Commit d6b3358a authored by NeilBrown's avatar NeilBrown Committed by Chuck Lever
Browse files

llist: add interface to check if a node is on a list. 



With list.h lists, it is easy to test if a node is on a list, providing
it was initialised and that it is removed with list_del_init().

This patch provides similar functionality for llist.h lists.

 init_llist_node()
marks a node as being not-on-any-list be setting the ->next pointer to
the node itself.
 llist_on_list()
tests if the node is on any list.
 llist_del_first_init()
remove the first element from a llist, and marks it as being off-list.

Signed-off-by: default avatarNeilBrown <neilb@suse.de>
Signed-off-by: default avatarChuck Lever <chuck.lever@oracle.com>
parent 2b65a226

include/linux/llist.h

+42 −0
Original line number Diff line number Diff line
@@ -73,6 +73,33 @@ static inline void init_llist_head(struct llist_head *list) 
	list->first = NULL;

}



/**

 * init_llist_node - initialize lock-less list node

 * @node:	the node to be initialised

 *

 * In cases where there is a need to test if a node is on

 * a list or not, this initialises the node to clearly

 * not be on any list.

 */

static inline void init_llist_node(struct llist_node *node)

{

	node->next = node;

}



/**

 * llist_on_list - test if a lock-list list node is on a list

 * @node:	the node to test

 *

 * When a node is on a list the ->next pointer will be NULL or

 * some other node.  It can never point to itself.  We use that

 * in init_llist_node() to record that a node is not on any list,

 * and here to test whether it is on any list.

 */

static inline bool llist_on_list(const struct llist_node *node)

{

	return node->next != node;

}



/**

 * llist_entry - get the struct of this entry

 * @ptr:	the &struct llist_node pointer.
@@ -249,6 +276,21 @@ static inline struct llist_node *__llist_del_all(struct llist_head *head) 


extern struct llist_node *llist_del_first(struct llist_head *head);



/**

 * llist_del_first_init - delete first entry from lock-list and mark is as being off-list

 * @head:	the head of lock-less list to delete from.

 *

 * This behave the same as llist_del_first() except that llist_init_node() is called

 * on the returned node so that llist_on_list() will report false for the node.

 */

static inline struct llist_node *llist_del_first_init(struct llist_head *head)

{

	struct llist_node *n = llist_del_first(head);



	if (n)

		init_llist_node(n);

	return n;

}

struct llist_node *llist_reverse_order(struct llist_node *head);



#endif /* LLIST_H */