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1/*
2 * Copyright (C) 2016 Facebook
3 * Copyright (C) 2013-2014 Jens Axboe
4 *
5 * This program is free software; you can redistribute it and/or
6 * modify it under the terms of the GNU General Public
7 * License v2 as published by the Free Software Foundation.
8 *
9 * This program is distributed in the hope that it will be useful,
10 * but WITHOUT ANY WARRANTY; without even the implied warranty of
11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
12 * General Public License for more details.
13 *
14 * You should have received a copy of the GNU General Public License
15 * along with this program. If not, see <https://www.gnu.org/licenses/>.
16 */
17
18#include <linux/sched.h>
19#include <linux/random.h>
20#include <linux/sbitmap.h>
21#include <linux/seq_file.h>
22
23int sbitmap_init_node(struct sbitmap *sb, unsigned int depth, int shift,
24 gfp_t flags, int node)
25{
26 unsigned int bits_per_word;
27 unsigned int i;
28
29 if (shift < 0) {
30 shift = ilog2(BITS_PER_LONG);
31 /*
32 * If the bitmap is small, shrink the number of bits per word so
33 * we spread over a few cachelines, at least. If less than 4
34 * bits, just forget about it, it's not going to work optimally
35 * anyway.
36 */
37 if (depth >= 4) {
38 while ((4U << shift) > depth)
39 shift--;
40 }
41 }
42 bits_per_word = 1U << shift;
43 if (bits_per_word > BITS_PER_LONG)
44 return -EINVAL;
45
46 sb->shift = shift;
47 sb->depth = depth;
48 sb->map_nr = DIV_ROUND_UP(sb->depth, bits_per_word);
49
50 if (depth == 0) {
51 sb->map = NULL;
52 return 0;
53 }
54
55 sb->map = kzalloc_node(sb->map_nr * sizeof(*sb->map), flags, node);
56 if (!sb->map)
57 return -ENOMEM;
58
59 for (i = 0; i < sb->map_nr; i++) {
60 sb->map[i].depth = min(depth, bits_per_word);
61 depth -= sb->map[i].depth;
62 }
63 return 0;
64}
65EXPORT_SYMBOL_GPL(sbitmap_init_node);
66
67void sbitmap_resize(struct sbitmap *sb, unsigned int depth)
68{
69 unsigned int bits_per_word = 1U << sb->shift;
70 unsigned int i;
71
72 sb->depth = depth;
73 sb->map_nr = DIV_ROUND_UP(sb->depth, bits_per_word);
74
75 for (i = 0; i < sb->map_nr; i++) {
76 sb->map[i].depth = min(depth, bits_per_word);
77 depth -= sb->map[i].depth;
78 }
79}
80EXPORT_SYMBOL_GPL(sbitmap_resize);
81
82static int __sbitmap_get_word(unsigned long *word, unsigned long depth,
83 unsigned int hint, bool wrap)
84{
85 unsigned int orig_hint = hint;
86 int nr;
87
88 while (1) {
89 nr = find_next_zero_bit(word, depth, hint);
90 if (unlikely(nr >= depth)) {
91 /*
92 * We started with an offset, and we didn't reset the
93 * offset to 0 in a failure case, so start from 0 to
94 * exhaust the map.
95 */
96 if (orig_hint && hint && wrap) {
97 hint = orig_hint = 0;
98 continue;
99 }
100 return -1;
101 }
102
103 if (!test_and_set_bit_lock(nr, word))
104 break;
105
106 hint = nr + 1;
107 if (hint >= depth - 1)
108 hint = 0;
109 }
110
111 return nr;
112}
113
114int sbitmap_get(struct sbitmap *sb, unsigned int alloc_hint, bool round_robin)
115{
116 unsigned int i, index;
117 int nr = -1;
118
119 index = SB_NR_TO_INDEX(sb, alloc_hint);
120
121 for (i = 0; i < sb->map_nr; i++) {
122 nr = __sbitmap_get_word(&sb->map[index].word,
123 sb->map[index].depth,
124 SB_NR_TO_BIT(sb, alloc_hint),
125 !round_robin);
126 if (nr != -1) {
127 nr += index << sb->shift;
128 break;
129 }
130
131 /* Jump to next index. */
132 index++;
133 alloc_hint = index << sb->shift;
134
135 if (index >= sb->map_nr) {
