1 /* 2 * Tag allocation using scalable bitmaps. Uses active queue tracking to support 3 * fairer distribution of tags between multiple submitters when a shared tag map 4 * is used. 5 * 6 * Copyright (C) 2013-2014 Jens Axboe 7 */ 8 #include <linux/kernel.h> 9 #include <linux/module.h> 10 11 #include <linux/blk-mq.h> 12 #include "blk.h" 13 #include "blk-mq.h" 14 #include "blk-mq-tag.h" 15 16 bool blk_mq_has_free_tags(struct blk_mq_tags *tags) 17 { 18 if (!tags) 19 return true; 20 21 return sbitmap_any_bit_clear(&tags->bitmap_tags.sb); 22 } 23 24 /* 25 * If a previously inactive queue goes active, bump the active user count. 26 */ 27 bool __blk_mq_tag_busy(struct blk_mq_hw_ctx *hctx) 28 { 29 if (!test_bit(BLK_MQ_S_TAG_ACTIVE, &hctx->state) && 30 !test_and_set_bit(BLK_MQ_S_TAG_ACTIVE, &hctx->state)) 31 atomic_inc(&hctx->tags->active_queues); 32 33 return true; 34 } 35 36 /* 37 * Wakeup all potentially sleeping on tags 38 */ 39 void blk_mq_tag_wakeup_all(struct blk_mq_tags *tags, bool include_reserve) 40 { 41 sbitmap_queue_wake_all(&tags->bitmap_tags); 42 if (include_reserve) 43 sbitmap_queue_wake_all(&tags->breserved_tags); 44 } 45 46 /* 47 * If a previously busy queue goes inactive, potential waiters could now 48 * be allowed to queue. Wake them up and check. 49 */ 50 void __blk_mq_tag_idle(struct blk_mq_hw_ctx *hctx) 51 { 52 struct blk_mq_tags *tags = hctx->tags; 53 54 if (!test_and_clear_bit(BLK_MQ_S_TAG_ACTIVE, &hctx->state)) 55 return; 56 57 atomic_dec(&tags->active_queues); 58 59 blk_mq_tag_wakeup_all(tags, false); 60 } 61 62 /* 63 * For shared tag users, we track the number of currently active users 64 * and attempt to provide a fair share of the tag depth for each of them. 65 */ 66 static inline bool hctx_may_queue(struct blk_mq_hw_ctx *hctx, 67 struct sbitmap_queue *bt) 68 { 69 unsigned int depth, users; 70 71 if (!hctx || !(hctx->flags & BLK_MQ_F_TAG_SHARED)) 72 return true; 73 if (!test_bit(BLK_MQ_S_TAG_ACTIVE, &hctx->state)) 74 return true; 75 76 /* 77 * Don't try dividing an ant 78 */ 79 if (bt->sb.depth == 1) 80 return true; 81 82 users = atomic_read(&hctx->tags->active_queues); 83 if (!users) 84 return true; 85 86 /* 87 * Allow at least some tags 88 */ 89 depth = max((bt->sb.depth + users - 1) / users, 4U); 90 return atomic_read(&hctx->nr_active) < depth; 91 } 92 93 static int __blk_mq_get_tag(struct blk_mq_alloc_data *data, 94 struct sbitmap_queue *bt) 95 { 96 if (!(data->flags & BLK_MQ_REQ_INTERNAL) && 97 !hctx_may_queue(data->hctx, bt)) 98 return -1; 99 return __sbitmap_queue_get(bt); 100 } 101 102 unsigned int blk_mq_get_tag(struct blk_mq_alloc_data *data) 103 { 104 struct blk_mq_tags *tags = blk_mq_tags_from_data(data); 105 struct sbitmap_queue *bt; 106 struct sbq_wait_state *ws; 107 DEFINE_WAIT(wait); 108 unsigned int tag_offset; 109 bool drop_ctx; 110 int tag; 111 112 if (data->flags & BLK_MQ_REQ_RESERVED) { 113 if (unlikely(!tags->nr_reserved_tags)) { 114 WARN_ON_ONCE(1); 115 return BLK_MQ_TAG_FAIL; 116 } 117 bt = &tags->breserved_tags; 118 tag_offset = 0; 119 } else { 120 bt = &tags->bitmap_tags; 121 tag_offset = tags->nr_reserved_tags; 122 } 123 124 tag = __blk_mq_get_tag(data, bt); 125 if (tag != -1) 126 goto found_tag; 127 128 if (data->flags & BLK_MQ_REQ_NOWAIT) 129 return BLK_MQ_TAG_FAIL; 130 131 ws = bt_wait_ptr(bt, data->hctx); 132 drop_ctx = data->ctx == NULL; 133 do { 134 prepare_to_wait(&ws->wait, &wait, TASK_UNINTERRUPTIBLE); 135 136 tag = __blk_mq_get_tag(data, bt); 137 if (tag != -1) 138 break; 139 140 /* 141 * We're out of tags on this hardware queue, kick any 142 * pending IO submits before going to sleep waiting for 143 * some to complete. 144 */ 145 blk_mq_run_hw_queue(data->hctx, false); 146 147 /* 148 * Retry tag allocation after running the hardware queue, 149 * as running the queue may also have found completions. 150 */ 151 tag = __blk_mq_get_tag(data, bt); 152 if (tag != -1) 153 break; 154 155 if (data->ctx) 156 blk_mq_put_ctx(data->ctx); 157 158 io_schedule(); 159 160 data->ctx = blk_mq_get_ctx(data->q); 161 data->hctx = blk_mq_map_queue(data->q, data->ctx->cpu); 162 tags = blk_mq_tags_from_data(data); 163 if (data->flags & BLK_MQ_REQ_RESERVED) 164 bt = &tags->breserved_tags; 165 else 166 bt = &tags->bitmap_tags; 167 168 finish_wait(&ws->wait, &wait); 169 ws = bt_wait_ptr(bt, data->hctx); 170 } while (1); 171 172 if (drop_ctx && data->ctx) 173 blk_mq_put_ctx(data->ctx); 174 175 finish_wait(&ws->wait, &wait); 176 177 found_tag: 178 return tag + tag_offset; 179 } 180 181 void blk_mq_put_tag(struct blk_mq_hw_ctx *hctx, struct blk_mq_tags *tags, 182 struct blk_mq_ctx *ctx, unsigned int tag) 183 { 184 if (!blk_mq_tag_is_reserved(tags, tag)) { 185 const int real_tag = tag - tags->nr_reserved_tags; 186 187 BUG_ON(real_tag >= tags->nr_tags); 188 sbitmap_queue_clear(&tags->bitmap_tags, real_tag, ctx->cpu); 189 } else { 190 BUG_ON(tag >= tags->nr_reserved_tags); 191 sbitmap_queue_clear(&tags->breserved_tags, tag, ctx->cpu); 192 } 193 } 194 195 struct bt_iter_data { 196 struct blk_mq_hw_ctx *hctx; 197 busy_iter_fn *fn; 198 void *data; 199 bool reserved; 200 }; 201 202 static bool bt_iter(struct sbitmap *bitmap, unsigned int bitnr, void *data) 203 { 204 struct bt_iter_data *iter_data = data; 205 struct blk_mq_hw_ctx *hctx = iter_data->hctx; 206 struct blk_mq_tags *tags = hctx->tags; 207 bool reserved = iter_data->reserved; 208 struct request *rq; 209 210 if (!reserved) 211 bitnr += tags->nr_reserved_tags; 212 rq = tags->rqs[bitnr]; 213 214 if (rq->q == hctx->queue) 215 iter_data->fn(hctx, rq, iter_data->data, reserved); 216 return true; 217 } 218 219 static void bt_for_each(struct blk_mq_hw_ctx *hctx, struct sbitmap_queue *bt, 220 busy_iter_fn *fn, void *data, bool reserved) 221 { 222 struct bt_iter_data iter_data = { 223 .hctx = hctx, 224 .fn = fn, 225 .data = data, 226 .reserved = reserved, 227 }; 228 229 sbitmap_for_each_set(&bt->sb, bt_iter, &iter_data); 230 } 231 232 struct bt_tags_iter_data { 233 struct blk_mq_tags *tags; 234 busy_tag_iter_fn *fn; 235 void *data; 236 bool reserved; 237 }; 238 239 static bool bt_tags_iter(struct sbitmap *bitmap, unsigned int bitnr, void *data) 240 { 241 struct bt_tags_iter_data *iter_data = data; 242 