1 /* 2 * Copyright (C) 1991, 1992 Linus Torvalds 3 * Copyright (C) 1994, Karl Keyte: Added support for disk statistics 4 * Elevator latency, (C) 2000 Andrea Arcangeli <andrea@suse.de> SuSE 5 * Queue request tables / lock, selectable elevator, Jens Axboe <axboe@suse.de> 6 * kernel-doc documentation started by NeilBrown <neilb@cse.unsw.edu.au> 7 * - July2000 8 * bio rewrite, highmem i/o, etc, Jens Axboe <axboe@suse.de> - may 2001 9 */ 10 11 /* 12 * This handles all read/write requests to block devices 13 */ 14 #include <linux/kernel.h> 15 #include <linux/module.h> 16 #include <linux/backing-dev.h> 17 #include <linux/bio.h> 18 #include <linux/blkdev.h> 19 #include <linux/highmem.h> 20 #include <linux/mm.h> 21 #include <linux/kernel_stat.h> 22 #include <linux/string.h> 23 #include <linux/init.h> 24 #include <linux/completion.h> 25 #include <linux/slab.h> 26 #include <linux/swap.h> 27 #include <linux/writeback.h> 28 #include <linux/task_io_accounting_ops.h> 29 #include <linux/blktrace_api.h> 30 #include <linux/fault-inject.h> 31 #include <trace/block.h> 32 33 #include "blk.h" 34 35 DEFINE_TRACE(block_plug); 36 DEFINE_TRACE(block_unplug_io); 37 DEFINE_TRACE(block_unplug_timer); 38 DEFINE_TRACE(block_getrq); 39 DEFINE_TRACE(block_sleeprq); 40 DEFINE_TRACE(block_rq_requeue); 41 DEFINE_TRACE(block_bio_backmerge); 42 DEFINE_TRACE(block_bio_frontmerge); 43 DEFINE_TRACE(block_bio_queue); 44 DEFINE_TRACE(block_rq_complete); 45 DEFINE_TRACE(block_remap); /* Also used in drivers/md/dm.c */ 46 EXPORT_TRACEPOINT_SYMBOL_GPL(block_remap); 47 48 static int __make_request(struct request_queue *q, struct bio *bio); 49 50 /* 51 * For the allocated request tables 52 */ 53 static struct kmem_cache *request_cachep; 54 55 /* 56 * For queue allocation 57 */ 58 struct kmem_cache *blk_requestq_cachep; 59 60 /* 61 * Controlling structure to kblockd 62 */ 63 static struct workqueue_struct *kblockd_workqueue; 64 65 static void drive_stat_acct(struct request *rq, int new_io) 66 { 67 struct hd_struct *part; 68 int rw = rq_data_dir(rq); 69 int cpu; 70 71 if (!blk_fs_request(rq) || !blk_do_io_stat(rq)) 72 return; 73 74 cpu = part_stat_lock(); 75 part = disk_map_sector_rcu(rq->rq_disk, rq->sector); 76 77 if (!new_io) 78 part_stat_inc(cpu, part, merges[rw]); 79 else { 80 part_round_stats(cpu, part); 81 part_inc_in_flight(part); 82 } 83 84 part_stat_unlock(); 85 } 86 87 void blk_queue_congestion_threshold(struct request_queue *q) 88 { 89 int nr; 90 91 nr = q->nr_requests - (q->nr_requests / 8) + 1; 92 if (nr > q->nr_requests) 93 nr = q->nr_requests; 94 q->nr_congestion_on = nr; 95 96 nr = q->nr_requests - (q->nr_requests / 8) - (q->nr_requests / 16) - 1; 97 if (nr < 1) 98 nr = 1; 99 q->nr_congestion_off = nr; 100 } 101 102 /** 103 * blk_get_backing_dev_info - get the address of a queue's backing_dev_info 104 * @bdev: device 105 * 106 * Locates the passed device's request queue and returns the address of its 107 * backing_dev_info 108 * 109 * Will return NULL if the request queue cannot be located. 110 */ 111 struct backing_dev_info *blk_get_backing_dev_info(struct block_device *bdev) 112 { 113 struct backing_dev_info *ret = NULL; 114 struct request_queue *q = bdev_get_queue(bdev); 115 116 if (q) 117 ret = &q->backing_dev_info; 118 return ret; 119 } 120 EXPORT_SYMBOL(blk_get_backing_dev_info); 121 122 void blk_rq_init(struct request_queue *q, struct request *rq) 123 { 124 memset(rq, 0, sizeof(*rq)); 125 126 INIT_LIST_HEAD(&rq->queuelist); 127 INIT_LIST_HEAD(&rq->timeout_list); 128 rq->cpu = -1; 129 rq->q = q; 130 rq->sector = rq->hard_sector = (sector_t) -1; 131 INIT_HLIST_NODE(&rq->hash); 132 RB_CLEAR_NODE(&rq->rb_node); 133 rq->cmd = rq->__cmd; 134 rq->cmd_len = BLK_MAX_CDB; 135 rq->tag = -1; 136 rq->ref_count = 1; 137 } 138 EXPORT_SYMBOL(blk_rq_init); 139 140 static void req_bio_endio(struct request *rq, struct bio *bio, 141 unsigned int nbytes, int error) 142 { 143 struct request_queue *q = rq->q; 144 145 if (&q->bar_rq != rq) { 146 if (error) 147 clear_bit(BIO_UPTODATE, &bio->bi_flags); 148 else if (!test_bit(BIO_UPTODATE, &bio->bi_flags)) 149 error = -EIO; 150 151 if (unlikely(nbytes > bio->bi_size)) { 152 printk(KERN_ERR "%s: want %u bytes done, %u left\n", 153 __func__, nbytes, bio->bi_size); 154 nbytes = bio->bi_size; 155 } 156 157 if (unlikely(rq->cmd_flags & REQ_QUIET)) 158 set_bit(BIO_QUIET, &bio->bi_flags); 159 160 bio->bi_size -= nbytes; 161 bio->bi_sector += (nbytes >> 9); 162 163 if (bio_integrity(bio)) 164 bio_integrity_advance(bio, nbytes); 165 166 if (bio->bi_size == 0) 167 bio_endio(bio, error); 168 } else { 169 170 /* 171 * Okay, this is the barrier request in progress, just 172 * record the error; 173 */ 174 if (error && !q->orderr) 175 q->orderr = error; 176 } 177 } 178 179 void blk_dump_rq_flags(struct request *rq, char *msg) 180 { 181 int bit; 182 183 printk(KERN_INFO "%s: dev %s: type=%x, flags=%x\n", msg, 184 rq->rq_disk ? rq->rq_disk->disk_name : "?", rq->cmd_type, 185 rq->cmd_flags); 186 187 printk(KERN_INFO " sector %llu, nr/cnr %lu/%u\n", 188 (unsigned long long)rq->sector, 189 rq->nr_sectors, 190 rq->current_nr_sectors); 191 printk(KERN_INFO " bio %p, biotail %p, buffer %p, data %p, len %u\n", 192 rq->bio, rq->biotail, 193 rq->buffer, rq->data, 194 rq->data_len); 195 196 if (blk_pc_request(rq)) { 197 printk(KERN_INFO " cdb: "); 198 for (bit = 0; bit < BLK_MAX_CDB; bit++) 199 printk("%02x ", rq->cmd[bit]); 200 printk("\n"); 201 } 202 } 203 EXPORT_SYMBOL(blk_dump_rq_flags); 204 205 /* 206 * "plug" the device if there are no outstanding requests: this will 207 * force the transfer to start only after we have put all the requests 208 * on the list. 209 * 210 * This is called with interrupts off and no requests on the queue and 211 * with the queue lock held. 212 */ 213 void blk_plug_device(struct request_queue *q) 214 { 215 WARN_ON(!irqs_disabled()); 216 217 /* 218 * don't plug a stopped queue, it must be paired with blk_start_queue() 219 * which will restart the queueing 220 */ 221 if (blk_queue_stopped(q)) 222 return; 223 224 if (!queue_flag_test_and_set(QUEUE_FLAG_PLUGGED, q)) { 225 mod_timer(&q->unplug_timer, jiffies + q->unplug_delay); 226 trace_block_plug(q); 227 } 228 } 229 EXPORT_SYMBOL(blk_plug_device); 230 231 /** 232 * blk_plug_device_unlocked - plug a device without queue lock held 233 * @q: The &struct request_queue to plug 234 * 235 * Description: 236 * Like @blk_plug_device(), but grabs the queue lock and disables 237 * interrupts. 