Re: [PATCH 2/2] scsi: scsi_debug: Validate zone access for WRITE ATOMIC (16)

[Niklas Cassel <cassel@kernel.org>]

On Thu, Sep 17, 2026 at 11:26:45AM +0100, John Garry wrote:
> On 9/17/26 10:56, Niklas Cassel wrote:
> > On Thu, Sep 17, 2026 at 10:38:30AM +0100, John Garry wrote:
> > > On 9/17/26 09:45, Niklas Cassel wrote:
> > > 
> > > So far we have not considered atomic writes for zoned devices
> > > - do devices which support both technologies exist? Or is
> > > this just hypothetical?
> > If the specs allow it, someone might build it.
> 
> Sure, but do they (allow it)? atomic writes have specific
> alignment and granularity rules - how does that play with
> zoned devices?
> 
> I would need to check the specs more on this..

I haven't been able to find anything that disallows it.

Trying to parse the specs with the help of LLM:

""
WRITE ATOMIC (16) is a write command as far as ZBC is concerned, so on a
zoned device it is subject to the access requirements of the zone that it
addresses, and it advances the write pointer of a sequential write
required zone.
Neither standard says so directly, but the definitions leave no room for
anything else. SBC-6 r02 defines an atomic write operation as a "process
by which a device server performs a write operation that is either
completed in its entirety or has no effects on stored logical block
data" (3.1.9), and an atomic write command as a "command that performs
one or more atomic write operations" (3.1.8). ZBC-3 r06 in turn defines
a write operation as a "write operation as described in SBC-5 with the
additional requirements described in this standard" (3.1.62), and a
write command as a "command that requests write operations" (3.1.61).
WRITE ATOMIC (16) therefore falls under 4.5.3.3.2 Write access pattern
requirements for sequential write required zones, exactly as WRITE (16)
does.
""

Right now, I don't see why WRITE ATOMIC should not be allowed on a ZBC
drive.


Kind regards,
Niklas