Hi all, I recently went over code that directly access the bio_vec bv_page/ bv_offset members and the code in _drbd_send_bio/_drbd_send_zc_bio came to my attention. It iterates the bio to kmap all segments, and then either does a sock_sendmsg on a newly created kvec iter, or one one a new bvec iter for each segment. The former can't work on highmem systems and both versions are rather inefficient. What is preventing drbd from doing a single sock_sendmsg with the bvec payload? nvme-tcp (nvme_tcp_init_iter0 is a good example for doing that, or the sunrpc svcsock code using it's local bvec list (svc_tcp_sendmsg).
