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  */
ulist_init(struct ulist * ulist)48 void 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  */
ulist_release(struct ulist * ulist)64 void 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  */
ulist_reinit(struct ulist * ulist)86 void 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  */
ulist_alloc(gfp_t gfp_mask)99 struct 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 
ulist_prealloc(struct ulist * ulist,gfp_t gfp_mask)111 void 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  */
ulist_free(struct ulist * ulist)124 void ulist_free(struct ulist *ulist)
125 {
126 	if (!ulist)
127 		return;
128 	ulist_release(ulist);
129 	kfree(ulist);
130 }
131 
ulist_rbtree_search(struct ulist * ulist,u64 val)132 static struct ulist_node *ulist_rbtree_search(struct ulist *ulist, u64 val)
133 {
134 	struct rb_node *n = ulist->root.rb_node;
135 	struct ulist_node *u = NULL;
136 
137 	while (n) {
138 		u = rb_entry(n, struct ulist_node, rb_node);
139 		if (u->val < val)
140 			n = n->rb_right;
141 		else if (u->val > val)
142 			n = n->rb_left;
143 		else
144 			return u;
145 	}
146 	return NULL;
147 }
148 
ulist_rbtree_erase(struct ulist * ulist,struct ulist_node * node)149 static void ulist_rbtree_erase(struct ulist *ulist, struct ulist_node *node)
150 {
151 	rb_erase(&node->rb_node, &ulist->root);
152 	list_del(&node->list);
153 	kfree(node);
154 	BUG_ON(ulist->nnodes == 0);
155 	ulist->nnodes--;
156 }
157 
ulist_rbtree_insert(struct ulist * ulist,struct ulist_node * ins)158 static int ulist_rbtree_insert(struct ulist *ulist, struct ulist_node *ins)
159 {
160 	struct rb_node **p = &ulist->root.rb_node;
161 	struct rb_node *parent = NULL;
162 	struct ulist_node *cur = NULL;
163 
164 	while (*p) {
165 		parent = *p;
166 		cur = rb_entry(parent, struct ulist_node, rb_node);
167 
168 		if (cur->val < ins->val)
169 			p = &(*p)->rb_right;
170 		else if (cur->val > ins->val)
171 			p = &(*p)->rb_left;
172 		else
173 			return -EEXIST;
174 	}
175 	rb_link_node(&ins->rb_node, parent, p);
176 	rb_insert_color(&ins->rb_node, &ulist->root);
177 	return 0;
178 }
179 
180 /*
181  * Add an element to the ulist.
182  *
183  * @ulist:	ulist to add the element to
184  * @val:	value to add to ulist
185  * @aux:	auxiliary value to store along with val
186  * @gfp_mask:	flags to use for allocation
187  *
188  * Note: locking must be provided by the caller. In case of rwlocks write
189  *       locking is needed
190  *
191  * Add an element to a ulist. The @val will only be added if it doesn't
192  * already exist. If it is added, the auxiliary value @aux is stored along with
193  * it. In case @val already exists in the ulist, @aux is ignored, even if
194  * it differs from the already stored value.
195  *
196  * ulist_add returns 0 if @val already exists in ulist and 1 if @val has been
197  * inserted.
198  * In case of allocation failure -ENOMEM is returned and the ulist stays
199  * unaltered.
200  */
ulist_add(struct ulist * ulist,u64 val,u64 aux,gfp_t gfp_mask)201 int ulist_add(struct ulist *ulist, u64 val, u64 aux, gfp_t gfp_mask)
202 {
203 	return ulist_add_merge(ulist, val, aux, NULL, gfp_mask);
204 }
205 
ulist_add_merge(struct ulist * ulist,u64 val,u64 aux,u64 * old_aux,gfp_t gfp_mask)206 int ulist_add_merge(struct ulist *ulist, u64 val, u64 aux,
207 		    u64 *old_aux, gfp_t gfp_mask)
208 {
209 	int ret;
210 	struct ulist_node *node;
211 
212 	node = ulist_rbtree_search(ulist, val);
213 	if (node) {
214 		if (old_aux)
215 			*old_aux = node->aux;
216 		return 0;
217 	}
218 
219 	if (ulist->prealloc) {
220 		node = ulist->prealloc;
221 		ulist->prealloc = NULL;
222 	} else {
223 		node = kmalloc(sizeof(*node), gfp_mask);
224 		if (!node)
225 			return -ENOMEM;
226 	}
227 
228 	node->val = val;
229 	node->aux = aux;
230 
231 	ret = ulist_rbtree_insert(ulist, node);
232 	ASSERT(!ret);
233 	list_add_tail(&node->list, &ulist->nodes);
234 	ulist->nnodes++;
235 
236 	return 1;
237 }
238 
239 /*
240  * Delete one node from ulist.
241  *
242  * @ulist:	ulist to remove node from
243  * @val:	value to delete
244  * @aux:	aux to delete
245  *
246  * The deletion will only be done when *BOTH* val and aux matches.
247  * Return 0 for successful delete.
248  * Return > 0 for not found.
249  */
ulist_del(struct ulist * ulist,u64 val,u64 aux)250 int ulist_del(struct ulist *ulist, u64 val, u64 aux)
251 {
252 	struct ulist_node *node;
253 
254 	node = ulist_rbtree_search(ulist, val);
255 	/* Not found */
256 	if (!node)
257 		return 1;
258 
259 	if (node->aux != aux)
260 		return 1;
261 
262 	/* Found and delete */
263 	ulist_rbtree_erase(ulist, node);
264 	return 0;
265 }
266 
267 /*
268  * Iterate ulist.
269  *
270  * @ulist:	ulist to iterate
271  * @uiter:	iterator variable, initialized with ULIST_ITER_INIT(&iterator)
272  *
273  * Note: locking must be provided by the caller. In case of rwlocks only read
274  *       locking is needed
275  *
276  * This function is used to iterate an ulist.
277  * It returns the next element from the ulist or %NULL when the
278  * end is reached. No guarantee is made with respect to the order in which
279  * the elements are returned. They might neither be returned in order of
280  * addition nor in ascending order.
281  * It is allowed to call ulist_add during an enumeration. Newly added items
282  * are guaranteed to show up in the running enumeration.
283  */
ulist_next(const struct ulist * ulist,struct ulist_iterator * uiter)284 struct ulist_node *ulist_next(const struct ulist *ulist, struct ulist_iterator *uiter)
285 {
286 	struct ulist_node *node;
287 
288 	if (list_empty(&ulist->nodes))
289 		return NULL;
290 	if (uiter->cur_list && uiter->cur_list->next == &ulist->nodes)
291 		return NULL;
292 	if (uiter->cur_list) {
293 		uiter->cur_list = uiter->cur_list->next;
294 	} else {
295 		uiter->cur_list = ulist->nodes.next;
296 	}
297 	node = list_entry(uiter->cur_list, struct ulist_node, list);
298 	return node;
299 }
300