arm: socfpga: Enable ARM_TWD for socfpga
[linux-2.6.git] / fs / btrfs / ulist.c
blobb0a523b2c60ee8e73cd5165382892918ddad269e
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 */
7 #include <linux/slab.h>
8 #include <linux/export.h>
9 #include "ulist.h"
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.
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.
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:
24 * ulist = ulist_alloc();
25 * ulist_add(ulist, root);
26 * ULIST_ITER_INIT(&uiter);
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);
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.
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.
44 /**
45 * ulist_init - freshly initialize a ulist
46 * @ulist: the ulist to initialize
48 * Note: don't use this function to init an already used ulist, use
49 * ulist_reinit instead.
51 void ulist_init(struct ulist *ulist)
53 ulist->nnodes = 0;
54 ulist->nodes = ulist->int_nodes;
55 ulist->nodes_alloced = ULIST_SIZE;
56 ulist->root = RB_ROOT;
58 EXPORT_SYMBOL(ulist_init);
60 /**
61 * ulist_fini - free up additionally allocated memory for the ulist
62 * @ulist: the ulist from which to free the additional memory
64 * This is useful in cases where the base 'struct ulist' has been statically
65 * allocated.
67 void ulist_fini(struct ulist *ulist)
70 * The first ULIST_SIZE elements are stored inline in struct ulist.
71 * Only if more elements are alocated they need to be freed.
73 if (ulist->nodes_alloced > ULIST_SIZE)
74 kfree(ulist->nodes);
75 ulist->nodes_alloced = 0; /* in case ulist_fini is called twice */
76 ulist->root = RB_ROOT;
78 EXPORT_SYMBOL(ulist_fini);
80 /**
81 * ulist_reinit - prepare a ulist for reuse
82 * @ulist: ulist to be reused
84 * Free up all additional memory allocated for the list elements and reinit
85 * the ulist.
87 void ulist_reinit(struct ulist *ulist)
89 ulist_fini(ulist);
90 ulist_init(ulist);
92 EXPORT_SYMBOL(ulist_reinit);
94 /**
95 * ulist_alloc - dynamically allocate a ulist
96 * @gfp_mask: allocation flags to for base allocation
98 * The allocated ulist will be returned in an initialized state.
100 struct ulist *ulist_alloc(gfp_t gfp_mask)
102 struct ulist *ulist = kmalloc(sizeof(*ulist), gfp_mask);
104 if (!ulist)
105 return NULL;
107 ulist_init(ulist);
109 return ulist;
111 EXPORT_SYMBOL(ulist_alloc);
114 * ulist_free - free dynamically allocated ulist
115 * @ulist: ulist to free
117 * It is not necessary to call ulist_fini before.
119 void ulist_free(struct ulist *ulist)
121 if (!ulist)
122 return;
123 ulist_fini(ulist);
124 kfree(ulist);
126 EXPORT_SYMBOL(ulist_free);
128 static struct ulist_node *ulist_rbtree_search(struct ulist *ulist, u64 val)
130 struct rb_node *n = ulist->root.rb_node;
131 struct ulist_node *u = NULL;
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;
142 return NULL;
145 static int ulist_rbtree_insert(struct ulist *ulist, struct ulist_node *ins)
147 struct rb_node **p = &ulist->root.rb_node;
148 struct rb_node *parent = NULL;
149 struct ulist_node *cur = NULL;
151 while (*p) {
152 parent = *p;
153 cur = rb_entry(parent, struct ulist_node, rb_node);
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;
162 rb_link_node(&ins->rb_node, parent, p);
163 rb_insert_color(&ins->rb_node, &ulist->root);
164 return 0;
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
174 * Note: locking must be provided by the caller. In case of rwlocks write
175 * locking is needed
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.
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.
187 int ulist_add(struct ulist *ulist, u64 val, u64 aux, gfp_t gfp_mask)
189 return ulist_add_merge(ulist, val, aux, NULL, gfp_mask);
192 int ulist_add_merge(struct ulist *ulist, u64 val, u64 aux,
193 u64 *old_aux, gfp_t gfp_mask)
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;
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;
208 int i;
210 for (i = 0; i < ulist->nnodes; i++)
211 rb_erase(&ulist->nodes[i].rb_node, &ulist->root);
214 * if nodes_alloced == ULIST_SIZE no memory has been allocated
215 * yet, so pass NULL to krealloc
217 if (ulist->nodes_alloced > ULIST_SIZE)
218 old = ulist->nodes;
220 new_nodes = krealloc(old, sizeof(*new_nodes) * new_alloced,
221 gfp_mask);
222 if (!new_nodes)
223 return -ENOMEM;
225 if (!old)
226 memcpy(new_nodes, ulist->int_nodes,
227 sizeof(ulist->int_nodes));
229 ulist->nodes = new_nodes;
230 ulist->nodes_alloced = new_alloced;
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.
237 for (i = 0; i < ulist->nnodes; i++) {
238 ret = ulist_rbtree_insert(ulist, &ulist->nodes[i]);
239 if (ret < 0)
240 return ret;
243 ulist->nodes[ulist->nnodes].val = val;
244 ulist->nodes[ulist->nnodes].aux = aux;
245 ret = ulist_rbtree_insert(ulist, &ulist->nodes[ulist->nnodes]);
246 BUG_ON(ret);
247 ++ulist->nnodes;
249 return 1;
251 EXPORT_SYMBOL(ulist_add);
254 * ulist_next - iterate ulist
255 * @ulist: ulist to iterate
256 * @uiter: iterator variable, initialized with ULIST_ITER_INIT(&iterator)
258 * Note: locking must be provided by the caller. In case of rwlocks only read
259 * locking is needed
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.
269 struct ulist_node *ulist_next(struct ulist *ulist, struct ulist_iterator *uiter)
271 if (ulist->nnodes == 0)
272 return NULL;
273 if (uiter->i < 0 || uiter->i >= ulist->nnodes)
274 return NULL;
276 return &ulist->nodes[uiter->i++];
278 EXPORT_SYMBOL(ulist_next);