238 **/ 239 void blk_plug_device_unlocked(struct request_queue *q) 240 { 241 unsigned long flags; 242 243 spin_lock_irqsave(q->queue_lock, flags); 244 blk_plug_device(q); 245 spin_unlock_irqrestore(q->queue_lock, flags); 246 } 247 EXPORT_SYMBOL(blk_plug_device_unlocked); 248 249 /* 250 * remove the queue from the plugged list, if present. called with 251 * queue lock held and interrupts disabled. 252 */ 253 int blk_remove_plug(struct request_queue *q) 254 { 255 WARN_ON(!irqs_disabled()); 256 257 if (!queue_flag_test_and_clear(QUEUE_FLAG_PLUGGED, q)) 258 return 0; 259 260 del_timer(&q->unplug_timer); 261 return 1; 262 } 263 EXPORT_SYMBOL(blk_remove_plug); 264 265 /* 266 * remove the plug and let it rip.. 267 */ 268 void __generic_unplug_device(struct request_queue *q) 269 { 270 if (unlikely(blk_queue_stopped(q))) 271 return; 272 if (!blk_remove_plug(q) && !blk_queue_nonrot(q)) 273 return; 274 275 q->request_fn(q); 276 } 277 278 /** 279 * generic_unplug_device - fire a request queue 280 * @q: The &struct request_queue in question 281 * 282 * Description: 283 * Linux uses plugging to build bigger requests queues before letting 284 * the device have at them. If a queue is plugged, the I/O scheduler 285 * is still adding and merging requests on the queue. Once the queue 286 * gets unplugged, the request_fn defined for the queue is invoked and 287 * transfers started. 288 **/ 289 void generic_unplug_device(struct request_queue *q) 290 { 291 if (blk_queue_plugged(q)) { 292 spin_lock_irq(q->queue_lock); 293 __generic_unplug_device(q); 294 spin_unlock_irq(q->queue_lock); 295 } 296 } 297 EXPORT_SYMBOL(generic_unplug_device); 298 299 static void blk_backing_dev_unplug(struct backing_dev_info *bdi, 300 struct page *page) 301 { 302 struct request_queue *q = bdi->unplug_io_data; 303 304 blk_unplug(q); 305 } 306 307 void blk_unplug_work(struct work_struct *work) 308 { 309 struct request_queue *q = 310 container_of(work, struct request_queue, unplug_work); 311 312 trace_block_unplug_io(q); 313 q->unplug_fn(q); 314 } 315 316 void blk_unplug_timeout(unsigned long data) 317 { 318 struct request_queue *q = (struct request_queue *)data; 319 320 trace_block_unplug_timer(q); 321 kblockd_schedule_work(q, &q->unplug_work); 322 } 323 324 void blk_unplug(struct request_queue *q) 325 { 326 /* 327 * devices don't necessarily have an ->unplug_fn defined 328 */ 329 if (q->unplug_fn) { 330 trace_block_unplug_io(q); 331 q->unplug_fn(q); 332 } 333 } 334 EXPORT_SYMBOL(blk_unplug); 335 336 static void blk_invoke_request_fn(struct request_queue *q) 337 { 338 if (unlikely(blk_queue_stopped(q))) 339 return; 340 341 /* 342 * one level of recursion is ok and is much faster than kicking 343 * the unplug handling 344 */ 345 if (!queue_flag_test_and_set(QUEUE_FLAG_REENTER, q)) { 346 q->request_fn(q); 347 queue_flag_clear(QUEUE_FLAG_REENTER, q); 348 } else { 349 queue_flag_set(QUEUE_FLAG_PLUGGED, q); 350 kblockd_schedule_work(q, &q->unplug_work); 351 } 352 } 353 354 /** 355 * blk_start_queue - restart a previously stopped queue 356 * @q: The &struct request_queue in question 357 * 358 * Description: 359 * blk_start_queue() will clear the stop flag on the queue, and call 360 * the request_fn for the queue if it was in a stopped state when 361 * entered. Also see blk_stop_queue(). Queue lock must be held. 362 **/ 363 void blk_start_queue(struct request_queue *q) 364 { 365 WARN_ON(!irqs_disabled()); 366 367 queue_flag_clear(QUEUE_FLAG_STOPPED, q); 368 blk_invoke_request_fn(q); 369 } 370 EXPORT_SYMBOL(blk_start_queue); 371 372 /** 373 * blk_stop_queue - stop a queue 374 * @q: The &struct request_queue in question 375 * 376 * Description: 377 * The Linux block layer assumes that a block driver will consume all 378 * entries on the request queue when the request_fn strategy is called. 379 * Often this will not happen, because of hardware limitations (queue 380 * depth settings). If a device driver gets a 'queue full' response, 381 * or if it simply chooses not to queue more I/O at one point, it can 382 * call this function to prevent the request_fn from being called until 383 * the driver has signalled it's ready to go again. This happens by calling 384 * blk_start_queue() to restart queue operations. Queue lock must be held. 385 **/ 386 void blk_stop_queue(struct request_queue *q) 387 { 388 blk_remove_plug(q); 389 queue_flag_set(QUEUE_FLAG_STOPPED, q); 390 } 391 EXPORT_SYMBOL(blk_stop_queue); 392 393 /** 394 * blk_sync_queue - cancel any pending callbacks on a queue 395 * @q: the queue 396 * 397 * Description: 398 * The block layer may perform asynchronous callback activity 399 * on a queue, such as calling the unplug function after a timeout. 400 * A block device may call blk_sync_queue to ensure that any 401 * such activity is cancelled, thus allowing it to release resources 402 * that the callbacks might use. The caller must already have made sure 403 * that its ->make_request_fn will not re-add plugging prior to calling 404 * this function. 