On Wed, 2022-06-22 at 05:15 +0100, Al Viro wrote:
> Pass maxsize by reference, return length via the same.
>
> Signed-off-by: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
> ---
> lib/iov_iter.c | 37 +++++++++++++++----------------------
> 1 file changed, 15 insertions(+), 22 deletions(-)
>
> diff --git a/lib/iov_iter.c b/lib/iov_iter.c
> index 0bed684d91d0..fca66ecce7a0 100644
> --- a/lib/iov_iter.c
> +++ b/lib/iov_iter.c
> @@ -1306,26 +1306,22 @@ static ssize_t iter_xarray_get_pages(struct iov_iter *i,
> return min_t(size_t, nr * PAGE_SIZE - offset, maxsize);
> }
>
> -static unsigned long found_ubuf_segment(unsigned long addr,
> - size_t len,
> - size_t *size, size_t *start)
> +static unsigned long found_ubuf_segment(unsigned long addr, size_t *start)
> {
> *start = addr % PAGE_SIZE;
> - *size = len;
> return addr & PAGE_MASK;
> }
>
> /* must be done on non-empty ITER_UBUF or ITER_IOVEC one */
> static unsigned long first_iovec_segment(const struct iov_iter *i,
> - size_t *size, size_t *start,
> - size_t maxsize)
> + size_t *size, size_t *start)
> {
> size_t skip;
> long k;
>
> if (iter_is_ubuf(i)) {
> unsigned long addr = (unsigned long)i->ubuf + i->iov_offset;
> - return found_ubuf_segment(addr, maxsize, size, start);
> + return found_ubuf_segment(addr, start);
> }
>
> for (k = 0, skip = i->iov_offset; k < i->nr_segs; k++, skip = 0) {
> @@ -1334,28 +1330,26 @@ static unsigned long first_iovec_segment(const struct iov_iter *i,
>
> if (unlikely(!len))
> continue;
> - if (len > maxsize)
> - len = maxsize;
> - return found_ubuf_segment(addr, len, size, start);
> + if (*size > len)
> + *size = len;
> + return found_ubuf_segment(addr, start);
> }
> BUG(); // if it had been empty, we wouldn't get called
> }
>
> /* must be done on non-empty ITER_BVEC one */
> static struct page *first_bvec_segment(const struct iov_iter *i,
> - size_t *size, size_t *start,
> - size_t maxsize)
> + size_t *size, size_t *start)
> {
> struct page *page;
> size_t skip = i->iov_offset, len;
>
> len = i->bvec->bv_len - skip;
> - if (len > maxsize)
> - len = maxsize;
> + if (*size > len)
> + *size = len;
> skip += i->bvec->bv_offset;
> page = i->bvec->bv_page + skip / PAGE_SIZE;
> *start = skip % PAGE_SIZE;
> - *size = len;
> return page;
> }
>
> @@ -1363,7 +1357,6 @@ static ssize_t __iov_iter_get_pages_alloc(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)
> @@ -1382,8 +1375,8 @@ static ssize_t __iov_iter_get_pages_alloc(struct iov_iter *i,
> if (i->nofault)
> gup_flags |= FOLL_NOFAULT;
>
> - addr = first_iovec_segment(i, &len, start, maxsize);
> - n = DIV_ROUND_UP(len + *start, PAGE_SIZE);
> + addr = first_iovec_segment(i, &maxsize, start);
> + n = DIV_ROUND_UP(maxsize + *start, PAGE_SIZE);
> if (n > maxpages)
> n = maxpages;
> if (!*pages) {
> @@ -1394,14 +1387,14 @@ static ssize_t __iov_iter_get_pages_alloc(struct iov_iter *i,
> res = get_user_pages_fast(addr, n, gup_flags, *pages);
> if (unlikely(res <= 0))
> return res;
> - return min_t(size_t, len, res * PAGE_SIZE - *start);
> + return min_t(size_t, maxsize, res * PAGE_SIZE - *start);
> }
> if (iov_iter_is_bvec(i)) {
> struct page **p;
> struct page *page;
>
> - page = first_bvec_segment(i, &len, start, maxsize);
> - n = DIV_ROUND_UP(len + *start, PAGE_SIZE);
> + page = first_bvec_segment(i, &maxsize, start);
> + n = DIV_ROUND_UP(maxsize + *start, PAGE_SIZE);
> if (n > maxpages)
> n = maxpages;
> p = *pages;
> @@ -1412,7 +1405,7 @@ static ssize_t __iov_iter_get_pages_alloc(struct iov_iter *i,
> }
> for (int k = 0; k < n; k++)
> get_page(*p++ = page++);
> - return min_t(size_t, len, n * PAGE_SIZE - *start);
> + return min_t(size_t, maxsize, n * PAGE_SIZE - *start);
> }
> if (iov_iter_is_pipe(i))
> return pipe_get_pages(i, pages, maxsize, maxpages, start);
Reviewed-by: Jeff Layton <jlayton@xxxxxxxxxx>
