On 6/26/24 03:18, Bart Van Assche wrote: > On 6/24/24 2:55 PM, Damien Le Moal wrote: >> I am still a little confused as to why we need 2 BIOs, one for src and one for >> dst... Is it because of the overly complex scsi extended copy support ? >> >> Given that the main use case is copy offload for data within the same device, >> using a single BIO which somehow can carry a list of LBA sources and a single >> destination LBA would be far simpler and perfectly matching nvme simple copy and >> ATA write gathered. And I think that this would also match the simplest case for >> scsi extended copy as well. > > Hi Damien, > > What are the implications for the device mapper code if the copy source > and destination LBAs are encoded in the bio payload instead of in > bio->bi_sector? DM can deal with "abnormal" BIOs on its own. There is code for that. See is_abnormal_io() and __process_abnormal_io(). Sure, that will need more code compared to a bio sector+size based simple split, but I do not think it is a big deal given the potential benefits of the offloading. -- Damien Le Moal Western Digital Research
