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>
8 #include <linux/export.h>
13 * ulist is a generic data structure to hold a collection of unique u64
14 * values. The only operations it supports is adding to the list and
16 * It is possible to store an auxiliary value along with the key.
18 * A sample usage for ulists is the enumeration of directed graphs without
19 * visiting a node twice. The pseudo-code could look like this:
21 * ulist = ulist_alloc();
22 * ulist_add(ulist, root);
23 * ULIST_ITER_INIT(&uiter);
25 * while ((elem = ulist_next(ulist, &uiter)) {
26 * for (all child nodes n in elem)
27 * ulist_add(ulist, n);
28 * do something useful with the node;
32 * This assumes the graph nodes are adressable by u64. This stems from the
33 * usage for tree enumeration in btrfs, where the logical addresses are
36 * It is also useful for tree enumeration which could be done elegantly
37 * recursively, but is not possible due to kernel stack limitations. The
38 * loop would be similar to the above.
42 * ulist_init - freshly initialize a ulist
43 * @ulist: the ulist to initialize
45 * Note: don't use this function to init an already used ulist, use
46 * ulist_reinit instead.
48 void ulist_init(struct ulist *ulist)
50 INIT_LIST_HEAD(&ulist->nodes);
51 ulist->root = RB_ROOT;
54 EXPORT_SYMBOL(ulist_init);
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 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);
74 EXPORT_SYMBOL(ulist_fini);
77 * ulist_reinit - prepare a ulist for reuse
78 * @ulist: ulist to be reused
80 * Free up all additional memory allocated for the list elements and reinit
83 void ulist_reinit(struct ulist *ulist)
88 EXPORT_SYMBOL(ulist_reinit);
91 * ulist_alloc - dynamically allocate a ulist
92 * @gfp_mask: allocation flags to for base allocation
94 * The allocated ulist will be returned in an initialized state.
96 struct ulist *ulist_alloc(gfp_t gfp_mask)
98 struct ulist *ulist = kmalloc(sizeof(*ulist), gfp_mask);
107 EXPORT_SYMBOL(ulist_alloc);
110 * ulist_free - free dynamically allocated ulist
111 * @ulist: ulist to free
113 * It is not necessary to call ulist_fini before.
115 void ulist_free(struct ulist *ulist)
122 EXPORT_SYMBOL(ulist_free);
124 static struct ulist_node *ulist_rbtree_search(struct ulist *ulist, u64 val)
126 struct rb_node *n = ulist->root.rb_node;
127 struct ulist_node *u = NULL;
130 u = rb_entry(n, struct ulist_node, rb_node);
133 else if (u->val > val)
141 static int ulist_rbtree_insert(struct ulist *ulist, struct ulist_node *ins)
143 struct rb_node **p = &ulist->root.rb_node;
144 struct rb_node *parent = NULL;
145 struct ulist_node *cur = NULL;
149 cur = rb_entry(parent, struct ulist_node, rb_node);
151 if (cur->val < ins->val)
153 else if (cur->val > ins->val)
158 rb_link_node(&ins->rb_node, parent, p);
159 rb_insert_color(&ins->rb_node, &ulist->root);
164 * ulist_add - add an element to the ulist
165 * @ulist: ulist to add the element to
166 * @val: value to add to ulist
167 * @aux: auxiliary value to store along with val
168 * @gfp_mask: flags to use for allocation
170 * Note: locking must be provided by the caller. In case of rwlocks write
173 * Add an element to a ulist. The @val will only be added if it doesn't
174 * already exist. If it is added, the auxiliary value @aux is stored along with
175 * it. In case @val already exists in the ulist, @aux is ignored, even if
176 * it differs from the already stored value.
178 * ulist_add returns 0 if @val already exists in ulist and 1 if @val has been
180 * In case of allocation failure -ENOMEM is returned and the ulist stays
183 int ulist_add(struct ulist *ulist, u64 val, u64 aux, gfp_t gfp_mask)
185 return ulist_add_merge(ulist, val, aux, NULL, gfp_mask);
188 int ulist_add_merge(struct ulist *ulist, u64 val, u64 aux,
189 u64 *old_aux, gfp_t gfp_mask)
192 struct ulist_node *node;
194 node = ulist_rbtree_search(ulist, val);
197 *old_aux = node->aux;
200 node = kmalloc(sizeof(*node), gfp_mask);
206 #ifdef CONFIG_BTRFS_DEBUG
207 node->seqnum = ulist->nnodes;
210 ret = ulist_rbtree_insert(ulist, node);
212 list_add_tail(&node->list, &ulist->nodes);
217 EXPORT_SYMBOL(ulist_add);
220 * ulist_next - iterate ulist
221 * @ulist: ulist to iterate
222 * @uiter: iterator variable, initialized with ULIST_ITER_INIT(&iterator)
224 * Note: locking must be provided by the caller. In case of rwlocks only read
227 * This function is used to iterate an ulist.
228 * It returns the next element from the ulist or %NULL when the
229 * end is reached. No guarantee is made with respect to the order in which
230 * the elements are returned. They might neither be returned in order of
231 * addition nor in ascending order.
232 * It is allowed to call ulist_add during an enumeration. Newly added items
233 * are guaranteed to show up in the running enumeration.
235 struct ulist_node *ulist_next(struct ulist *ulist, struct ulist_iterator *uiter)
237 struct ulist_node *node;
239 if (list_empty(&ulist->nodes))
241 if (uiter->cur_list && uiter->cur_list->next == &ulist->nodes)
243 if (uiter->cur_list) {
244 uiter->cur_list = uiter->cur_list->next;
246 uiter->cur_list = ulist->nodes.next;
247 #ifdef CONFIG_BTRFS_DEBUG
251 node = list_entry(uiter->cur_list, struct ulist_node, list);
252 #ifdef CONFIG_BTRFS_DEBUG
253 ASSERT(node->seqnum == uiter->i);
254 ASSERT(uiter->i >= 0 && uiter->i < ulist->nnodes);
259 EXPORT_SYMBOL(ulist_next);