Commit | Line | Data |
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320ae51f JA |
1 | #include <linux/kernel.h> |
2 | #include <linux/module.h> | |
4bb659b1 | 3 | #include <linux/random.h> |
320ae51f JA |
4 | |
5 | #include <linux/blk-mq.h> | |
6 | #include "blk.h" | |
7 | #include "blk-mq.h" | |
8 | #include "blk-mq-tag.h" | |
9 | ||
4bb659b1 JA |
10 | void blk_mq_wait_for_tags(struct blk_mq_tags *tags, struct blk_mq_hw_ctx *hctx, |
11 | bool reserved) | |
320ae51f | 12 | { |
4bb659b1 JA |
13 | int tag, zero = 0; |
14 | ||
15 | tag = blk_mq_get_tag(tags, hctx, &zero, __GFP_WAIT, reserved); | |
16 | blk_mq_put_tag(tags, tag, &zero); | |
17 | } | |
18 | ||
19 | static bool bt_has_free_tags(struct blk_mq_bitmap_tags *bt) | |
20 | { | |
21 | int i; | |
22 | ||
23 | for (i = 0; i < bt->map_nr; i++) { | |
e93ecf60 | 24 | struct blk_align_bitmap *bm = &bt->map[i]; |
4bb659b1 JA |
25 | int ret; |
26 | ||
27 | ret = find_first_zero_bit(&bm->word, bm->depth); | |
28 | if (ret < bm->depth) | |
29 | return true; | |
30 | } | |
31 | ||
32 | return false; | |
320ae51f JA |
33 | } |
34 | ||
35 | bool blk_mq_has_free_tags(struct blk_mq_tags *tags) | |
36 | { | |
4bb659b1 JA |
37 | if (!tags) |
38 | return true; | |
39 | ||
40 | return bt_has_free_tags(&tags->bitmap_tags); | |
41 | } | |
42 | ||
e93ecf60 | 43 | static int __bt_get_word(struct blk_align_bitmap *bm, unsigned int last_tag) |
4bb659b1 JA |
44 | { |
45 | int tag, org_last_tag, end; | |
46 | ||
59d13bf5 | 47 | org_last_tag = last_tag; |
4bb659b1 JA |
48 | end = bm->depth; |
49 | do { | |
50 | restart: | |
51 | tag = find_next_zero_bit(&bm->word, end, last_tag); | |
52 | if (unlikely(tag >= end)) { | |
53 | /* | |
54 | * We started with an offset, start from 0 to | |
55 | * exhaust the map. | |
56 | */ | |
57 | if (org_last_tag && last_tag) { | |
58 | end = last_tag; | |
59 | last_tag = 0; | |
60 | goto restart; | |
61 | } | |
62 | return -1; | |
63 | } | |
64 | last_tag = tag + 1; | |
65 | } while (test_and_set_bit_lock(tag, &bm->word)); | |
66 | ||
67 | return tag; | |
68 | } | |
69 | ||
70 | /* | |
71 | * Straight forward bitmap tag implementation, where each bit is a tag | |
72 | * (cleared == free, and set == busy). The small twist is using per-cpu | |
73 | * last_tag caches, which blk-mq stores in the blk_mq_ctx software queue | |
74 | * contexts. This enables us to drastically limit the space searched, | |
75 | * without dirtying an extra shared cacheline like we would if we stored | |
76 | * the cache value inside the shared blk_mq_bitmap_tags structure. On top | |
77 | * of that, each word of tags is in a separate cacheline. This means that | |
78 | * multiple users will tend to stick to different cachelines, at least | |
79 | * until the map is exhausted. | |
80 | */ | |
81 | static int __bt_get(struct blk_mq_bitmap_tags *bt, unsigned int *tag_cache) | |
82 | { | |
83 | unsigned int last_tag, org_last_tag; | |
84 | int index, i, tag; | |
85 | ||
86 | last_tag = org_last_tag = *tag_cache; | |
59d13bf5 | 87 | index = TAG_TO_INDEX(bt, last_tag); |
4bb659b1 JA |
