Re: [PATCH v9 09/17] scsi: scsi_debug: Support disabling zone write locking

[Damien Le Moal <dlemoal@kernel.org>]

On 8/17/23 04:53, Bart Van Assche wrote:
> Make it easier to test not using zone write locking by supporting
> disabling zone write locking in the scsi_debug driver.
> 
> 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>
> ---
>  drivers/scsi/scsi_debug.c | 8 ++++++++
>  1 file changed, 8 insertions(+)
> 
> diff --git a/drivers/scsi/scsi_debug.c b/drivers/scsi/scsi_debug.c
> index 9c0af50501f9..c44c523bde2c 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_no_zwrl;
>  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_no_zwrl)
> +		q->limits.driver_preserves_write_order = true;

The option is named and discribed as "no_zone_write_lock", which is a block
layer concept. Given that this sets driver_preserves_write_order and does not
touch the use_zone_write_locking limit, I think it is better to name the option
"preserve_write_order" (or similar) to avoid confusion.

>  	return 0;
>  }
>  
> @@ -5738,6 +5743,7 @@ module_param_named(ndelay, sdebug_ndelay, int, S_IRUGO | S_IWUSR);
>  module_param_named(no_lun_0, sdebug_no_lun_0, int, S_IRUGO | S_IWUSR);
>  module_param_named(no_rwlock, sdebug_no_rwlock, bool, S_IRUGO | S_IWUSR);
>  module_param_named(no_uld, sdebug_no_uld, int, S_IRUGO);
> +module_param_named(no_zone_write_lock, sdeb_no_zwrl, bool, S_IRUGO);
>  module_param_named(num_parts, sdebug_num_parts, int, S_IRUGO);
>  module_param_named(num_tgts, sdebug_num_tgts, int, S_IRUGO | S_IWUSR);
>  module_param_named(opt_blks, sdebug_opt_blks, int, S_IRUGO);
> @@ -5812,6 +5818,8 @@ 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(no_zone_write_lock,
> +		 "Disable serialization of zoned writes (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)");

-- 
Damien Le Moal
Western Digital Research