/*
* klist.c - Routines for manipulating klists.
*
* Copyright (C) 2005 Patrick Mochel
*
* This file is released under the GPL v2.
*
* This klist interface provides a couple of structures that wrap around
* struct list_head to provide explicit list "head" (struct klist) and list
* "node" (struct klist_node) objects. For struct klist, a spinlock is
* included that protects access to the actual list itself. struct
* klist_node provides a pointer to the klist that owns it and a kref
* reference count that indicates the number of current users of that node
* in the list.
*
* The entire point is to provide an interface for iterating over a list
* that is safe and allows for modification of the list during the
* iteration (e.g. insertion and removal), including modification of the
* current node on the list.
*
* It works using a 3rd object type - struct klist_iter - that is declared
* and initialized before an iteration. klist_next() is used to acquire the
* next element in the list. It returns NULL if there are no more items.
* Internally, that routine takes the klist's lock, decrements the
* reference count of the previous klist_node and increments the count of
* the next klist_node. It then drops the lock and returns.
*
* There are primitives for adding and removing nodes to/from a klist.
* When deleting, klist_del() will simply decrement the reference count.
* Only when the count goes to 0 is the node removed from the list.
* klist_remove() will try to delete the node from the list and block until
* it is actually removed. This is useful for objects (like devices) that
* have been removed from the system and must be freed (but must wait until
* all accessors have finished).
*/
#include <linux/klist.h>
#include <linux/module.h>
/**
* klist_init - Initialize a klist structure.
* @k: The klist we're initializing.
* @get: The get function for the embedding object (NULL if none)
* @put: The put function for the embedding object (NULL if none)
*
* Initialises the klist structure. If the klist_node structures are
* going to be embedded in refcounted objects (necessary for safe
* deletion) then the get/put arguments are used to initialise
* functions that take and release references on the embedding
* objects.
*/
void klist_init(struct klist *k, void (*get)(struct klist_node *),
void (*put)(struct klist_node *))
{
INIT_LIST_HEAD(&k->k_list);
spin_lock_init(&k->k_lock);
k->get = get;
k->put = put;
}
EXPORT_SYMBOL_GPL(klist_init);
static void add_head(struct klist *k, struct klist_node *n)
{
spin_lock(&k->k_lock);
list_add(&n->n_node, &k->k_list);
spin_unlock(&k->k_lock);
}
static void add_tail(struct klist *k, struct klist_node *n)
{
spin_lock(&k->k_lock);
list_add_tail(&n->n_node, &k->k_list);
spin_unlock(&k->k_lock);
}
static void klist_node_init(struct klist *k, struct klist_node *n)
{
INIT_LIST_HEAD(&n->n_node);
init_completion(&n->n_removed);
kref_init(&n->n_ref);
n->n_klist = k;
if (k->get)
k->get(n);
}
/**
* klist_add_head - Initialize a klist_node and add it to front.
* @n: node we're adding.
* @k: klist it's going on.
*/
void klist_add_head(struct klist_node *n, struct klist *k)
{
klist_node_init(k, n);
add_head(k, n);
}
EXPORT_SYMBOL_GPL(klist_add_head);
/**
* klist_add_tail - Initialize a klist_node and add it to back.
* @n: node we're adding.
* @k: klist it's going on.
*/
void klist_add_tail(struct klist_node *n, struct klist *k)
{
klist_node_init(k, n);
add_tail(k, n);
}
EXPORT_SYMBOL_GPL(klist_add_tail);
/**
* klist_add_after - Init a klist_node and add it after an existing node
* @n: node we're adding.
* @pos: node to put @n after
*/
void klist_add_after(struct klist_node *n, struct klist_node *pos)
{
struct klist *k = pos->n_klist;
klist_node_init(k, n);
spin_lock(&k->k_lock);
list_add(&n->n_node, &pos->n_node);
spin_unlock(&k->k_lock);
}
EXPORT_SYMBOL_GPL(klist_add_after);
/**
* klist_add_before - Init a klist_node and add it before an existing node
* @n: node we're adding.
