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Arne Jansenda5c8132011-09-13 12:29:12 +02001/*
2 * Copyright (C) 2011 STRATO AG
3 * written by Arne Jansen <sensille@gmx.net>
4 * Distributed under the GNU GPL license version 2.
5 */
6
7#include <linux/slab.h>
Paul Gortmaker180e0012013-02-14 13:50:15 -07008#include <linux/export.h>
Arne Jansenda5c8132011-09-13 12:29:12 +02009#include "ulist.h"
10
11/*
12 * ulist is a generic data structure to hold a collection of unique u64
13 * values. The only operations it supports is adding to the list and
14 * enumerating it.
15 * It is possible to store an auxiliary value along with the key.
16 *
17 * The implementation is preliminary and can probably be sped up
18 * significantly. A first step would be to store the values in an rbtree
19 * as soon as ULIST_SIZE is exceeded.
20 *
21 * A sample usage for ulists is the enumeration of directed graphs without
22 * visiting a node twice. The pseudo-code could look like this:
23 *
24 * ulist = ulist_alloc();
25 * ulist_add(ulist, root);
Jan Schmidtcd1b4132012-05-22 14:56:50 +020026 * ULIST_ITER_INIT(&uiter);
Arne Jansenda5c8132011-09-13 12:29:12 +020027 *
Jan Schmidtcd1b4132012-05-22 14:56:50 +020028 * while ((elem = ulist_next(ulist, &uiter)) {
Arne Jansenda5c8132011-09-13 12:29:12 +020029 * for (all child nodes n in elem)
30 * ulist_add(ulist, n);
31 * do something useful with the node;
32 * }
33 * ulist_free(ulist);
34 *
35 * This assumes the graph nodes are adressable by u64. This stems from the
36 * usage for tree enumeration in btrfs, where the logical addresses are
37 * 64 bit.
38 *
39 * It is also useful for tree enumeration which could be done elegantly
40 * recursively, but is not possible due to kernel stack limitations. The
41 * loop would be similar to the above.
42 */
43
44/**
45 * ulist_init - freshly initialize a ulist
46 * @ulist: the ulist to initialize
47 *
48 * Note: don't use this function to init an already used ulist, use
49 * ulist_reinit instead.
50 */
51void ulist_init(struct ulist *ulist)
52{
53 ulist->nnodes = 0;
54 ulist->nodes = ulist->int_nodes;
55 ulist->nodes_alloced = ULIST_SIZE;
Wang Shilongf7f82b82013-04-12 12:12:17 +000056 ulist->root = RB_ROOT;
Arne Jansenda5c8132011-09-13 12:29:12 +020057}
58EXPORT_SYMBOL(ulist_init);
59
60/**
61 * ulist_fini - free up additionally allocated memory for the ulist
62 * @ulist: the ulist from which to free the additional memory
63 *
64 * This is useful in cases where the base 'struct ulist' has been statically
65 * allocated.
66 */
67void ulist_fini(struct ulist *ulist)
68{
69 /*
70 * The first ULIST_SIZE elements are stored inline in struct ulist.
71 * Only if more elements are alocated they need to be freed.
72 */
73 if (ulist->nodes_alloced > ULIST_SIZE)
74 kfree(ulist->nodes);
75 ulist->nodes_alloced = 0; /* in case ulist_fini is called twice */
Wang Shilongf7f82b82013-04-12 12:12:17 +000076 ulist->root = RB_ROOT;
Arne Jansenda5c8132011-09-13 12:29:12 +020077}
78EXPORT_SYMBOL(ulist_fini);
79
80/**
81 * ulist_reinit - prepare a ulist for reuse
82 * @ulist: ulist to be reused
83 *
84 * Free up all additional memory allocated for the list elements and reinit
85 * the ulist.
86 */
87void ulist_reinit(struct ulist *ulist)
88{
89 ulist_fini(ulist);
90 ulist_init(ulist);
91}
92EXPORT_SYMBOL(ulist_reinit);
93
94/**
95 * ulist_alloc - dynamically allocate a ulist
96 * @gfp_mask: allocation flags to for base allocation
97 *
98 * The allocated ulist will be returned in an initialized state.
