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mochel@digitalimplant.org9a19fea2005-03-21 11:45:16 -08001/*
Greg Kroah-Hartmanc3bb7fad2008-04-30 16:43:45 -07002 * klist.c - Routines for manipulating klists.
mochel@digitalimplant.org9a19fea2005-03-21 11:45:16 -08003 *
Greg Kroah-Hartmanc3bb7fad2008-04-30 16:43:45 -07004 * Copyright (C) 2005 Patrick Mochel
mochel@digitalimplant.org9a19fea2005-03-21 11:45:16 -08005 *
Greg Kroah-Hartmanc3bb7fad2008-04-30 16:43:45 -07006 * This file is released under the GPL v2.
mochel@digitalimplant.org9a19fea2005-03-21 11:45:16 -08007 *
Greg Kroah-Hartmanc3bb7fad2008-04-30 16:43:45 -07008 * This klist interface provides a couple of structures that wrap around
9 * struct list_head to provide explicit list "head" (struct klist) and list
10 * "node" (struct klist_node) objects. For struct klist, a spinlock is
11 * included that protects access to the actual list itself. struct
12 * klist_node provides a pointer to the klist that owns it and a kref
13 * reference count that indicates the number of current users of that node
14 * in the list.
mochel@digitalimplant.org9a19fea2005-03-21 11:45:16 -080015 *
Greg Kroah-Hartmanc3bb7fad2008-04-30 16:43:45 -070016 * The entire point is to provide an interface for iterating over a list
17 * that is safe and allows for modification of the list during the
18 * iteration (e.g. insertion and removal), including modification of the
19 * current node on the list.
mochel@digitalimplant.org9a19fea2005-03-21 11:45:16 -080020 *
Greg Kroah-Hartmanc3bb7fad2008-04-30 16:43:45 -070021 * It works using a 3rd object type - struct klist_iter - that is declared
22 * and initialized before an iteration. klist_next() is used to acquire the
23 * next element in the list. It returns NULL if there are no more items.
24 * Internally, that routine takes the klist's lock, decrements the
25 * reference count of the previous klist_node and increments the count of
26 * the next klist_node. It then drops the lock and returns.
mochel@digitalimplant.org9a19fea2005-03-21 11:45:16 -080027 *
Greg Kroah-Hartmanc3bb7fad2008-04-30 16:43:45 -070028 * There are primitives for adding and removing nodes to/from a klist.
29 * When deleting, klist_del() will simply decrement the reference count.
30 * Only when the count goes to 0 is the node removed from the list.
31 * klist_remove() will try to delete the node from the list and block until
32 * it is actually removed. This is useful for objects (like devices) that
33 * have been removed from the system and must be freed (but must wait until
34 * all accessors have finished).
mochel@digitalimplant.org9a19fea2005-03-21 11:45:16 -080035 */
36
37#include <linux/klist.h>
38#include <linux/module.h>
39
40
41/**
Greg Kroah-Hartmanc3bb7fad2008-04-30 16:43:45 -070042 * klist_init - Initialize a klist structure.
43 * @k: The klist we're initializing.
44 * @get: The get function for the embedding object (NULL if none)
45 * @put: The put function for the embedding object (NULL if none)
James Bottomley34bb61f2005-09-06 16:56:51 -070046 *
47 * Initialises the klist structure. If the klist_node structures are
48 * going to be embedded in refcounted objects (necessary for safe
49 * deletion) then the get/put arguments are used to initialise
50 * functions that take and release references on the embedding
51 * objects.