88 | |
89 | for (i = 0; i < bt->map_nr; i++) { | |
59d13bf5 | 90 | tag = __bt_get_word(&bt->map[index], TAG_TO_BIT(bt, last_tag)); |
4bb659b1 | 91 | if (tag != -1) { |
59d13bf5 | 92 | tag += (index << bt->bits_per_word); |
4bb659b1 JA |
93 | goto done; |
94 | } | |
95 | ||
96 | last_tag = 0; | |
97 | if (++index >= bt->map_nr) | |
98 | index = 0; | |
99 | } | |
100 | ||
101 | *tag_cache = 0; | |
102 | return -1; | |
103 | ||
104 | /* | |
105 | * Only update the cache from the allocation path, if we ended | |
106 | * up using the specific cached tag. | |
107 | */ | |
108 | done: | |
109 | if (tag == org_last_tag) { | |
110 | last_tag = tag + 1; | |
111 | if (last_tag >= bt->depth - 1) | |
112 | last_tag = 0; | |
113 | ||
114 | *tag_cache = last_tag; | |
115 | } | |
116 | ||
117 | return tag; | |
118 | } | |
119 | ||
120 | static inline void bt_index_inc(unsigned int *index) | |
121 | { | |
122 | *index = (*index + 1) & (BT_WAIT_QUEUES - 1); | |
123 | } | |
124 | ||
125 | static struct bt_wait_state *bt_wait_ptr(struct blk_mq_bitmap_tags *bt, | |
126 | struct blk_mq_hw_ctx *hctx) | |
127 | { | |
128 | struct bt_wait_state *bs; | |
129 | ||
130 | if (!hctx) | |
131 | return &bt->bs[0]; | |
132 | ||
133 | bs = &bt->bs[hctx->wait_index]; | |
134 | bt_index_inc(&hctx->wait_index); | |
135 | return bs; | |
320ae51f JA |
136 | } |
137 | ||
4bb659b1 JA |
138 | static int bt_get(struct blk_mq_bitmap_tags *bt, struct blk_mq_hw_ctx *hctx, |
139 | unsigned int *last_tag, gfp_t gfp) | |
320ae51f | 140 | { |
4bb659b1 JA |
141 | struct bt_wait_state *bs; |
142 | DEFINE_WAIT(wait); | |
320ae51f JA |
143 | int tag; |
144 | ||
4bb659b1 JA |
145 | tag = __bt_get(bt, last_tag); |
146 | if (tag != -1) | |
147 | return tag; | |
148 | ||
149 | if (!(gfp & __GFP_WAIT)) | |
150 | return -1; | |
151 | ||
152 | bs = bt_wait_ptr(bt, hctx); | |
153 | do { | |
154 | bool was_empty; | |
155 | ||
156 | was_empty = list_empty(&wait.task_list); | |
157 | prepare_to_wait(&bs->wait, &wait, TASK_UNINTERRUPTIBLE); | |
158 | ||
159 | tag = __bt_get(bt, last_tag); | |
160 | if (tag != -1) | |
161 | break; | |
162 | ||
163 | if (was_empty) | |
164 | atomic_set(&bs->wait_cnt, bt->wake_cnt); | |
165 | ||
166 | io_schedule(); | |
167 | } while (1); | |
168 | ||
169 | finish_wait(&bs->wait, &wait); | |
170 | return tag; | |
171 | } | |
172 | ||
173 | static unsigned int __blk_mq_get_tag(struct blk_mq_tags *tags, | |
174 | struct blk_mq_hw_ctx *hctx, | |
175 | unsigned int *last_tag, gfp_t gfp) | |
176 | { | |
177 | int tag; | |
178 | ||
179 | tag = bt_get(&tags->bitmap_tags, hctx, last_tag, gfp); | |
180 | if (tag >= 0) | |
181 | return tag + tags->nr_reserved_tags; | |
182 | ||
183 | return BLK_MQ_TAG_FAIL; | |
320ae51f JA |
184 | } |
185 | ||
186 | static unsigned int __blk_mq_get_reserved_tag(struct blk_mq_tags *tags, | |
187 | gfp_t gfp) | |
188 | { | |
4bb659b1 | 189 | int tag, zero = 0; |
320ae51f JA |
190 | |
191 | if (unlikely(!tags->nr_reserved_tags)) { | |
192 | WARN_ON_ONCE(1); | |
193 | return BLK_MQ_TAG_FAIL; | |
194 | } | |
195 | ||
