1 /*
2  * lib/parman.c - Manager for linear priority array areas
3  * Copyright (c) 2017 Mellanox Technologies. All rights reserved.
4  * Copyright (c) 2017 Jiri Pirko <jiri@mellanox.com>
5  *
6  * Redistribution and use in source and binary forms, with or without
7  * modification, are permitted provided that the following conditions are met:
8  *
9  * 1. Redistributions of source code must retain the above copyright
10  *    notice, this list of conditions and the following disclaimer.
11  * 2. Redistributions in binary form must reproduce the above copyright
12  *    notice, this list of conditions and the following disclaimer in the
13  *    documentation and/or other materials provided with the distribution.
14  * 3. Neither the names of the copyright holders nor the names of its
15  *    contributors may be used to endorse or promote products derived from
16  *    this software without specific prior written permission.
17  *
18  * Alternatively, this software may be distributed under the terms of the
19  * GNU General Public License ("GPL") version 2 as published by the Free
20  * Software Foundation.
21  *
22  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
23  * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
24  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
25  * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
26  * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
27  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
28  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
29  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
30  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
31  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
32  * POSSIBILITY OF SUCH DAMAGE.
33  */
34 
35 #include <linux/kernel.h>
36 #include <linux/module.h>
37 #include <linux/slab.h>
38 #include <linux/export.h>
39 #include <linux/list.h>
40 #include <linux/err.h>
41 #include <linux/parman.h>
42 
43 struct parman_algo {
44 	int (*item_add)(struct parman *parman, struct parman_prio *prio,
45 			struct parman_item *item);
46 	void (*item_remove)(struct parman *parman, struct parman_prio *prio,
47 			    struct parman_item *item);
48 };
49 
50 struct parman {
51 	const struct parman_ops *ops;
52 	void *priv;
53 	const struct parman_algo *algo;
54 	unsigned long count;
55 	unsigned long limit_count;
56 	struct list_head prio_list;
57 };
58 
parman_enlarge(struct parman * parman)59 static int parman_enlarge(struct parman *parman)
60 {
61 	unsigned long new_count = parman->limit_count +
62 				  parman->ops->resize_step;
63 	int err;
64 
65 	err = parman->ops->resize(parman->priv, new_count);
66 	if (err)
67 		return err;
68 	parman->limit_count = new_count;
69 	return 0;
70 }
71 
parman_shrink(struct parman * parman)72 static int parman_shrink(struct parman *parman)
73 {
74 	unsigned long new_count = parman->limit_count -
75 				  parman->ops->resize_step;
76 	int err;
77 
78 	if (new_count < parman->ops->base_count)
79 		return 0;
80 	err = parman->ops->resize(parman->priv, new_count);
81 	if (err)
82 		return err;
83 	parman->limit_count = new_count;
84 	return 0;
85 }
86 
parman_prio_used(struct parman_prio * prio)87 static bool parman_prio_used(struct parman_prio *prio)
88 {
89 	return !list_empty(&prio->item_list);
90 }
91 
parman_prio_first_item(struct parman_prio * prio)92 static struct parman_item *parman_prio_first_item(struct parman_prio *prio)
93 {
94 	return list_first_entry(&prio->item_list,
95 				typeof(struct parman_item), list);
96 }
97 
parman_prio_first_index(struct parman_prio * prio)98 static unsigned long parman_prio_first_index(struct parman_prio *prio)
99 {
100 	return parman_prio_first_item(prio)->index;
101 }
102 
parman_prio_last_item(struct parman_prio * prio)103 static struct parman_item *parman_prio_last_item(struct parman_prio *prio)
104 {
105 	return list_last_entry(&prio->item_list,
106 			       typeof(struct parman_item), list);
107 }
108 
parman_prio_last_index(struct parman_prio * prio)109 static unsigned long parman_prio_last_index(struct parman_prio *prio)
110 {
111 	return parman_prio_last_item(prio)->index;
112 }
113 
parman_lsort_new_index_find(struct parman * parman,struct parman_prio * prio)114 static unsigned long parman_lsort_new_index_find(struct parman *parman,
115 						 struct parman_prio *prio)
116 {
117 	list_for_each_entry_from_reverse(prio, &parman->prio_list, list) {
118 		if (!parman_prio_used(prio))
119 			continue;
120 		return parman_prio_last_index(prio) + 1;
121 	}
122 	return 0;
123 }
124 
__parman_prio_move(struct parman * parman,struct parman_prio * prio,struct parman_item * item,unsigned long to_index,unsigned long count)125 static void __parman_prio_move(struct parman *parman, struct parman_prio *prio,
126 			       struct parman_item *item, unsigned long to_index,
