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

[John Garry <john.garry@linux.dev>]

On 9/17/26 11:35, Niklas Cassel wrote:
> 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.
> 
> 
So what happens when the write pointer is not aligned with Atomic 
alignment? Are atomic writes just not permitted in that scenario?