[lvm-devel] [PATCH 01/22] Add dm_list_splice() for list join.

[Alasdair G Kergon]

On Mon, Apr 12, 2010 at 05:21:29PM +0200, Zdenek Kabelac wrote:
> Introduce dm_list_splice to join two lists.

OK, but do please retain the style and conventions of the existing functions.

> +void dm_list_splice(struct dm_list *list, struct dm_list *head)

Based on existing conventions, the code appears to implement:
  dm_list_splice_h(struct dm_list *head, struct dm_list *list)

Try the following (untested) instead:

/*
 * Join two lists together.
 * This moves all the elements of the list 'head1' to the end of the list
 * 'head', leaving 'head1' empty.
 */
void dm_list_splice(struct dm_list *head, struct dm_list *head1)
{
	assert(head->n);
	assert(head1->n);

	head1->p->n = head;
	head1->n->p = head->p;

	head->p->n = head1->n;
	head->p = head1->p;

	dm_list_init(head1);
}

Of if you genuinely require the _h version (i.e. the elements are ordered and
you can't choose to retain 'head1' for the combined list instead of 'head.)

/*
 * Join two lists together.
 * This moves all the elements of the list 'head1' to the front of the list
 * 'head', leaving 'head1' empty.
 */
void dm_list_splice_h(struct dm_list *head, struct dm_list *head1)
{
	assert(head->n);
	assert(head1->n);

	head1->n->p = head;
	head1->p->n = head->n;

	head->n->p = head1->p;
	head->n = head1->n;

	dm_list_init(head1);
}

Alasdair