136 index = 0;
137 alloc_hint = 0;
138 }
139 }
140
141 return nr;
142}
143EXPORT_SYMBOL_GPL(sbitmap_get);
144
145int sbitmap_get_shallow(struct sbitmap *sb, unsigned int alloc_hint,
146 unsigned long shallow_depth)
147{
148 unsigned int i, index;
149 int nr = -1;
150
151 index = SB_NR_TO_INDEX(sb, alloc_hint);
152
153 for (i = 0; i < sb->map_nr; i++) {
154 nr = __sbitmap_get_word(&sb->map[index].word,
155 min(sb->map[index].depth, shallow_depth),
156 SB_NR_TO_BIT(sb, alloc_hint), true);
157 if (nr != -1) {
158 nr += index << sb->shift;
159 break;
160 }
161
162 /* Jump to next index. */
163 index++;
164 alloc_hint = index << sb->shift;
165
166 if (index >= sb->map_nr) {
167 index = 0;
168 alloc_hint = 0;
169 }
170 }
171
172 return nr;
173}
174EXPORT_SYMBOL_GPL(sbitmap_get_shallow);
175
176bool sbitmap_any_bit_set(const struct sbitmap *sb)
177{
178 unsigned int i;
179
180 for (i = 0; i < sb->map_nr; i++) {
181 if (sb->map[i].word)
182 return true;
183 }
184 return false;
185}
186EXPORT_SYMBOL_GPL(sbitmap_any_bit_set);
187
188bool sbitmap_any_bit_clear(const struct sbitmap *sb)
189{
190 unsigned int i;
191
192 for (i = 0; i < sb->map_nr; i++) {
193 const struct sbitmap_word *word = &sb->map[i];
194 unsigned long ret;
195
196 ret = find_first_zero_bit(&word->word, word->depth);
197 if (ret < word->depth)
198 return true;
199 }
200 return false;
201}
202EXPORT_SYMBOL_GPL(sbitmap_any_bit_clear);
203
204unsigned int sbitmap_weight(const struct sbitmap *sb)
205{
206 unsigned int i, weight = 0;
207
208 for (i = 0; i < sb->map_nr; i++) {
209 const struct sbitmap_word *word = &sb->map[i];
210
211 weight += bitmap_weight(&word->word, word->depth);
212 }
213 return weight;
214}
215EXPORT_SYMBOL_GPL(sbitmap_weight);
216
217void sbitmap_show(struct sbitmap *sb, struct seq_file *m)
218{
219 seq_printf(m, "depth=%u\n", sb->depth);
220 seq_printf(m, "busy=%u\n", sbitmap_weight(sb));
221 seq_printf(m, "bits_per_word=%u\n", 1U << sb->shift);
222 seq_printf(m, "map_nr=%u\n", sb->map_nr);
223}
224EXPORT_SYMBOL_GPL(sbitmap_show);
225
226static inline void emit_byte(struct seq_file *m, unsigned int offset, u8 byte)
227{
228 if ((offset & 0xf) == 0) {
229 if (offset != 0)
230 seq_putc(m, '\n');
231 seq_printf(m, "%08x:", offset);
232 }
233 if ((offset & 0x1) == 0)
234 seq_putc(m, ' ');
235 seq_printf(m, "%02x", byte);
236}
237
238void sbitmap_bitmap_show(struct sbitmap *sb, struct seq_file *m)
239{
240 u8 byte = 0;
241 unsigned int byte_bits = 0;
242 unsigned int offset = 0;
243 int i;
244
245 for (i = 0; i < sb->map_nr; i++) {
246 unsigned long word = READ_ONCE(sb->map[i].word);
247 unsigned int word_bits = READ_ONCE(sb->map[i].depth);
248
249 while (word_bits > 0) {
250 unsigned int bits = min(8 - byte_bits, word_bits);
251
252 byte |= (word & (BIT(bits) - 1)) << byte_bits;
253 byte_bits += bits;
254 if (byte_bits == 8) {
255 emit_byte(m, offset, byte);
256 byte = 0;
257 byte_bits = 0;
258 offset++;
259 }
260 word >>= bits;
261 word_bits -= bits;
262 }
263 }
264 if (byte_bits) {
265 emit_byte(m, offset, byte);
266 offset++;
267 }
268 if (offset)
269 seq_putc(m, '\n');
270}
271EXPORT_SYMBOL_GPL(sbitmap_bitmap_show);
272
273static unsigned int sbq_calc_wake_batch(unsigned int depth)
274{
275 unsigned int wake_batch;
276
277 /*
278 * For each batch, we wake up one queue. We need to make sure that our
279 * batch size is small enough that the full depth of the bitmap is
280 * enough to wake up all of the queues.