struct blk_mq_tags *tags = iter_data->tags; 243 bool reserved = iter_data->reserved; 244 struct request *rq; 245 246 if (!reserved) 247 bitnr += tags->nr_reserved_tags; 248 rq = tags->rqs[bitnr]; 249 250 iter_data->fn(rq, iter_data->data, reserved); 251 return true; 252 } 253 254 static void bt_tags_for_each(struct blk_mq_tags *tags, struct sbitmap_queue *bt, 255 busy_tag_iter_fn *fn, void *data, bool reserved) 256 { 257 struct bt_tags_iter_data iter_data = { 258 .tags = tags, 259 .fn = fn, 260 .data = data, 261 .reserved = reserved, 262 }; 263 264 if (tags->rqs) 265 sbitmap_for_each_set(&bt->sb, bt_tags_iter, &iter_data); 266 } 267 268 static void blk_mq_all_tag_busy_iter(struct blk_mq_tags *tags, 269 busy_tag_iter_fn *fn, void *priv) 270 { 271 if (tags->nr_reserved_tags) 272 bt_tags_for_each(tags, &tags->breserved_tags, fn, priv, true); 273 bt_tags_for_each(tags, &tags->bitmap_tags, fn, priv, false); 274 } 275 276 void blk_mq_tagset_busy_iter(struct blk_mq_tag_set *tagset, 277 busy_tag_iter_fn *fn, void *priv) 278 { 279 int i; 280 281 for (i = 0; i < tagset->nr_hw_queues; i++) { 282 if (tagset->tags && tagset->tags[i]) 283 blk_mq_all_tag_busy_iter(tagset->tags[i], fn, priv); 284 } 285 } 286 EXPORT_SYMBOL(blk_mq_tagset_busy_iter); 287 288 int blk_mq_reinit_tagset(struct blk_mq_tag_set *set) 289 { 290 int i, j, ret = 0; 291 292 if (!set->ops->reinit_request) 293 goto out; 294 295 for (i = 0; i < set->nr_hw_queues; i++) { 296 struct blk_mq_tags *tags = set->tags[i]; 297 298 if (!tags) 299 continue; 300 301 for (j = 0; j < tags->nr_tags; j++) { 302 if (!tags->static_rqs[j]) 303 continue; 304 305 ret = set->ops->reinit_request(set->driver_data, 306 tags->static_rqs[j]); 307 if (ret) 308 goto out; 309 } 310 } 311 312 out: 313 return ret; 314 } 315 EXPORT_SYMBOL_GPL(blk_mq_reinit_tagset); 316 317 void blk_mq_queue_tag_busy_iter(struct request_queue *q, busy_iter_fn *fn, 318 void *priv) 319 { 320 struct blk_mq_hw_ctx *hctx; 321 int i; 322 323 324 queue_for_each_hw_ctx(q, hctx, i) { 325 struct blk_mq_tags *tags = hctx->tags; 326 327 /* 328 * If not software queues are currently mapped to this 329 * hardware queue, there's nothing to check 330 */ 331 if (!blk_mq_hw_queue_mapped(hctx)) 332 continue; 333 334 if (tags->nr_reserved_tags) 335 bt_for_each(hctx, &tags->breserved_tags, fn, priv, true); 336 bt_for_each(hctx, &tags->bitmap_tags, fn, priv, false); 337 } 338 339 } 340 341 static int bt_alloc(struct sbitmap_queue *bt, unsigned int depth, 342 bool round_robin, int node) 343 { 344 return sbitmap_queue_init_node(bt, depth, -1, round_robin, GFP_KERNEL, 345 node); 346 } 347 348 static struct blk_mq_tags *blk_mq_init_bitmap_tags(struct blk_mq_tags *tags, 349 int node, int alloc_policy) 350 { 351 unsigned int depth = tags->nr_tags - tags->nr_reserved_tags; 352 bool round_robin = alloc_policy == BLK_TAG_ALLOC_RR; 353 354 if (bt_alloc(&tags->bitmap_tags, depth, round_robin, node)) 355 goto free_tags; 356 if (bt_alloc(&tags->breserved_tags, tags->nr_reserved_tags, round_robin, 357 node)) 358 goto free_bitmap_tags; 359 360 return tags; 361 free_bitmap_tags: 