405 * 406 */ 407 void blk_sync_queue(struct request_queue *q) 408 { 409 del_timer_sync(&q->unplug_timer); 410 del_timer_sync(&q->timeout); 411 cancel_work_sync(&q->unplug_work); 412 } 413 EXPORT_SYMBOL(blk_sync_queue); 414 415 /** 416 * __blk_run_queue - run a single device queue 417 * @q: The queue to run 418 * 419 * Description: 420 * See @blk_run_queue. This variant must be called with the queue lock 421 * held and interrupts disabled. 422 * 423 */ 424 void __blk_run_queue(struct request_queue *q) 425 { 426 blk_remove_plug(q); 427 428 /* 429 * Only recurse once to avoid overrunning the stack, let the unplug 430 * handling reinvoke the handler shortly if we already got there. 431 */ 432 if (!elv_queue_empty(q)) 433 blk_invoke_request_fn(q); 434 } 435 EXPORT_SYMBOL(__blk_run_queue); 436 437 /** 438 * blk_run_queue - run a single device queue 439 * @q: The queue to run 440 * 441 * Description: 442 * Invoke request handling on this queue, if it has pending work to do. 443 * May be used to restart queueing when a request has completed. Also 444 * See @blk_start_queueing. 445 * 446 */ 447 void blk_run_queue(struct request_queue *q) 448 { 449 unsigned long flags; 450 451 spin_lock_irqsave(q->queue_lock, flags); 452 __blk_run_queue(q); 453 spin_unlock_irqrestore(q->queue_lock, flags); 454 } 455 EXPORT_SYMBOL(blk_run_queue); 456 457 void blk_put_queue(struct request_queue *q) 458 { 459 kobject_put(&q->kobj); 460 } 461 462 void blk_cleanup_queue(struct request_queue *q) 463 { 464 /* 465 * We know we have process context here, so we can be a little 466 * cautious and ensure that pending block actions on this device 467 * are done before moving on. Going into this function, we should 468 * not have processes doing IO to this device. 469 */ 470 blk_sync_queue(q); 471 472 mutex_lock(&q->sysfs_lock); 473 queue_flag_set_unlocked(QUEUE_FLAG_DEAD, q); 474 mutex_unlock(&q->sysfs_lock); 475 476 if (q->elevator) 477 elevator_exit(q->elevator); 478 479 blk_put_queue(q); 480 } 481 EXPORT_SYMBOL(blk_cleanup_queue); 482 483 static int blk_init_free_list(struct request_queue *q) 484 { 485 struct request_list *rl = &q->rq; 486 487 rl->count[BLK_RW_SYNC] = rl->count[BLK_RW_ASYNC] = 0; 488 rl->starved[BLK_RW_SYNC] = rl->starved[BLK_RW_ASYNC] = 0; 489 rl->elvpriv = 0; 490 init_waitqueue_head(&rl->wait[BLK_RW_SYNC]); 491 init_waitqueue_head(&rl->wait[BLK_RW_ASYNC]); 492 493 rl->rq_pool = mempool_create_node(BLKDEV_MIN_RQ, mempool_alloc_slab, 494 mempool_free_slab, request_cachep, q->node); 495 496 if (!rl->rq_pool) 497 return -ENOMEM; 498 499 return 0; 500 } 501 502 struct request_queue *blk_alloc_queue(gfp_t gfp_mask) 503 { 504 return blk_alloc_queue_node(gfp_mask, -1); 505 } 506 EXPORT_SYMBOL(blk_alloc_queue); 507 508 struct request_queue *blk_alloc_queue_node(gfp_t gfp_mask, int node_id) 509 { 510 struct request_queue *q; 511 int err; 512 513 q = kmem_cache_alloc_node(blk_requestq_cachep, 514 gfp_mask | __GFP_ZERO, node_id); 515 if (!q) 516 return NULL; 517 518 q->backing_dev_info.unplug_io_fn = blk_backing_dev_unplug; 519 q->backing_dev_info.unplug_io_data = q; 520 err = bdi_init(&q->backing_dev_info); 521 if (err) { 522 kmem_cache_free(blk_requestq_cachep, q); 523 return NULL; 524 } 525 526 init_timer(&q->unplug_timer); 527 setup_timer(&q->timeout, blk_rq_timed_out_timer, (unsigned long) q); 528 INIT_LIST_HEAD(&q->timeout_list); 529 INIT_WORK(&q->unplug_work, blk_unplug_work); 530 531 kobject_init(&q->kobj, &blk_queue_ktype); 532 533 mutex_init(&q->sysfs_lock); 534 spin_lock_init(&q->__queue_lock); 535 536 return q; 537 } 538 EXPORT_SYMBOL(blk_alloc_queue_node); 539 540 /** 541 * blk_init_queue - prepare a request queue for use with a block device 542 * @rfn: The function to be called to process requests that have been 543 * placed on the queue. 544 * @lock: Request queue spin lock 545 * 546 * Description: 547 * If a block device wishes to use the standard request handling procedures, 548 * which sorts requests and coalesces adjacent requests, then it must 549 * call blk_init_queue(). The function @rfn will be called when there 550 * are requests on the queue that need to be processed. If the device 551 * supports plugging, then @rfn may not be called immediately when requests 552 * are available on the queue, but may be called at some time later instead. 553 * Plugged queues are generally unplugged when a buffer belonging to one 554 * of the requests on the queue is needed, or due to memory pressure. 555 * 556 * @rfn is not required, or even expected, to remove all requests off the 557 * queue, but only as many as it can handle at a time. If it does leave 558 * requests on the queue, it is responsible for arranging that the requests 559 * get dealt with eventually. 560 * 561 * The queue spin lock must be held while manipulating the requests on the 562 * request queue; this lock will be taken also from interrupt context, so irq 563 * disabling is needed for it. 564 * 565 * Function returns a pointer to the initialized request queue, or %NULL if 566 * it didn't succeed. 567 * 568 * Note: 569 * blk_init_queue() must be paired with a blk_cleanup_queue() call 570 * when the block device is deactivated (such as at module unload). 