VFS: Add iov_iter_fault_in_multipages_readable()

		struct iov_iter *i, unsigned long offset, size_t bytes);

void iov_iter_advance(struct iov_iter *i, size_t bytes);

int iov_iter_fault_in_readable(struct iov_iter *i, size_t bytes);

int iov_iter_fault_in_multipages_readable(struct iov_iter *i, size_t bytes);

size_t iov_iter_single_seg_count(const struct iov_iter *i);

size_t copy_page_to_iter(struct page *page, size_t offset, size_t bytes,

			 struct iov_iter *i);

}

EXPORT_SYMBOL(iov_iter_fault_in_readable);

/*

 * Fault in one or more iovecs of the given iov_iter, to a maximum length of

 * bytes.  For each iovec, fault in each page that constitutes the iovec.

 *

 * Return 0 on success, or non-zero if the memory could not be accessed (i.e.

 * because it is an invalid address).

 */

int iov_iter_fault_in_multipages_readable(struct iov_iter *i, size_t bytes)

{

	size_t skip = i->iov_offset;

	const struct iovec *iov;

	int err;

	struct iovec v;

	if (!(i->type & (ITER_BVEC|ITER_KVEC))) {

		iterate_iovec(i, bytes, v, iov, skip, ({

			err = fault_in_multipages_readable(v.iov_base,

					v.iov_len);

			if (unlikely(err))

			return err;

		0;}))

	}

	return 0;

}

EXPORT_SYMBOL(iov_iter_fault_in_multipages_readable);

void iov_iter_init(struct iov_iter *i, int direction,

			const struct iovec *iov, unsigned long nr_segs,

			size_t count)