Re: [PATCH 1/2] scsi: scsi_debug: Enforce physical block alignment of zoned writes

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

On 2026/09/17 15:45, Niklas Cassel wrote:
> ZBC-3 r06 (T10/BSR INCITS 579), 4.5.3.3.2 Write access pattern
> requirements for sequential write required zones, states:
> 
>   The device server terminates with CHECK CONDITION status, with the
>   sense key set to ILLEGAL REQUEST, and the additional sense code set
>   to UNALIGNED WRITE COMMAND a write command, other than an entire
>   medium write same command, that specifies:
>     a) the starting LBA in a sequential write required zone set to a
>        value that is not equal to the write pointer for that sequential
>        write required zone; or
>     b) an ending LBA that is not equal to the last logical block within
>        a physical block (see SBC-5).
> 
> That is why sd_zbc_read_zones() sets the zone_write_granularity queue
> limit to the physical block size of a host-managed device, exposing the
> constraint to user space.
> 
> check_zbc_access_params() implements condition a) but not condition b):
> it verifies that a write to a sequential write required zone starts at
> the write pointer of the zone, but never validates the ending LBA. As a
> consequence, when scsi_debug emulates a host-managed device whose
> physical block size is larger than its logical block size, for instance
> with zbc=managed sector_size=512 physblk_exp=3, a write of a single
> logical block at the write pointer of a sequential zone is accepted and
> advances the write pointer by one logical block. The write pointer is
> then no longer a multiple of the zone_write_granularity reported for the
> device, so nothing can write at it at the granularity that was
> advertised, and the zone can only be used again after being reset.
> 
> Implement condition b) as well, with the same sense data as the write
> pointer check, as the standard gives both conditions the same sense key
> and additional sense code. The exclusion of an entire medium write same
> command needs no special case: such a command spans the whole medium, so
> it is already terminated with WRITE BOUNDARY VIOLATION by the preceding
> check.
> 
> The check is placed in check_zbc_access_params(), which every command
> that advances a zone write pointer reaches first: WRITE, WRITE SCATTERED
> and WRITE SAME. Reads return earlier in the function and are unaffected.
> 
> Sequential write preferred zones, which are emulated for host-aware
> devices with zbc=aware, are left alone: writes to them are not required
> to be sequential, and Linux does not restrict the write granularity of
> host-aware devices.
> 
> With the default physblk_exp=0, the physical block size equals the
> logical block size and the new check is a no-op.
> 
> Assisted-by: LLM
> Fixes: f0d1cf9378bd ("scsi: scsi_debug: Add ZBC zone commands")
> Signed-off-by: Niklas Cassel <cassel@kernel.org>

Looks good, but that will be another conflict with linux-next...
May be rebase the fix on scsi-staging and let's push it to 7.4 instead?

Either way,

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


-- 
Damien Le Moal
Western Digital Research