* @pos: node to put @n after
*/
void klist_add_before(struct klist_node *n, struct klist_node *pos)
{
struct klist *k = pos->n_klist;
klist_node_init(k, n);
spin_lock(&k->k_lock);
list_add_tail(&n->n_node, &pos->n_node);
spin_unlock(&k->k_lock);
}
EXPORT_SYMBOL_GPL(klist_add_before);
static void klist_release(struct kref *kref)
{
struct klist_node *n = container_of(kref, struct klist_node, n_ref);
list_del(&n->n_node);
complete(&n->n_removed);
n->n_klist = NULL;
}
static int klist_dec_and_del(struct klist_node *n)
{
return kref_put(&n->n_ref, klist_release);
}
/**
* klist_del - Decrement the reference count of node and try to remove.
* @n: node we're deleting.
*/
void klist_del(struct klist_node *n)
{
struct klist *k = n->n_klist;
void (*put)(struct klist_node *) = k->put;
spin_lock(&k->k_lock);
if (!klist_dec_and_del(n))
put = NULL;
spin_unlock(&k->k_lock);
if (put)
put(n);
}
EXPORT_SYMBOL_GPL(klist_del);
/**
* klist_remove - Decrement the refcount of node and wait for it to go away.
* @n: node we're removing.
*/
void klist_remove(struct klist_node *n)
{
klist_del(n);
wait_for_completion(&n->n_removed);
}
EXPORT_SYMBOL_GPL(klist_remove);
/**
* klist_node_attached - Say whether a node is bound to a list or not.
* @n: Node that we're testing.
*/
int klist_node_attached(struct klist_node *n)
{
return (n->n_klist != NULL);
}
EXPORT_SYMBOL_GPL(klist_node_attached);
/**
* klist_iter_init_node - Initialize a klist_iter structure.
* @k: klist we're iterating.
* @i: klist_iter we're filling.
* @n: node to start with.
*
* Similar to klist_iter_init(), but starts the action off with @n,
* instead of with the list head.
*/
void klist_iter_init_node(struct klist *k, struct klist_iter *i,
struct klist_node *n)
{
i->i_klist = k;
i->i_head = &k->k_list;
i->i_cur = n;
if (n)
kref_get(&n->n_ref);
}
EXPORT_SYMBOL_GPL(klist_iter_init_node);
/**
* klist_iter_init - Iniitalize a klist_iter structure.
* @k: klist we're iterating.
* @i: klist_iter structure we're filling.
*
* Similar to klist_iter_init_node(), but start with the list head.
*/
void klist_iter_init(struct klist *k, struct klist_iter *i)
{
klist_iter_init_node(k, i, NULL);
}
EXPORT_SYMBOL_GPL(klist_iter_init);
/**
* klist_iter_exit - Finish a list iteration.
* @i: Iterator structure.
*
* Must be called when done iterating over list, as it decrements the
* refcount of the current node. Necessary in case iteration exited before
* the end of the list was reached, and always good form.
*/
void klist_iter_exit(struct klist_iter *i)
{
if (i->i_cur) {
klist_del(i->i_cur);
i->i_cur = NULL;
}
}
EXPORT_SYMBOL_GPL(klist_iter_exit);
static struct klist_node *to_klist_node(struct list_head *n)
{
return container_of(n, struct klist_node, n_node);
}
/**
* klist_next - Ante up next node in list.
* @i: Iterator structure.
*
* First grab list lock. Decrement the reference count of the previous
* node, if there was one. Grab the next node, increment its reference
* count, drop the lock, and return that next node.
*/
struct klist_node *klist_next(struct klist_iter *i)
{
struct list_head *next;
struct klist_node *lnode = i->i_cur;
struct klist_node *knode = NULL;
void (*put)(struct klist_node *) = i->i_klist->put;
spin_lock(&i->i_klist->k_lock);
if (lnode) {
next = lnode->n_node.next;
if (!klist_dec_and_del(lnode))
put = NULL;
} else
next = i->i_head->next;
if (next != i->i_head) {
knode = to_klist_node(next);
kref_get(&knode->n_ref);
}
i->i_cur = knode;
spin_unlock(&i->i_klist->k_lock);
if (put && lnode)
put(lnode);
return knode;
}
EXPORT_SYMBOL_GPL(klist_next);
