Re: [PATCH] blk-settings: round down io_opt to at least 4K

[Milan Broz <gmazyland@gmail.com>]

On 2/10/25 1:54 PM, Mikulas Patocka wrote:

...

>> Can you send me the output of:
>>
>> # sg_vpd -p bl /dev/sdN
>>
>> and maybe hdparm -I too? I'd like to see if we can come up with a
>> reasonable heuristic.
>>
>> -- 
>> Martin K. Petersen	Oracle Linux Engineering
> 
> I don't have that USB-SATA bridge that reports optimal I/O size 65535
> sectors. Milan talked about it, but maybe he doesn't have it too. Some
> user reported that cryptsetup behaves badly with this particular bridge,
> so Milan wrote workaround for it in cryptsetup.

I think I have that adapter somewhere in the box (I guess it is JMicron thingy).
But the change in cryptsetup was based on several user reports (one was
https://gitlab.com/cryptsetup/cryptsetup/-/issues/585 but there is too
much confusion from my side :-)

We just added a rule to ignore bogus value and stay with a default
alignment in that case.

There are some links in the report, though:
https://linux-blog.anracom.com/2018/12/03/linux-ssd-partition-alignment-problems-with-external-usb-to-sata-controllers-i/
https://bugzilla.redhat.com/show_bug.cgi?id=1420935

It is an old story, apparently.

If I see it again, I can send report (or even fix) to linux-usb list,
as this is really related to USB storage driver (AFAIK).

The code below just simulated what the USB enclosure presented to kernel.
  
> You can simulate it with "modprobe scsi_debug dev_size_mb=32
> sector_size=512 num_tgts=1 opt_blks=65535"

Milan