mochel@digitalimplant.org9a19fea2005-03-21 11:45:16 -080052 */
Greg Kroah-Hartmanc3bb7fad2008-04-30 16:43:45 -070053void klist_init(struct klist *k, void (*get)(struct klist_node *),
James Bottomley34bb61f2005-09-06 16:56:51 -070054 void (*put)(struct klist_node *))
mochel@digitalimplant.org9a19fea2005-03-21 11:45:16 -080055{
56 INIT_LIST_HEAD(&k->k_list);
57 spin_lock_init(&k->k_lock);
James Bottomley34bb61f2005-09-06 16:56:51 -070058 k->get = get;
59 k->put = put;
mochel@digitalimplant.org9a19fea2005-03-21 11:45:16 -080060}
mochel@digitalimplant.org9a19fea2005-03-21 11:45:16 -080061EXPORT_SYMBOL_GPL(klist_init);
62
Greg Kroah-Hartmanc3bb7fad2008-04-30 16:43:45 -070063static void add_head(struct klist *k, struct klist_node *n)
mochel@digitalimplant.org9a19fea2005-03-21 11:45:16 -080064{
65 spin_lock(&k->k_lock);
66 list_add(&n->n_node, &k->k_list);
67 spin_unlock(&k->k_lock);
68}
69
Greg Kroah-Hartmanc3bb7fad2008-04-30 16:43:45 -070070static void add_tail(struct klist *k, struct klist_node *n)
mochel@digitalimplant.org9a19fea2005-03-21 11:45:16 -080071{
72 spin_lock(&k->k_lock);
73 list_add_tail(&n->n_node, &k->k_list);
74 spin_unlock(&k->k_lock);
75}
76
Greg Kroah-Hartmanc3bb7fad2008-04-30 16:43:45 -070077static void klist_node_init(struct klist *k, struct klist_node *n)
mochel@digitalimplant.org9a19fea2005-03-21 11:45:16 -080078{
79 INIT_LIST_HEAD(&n->n_node);
80 init_completion(&n->n_removed);
81 kref_init(&n->n_ref);
82 n->n_klist = k;
James Bottomley34bb61f2005-09-06 16:56:51 -070083 if (k->get)
84 k->get(n);
mochel@digitalimplant.org9a19fea2005-03-21 11:45:16 -080085}
86
mochel@digitalimplant.org9a19fea2005-03-21 11:45:16 -080087/**
Greg Kroah-Hartmanc3bb7fad2008-04-30 16:43:45 -070088 * klist_add_head - Initialize a klist_node and add it to front.
89 * @n: node we're adding.
90 * @k: klist it's going on.
mochel@digitalimplant.org9a19fea2005-03-21 11:45:16 -080091 */
Greg Kroah-Hartmanc3bb7fad2008-04-30 16:43:45 -070092void klist_add_head(struct klist_node *n, struct klist *k)
mochel@digitalimplant.org9a19fea2005-03-21 11:45:16 -080093{
94 klist_node_init(k, n);
95 add_head(k, n);
96}
mochel@digitalimplant.org9a19fea2005-03-21 11:45:16 -080097EXPORT_SYMBOL_GPL(klist_add_head);
98
mochel@digitalimplant.org9a19fea2005-03-21 11:45:16 -080099/**
Greg Kroah-Hartmanc3bb7fad2008-04-30 16:43:45 -0700100 * klist_add_tail - Initialize a klist_node and add it to back.
101 * @n: node we're adding.
102 * @k: klist it's going on.
mochel@digitalimplant.org9a19fea2005-03-21 11:45:16 -0800103 */
Greg Kroah-Hartmanc3bb7fad2008-04-30 16:43:45 -0700104void klist_add_tail(struct klist_node *n, struct klist *k)
mochel@digitalimplant.org9a19fea2005-03-21 11:45:16 -0800105{
106 klist_node_init(k, n);
107 add_tail(k, n);
108}
mochel@digitalimplant.org9a19fea2005-03-21 11:45:16 -0800109EXPORT_SYMBOL_GPL(klist_add_tail);
110
Tejun Heo93dd4002008-04-22 18:58:46 +0900111/**
112 * klist_add_after - Init a klist_node and add it after an existing node
113 * @n: node we're adding.
