2 * Copyright (C) 2011 STRATO AG
3 * written by Arne Jansen <sensille@gmx.net>
4 * Distributed under the GNU GPL license version 2.
7 //#include <linux/slab.h>
9 #include "kerncompat.h"
14 * ulist is a generic data structure to hold a collection of unique u64
15 * values. The only operations it supports is adding to the list and
17 * It is possible to store an auxiliary value along with the key.
19 * A sample usage for ulists is the enumeration of directed graphs without
20 * visiting a node twice. The pseudo-code could look like this:
22 * ulist = ulist_alloc();
23 * ulist_add(ulist, root);
24 * ULIST_ITER_INIT(&uiter);
26 * while ((elem = ulist_next(ulist, &uiter)) {
27 * for (all child nodes n in elem)
28 * ulist_add(ulist, n);
29 * do something useful with the node;
33 * This assumes the graph nodes are addressable by u64. This stems from the
34 * usage for tree enumeration in btrfs, where the logical addresses are
37 * It is also useful for tree enumeration which could be done elegantly
38 * recursively, but is not possible due to kernel stack limitations. The
39 * loop would be similar to the above.
43 * ulist_init - freshly initialize a ulist
44 * @ulist: the ulist to initialize
46 * Note: don't use this function to init an already used ulist, use
47 * ulist_reinit instead.
49 void ulist_init(struct ulist *ulist)
51 INIT_LIST_HEAD(&ulist->nodes);
52 ulist->root = RB_ROOT;
57 * ulist_fini - free up additionally allocated memory for the ulist
58 * @ulist: the ulist from which to free the additional memory
60 * This is useful in cases where the base 'struct ulist' has been statically
63 static void ulist_fini(struct ulist *ulist)
65 struct ulist_node *node;
66 struct ulist_node *next;
68 list_for_each_entry_safe(node, next, &ulist->nodes, list) {
71 ulist->root = RB_ROOT;
72 INIT_LIST_HEAD(&ulist->nodes);
76 * ulist_reinit - prepare a ulist for reuse
77 * @ulist: ulist to be reused
79 * Free up all additional memory allocated for the list elements and reinit
82 void ulist_reinit(struct ulist *ulist)
89 * ulist_alloc - dynamically allocate a ulist
90 * @gfp_mask: allocation flags to for base allocation
92 * The allocated ulist will be returned in an initialized state.
94 struct ulist *ulist_alloc(gfp_t gfp_mask)
96 struct ulist *ulist = kmalloc(sizeof(*ulist), gfp_mask);
107 * ulist_free - free dynamically allocated ulist
108 * @ulist: ulist to free
110 * It is not necessary to call ulist_fini before.
112 void ulist_free(struct ulist *ulist)
120 static struct ulist_node *ulist_rbtree_search(struct ulist *ulist, u64 val)
122 struct rb_node *n = ulist->root.rb_node;
123 struct ulist_node *u = NULL;
126 u = rb_entry(n, struct ulist_node, rb_node);
129 else if (u->val > val)
137 static void ulist_rbtree_erase(struct ulist *ulist, struct ulist_node *node)
139 rb_erase(&node->rb_node, &ulist->root);
140 list_del(&node->list);
142 BUG_ON(ulist->nnodes == 0);
146 static int ulist_rbtree_insert(struct ulist *ulist, struct ulist_node *ins)
148 struct rb_node **p = &ulist->root.rb_node;
149 struct rb_node *parent = NULL;
150 struct ulist_node *cur = NULL;
154 cur = rb_entry(parent, struct ulist_node, rb_node);
156 if (cur->val < ins->val)
158 else if (cur->val > ins->val)
163 rb_link_node(&ins->rb_node, parent, p);
164 rb_insert_color(&ins->rb_node, &ulist->root);
169 * ulist_add - add an element to the ulist
170 * @ulist: ulist to add the element to
171 * @val: value to add to ulist
172 * @aux: auxiliary value to store along with val
173 * @gfp_mask: flags to use for allocation
175 * Note: locking must be provided by the caller. In case of rwlocks write
178 * Add an element to a ulist. The @val will only be added if it doesn't
179 * already exist. If it is added, the auxiliary value @aux is stored along with
180 * it. In case @val already exists in the ulist, @aux is ignored, even if
181 * it differs from the already stored value.
183 * ulist_add returns 0 if @val already exists in ulist and 1 if @val has been
185 * In case of allocation failure -ENOMEM is returned and the ulist stays
188 int ulist_add(struct ulist *ulist, u64 val, u64 aux, gfp_t gfp_mask)
190 return ulist_add_merge(ulist, val, aux, NULL, gfp_mask);
193 int ulist_add_merge(struct ulist *ulist, u64 val, u64 aux,
194 u64 *old_aux, gfp_t gfp_mask)
197 struct ulist_node *node;
199 node = ulist_rbtree_search(ulist, val);
202 *old_aux = node->aux;
205 node = kmalloc(sizeof(*node), gfp_mask);
212 ret = ulist_rbtree_insert(ulist, node);
214 list_add_tail(&node->list, &ulist->nodes);
221 * ulist_del - delete one node from ulist
222 * @ulist: ulist to remove node from
223 * @val: value to delete
224 * @aux: aux to delete
226 * The deletion will only be done when *BOTH* val and aux matches.
227 * Return 0 for successful delete.
228 * Return > 0 for not found.
230 int ulist_del(struct ulist *ulist, u64 val, u64 aux)
232 struct ulist_node *node;
234 node = ulist_rbtree_search(ulist, val);
239 if (node->aux != aux)
242 /* Found and delete */
243 ulist_rbtree_erase(ulist, node);
248 * ulist_next - iterate ulist
249 * @ulist: ulist to iterate
250 * @uiter: iterator variable, initialized with ULIST_ITER_INIT(&iterator)
252 * Note: locking must be provided by the caller. In case of rwlocks only read
255 * This function is used to iterate an ulist.
256 * It returns the next element from the ulist or %NULL when the
257 * end is reached. No guarantee is made with respect to the order in which
258 * the elements are returned. They might neither be returned in order of
259 * addition nor in ascending order.
260 * It is allowed to call ulist_add during an enumeration. Newly added items
261 * are guaranteed to show up in the running enumeration.
263 struct ulist_node *ulist_next(struct ulist *ulist, struct ulist_iterator *uiter)
265 struct ulist_node *node;
267 if (list_empty(&ulist->nodes))
269 if (uiter->cur_list && uiter->cur_list->next == &ulist->nodes)
271 if (uiter->cur_list) {
272 uiter->cur_list = uiter->cur_list->next;
274 uiter->cur_list = ulist->nodes.next;
276 node = list_entry(uiter->cur_list, struct ulist_node, list);