Re: [PATCH 2/6] iov_iter: new iov_iter_pin_pages*(), for FOLL_PIN pages

Jens Axboe
2022-02-27T21:57:51Z

> +ssize_t iov_iter_pin_pages(struct iov_iter *i,
> + struct page **pages, size_t maxsize, unsigned int maxpages,
> + size_t *start)
> +{
> + size_t len;
> + int n, res;
> +
> + if (maxsize > i->count)
> + maxsize = i->count;
> + if (!maxsize)
> + return 0;
> +
> + WARN_ON_ONCE(!iter_is_iovec(i));
> +
> + if (likely(iter_is_iovec(i))) {
> + unsigned int gup_flags = 0;
> + unsigned long addr;
> +
> + if (iov_iter_rw(i) != WRITE)
> + gup_flags |= FOLL_WRITE;
> + if (i->nofault)
> + gup_flags |= FOLL_NOFAULT;
> +
> + addr = first_iovec_segment(i, &len, start, maxsize, maxpages);
> + n = DIV_ROUND_UP(len, PAGE_SIZE);
> + res = pin_user_pages_fast(addr, n, gup_flags, pages);
> + if (unlikely(res <= 0))
> + return res;
> + return (res == n ? len : res * PAGE_SIZE) - *start;

Trying to be clever like that just makes the code a lot less readable. I
should not have to reason about a return value. Same in the other
function.

--
Jens Axboe