1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * Copyright (C) 2011 STRATO AG
4 * written by Arne Jansen <sensille@gmx.net>
5 */
6
7 #include <linux/slab.h>
8 #include "messages.h"
9 #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 * A sample usage for ulists is the enumeration of directed graphs without
18 * visiting a node twice. The pseudo-code could look like this:
19 *
20 * ulist = ulist_alloc();
21 * ulist_add(ulist, root);
22 * ULIST_ITER_INIT(&uiter);
23 *
24 * while ((elem = ulist_next(ulist, &uiter)) {
25 * for (all child nodes n in elem)
26 * ulist_add(ulist, n);
27 * do something useful with the node;
28 * }
29 * ulist_free(ulist);
30 *
31 * This assumes the graph nodes are addressable by u64. This stems from the
32 * usage for tree enumeration in btrfs, where the logical addresses are
33 * 64 bit.
34 *
35 * It is also useful for tree enumeration which could be done elegantly
36 * recursively, but is not possible due to kernel stack limitations. The
37 * loop would be similar to the above.
38 */
39
40 /*
41 * Freshly initialize a ulist.
42 *
43 * @ulist: the ulist to initialize
44 *
45 * Note: don't use this function to init an already used ulist, use
46 * ulist_reinit instead.
47 */
48 void ulist_init(struct ulist *ulist)
49 {
50 INIT_LIST_HEAD(&ulist->nodes);
51 ulist->root = RB_ROOT;
52 ulist->nnodes = 0;
53 ulist->prealloc = NULL;
54 }
55
56 /*
57 * Free up additionally allocated memory for the ulist.
58 *
59 * @ulist: the ulist from which to free the additional memory
60 *
61 * This is useful in cases where the base 'struct ulist' has been statically
62 * allocated.
63 */
64 void ulist_release(struct ulist *ulist)
65 {
66 struct ulist_node *node;
67 struct ulist_node *next;
68
69 list_for_each_entry_safe(node, next, &ulist->nodes, list) {
70 kfree(node);
71 }
72 kfree(ulist->prealloc);
73 ulist->prealloc = NULL;
74 ulist->root = RB_ROOT;
75 INIT_LIST_HEAD(&ulist->nodes);
76 }
77
78 /*
79 * Prepare a ulist for reuse.
80 *
81 * @ulist: ulist to be reused
82 *
83 * Free up all additional memory allocated for the list elements and reinit
84 * the ulist.
85 */
86 void ulist_reinit(struct ulist *ulist)
87 {
88 ulist_release(ulist);
89 ulist_init(ulist);
90 }
91
92 /*
93 * Dynamically allocate a ulist.
94 *
95 * @gfp_mask: allocation flags to for base allocation
96 *
97 * The allocated ulist will be returned in an initialized state.
98 */
99 struct ulist *ulist_alloc(gfp_t gfp_mask)
100 {
101 struct ulist *ulist = kmalloc(sizeof(*ulist), gfp_mask);
102
103 if (!ulist)
104 return NULL;
105
106 ulist_init(ulist);
107
108 return ulist;
109 }
110
111 void ulist_prealloc(struct ulist *ulist, gfp_t gfp_mask)
112 {
113 if (!ulist->prealloc)
114 ulist->prealloc = kzalloc(sizeof(*ulist->prealloc), gfp_mask);
115 }
116
117 /*
118 * Free dynamically allocated ulist.
119 *
120 * @ulist: ulist to free
121 *
122 * It is not necessary to call ulist_release before.
123 */
124 void ulist_free(struct ulist *ulist)
125 {
126 if (!ulist)
127 return;
128 ulist_release(ulist);
129 kfree(ulist);
130 }
131
132 static struct ulist_node *ulist_rbtree_search(struct ulist *ulist, u64 val)
133 {
134 struct rb_node *n = ulist->root.rb_node;
135 struct ulist_node *u = NULL;
136
137 while (n) {
138 u = rb_entry(n, struct ulist_node, rb_node);
139 if (u->val < val)
140 n = n->rb_right;
141 else if (u->val > val)
142 n = n->rb_left;
143 else
144 return u;
145 }
146 return NULL;
147 }
148
149 static void ulist_rbtree_erase(struct ulist *ulist, struct ulist_node *node)
150 {
151 rb_erase(&node->rb_node, &ulist->root);
152 list_del(&node->list);
153 kfree(node);
154 BUG_ON(ulist->nnodes == 0);
155 ulist->nnodes--;
156 }
157
158 static int ulist_rbtree_insert(struct ulist *ulist, struct ulist_node *ins)
159 {
160 struct rb_node **p = &ulist->root.rb_node;
161 struct rb_node *parent = NULL;
162 struct ulist_node *cur = NULL;
163
164 while (*p) {
165 parent = *p;
166 cur = rb_entry(parent, struct ulist_node, rb_node);
167
168 if (cur->val < ins->val)
169 p = &(*p)->rb_right;
170 else if (cur->val > ins->val)
171 p = &(*p)->rb_left;
172 else
173 return -EEXIST;
174 }
175 rb_link_node(&ins->rb_node, parent, p);
176 rb_insert_color(&ins->rb_node, &ulist->root);
177 return 0;
178 }
179
180 /*
181 * Add an element to the ulist.
