Re: [PATCH v4 07/10] scsi: scsi_debug: Do not write a partial physical block to a zoned device

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

On 2026/09/18 13:29, Niklas Cassel wrote:
> do_device_access() copies one logical block at a time and stops at the
> first short copy, so when the data-out buffer is smaller than the
> transfer length of the command it can write part of a physical block.
> An initiator can arrange that with SG_IO.
> 
> A write that does not end on a physical block boundary is perfectly
> acceptable to a device that is not zoned, and to a conventional zone,
> where the device reads, modifies and writes the physical block that the
> write falls in. ZBC-3 r06 (T10/BSR INCITS 579), 4.5.3.3.2, does require
> a write to a sequential write required zone to end on a physical block
> boundary, though, so a partly written physical block is not a state that
> such a zone can be left in.
> 
> Stop at the last whole physical block that the buffer holds, for a
> sequential write required zone only. The bytes that are left over are
> not written, and are reported to the initiator as part of the residual.
> 
> With the default physblk_exp=0 the physical block size equals the
> logical block size and this changes nothing. Nothing changes either when
> the buffer holds all of the data that the command asks for, so a command
> that transfers fewer logical blocks than a physical block is unaffected
> wherever it is legal.
> 
> Assisted-by: LLM
> Signed-off-by: Niklas Cassel <cassel@kernel.org>

A bit shift would be nicer than a division... But nevertheless, looks good.

Reviewed-by: Damien Le Moal <dlemoal@kernel.org>


-- 
Damien Le Moal
Western Digital Research