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Message-ID: <44f7297f-6f3a-cba9-ada1-c59188a98c9a@huawei.com>
Date:   Thu, 15 Dec 2022 17:19:58 +0800
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Subject: Re: [PATCH] ata:libata-eh:Cleanup ata_scsi_cmd_error_handler
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To:     Niklas Cassel <Niklas.Cassel@wdc.com>
CC:     Damien Le Moal <damien.lemoal@opensource.wdc.com>,
        "linux-ide@vger.kernel.org" <linux-ide@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "liuzhiqiang26@huawei.com" <liuzhiqiang26@huawei.com>,
        "linfeilong@huawei.com" <linfeilong@huawei.com>
References: <20221215050416.1891113-1-haowenchao@huawei.com>
 <Y5rgrhJuX6xCDEa3@x1-carbon>
From:   Wenchao Hao <haowenchao@huawei.com>
In-Reply-To: <Y5rgrhJuX6xCDEa3@x1-carbon>
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On 2022/12/15 16:54, Niklas Cassel wrote:
> On Thu, Dec 15, 2022 at 01:04:16PM +0800, Wenchao Hao wrote:
>> If ap->ops->error_handler is NULL, just go out and release the
>> spinlock. This patch is just a cleanup, which would not change
>> the origin error handle logic.
>>
>> Signed-off-by: Wenchao Hao <haowenchao@huawei.com>
>> ---
>>  drivers/ata/libata-eh.c | 96 ++++++++++++++++++++---------------------
>>  1 file changed, 48 insertions(+), 48 deletions(-)
>>
>> diff --git a/drivers/ata/libata-eh.c b/drivers/ata/libata-eh.c
>> index 34303ce67c14..66ca3ac7cd58 100644
>> --- a/drivers/ata/libata-eh.c
>> +++ b/drivers/ata/libata-eh.c
>> @@ -565,6 +565,8 @@ 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);
>> @@ -584,62 +586,60 @@ 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->error_handler)
>> +		goto out;
> 
> Nice cleanup!
> 
> However, I don't think there is any point in taking the spin lock if there is
> no error_handler.
> 
> So I think that you can do similar to the skip_eh label in ata_port_detach():
> https://github.com/torvalds/linux/blob/master/drivers/ata/libata-core.c#L5904
> 
> 
> Kind regards,
> Niklas
> 

I did not want to change the origin logic. But it looks unnecessary to take 
the spin lock, would update.

>>  
>> -		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;
>> +out:
>>  	spin_unlock_irqrestore(ap->lock, flags);
>>  
>>  }
>> -- 
>> 2.32.0
>> .