1/* 2 * Functions related to tagged command queuing 3 */ 4#include <linux/kernel.h> 5#include <linux/module.h> 6#include <linux/bio.h> 7#include <linux/blkdev.h> 8#include <linux/slab.h> 9 10#include "blk.h" 11 12/** 13 * blk_queue_find_tag - find a request by its tag and queue 14 * @q: The request queue for the device 15 * @tag: The tag of the request 16 * 17 * Notes: 18 * Should be used when a device returns a tag and you want to match 19 * it with a request. 20 * 21 * no locks need be held. 22 **/ 23struct request *blk_queue_find_tag(struct request_queue *q, int tag) 24{ 25 return blk_map_queue_find_tag(q->queue_tags, tag); 26} 27EXPORT_SYMBOL(blk_queue_find_tag); 28 29/** 30 * blk_free_tags - release a given set of tag maintenance info 31 * @bqt: the tag map to free 32 * 33 * Drop the reference count on @bqt and frees it when the last reference 34 * is dropped. 35 */ 36void blk_free_tags(struct blk_queue_tag *bqt) 37{ 38 if (atomic_dec_and_test(&bqt->refcnt)) { 39 BUG_ON(find_first_bit(bqt->tag_map, bqt->max_depth) < 40 bqt->max_depth); 41 42 kfree(bqt->tag_index); 43 bqt->tag_index = NULL; 44 45 kfree(bqt->tag_map); 46 bqt->tag_map = NULL; 47 48 kfree(bqt); 49 } 50} 51EXPORT_SYMBOL(blk_free_tags); 52 53/** 54 * __blk_queue_free_tags - release tag maintenance info 55 * @q: the request queue for the device 56 * 57 * Notes: 58 * blk_cleanup_queue() will take care of calling this function, if tagging 59 * has been used. So there's no need to call this directly. 60 **/ 61void __blk_queue_free_tags(struct request_queue *q) 62{ 63 struct blk_queue_tag *bqt = q->queue_tags; 64 65 if (!bqt) 66 return; 67 68 blk_free_tags(bqt); 69 70 q->queue_tags = NULL; 71 queue_flag_clear_unlocked(QUEUE_FLAG_QUEUED, q); 72} 73 74/** 75 * blk_queue_free_tags - release tag maintenance info 76 * @q: the request queue for the device 77 * 78 * Notes: 79 * This is used to disable tagged queuing to a device, yet leave 80 * queue in function. 81 **/ 82void blk_queue_free_tags(struct request_queue *q) 83{ 84 queue_flag_clear_unlocked(QUEUE_FLAG_QUEUED, q); 85} 86EXPORT_SYMBOL(blk_queue_free_tags); 87 88static int 89init_tag_map(struct request_queue *q, struct blk_queue_tag *tags, int depth) 90{ 91 struct request **tag_index; 92 unsigned long *tag_map; 93 int nr_ulongs; 94 95 if (q && depth > q->nr_requests * 2) { 96 depth = q->nr_requests * 2; 97 printk(KERN_ERR "%s: adjusted depth to %d\n", 98 __func__, depth); 99 } 100 101 tag_index = kzalloc(depth * sizeof(struct request *), GFP_ATOMIC); 102 if (!tag_index) 103 goto fail; 104 105 nr_ulongs = ALIGN(depth, BITS_PER_LONG) / BITS_PER_LONG; 106 tag_map = kzalloc(nr_ulongs * sizeof(unsigned long), GFP_ATOMIC); 107 if (!tag_map) 108 goto fail; 109 110 tags->real_max_depth = depth; 111 tags->max_depth = depth; 112 tags->tag_index = tag_index; 113 tags->tag_map = tag_map; 114 115 return 0; 116fail: 117 kfree(tag_index); 118 return -ENOMEM; 119} 120 121static struct blk_queue_tag *__blk_queue_init_tags(struct request_queue *q, 122 int depth, int alloc_policy) 123{ 124 struct blk_queue_tag *tags; 125 126 tags = kmalloc(sizeof(struct blk_queue_tag), GFP_ATOMIC); 127 if (!tags) 128 goto fail; 129 130 if (init_tag_map(q, tags, depth)) 131 goto fail; 132 133 atomic_set(&tags->refcnt, 1); 134 tags->alloc_policy = alloc_policy; 135 tags->next_tag = 0; 136 return tags; 137fail: 138 kfree(tags); 139 return NULL; 140} 141 142/** 143 * blk_init_tags - initialize the tag info for an external tag map 144 * @depth: the maximum queue depth supported 145 * @alloc_policy: tag allocation policy 146 **/ 147struct blk_queue_tag *blk_init_tags(int depth, int alloc_policy) 148{ 149 return __blk_queue_init_tags(NULL, depth, alloc_policy); 