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 "ulist.h"
9 #include "ctree.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  * ulist_init - freshly initialize a ulist
42  * @ulist:	the ulist to initialize
43  *
44  * Note: don't use this function to init an already used ulist, use
45  * ulist_reinit instead.
46  */
ulist_init(struct ulist * ulist)47 void ulist_init(struct ulist *ulist)
48 {
49 	INIT_LIST_HEAD(&ulist->nodes);
50 	ulist->root = RB_ROOT;
51 	ulist->nnodes = 0;
52 }
53 
54 /**
55  * ulist_release - free up additionally allocated memory for the ulist
56  * @ulist:	the ulist from which to free the additional memory
57  *
58  * This is useful in cases where the base 'struct ulist' has been statically
59  * allocated.
60  */
ulist_release(struct ulist * ulist)61 void ulist_release(struct ulist *ulist)
62 {
63 	struct ulist_node *node;
64 	struct ulist_node *next;
65 
66 	list_for_each_entry_safe(node, next, &ulist->nodes, list) {
67 		kfree(node);
68 	}
69 	ulist->root = RB_ROOT;
70 	INIT_LIST_HEAD(&ulist->nodes);
71 }
72 
73 /**
74  * ulist_reinit - prepare a ulist for reuse
75  * @ulist:	ulist to be reused
76  *
77  * Free up all additional memory allocated for the list elements and reinit
78  * the ulist.
79  */
ulist_reinit(struct ulist * ulist)80 void ulist_reinit(struct ulist *ulist)
81 {
82 	ulist_release(ulist);
83 	ulist_init(ulist);
84 }
85 
86 /**
87  * ulist_alloc - dynamically allocate a ulist
88  * @gfp_mask:	allocation flags to for base allocation
89  *
90  * The allocated ulist will be returned in an initialized state.
91  */
ulist_alloc(gfp_t gfp_mask)92 struct ulist *ulist_alloc(gfp_t gfp_mask)
93 {
94 	struct ulist *ulist = kmalloc(sizeof(*ulist), gfp_mask);
95 
96 	if (!ulist)
97 		return NULL;
98 
99 	ulist_init(ulist);
100 
101 	return ulist;
102 }
103 
104 /**
105  * ulist_free - free dynamically allocated ulist
106  * @ulist:	ulist to free
107  *
108  * It is not necessary to call ulist_release before.
109  */
ulist_free(struct ulist * ulist)110 void ulist_free(struct ulist *ulist)
111 {
112 	if (!ulist)
113 		return;
114 	ulist_release(ulist);
115 	kfree(ulist);
116 }
117 
ulist_rbtree_search(struct ulist * ulist,u64 val)118 static struct ulist_node *ulist_rbtree_search(struct ulist *ulist, u64 val)
119 {
120 	struct rb_node *n = ulist->root.rb_node;
121 	struct ulist_node *u = NULL;
122 
123 	while (n) {
124 		u = rb_entry(n, struct ulist_node, rb_node);
125 		if (u->val < val)
126 			n = n->rb_right;
127 		else if (u->val > val)
128 			n = n->rb_left;
129 		else
130 			return u;
131 	}
132 	return NULL;
133 }
134 
ulist_rbtree_erase(struct ulist * ulist,struct ulist_node * node)135 static void ulist_rbtree_erase(struct ulist *ulist, struct ulist_node *node)
136 {
137 	rb_erase(&node->rb_node, &ulist->root);
138 	list_del(&node->list);
139 	kfree(node);
140 	BUG_ON(ulist->nnodes == 0);
141 	ulist->nnodes--;
142 }
143 
ulist_rbtree_insert(struct ulist * ulist,struct ulist_node * ins)144 static int ulist_rbtree_insert(struct ulist *ulist, struct ulist_node *ins)
145 {
146 	struct rb_node **p = &ulist->root.rb_node;
147 	struct rb_node *parent = NULL;
148 	struct ulist_node *cur = NULL;
149 
150 	while (*p) {
151 		parent = *p;
152 		cur = rb_entry(parent, struct ulist_node, rb_node);
153 
154 		if (cur->val < ins->val)
155 			p = &(*p)->rb_right;
156 		else if (cur->val > ins->val)
157 			p = &(*p)->rb_left;
158 		else
159 			return -EEXIST;
160 	}
161 	rb_link_node(&ins->rb_node, parent, p);
162 	rb_insert_color(&ins->rb_node, &ulist->root);
163 	return 0;
164 }
165 
166 /**
167  * ulist_add - add an element to the ulist
168  * @ulist:	ulist to add the element to
169  * @val:	value to add to ulist
170  * @aux:	auxiliary value to store along with val
171  * @gfp_mask:	flags to use for allocation
172  *
173  * Note: locking must be provided by the caller. In case of rwlocks write
174  *       locking is needed
175  *
176  * Add an element to a ulist. The @val will only be added if it doesn't
177  * already exist. If it is added, the auxiliary value @aux is stored along with
178  * it. In case @val already exists in the ulist, @aux is ignored, even if
179  * it differs from the already stored value.
