iov_iter: teach csum_and_copy_to_iter() to handle pipe-backed ones

	return bytes;

}

static size_t csum_and_copy_to_pipe_iter(const void *addr, size_t bytes,

				__wsum *csum, struct iov_iter *i)

{

	struct pipe_inode_info *pipe = i->pipe;

	size_t n, r;

	size_t off = 0;

	__wsum sum = *csum, next;

	int idx;

	if (!sanity(i))

		return 0;

	bytes = n = push_pipe(i, bytes, &idx, &r);

	if (unlikely(!n))

		return 0;

	for ( ; n; idx = next_idx(idx, pipe), r = 0) {

		size_t chunk = min_t(size_t, n, PAGE_SIZE - r);

		char *p = kmap_atomic(pipe->bufs[idx].page);

		next = csum_partial_copy_nocheck(addr, p + r, chunk, 0);

		sum = csum_block_add(sum, next, off);

		kunmap_atomic(p);

		i->idx = idx;

		i->iov_offset = r + chunk;

		n -= chunk;

		off += chunk;

		addr += chunk;

	}

	i->count -= bytes;

	*csum = sum;

	return bytes;

}

size_t _copy_to_iter(const void *addr, size_t bytes, struct iov_iter *i)

{

	const char *from = addr;

	const char *from = addr;

	__wsum sum, next;

	size_t off = 0;

	if (unlikely(iov_iter_is_pipe(i)))

		return csum_and_copy_to_pipe_iter(addr, bytes, csum, i);

	sum = *csum;

	if (unlikely(iov_iter_is_pipe(i) || iov_iter_is_discard(i))) {

	if (unlikely(iov_iter_is_discard(i))) {

		WARN_ON(1);	/* for now */

		return 0;

	}