114 * @pos: node to put @n after
115 */
116void klist_add_after(struct klist_node *n, struct klist_node *pos)
117{
118 struct klist *k = pos->n_klist;
119
120 klist_node_init(k, n);
121 spin_lock(&k->k_lock);
122 list_add(&n->n_node, &pos->n_node);
123 spin_unlock(&k->k_lock);
124}
125EXPORT_SYMBOL_GPL(klist_add_after);
126
127/**
128 * klist_add_before - Init a klist_node and add it before an existing node
129 * @n: node we're adding.
130 * @pos: node to put @n after
131 */
132void klist_add_before(struct klist_node *n, struct klist_node *pos)
133{
134 struct klist *k = pos->n_klist;
135
136 klist_node_init(k, n);
137 spin_lock(&k->k_lock);
138 list_add_tail(&n->n_node, &pos->n_node);
139 spin_unlock(&k->k_lock);
140}
141EXPORT_SYMBOL_GPL(klist_add_before);
142
Greg Kroah-Hartmanc3bb7fad2008-04-30 16:43:45 -0700143static void klist_release(struct kref *kref)
mochel@digitalimplant.org9a19fea2005-03-21 11:45:16 -0800144{
Greg Kroah-Hartmanc3bb7fad2008-04-30 16:43:45 -0700145 struct klist_node *n = container_of(kref, struct klist_node, n_ref);
Alan Stern7e9f4b22006-09-18 16:28:06 -0400146
mochel@digitalimplant.org9a19fea2005-03-21 11:45:16 -0800147 list_del(&n->n_node);
148 complete(&n->n_removed);
mochel@digitalimplant.org8b0c2502005-03-24 12:58:57 -0800149 n->n_klist = NULL;
mochel@digitalimplant.org9a19fea2005-03-21 11:45:16 -0800150}
151
Greg Kroah-Hartmanc3bb7fad2008-04-30 16:43:45 -0700152static int klist_dec_and_del(struct klist_node *n)
mochel@digitalimplant.org9a19fea2005-03-21 11:45:16 -0800153{
154 return kref_put(&n->n_ref, klist_release);
155}
156
mochel@digitalimplant.org9a19fea2005-03-21 11:45:16 -0800157/**
Greg Kroah-Hartmanc3bb7fad2008-04-30 16:43:45 -0700158 * klist_del - Decrement the reference count of node and try to remove.
159 * @n: node we're deleting.
mochel@digitalimplant.org9a19fea2005-03-21 11:45:16 -0800160 */
Greg Kroah-Hartmanc3bb7fad2008-04-30 16:43:45 -0700161void klist_del(struct klist_node *n)
mochel@digitalimplant.org9a19fea2005-03-21 11:45:16 -0800162{
Greg Kroah-Hartmanc3bb7fad2008-04-30 16:43:45 -0700163 struct klist *k = n->n_klist;
Alan Stern7e9f4b22006-09-18 16:28:06 -0400164 void (*put)(struct klist_node *) = k->put;
mochel@digitalimplant.org9a19fea2005-03-21 11:45:16 -0800165
166 spin_lock(&k->k_lock);
Alan Stern7e9f4b22006-09-18 16:28:06 -0400167 if (!klist_dec_and_del(n))
168 put = NULL;
mochel@digitalimplant.org9a19fea2005-03-21 11:45:16 -0800169 spin_unlock(&k->k_lock);
Alan Stern7e9f4b22006-09-18 16:28:06 -0400170 if (put)
171 put(n);
mochel@digitalimplant.org9a19fea2005-03-21 11:45:16 -0800172}
mochel@digitalimplant.org9a19fea2005-03-21 11:45:16 -0800173EXPORT_SYMBOL_GPL(klist_del);
174
mochel@digitalimplant.org9a19fea2005-03-21 11:45:16 -0800175/**
Greg Kroah-Hartmanc3bb7fad2008-04-30 16:43:45 -0700176 * klist_remove - Decrement the refcount of node and wait for it to go away.