4bb659b1 | 196 | tag = bt_get(&tags->breserved_tags, NULL, &zero, gfp); |
320ae51f JA |
197 | if (tag < 0) |
198 | return BLK_MQ_TAG_FAIL; | |
4bb659b1 | 199 | |
320ae51f JA |
200 | return tag; |
201 | } | |
202 | ||
4bb659b1 JA |
203 | unsigned int blk_mq_get_tag(struct blk_mq_tags *tags, |
204 | struct blk_mq_hw_ctx *hctx, unsigned int *last_tag, | |
205 | gfp_t gfp, bool reserved) | |
320ae51f JA |
206 | { |
207 | if (!reserved) | |
4bb659b1 | 208 | return __blk_mq_get_tag(tags, hctx, last_tag, gfp); |
320ae51f JA |
209 | |
210 | return __blk_mq_get_reserved_tag(tags, gfp); | |
211 | } | |
212 | ||
4bb659b1 JA |
213 | static struct bt_wait_state *bt_wake_ptr(struct blk_mq_bitmap_tags *bt) |
214 | { | |
215 | int i, wake_index; | |
216 | ||
217 | wake_index = bt->wake_index; | |
218 | for (i = 0; i < BT_WAIT_QUEUES; i++) { | |
219 | struct bt_wait_state *bs = &bt->bs[wake_index]; | |
220 | ||
221 | if (waitqueue_active(&bs->wait)) { | |
222 | if (wake_index != bt->wake_index) | |
223 | bt->wake_index = wake_index; | |
224 | ||
225 | return bs; | |
226 | } | |
227 | ||
228 | bt_index_inc(&wake_index); | |
229 | } | |
230 | ||
231 | return NULL; | |
232 | } | |
233 | ||
234 | static void bt_clear_tag(struct blk_mq_bitmap_tags *bt, unsigned int tag) | |
235 | { | |
59d13bf5 | 236 | const int index = TAG_TO_INDEX(bt, tag); |
4bb659b1 JA |
237 | struct bt_wait_state *bs; |
238 | ||
0289b2e1 ML |
239 | /* |
240 | * The unlock memory barrier need to order access to req in free | |
241 | * path and clearing tag bit | |
242 | */ | |
243 | clear_bit_unlock(TAG_TO_BIT(bt, tag), &bt->map[index].word); | |
4bb659b1 JA |
244 | |
245 | bs = bt_wake_ptr(bt); | |
246 | if (bs && atomic_dec_and_test(&bs->wait_cnt)) { | |
4bb659b1 JA |
247 | atomic_set(&bs->wait_cnt, bt->wake_cnt); |
248 | bt_index_inc(&bt->wake_index); | |
249 | wake_up(&bs->wait); | |
250 | } | |
251 | } | |
252 | ||
320ae51f JA |
253 | static void __blk_mq_put_tag(struct blk_mq_tags *tags, unsigned int tag) |
254 | { | |
255 | BUG_ON(tag >= tags->nr_tags); | |
256 | ||
4bb659b1 | 257 | bt_clear_tag(&tags->bitmap_tags, tag); |
320ae51f JA |
258 | } |
259 | ||
260 | static void __blk_mq_put_reserved_tag(struct blk_mq_tags *tags, | |
261 | unsigned int tag) | |
262 | { | |
263 | BUG_ON(tag >= tags->nr_reserved_tags); | |
264 | ||
4bb659b1 | 265 | bt_clear_tag(&tags->breserved_tags, tag); |
320ae51f JA |
266 | } |
267 | ||
4bb659b1 JA |
268 | void blk_mq_put_tag(struct blk_mq_tags *tags, unsigned int tag, |
269 | unsigned int *last_tag) | |
320ae51f | 270 | { |
4bb659b1 JA |
271 | if (tag >= tags->nr_reserved_tags) { |
272 | const int real_tag = tag - tags->nr_reserved_tags; | |
273 | ||
274 | __blk_mq_put_tag(tags, real_tag); | |
275 | *last_tag = real_tag; | |
276 | } else | |
320ae51f JA |
277 | __blk_mq_put_reserved_tag(tags, tag); |
278 | } | |
279 | ||
4bb659b1 JA |
280 | static void bt_for_each_free(struct blk_mq_bitmap_tags *bt, |
281 | unsigned long *free_map, unsigned int off) | |
320ae51f | 282 | { |
4bb659b1 JA |
283 | int i; |
284 | ||
285 | for (i = 0; i < bt->map_nr; i++) { | |