99 */
Daniel J Blueman2eec6c82012-04-26 00:37:14 +0800100struct ulist *ulist_alloc(gfp_t gfp_mask)
Arne Jansenda5c8132011-09-13 12:29:12 +0200101{
102 struct ulist *ulist = kmalloc(sizeof(*ulist), gfp_mask);
103
104 if (!ulist)
105 return NULL;
106
107 ulist_init(ulist);
108
109 return ulist;
110}
111EXPORT_SYMBOL(ulist_alloc);
112
113/**
114 * ulist_free - free dynamically allocated ulist
115 * @ulist: ulist to free
116 *
117 * It is not necessary to call ulist_fini before.
118 */
119void ulist_free(struct ulist *ulist)
120{
121 if (!ulist)
122 return;
123 ulist_fini(ulist);
124 kfree(ulist);
125}
126EXPORT_SYMBOL(ulist_free);
127
Wang Shilongf7f82b82013-04-12 12:12:17 +0000128static struct ulist_node *ulist_rbtree_search(struct ulist *ulist, u64 val)
129{
130 struct rb_node *n = ulist->root.rb_node;
131 struct ulist_node *u = NULL;
132
133 while (n) {
134 u = rb_entry(n, struct ulist_node, rb_node);
135 if (u->val < val)
136 n = n->rb_right;
137 else if (u->val > val)
138 n = n->rb_left;
139 else
140 return u;
141 }
142 return NULL;
143}
144
145static int ulist_rbtree_insert(struct ulist *ulist, struct ulist_node *ins)
146{
147 struct rb_node **p = &ulist->root.rb_node;
148 struct rb_node *parent = NULL;
149 struct ulist_node *cur = NULL;
150
151 while (*p) {
152 parent = *p;
153 cur = rb_entry(parent, struct ulist_node, rb_node);
154
155 if (cur->val < ins->val)
156 p = &(*p)->rb_right;
157 else if (cur->val > ins->val)
158 p = &(*p)->rb_left;
159 else
160 return -EEXIST;
161 }
162 rb_link_node(&ins->rb_node, parent, p);
163 rb_insert_color(&ins->rb_node, &ulist->root);
164 return 0;
165}
166
Arne Jansenda5c8132011-09-13 12:29:12 +0200167/**
168 * ulist_add - add an element to the ulist
169 * @ulist: ulist to add the element to
170 * @val: value to add to ulist
171 * @aux: auxiliary value to store along with val
172 * @gfp_mask: flags to use for allocation
173 *
174 * Note: locking must be provided by the caller. In case of rwlocks write
175 * locking is needed
176 *
177 * Add an element to a ulist. The @val will only be added if it doesn't
178 * already exist. If it is added, the auxiliary value @aux is stored along with
179 * it. In case @val already exists in the ulist, @aux is ignored, even if
180 * it differs from the already stored value.
181 *
182 * ulist_add returns 0 if @val already exists in ulist and 1 if @val has been
183 * inserted.
184 * In case of allocation failure -ENOMEM is returned and the ulist stays
185 * unaltered.