571 **/ 572 573 struct request_queue *blk_init_queue(request_fn_proc *rfn, spinlock_t *lock) 574 { 575 return blk_init_queue_node(rfn, lock, -1); 576 } 577 EXPORT_SYMBOL(blk_init_queue); 578 579 struct request_queue * 580 blk_init_queue_node(request_fn_proc *rfn, spinlock_t *lock, int node_id) 581 { 582 struct request_queue *q = blk_alloc_queue_node(GFP_KERNEL, node_id); 583 584 if (!q) 585 return NULL; 586 587 q->node = node_id; 588 if (blk_init_free_list(q)) { 589 kmem_cache_free(blk_requestq_cachep, q); 590 return NULL; 591 } 592 593 /* 594 * if caller didn't supply a lock, they get per-queue locking with 595 * our embedded lock 596 */ 597 if (!lock) 598 lock = &q->__queue_lock; 599 600 q->request_fn = rfn; 601 q->prep_rq_fn = NULL; 602 q->unplug_fn = generic_unplug_device; 603 q->queue_flags = QUEUE_FLAG_DEFAULT; 604 q->queue_lock = lock; 605 606 /* 607 * This also sets hw/phys segments, boundary and size 608 */ 609 blk_queue_make_request(q, __make_request); 610 611 q->sg_reserved_size = INT_MAX; 612 613 blk_set_cmd_filter_defaults(&q->cmd_filter); 614 615 /* 616 * all done 617 */ 618 if (!elevator_init(q, NULL)) { 619 blk_queue_congestion_threshold(q); 620 return q; 621 } 622 623 blk_put_queue(q); 624 return NULL; 625 } 626 EXPORT_SYMBOL(blk_init_queue_node); 627 628 int blk_get_queue(struct request_queue *q) 629 { 630 if (likely(!test_bit(QUEUE_FLAG_DEAD, &q->queue_flags))) { 631 kobject_get(&q->kobj); 632 return 0; 633 } 634 635 return 1; 636 } 637 638 static inline void blk_free_request(struct request_queue *q, struct request *rq) 639 { 640 if (rq->cmd_flags & REQ_ELVPRIV) 641 elv_put_request(q, rq); 642 mempool_free(rq, q->rq.rq_pool); 643 } 644 645 static struct request * 646 blk_alloc_request(struct request_queue *q, int flags, int priv, gfp_t gfp_mask) 647 { 648 struct request *rq = mempool_alloc(q->rq.rq_pool, gfp_mask); 649 650 if (!rq) 651 return NULL; 652 653 blk_rq_init(q, rq); 654 655 rq->cmd_flags = flags | REQ_ALLOCED; 656 657 if (priv) { 658 if (unlikely(elv_set_request(q, rq, gfp_mask))) { 659 mempool_free(rq, q->rq.rq_pool); 660 return NULL; 661 } 662 rq->cmd_flags |= REQ_ELVPRIV; 663 } 664 665 return rq; 666 } 667 668 /* 669 * ioc_batching returns true if the ioc is a valid batching request and 670 * should be given priority access to a request. 671 */ 672 static inline int ioc_batching(struct request_queue *q, struct io_context *ioc) 673 { 674 if (!ioc) 675 return 0; 676 677 /* 678 * Make sure the process is able to allocate at least 1 request 679 * even if the batch times out, otherwise we could theoretically 680 * lose wakeups. 681 */ 682 return ioc->nr_batch_requests == q->nr_batching || 683 (ioc->nr_batch_requests > 0 684 && time_before(jiffies, ioc->last_waited + BLK_BATCH_TIME)); 685 } 686 687 /* 688 * ioc_set_batching sets ioc to be a new "batcher" if it is not one. This 689 * will cause the process to be a "batcher" on all queues in the system. This 690 * is the behaviour we want though - once it gets a wakeup it should be given 691 * a nice run. 692 */ 693 static void ioc_set_batching(struct request_queue *q, struct io_context *ioc) 694 { 695 if (!ioc || ioc_batching(q, ioc)) 696 return; 697 698 ioc->nr_batch_requests = q->nr_batching; 699 ioc->last_waited = jiffies; 700 } 701 702 static void __freed_request(struct request_queue *q, int sync) 703 { 704 struct request_list *rl = &q->rq; 705 706 if (rl->count[sync] < queue_congestion_off_threshold(q)) 707 blk_clear_queue_congested(q, sync); 708 709 if (rl->count[sync] + 1 <= q->nr_requests) { 710 if (waitqueue_active(&rl->wait[sync])) 711 wake_up(&rl->wait[sync]); 712 713 blk_clear_queue_full(q, sync); 714 } 715 } 716 717 /* 718 * A request has just been released. Account for it, update the full and 719 * congestion status, wake up any waiters. Called under q->queue_lock. 720 */ 721 static void freed_request(struct request_queue *q, int sync, int priv) 722 { 723 struct request_list *rl = &q->rq; 724 725 rl->count[sync]--; 726 if (priv) 727 rl->elvpriv--; 728 729 __freed_request(q, sync); 730 731 if (unlikely(rl->starved[sync ^ 1])) 732 __freed_request(q, sync ^ 1); 733 } 734 735 /* 736 * Get a free request, queue_lock must be held. 737 * Returns NULL on failure, with queue_lock held. 738 * Returns !NULL on success, with queue_lock *not held*. 739 */ 740 static struct request *get_request(struct request_queue *q, int rw_flags, 741 struct bio *bio, gfp_t gfp_mask) 742 { 743 struct request *rq = NULL; 744 struct request_list *rl = &q->rq; 745 struct io_context *ioc = NULL; 746 const bool is_sync = rw_is_sync(rw_flags) != 0; 747 int may_queue, priv; 748 749 may_queue = elv_may_queue(q, rw_flags); 750 if (may_queue == ELV_MQUEUE_NO) 751 goto rq_starved; 752 753 if (rl->count[is_sync]+1 >= queue_congestion_on_threshold(q)) { 754 if (rl->count[is_sync]+1 >= q->nr_requests) { 755 ioc = current_io_context(GFP_ATOMIC, q->node); 756 /* 757 * The queue will fill after this allocation, so set 758 * it as full, and mark this process as "batching". 759 * This process will be allowed to complete a batch of 760 * requests, others will be blocked. 761 */ 762 if (!blk_queue_full(q, is_sync)) { 763 ioc_set_batching(q, ioc); 764 blk_set_queue_full(q, is_sync); 765 } else { 766 if (may_queue != ELV_MQUEUE_MUST 767 && !ioc_batching(q, ioc)) { 768 /* 769 * The queue is full and the allocating 770 * process is not a "batcher", and not 771 * exempted by the IO scheduler 772 */ 773 goto out; 774 } 775 } 776 } 777 blk_set_queue_congested(q, is_sync); 778 } 779 780 /* 781 * Only allow batching queuers to allocate up to 50% over the defined 782 * limit of requests, otherwise we could have thousands of requests 783 * allocated with any setting of ->nr_requests 784 */ 785 if (rl->count[is_sync] >= (3 * q->nr_requests / 2)) 786 goto out; 787 788 rl->count[is_sync]++; 789 rl->starved[is_sync] = 0; 790 791 priv = !test_bit(QUEUE_FLAG_ELVSWITCH, &q->queue_flags); 792 if (priv) 793 rl->elvpriv++; 794 795 if (blk_queue_io_stat(q)) 796 rw_flags |= REQ_IO_STAT; 797 spin_unlock_irq(q->queue_lock); 798 799 rq = blk_alloc_request(q, rw_flags, priv, gfp_mask); 800 if (unlikely(!rq)) { 801 /* 802 * Allocation failed presumably due to memory. Undo anything 803 * we might have messed up. 804 * 805 * Allocating task should really be put onto the front of the 806 * wait queue, but this is pretty rare. 