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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>
8#include <linux/module.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);
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;
56}
57EXPORT_SYMBOL(ulist_init);
58
59/**
60 * ulist_fini - free up additionally allocated memory for the ulist
61 * @ulist: the ulist from which to free the additional memory
62 *
63 * This is useful in cases where the base 'struct ulist' has been statically
64 * allocated.
65 */
66void ulist_fini(struct ulist *ulist)
67{
68 /*
69 * The first ULIST_SIZE elements are stored inline in struct ulist.
70 * Only if more elements are alocated they need to be freed.
71 */
72 if (ulist->nodes_alloced > ULIST_SIZE)
73 kfree(ulist->nodes);
74 ulist->nodes_alloced = 0; /* in case ulist_fini is called twice */
75}
76EXPORT_SYMBOL(ulist_fini);
77
78/**
79 * ulist_reinit - prepare a ulist for reuse
80 * @ulist: ulist to be reused
81 *
82 * Free up all additional memory allocated for the list elements and reinit
83 * the ulist.
84 */
85void ulist_reinit(struct ulist *ulist)
86{
87 ulist_fini(ulist);
88 ulist_init(ulist);
89}
90EXPORT_SYMBOL(ulist_reinit);
91
92/**
93 * ulist_alloc - dynamically allocate a ulist
94 * @gfp_mask: allocation flags to for base allocation
95 *
96 * The allocated ulist will be returned in an initialized state.
97 */
Daniel J Blueman2eec6c82012-04-26 00:37:14 +080098struct ulist *ulist_alloc(gfp_t gfp_mask)
Arne Jansenda5c8132011-09-13 12:29:12 +020099{
100 struct ulist *ulist = kmalloc(sizeof(*ulist), gfp_mask);
101
102 if (!ulist)
103 return NULL;
104
105 ulist_init(ulist);
106
107 return ulist;
108}
109EXPORT_SYMBOL(ulist_alloc);
110
111/**
112 * ulist_free - free dynamically allocated ulist
113 * @ulist: ulist to free
114 *
115 * It is not necessary to call ulist_fini before.
116 */
117void ulist_free(struct ulist *ulist)
118{
119 if (!ulist)
120 return;
121 ulist_fini(ulist);
122 kfree(ulist);
123}
124EXPORT_SYMBOL(ulist_free);
125
126/**
127 * ulist_add - add an element to the ulist
128 * @ulist: ulist to add the element to
129 * @val: value to add to ulist
130 * @aux: auxiliary value to store along with val
131 * @gfp_mask: flags to use for allocation
132 *
133 * Note: locking must be provided by the caller. In case of rwlocks write
134 * locking is needed
135 *
136 * Add an element to a ulist. The @val will only be added if it doesn't
137 * already exist. If it is added, the auxiliary value @aux is stored along with
138 * it. In case @val already exists in the ulist, @aux is ignored, even if
139 * it differs from the already stored value.
140 *
141 * ulist_add returns 0 if @val already exists in ulist and 1 if @val has been
142 * inserted.
143 * In case of allocation failure -ENOMEM is returned and the ulist stays
144 * unaltered.
145 */
146int ulist_add(struct ulist *ulist, u64 val, unsigned long aux,
Daniel J Blueman2eec6c82012-04-26 00:37:14 +0800147 gfp_t gfp_mask)
Arne Jansenda5c8132011-09-13 12:29:12 +0200148{
Jan Schmidt33019582012-05-30 18:05:21 +0200149 return ulist_add_merge(ulist, val, aux, NULL, gfp_mask);
150}
151
152int ulist_add_merge(struct ulist *ulist, u64 val, unsigned long aux,
Chris Mason1e209322012-05-31 16:50:28 -0400153 unsigned long *old_aux, gfp_t gfp_mask)
Jan Schmidt33019582012-05-30 18:05:21 +0200154{
Arne Jansenda5c8132011-09-13 12:29:12 +0200155 int i;
156
157 for (i = 0; i < ulist->nnodes; ++i) {
Jan Schmidt33019582012-05-30 18:05:21 +0200158 if (ulist->nodes[i].val == val) {
159 if (old_aux)
160 *old_aux = ulist->nodes[i].aux;
Arne Jansenda5c8132011-09-13 12:29:12 +0200161 return 0;
Jan Schmidt33019582012-05-30 18:05:21 +0200162 }
Arne Jansenda5c8132011-09-13 12:29:12 +0200163 }
164
165 if (ulist->nnodes >= ulist->nodes_alloced) {
166 u64 new_alloced = ulist->nodes_alloced + 128;
167 struct ulist_node *new_nodes;
168 void *old = NULL;
169
170 /*
171 * if nodes_alloced == ULIST_SIZE no memory has been allocated
172 * yet, so pass NULL to krealloc
173 */
174 if (ulist->nodes_alloced > ULIST_SIZE)
175 old = ulist->nodes;
176
177 new_nodes = krealloc(old, sizeof(*new_nodes) * new_alloced,
178 gfp_mask);
179 if (!new_nodes)
180 return -ENOMEM;
181
182 if (!old)
183 memcpy(new_nodes, ulist->int_nodes,
184 sizeof(ulist->int_nodes));
185
186 ulist->nodes = new_nodes;
187 ulist->nodes_alloced = new_alloced;
188 }
189 ulist->nodes[ulist->nnodes].val = val;
190 ulist->nodes[ulist->nnodes].aux = aux;
191 ++ulist->nnodes;
192
193 return 1;
194}
195EXPORT_SYMBOL(ulist_add);
196
197/**
198 * ulist_next - iterate ulist
199 * @ulist: ulist to iterate
Jan Schmidtcd1b4132012-05-22 14:56:50 +0200200 * @uiter: iterator variable, initialized with ULIST_ITER_INIT(&iterator)
Arne Jansenda5c8132011-09-13 12:29:12 +0200201 *
202 * Note: locking must be provided by the caller. In case of rwlocks only read
203 * locking is needed
204 *
Jan Schmidtcd1b4132012-05-22 14:56:50 +0200205 * This function is used to iterate an ulist.
206 * It returns the next element from the ulist or %NULL when the
Arne Jansenda5c8132011-09-13 12:29:12 +0200207 * end is reached. No guarantee is made with respect to the order in which
208 * the elements are returned. They might neither be returned in order of
209 * addition nor in ascending order.
210 * It is allowed to call ulist_add during an enumeration. Newly added items
211 * are guaranteed to show up in the running enumeration.
212 */
Jan Schmidtcd1b4132012-05-22 14:56:50 +0200213struct ulist_node *ulist_next(struct ulist *ulist, struct ulist_iterator *uiter)
Arne Jansenda5c8132011-09-13 12:29:12 +0200214{
Arne Jansenda5c8132011-09-13 12:29:12 +0200215 if (ulist->nnodes == 0)
216 return NULL;
Jan Schmidtcd1b4132012-05-22 14:56:50 +0200217 if (uiter->i < 0 || uiter->i >= ulist->nnodes)
Arne Jansenda5c8132011-09-13 12:29:12 +0200218 return NULL;
219
Jan Schmidtcd1b4132012-05-22 14:56:50 +0200220 return &ulist->nodes[uiter->i++];
Arne Jansenda5c8132011-09-13 12:29:12 +0200221}
222EXPORT_SYMBOL(ulist_next);