On Wed, 2022-06-22 at 05:15 +0100, Al Viro wrote:
> ... doing revert if we end up not using some pages
>
> Signed-off-by: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
> ---
> block/bio.c | 15 ++++++---------
> block/blk-map.c | 7 ++++---
> 2 files changed, 10 insertions(+), 12 deletions(-)
>
> diff --git a/block/bio.c b/block/bio.c
> index 51c99f2c5c90..01ab683e67be 100644
> --- a/block/bio.c
> +++ b/block/bio.c
> @@ -1190,7 +1190,7 @@ static int __bio_iov_iter_get_pages(struct bio *bio, struct iov_iter *iter)
> BUILD_BUG_ON(PAGE_PTRS_PER_BVEC < 2);
> pages += entries_left * (PAGE_PTRS_PER_BVEC - 1);
>
> - size = iov_iter_get_pages(iter, pages, LONG_MAX, nr_pages, &offset);
> + size = iov_iter_get_pages2(iter, pages, LONG_MAX, nr_pages, &offset);
> if (unlikely(size <= 0))
> return size ? size : -EFAULT;
>
> @@ -1205,6 +1205,7 @@ static int __bio_iov_iter_get_pages(struct bio *bio, struct iov_iter *iter)
> } else {
> if (WARN_ON_ONCE(bio_full(bio, len))) {
> bio_put_pages(pages + i, left, offset);
> + iov_iter_revert(iter, left);
> return -EINVAL;
> }
> __bio_add_page(bio, page, len, offset);
> @@ -1212,7 +1213,6 @@ static int __bio_iov_iter_get_pages(struct bio *bio, struct iov_iter *iter)
> offset = 0;
> }
>
> - iov_iter_advance(iter, size);
> return 0;
> }
>
> @@ -1227,7 +1227,6 @@ static int __bio_iov_append_get_pages(struct bio *bio, struct iov_iter *iter)
> ssize_t size, left;
> unsigned len, i;
> size_t offset;
> - int ret = 0;
>
> if (WARN_ON_ONCE(!max_append_sectors))
> return 0;
> @@ -1240,7 +1239,7 @@ static int __bio_iov_append_get_pages(struct bio *bio, struct iov_iter *iter)
> BUILD_BUG_ON(PAGE_PTRS_PER_BVEC < 2);
> pages += entries_left * (PAGE_PTRS_PER_BVEC - 1);
>
> - size = iov_iter_get_pages(iter, pages, LONG_MAX, nr_pages, &offset);
> + size = iov_iter_get_pages2(iter, pages, LONG_MAX, nr_pages, &offset);
> if (unlikely(size <= 0))
> return size ? size : -EFAULT;
>
> @@ -1252,16 +1251,14 @@ static int __bio_iov_append_get_pages(struct bio *bio, struct iov_iter *iter)
> if (bio_add_hw_page(q, bio, page, len, offset,
> max_append_sectors, &same_page) != len) {
> bio_put_pages(pages + i, left, offset);
> - ret = -EINVAL;
> - break;
> + iov_iter_revert(iter, left);
> + return -EINVAL;
> }
> if (same_page)
> put_page(page);
> offset = 0;
> }
> -
> - iov_iter_advance(iter, size - left);
> - return ret;
> + return 0;
> }
>
> /**
> diff --git a/block/blk-map.c b/block/blk-map.c
> index df8b066cd548..7196a6b64c80 100644
> --- a/block/blk-map.c
> +++ b/block/blk-map.c
> @@ -254,7 +254,7 @@ static int bio_map_user_iov(struct request *rq, struct iov_iter *iter,
> size_t offs, added = 0;
> int npages;
>
> - bytes = iov_iter_get_pages_alloc(iter, &pages, LONG_MAX, &offs);
> + bytes = iov_iter_get_pages_alloc2(iter, &pages, LONG_MAX, &offs);
> if (unlikely(bytes <= 0)) {
> ret = bytes ? bytes : -EFAULT;
> goto out_unmap;
> @@ -284,7 +284,6 @@ static int bio_map_user_iov(struct request *rq, struct iov_iter *iter,
> bytes -= n;
> offs = 0;
> }
> - iov_iter_advance(iter, added);
> }
> /*
> * release the pages we didn't map into the bio, if any
> @@ -293,8 +292,10 @@ static int bio_map_user_iov(struct request *rq, struct iov_iter *iter,
> put_page(pages[j++]);
> kvfree(pages);
> /* couldn't stuff something into bio? */
> - if (bytes)
> + if (bytes) {
> + iov_iter_revert(iter, bytes);
> break;
> + }
> }
>
> ret = blk_rq_append_bio(rq, bio);
Reviewed-by: Jeff Layton <jlayton@xxxxxxxxxx>
