No subject

Fri Jul 8 11:39:09 CEST 2016

If unmap operations are requested in a WRITE SAME command,
then for each specified LBA:

if the Data-Out Buffer of the WRITE SAME command is the same as the
logical block data returned by a read operation from that LBA while in
the unmapped state (see, then:

1) the device server performs the actions described in table 6; and

2) if an unmap operation is not performed in step 1), then the device
server shall perform the specified write operation to that LBA;

and from the description of WRITE SAME (10): "subsequent read operations
behave as if the device server wrote the single block of user data
received from the Data-Out Buffer to each logical block without
modification" (I have a slightly older copy though, it's 5.45 here).

It's pretty unambiguous that if the device cannot unmap (including the
case where the request is misaligned with respect to the granularity) it
does a write.

> Another question is, if the specification of WRITE SAME + UNMAP would be
> made unambiguous in the SBC document, whether or not we should take the risk
> to trigger behavior that is not what we expect by sending unaligned WRITE
> SAME + UNMAP commands to SCSI devices?

Yes, I think we should.


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