127 			       unsigned long count)
128 {
129 	parman->ops->move(parman->priv, item->index, to_index, count);
130 }
131 
parman_prio_shift_down(struct parman * parman,struct parman_prio * prio)132 static void parman_prio_shift_down(struct parman *parman,
133 				   struct parman_prio *prio)
134 {
135 	struct parman_item *item;
136 	unsigned long to_index;
137 
138 	if (!parman_prio_used(prio))
139 		return;
140 	item = parman_prio_first_item(prio);
141 	to_index = parman_prio_last_index(prio) + 1;
142 	__parman_prio_move(parman, prio, item, to_index, 1);
143 	list_move_tail(&item->list, &prio->item_list);
144 	item->index = to_index;
145 }
146 
parman_prio_shift_up(struct parman * parman,struct parman_prio * prio)147 static void parman_prio_shift_up(struct parman *parman,
148 				 struct parman_prio *prio)
149 {
150 	struct parman_item *item;
151 	unsigned long to_index;
152 
153 	if (!parman_prio_used(prio))
154 		return;
155 	item = parman_prio_last_item(prio);
156 	to_index = parman_prio_first_index(prio) - 1;
157 	__parman_prio_move(parman, prio, item, to_index, 1);
158 	list_move(&item->list, &prio->item_list);
159 	item->index = to_index;
160 }
161 
parman_prio_item_remove(struct parman * parman,struct parman_prio * prio,struct parman_item * item)162 static void parman_prio_item_remove(struct parman *parman,
163 				    struct parman_prio *prio,
164 				    struct parman_item *item)
165 {
166 	struct parman_item *last_item;
167 	unsigned long to_index;
168 
169 	last_item = parman_prio_last_item(prio);
170 	if (last_item == item) {
171 		list_del(&item->list);
172 		return;
173 	}
174 	to_index = item->index;
175 	__parman_prio_move(parman, prio, last_item, to_index, 1);
176 	list_del(&last_item->list);
177 	list_replace(&item->list, &last_item->list);
178 	last_item->index = to_index;
179 }
180 
parman_lsort_item_add(struct parman * parman,struct parman_prio * prio,struct parman_item * item)181 static int parman_lsort_item_add(struct parman *parman,
182 				 struct parman_prio *prio,
183 				 struct parman_item *item)
184 {
185 	struct parman_prio *prio2;
186 	unsigned long new_index;
187 	int err;
188 
189 	if (parman->count + 1 > parman->limit_count) {
190 		err = parman_enlarge(parman);
191 		if (err)
192 			return err;
193 	}
194 
195 	new_index = parman_lsort_new_index_find(parman, prio);
196 	list_for_each_entry_reverse(prio2, &parman->prio_list, list) {
197 		if (prio2 == prio)
198 			break;
199 		parman_prio_shift_down(parman, prio2);
200 	}
201 	item->index = new_index;
202 	list_add_tail(&item->list, &prio->item_list);
203 	parman->count++;
204 	return 0;
205 }
206 
parman_lsort_item_remove(struct parman * parman,struct parman_prio * prio,struct parman_item * item)207 static void parman_lsort_item_remove(struct parman *parman,
208 				     struct parman_prio *prio,
209 				     struct parman_item *item)
210 {
211 	parman_prio_item_remove(parman, prio, item);
212 	list_for_each_entry_continue(prio, &parman->prio_list, list)
213 		parman_prio_shift_up(parman, prio);
214 	parman->count--;
215 	if (parman->limit_count - parman->count >= parman->ops->resize_step)
216 		parman_shrink(parman);
217 }
218 
219 static const struct parman_algo parman_lsort = {
220 	.item_add	= parman_lsort_item_add,
221 	.item_remove	= parman_lsort_item_remove,
222 };
223 
224 static const struct parman_algo *parman_algos[] = {
225 	&parman_lsort,
226 };
227 
228 /**
229  * parman_create - creates a new parman instance
230  * @ops:	caller-specific callbacks
231  * @priv:	pointer to a private data passed to the ops
232  *
233  * Note: all locking must be provided by the caller.
234  *
235  * Each parman instance manages an array area with chunks of entries
236  * with the same priority. Consider following example:
237  *
238  * item 1 with prio 10
239  * item 2 with prio 10
240  * item 3 with prio 10
241  * item 4 with prio 20
242  * item 5 with prio 20
243  * item 6 with prio 30
244  * item 7 with prio 30
245  * item 8 with prio 30
246  *
247  * In this example, there are 3 priority chunks. The order of the priorities
248  * matters, however the order of items within a single priority chunk does not
249  * matter. So the same array could be ordered as follows:
250  *
251  * item 2 with prio 10
252  * item 3 with prio 10
253  * item 1 with prio 10
254  * item 5 with prio 20
255  * item 4 with prio 20
256  * item 7 with prio 30
257  * item 8 with prio 30
258  * item 6 with prio 30
259  *
260  * The goal of parman is to maintain the priority ordering. The caller
261  * provides @ops with callbacks parman uses to move the items
262  * and resize the array area.