362 sbitmap_queue_free(&tags->bitmap_tags); 363 free_tags: 364 kfree(tags); 365 return NULL; 366 } 367 368 struct blk_mq_tags *blk_mq_init_tags(unsigned int total_tags, 369 unsigned int reserved_tags, 370 int node, int alloc_policy) 371 { 372 struct blk_mq_tags *tags; 373 374 if (total_tags > BLK_MQ_TAG_MAX) { 375 pr_err("blk-mq: tag depth too large\n"); 376 return NULL; 377 } 378 379 tags = kzalloc_node(sizeof(*tags), GFP_KERNEL, node); 380 if (!tags) 381 return NULL; 382 383 tags->nr_tags = total_tags; 384 tags->nr_reserved_tags = reserved_tags; 385 386 return blk_mq_init_bitmap_tags(tags, node, alloc_policy); 387 } 388 389 void blk_mq_free_tags(struct blk_mq_tags *tags) 390 { 391 sbitmap_queue_free(&tags->bitmap_tags); 392 sbitmap_queue_free(&tags->breserved_tags); 393 kfree(tags); 394 } 395 396 int blk_mq_tag_update_depth(struct blk_mq_hw_ctx *hctx, 397 struct blk_mq_tags **tagsptr, unsigned int tdepth, 398 bool can_grow) 399 { 400 struct blk_mq_tags *tags = *tagsptr; 401 402 if (tdepth <= tags->nr_reserved_tags) 403 return -EINVAL; 404 405 tdepth -= tags->nr_reserved_tags; 406 407 /* 408 * If we are allowed to grow beyond the original size, allocate 409 * a new set of tags before freeing the old one. 410 */ 411 if (tdepth > tags->nr_tags) { 412 struct blk_mq_tag_set *set = hctx->queue->tag_set; 413 struct blk_mq_tags *new; 414 bool ret; 415 416 if (!can_grow) 417 return -EINVAL; 418 419 /* 420 * We need some sort of upper limit, set it high enough that 421 * no valid use cases should require more. 422 */ 423 if (tdepth > 16 * BLKDEV_MAX_RQ) 424 return -EINVAL; 425 426 new = blk_mq_alloc_rq_map(set, hctx->queue_num, tdepth, 0); 427 if (!new) 428 return -ENOMEM; 429 ret = blk_mq_alloc_rqs(set, new, hctx->queue_num, tdepth); 430 if (ret) { 431 blk_mq_free_rq_map(new); 432 return -ENOMEM; 433 } 434 435 blk_mq_free_rqs(set, *tagsptr, hctx->queue_num); 436 blk_mq_free_rq_map(*tagsptr); 437 *tagsptr = new; 438 } else { 439 /* 440 * Don't need (or can't) update reserved tags here, they 441 * remain static and should never need resizing. 442 */ 443 sbitmap_queue_resize(&tags->bitmap_tags, tdepth); 444 } 445 446 return 0; 447 } 448 449 /** 450 * blk_mq_unique_tag() - return a tag that is unique queue-wide 451 * @rq: request for which to compute a unique tag 452 * 453 * The tag field in struct request is unique per hardware queue but not over 454 * all hardware queues. Hence this function that returns a tag with the 455 * hardware context index in the upper bits and the per hardware queue tag in 456 * the lower bits. 457 * 458 * Note: When called for a request that is queued on a non-multiqueue request 459 * queue, the hardware context index is set to zero. 460 */ 461 u32 blk_mq_unique_tag(struct request *rq) 462 { 463 struct request_queue *q = rq->q; 464 struct blk_mq_hw_ctx *hctx; 465 int hwq = 0; 466 467 if (q->mq_ops) { 468 hctx = blk_mq_map_queue(q, rq->mq_ctx->cpu); 469 hwq = hctx->queue_num; 470 } 471 472 return (hwq << BLK_MQ_UNIQUE_TAG_BITS) | 473 (rq->tag & BLK_MQ_UNIQUE_TAG_MASK); 474 } 475 EXPORT_SYMBOL(blk_mq_unique_tag); 476