On Fri, Jul 01, 2022 at 11:53:44AM -0600, Keith Busch wrote:
> On Fri, Jul 01, 2022 at 06:40:40PM +0100, Al Viro wrote:
> > -static void bio_put_pages(struct page **pages, size_t size, size_t off)
> > -{
> > - size_t i, nr = DIV_ROUND_UP(size + (off & ~PAGE_MASK), PAGE_SIZE);
> > -
> > - for (i = 0; i < nr; i++)
> > - put_page(pages[i]);
> > -}
> > -
> > static int bio_iov_add_page(struct bio *bio, struct page *page,
> > unsigned int len, unsigned int offset)
> > {
> > @@ -1228,11 +1220,11 @@ static int __bio_iov_iter_get_pages(struct bio *bio, struct iov_iter *iter)
> > * the iov data will be picked up in the next bio iteration.
> > */
> > size = iov_iter_get_pages(iter, pages, LONG_MAX, nr_pages, &offset);
> > - if (size > 0)
> > - size = ALIGN_DOWN(size, bdev_logical_block_size(bio->bi_bdev));
> > if (unlikely(size <= 0))
> > return size ? size : -EFAULT;
> > + nr_pages = DIV_ROUND_UP(offset + size, PAGE_SIZE);
> >
> > + size = ALIGN_DOWN(size, bdev_logical_block_size(bio->bi_bdev));
>
> This isn't quite right. The result of the ALIGN_DOWN could be 0, so whatever
> page we got before would be leaked since unused pages are only released on an
> add_page error. I was about to reply with a patch that fixes this, but here's
> the one that I'm currently testing:
AFAICS, result is broken; you might end up consuming some data and leaving
iterator not advanced at all. With no way for the caller to tell which way it
went.
