On Wed, 2022-06-22 at 05:15 +0100, Al Viro wrote:
> same as for pipes and xarrays; after that iov_iter_get_pages() becomes
> a wrapper for __iov_iter_get_pages_alloc().
>
> Signed-off-by: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
> ---
> lib/iov_iter.c | 86 ++++++++++++++++----------------------------------
> 1 file changed, 28 insertions(+), 58 deletions(-)
>
> diff --git a/lib/iov_iter.c b/lib/iov_iter.c
> index 07dacb274ba5..811fa09515d8 100644
> --- a/lib/iov_iter.c
> +++ b/lib/iov_iter.c
> @@ -1372,20 +1372,19 @@ static struct page *first_bvec_segment(const struct iov_iter *i,
> return page;
> }
>
> -ssize_t iov_iter_get_pages(struct iov_iter *i,
> - struct page **pages, size_t maxsize, unsigned maxpages,
> - size_t *start)
> +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)
> maxsize = i->count;
> - if (!maxsize || !maxpages)
> + if (!maxsize)
> return 0;
> if (maxsize > MAX_RW_COUNT)
> maxsize = MAX_RW_COUNT;
> - BUG_ON(!pages);
>
> if (likely(user_backed_iter(i))) {
> unsigned int gup_flags = 0;
> @@ -1398,80 +1397,51 @@ ssize_t iov_iter_get_pages(struct iov_iter *i,
>
> addr = first_iovec_segment(i, &len, start, maxsize, maxpages);
> n = DIV_ROUND_UP(len, PAGE_SIZE);
> - res = get_user_pages_fast(addr, n, gup_flags, pages);
> + if (!*pages) {
> + *pages = get_pages_array(n);
> + if (!*pages)
> + return -ENOMEM;
> + }
> + res = get_user_pages_fast(addr, n, gup_flags, *pages);
> if (unlikely(res <= 0))
> return res;
> return (res == n ? len : res * PAGE_SIZE) - *start;
> }
> if (iov_iter_is_bvec(i)) {
> + struct page **p;
> struct page *page;
>
> page = first_bvec_segment(i, &len, start, maxsize, maxpages);
> n = DIV_ROUND_UP(len, PAGE_SIZE);
> + p = *pages;
> + if (!p) {
> + *pages = p = get_pages_array(n);
> + if (!p)
> + return -ENOMEM;
> + }
> while (n--)
> - get_page(*pages++ = page++);
> + get_page(*p++ = page++);
> return len - *start;
> }
> if (iov_iter_is_pipe(i))
> - return pipe_get_pages(i, &pages, maxsize, maxpages, start);
> + return pipe_get_pages(i, pages, maxsize, maxpages, start);
> if (iov_iter_is_xarray(i))
> - return iter_xarray_get_pages(i, &pages, maxsize, maxpages, start);
> + return iter_xarray_get_pages(i, pages, maxsize, maxpages,
> + start);
> return -EFAULT;
> }
> -EXPORT_SYMBOL(iov_iter_get_pages);
>
> -static ssize_t __iov_iter_get_pages_alloc(struct iov_iter *i,
> - struct page ***pages, size_t maxsize,
> +ssize_t iov_iter_get_pages(struct iov_iter *i,
> + struct page **pages, size_t maxsize, unsigned maxpages,
> size_t *start)
> {
> - struct page **p;
> - size_t len;
> - int n, res;
> -
> - if (maxsize > i->count)
> - maxsize = i->count;
> - if (!maxsize)
> + if (!maxpages)
> return 0;
> - if (maxsize > MAX_RW_COUNT)
> - maxsize = MAX_RW_COUNT;
> -
> - if (likely(user_backed_iter(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, ~0U);
> - n = DIV_ROUND_UP(len, PAGE_SIZE);
> - *pages = p = get_pages_array(n);
> - if (!p)
> - return -ENOMEM;
> - res = get_user_pages_fast(addr, n, gup_flags, p);
> - if (unlikely(res <= 0))
> - return res;
> - return (res == n ? len : res * PAGE_SIZE) - *start;
> - }
> - if (iov_iter_is_bvec(i)) {
> - struct page *page;
> + BUG_ON(!pages);
>
> - page = first_bvec_segment(i, &len, start, maxsize, ~0U);
> - n = DIV_ROUND_UP(len, PAGE_SIZE);
> - *pages = p = get_pages_array(n);
> - if (!p)
> - return -ENOMEM;
> - while (n--)
> - get_page(*p++ = page++);
> - return len - *start;
> - }
> - if (iov_iter_is_pipe(i))
> - return pipe_get_pages(i, pages, maxsize, ~0U, start);
> - if (iov_iter_is_xarray(i))
> - return iter_xarray_get_pages(i, pages, maxsize, ~0U, start);
> - return -EFAULT;
> + return __iov_iter_get_pages_alloc(i, &pages, maxsize, maxpages, start);
> }
> +EXPORT_SYMBOL(iov_iter_get_pages);
>
> ssize_t iov_iter_get_pages_alloc(struct iov_iter *i,
> struct page ***pages, size_t maxsize,
> @@ -1481,7 +1451,7 @@ ssize_t iov_iter_get_pages_alloc(struct iov_iter *i,
>
> *pages = NULL;
>
> - len = __iov_iter_get_pages_alloc(i, pages, maxsize, start);
> + len = __iov_iter_get_pages_alloc(i, pages, maxsize, ~0U, start);
> if (len <= 0) {
> kvfree(*pages);
> *pages = NULL;
Reviewed-by: Jeff Layton <jlayton@xxxxxxxxxx>