807 */ 808 spin_lock_irq(q->queue_lock); 809 freed_request(q, is_sync, priv); 810 811 /* 812 * in the very unlikely event that allocation failed and no 813 * requests for this direction was pending, mark us starved 814 * so that freeing of a request in the other direction will 815 * notice us. another possible fix would be to split the 816 * rq mempool into READ and WRITE 817 */ 818 rq_starved: 819 if (unlikely(rl->count[is_sync] == 0)) 820 rl->starved[is_sync] = 1; 821 822 goto out; 823 } 824 825 /* 826 * ioc may be NULL here, and ioc_batching will be false. That's 827 * OK, if the queue is under the request limit then requests need 828 * not count toward the nr_batch_requests limit. There will always 829 * be some limit enforced by BLK_BATCH_TIME. 830 */ 831 if (ioc_batching(q, ioc)) 832 ioc->nr_batch_requests--; 833 834 trace_block_getrq(q, bio, rw_flags & 1); 835 out: 836 return rq; 837 } 838 839 /* 840 * No available requests for this queue, unplug the device and wait for some 841 * requests to become available. 842 * 843 * Called with q->queue_lock held, and returns with it unlocked. 844 */ 845 static struct request *get_request_wait(struct request_queue *q, int rw_flags, 846 struct bio *bio) 847 { 848 const bool is_sync = rw_is_sync(rw_flags) != 0; 849 struct request *rq; 850 851 rq = get_request(q, rw_flags, bio, GFP_NOIO); 852 while (!rq) { 853 DEFINE_WAIT(wait); 854 struct io_context *ioc; 855 struct request_list *rl = &q->rq; 856 857 prepare_to_wait_exclusive(&rl->wait[is_sync], &wait, 858 TASK_UNINTERRUPTIBLE); 859 860 trace_block_sleeprq(q, bio, rw_flags & 1); 861 862 __generic_unplug_device(q); 863 spin_unlock_irq(q->queue_lock); 864 io_schedule(); 865 866 /* 867 * After sleeping, we become a "batching" process and 868 * will be able to allocate at least one request, and 869 * up to a big batch of them for a small period time. 870 * See ioc_batching, ioc_set_batching 871 */ 872 ioc = current_io_context(GFP_NOIO, q->node); 873 ioc_set_batching(q, ioc); 874 875 spin_lock_irq(q->queue_lock); 876 finish_wait(&rl->wait[is_sync], &wait); 877 878 rq = get_request(q, rw_flags, bio, GFP_NOIO); 879 }; 880 881 return rq; 882 } 883 884 struct request *blk_get_request(struct request_queue *q, int rw, gfp_t gfp_mask) 885 { 886 struct request *rq; 887 888 BUG_ON(rw != READ && rw != WRITE); 889 890 spin_lock_irq(q->queue_lock); 891 if (gfp_mask & __GFP_WAIT) { 892 rq = get_request_wait(q, rw, NULL); 893 } else { 894 rq = get_request(q, rw, NULL, gfp_mask); 895 if (!rq) 896 spin_unlock_irq(q->queue_lock); 897 } 898 /* q->queue_lock is unlocked at this point */ 899 900 return rq; 901 } 902 EXPORT_SYMBOL(blk_get_request); 903 904 /** 905 * blk_start_queueing - initiate dispatch of requests to device 906 * @q: request queue to kick into gear 907 * 908 * This is basically a helper to remove the need to know whether a queue 909 * is plugged or not if someone just wants to initiate dispatch of requests 910 * for this queue. Should be used to start queueing on a device outside 911 * of ->request_fn() context. Also see @blk_run_queue. 912 * 913 * The queue lock must be held with interrupts disabled. 914 */ 915 void blk_start_queueing(struct request_queue *q) 916 { 917 if (!blk_queue_plugged(q)) { 918 if (unlikely(blk_queue_stopped(q))) 919 return; 920 q->request_fn(q); 921 } else 922 __generic_unplug_device(q); 923 } 924 EXPORT_SYMBOL(blk_start_queueing); 925 926 /** 927 * blk_requeue_request - put a request back on queue 928 * @q: request queue where request should be inserted 929 * @rq: request to be inserted 930 * 931 * Description: 932 * Drivers often keep queueing requests until the hardware cannot accept 933 * more, when that condition happens we need to put the request back 934 * on the queue. Must be called with queue lock held. 935 */ 936 void blk_requeue_request(struct request_queue *q, struct request *rq) 937 { 938 blk_delete_timer(rq); 939 blk_clear_rq_complete(rq); 940 trace_block_rq_requeue(q, rq); 941 942 if (blk_rq_tagged(rq)) 943 blk_queue_end_tag(q, rq); 944 945 elv_requeue_request(q, rq); 946 } 947 EXPORT_SYMBOL(blk_requeue_request); 948 949 /** 950 * blk_insert_request - insert a special request into a request queue 951 * @q: request queue where request should be inserted 952 * @rq: request to be inserted 953 * @at_head: insert request at head or tail of queue 954 * @data: private data 955 * 956 * Description: 957 * Many block devices need to execute commands asynchronously, so they don't 958 * block the whole kernel from preemption during request execution. This is 959 * accomplished normally by inserting aritficial requests tagged as 960 * REQ_TYPE_SPECIAL in to the corresponding request queue, and letting them 961 * be scheduled for actual execution by the request queue. 962 * 963 * We have the option of inserting the head or the tail of the queue. 964 * Typically we use the tail for new ioctls and so forth. We use the head 965 * of the queue for things like a QUEUE_FULL message from a device, or a 966 * host that is unable to accept a particular command. 