Re: [PATCH 2/2] scsi: scsi_debug: enable sdebug_sector_size > PAGE_SIZE

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

On 02/03/2026 12:27, Swarna Prabhu wrote:
>>>> PAGE_SIZE in scsi_debug.
>> Surely the sd driver or block layer should be catching non-compliant HW,
>> right?
> Yes, the sd driver and block layer will catch any non compliant HW.
>> The scsi_debug driver should minic HW, and there is nothing in any SCSI
>> specs which mentions that the sector size needs to be limited to 64KB or the
>> like - am I correct? The useful thing about scsi_debug is that we can
>> pretend to be broken* HW and see if the upper layers catch it.
>>
>> *broken for Linux or non-compliant wrt spec
>>
> As you pointed, the SCSI spec doesn't restrict the sector size to be
> limited to 64 KiB. Earlier block layer had limitations on block size
> upto PAGE_SIZE. With that limitation being addressed and sd driver
> change, sd driver and block layer can handle large block sizes
> correctly. By allowing large sector size on scsi debug we allow
> emulation of spec compliant HW.

Sure, so is there any reason to have those checks in scsi_debug at all? 
Would removing them break that driver and be unsafe?

Thanks,
John

> 
>>> Reviewed-by: Damien Le Moal<dlemoal@kernel.org>
>>> Signed-off-by: Swarna Prabhu<s.prabhu@samsung.com>
>>> ---
>>>    drivers/scsi/scsi_debug.c | 8 +-------
>>>    1 file changed, 1 insertion(+), 7 deletions(-)
>>>
>>> diff --git a/drivers/scsi/scsi_debug.c b/drivers/scsi/scsi_debug.c
>>> index c947655db518..4c6feee87f05 100644
>>> --- a/drivers/scsi/scsi_debug.c
>>> +++ b/drivers/scsi/scsi_debug.c
>>> @@ -8495,13 +8495,7 @@ static int __init scsi_debug_init(void)
>>>    	} else if (sdebug_ndelay > 0)
>>>    		sdebug_jdelay = JDELAY_OVERRIDDEN;
>>> -	switch (sdebug_sector_size) {
>>> -	case  512:
>>> -	case 1024:
>>> -	case 2048:
>>> -	case 4096:
>>> -		break;
>>> -	default:
>>> +	if (blk_validate_block_size(sdebug_sector_size)) {
>>>    		pr_err("invalid sector_size %d\n", sdebug_sector_size);
>>>    		return -EINVAL;