Wait, I see that the bvec is still a single array per bio. When you said a table I thought you meant a 2-dimentional array...I mean a new 1-d table A has to be created for multiple bios in one rq, and build it in the following way rq_for_each_bvec(tmp, rq, rq_iter) *A = tmp; Then you can pass A to iov_iter_bvec() & send(). Given it is over TCP, I guess it should be doable for you to preallocate one 256-bvec table in one page for each request, then sets the max segment size as (unsigned int)-1, and max segment number as 256, the preallocated table should work anytime.
256 bvec table is really a lot to preallocate, especially when its not needed, I can easily initialize the bvec_iter on the bio bvec. If this involves preallocation of the worst-case than I don't consider this to be an improvement.