186 */
Alexander Block34d73f52012-07-28 16:18:58 +0200187int ulist_add(struct ulist *ulist, u64 val, u64 aux, gfp_t gfp_mask)
Arne Jansenda5c8132011-09-13 12:29:12 +0200188{
Jan Schmidt33019582012-05-30 18:05:21 +0200189 return ulist_add_merge(ulist, val, aux, NULL, gfp_mask);
190}
191
Alexander Block34d73f52012-07-28 16:18:58 +0200192int ulist_add_merge(struct ulist *ulist, u64 val, u64 aux,
193 u64 *old_aux, gfp_t gfp_mask)
Jan Schmidt33019582012-05-30 18:05:21 +0200194{
Wang Shilongf7f82b82013-04-12 12:12:17 +0000195 int ret = 0;
196 struct ulist_node *node = NULL;
197 node = ulist_rbtree_search(ulist, val);
198 if (node) {
199 if (old_aux)
200 *old_aux = node->aux;
201 return 0;
Arne Jansenda5c8132011-09-13 12:29:12 +0200202 }
203
204 if (ulist->nnodes >= ulist->nodes_alloced) {
205 u64 new_alloced = ulist->nodes_alloced + 128;
206 struct ulist_node *new_nodes;
207 void *old = NULL;
Liu Bo35f03992013-06-28 12:37:45 +0800208 int i;
209
210 for (i = 0; i < ulist->nnodes; i++)
211 rb_erase(&ulist->nodes[i].rb_node, &ulist->root);
Arne Jansenda5c8132011-09-13 12:29:12 +0200212
213 /*
214 * if nodes_alloced == ULIST_SIZE no memory has been allocated
215 * yet, so pass NULL to krealloc
216 */
217 if (ulist->nodes_alloced > ULIST_SIZE)
218 old = ulist->nodes;
219
220 new_nodes = krealloc(old, sizeof(*new_nodes) * new_alloced,
221 gfp_mask);
222 if (!new_nodes)
223 return -ENOMEM;
224
225 if (!old)
226 memcpy(new_nodes, ulist->int_nodes,
227 sizeof(ulist->int_nodes));
228
229 ulist->nodes = new_nodes;
230 ulist->nodes_alloced = new_alloced;
Liu Bo35f03992013-06-28 12:37:45 +0800231
232 /*
233 * krealloc actually uses memcpy, which does not copy rb_node
234 * pointers, so we have to do it ourselves. Otherwise we may
235 * be bitten by crashes.
236 */
237 for (i = 0; i < ulist->nnodes; i++) {
238 ret = ulist_rbtree_insert(ulist, &ulist->nodes[i]);
239 if (ret < 0)
240 return ret;
241 }
Arne Jansenda5c8132011-09-13 12:29:12 +0200242 }
243 ulist->nodes[ulist->nnodes].val = val;
244 ulist->nodes[ulist->nnodes].aux = aux;
Wang Shilongf7f82b82013-04-12 12:12:17 +0000245 ret = ulist_rbtree_insert(ulist, &ulist->nodes[ulist->nnodes]);
246 BUG_ON(ret);
Arne Jansenda5c8132011-09-13 12:29:12 +0200247 ++ulist->nnodes;
248
249 return 1;
250}
251EXPORT_SYMBOL(ulist_add);
252
253/**
254 * ulist_next - iterate ulist
255 * @ulist: ulist to iterate
Jan Schmidtcd1b4132012-05-22 14:56:50 +0200256 * @uiter: iterator variable, initialized with ULIST_ITER_INIT(&iterator)
Arne Jansenda5c8132011-09-13 12:29:12 +0200257 *
258 * Note: locking must be provided by the caller. In case of rwlocks only read
259 * locking is needed
260 *
Jan Schmidtcd1b4132012-05-22 14:56:50 +0200261 * This function is used to iterate an ulist.
262 * It returns the next element from the ulist or %NULL when the
Arne Jansenda5c8132011-09-13 12:29:12 +0200263 * end is reached. No guarantee is made with respect to the order in which
264 * the elements are returned. They might neither be returned in order of
265 * addition nor in ascending order.
266 * It is allowed to call ulist_add during an enumeration. Newly added items
267 * are guaranteed to show up in the running enumeration.
268 */
Jan Schmidtcd1b4132012-05-22 14:56:50 +0200269struct ulist_node *ulist_next(struct ulist *ulist, struct ulist_iterator *uiter)
Arne Jansenda5c8132011-09-13 12:29:12 +0200270{
Arne Jansenda5c8132011-09-13 12:29:12 +0200271 if (ulist->nnodes == 0)
272 return NULL;
Jan Schmidtcd1b4132012-05-22 14:56:50 +0200273 if (uiter->i < 0 || uiter->i >= ulist->nnodes)
Arne Jansenda5c8132011-09-13 12:29:12 +0200274 return NULL;
275
Jan Schmidtcd1b4132012-05-22 14:56:50 +0200276 return &ulist->nodes[uiter->i++];
Arne Jansenda5c8132011-09-13 12:29:12 +0200277}
278EXPORT_SYMBOL(ulist_next);