Jens Axboe | 8324aa9 | 2008-01-29 14:51:59 +0100 | [diff] [blame] | 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 | |
| 9 | /** |
| 10 | * blk_queue_find_tag - find a request by its tag and queue |
| 11 | * @q: The request queue for the device |
| 12 | * @tag: The tag of the request |
| 13 | * |
| 14 | * Notes: |
| 15 | * Should be used when a device returns a tag and you want to match |
| 16 | * it with a request. |
| 17 | * |
| 18 | * no locks need be held. |
| 19 | **/ |
| 20 | struct request *blk_queue_find_tag(struct request_queue *q, int tag) |
| 21 | { |
| 22 | return blk_map_queue_find_tag(q->queue_tags, tag); |
| 23 | } |
| 24 | |
| 25 | EXPORT_SYMBOL(blk_queue_find_tag); |
| 26 | |
| 27 | /** |
| 28 | * __blk_free_tags - release a given set of tag maintenance info |
| 29 | * @bqt: the tag map to free |
| 30 | * |
| 31 | * Tries to free the specified @bqt@. Returns true if it was |
| 32 | * actually freed and false if there are still references using it |
| 33 | */ |
| 34 | static int __blk_free_tags(struct blk_queue_tag *bqt) |
| 35 | { |
| 36 | int retval; |
| 37 | |
| 38 | retval = atomic_dec_and_test(&bqt->refcnt); |
| 39 | if (retval) { |
| 40 | BUG_ON(bqt->busy); |
| 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 | |
| 51 | return retval; |
| 52 | } |
| 53 | |
| 54 | /** |
| 55 | * __blk_queue_free_tags - release tag maintenance info |
| 56 | * @q: the request queue for the device |
| 57 | * |
| 58 | * Notes: |
| 59 | * blk_cleanup_queue() will take care of calling this function, if tagging |
| 60 | * has been used. So there's no need to call this directly. |
| 61 | **/ |
| 62 | void __blk_queue_free_tags(struct request_queue *q) |
| 63 | { |
| 64 | struct blk_queue_tag *bqt = q->queue_tags; |
| 65 | |
| 66 | if (!bqt) |
| 67 | return; |
| 68 | |
| 69 | __blk_free_tags(bqt); |
| 70 | |
| 71 | q->queue_tags = NULL; |
| 72 | q->queue_flags &= ~(1 << QUEUE_FLAG_QUEUED); |
| 73 | } |
| 74 | |
| 75 | /** |
| 76 | * blk_free_tags - release a given set of tag maintenance info |
| 77 | * @bqt: the tag map to free |
| 78 | * |
| 79 | * For externally managed @bqt@ frees the map. Callers of this |
| 80 | * function must guarantee to have released all the queues that |
| 81 | * might have been using this tag map. |
| 82 | */ |
| 83 | void blk_free_tags(struct blk_queue_tag *bqt) |
| 84 | { |
| 85 | if (unlikely(!__blk_free_tags(bqt))) |
| 86 | BUG(); |
| 87 | } |
| 88 | EXPORT_SYMBOL(blk_free_tags); |
| 89 | |
| 90 | /** |
| 91 | * blk_queue_free_tags - release tag maintenance info |
| 92 | * @q: the request queue for the device |
| 93 | * |
| 94 | * Notes: |
| 95 | * This is used to disabled tagged queuing to a device, yet leave |
| 96 | * queue in function. |
| 97 | **/ |
| 98 | void blk_queue_free_tags(struct request_queue *q) |
| 99 | { |
| 100 | clear_bit(QUEUE_FLAG_QUEUED, &q->queue_flags); |
| 101 | } |
| 102 | |
| 103 | EXPORT_SYMBOL(blk_queue_free_tags); |
| 104 | |
| 105 | static int |
| 106 | init_tag_map(struct request_queue *q, struct blk_queue_tag *tags, int depth) |
| 107 | { |
| 108 | struct request **tag_index; |
| 109 | unsigned long *tag_map; |
| 110 | int nr_ulongs; |
| 111 | |