263  *
264  * Returns a pointer to newly created parman instance in case of success,
265  * otherwise it returns NULL.
266  */
parman_create(const struct parman_ops * ops,void * priv)267 struct parman *parman_create(const struct parman_ops *ops, void *priv)
268 {
269 	struct parman *parman;
270 
271 	parman = kzalloc(sizeof(*parman), GFP_KERNEL);
272 	if (!parman)
273 		return NULL;
274 	INIT_LIST_HEAD(&parman->prio_list);
275 	parman->ops = ops;
276 	parman->priv = priv;
277 	parman->limit_count = ops->base_count;
278 	parman->algo = parman_algos[ops->algo];
279 	return parman;
280 }
281 EXPORT_SYMBOL(parman_create);
282 
283 /**
284  * parman_destroy - destroys existing parman instance
285  * @parman:	parman instance
286  *
287  * Note: all locking must be provided by the caller.
288  */
parman_destroy(struct parman * parman)289 void parman_destroy(struct parman *parman)
290 {
291 	WARN_ON(!list_empty(&parman->prio_list));
292 	kfree(parman);
293 }
294 EXPORT_SYMBOL(parman_destroy);
295 
296 /**
297  * parman_prio_init - initializes a parman priority chunk
298  * @parman:	parman instance
299  * @prio:	parman prio structure to be initialized
300  * @priority:	desired priority of the chunk
301  *
302  * Note: all locking must be provided by the caller.
303  *
304  * Before caller could add an item with certain priority, he has to
305  * initialize a priority chunk for it using this function.
306  */
parman_prio_init(struct parman * parman,struct parman_prio * prio,unsigned long priority)307 void parman_prio_init(struct parman *parman, struct parman_prio *prio,
308 		      unsigned long priority)
309 {
310 	struct parman_prio *prio2;
311 	struct list_head *pos;
312 
313 	INIT_LIST_HEAD(&prio->item_list);
314 	prio->priority = priority;
315 
316 	/* Position inside the list according to priority */
317 	list_for_each(pos, &parman->prio_list) {
318 		prio2 = list_entry(pos, typeof(*prio2), list);
319 		if (prio2->priority > prio->priority)
320 			break;
321 	}
322 	list_add_tail(&prio->list, pos);
323 }
324 EXPORT_SYMBOL(parman_prio_init);
325 
326 /**
327  * parman_prio_fini - finalizes use of parman priority chunk
328  * @prio:	parman prio structure
329  *
330  * Note: all locking must be provided by the caller.
331  */
parman_prio_fini(struct parman_prio * prio)332 void parman_prio_fini(struct parman_prio *prio)
333 {
334 	WARN_ON(parman_prio_used(prio));
335 	list_del(&prio->list);
336 }
337 EXPORT_SYMBOL(parman_prio_fini);
338 
339 /**
340  * parman_item_add - adds a parman item under defined priority
341  * @parman:	parman instance
342  * @prio:	parman prio instance to add the item to
343  * @item:	parman item instance
344  *
345  * Note: all locking must be provided by the caller.
346  *
347  * Adds item to a array managed by parman instance under the specified priority.
348  *
349  * Returns 0 in case of success, negative number to indicate an error.
350  */
parman_item_add(struct parman * parman,struct parman_prio * prio,struct parman_item * item)351 int parman_item_add(struct parman *parman, struct parman_prio *prio,
352 		    struct parman_item *item)
353 {
354 	return parman->algo->item_add(parman, prio, item);
355 }
356 EXPORT_SYMBOL(parman_item_add);
357 
358 /**
359  * parman_item_remove - deletes parman item
360  * @parman:	parman instance
361  * @prio:	parman prio instance to delete the item from
362  * @item:	parman item instance
363  *
364  * Note: all locking must be provided by the caller.
365  */
parman_item_remove(struct parman * parman,struct parman_prio * prio,struct parman_item * item)366 void parman_item_remove(struct parman *parman, struct parman_prio *prio,
367 			struct parman_item *item)
368 {
369 	parman->algo->item_remove(parman, prio, item);
370 }
371 EXPORT_SYMBOL(parman_item_remove);
372 
373 MODULE_LICENSE("Dual BSD/GPL");
374 MODULE_AUTHOR("Jiri Pirko <jiri@mellanox.com>");
375 MODULE_DESCRIPTION("Priority-based array manager");
376