On Wed, 2022-06-22 at 05:15 +0100, Al Viro wrote:
> The differences between those two are
> * pipe_get_pages() gets a non-NULL struct page ** value pointing to
> preallocated array + array size.
> * pipe_get_pages_alloc() gets an address of struct page ** variable that
> contains NULL, allocates the array and (on success) stores its address in
> that variable.
>
> Not hard to combine - always pass struct page ***, have
> the previous pipe_get_pages_alloc() caller pass ~0U as cap for
> array size.
>
> Signed-off-by: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
> ---
> lib/iov_iter.c | 49 +++++++++++++++++--------------------------------
> 1 file changed, 17 insertions(+), 32 deletions(-)
>
> diff --git a/lib/iov_iter.c b/lib/iov_iter.c
> index 5c985cf2858e..1c98f2f3a581 100644
> --- a/lib/iov_iter.c
> +++ b/lib/iov_iter.c
> @@ -1187,6 +1187,11 @@ unsigned long iov_iter_gap_alignment(const struct iov_iter *i)
> }
> EXPORT_SYMBOL(iov_iter_gap_alignment);
>
> +static struct page **get_pages_array(size_t n)
> +{
> + return kvmalloc_array(n, sizeof(struct page *), GFP_KERNEL);
> +}
> +
> static inline ssize_t __pipe_get_pages(struct iov_iter *i,
> size_t maxsize,
> struct page **pages,
> @@ -1220,10 +1225,11 @@ static inline ssize_t __pipe_get_pages(struct iov_iter *i,
> }
>
> static ssize_t pipe_get_pages(struct iov_iter *i,
> - struct page **pages, size_t maxsize, unsigned maxpages,
> + struct page ***pages, size_t maxsize, unsigned maxpages,
> size_t *start)
> {
> unsigned int npages, off;
> + struct page **p;
> size_t capacity;
>
> if (!sanity(i))
> @@ -1231,8 +1237,15 @@ static ssize_t pipe_get_pages(struct iov_iter *i,
>
> *start = off = pipe_npages(i, &npages);
> capacity = min(npages, maxpages) * PAGE_SIZE - off;
> + maxsize = min(maxsize, capacity);
> + p = *pages;
> + if (!p) {
> + *pages = p = get_pages_array(DIV_ROUND_UP(maxsize + off, PAGE_SIZE));
> + if (!p)
> + return -ENOMEM;
> + }
>
> - return __pipe_get_pages(i, min(maxsize, capacity), pages, off);
> + return __pipe_get_pages(i, maxsize, p, off);
> }
>
> static ssize_t iter_xarray_populate_pages(struct page **pages, struct xarray *xa,
> @@ -1394,41 +1407,13 @@ ssize_t iov_iter_get_pages(struct iov_iter *i,
> 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 -EFAULT;
> }
> EXPORT_SYMBOL(iov_iter_get_pages);
>
> -static struct page **get_pages_array(size_t n)
> -{
> - return kvmalloc_array(n, sizeof(struct page *), GFP_KERNEL);
> -}
> -
> -static ssize_t pipe_get_pages_alloc(struct iov_iter *i,
> - struct page ***pages, size_t maxsize,
> - size_t *start)
> -{
> - struct page **p;
> - unsigned int npages, off;
> - ssize_t n;
> -
> - if (!sanity(i))
> - return -EFAULT;
> -
> - *start = off = pipe_npages(i, &npages);
> - n = npages * PAGE_SIZE - off;
> - if (maxsize > n)
> - maxsize = n;
> - else
> - npages = DIV_ROUND_UP(maxsize + off, PAGE_SIZE);
> - *pages = p = get_pages_array(npages);
> - if (!p)
> - return -ENOMEM;
> - return __pipe_get_pages(i, maxsize, p, off);
> -}
> -
> static ssize_t iter_xarray_get_pages_alloc(struct iov_iter *i,
> struct page ***pages, size_t maxsize,
> size_t *_start_offset)
> @@ -1511,7 +1496,7 @@ static ssize_t __iov_iter_get_pages_alloc(struct iov_iter *i,
> return len - *start;
> }
> if (iov_iter_is_pipe(i))
> - return pipe_get_pages_alloc(i, pages, maxsize, start);
> + return pipe_get_pages(i, pages, maxsize, ~0U, start);
> if (iov_iter_is_xarray(i))
> return iter_xarray_get_pages_alloc(i, pages, maxsize, start);
> return -EFAULT;
Reviewed-by: Jeff Layton <jlayton@xxxxxxxxxx>
