/libata.h
> @@ -82,7 +82,6 @@ extern int ata_port_probe(struct ata_port *ap);
>  extern void __ata_port_probe(struct ata_port *ap);
>  extern unsigned int ata_read_log_page(struct ata_device *dev, u8 log,
>  				      u8 page, void *buf, unsigned int sectors);
> -
>  #define to_ata_port(d) container_of(d, struct ata_port, tdev)
>  
>  /* libata-acpi.c */
> @@ -130,6 +129,8 @@ extern int ata_scsi_user_scan(struct Scsi_Host *shost, unsigned int channel,
>  void ata_scsi_sdev_config(struct scsi_device *sdev);
>  int ata_scsi_dev_config(struct scsi_device *sdev, struct ata_device *dev);
>  int __ata_scsi_queuecmd(struct scsi_cmnd *scmd, struct ata_device *dev);
> +unsigned int ata_scsi_queue_internal(struct scsi_cmnd *scmd,
> +				     struct ata_device *dev);
>  
>  /* libata-eh.c */
>  extern unsigned int ata_internal_cmd_timeout(struct ata_device *dev, u8 cmd);
> diff --git a/include/linux/libata.h b/include/linux/libata.h
> index 827d5838cd23..8938b584520f 100644
> --- a/include/linux/libata.h
> +++ b/include/linux/libata.h
> @@ -764,7 +764,9 @@ struct ata_link {
>  
>  	struct device		tdev;
>  	unsigned int		active_tag;	/* active tag on this link */
> +	unsigned int		preempted_tag;
>  	u32			sactive;	/* active NCQ commands */
> +	u32			preempted_sactive;
>  
>  	unsigned int		flags;		/* ATA_LFLAG_xxx */
>  
> @@ -857,6 +859,10 @@ struct ata_port {
>  #ifdef CONFIG_ATA_ACPI
>  	struct ata_acpi_gtm	__acpi_init_gtm; /* use ata_acpi_init_gtm() */
>  #endif
> +
> +	u64 preempted_qc_active;
> +	int preempted_nr_active_links;
> +
>  	/* owned by EH */
>  	u8			sector_buf[ATA_SECT_SIZE] ____cacheline_aligned;
>  };

-- 
Damien Le Moal
Western Digital Research