281 */
282 wake_batch = SBQ_WAKE_BATCH;
283 if (wake_batch > depth / SBQ_WAIT_QUEUES)
284 wake_batch = max(1U, depth / SBQ_WAIT_QUEUES);
285
286 return wake_batch;
287}
288
289int sbitmap_queue_init_node(struct sbitmap_queue *sbq, unsigned int depth,
290 int shift, bool round_robin, gfp_t flags, int node)
291{
292 int ret;
293 int i;
294
295 ret = sbitmap_init_node(&sbq->sb, depth, shift, flags, node);
296 if (ret)
297 return ret;
298
299 sbq->alloc_hint = alloc_percpu_gfp(unsigned int, flags);
300 if (!sbq->alloc_hint) {
301 sbitmap_free(&sbq->sb);
302 return -ENOMEM;
303 }
304
305 if (depth && !round_robin) {
306 for_each_possible_cpu(i)
307 *per_cpu_ptr(sbq->alloc_hint, i) = prandom_u32() % depth;
308 }
309
310 sbq->wake_batch = sbq_calc_wake_batch(depth);
311 atomic_set(&sbq->wake_index, 0);
312
313 sbq->ws = kzalloc_node(SBQ_WAIT_QUEUES * sizeof(*sbq->ws), flags, node);
314 if (!sbq->ws) {
315 free_percpu(sbq->alloc_hint);
316 sbitmap_free(&sbq->sb);
317 return -ENOMEM;
318 }
319
320 for (i = 0; i < SBQ_WAIT_QUEUES; i++) {
321 init_waitqueue_head(&sbq->ws[i].wait);
322 atomic_set(&sbq->ws[i].wait_cnt, sbq->wake_batch);
323 }
324
325 sbq->round_robin = round_robin;
326 return 0;
327}
328EXPORT_SYMBOL_GPL(sbitmap_queue_init_node);
329
330void sbitmap_queue_resize(struct sbitmap_queue *sbq, unsigned int depth)
331{
332 unsigned int wake_batch = sbq_calc_wake_batch(depth);
333 int i;
334
335 if (sbq->wake_batch != wake_batch) {
336 WRITE_ONCE(sbq->wake_batch, wake_batch);
337 /*
338 * Pairs with the memory barrier in sbq_wake_up() to ensure that
339 * the batch size is updated before the wait counts.
340 */
341 smp_mb__before_atomic();
342 for (i = 0; i < SBQ_WAIT_QUEUES; i++)
343 atomic_set(&sbq->ws[i].wait_cnt, 1);
344 }
345 sbitmap_resize(&sbq->sb, depth);
346}
347EXPORT_SYMBOL_GPL(sbitmap_queue_resize);
348
349int __sbitmap_queue_get(struct sbitmap_queue *sbq)
350{
351 unsigned int hint, depth;
352 int nr;
353
354 hint = this_cpu_read(*sbq->alloc_hint);
355 depth = READ_ONCE(sbq->sb.depth);
356 if (unlikely(hint >= depth)) {
357 hint = depth ? prandom_u32() % depth : 0;
358 this_cpu_write(*sbq->alloc_hint, hint);
359 }
360 nr = sbitmap_get(&sbq->sb, hint, sbq->round_robin);
361
362 if (nr == -1) {
363 /* If the map is full, a hint won't do us much good. */
364 this_cpu_write(*sbq->alloc_hint, 0);
365 } else if (nr == hint || unlikely(sbq->round_robin)) {
366 /* Only update the hint if we used it. */
367 hint = nr + 1;
368 if (hint >= depth - 1)
369 hint = 0;
370 this_cpu_write(*sbq->alloc_hint, hint);
371 }
372
373 return nr;
374}
375EXPORT_SYMBOL_GPL(__sbitmap_queue_get);
376
377int __sbitmap_queue_get_shallow(struct sbitmap_queue *sbq,
378 unsigned int shallow_depth)
379{
380 unsigned int hint, depth;
381 int nr;
382
383 hint = this_cpu_read(*sbq->alloc_hint);
384 depth = READ_ONCE(sbq->sb.depth);
385 if (unlikely(hint >= depth)) {
386 hint = depth ? prandom_u32() % depth : 0;
387 this_cpu_write(*sbq->alloc_hint, hint);
388 }
389 nr = sbitmap_get_shallow(&sbq->sb, hint, shallow_depth);
390
391 if (nr == -1) {
392 /* If the map is full, a hint won't do us much good. */
393 this_cpu_write(*sbq->alloc_hint, 0);
394 } else if (nr == hint || unlikely(sbq->round_robin)) {
395 /* Only update the hint if we used it. */
396 hint = nr + 1;
397 if (hint >= depth - 1)
398 hint = 0;
399 this_cpu_write(*sbq->alloc_hint, hint);
400 }
401
402 return nr;
403}
404EXPORT_SYMBOL_GPL(__sbitmap_queue_get_shallow);
405
406static struct sbq_wait_state *sbq_wake_ptr(struct sbitmap_queue *sbq)
407{
408 int i, wake_index;
409
410 wake_index = atomic_read(&sbq->wake_index);
411 for (i = 0; i < SBQ_WAIT_QUEUES; i++) {
412 struct sbq_wait_state *ws = &sbq->ws[wake_index];
413
414 if (waitqueue_active(&ws->wait)) {
415 int o = atomic_read(&sbq->wake_index);
416
417 if (wake_index != o)
418 atomic_cmpxchg(&sbq->wake_index, o, wake_index);
419 return ws;
420 }
421
422 wake_index = sbq_index_inc(wake_index);
423 }
424
425 return NULL;
426}
427
428static void sbq_wake_up(struct sbitmap_queue *sbq)
429{
430 struct sbq_wait_state *ws;
431 unsigned int wake_batch;
432 int wait_cnt;
433
434 /*
435 * Pairs with the memory barrier in set_current_state() to ensure the
436 * proper ordering of clear_bit()/waitqueue_active() in the waker and
437 * test_and_set_bit_lock()/prepare_to_wait()/finish_wait() in the
438 * waiter. See the comment on waitqueue_active(). This is __after_atomic
439 * because we just did clear_bit_unlock() in the caller.
