On Fri, Sep 10, 2021 at 10:31:00AM -0700, Linus Torvalds wrote: > On Fri, Sep 10, 2021 at 10:26 AM Jens Axboe <axboe@xxxxxxxxx> wrote: > > > > On 9/10/21 10:58 AM, Linus Torvalds wrote: > > > On Fri, Sep 10, 2021 at 9:56 AM Al Viro <viro@xxxxxxxxxxxxxxxxxx> wrote: > > >> > > >> What's the point of all those contortions, anyway? You only need it for > > >> iovec case; don't mix doing that and turning it into flavour-independent > > >> primitive. > > > > > > Good point, making it specific to iovec only gets rid of a lot of > > > special cases and worries. > > > > > > This is fairly specialized, no need to always cater to every possible case. > > > > Alright, split into three patches: > > > > https://git.kernel.dk/cgit/linux-block/log/?h=iov_iter > > That looks sane to me. > > Please add some comment about how that > > i->iov -= state->nr_segs - i->nr_segs; > > actually is the right thing for all the three cases (iow how 'iov', > 'kvec' and 'bvec' all end up having a union member that acts the same > way). > > But yeah, I like how the io_uring.c code looks better this way too. > > Al, what do you think? I think that sizeof(struct bio_vec) != sizeof(struct iovec): struct bio_vec { struct page *bv_page; unsigned int bv_len; unsigned int bv_offset; }; takes 3 words on 32bit boxen. struct iovec { void __user *iov_base; /* BSD uses caddr_t (1003.1g requires void *) */ __kernel_size_t iov_len; /* Must be size_t (1003.1g) */ }; takes 2 words on 32bit boxen.
