On Fri, Sep 10, 2021 at 12:25:34PM -0600, Jens Axboe wrote:
> +void iov_iter_restore(struct iov_iter *i, struct iov_iter_state *state,
> + ssize_t did_bytes)
> +{
> + if (WARN_ON_ONCE(!iov_iter_is_bvec(i) && !iter_is_iovec(i)) &&
> + !iov_iter_is_kvec(i))
> + return;
> + i->iov_offset = state->iov_offset;
> + i->count = state->count;
> + /*
> + * For the *vec iters, nr_segs + iov is constant - if we increment
> + * the vec, then we also decrement the nr_segs count. Hence we don't
> + * need to track both of these, just one is enough and we can deduct
> + * the other from that. ITER_{BVEC,IOVEC,KVEC} all have their pointers
> + * unionized, so we don't need to handle them individually.
> + */
> + i->iov -= state->nr_segs - i->nr_segs;
> + i->nr_segs = state->nr_segs;
> +}
No. You can have iovec and kvec handled jointly (struct iovec and struct kvec
always have the same size). You can *not* do that to bvec - check sizeof of
struct bio_vec and struct iovec on 32bit targets.