967 */ 968 void blk_insert_request(struct request_queue *q, struct request *rq, 969 int at_head, void *data) 970 { 971 int where = at_head ? ELEVATOR_INSERT_FRONT : ELEVATOR_INSERT_BACK; 972 unsigned long flags; 973 974 /* 975 * tell I/O scheduler that this isn't a regular read/write (ie it 976 * must not attempt merges on this) and that it acts as a soft 977 * barrier 978 */ 979 rq->cmd_type = REQ_TYPE_SPECIAL; 980 rq->cmd_flags |= REQ_SOFTBARRIER; 981 982 rq->special = data; 983 984 spin_lock_irqsave(q->queue_lock, flags); 985 986 /* 987 * If command is tagged, release the tag 988 */ 989 if (blk_rq_tagged(rq)) 990 blk_queue_end_tag(q, rq); 991 992 drive_stat_acct(rq, 1); 993 __elv_add_request(q, rq, where, 0); 994 blk_start_queueing(q); 995 spin_unlock_irqrestore(q->queue_lock, flags); 996 } 997 EXPORT_SYMBOL(blk_insert_request); 998 999 /* 1000 * add-request adds a request to the linked list. 1001 * queue lock is held and interrupts disabled, as we muck with the 1002 * request queue list. 1003 */ 1004 static inline void add_request(struct request_queue *q, struct request *req) 1005 { 1006 drive_stat_acct(req, 1); 1007 1008 /* 1009 * elevator indicated where it wants this request to be 1010 * inserted at elevator_merge time 1011 */ 1012 __elv_add_request(q, req, ELEVATOR_INSERT_SORT, 0); 1013 } 1014 1015 static void part_round_stats_single(int cpu, struct hd_struct *part, 1016 unsigned long now) 1017 { 1018 if (now == part->stamp) 1019 return; 1020 1021 if (part->in_flight) { 1022 __part_stat_add(cpu, part, time_in_queue, 1023 part->in_flight * (now - part->stamp)); 1024 __part_stat_add(cpu, part, io_ticks, (now - part->stamp)); 1025 } 1026 part->stamp = now; 1027 } 1028 1029 /** 1030 * part_round_stats() - Round off the performance stats on a struct disk_stats. 1031 * @cpu: cpu number for stats access 1032 * @part: target partition 1033 * 1034 * The average IO queue length and utilisation statistics are maintained 1035 * by observing the current state of the queue length and the amount of 1036 * time it has been in this state for. 1037 * 1038 * Normally, that accounting is done on IO completion, but that can result 1039 * in more than a second's worth of IO being accounted for within any one 1040 * second, leading to >100% utilisation. To deal with that, we call this 1041 * function to do a round-off before returning the results when reading 1042 * /proc/diskstats. This accounts immediately for all queue usage up to 1043 * the current jiffies and restarts the counters again. 1044 */ 1045 void part_round_stats(int cpu, struct hd_struct *part) 1046 { 1047 unsigned long now = jiffies; 1048 1049 if (part->partno) 1050 part_round_stats_single(cpu, &part_to_disk(part)->part0, now); 1051 part_round_stats_single(cpu, part, now); 1052 } 1053 EXPORT_SYMBOL_GPL(part_round_stats); 1054 1055 /* 1056 * queue lock must be held 1057 */ 1058 void __blk_put_request(struct request_queue *q, struct request *req) 1059 { 1060 if (unlikely(!q)) 1061 return; 1062 if (unlikely(--req->ref_count)) 1063 return; 1064 1065 elv_completed_request(q, req); 1066 1067 /* this is a bio leak */ 1068 WARN_ON(req->bio != NULL); 1069 1070 /* 1071 * Request may not have originated from ll_rw_blk. if not, 1072 * it didn't come out of our reserved rq pools 1073 */ 1074 if (req->cmd_flags & REQ_ALLOCED) { 1075 int is_sync = rq_is_sync(req) != 0; 1076 int priv = req->cmd_flags & REQ_ELVPRIV; 1077 1078 BUG_ON(!list_empty(&req->queuelist)); 1079 BUG_ON(!hlist_unhashed(&req->hash)); 1080 1081 blk_free_request(q, req); 1082 freed_request(q, is_sync, priv); 1083 } 1084 } 1085 EXPORT_SYMBOL_GPL(__blk_put_request); 1086 1087 void blk_put_request(struct request *req) 1088 { 1089 unsigned long flags; 1090 struct request_queue *q = req->q; 1091 1092 spin_lock_irqsave(q->queue_lock, flags); 1093 __blk_put_request(q, req); 1094 spin_unlock_irqrestore(q->queue_lock, flags); 1095 } 1096 EXPORT_SYMBOL(blk_put_request); 1097 1098 void init_request_from_bio(struct request *req, struct bio *bio) 1099 { 1100 req->cpu = bio->bi_comp_cpu; 1101 req->cmd_type = REQ_TYPE_FS; 1102 1103 /* 1104 * inherit FAILFAST from bio (for read-ahead, and explicit FAILFAST) 1105 */ 1106 if (bio_rw_ahead(bio)) 1107 req->cmd_flags |= (REQ_FAILFAST_DEV | REQ_FAILFAST_TRANSPORT | 1108 REQ_FAILFAST_DRIVER); 1109 if (bio_failfast_dev(bio)) 1110 req->cmd_flags |= REQ_FAILFAST_DEV; 1111 if (bio_failfast_transport(bio)) 1112 req->cmd_flags |= REQ_FAILFAST_TRANSPORT; 1113 if (bio_failfast_driver(bio)) 1114 req->cmd_flags |= REQ_FAILFAST_DRIVER; 1115 1116 /* 1117 * REQ_BARRIER implies no merging, but lets make it explicit 1118 */ 1119 if (unlikely(bio_discard(bio))) { 1120 req->cmd_flags |= REQ_DISCARD; 1121 if (bio_barrier(bio)) 1122 req->cmd_flags |= REQ_SOFTBARRIER; 1123 req->q->prepare_discard_fn(req->q, req); 1124 } else if (unlikely(bio_barrier(bio))) 1125 req->cmd_flags |= (REQ_HARDBARRIER | REQ_NOMERGE); 1126 1127 if (bio_sync(bio)) 1128 req->cmd_flags |= REQ_RW_SYNC; 1129 if (bio_rw_meta(bio)) 1130 req->cmd_flags |= REQ_RW_META; 1131 if (bio_noidle(bio)) 1132 req->cmd_flags |= REQ_NOIDLE; 1133 1134 req->errors = 0; 1135 req->hard_sector = req->sector = bio->bi_sector; 1136 req->ioprio = bio_prio(bio); 1137 req->start_time = jiffies; 1138 blk_rq_bio_prep(req->q, req, bio); 1139 } 1140 1141 /* 1142 * Only disabling plugging for non-rotational devices if it does tagging 1143 * as well, otherwise we do need the proper merging 1144 */ 1145 static inline bool queue_should_plug(struct request_queue *q) 1146 { 1147 return !(blk_queue_nonrot(q) && blk_queue_tagged(q)); 1148 } 1149 1150 static int __make_request(struct request_queue *q, struct bio *bio) 1151 { 1152 struct request *req; 1153 int el_ret, nr_sectors; 1154 const unsigned short prio = bio_prio(bio); 1155 const int sync = bio_sync(bio); 1156 const int unplug = bio_unplug(bio); 1157 int rw_flags; 1158 1159 nr_sectors = bio_sectors(bio); 1160 1161 /* 1162 * low level driver can indicate that it wants pages above a 1163 * certain limit bounced to low memory (ie for highmem, or even 1164 * ISA dma in theory) 1165 */ 1166 blk_queue_bounce(q, &bio); 1167 1168 spin_lock_irq(q->queue_lock); 1169 1170 if (unlikely(bio_barrier(bio)) || elv_queue_empty(q)) 1171 goto get_rq; 1172 1173 el_ret = elv_merge(q, &req, bio); 1174 switch (el_ret) { 1175 case ELEVATOR_BACK_MERGE: 1176 BUG_ON(!rq_mergeable(req)); 1177 1178 if (!ll_back_merge_fn(q, req, bio)) 1179 break; 1180 1181 trace_block_bio_backmerge(q, bio); 1182 1183 req->biotail->bi_next = bio; 1184 req->biotail = bio; 1185 req->nr_sectors = req->hard_nr_sectors += nr_sectors; 1186 req->ioprio = ioprio_best(req->ioprio, prio); 1187 if (!blk_rq_cpu_valid(req)) 1188 req->cpu = bio->bi_comp_cpu; 1189 drive_stat_acct(req, 0); 1190 if (!attempt_back_merge(q, req)) 1191 elv_merged_request(q, req, el_ret); 1192 goto out; 1193 1194 case ELEVATOR_FRONT_MERGE: 1195 BUG_ON(!rq_mergeable(req)); 1196 1197 if (!ll_front_merge_fn(q, req, bio)) 1198 break; 1199 1200 trace_block_bio_frontmerge(q, bio); 1201 1202 bio->bi_next = req->bio; 1203 req->bio = bio; 1204 1205 /* 1206 * may not be valid. if the low level driver said 1207 * it didn't need a bounce buffer then it better 1208 * not touch req->buffer either... 