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

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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: NeilBrown <neilb@suse.de>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
This commit is contained in:
NeilBrown 2023-09-11 10:39:24 -04:00 committed by Chuck Lever
parent 2b65a22684
commit d6b3358a28
1 changed files with 42 additions and 0 deletions
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42
include/linux/llist.h
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@ -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 */