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WRITE SAME > must always ensure reads return the data written using it, Yep, but many device vendors messed that up due to the initial ambiguity in the spec wrt. how to handle the UNMAP flag. Based on experience with the SCSI UNMAP command being able to ignore blocks and ATA DSM TRIM being non-deterministic, several vendors ended up not treating WRITE SAME with the UNMAP flag set as a data integrity operation. I was just concerned that this practice would carry over to NVMe. Bits 2:0 being set to 1 is an indication that somebody at least thought about this scenario during device implementation. But again, devices that return non-zero blocks after deallocate are rare and we can always quirk them if there's a problem. Anyway. Not a big issue as far as I'm concerned. Just tainted by the twisted heuristics I had to deal with in SCSI... -- Martin K. Petersen Oracle Linux Engineering