| 112 | if (q && depth > q->nr_requests * 2) { |
| 113 | depth = q->nr_requests * 2; |
| 114 | printk(KERN_ERR "%s: adjusted depth to %d\n", |
| 115 | __FUNCTION__, depth); |
| 116 | } |
| 117 | |
| 118 | tag_index = kzalloc(depth * sizeof(struct request *), GFP_ATOMIC); |
| 119 | if (!tag_index) |
| 120 | goto fail; |
| 121 | |
| 122 | nr_ulongs = ALIGN(depth, BITS_PER_LONG) / BITS_PER_LONG; |
| 123 | tag_map = kzalloc(nr_ulongs * sizeof(unsigned long), GFP_ATOMIC); |
| 124 | if (!tag_map) |
| 125 | goto fail; |
| 126 | |
| 127 | tags->real_max_depth = depth; |
| 128 | tags->max_depth = depth; |
| 129 | tags->tag_index = tag_index; |
| 130 | tags->tag_map = tag_map; |
| 131 | |
| 132 | return 0; |
| 133 | fail: |
| 134 | kfree(tag_index); |
| 135 | return -ENOMEM; |
| 136 | } |
| 137 | |
| 138 | static struct blk_queue_tag *__blk_queue_init_tags(struct request_queue *q, |
| 139 | int depth) |
| 140 | { |
| 141 | struct blk_queue_tag *tags; |
| 142 | |
| 143 | tags = kmalloc(sizeof(struct blk_queue_tag), GFP_ATOMIC); |
| 144 | if (!tags) |
| 145 | goto fail; |
| 146 | |
| 147 | if (init_tag_map(q, tags, depth)) |
| 148 | goto fail; |
| 149 | |
| 150 | tags->busy = 0; |
| 151 | atomic_set(&tags->refcnt, 1); |
| 152 | return tags; |
| 153 | fail: |
| 154 | kfree(tags); |
| 155 | return NULL; |
| 156 | } |
| 157 | |
| 158 | /** |
| 159 | * blk_init_tags - initialize the tag info for an external tag map |
| 160 | * @depth: the maximum queue depth supported |
| 161 | * @tags: the tag to use |
| 162 | **/ |
| 163 | struct blk_queue_tag *blk_init_tags(int depth) |
| 164 | { |
| 165 | return __blk_queue_init_tags(NULL, depth); |
| 166 | } |
| 167 | EXPORT_SYMBOL(blk_init_tags); |
| 168 | |
| 169 | /** |
| 170 | * blk_queue_init_tags - initialize the queue tag info |
| 171 | * @q: the request queue for the device |
| 172 | * @depth: the maximum queue depth supported |
| 173 | * @tags: the tag to use |
| 174 | **/ |
| 175 | int blk_queue_init_tags(struct request_queue *q, int depth, |
| 176 | struct blk_queue_tag *tags) |
| 177 | { |
| 178 | int rc; |
| 179 | |
| 180 | BUG_ON(tags && q->queue_tags && tags != q->queue_tags); |
| 181 | |
| 182 | if (!tags && !q->queue_tags) { |
| 183 | tags = __blk_queue_init_tags(q, depth); |
| 184 | |
| 185 | if (!tags) |
| 186 | goto fail; |
| 187 | } else if (q->queue_tags) { |
| 188 | if ((rc = blk_queue_resize_tags(q, depth))) |
| 189 | return rc; |
| 190 | set_bit(QUEUE_FLAG_QUEUED, &q->queue_flags); |
| 191 | return 0; |
| 192 | } else |
| 193 | atomic_inc(&tags->refcnt); |
| 194 | |
| 195 | /* |
| 196 | * assign it, all done |
| 197 | */ |
| 198 | q->queue_tags = tags; |
| 199 | q->queue_flags |= (1 << QUEUE_FLAG_QUEUED); |
| 200 | INIT_LIST_HEAD(&q->tag_busy_list); |
| 201 | return 0; |
| 202 | fail: |
| 203 | kfree(tags); |
| 204 | return -ENOMEM; |
| 205 | } |
| 206 | |
| 207 | EXPORT_SYMBOL(blk_queue_init_tags); |
| 208 | |
| 209 | /** |
| 210 | * blk_queue_resize_tags - change the queueing depth |
| 211 | * @q: the request queue for the device |
| 212 | * @new_depth: the new max command queueing depth |
| 213 | * |
| 214 | * Notes: |
| 215 | * Must be called with the queue lock held. |
| 216 | **/ |
