Re: [PATCH v14 10/19] scsi: core: Retry unaligned zoned writes

Damien Le Moal
2023-10-24T00:13:40Z

On 10/24/23 06:54, Bart Van Assche wrote:
> If zoned writes (REQ_OP_WRITE) for a sequential write required zone have
> a starting LBA that differs from the write pointer, e.g. because zoned
> writes have been reordered, then the storage device will respond with an
> UNALIGNED WRITE COMMAND error. Send commands that failed with an
> unaligned write error to the SCSI error handler if zone write locking is
> disabled. The SCSI error handler will sort SCSI commands per LBA before
> resubmitting these.
>
> If zone write locking is disabled, increase the number of retries for
> write commands sent to a sequential zone to the maximum number of
> outstanding commands because in the worst case the number of times
> reordered zoned writes have to be retried is (number of outstanding
> writes per sequential zone) - 1.
>
> Reviewed-by: Damien Le Moal <dlemoal@kernel.org>
> Cc: Martin K. Petersen <martin.petersen@oracle.com>
> Cc: Christoph Hellwig <hch@lst.de>
> Cc: Ming Lei <ming.lei@redhat.com>
> Signed-off-by: Bart Van Assche <bvanassche@acm.org>
> ---
> drivers/scsi/scsi_error.c | 16 ++++++++++++++++
> drivers/scsi/scsi_lib.c | 1 +
> drivers/scsi/sd.c | 6 ++++++
> include/scsi/scsi.h | 1 +
> 4 files changed, 24 insertions(+)
>
> diff --git a/drivers/scsi/scsi_error.c b/drivers/scsi/scsi_error.c
> index 8b1eb637ffa8..9a54856fa03b 100644
> --- a/drivers/scsi/scsi_error.c
> +++ b/drivers/scsi/scsi_error.c
> @@ -699,6 +699,22 @@ enum scsi_disposition scsi_check_sense(struct scsi_cmnd *scmd)
> fallthrough;
>
> case ILLEGAL_REQUEST:
> + /*
> + * Unaligned write command. This may indicate that zoned writes
> + * have been received by the device in the wrong order. If zone
> + * write locking is disabled, retry after all pending commands
> + * have completed.
> + */
> + if (sshdr.asc == 0x21 && sshdr.ascq == 0x04 &&
> + !req->q->limits.use_zone_write_lock &&
> + blk_rq_is_seq_zoned_write(req) &&
> + scmd->retries <= scmd->allowed) {
> + sdev_printk(KERN_INFO, scmd->device,
> + "Retrying unaligned write at LBA %#llx.\n",
> + scsi_get_lba(scmd));

KERN_INFO ? Did you perhaps mean KERN_DEBUG ? An info message for this will be
way too noisy.

> + return NEEDS_DELAYED_RETRY;
> + }
> +
> if (sshdr.asc == 0x20 || /* Invalid command operation code */
> sshdr.asc == 0x21 || /* Logical block address out of range */
> sshdr.asc == 0x22 || /* Invalid function */
> diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
> index c2f647a7c1b0..33a34693c8a2 100644
> --- a/drivers/scsi/scsi_lib.c
> +++ b/drivers/scsi/scsi_lib.c
> @@ -1443,6 +1443,7 @@ static void scsi_complete(struct request *rq)
> case ADD_TO_MLQUEUE:
> scsi_queue_insert(cmd, SCSI_MLQUEUE_DEVICE_BUSY);
> break;
> + case NEEDS_DELAYED_RETRY:
> default:
> scsi_eh_scmd_add(cmd);
> break;
> diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c
> index 82abc721b543..4e6b77f5854f 100644
> --- a/drivers/scsi/sd.c
> +++ b/drivers/scsi/sd.c
> @@ -1197,6 +1197,12 @@ static blk_status_t sd_setup_read_write_cmnd(struct scsi_cmnd *cmd)
> cmd->transfersize = sdp->sector_size;
> cmd->underflow = nr_blocks << 9;
> cmd->allowed = sdkp->max_retries;
> + /*
> + * Increase the number of allowed retries for zoned writes if zone
> + * write locking is disabled.
> + */
> + if (!rq->q->limits.use_zone_write_lock && blk_rq_is_seq_zoned_write(rq))
> + cmd->allowed += rq->q->nr_requests;
> cmd->sdb.length = nr_blocks * sdp->sector_size;
>
> SCSI_LOG_HLQUEUE(1,
> diff --git a/include/scsi/scsi.h b/include/scsi/scsi.h
> index ec093594ba53..6600db046227 100644
> --- a/include/scsi/scsi.h
> +++ b/include/scsi/scsi.h
> @@ -93,6 +93,7 @@ static inline int scsi_status_is_check_condition(int status)
> * Internal return values.
> */
> enum scsi_disposition {
> + NEEDS_DELAYED_RETRY = 0x2000,
> NEEDS_RETRY = 0x2001,
> SUCCESS = 0x2002,
> FAILED = 0x2003,

--
Damien Le Moal
Western Digital Research