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da5c8135 AJ |
1 | /* |
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> | |
180e001c | 8 | #include <linux/export.h> |
da5c8135 AJ |
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 | * 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); | |
cd1b413c | 26 | * ULIST_ITER_INIT(&uiter); |
da5c8135 | 27 | * |
cd1b413c | 28 | * while ((elem = ulist_next(ulist, &uiter)) { |
da5c8135 AJ |
29 | * 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 | */ | |
51 | void ulist_init(struct ulist *ulist) | |
52 | { | |
53 | ulist->nnodes = 0; | |
54 | ulist->nodes = ulist->int_nodes; | |
55 | ulist->nodes_alloced = ULIST_SIZE; | |
f7f82b81 | 56 | ulist->root = RB_ROOT; |
da5c8135 AJ |
57 | } |
58 | EXPORT_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 | */ | |
67 | void 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 */ | |
f7f82b81 | 76 | ulist->root = RB_ROOT; |
da5c8135 AJ |
77 | } |
78 | EXPORT_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 | */ | |
87 | void ulist_reinit(struct ulist *ulist) | |
88 | { | |
89 | ulist_fini(ulist); | |
90 | ulist_init(ulist); | |
91 | } | |
92 | EXPORT_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 | */ | |
2eec6c81 | 100 | struct ulist *ulist_alloc(gfp_t gfp_mask) |
da5c8135 AJ |
101 | { |
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 | } | |
111 | EXPORT_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 | */ | |
119 | void ulist_free(struct ulist *ulist) | |
120 | { | |
121 | if (!ulist) | |
122 | return; | |
123 | ulist_fini(ulist); | |
124 | kfree(ulist); | |
125 | } | |
126 | EXPORT_SYMBOL(ulist_free); | |
127 | ||
f7f82b81 WS |
128 | static 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 | ||
145 | static 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 | ||
da5c8135 AJ |
167 | /** |
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 | */ | |
34d73f54 | 187 | int ulist_add(struct ulist *ulist, u64 val, u64 aux, gfp_t gfp_mask) |
3301958b JS |
188 | { |
189 | return ulist_add_merge(ulist, val, aux, NULL, gfp_mask); | |
190 | } | |
191 | ||
34d73f54 AB |
192 | int ulist_add_merge(struct ulist *ulist, u64 val, u64 aux, |
193 | u64 *old_aux, gfp_t gfp_mask) | |
da5c8135 | 194 | { |
f7f82b81 WS |
195 | 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; | |
da5c8135 AJ |
202 | } |
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; | |
35f0399d LB |
208 | int i; |
209 | ||
210 | for (i = 0; i < ulist->nnodes; i++) | |
211 | rb_erase(&ulist->nodes[i].rb_node, &ulist->root); | |
da5c8135 AJ |
212 | |
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; | |
35f0399d LB |
231 | |
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 | } | |
da5c8135 AJ |
242 | } |
243 | ulist->nodes[ulist->nnodes].val = val; | |
244 | ulist->nodes[ulist->nnodes].aux = aux; | |
f7f82b81 WS |
245 | ret = ulist_rbtree_insert(ulist, &ulist->nodes[ulist->nnodes]); |
246 | BUG_ON(ret); | |
da5c8135 AJ |
247 | ++ulist->nnodes; |
248 | ||
249 | return 1; | |
250 | } | |
251 | EXPORT_SYMBOL(ulist_add); | |
252 | ||
253 | /** | |
254 | * ulist_next - iterate ulist | |
255 | * @ulist: ulist to iterate | |
cd1b413c | 256 | * @uiter: iterator variable, initialized with ULIST_ITER_INIT(&iterator) |
da5c8135 AJ |
257 | * |
258 | * Note: locking must be provided by the caller. In case of rwlocks only read | |
259 | * locking is needed | |
260 | * | |
cd1b413c JS |
261 | * This function is used to iterate an ulist. |
262 | * It returns the next element from the ulist or %NULL when the | |
da5c8135 AJ |
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 | */ | |
cd1b413c | 269 | struct ulist_node *ulist_next(struct ulist *ulist, struct ulist_iterator *uiter) |
da5c8135 | 270 | { |
da5c8135 AJ |
271 | if (ulist->nnodes == 0) |
272 | return NULL; | |
cd1b413c | 273 | if (uiter->i < 0 || uiter->i >= ulist->nnodes) |
da5c8135 AJ |
274 | return NULL; |
275 | ||
cd1b413c | 276 | return &ulist->nodes[uiter->i++]; |
da5c8135 AJ |
277 | } |
278 | EXPORT_SYMBOL(ulist_next); |