| 217 | int blk_queue_resize_tags(struct request_queue *q, int new_depth) |
| 218 | { |
| 219 | struct blk_queue_tag *bqt = q->queue_tags; |
| 220 | struct request **tag_index; |
| 221 | unsigned long *tag_map; |
| 222 | int max_depth, nr_ulongs; |
| 223 | |
| 224 | if (!bqt) |
| 225 | return -ENXIO; |
| 226 | |
| 227 | /* |
| 228 | * if we already have large enough real_max_depth. just |
| 229 | * adjust max_depth. *NOTE* as requests with tag value |
| 230 | * between new_depth and real_max_depth can be in-flight, tag |
| 231 | * map can not be shrunk blindly here. |
| 232 | */ |
| 233 | if (new_depth <= bqt->real_max_depth) { |
| 234 | bqt->max_depth = new_depth; |
| 235 | return 0; |
| 236 | } |
| 237 | |
| 238 | /* |
| 239 | * Currently cannot replace a shared tag map with a new |
| 240 | * one, so error out if this is the case |
| 241 | */ |
| 242 | if (atomic_read(&bqt->refcnt) != 1) |
| 243 | return -EBUSY; |
| 244 | |
| 245 | /* |
| 246 | * save the old state info, so we can copy it back |
| 247 | */ |
| 248 | tag_index = bqt->tag_index; |
| 249 | tag_map = bqt->tag_map; |
| 250 | max_depth = bqt->real_max_depth; |
| 251 | |
| 252 | if (init_tag_map(q, bqt, new_depth)) |
| 253 | return -ENOMEM; |
| 254 | |
| 255 | memcpy(bqt->tag_index, tag_index, max_depth * sizeof(struct request *)); |
| 256 | nr_ulongs = ALIGN(max_depth, BITS_PER_LONG) / BITS_PER_LONG; |
| 257 | memcpy(bqt->tag_map, tag_map, nr_ulongs * sizeof(unsigned long)); |
| 258 | |
| 259 | kfree(tag_index); |
| 260 | kfree(tag_map); |
| 261 | return 0; |
| 262 | } |
| 263 | |
| 264 | EXPORT_SYMBOL(blk_queue_resize_tags); |
| 265 | |
| 266 | /** |
| 267 | * blk_queue_end_tag - end tag operations for a request |
| 268 | * @q: the request queue for the device |
| 269 | * @rq: the request that has completed |
| 270 | * |
| 271 | * Description: |
| 272 | * Typically called when end_that_request_first() returns 0, meaning |
| 273 | * all transfers have been done for a request. It's important to call |
| 274 | * this function before end_that_request_last(), as that will put the |
| 275 | * request back on the free list thus corrupting the internal tag list. |
| 276 | * |
| 277 | * Notes: |
| 278 | * queue lock must be held. |
| 279 | **/ |
| 280 | void blk_queue_end_tag(struct request_queue *q, struct request *rq) |
| 281 | { |
| 282 | struct blk_queue_tag *bqt = q->queue_tags; |
| 283 | int tag = rq->tag; |
| 284 | |
| 285 | BUG_ON(tag == -1); |
| 286 | |
| 287 | if (unlikely(tag >= bqt->real_max_depth)) |
| 288 | /* |
| 289 | * This can happen after tag depth has been reduced. |
| 290 | * FIXME: how about a warning or info message here? |
| 291 | */ |
| 292 | return; |
| 293 | |
| 294 | list_del_init(&rq->queuelist); |
| 295 | rq->cmd_flags &= ~REQ_QUEUED; |
| 296 | rq->tag = -1; |
| 297 | |
| 298 | if (unlikely(bqt->tag_index[tag] == NULL)) |
| 299 | printk(KERN_ERR "%s: tag %d is missing\n", |
| 300 | __FUNCTION__, tag); |
| 301 | |
| 302 | bqt->tag_index[tag] = NULL; |
| 303 | |
| 304 | if (unlikely(!test_bit(tag, bqt->tag_map))) { |
| 305 | printk(KERN_ERR "%s: attempt to clear non-busy tag (%d)\n", |
| 306 | __FUNCTION__, tag); |
| 307 | return; |
| 308 | } |
| 309 | /* |
