On Mon, Jun 17, 2024 at 07:04:23PM +0100, John Garry wrote: >> Nit: I'd cache blk_rq_bytes(req), since that is repeating and this >> function is called for each atomic IO. > > blk_rq_bytes() is just a wrapper for rq->__data_len. I suppose that we > could cache that value to stop re-reading that memory, but I would > hope/expect that memory to be in the CPU cache anyway. Yes, that feels a bit pointless. > Only NVMe supports an LBA space boundary, so that part is specific to NVMe. > > Regardless, the block layer already should ensure that the atomic write > length and boundary is respected. nvme_valid_atomic_write() is just an > insurance policy against the block layer or some other component not doing > its job. > > For SCSI, the device would error - for example - if the atomic write length > was larger than the device supported. NVMe silently just does not execute > the write atomically in that scenario, which we must avoid. It might be worth to expand the comment to include this information to help future readers.