150} 151EXPORT_SYMBOL(blk_init_tags); 152 153/** 154 * blk_queue_init_tags - initialize the queue tag info 155 * @q: the request queue for the device 156 * @depth: the maximum queue depth supported 157 * @tags: the tag to use 158 * @alloc_policy: tag allocation policy 159 * 160 * Queue lock must be held here if the function is called to resize an 161 * existing map. 162 **/ 163int blk_queue_init_tags(struct request_queue *q, int depth, 164 struct blk_queue_tag *tags, int alloc_policy) 165{ 166 int rc; 167 168 BUG_ON(tags && q->queue_tags && tags != q->queue_tags); 169 170 if (!tags && !q->queue_tags) { 171 tags = __blk_queue_init_tags(q, depth, alloc_policy); 172 173 if (!tags) 174 return -ENOMEM; 175 176 } else if (q->queue_tags) { 177 rc = blk_queue_resize_tags(q, depth); 178 if (rc) 179 return rc; 180 queue_flag_set(QUEUE_FLAG_QUEUED, q); 181 return 0; 182 } else 183 atomic_inc(&tags->refcnt); 184 185 /* 186 * assign it, all done 187 */ 188 q->queue_tags = tags; 189 queue_flag_set_unlocked(QUEUE_FLAG_QUEUED, q); 190 INIT_LIST_HEAD(&q->tag_busy_list); 191 return 0; 192} 193EXPORT_SYMBOL(blk_queue_init_tags); 194 195/** 196 * blk_queue_resize_tags - change the queueing depth 197 * @q: the request queue for the device 198 * @new_depth: the new max command queueing depth 199 * 200 * Notes: 201 * Must be called with the queue lock held. 202 **/ 203int blk_queue_resize_tags(struct request_queue *q, int new_depth) 204{ 205 struct blk_queue_tag *bqt = q->queue_tags; 206 struct request **tag_index; 207 unsigned long *tag_map; 208 int max_depth, nr_ulongs; 209 210 if (!bqt) 211 return -ENXIO; 212 213 /* 214 * if we already have large enough real_max_depth. just 215 * adjust max_depth. *NOTE* as requests with tag value 216 * between new_depth and real_max_depth can be in-flight, tag 217 * map can not be shrunk blindly here. 218 */ 219 if (new_depth <= bqt->real_max_depth) { 220 bqt->max_depth = new_depth; 221 return 0; 222 } 223 224 /* 225 * Currently cannot replace a shared tag map with a new 226 * one, so error out if this is the case 227 */ 228 if (atomic_read(&bqt->refcnt) != 1) 229 return -EBUSY; 230 231 /* 232 * save the old state info, so we can copy it back 233 */ 234 tag_index = bqt->tag_index; 235 tag_map = bqt->tag_map; 236 max_depth = bqt->real_max_depth; 237 238 if (init_tag_map(q, bqt, new_depth)) 239 return -ENOMEM; 240 241 memcpy(bqt->tag_index, tag_index, max_depth * sizeof(struct request *)); 242 nr_ulongs = ALIGN(max_depth, BITS_PER_LONG) / BITS_PER_LONG; 243 memcpy(bqt->tag_map, tag_map, nr_ulongs * sizeof(unsigned long)); 244 245 kfree(tag_index); 246 kfree(tag_map); 247 return 0; 248} 249EXPORT_SYMBOL(blk_queue_resize_tags); 250 251/** 252 * blk_queue_end_tag - end tag operations for a request 253 * @q: the request queue for the device 254 * @rq: the request that has completed 255 * 256 * Description: 257 * Typically called when end_that_request_first() returns %0, meaning 258 * all transfers have been done for a request. It's important to call 259 * this function before end_that_request_last(), as that will put the 260 * request back on the free list thus corrupting the internal tag list. 261 * 262 * Notes: 263 * queue lock must be held. 264 **/ 265void blk_queue_end_tag(struct request_queue *q, struct request *rq) 266{ 267 struct blk_queue_tag *bqt = q->queue_tags; 268 unsigned tag = rq->tag; /* negative tags invalid */ 269 270 BUG_ON(tag >= bqt->real_max_depth); 271 272 list_del_init(&rq->queuelist); 273 rq->cmd_flags &= ~REQ_QUEUED; 274 rq->tag = -1; 275 276 if (unlikely(bqt->tag_index[tag] == NULL)) 277 printk(KERN_ERR "%s: tag %d is missing\n", 278 __func__, tag); 279 280 bqt->tag_index[tag] = NULL; 281 282 if (unlikely(!test_bit(tag, bqt->tag_map))) { 283 printk(KERN_ERR "%s: attempt to clear non-busy tag (%d)\n", 284 __func__, tag); 285 return; 286 } 287 /* 288 * The tag_map bit acts as a lock for tag_index[bit], so we need 289 * unlock memory barrier semantics. 