ulist.c

  1// SPDX-License-Identifier: GPL-2.0
  2/*
  3 * Copyright (C) 2011 STRATO AG
  4 * written by Arne Jansen <sensille@gmx.net>
  5 */
  6
  7#include <linux/slab.h>
  8#include "messages.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 * A sample usage for ulists is the enumeration of directed graphs without
 18 * visiting a node twice. The pseudo-code could look like this:
 19 *
 20 * ulist = ulist_alloc();
 21 * ulist_add(ulist, root);
 22 * ULIST_ITER_INIT(&uiter);
 23 *
 24 * while ((elem = ulist_next(ulist, &uiter)) {
 25 * 	for (all child nodes n in elem)
 26 *		ulist_add(ulist, n);
 27 *	do something useful with the node;
 28 * }
 29 * ulist_free(ulist);
 30 *
 31 * This assumes the graph nodes are addressable by u64. This stems from the
 32 * usage for tree enumeration in btrfs, where the logical addresses are
 33 * 64 bit.
 34 *
 35 * It is also useful for tree enumeration which could be done elegantly
 36 * recursively, but is not possible due to kernel stack limitations. The
 37 * loop would be similar to the above.
 38 */
 39
 40/*
 41 * Freshly initialize a ulist.
 42 *
 43 * @ulist:	the ulist to initialize
 44 *
 45 * Note: don't use this function to init an already used ulist, use
 46 * ulist_reinit instead.
 47 */
 48void ulist_init(struct ulist *ulist)
 49{
 50	INIT_LIST_HEAD(&ulist->nodes);
 51	ulist->root = RB_ROOT;
 52	ulist->nnodes = 0;
 53	ulist->prealloc = NULL;
 54}
 55
 56/*
 57 * Free up additionally allocated memory for the ulist.
 58 *
 59 * @ulist:	the ulist from which to free the additional memory
 60 *
 61 * This is useful in cases where the base 'struct ulist' has been statically
 62 * allocated.
 63 */
 64void ulist_release(struct ulist *ulist)
 65{
 66	struct ulist_node *node;
 67	struct ulist_node *next;
 68
 69	list_for_each_entry_safe(node, next, &ulist->nodes, list) {
 70		kfree(node);
 71	}
 72	kfree(ulist->prealloc);
 73	ulist->prealloc = NULL;
 74	ulist->root = RB_ROOT;
 75	INIT_LIST_HEAD(&ulist->nodes);
 76}
 77
 78/*
 79 * Prepare a ulist for reuse.
 80 *
 81 * @ulist:	ulist to be reused
 82 *
 83 * Free up all additional memory allocated for the list elements and reinit
 84 * the ulist.
 85 */
 86void ulist_reinit(struct ulist *ulist)
 87{
 88	ulist_release(ulist);
 89	ulist_init(ulist);
 90}
 91
 92/*
 93 * Dynamically allocate a ulist.
 94 *
 95 * @gfp_mask:	allocation flags to for base allocation
 96 *
 97 * The allocated ulist will be returned in an initialized state.
 98 */
 99struct ulist *ulist_alloc(gfp_t gfp_mask)
100{
101	struct ulist *ulist = kmalloc(sizeof(*ulist), gfp_mask);
102
103	if (!ulist)
104		return NULL;
105
106	ulist_init(ulist);
107
108	return ulist;
109}
110
111void ulist_prealloc(struct ulist *ulist, gfp_t gfp_mask)
112{
113	if (!ulist->prealloc)
114		ulist->prealloc = kzalloc(sizeof(*ulist->prealloc), gfp_mask);
115}
116
117/*
118 * Free dynamically allocated ulist.
119 *
120 * @ulist:	ulist to free
121 *
122 * It is not necessary to call ulist_release before.
123 */
124void ulist_free(struct ulist *ulist)
125{
126	if (!ulist)
127		return;
128	ulist_release(ulist);
129	kfree(ulist);
130}
131
132static int ulist_node_val_key_cmp(const void *key, const struct rb_node *node)
133{
134	const u64 *val = key;
135	const struct ulist_node *unode = rb_entry(node, struct ulist_node, rb_node);
136
137	if (unode->val < *val)
138		return 1;
139	else if (unode->val > *val)
140		return -1;
141
142	return 0;
143}
144
145static struct ulist_node *ulist_rbtree_search(struct ulist *ulist, u64 val)
146{
147	struct rb_node *node;
148
149	node = rb_find(&val, &ulist->root, ulist_node_val_key_cmp);
150	return rb_entry_safe(node, struct ulist_node, rb_node);
151}
152
153static void ulist_rbtree_erase(struct ulist *ulist, struct ulist_node *node)
154{
155	rb_erase(&node->rb_node, &ulist->root);
156	list_del(&node->list);
157	kfree(node);
158	BUG_ON(ulist->nnodes == 0);
159	ulist->nnodes--;
160}
161
162static int ulist_node_val_cmp(struct rb_node *new, const struct rb_node *existing)
163{
164	const struct ulist_node *unode = rb_entry(new, struct ulist_node, rb_node);
165
166	return ulist_node_val_key_cmp(&unode->val, existing);
167}
168
169static int ulist_rbtree_insert(struct ulist *ulist, struct ulist_node *ins)
170{
171	struct rb_node *node;
172
173	node = rb_find_add(&ins->rb_node, &ulist->root, ulist_node_val_cmp);
174	if (node)
175		return -EEXIST;
176	return 0;
177}
178
179/*
180 * Add an element to the ulist.