177 * @n: node we're removing.
mochel@digitalimplant.org9a19fea2005-03-21 11:45:16 -0800178 */
Greg Kroah-Hartmanc3bb7fad2008-04-30 16:43:45 -0700179void klist_remove(struct klist_node *n)
mochel@digitalimplant.org9a19fea2005-03-21 11:45:16 -0800180{
Alan Stern7e9f4b22006-09-18 16:28:06 -0400181 klist_del(n);
mochel@digitalimplant.org9a19fea2005-03-21 11:45:16 -0800182 wait_for_completion(&n->n_removed);
183}
mochel@digitalimplant.org9a19fea2005-03-21 11:45:16 -0800184EXPORT_SYMBOL_GPL(klist_remove);
185
mochel@digitalimplant.org9a19fea2005-03-21 11:45:16 -0800186/**
Greg Kroah-Hartmanc3bb7fad2008-04-30 16:43:45 -0700187 * klist_node_attached - Say whether a node is bound to a list or not.
188 * @n: Node that we're testing.
mochel@digitalimplant.org8b0c2502005-03-24 12:58:57 -0800189 */
Greg Kroah-Hartmanc3bb7fad2008-04-30 16:43:45 -0700190int klist_node_attached(struct klist_node *n)
mochel@digitalimplant.org8b0c2502005-03-24 12:58:57 -0800191{
192 return (n->n_klist != NULL);
193}
mochel@digitalimplant.org8b0c2502005-03-24 12:58:57 -0800194EXPORT_SYMBOL_GPL(klist_node_attached);
195
mochel@digitalimplant.org8b0c2502005-03-24 12:58:57 -0800196/**
Greg Kroah-Hartmanc3bb7fad2008-04-30 16:43:45 -0700197 * klist_iter_init_node - Initialize a klist_iter structure.
198 * @k: klist we're iterating.
199 * @i: klist_iter we're filling.
200 * @n: node to start with.
mochel@digitalimplant.org9a19fea2005-03-21 11:45:16 -0800201 *
Greg Kroah-Hartmanc3bb7fad2008-04-30 16:43:45 -0700202 * Similar to klist_iter_init(), but starts the action off with @n,
203 * instead of with the list head.
mochel@digitalimplant.org9a19fea2005-03-21 11:45:16 -0800204 */
Greg Kroah-Hartmanc3bb7fad2008-04-30 16:43:45 -0700205void klist_iter_init_node(struct klist *k, struct klist_iter *i,
206 struct klist_node *n)
mochel@digitalimplant.org9a19fea2005-03-21 11:45:16 -0800207{
208 i->i_klist = k;
209 i->i_head = &k->k_list;
210 i->i_cur = n;
Frank Pavlice22dafb2005-11-26 20:48:40 -0800211 if (n)
212 kref_get(&n->n_ref);
mochel@digitalimplant.org9a19fea2005-03-21 11:45:16 -0800213}
mochel@digitalimplant.org9a19fea2005-03-21 11:45:16 -0800214EXPORT_SYMBOL_GPL(klist_iter_init_node);
215
mochel@digitalimplant.org9a19fea2005-03-21 11:45:16 -0800216/**
Greg Kroah-Hartmanc3bb7fad2008-04-30 16:43:45 -0700217 * klist_iter_init - Iniitalize a klist_iter structure.
218 * @k: klist we're iterating.
219 * @i: klist_iter structure we're filling.
mochel@digitalimplant.org9a19fea2005-03-21 11:45:16 -0800220 *
Greg Kroah-Hartmanc3bb7fad2008-04-30 16:43:45 -0700221 * Similar to klist_iter_init_node(), but start with the list head.
mochel@digitalimplant.org9a19fea2005-03-21 11:45:16 -0800222 */
Greg Kroah-Hartmanc3bb7fad2008-04-30 16:43:45 -0700223void klist_iter_init(struct klist *k, struct klist_iter *i)
mochel@digitalimplant.org9a19fea2005-03-21 11:45:16 -0800224{
225 klist_iter_init_node(k, i, NULL);
226}
mochel@digitalimplant.org9a19fea2005-03-21 11:45:16 -0800227EXPORT_SYMBOL_GPL(klist_iter_init);
228
mochel@digitalimplant.org9a19fea2005-03-21 11:45:16 -0800229/**
Greg Kroah-Hartmanc3bb7fad2008-04-30 16:43:45 -0700230 * klist_iter_exit - Finish a list iteration.