180  *
181  * ulist_add returns 0 if @val already exists in ulist and 1 if @val has been
182  * inserted.
183  * In case of allocation failure -ENOMEM is returned and the ulist stays
184  * unaltered.
185  */
ulist_add(struct ulist * ulist,u64 val,u64 aux,gfp_t gfp_mask)186 int ulist_add(struct ulist *ulist, u64 val, u64 aux, gfp_t gfp_mask)
187 {
188 	return ulist_add_merge(ulist, val, aux, NULL, gfp_mask);
189 }
190 
ulist_add_merge(struct ulist * ulist,u64 val,u64 aux,u64 * old_aux,gfp_t gfp_mask)191 int ulist_add_merge(struct ulist *ulist, u64 val, u64 aux,
192 		    u64 *old_aux, gfp_t gfp_mask)
193 {
194 	int ret;
195 	struct ulist_node *node;
196 
197 	node = ulist_rbtree_search(ulist, val);
198 	if (node) {
199 		if (old_aux)
200 			*old_aux = node->aux;
201 		return 0;
202 	}
203 	node = kmalloc(sizeof(*node), gfp_mask);
204 	if (!node)
205 		return -ENOMEM;
206 
207 	node->val = val;
208 	node->aux = aux;
209 
210 	ret = ulist_rbtree_insert(ulist, node);
211 	ASSERT(!ret);
212 	list_add_tail(&node->list, &ulist->nodes);
213 	ulist->nnodes++;
214 
215 	return 1;
216 }
217 
218 /*
219  * ulist_del - delete one node from ulist
220  * @ulist:	ulist to remove node from
221  * @val:	value to delete
222  * @aux:	aux to delete
223  *
224  * The deletion will only be done when *BOTH* val and aux matches.
225  * Return 0 for successful delete.
226  * Return > 0 for not found.
227  */
ulist_del(struct ulist * ulist,u64 val,u64 aux)228 int ulist_del(struct ulist *ulist, u64 val, u64 aux)
229 {
230 	struct ulist_node *node;
231 
232 	node = ulist_rbtree_search(ulist, val);
233 	/* Not found */
234 	if (!node)
235 		return 1;
236 
237 	if (node->aux != aux)
238 		return 1;
239 
240 	/* Found and delete */
241 	ulist_rbtree_erase(ulist, node);
242 	return 0;
243 }
244 
245 /**
246  * ulist_next - iterate ulist
247  * @ulist:	ulist to iterate
248  * @uiter:	iterator variable, initialized with ULIST_ITER_INIT(&iterator)
249  *
250  * Note: locking must be provided by the caller. In case of rwlocks only read
251  *       locking is needed
252  *
253  * This function is used to iterate an ulist.
254  * It returns the next element from the ulist or %NULL when the
255  * end is reached. No guarantee is made with respect to the order in which
256  * the elements are returned. They might neither be returned in order of
257  * addition nor in ascending order.
258  * It is allowed to call ulist_add during an enumeration. Newly added items
259  * are guaranteed to show up in the running enumeration.
260  */
ulist_next(struct ulist * ulist,struct ulist_iterator * uiter)261 struct ulist_node *ulist_next(struct ulist *ulist, struct ulist_iterator *uiter)
262 {
263 	struct ulist_node *node;
264 
265 	if (list_empty(&ulist->nodes))
266 		return NULL;
267 	if (uiter->cur_list && uiter->cur_list->next == &ulist->nodes)
268 		return NULL;
269 	if (uiter->cur_list) {
270 		uiter->cur_list = uiter->cur_list->next;
271 	} else {
272 		uiter->cur_list = ulist->nodes.next;
273 	}
274 	node = list_entry(uiter->cur_list, struct ulist_node, list);
275 	return node;
276 }
277