181 *
182 * @ulist:	ulist to add the element to
183 * @val:	value to add to ulist
184 * @aux:	auxiliary value to store along with val
185 * @gfp_mask:	flags to use for allocation
186 *
187 * Note: locking must be provided by the caller. In case of rwlocks write
188 *       locking is needed
189 *
190 * Add an element to a ulist. The @val will only be added if it doesn't
191 * already exist. If it is added, the auxiliary value @aux is stored along with
192 * it. In case @val already exists in the ulist, @aux is ignored, even if
193 * it differs from the already stored value.
194 *
195 * ulist_add returns 0 if @val already exists in ulist and 1 if @val has been
196 * inserted.
197 * In case of allocation failure -ENOMEM is returned and the ulist stays
198 * unaltered.
199 */
200int ulist_add(struct ulist *ulist, u64 val, u64 aux, gfp_t gfp_mask)
201{
202	return ulist_add_merge(ulist, val, aux, NULL, gfp_mask);
203}
204
205int ulist_add_merge(struct ulist *ulist, u64 val, u64 aux,
206		    u64 *old_aux, gfp_t gfp_mask)
207{
208	int ret;
209	struct ulist_node *node;
210
211	node = ulist_rbtree_search(ulist, val);
212	if (node) {
213		if (old_aux)
214			*old_aux = node->aux;
215		return 0;
216	}
217
218	if (ulist->prealloc) {
219		node = ulist->prealloc;
220		ulist->prealloc = NULL;
221	} else {
222		node = kmalloc(sizeof(*node), gfp_mask);
223		if (!node)
224			return -ENOMEM;
225	}
226
227	node->val = val;
228	node->aux = aux;
229
230	ret = ulist_rbtree_insert(ulist, node);
231	ASSERT(!ret);
232	list_add_tail(&node->list, &ulist->nodes);
233	ulist->nnodes++;
234
235	return 1;
236}
237
238/*
239 * Delete one node from ulist.
240 *
241 * @ulist:	ulist to remove node from
242 * @val:	value to delete
243 * @aux:	aux to delete
244 *
245 * The deletion will only be done when *BOTH* val and aux matches.
246 * Return 0 for successful delete.
247 * Return > 0 for not found.
248 */
249int ulist_del(struct ulist *ulist, u64 val, u64 aux)
250{
251	struct ulist_node *node;
252
253	node = ulist_rbtree_search(ulist, val);
254	/* Not found */
255	if (!node)
256		return 1;
257
258	if (node->aux != aux)
259		return 1;
260
261	/* Found and delete */
262	ulist_rbtree_erase(ulist, node);
263	return 0;
264}
265
266/*
267 * Iterate ulist.
268 *
269 * @ulist:	ulist to iterate
270 * @uiter:	iterator variable, initialized with ULIST_ITER_INIT(&iterator)
271 *
272 * Note: locking must be provided by the caller. In case of rwlocks only read
273 *       locking is needed
274 *
275 * This function is used to iterate an ulist.
276 * It returns the next element from the ulist or %NULL when the
277 * end is reached. No guarantee is made with respect to the order in which
278 * the elements are returned. They might neither be returned in order of
279 * addition nor in ascending order.
280 * It is allowed to call ulist_add during an enumeration. Newly added items
281 * are guaranteed to show up in the running enumeration.
282 */
283struct ulist_node *ulist_next(const struct ulist *ulist, struct ulist_iterator *uiter)
284{
285	struct ulist_node *node;
286
287	if (list_empty(&ulist->nodes))
288		return NULL;
289	if (uiter->cur_list && uiter->cur_list->next == &ulist->nodes)
290		return NULL;
291	if (uiter->cur_list) {
292		uiter->cur_list = uiter->cur_list->next;
293	} else {
294		uiter->cur_list = ulist->nodes.next;
295	}
296	node = list_entry(uiter->cur_list, struct ulist_node, list);
297	return node;
298}