231 * @i: Iterator structure.
mochel@digitalimplant.org9a19fea2005-03-21 11:45:16 -0800232 *
Greg Kroah-Hartmanc3bb7fad2008-04-30 16:43:45 -0700233 * Must be called when done iterating over list, as it decrements the
234 * refcount of the current node. Necessary in case iteration exited before
235 * the end of the list was reached, and always good form.
mochel@digitalimplant.org9a19fea2005-03-21 11:45:16 -0800236 */
Greg Kroah-Hartmanc3bb7fad2008-04-30 16:43:45 -0700237void klist_iter_exit(struct klist_iter *i)
mochel@digitalimplant.org9a19fea2005-03-21 11:45:16 -0800238{
239 if (i->i_cur) {
240 klist_del(i->i_cur);
241 i->i_cur = NULL;
242 }
243}
mochel@digitalimplant.org9a19fea2005-03-21 11:45:16 -0800244EXPORT_SYMBOL_GPL(klist_iter_exit);
245
Greg Kroah-Hartmanc3bb7fad2008-04-30 16:43:45 -0700246static struct klist_node *to_klist_node(struct list_head *n)
mochel@digitalimplant.org9a19fea2005-03-21 11:45:16 -0800247{
248 return container_of(n, struct klist_node, n_node);
249}
250
mochel@digitalimplant.org9a19fea2005-03-21 11:45:16 -0800251/**
Greg Kroah-Hartmanc3bb7fad2008-04-30 16:43:45 -0700252 * klist_next - Ante up next node in list.
253 * @i: Iterator structure.
mochel@digitalimplant.org9a19fea2005-03-21 11:45:16 -0800254 *
Greg Kroah-Hartmanc3bb7fad2008-04-30 16:43:45 -0700255 * First grab list lock. Decrement the reference count of the previous
256 * node, if there was one. Grab the next node, increment its reference
257 * count, drop the lock, and return that next node.
mochel@digitalimplant.org9a19fea2005-03-21 11:45:16 -0800258 */
Greg Kroah-Hartmanc3bb7fad2008-04-30 16:43:45 -0700259struct klist_node *klist_next(struct klist_iter *i)
mochel@digitalimplant.org9a19fea2005-03-21 11:45:16 -0800260{
Greg Kroah-Hartmanc3bb7fad2008-04-30 16:43:45 -0700261 struct list_head *next;
262 struct klist_node *lnode = i->i_cur;
263 struct klist_node *knode = NULL;
Alan Stern7e9f4b22006-09-18 16:28:06 -0400264 void (*put)(struct klist_node *) = i->i_klist->put;
mochel@digitalimplant.org9a19fea2005-03-21 11:45:16 -0800265
266 spin_lock(&i->i_klist->k_lock);
Alan Stern7e9f4b22006-09-18 16:28:06 -0400267 if (lnode) {
268 next = lnode->n_node.next;
269 if (!klist_dec_and_del(lnode))
270 put = NULL;
mochel@digitalimplant.org9a19fea2005-03-21 11:45:16 -0800271 } else
272 next = i->i_head->next;
273
274 if (next != i->i_head) {
275 knode = to_klist_node(next);
276 kref_get(&knode->n_ref);
277 }
278 i->i_cur = knode;
279 spin_unlock(&i->i_klist->k_lock);
Alan Stern7e9f4b22006-09-18 16:28:06 -0400280 if (put && lnode)
281 put(lnode);
mochel@digitalimplant.org9a19fea2005-03-21 11:45:16 -0800282 return knode;
283}
mochel@digitalimplant.org9a19fea2005-03-21 11:45:16 -0800284EXPORT_SYMBOL_GPL(klist_next);