e93ecf60 | 286 | struct blk_align_bitmap *bm = &bt->map[i]; |
4bb659b1 JA |
287 | int bit = 0; |
288 | ||
289 | do { | |
290 | bit = find_next_zero_bit(&bm->word, bm->depth, bit); | |
291 | if (bit >= bm->depth) | |
292 | break; | |
293 | ||
294 | __set_bit(bit + off, free_map); | |
295 | bit++; | |
296 | } while (1); | |
297 | ||
59d13bf5 | 298 | off += (1 << bt->bits_per_word); |
4bb659b1 | 299 | } |
320ae51f JA |
300 | } |
301 | ||
302 | void blk_mq_tag_busy_iter(struct blk_mq_tags *tags, | |
303 | void (*fn)(void *, unsigned long *), void *data) | |
304 | { | |
305 | unsigned long *tag_map; | |
306 | size_t map_size; | |
307 | ||
308 | map_size = ALIGN(tags->nr_tags, BITS_PER_LONG) / BITS_PER_LONG; | |
309 | tag_map = kzalloc(map_size * sizeof(unsigned long), GFP_ATOMIC); | |
310 | if (!tag_map) | |
311 | return; | |
312 | ||
4bb659b1 | 313 | bt_for_each_free(&tags->bitmap_tags, tag_map, tags->nr_reserved_tags); |
320ae51f | 314 | if (tags->nr_reserved_tags) |
4bb659b1 | 315 | bt_for_each_free(&tags->breserved_tags, tag_map, 0); |
320ae51f JA |
316 | |
317 | fn(data, tag_map); | |
318 | kfree(tag_map); | |
319 | } | |
320 | ||
4bb659b1 JA |
321 | static unsigned int bt_unused_tags(struct blk_mq_bitmap_tags *bt) |
322 | { | |
323 | unsigned int i, used; | |
324 | ||
325 | for (i = 0, used = 0; i < bt->map_nr; i++) { | |
e93ecf60 | 326 | struct blk_align_bitmap *bm = &bt->map[i]; |
4bb659b1 JA |
327 | |
328 | used += bitmap_weight(&bm->word, bm->depth); | |
329 | } | |
330 | ||
331 | return bt->depth - used; | |
332 | } | |
333 | ||
334 | static int bt_alloc(struct blk_mq_bitmap_tags *bt, unsigned int depth, | |
335 | int node, bool reserved) | |
336 | { | |
337 | int i; | |
338 | ||
59d13bf5 JA |
339 | bt->bits_per_word = ilog2(BITS_PER_LONG); |
340 | ||
4bb659b1 JA |
341 | /* |
342 | * Depth can be zero for reserved tags, that's not a failure | |
343 | * condition. | |
344 | */ | |
345 | if (depth) { | |
59d13bf5 JA |
346 | unsigned int nr, i, map_depth, tags_per_word; |
347 | ||
348 | tags_per_word = (1 << bt->bits_per_word); | |
349 | ||
350 | /* | |
351 | * If the tag space is small, shrink the number of tags | |
352 | * per word so we spread over a few cachelines, at least. | |
353 | * If less than 4 tags, just forget about it, it's not | |
354 | * going to work optimally anyway. | |
355 | */ | |
356 | if (depth >= 4) { | |
357 | while (tags_per_word * 4 > depth) { | |
358 | bt->bits_per_word--; | |
359 | tags_per_word = (1 << bt->bits_per_word); | |
360 | } | |
361 | } | |
4bb659b1 | 362 | |
59d13bf5 | 363 | nr = ALIGN(depth, tags_per_word) / tags_per_word; |
e93ecf60 | 364 | bt->map = kzalloc_node(nr * sizeof(struct blk_align_bitmap), |
4bb659b1 JA |
365 | GFP_KERNEL, node); |
366 | if (!bt->map) | |
367 | return -ENOMEM; | |
368 | ||
369 | bt->map_nr = nr; | |
370 | map_depth = depth; | |
371 | for (i = 0; i < nr; i++) { | |
59d13bf5 JA |
372 | bt->map[i].depth = min(map_depth, tags_per_word); |
373 | map_depth -= tags_per_word; | |
4bb659b1 JA |
374 | } |
375 | } | |
376 | ||
