On Thu, Nov 19, 2020 at 11:24:38PM +0000, Pavel Begunkov wrote: > The block layer spends quite a while in iov_iter_npages(), but for the > bvec case the number of pages is already known and stored in > iter->nr_segs, so it can be returned immediately as an optimisation Er ... no, it doesn't. nr_segs is the number of bvecs. Each bvec can store up to 4GB of contiguous physical memory.
