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 */
48void ulist_init(struct ulist *ulist)
49{
50 INIT_LIST_HEAD(list: &ulist->nodes);
51 ulist->root = RB_ROOT;
52 ulist->nnodes = 0;
53}
54
55/*
56 * Free up additionally allocated memory for the ulist.
57 *
58 * @ulist: the ulist from which to free the additional memory
59 *
60 * This is useful in cases where the base 'struct ulist' has been statically
61 * allocated.
62 */
63void ulist_release(struct ulist *ulist)
64{
65 struct ulist_node *node;
66 struct ulist_node *next;
67
68 list_for_each_entry_safe(node, next, &ulist->nodes, list) {
69 kfree(objp: node);
70 }
71 ulist->root = RB_ROOT;
72 INIT_LIST_HEAD(list: &ulist->nodes);
73}
74
75/*
76 * Prepare a ulist for reuse.
77 *
78 * @ulist: ulist to be reused
79 *
80 * Free up all additional memory allocated for the list elements and reinit
81 * the ulist.
82 */
83void ulist_reinit(struct ulist *ulist)
84{
85 ulist_release(ulist);
86 ulist_init(ulist);
87}
88
89/*
90 * Dynamically allocate a ulist.
91 *
92 * @gfp_mask: allocation flags to for base allocation
93 *
94 * The allocated ulist will be returned in an initialized state.
95 */
96struct ulist *ulist_alloc(gfp_t gfp_mask)
97{
98 struct ulist *ulist = kmalloc(size: sizeof(*ulist), flags: gfp_mask);
99
100 if (!ulist)
101 return NULL;
102
103 ulist_init(ulist);
104
105 return ulist;
106}
107
108/*
109 * Free dynamically allocated ulist.
110 *
111 * @ulist: ulist to free
112 *
113 * It is not necessary to call ulist_release before.
114 */
115void ulist_free(struct ulist *ulist)
116{
117 if (!ulist)
118 return;
119 ulist_release(ulist);
120 kfree(objp: ulist);
121}
122
123static struct ulist_node *ulist_rbtree_search(struct ulist *ulist, u64 val)
124{
125 struct rb_node *n = ulist->root.rb_node;
126 struct ulist_node *u = NULL;
127
128 while (n) {
129 u = rb_entry(n, struct ulist_node, rb_node);
130 if (u->val < val)
131 n = n->rb_right;
132 else if (u->val > val)
133 n = n->rb_left;
134 else
135 return u;
136 }
137 return NULL;
138}
139
140static void ulist_rbtree_erase(struct ulist *ulist, struct ulist_node *node)
141{
142 rb_erase(&node->rb_node, &ulist->root);
143 list_del(entry: &node->list);
144 kfree(objp: node);
145 BUG_ON(ulist->nnodes == 0);
146 ulist->nnodes--;
147}
148
149static int ulist_rbtree_insert(struct ulist *ulist, struct ulist_node *ins)
150{
151 struct rb_node **p = &ulist->root.rb_node;
152 struct rb_node *parent = NULL;
153 struct ulist_node *cur = NULL;
154
155 while (*p) {
156 parent = *p;
157 cur = rb_entry(parent, struct ulist_node, rb_node);
158
159 if (cur->val < ins->val)
160 p = &(*p)->rb_right;
161 else if (cur->val > ins->val)
162 p = &(*p)->rb_left;
163 else
164 return -EEXIST;
165 }
166 rb_link_node(node: &ins->rb_node, parent, rb_link: p);
167 rb_insert_color(&ins->rb_node, &ulist->root);
168 return 0;
169}
170
171/*
172 * Add an element to the ulist.
173 *
174 * @ulist: ulist to add the element to
175 * @val: value to add to ulist
176 * @aux: auxiliary value to store along with val
177 * @gfp_mask: flags to use for allocation
178 *
179 * Note: locking must be provided by the caller. In case of rwlocks write
180 * locking is needed
181 *
182 * Add an element to a ulist. The @val will only be added if it doesn't
183 * already exist. If it is added, the auxiliary value @aux is stored along with
184 * it. In case @val already exists in the ulist, @aux is ignored, even if
185 * it differs from the already stored value.
186 *
187 * ulist_add returns 0 if @val already exists in ulist and 1 if @val has been
188 * inserted.
189 * In case of allocation failure -ENOMEM is returned and the ulist stays
190 * unaltered.
191 */
192int ulist_add(struct ulist *ulist, u64 val, u64 aux, gfp_t gfp_mask)
193{
194 return ulist_add_merge(ulist, val, aux, NULL, gfp_mask);
195}
196
197int ulist_add_merge(struct ulist *ulist, u64 val, u64 aux,
198 u64 *old_aux, gfp_t gfp_mask)
199{
200 int ret;
201 struct ulist_node *node;
202
203 node = ulist_rbtree_search(ulist, val);
204 if (node) {
205 if (old_aux)
206 *old_aux = node->aux;
207 return 0;
208 }
209 node = kmalloc(size: sizeof(*node), flags: gfp_mask);
210 if (!node)
211 return -ENOMEM;
212
213 node->val = val;
214 node->aux = aux;
215
216 ret = ulist_rbtree_insert(ulist, ins: node);
217 ASSERT(!ret);
218 list_add_tail(new: &node->list, head: &ulist->nodes);
219 ulist->nnodes++;
220
221 return 1;
222}
223
224/*
225 * Delete one node from ulist.
226 *
227 * @ulist: ulist to remove node from
228 * @val: value to delete
229 * @aux: aux to delete
230 *
231 * The deletion will only be done when *BOTH* val and aux matches.
232 * Return 0 for successful delete.
233 * Return > 0 for not found.
234 */
235int ulist_del(struct ulist *ulist, u64 val, u64 aux)
236{
237 struct ulist_node *node;
238
239 node = ulist_rbtree_search(ulist, val);
240 /* Not found */
241 if (!node)
242 return 1;
243
244 if (node->aux != aux)
245 return 1;
246
247 /* Found and delete */
248 ulist_rbtree_erase(ulist, node);
249 return 0;
250}
251
252/*
253 * Iterate ulist.
254 *
255 * @ulist: ulist to iterate
256 * @uiter: iterator variable, initialized with ULIST_ITER_INIT(&iterator)
257 *
258 * Note: locking must be provided by the caller. In case of rwlocks only read
259 * locking is needed
260 *
261 * This function is used to iterate an ulist.
262 * It returns the next element from the ulist or %NULL when the
263 * 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 */
269struct ulist_node *ulist_next(const struct ulist *ulist, struct ulist_iterator *uiter)
270{
271 struct ulist_node *node;
272
273 if (list_empty(head: &ulist->nodes))
274 return NULL;
275 if (uiter->cur_list && uiter->cur_list->next == &ulist->nodes)
276 return NULL;
277 if (uiter->cur_list) {
278 uiter->cur_list = uiter->cur_list->next;
279 } else {
280 uiter->cur_list = ulist->nodes.next;
281 }
282 node = list_entry(uiter->cur_list, struct ulist_node, list);
283 return node;
284}
285

source code of linux/fs/btrfs/ulist.c