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 void ulist_init(struct ulist *ulist) 52 { 53 ulist->nnodes = 0; 54 ulist->nodes = ulist->int_nodes; 55 ulist->nodes_alloced = ULIST_SIZE; 56 ulist->root = RB_ROOT; 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 */ 76 ulist->root = RB_ROOT; 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 */ 100 struct ulist *ulist_alloc(gfp_t gfp_mask) 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); 127 128 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 } 166 167 /** 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 int ulist_add(struct ulist *ulist, u64 val, u64 aux, gfp_t gfp_mask) 188 { 189 return ulist_add_merge(ulist, val, aux, NULL, gfp_mask); 190 } 191 192 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 if (node) { 199 if (old_aux) 200 *old_aux = node->aux; 201 return 0; 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; 208 209 /* 210 * if nodes_alloced == ULIST_SIZE no memory has been allocated 211 * yet, so pass NULL to krealloc 212 */ 213 if (ulist->nodes_alloced > ULIST_SIZE) 214 old = ulist->nodes; 215 216 new_nodes = krealloc(old, sizeof(*new_nodes) * new_alloced, 217 gfp_mask); 218 if (!new_nodes) 219 return -ENOMEM; 220 221 if (!old) 222 memcpy(new_nodes, ulist->int_nodes, 223 sizeof(ulist->int_nodes)); 224 225 ulist->nodes = new_nodes; 226 ulist->nodes_alloced = new_alloced; 227 } 228 ulist->nodes[ulist->nnodes].val = val; 229 ulist->nodes[ulist->nnodes].aux = aux; 230 ret = ulist_rbtree_insert(ulist, &ulist->nodes[ulist->nnodes]); 231 BUG_ON(ret); 232 ++ulist->nnodes; 233 234 return 1; 235 } 236 EXPORT_SYMBOL(ulist_add); 237 238 /** 239 * ulist_next - iterate ulist 240 * @ulist: ulist to iterate 241 * @uiter: iterator variable, initialized with ULIST_ITER_INIT(&iterator) 242 * 243 * Note: locking must be provided by the caller. In case of rwlocks only read 244 * locking is needed 245 * 246 * This function is used to iterate an ulist. 247 * It returns the next element from the ulist or %NULL when the 248 * end is reached. No guarantee is made with respect to the order in which 249 * the elements are returned. They might neither be returned in order of 250 * addition nor in ascending order. 251 * It is allowed to call ulist_add during an enumeration. Newly added items 252 * are guaranteed to show up in the running enumeration. 253 */ 254 struct ulist_node *ulist_next(struct ulist *ulist, struct ulist_iterator *uiter) 255 { 256 if (ulist->nnodes == 0) 257 return NULL; 258 if (uiter->i < 0 || uiter->i >= ulist->nnodes) 259 return NULL; 260 261 return &ulist->nodes[uiter->i++]; 262 } 263 EXPORT_SYMBOL(ulist_next); 264