182 *
183 * @ulist: ulist to add the element to
184 * @val: value to add to ulist
185 * @aux: auxiliary value to store along with val
186 * @gfp_mask: flags to use for allocation
187 *
188 * Note: locking must be provided by the caller. In case of rwlocks write
189 * locking is needed
190 *
191 * Add an element to a ulist. The @val will only be added if it doesn't
192 * already exist. If it is added, the auxiliary value @aux is stored along with
193 * it. In case @val already exists in the ulist, @aux is ignored, even if
194 * it differs from the already stored value.
195 *
196 * ulist_add returns 0 if @val already exists in ulist and 1 if @val has been
197 * inserted.
198 * In case of allocation failure -ENOMEM is returned and the ulist stays
199 * unaltered.
200 */
201 int ulist_add(struct ulist *ulist, u64 val, u64 aux, gfp_t gfp_mask)
202 {
203 return ulist_add_merge(ulist, val, aux, NULL, gfp_mask);
204 }
205
206 int ulist_add_merge(struct ulist *ulist, u64 val, u64 aux,
207 u64 *old_aux, gfp_t gfp_mask)
208 {
209 int ret;
210 struct ulist_node *node;
211
212 node = ulist_rbtree_search(ulist, val);
213 if (node) {
214 if (old_aux)
215 *old_aux = node->aux;
216 return 0;
217 }
218
219 if (ulist->prealloc) {
220 node = ulist->prealloc;
221 ulist->prealloc = NULL;
222 } else {
223 node = kmalloc(sizeof(*node), gfp_mask);
224 if (!node)
225 return -ENOMEM;
226 }
227
228 node->val = val;
229 node->aux = aux;
230
231 ret = ulist_rbtree_insert(ulist, node);
232 ASSERT(!ret);
233 list_add_tail(&node->list, &ulist->nodes);
234 ulist->nnodes++;
235
236 return 1;
237 }
238
239 /*
240 * Delete one node from ulist.
241 *
242 * @ulist: ulist to remove node from
243 * @val: value to delete
244 * @aux: aux to delete
245 *
246 * The deletion will only be done when *BOTH* val and aux matches.
247 * Return 0 for successful delete.
248 * Return > 0 for not found.
249 */
250 int ulist_del(struct ulist *ulist, u64 val, u64 aux)
251 {
252 struct ulist_node *node;
253
254 node = ulist_rbtree_search(ulist, val);
255 /* Not found */
256 if (!node)
257 return 1;
258
259 if (node->aux != aux)
260 return 1;
261
262 /* Found and delete */
263 ulist_rbtree_erase(ulist, node);
264 return 0;
265 }
266
267 /*
268 * Iterate ulist.
269 *
270 * @ulist: ulist to iterate
271 * @uiter: iterator variable, initialized with ULIST_ITER_INIT(&iterator)
272 *
273 * Note: locking must be provided by the caller. In case of rwlocks only read
274 * locking is needed
275 *
276 * This function is used to iterate an ulist.
277 * It returns the next element from the ulist or %NULL when the
278 * end is reached. No guarantee is made with respect to the order in which
279 * the elements are returned. They might neither be returned in order of
280 * addition nor in ascending order.
281 * It is allowed to call ulist_add during an enumeration. Newly added items
282 * are guaranteed to show up in the running enumeration.
283 */
284 struct ulist_node *ulist_next(const struct ulist *ulist, struct ulist_iterator *uiter)
285 {
286 struct ulist_node *node;
287
288 if (list_empty(&ulist->nodes))
289 return NULL;
290 if (uiter->cur_list && uiter->cur_list->next == &ulist->nodes)
291 return NULL;
292 if (uiter->cur_list) {
293 uiter->cur_list = uiter->cur_list->next;
294 } else {
295 uiter->cur_list = ulist->nodes.next;
296 }
297 node = list_entry(uiter->cur_list, struct ulist_node, list);
298 return node;
299 }
300
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