ssize_t default_file_splice_read(struct file *in, loff_t *ppos,
				 struct pipe_inode_info *pipe, size_t len,
				 unsigned int flags)
{
	unsigned int nr_pages;
	unsigned int nr_freed;
	size_t offset;
	struct page *pages[PIPE_DEF_BUFFERS];
	struct partial_page partial[PIPE_DEF_BUFFERS];
	struct iovec *vec, __vec[PIPE_DEF_BUFFERS];
	ssize_t res;
	size_t this_len;
	int error;
	int i;
	struct splice_pipe_desc spd = {
		.pages = pages,
		.partial = partial,
		.nr_pages_max = PIPE_DEF_BUFFERS,
		.flags = flags,
		.ops = &default_pipe_buf_ops,
		.spd_release = spd_release_page,
	};

	if (splice_grow_spd(pipe, &spd))
		return -ENOMEM;

	res = -ENOMEM;
	vec = __vec;
	if (spd.nr_pages_max > PIPE_DEF_BUFFERS) {
		vec = kmalloc(spd.nr_pages_max * sizeof(struct iovec), GFP_KERNEL);
		if (!vec)
			goto shrink_ret;
	}

	offset = *ppos & ~PAGE_CACHE_MASK;
	nr_pages = (len + offset + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;

	for (i = 0; i < nr_pages && i < spd.nr_pages_max && len; i++) {
		struct page *page;

		page = alloc_page(GFP_USER);
		error = -ENOMEM;
		if (!page)
			goto err;

		this_len = min_t(size_t, len, PAGE_CACHE_SIZE - offset);
		vec[i].iov_base = (void __user *) page_address(page);
		vec[i].iov_len = this_len;
		spd.pages[i] = page;
		spd.nr_pages++;
		len -= this_len;
		offset = 0;
	}

	res = kernel_readv(in, vec, spd.nr_pages, *ppos);
	if (res < 0) {
		error = res;
		goto err;
	}

	error = 0;
	if (!res)
		goto err;

	nr_freed = 0;
	for (i = 0; i < spd.nr_pages; i++) {
		this_len = min_t(size_t, vec[i].iov_len, res);
		spd.partial[i].offset = 0;
		spd.partial[i].len = this_len;
		if (!this_len) {
			__free_page(spd.pages[i]);
			spd.pages[i] = NULL;
			nr_freed++;
		}
		res -= this_len;
	}
	spd.nr_pages -= nr_freed;

	res = splice_to_pipe(pipe, &spd);
	if (res > 0)
		*ppos += res;

shrink_ret:
	if (vec != __vec)
		kfree(vec);
	splice_shrink_spd(&spd);
	return res;

err:
	for (i = 0; i < spd.nr_pages; i++)
		__free_page(spd.pages[i]);

	res = error;
	goto shrink_ret;
}
ssize_t default_file_splice_read(struct file *in, loff_t *ppos,
				 struct pipe_inode_info *pipe, size_t len,
				 unsigned int flags)
{
	unsigned int nr_pages;
	unsigned int nr_freed;
	size_t offset;
	struct page *pages[PIPE_DEF_BUFFERS];
	struct partial_page partial[PIPE_DEF_BUFFERS];
	struct iovec *vec, __vec[PIPE_DEF_BUFFERS];
	ssize_t res;
	size_t this_len;
	int error;
	int i;
	struct splice_pipe_desc spd = {
		.pages = pages,
		.partial = partial,
		.nr_pages_max = PIPE_DEF_BUFFERS,
		.flags = flags,
		.ops = &default_pipe_buf_ops,
		.spd_release = spd_release_page,
	};

	if (splice_grow_spd(pipe, &spd))
		return -ENOMEM;

	res = -ENOMEM;
	vec = __vec;
	if (spd.nr_pages_max > PIPE_DEF_BUFFERS) {
		vec = kmalloc(spd.nr_pages_max * sizeof(struct iovec), GFP_KERNEL);
		if (!vec)
			goto shrink_ret;
	}

	offset = *ppos & ~PAGE_CACHE_MASK;
	nr_pages = (len + offset + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;

	for (i = 0; i < nr_pages && i < spd.nr_pages_max && len; i++) {
		struct page *page;

		page = alloc_page(GFP_USER);
		error = -ENOMEM;
		if (!page)
			goto err;

		this_len = min_t(size_t, len, PAGE_CACHE_SIZE - offset);
		vec[i].iov_base = (void __user *) page_address(page);
		vec[i].iov_len = this_len;
		spd.pages[i] = page;
		spd.nr_pages++;
		len -= this_len;
		offset = 0;
	}

	res = kernel_readv(in, vec, spd.nr_pages, *ppos);
	if (res < 0) {
		error = res;
		goto err;
	}

	error = 0;
	if (!res)
		goto err;

	nr_freed = 0;
	for (i = 0; i < spd.nr_pages; i++) {
		this_len = min_t(size_t, vec[i].iov_len, res);
		spd.partial[i].offset = 0;
		spd.partial[i].len = this_len;
		if (!this_len) {
			__free_page(spd.pages[i]);
			spd.pages[i] = NULL;
			nr_freed++;
		}
		res -= this_len;
	}
	spd.nr_pages -= nr_freed;

	res = splice_to_pipe(pipe, &spd);
	if (res > 0)
		*ppos += res;

shrink_ret:
	if (vec != __vec)
		kfree(vec);
	splice_shrink_spd(&spd);
	return res;

err:
	for (i = 0; i < spd.nr_pages; i++)
		__free_page(spd.pages[i]);

	res = error;
	goto shrink_ret;
}