377 | bt->bs = kzalloc(BT_WAIT_QUEUES * sizeof(*bt->bs), GFP_KERNEL); | |
378 | if (!bt->bs) { | |
379 | kfree(bt->map); | |
380 | return -ENOMEM; | |
381 | } | |
382 | ||
383 | for (i = 0; i < BT_WAIT_QUEUES; i++) | |
384 | init_waitqueue_head(&bt->bs[i].wait); | |
385 | ||
386 | bt->wake_cnt = BT_WAIT_BATCH; | |
387 | if (bt->wake_cnt > depth / 4) | |
388 | bt->wake_cnt = max(1U, depth / 4); | |
389 | ||
390 | bt->depth = depth; | |
391 | return 0; | |
392 | } | |
393 | ||
394 | static void bt_free(struct blk_mq_bitmap_tags *bt) | |
395 | { | |
396 | kfree(bt->map); | |
397 | kfree(bt->bs); | |
398 | } | |
399 | ||
400 | static struct blk_mq_tags *blk_mq_init_bitmap_tags(struct blk_mq_tags *tags, | |
401 | int node) | |
402 | { | |
403 | unsigned int depth = tags->nr_tags - tags->nr_reserved_tags; | |
404 | ||
405 | if (bt_alloc(&tags->bitmap_tags, depth, node, false)) | |
406 | goto enomem; | |
407 | if (bt_alloc(&tags->breserved_tags, tags->nr_reserved_tags, node, true)) | |
408 | goto enomem; | |
409 | ||
410 | return tags; | |
411 | enomem: | |
412 | bt_free(&tags->bitmap_tags); | |
413 | kfree(tags); | |
414 | return NULL; | |
415 | } | |
416 | ||
320ae51f JA |
417 | struct blk_mq_tags *blk_mq_init_tags(unsigned int total_tags, |
418 | unsigned int reserved_tags, int node) | |
419 | { | |
320ae51f | 420 | struct blk_mq_tags *tags; |
320ae51f JA |
421 | |
422 | if (total_tags > BLK_MQ_TAG_MAX) { | |
423 | pr_err("blk-mq: tag depth too large\n"); | |
424 | return NULL; | |
425 | } | |
426 | ||
427 | tags = kzalloc_node(sizeof(*tags), GFP_KERNEL, node); | |
428 | if (!tags) | |
429 | return NULL; | |
430 | ||
320ae51f JA |
431 | tags->nr_tags = total_tags; |
432 | tags->nr_reserved_tags = reserved_tags; | |
320ae51f | 433 | |
4bb659b1 | 434 | return blk_mq_init_bitmap_tags(tags, node); |
320ae51f JA |
435 | } |
436 | ||
437 | void blk_mq_free_tags(struct blk_mq_tags *tags) | |
438 | { | |
4bb659b1 JA |
439 | bt_free(&tags->bitmap_tags); |
440 | bt_free(&tags->breserved_tags); | |
320ae51f JA |
441 | kfree(tags); |
442 | } | |
443 | ||
4bb659b1 JA |
444 | void blk_mq_tag_init_last_tag(struct blk_mq_tags *tags, unsigned int *tag) |
445 | { | |
446 | unsigned int depth = tags->nr_tags - tags->nr_reserved_tags; | |
447 | ||
9d3d21ae | 448 | *tag = prandom_u32() % depth; |
4bb659b1 JA |
449 | } |
450 | ||
320ae51f JA |
451 | ssize_t blk_mq_tag_sysfs_show(struct blk_mq_tags *tags, char *page) |
452 | { | |
453 | char *orig_page = page; | |
4bb659b1 | 454 | unsigned int free, res; |
320ae51f JA |
455 | |
456 | if (!tags) | |
457 | return 0; | |
458 | ||
59d13bf5 JA |
459 | page += sprintf(page, "nr_tags=%u, reserved_tags=%u, " |
460 | "bits_per_word=%u\n", | |
461 | tags->nr_tags, tags->nr_reserved_tags, | |
462 | tags->bitmap_tags.bits_per_word); | |
320ae51f | 463 | |
4bb659b1 JA |
464 | free = bt_unused_tags(&tags->bitmap_tags); |
465 | res = bt_unused_tags(&tags->breserved_tags); | |
320ae51f | 466 | |
4bb659b1 | 467 | page += sprintf(page, "nr_free=%u, nr_reserved=%u\n", free, res); |
320ae51f JA |
468 | |
469 | return page - orig_page; | |
470 | } |