1209 */ 1210 req->buffer = bio_data(bio); 1211 req->current_nr_sectors = bio_cur_sectors(bio); 1212 req->hard_cur_sectors = req->current_nr_sectors; 1213 req->sector = req->hard_sector = bio->bi_sector; 1214 req->nr_sectors = req->hard_nr_sectors += nr_sectors; 1215 req->ioprio = ioprio_best(req->ioprio, prio); 1216 if (!blk_rq_cpu_valid(req)) 1217 req->cpu = bio->bi_comp_cpu; 1218 drive_stat_acct(req, 0); 1219 if (!attempt_front_merge(q, req)) 1220 elv_merged_request(q, req, el_ret); 1221 goto out; 1222 1223 /* ELV_NO_MERGE: elevator says don't/can't merge. */ 1224 default: 1225 ; 1226 } 1227 1228 get_rq: 1229 /* 1230 * This sync check and mask will be re-done in init_request_from_bio(), 1231 * but we need to set it earlier to expose the sync flag to the 1232 * rq allocator and io schedulers. 1233 */ 1234 rw_flags = bio_data_dir(bio); 1235 if (sync) 1236 rw_flags |= REQ_RW_SYNC; 1237 1238 /* 1239 * Grab a free request. This is might sleep but can not fail. 1240 * Returns with the queue unlocked. 1241 */ 1242 req = get_request_wait(q, rw_flags, bio); 1243 1244 /* 1245 * After dropping the lock and possibly sleeping here, our request 1246 * may now be mergeable after it had proven unmergeable (above). 1247 * We don't worry about that case for efficiency. It won't happen 1248 * often, and the elevators are able to handle it. 1249 */ 1250 init_request_from_bio(req, bio); 1251 1252 spin_lock_irq(q->queue_lock); 1253 if (test_bit(QUEUE_FLAG_SAME_COMP, &q->queue_flags) || 1254 bio_flagged(bio, BIO_CPU_AFFINE)) 1255 req->cpu = blk_cpu_to_group(smp_processor_id()); 1256 if (queue_should_plug(q) && elv_queue_empty(q)) 1257 blk_plug_device(q); 1258 add_request(q, req); 1259 out: 1260 if (unplug || !queue_should_plug(q)) 1261 __generic_unplug_device(q); 1262 spin_unlock_irq(q->queue_lock); 1263 return 0; 1264 } 1265 1266 /* 1267 * If bio->bi_dev is a partition, remap the location 1268 */ 1269 static inline void blk_partition_remap(struct bio *bio) 1270 { 1271 struct block_device *bdev = bio->bi_bdev; 1272 1273 if (bio_sectors(bio) && bdev != bdev->bd_contains) { 1274 struct hd_struct *p = bdev->bd_part; 1275 1276 bio->bi_sector += p->start_sect; 1277 bio->bi_bdev = bdev->bd_contains; 1278 1279 trace_block_remap(bdev_get_queue(bio->bi_bdev), bio, 1280 bdev->bd_dev, bio->bi_sector, 1281 bio->bi_sector - p->start_sect); 1282 } 1283 } 1284 1285 static void handle_bad_sector(struct bio *bio) 1286 { 1287 char b[BDEVNAME_SIZE]; 1288 1289 printk(KERN_INFO "attempt to access beyond end of device\n"); 1290 printk(KERN_INFO "%s: rw=%ld, want=%Lu, limit=%Lu\n", 1291 bdevname(bio->bi_bdev, b), 1292 bio->bi_rw, 1293 (unsigned long long)bio->bi_sector + bio_sectors(bio), 1294 (long long)(bio->bi_bdev->bd_inode->i_size >> 9)); 1295 1296 set_bit(BIO_EOF, &bio->bi_flags); 1297 } 1298 1299 #ifdef CONFIG_FAIL_MAKE_REQUEST 1300 1301 static DECLARE_FAULT_ATTR(fail_make_request); 1302 1303 static int __init setup_fail_make_request(char *str) 1304 { 1305 return setup_fault_attr(&fail_make_request, str); 1306 } 1307 __setup("fail_make_request=", setup_fail_make_request); 1308 1309 static int should_fail_request(struct bio *bio) 1310 { 1311 struct hd_struct *part = bio->bi_bdev->bd_part; 1312 1313 if (part_to_disk(part)->part0.make_it_fail || part->make_it_fail) 1314 return should_fail(&fail_make_request, bio->bi_size); 1315 1316 return 0; 1317 } 1318 1319 static int __init fail_make_request_debugfs(void) 1320 { 1321 return init_fault_attr_dentries(&fail_make_request, 1322 "fail_make_request"); 1323 } 1324 1325 late_initcall(fail_make_request_debugfs); 1326 1327 #else /* CONFIG_FAIL_MAKE_REQUEST */ 1328 1329 static inline int should_fail_request(struct bio *bio) 1330 { 1331 return 0; 1332 } 1333 1334 #endif /* CONFIG_FAIL_MAKE_REQUEST */ 1335 1336 /* 1337 * Check whether this bio extends beyond the end of the device. 1338 */ 1339 static inline int bio_check_eod(struct bio *bio, unsigned int nr_sectors) 1340 { 1341 sector_t maxsector; 1342 1343 if (!nr_sectors) 1344 return 0; 1345 1346 /* Test device or partition size, when known. */ 1347 maxsector = bio->bi_bdev->bd_inode->i_size >> 9; 1348 if (maxsector) { 1349 sector_t sector = bio->bi_sector; 1350 1351 if (maxsector < nr_sectors || maxsector - nr_sectors < sector) { 1352 /* 1353 * This may well happen - the kernel calls bread() 1354 * without checking the size of the device, e.g., when 1355 * mounting a device. 1356 */ 1357 handle_bad_sector(bio); 1358 return 1; 1359 } 1360 } 1361 1362 return 0; 1363 } 1364 1365 /** 1366 * generic_make_request - hand a buffer to its device driver for I/O 1367 * @bio: The bio describing the location in memory and on the device. 1368 * 1369 * generic_make_request() is used to make I/O requests of block 1370 * devices. It is passed a &struct bio, which describes the I/O that needs 1371 * to be done. 1372 * 1373 * generic_make_request() does not return any status. The 1374 * success/failure status of the request, along with notification of 1375 * completion, is delivered asynchronously through the bio->bi_end_io 1376 * function described (one day) else where. 