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

[Niklas Cassel <cassel@kernel.org>]

On Thu, Sep 17, 2026 at 04:05:54PM +0700, Damien Le Moal wrote:
> 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?

Considering that the fixes are only for a moduled used for debug,
I can do that.

Will rebase on mkp/7.4/scsi-staging


Kind regards,
Niklas