| 310 | * The tag_map bit acts as a lock for tag_index[bit], so we need |
| 311 | * unlock memory barrier semantics. |
| 312 | */ |
| 313 | clear_bit_unlock(tag, bqt->tag_map); |
| 314 | bqt->busy--; |
| 315 | } |
| 316 | |
| 317 | EXPORT_SYMBOL(blk_queue_end_tag); |
| 318 | |
| 319 | /** |
| 320 | * blk_queue_start_tag - find a free tag and assign it |
| 321 | * @q: the request queue for the device |
| 322 | * @rq: the block request that needs tagging |
| 323 | * |
| 324 | * Description: |
| 325 | * This can either be used as a stand-alone helper, or possibly be |
| 326 | * assigned as the queue &prep_rq_fn (in which case &struct request |
| 327 | * automagically gets a tag assigned). Note that this function |
| 328 | * assumes that any type of request can be queued! if this is not |
| 329 | * true for your device, you must check the request type before |
| 330 | * calling this function. The request will also be removed from |
| 331 | * the request queue, so it's the drivers responsibility to readd |
| 332 | * it if it should need to be restarted for some reason. |
| 333 | * |
| 334 | * Notes: |
| 335 | * queue lock must be held. |
| 336 | **/ |
| 337 | int blk_queue_start_tag(struct request_queue *q, struct request *rq) |
| 338 | { |
| 339 | struct blk_queue_tag *bqt = q->queue_tags; |
| 340 | int tag; |
| 341 | |
| 342 | if (unlikely((rq->cmd_flags & REQ_QUEUED))) { |
| 343 | printk(KERN_ERR |
| 344 | "%s: request %p for device [%s] already tagged %d", |
| 345 | __FUNCTION__, rq, |
| 346 | rq->rq_disk ? rq->rq_disk->disk_name : "?", rq->tag); |
| 347 | BUG(); |
| 348 | } |
| 349 | |
| 350 | /* |
| 351 | * Protect against shared tag maps, as we may not have exclusive |
| 352 | * access to the tag map. |
| 353 | */ |
| 354 | do { |
| 355 | tag = find_first_zero_bit(bqt->tag_map, bqt->max_depth); |
| 356 | if (tag >= bqt->max_depth) |
| 357 | return 1; |
| 358 | |
| 359 | } while (test_and_set_bit_lock(tag, bqt->tag_map)); |
| 360 | /* |
| 361 | * We need lock ordering semantics given by test_and_set_bit_lock. |
| 362 | * See blk_queue_end_tag for details. |
| 363 | */ |
| 364 | |
| 365 | rq->cmd_flags |= REQ_QUEUED; |
| 366 | rq->tag = tag; |
| 367 | bqt->tag_index[tag] = rq; |
| 368 | blkdev_dequeue_request(rq); |
| 369 | list_add(&rq->queuelist, &q->tag_busy_list); |
| 370 | bqt->busy++; |
| 371 | return 0; |
| 372 | } |
| 373 | |
| 374 | EXPORT_SYMBOL(blk_queue_start_tag); |
| 375 | |
| 376 | /** |
| 377 | * blk_queue_invalidate_tags - invalidate all pending tags |
| 378 | * @q: the request queue for the device |
| 379 | * |
| 380 | * Description: |
| 381 | * Hardware conditions may dictate a need to stop all pending requests. |
| 382 | * In this case, we will safely clear the block side of the tag queue and |
| 383 | * readd all requests to the request queue in the right order. |
| 384 | * |
| 385 | * Notes: |
| 386 | * queue lock must be held. |
| 387 | **/ |
| 388 | void blk_queue_invalidate_tags(struct request_queue *q) |
| 389 | { |
| 390 | struct list_head *tmp, *n; |
| 391 | |
| 392 | list_for_each_safe(tmp, n, &q->tag_busy_list) |
| 393 | blk_requeue_request(q, list_entry_rq(tmp)); |
| 394 | } |
| 395 | |
| 396 | EXPORT_SYMBOL(blk_queue_invalidate_tags); |