On Wed, Jun 13, 2018 at 04:54:41AM -0400, Kent Overstreet wrote: > bi_size is not immutable though, it will usually be modified by drivers when you > submit a bio. > > I see what you're trying to do, but your approach is busted given the way the > block layer works today. You'd have to save bio->bi_iter before submitting the > bio and restore it afterwards for it to work. For bi_size, agreed this needs fixing. bi_sector is always restored already by the callers, and the remaining fields are zeroed by bio_reset, which does the right thing.