440 */
441 smp_mb__after_atomic();
442
443 ws = sbq_wake_ptr(sbq);
444 if (!ws)
445 return;
446
447 wait_cnt = atomic_dec_return(&ws->wait_cnt);
448 if (wait_cnt <= 0) {
449 wake_batch = READ_ONCE(sbq->wake_batch);
450 /*
451 * Pairs with the memory barrier in sbitmap_queue_resize() to
452 * ensure that we see the batch size update before the wait
453 * count is reset.
454 */
455 smp_mb__before_atomic();
456 /*
457 * If there are concurrent callers to sbq_wake_up(), the last
458 * one to decrement the wait count below zero will bump it back
459 * up. If there is a concurrent resize, the count reset will
460 * either cause the cmpxchg to fail or overwrite after the
461 * cmpxchg.
462 */
463 atomic_cmpxchg(&ws->wait_cnt, wait_cnt, wait_cnt + wake_batch);
464 sbq_index_atomic_inc(&sbq->wake_index);
465 wake_up_nr(&ws->wait, wake_batch);
466 }
467}
468
469void sbitmap_queue_clear(struct sbitmap_queue *sbq, unsigned int nr,
470 unsigned int cpu)
471{
472 sbitmap_clear_bit_unlock(&sbq->sb, nr);
473 sbq_wake_up(sbq);
474 if (likely(!sbq->round_robin && nr < sbq->sb.depth))
475 *per_cpu_ptr(sbq->alloc_hint, cpu) = nr;
476}
477EXPORT_SYMBOL_GPL(sbitmap_queue_clear);
478
479void sbitmap_queue_wake_all(struct sbitmap_queue *sbq)
480{
481 int i, wake_index;
482
483 /*
484 * Pairs with the memory barrier in set_current_state() like in
485 * sbq_wake_up().
486 */
487 smp_mb();
488 wake_index = atomic_read(&sbq->wake_index);
489 for (i = 0; i < SBQ_WAIT_QUEUES; i++) {
490 struct sbq_wait_state *ws = &sbq->ws[wake_index];
491
492 if (waitqueue_active(&ws->wait))
493 wake_up(&ws->wait);
494
495 wake_index = sbq_index_inc(wake_index);
496 }
497}
498EXPORT_SYMBOL_GPL(sbitmap_queue_wake_all);
499
500void sbitmap_queue_show(struct sbitmap_queue *sbq, struct seq_file *m)
501{
502 bool first;
503 int i;
504
505 sbitmap_show(&sbq->sb, m);
506
507 seq_puts(m, "alloc_hint={");
508 first = true;
509 for_each_possible_cpu(i) {
510 if (!first)
511 seq_puts(m, ", ");
512 first = false;
513 seq_printf(m, "%u", *per_cpu_ptr(sbq->alloc_hint, i));
514 }
515 seq_puts(m, "}\n");
516
517 seq_printf(m, "wake_batch=%u\n", sbq->wake_batch);
518 seq_printf(m, "wake_index=%d\n", atomic_read(&sbq->wake_index));
519
520 seq_puts(m, "ws={\n");
521 for (i = 0; i < SBQ_WAIT_QUEUES; i++) {
522 struct sbq_wait_state *ws = &sbq->ws[i];
523
524 seq_printf(m, "\t{.wait_cnt=%d, .wait=%s},\n",
525 atomic_read(&ws->wait_cnt),
526 waitqueue_active(&ws->wait) ? "active" : "inactive");
527 }
528 seq_puts(m, "}\n");
529
530 seq_printf(m, "round_robin=%d\n", sbq->round_robin);
531}
532EXPORT_SYMBOL_GPL(sbitmap_queue_show);