Re: [PATCH v10 07/33] scsi: sd: Have scsi-ml retry read_capacity_16 errors

[John Garry <john.g.garry@oracle.com>]

On 14/07/2023 22:33, Mike Christie wrote:
> This has read_capacity_16 have scsi-ml retry errors instead of driving
> them itself.
> 
> There are 2 behavior changes with this patch:
> 1. There is one behavior change where we no longer retry when
> scsi_execute_cmd returns < 0, but we should be ok. We don't need to retry
> for failures like the queue being removed, and for the case where there
> are no tags/reqs since the block layer waits/retries for us. For possible
> memory allocation failures from blk_rq_map_kern we use GFP_NOIO, so
> retrying will probably not help.
> 2. For the specific UAs we checked for and retried, we would get
> READ_CAPACITY_RETRIES_ON_RESET retries plus whatever retries were left
> from the loop's retries. Each UA now gets READ_CAPACITY_RETRIES_ON_RESET
> reties, and the other errors (not including medium not present) get up
> to 3 retries.
> 
> Signed-off-by: Mike Christie <michael.christie@oracle.com>
> Reviewed-by: Christoph Hellwig <hch@lst.de>

Regardless of a couple of nitpicks, below:

Reviewed-by: John Garry <john.g.garry@oracle.com>

> ---
>   drivers/scsi/sd.c | 106 ++++++++++++++++++++++++++++++----------------
>   1 file changed, 69 insertions(+), 37 deletions(-)
> 
> diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c
> index 755b09beff2a..245419fe9358 100644
> --- a/drivers/scsi/sd.c
> +++ b/drivers/scsi/sd.c
> @@ -2402,55 +2402,87 @@ static void read_capacity_error(struct scsi_disk *sdkp, struct scsi_device *sdp,
>   static int read_capacity_16(struct scsi_disk *sdkp, struct scsi_device *sdp,
>   						unsigned char *buffer)
>   {
> -	unsigned char cmd[16];
> +	static const u8 cmd[16] = { SERVICE_ACTION_IN_16, SAI_READ_CAPACITY_16,
> +				    0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, RC16_LEN };

In terms of coding style, could you follow previous style, like:
	static const u8 cmd[16] = {
		[0] = SERVICE_ACTION_IN_16,
		[1] = SAI_READ_CAPACITY_16,
		[13] = RC16_LEN,
	};
	
Seems safe to me (to ensure we fill in the correct array element).

>   	struct scsi_sense_hdr sshdr;
> -	const struct scsi_exec_args exec_args = {
> -		.sshdr = &sshdr,
> -	};
>   	int sense_valid = 0;
>   	int the_result;
> -	int retries = 3, reset_retries = READ_CAPACITY_RETRIES_ON_RESET;
>   	unsigned int alignment;
>   	unsigned long long lba;
>   	unsigned sector_size;
> +	struct scsi_failure failures[] = {
> +		/*
> +		 * Fail immediately for Invalid Command Operation Code or
> +		 * Invalid Field in CDB.
> +		 */
> +		{
> +			.sense = ILLEGAL_REQUEST,
> +			.asc = 0x20,
> +			.allowed = 0,
> +			.result = SAM_STAT_CHECK_CONDITION,
> +		},
> +		{
> +			.sense = ILLEGAL_REQUEST,
> +			.asc = 0x24,
> +			.allowed = 0,
> +			.result = SAM_STAT_CHECK_CONDITION,
> +		},
> +		/* Fail immediately for Medium Not Present */
> +		{
> +			.sense = UNIT_ATTENTION,
> +			.asc = 0x3A,
> +			.allowed = 0,
> +			.result = SAM_STAT_CHECK_CONDITION,
> +		},
> +		{
> +			.sense = NOT_READY,
> +			.asc = 0x3A,
> +			.ascq = 0x0,
> +			.allowed = 0,
> +			.result = SAM_STAT_CHECK_CONDITION,
> +		},
> +		{
> +			.sense = UNIT_ATTENTION,
> +			.asc = 0x29,
> +			/* Device reset might occur several times */
> +			.allowed = READ_CAPACITY_RETRIES_ON_RESET,
> +			.result = SAM_STAT_CHECK_CONDITION,
> +		},
> +		/* Any other error not listed above retry */
> +		{
> +			.result = SCMD_FAILURE_RESULT_ANY,
> +			.allowed = 3,
> +		},
> +		{}
> +	};
> +	const struct scsi_exec_args exec_args = {
> +		.sshdr = &sshdr,
> +		.failures = failures,
> +	};
>   
>   	if (sdp->no_read_capacity_16)
>   		return -EINVAL;
>   
> -	do {
> -		memset(cmd, 0, 16);
> -		cmd[0] = SERVICE_ACTION_IN_16;
> -		cmd[1] = SAI_READ_CAPACITY_16;
> -		cmd[13] = RC16_LEN;
> -		memset(buffer, 0, RC16_LEN);
> -
> -		the_result = scsi_execute_cmd(sdp, cmd, REQ_OP_DRV_IN,
> -					      buffer, RC16_LEN, SD_TIMEOUT,
> -					      sdkp->max_retries, &exec_args);
> -		if (the_result > 0) {
> -			if (media_not_present(sdkp, &sshdr))
> -				return -ENODEV;
> +	memset(buffer, 0, RC16_LEN);
>   
> -			sense_valid = scsi_sense_valid(&sshdr);
> -			if (sense_valid &&
> -			    sshdr.sense_key == ILLEGAL_REQUEST &&
> -			    (sshdr.asc == 0x20 || sshdr.asc == 0x24) &&
> -			    sshdr.ascq == 0x00)
> -				/* Invalid Command Operation Code or
> -				 * Invalid Field in CDB, just retry
> -				 * silently with RC10 */
> -				return -EINVAL;
> -			if (sense_valid &&
> -			    sshdr.sense_key == UNIT_ATTENTION &&
> -			    sshdr.asc == 0x29 && sshdr.ascq == 0x00)
> -				/* Device reset might occur several times,
> -				 * give it one more chance */
> -				if (--reset_retries > 0)
> -					continue;
> -		}
> -		retries--;
> +	the_result = scsi_execute_cmd(sdp, cmd, REQ_OP_DRV_IN, buffer,
> +				      RC16_LEN, SD_TIMEOUT, sdkp->max_retries,
> +				      &exec_args);
>   
> -	} while (the_result && retries);
> +	if (the_result > 0) {
> +		if (media_not_present(sdkp, &sshdr))
> +			return -ENODEV;
> +
> +		sense_valid = scsi_sense_valid(&sshdr);
> +		if (sense_valid && sshdr.sense_key == ILLEGAL_REQUEST &&
> +		    (sshdr.asc == 0x20 || sshdr.asc == 0x24) &&
> +		     sshdr.ascq == 0x00)
> +			/*
> +			 * Invalid Command Operation Code or Invalid Field in
> +			 * CDB, just retry silently with RC10
> +			 */
> +			return -EINVAL;


nit: personally I would use {} here, like below, but that's your choice.


  (sshdr.asc == 0x20 || sshdr.asc == 0x24) &&
		     sshdr.ascq == 0x00) {
			/*
			 * Invalid Command Operation Code or Invalid Field in
			 * CDB, just retry silently with RC10
			 */
			return -EINVAL;
}

> +	}
>   
>   	if (the_result) {
>   		sd_print_result(sdkp, "Read Capacity(16) failed", the_result);