Re: [PATCH v3] ata: libata-eh: Cleanup ata_scsi_cmd_error_handler()

[Niklas Cassel]

On Thu, Dec 15, 2022 at 11:37:49PM +0800, Wenchao Hao wrote:
> If ap->ops->error_handler is NULL just return. This patch also
> fixes some comment style issue.
> 
> ---
> v3:
> - Start with a "/*" empty line for multi-line comments.
> - Correct the commit subject
> 
> v2:
> - Check ap->ops->error_handler without taking the spin lock
> 
> Signed-off-by: Wenchao Hao <haowenchao@xxxxxxxxxx>
> ---
>  drivers/ata/libata-eh.c | 101 +++++++++++++++++++++-------------------
>  1 file changed, 52 insertions(+), 49 deletions(-)
> 
> diff --git a/drivers/ata/libata-eh.c b/drivers/ata/libata-eh.c
> index 34303ce67c14..56820b8e953a 100644
> --- a/drivers/ata/libata-eh.c
> +++ b/drivers/ata/libata-eh.c
> @@ -565,13 +565,19 @@ void ata_scsi_cmd_error_handler(struct Scsi_Host *host, struct ata_port *ap,
>  {
>  	int i;
>  	unsigned long flags;
> +	struct scsi_cmnd *scmd, *tmp;
> +	int nr_timedout = 0;
>  
>  	/* make sure sff pio task is not running */
>  	ata_sff_flush_pio_task(ap);
>  
> +	if (!ap->ops->error_handler)
> +		return;
> +
>  	/* synchronize with host lock and sort out timeouts */
>  
> -	/* For new EH, all qcs are finished in one of three ways -
> +	/*
> +	 * For new EH, all qcs are finished in one of three ways -
>  	 * normal completion, error completion, and SCSI timeout.
>  	 * Both completions can race against SCSI timeout.  When normal
>  	 * completion wins, the qc never reaches EH.  When error
> @@ -584,62 +590,59 @@ void ata_scsi_cmd_error_handler(struct Scsi_Host *host, struct ata_port *ap,
>  	 * timed out iff its associated qc is active and not failed.
>  	 */
>  	spin_lock_irqsave(ap->lock, flags);
> -	if (ap->ops->error_handler) {
> -		struct scsi_cmnd *scmd, *tmp;
> -		int nr_timedout = 0;
> -
> -		/* This must occur under the ap->lock as we don't want
> -		   a polled recovery to race the real interrupt handler
> -
> -		   The lost_interrupt handler checks for any completed but
> -		   non-notified command and completes much like an IRQ handler.
>  
> -		   We then fall into the error recovery code which will treat
> -		   this as if normal completion won the race */
> -
> -		if (ap->ops->lost_interrupt)
> -			ap->ops->lost_interrupt(ap);
> +	/*
> +	 * This must occur under the ap->lock as we don't want
> +	 * a polled recovery to race the real interrupt handler
> +	 *
> +	 * The lost_interrupt handler checks for any completed but
> +	 * non-notified command and completes much like an IRQ handler.
> +	 *
> +	 * We then fall into the error recovery code which will treat
> +	 * this as if normal completion won the race
> +	 */
> +	if (ap->ops->lost_interrupt)
> +		ap->ops->lost_interrupt(ap);
>  
> -		list_for_each_entry_safe(scmd, tmp, eh_work_q, eh_entry) {
> -			struct ata_queued_cmd *qc;
> +	list_for_each_entry_safe(scmd, tmp, eh_work_q, eh_entry) {
> +		struct ata_queued_cmd *qc;
>  
> -			ata_qc_for_each_raw(ap, qc, i) {
> -				if (qc->flags & ATA_QCFLAG_ACTIVE &&
> -				    qc->scsicmd == scmd)
> -					break;
> -			}
> +		ata_qc_for_each_raw(ap, qc, i) {
> +			if (qc->flags & ATA_QCFLAG_ACTIVE &&
> +			    qc->scsicmd == scmd)
> +				break;
> +		}
>  
> -			if (i < ATA_MAX_QUEUE) {
> -				/* the scmd has an associated qc */
> -				if (!(qc->flags & ATA_QCFLAG_FAILED)) {
> -					/* which hasn't failed yet, timeout */
> -					qc->err_mask |= AC_ERR_TIMEOUT;
> -					qc->flags |= ATA_QCFLAG_FAILED;
> -					nr_timedout++;
> -				}
> -			} else {
> -				/* Normal completion occurred after
> -				 * SCSI timeout but before this point.
> -				 * Successfully complete it.
> -				 */
> -				scmd->retries = scmd->allowed;
> -				scsi_eh_finish_cmd(scmd, &ap->eh_done_q);
> +		if (i < ATA_MAX_QUEUE) {
> +			/* the scmd has an associated qc */
> +			if (!(qc->flags & ATA_QCFLAG_FAILED)) {
> +				/* which hasn't failed yet, timeout */
> +				qc->err_mask |= AC_ERR_TIMEOUT;
> +				qc->flags |= ATA_QCFLAG_FAILED;
> +				nr_timedout++;
>  			}
> +		} else {
> +			/* Normal completion occurred after
> +			 * SCSI timeout but before this point.
> +			 * Successfully complete it.
> +			 */
> +			scmd->retries = scmd->allowed;
> +			scsi_eh_finish_cmd(scmd, &ap->eh_done_q);
>  		}
> +	}
>  
> -		/* If we have timed out qcs.  They belong to EH from
> -		 * this point but the state of the controller is
> -		 * unknown.  Freeze the port to make sure the IRQ
> -		 * handler doesn't diddle with those qcs.  This must
> -		 * be done atomically w.r.t. setting QCFLAG_FAILED.
> -		 */
> -		if (nr_timedout)
> -			__ata_port_freeze(ap);
> -
> +	/*
> +	 * If we have timed out qcs.  They belong to EH from
> +	 * this point but the state of the controller is
> +	 * unknown.  Freeze the port to make sure the IRQ
> +	 * handler doesn't diddle with those qcs.  This must
> +	 * be done atomically w.r.t. setting QCFLAG_FAILED.
> +	 */
> +	if (nr_timedout)
> +		__ata_port_freeze(ap);
>  
> -		/* initialize eh_tries */
> -		ap->eh_tries = ATA_EH_MAX_TRIES;
> -	}
> +	/* initialize eh_tries */
> +	ap->eh_tries = ATA_EH_MAX_TRIES;

Personally, I would prefer a newline between the spin_unlock_irqrestore()
and ap->eh_tries = ATA_EH_MAX_TRIES;

>  	spin_unlock_irqrestore(ap->lock, flags);
>  

You could also drop this superfluous newline.

>  }
> -- 
> 2.32.0
> 

With or without the above nits fixed:
Reviewed-by: Niklas Cassel <niklas.cassel@xxxxxxx>