[PATCH v6 01/11] scsi: scsi_debug: Refuse a zoned device with a non-zero lowest aligned LBA

[Niklas Cassel <cassel@kernel.org>]

scsi_debug reports the lowest_aligned module parameter in the LOWEST
ALIGNED LOGICAL BLOCK ADDRESS field, see SBC-6 r02 (T10/BSR INCITS 587),
5.20.2, but nothing else in the driver acts on it.

On a zoned device a non-zero value puts the start of every zone in the
middle of a physical block. ZBC requires a write to a sequential write
required zone to end on a physical block boundary, so a host writing in
units of the reported zone write granularity could never write such a
zone at all.

Refuse the combination rather than emulate a device that cannot be used.

Assisted-by: LLM
Reviewed-by: Damien Le Moal <dlemoal@kernel.org>
Signed-off-by: Niklas Cassel <cassel@kernel.org>
---
Tested by loading the module with each combination:

  zbc=managed lowest_aligned=8    refused, -EINVAL
  zbc=aware   lowest_aligned=8    refused, -EINVAL
  zbc=managed lowest_aligned=0    loads
  lowest_aligned=8                loads, as the device is not zoned
---
 drivers/scsi/scsi_debug.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/scsi/scsi_debug.c b/drivers/scsi/scsi_debug.c
index 6941809dfdb7..c664966e95cb 100644
--- a/drivers/scsi/scsi_debug.c
+++ b/drivers/scsi/scsi_debug.c
@@ -8734,6 +8734,11 @@ static int __init scsi_debug_init(void)
 			sdebug_dev_size_mb = DEF_ZBC_DEV_SIZE_MB;
 	}
 
+	if (sdeb_zbc_in_use && sdebug_lowest_aligned) {
+		pr_err("lowest_aligned is not supported by a zoned device\n");
+		return -EINVAL;
+	}
+
 	if (sdebug_dev_size_mb == DEF_DEV_SIZE_PRE_INIT)
 		sdebug_dev_size_mb = DEF_DEV_SIZE_MB;
 	if (sdebug_dev_size_mb < 1)
-- 
2.55.0