290 */ 291 clear_bit_unlock(tag, bqt->tag_map); 292} 293EXPORT_SYMBOL(blk_queue_end_tag); 294 295/** 296 * blk_queue_start_tag - find a free tag and assign it 297 * @q: the request queue for the device 298 * @rq: the block request that needs tagging 299 * 300 * Description: 301 * This can either be used as a stand-alone helper, or possibly be 302 * assigned as the queue &prep_rq_fn (in which case &struct request 303 * automagically gets a tag assigned). Note that this function 304 * assumes that any type of request can be queued! if this is not 305 * true for your device, you must check the request type before 306 * calling this function. The request will also be removed from 307 * the request queue, so it's the drivers responsibility to readd 308 * it if it should need to be restarted for some reason. 309 * 310 * Notes: 311 * queue lock must be held. 312 **/ 313int blk_queue_start_tag(struct request_queue *q, struct request *rq) 314{ 315 struct blk_queue_tag *bqt = q->queue_tags; 316 unsigned max_depth; 317 int tag; 318 319 if (unlikely((rq->cmd_flags & REQ_QUEUED))) { 320 printk(KERN_ERR 321 "%s: request %p for device [%s] already tagged %d", 322 __func__, rq, 323 rq->rq_disk ? rq->rq_disk->disk_name : "?", rq->tag); 324 BUG(); 325 } 326 327 /* 328 * Protect against shared tag maps, as we may not have exclusive 329 * access to the tag map. 330 * 331 * We reserve a few tags just for sync IO, since we don't want 332 * to starve sync IO on behalf of flooding async IO. 333 */ 334 max_depth = bqt->max_depth; 335 if (!rq_is_sync(rq) && max_depth > 1) { 336 switch (max_depth) { 337 case 2: 338 max_depth = 1; 339 break; 340 case 3: 341 max_depth = 2; 342 break; 343 default: 344 max_depth -= 2; 345 } 346 if (q->in_flight[BLK_RW_ASYNC] > max_depth) 347 return 1; 348 } 349 350 do { 351 if (bqt->alloc_policy == BLK_TAG_ALLOC_FIFO) { 352 tag = find_first_zero_bit(bqt->tag_map, max_depth); 353 if (tag >= max_depth) 354 return 1; 355 } else { 356 int start = bqt->next_tag; 357 int size = min_t(int, bqt->max_depth, max_depth + start); 358 tag = find_next_zero_bit(bqt->tag_map, size, start); 359 if (tag >= size && start + size > bqt->max_depth) { 360 size = start + size - bqt->max_depth; 361 tag = find_first_zero_bit(bqt->tag_map, size); 362 } 363 if (tag >= size) 364 return 1; 365 } 366 367 } while (test_and_set_bit_lock(tag, bqt->tag_map)); 368 /* 369 * We need lock ordering semantics given by test_and_set_bit_lock. 370 * See blk_queue_end_tag for details. 371 */ 372 373 bqt->next_tag = (tag + 1) % bqt->max_depth; 374 rq->cmd_flags |= REQ_QUEUED; 375 rq->tag = tag; 376 bqt->tag_index[tag] = rq; 377 blk_start_request(rq); 378 list_add(&rq->queuelist, &q->tag_busy_list); 379 return 0; 380} 381EXPORT_SYMBOL(blk_queue_start_tag); 382 383/** 384 * blk_queue_invalidate_tags - invalidate all pending tags 385 * @q: the request queue for the device 386 * 387 * Description: 388 * Hardware conditions may dictate a need to stop all pending requests. 389 * In this case, we will safely clear the block side of the tag queue and 390 * readd all requests to the request queue in the right order. 391 * 392 * Notes: 393 * queue lock must be held. 394 **/ 395void blk_queue_invalidate_tags(struct request_queue *q) 396{ 397 struct list_head *tmp, *n; 398 399 list_for_each_safe(tmp, n, &q->tag_busy_list) 400 blk_requeue_request(q, list_entry_rq(tmp)); 401} 402EXPORT_SYMBOL(blk_queue_invalidate_tags); 403