Branch data Line data Source code
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>
8 : : #include <linux/export.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 : : * 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);
26 : : * ULIST_ITER_INIT(&uiter);
27 : : *
28 : : * while ((elem = ulist_next(ulist, &uiter)) {
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 : 0 : void ulist_init(struct ulist *ulist)
52 : : {
53 : 0 : ulist->nnodes = 0;
54 : 0 : ulist->nodes = ulist->int_nodes;
55 : 0 : ulist->nodes_alloced = ULIST_SIZE;
56 : 0 : ulist->root = RB_ROOT;
57 : 0 : }
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 : 0 : 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 [ # # ][ # # ]: 0 : if (ulist->nodes_alloced > ULIST_SIZE)
[ # # ]
74 : 0 : kfree(ulist->nodes);
75 : 0 : ulist->nodes_alloced = 0; /* in case ulist_fini is called twice */
76 : 0 : ulist->root = RB_ROOT;
77 : 0 : }
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 : 0 : void ulist_reinit(struct ulist *ulist)
88 : : {
89 : : ulist_fini(ulist);
90 : : ulist_init(ulist);
91 : 0 : }
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 : : */
100 : 0 : struct ulist *ulist_alloc(gfp_t gfp_mask)
101 : : {
102 : : struct ulist *ulist = kmalloc(sizeof(*ulist), gfp_mask);
103 : :
104 [ # # ]: 0 : if (!ulist)
105 : : return NULL;
106 : :
107 : : ulist_init(ulist);
108 : :
109 : 0 : 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 : 0 : void ulist_free(struct ulist *ulist)
120 : : {
121 [ # # ]: 0 : if (!ulist)
122 : 0 : return;
123 : : ulist_fini(ulist);
124 : 0 : kfree(ulist);
125 : : }
126 : : EXPORT_SYMBOL(ulist_free);
127 : :
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 [ # # ]: 0 : while (n) {
134 : 0 : u = rb_entry(n, struct ulist_node, rb_node);
135 [ # # ]: 0 : if (u->val < val)
136 : 0 : n = n->rb_right;
137 [ # # ]: 0 : else if (u->val > val)
138 : 0 : n = n->rb_left;
139 : : else
140 : : return u;
141 : : }
142 : : return NULL;
143 : : }
144 : :
145 : 0 : static int ulist_rbtree_insert(struct ulist *ulist, struct ulist_node *ins)
146 : : {
147 : 0 : struct rb_node **p = &ulist->root.rb_node;
148 : : struct rb_node *parent = NULL;
149 : : struct ulist_node *cur = NULL;
150 : :
151 [ # # ]: 0 : while (*p) {
152 : : parent = *p;
153 : : cur = rb_entry(parent, struct ulist_node, rb_node);
154 : :
155 [ # # ]: 0 : if (cur->val < ins->val)
156 : 0 : p = &(*p)->rb_right;
157 [ # # ]: 0 : else if (cur->val > ins->val)
158 : 0 : p = &(*p)->rb_left;
159 : : else
160 : : return -EEXIST;
161 : : }
162 : 0 : rb_link_node(&ins->rb_node, parent, p);
163 : 0 : rb_insert_color(&ins->rb_node, &ulist->root);
164 : 0 : return 0;
165 : : }
166 : :
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 : : */
187 : 0 : int ulist_add(struct ulist *ulist, u64 val, u64 aux, gfp_t gfp_mask)
188 : : {
189 : 0 : return ulist_add_merge(ulist, val, aux, NULL, gfp_mask);
190 : : }
191 : :
192 : 0 : int ulist_add_merge(struct ulist *ulist, u64 val, u64 aux,
193 : : u64 *old_aux, gfp_t gfp_mask)
194 : : {
195 : : int ret = 0;
196 : : struct ulist_node *node = NULL;
197 : : node = ulist_rbtree_search(ulist, val);
198 [ # # ]: 0 : if (node) {
199 [ # # ]: 0 : if (old_aux)
200 : 0 : *old_aux = node->aux;
201 : : return 0;
202 : : }
203 : :
204 [ # # ]: 0 : if (ulist->nnodes >= ulist->nodes_alloced) {
205 : 0 : u64 new_alloced = ulist->nodes_alloced + 128;
206 : : struct ulist_node *new_nodes;
207 : : void *old = NULL;
208 : : int i;
209 : :
210 [ # # ]: 0 : for (i = 0; i < ulist->nnodes; i++)
211 : 0 : rb_erase(&ulist->nodes[i].rb_node, &ulist->root);
212 : :
213 : : /*
214 : : * if nodes_alloced == ULIST_SIZE no memory has been allocated
215 : : * yet, so pass NULL to krealloc
216 : : */
217 [ # # ]: 0 : if (ulist->nodes_alloced > ULIST_SIZE)
218 : 0 : old = ulist->nodes;
219 : :
220 : 0 : new_nodes = krealloc(old, sizeof(*new_nodes) * new_alloced,
221 : : gfp_mask);
222 [ # # ]: 0 : if (!new_nodes)
223 : : return -ENOMEM;
224 : :
225 [ # # ]: 0 : if (!old)
226 : 0 : memcpy(new_nodes, ulist->int_nodes,
227 : : sizeof(ulist->int_nodes));
228 : :
229 : 0 : ulist->nodes = new_nodes;
230 : 0 : ulist->nodes_alloced = new_alloced;
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 [ # # ]: 0 : for (i = 0; i < ulist->nnodes; i++) {
238 : 0 : ret = ulist_rbtree_insert(ulist, &ulist->nodes[i]);
239 [ # # ]: 0 : if (ret < 0)
240 : : return ret;
241 : : }
242 : : }
243 : 0 : ulist->nodes[ulist->nnodes].val = val;
244 : 0 : ulist->nodes[ulist->nnodes].aux = aux;
245 : 0 : ret = ulist_rbtree_insert(ulist, &ulist->nodes[ulist->nnodes]);
246 [ # # ]: 0 : BUG_ON(ret);
247 : 0 : ++ulist->nnodes;
248 : :
249 : 0 : return 1;
250 : : }
251 : : EXPORT_SYMBOL(ulist_add);
252 : :
253 : : /**
254 : : * ulist_next - iterate ulist
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 : : */
269 : 0 : struct ulist_node *ulist_next(struct ulist *ulist, struct ulist_iterator *uiter)
270 : : {
271 [ # # ]: 0 : if (ulist->nnodes == 0)
272 : : return NULL;
273 [ # # ][ # # ]: 0 : if (uiter->i < 0 || uiter->i >= ulist->nnodes)
274 : : return NULL;
275 : :
276 : 0 : return &ulist->nodes[uiter->i++];
277 : : }
278 : : EXPORT_SYMBOL(ulist_next);
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