Re: [PATCH v10 09/18] scsi: scsi_debug: Add the preserves_write_order module parameter

[Douglas Gilbert <dgilbert@interlog.com>]

On 2023-08-18 15:34, Bart Van Assche wrote:
> Zone write locking is not used for zoned devices if the block driver
> reports that it preserves the order of write commands. Make it easier to
> test not using zone write locking by adding support for setting the
> driver_preserves_write_order flag.
> 
> Cc: Martin K. Petersen <martin.petersen@oracle.com>
> Cc: Douglas Gilbert <dgilbert@interlog.com>
> Cc: Damien Le Moal <dlemoal@kernel.org>
> Cc: Christoph Hellwig <hch@lst.de>
> Cc: Ming Lei <ming.lei@redhat.com>
> Signed-off-by: Bart Van Assche <bvanassche@acm.org>

Acked-by: Douglas Gilbert <dgilbert@interlog.com>

> ---
>   drivers/scsi/scsi_debug.c | 9 +++++++++
>   1 file changed, 9 insertions(+)
> 
> diff --git a/drivers/scsi/scsi_debug.c b/drivers/scsi/scsi_debug.c
> index 9c0af50501f9..1ea4925d2c2f 100644
> --- a/drivers/scsi/scsi_debug.c
> +++ b/drivers/scsi/scsi_debug.c
> @@ -832,6 +832,7 @@ static int dix_reads;
>   static int dif_errors;
>   
>   /* ZBC global data */
> +static bool sdeb_preserves_write_order;
>   static bool sdeb_zbc_in_use;	/* true for host-aware and host-managed disks */
>   static int sdeb_zbc_zone_cap_mb;
>   static int sdeb_zbc_zone_size_mb;
> @@ -5138,9 +5139,13 @@ static struct sdebug_dev_info *find_build_dev_info(struct scsi_device *sdev)
>   
>   static int scsi_debug_slave_alloc(struct scsi_device *sdp)
>   {
> +	struct request_queue *q = sdp->request_queue;
> +
>   	if (sdebug_verbose)
>   		pr_info("slave_alloc <%u %u %u %llu>\n",
>   		       sdp->host->host_no, sdp->channel, sdp->id, sdp->lun);
> +	if (sdeb_preserves_write_order)
> +		q->limits.driver_preserves_write_order = true;
>   	return 0;
>   }
>   
> @@ -5755,6 +5760,8 @@ module_param_named(statistics, sdebug_statistics, bool, S_IRUGO | S_IWUSR);
>   module_param_named(strict, sdebug_strict, bool, S_IRUGO | S_IWUSR);
>   module_param_named(submit_queues, submit_queues, int, S_IRUGO);
>   module_param_named(poll_queues, poll_queues, int, S_IRUGO);
> +module_param_named(preserves_write_order, sdeb_preserves_write_order, bool,
> +		   S_IRUGO);
>   module_param_named(tur_ms_to_ready, sdeb_tur_ms_to_ready, int, S_IRUGO);
>   module_param_named(unmap_alignment, sdebug_unmap_alignment, int, S_IRUGO);
>   module_param_named(unmap_granularity, sdebug_unmap_granularity, int, S_IRUGO);
> @@ -5812,6 +5819,8 @@ MODULE_PARM_DESC(ndelay, "response delay in nanoseconds (def=0 -> ignore)");
>   MODULE_PARM_DESC(no_lun_0, "no LU number 0 (def=0 -> have lun 0)");
>   MODULE_PARM_DESC(no_rwlock, "don't protect user data reads+writes (def=0)");
>   MODULE_PARM_DESC(no_uld, "stop ULD (e.g. sd driver) attaching (def=0))");
> +MODULE_PARM_DESC(preserves_write_order,
> +		 "Whether or not to inform the block layer that this driver preserves the order of WRITE commands (def=0)");
>   MODULE_PARM_DESC(num_parts, "number of partitions(def=0)");
>   MODULE_PARM_DESC(num_tgts, "number of targets per host to simulate(def=1)");
>   MODULE_PARM_DESC(opt_blks, "optimal transfer length in blocks (def=1024)");