Commit 185ac4d4 authored by Al Viro's avatar Al Viro
Browse files

iov_iter: optimize iov_iter_advance() for iovec and kvec 



We can do better than generic iterate_and_advance() for this one;
inspired by bvec_iter_advance() (and massaged into that form by
equivalent transformations).

[fixed a braino caught by kernel test robot <oliver.sang@intel.com>]

Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
parent 8cd54c1c

lib/iov_iter.c

+28 −14
Original line number Diff line number Diff line
@@ -1096,28 +1096,42 @@ static void iov_iter_bvec_advance(struct iov_iter *i, size_t size) 
	i->iov_offset = bi.bi_bvec_done;

}



static void iov_iter_iovec_advance(struct iov_iter *i, size_t size)

{

	const struct iovec *iov, *end;



	if (!i->count)

		return;

	i->count -= size;



	size += i->iov_offset; // from beginning of current segment

	for (iov = i->iov, end = iov + i->nr_segs; iov < end; iov++) {

		if (likely(size < iov->iov_len))

			break;

		size -= iov->iov_len;

	}

	i->iov_offset = size;

	i->nr_segs -= iov - i->iov;

	i->iov = iov;

}



void iov_iter_advance(struct iov_iter *i, size_t size)

{

	if (unlikely(i->count < size))

		size = i->count;

	if (unlikely(iov_iter_is_pipe(i))) {

	if (likely(iter_is_iovec(i) || iov_iter_is_kvec(i))) {

		/* iovec and kvec have identical layouts */

		iov_iter_iovec_advance(i, size);

	} else if (iov_iter_is_bvec(i)) {

		iov_iter_bvec_advance(i, size);

	} else if (iov_iter_is_pipe(i)) {

		pipe_advance(i, size);

		return;

	}

	if (unlikely(iov_iter_is_discard(i))) {

		i->count -= size;

		return;

	}

	if (unlikely(iov_iter_is_xarray(i))) {

	} else if (unlikely(iov_iter_is_xarray(i))) {

		i->iov_offset += size;

		i->count -= size;

		return;

	}

	if (iov_iter_is_bvec(i)) {

		iov_iter_bvec_advance(i, size);

		return;

	} else if (iov_iter_is_discard(i)) {

		i->count -= size;

	}

	iterate_and_advance(i, size, v, 0, 0, 0, 0)

}

EXPORT_SYMBOL(iov_iter_advance);