1377 * 1378 * The caller of generic_make_request must make sure that bi_io_vec 1379 * are set to describe the memory buffer, and that bi_dev and bi_sector are 1380 * set to describe the device address, and the 1381 * bi_end_io and optionally bi_private are set to describe how 1382 * completion notification should be signaled. 1383 * 1384 * generic_make_request and the drivers it calls may use bi_next if this 1385 * bio happens to be merged with someone else, and may change bi_dev and 1386 * bi_sector for remaps as it sees fit. So the values of these fields 1387 * should NOT be depended on after the call to generic_make_request. 1388 */ 1389 static inline void __generic_make_request(struct bio *bio) 1390 { 1391 struct request_queue *q; 1392 sector_t old_sector; 1393 int ret, nr_sectors = bio_sectors(bio); 1394 dev_t old_dev; 1395 int err = -EIO; 1396 1397 might_sleep(); 1398 1399 if (bio_check_eod(bio, nr_sectors)) 1400 goto end_io; 1401 1402 /* 1403 * Resolve the mapping until finished. (drivers are 1404 * still free to implement/resolve their own stacking 1405 * by explicitly returning 0) 1406 * 1407 * NOTE: we don't repeat the blk_size check for each new device. 1408 * Stacking drivers are expected to know what they are doing. 1409 */ 1410 old_sector = -1; 1411 old_dev = 0; 1412 do { 1413 char b[BDEVNAME_SIZE]; 1414 1415 q = bdev_get_queue(bio->bi_bdev); 1416 if (unlikely(!q)) { 1417 printk(KERN_ERR 1418 "generic_make_request: Trying to access " 1419 "nonexistent block-device %s (%Lu)\n", 1420 bdevname(bio->bi_bdev, b), 1421 (long long) bio->bi_sector); 1422 goto end_io; 1423 } 1424 1425 if (unlikely(nr_sectors > q->max_hw_sectors)) { 1426 printk(KERN_ERR "bio too big device %s (%u > %u)\n", 1427 bdevname(bio->bi_bdev, b), 1428 bio_sectors(bio), 1429 q->max_hw_sectors); 1430 goto end_io; 1431 } 1432 1433 if (unlikely(test_bit(QUEUE_FLAG_DEAD, &q->queue_flags))) 1434 goto end_io; 1435 1436 if (should_fail_request(bio)) 1437 goto end_io; 1438 1439 /* 1440 * If this device has partitions, remap block n 1441 * of partition p to block n+start(p) of the disk. 1442 */ 1443 blk_partition_remap(bio); 1444 1445 if (bio_integrity_enabled(bio) && bio_integrity_prep(bio)) 1446 goto end_io; 1447 1448 if (old_sector != -1) 1449 trace_block_remap(q, bio, old_dev, bio->bi_sector, 1450 old_sector); 1451 1452 trace_block_bio_queue(q, bio); 1453 1454 old_sector = bio->bi_sector; 1455 old_dev = bio->bi_bdev->bd_dev; 1456 1457 if (bio_check_eod(bio, nr_sectors)) 1458 goto end_io; 1459 1460 if (bio_discard(bio) && !q->prepare_discard_fn) { 1461 err = -EOPNOTSUPP; 1462 goto end_io; 1463 } 1464 if (bio_barrier(bio) && bio_has_data(bio) && 1465 (q->next_ordered == QUEUE_ORDERED_NONE)) { 1466 err = -EOPNOTSUPP; 1467 goto end_io; 1468 } 1469 1470 ret = q->make_request_fn(q, bio); 1471 } while (ret); 1472 1473 return; 1474 1475 end_io: 1476 bio_endio(bio, err); 1477 } 1478 1479 /* 1480 * We only want one ->make_request_fn to be active at a time, 1481 * else stack usage with stacked devices could be a problem. 1482 * So use current->bio_{list,tail} to keep a list of requests 1483 * submited by a make_request_fn function. 1484 * current->bio_tail is also used as a flag to say if 1485 * generic_make_request is currently active in this task or not. 1486 * If it is NULL, then no make_request is active. If it is non-NULL, 1487 * then a make_request is active, and new requests should be added 1488 * at the tail 1489 */ 1490 void generic_make_request(struct bio *bio) 1491 { 1492 if (current->bio_tail) { 1493 /* make_request is active */ 1494 *(current->bio_tail) = bio; 1495 bio->bi_next = NULL; 1496 current->bio_tail = &bio->bi_next; 1497 return; 1498 } 1499 /* following loop may be a bit non-obvious, and so deserves some 1500 * explanation. 1501 * Before entering the loop, bio->bi_next is NULL (as all callers 1502 * ensure that) so we have a list with a single bio. 1503 * We pretend that we have just taken it off a longer list, so 1504 * we assign bio_list to the next (which is NULL) and bio_tail 1505 * to &bio_list, thus initialising the bio_list of new bios to be 1506 * added. __generic_make_request may indeed add some more bios 1507 * through a recursive call to generic_make_request. If it 1508 * did, we find a non-NULL value in bio_list and re-enter the loop 1509 * from the top. In this case we really did just take the bio 1510 * of the top of the list (no pretending) and so fixup bio_list and 1511 * bio_tail or bi_next, and call into __generic_make_request again. 1512 * 1513 * The loop was structured like this to make only one call to 1514 * __generic_make_request (which is important as it is large and 1515 * inlined) and to keep the structure simple. 1516 */ 1517 BUG_ON(bio->bi_next); 1518 do { 1519 current->bio_list = bio->bi_next; 1520 if (bio->bi_next == NULL) 1521 current->bio_tail = ¤t->bio_list; 1522 else 1523 bio->bi_next = NULL; 1524 __generic_make_request(bio); 1525 bio = current->bio_list; 1526 } while (bio); 1527 current->bio_tail = NULL; /* deactivate */ 1528 } 1529 EXPORT_SYMBOL(generic_make_request); 1530 1531 /** 1532 * submit_bio - submit a bio to the block device layer for I/O 1533 * @rw: whether to %READ or %WRITE, or maybe to %READA (read ahead) 1534 * @bio: The &struct bio which describes the I/O 1535 * 1536 * submit_bio() is very similar in purpose to generic_make_request(), and 1537 * uses that function to do most of the work. Both are fairly rough 1538 * interfaces; @bio must be presetup and ready for I/O. 1539 * 1540 */ 1541 void submit_bio(int rw, struct bio *bio) 1542 { 1543 int count = bio_sectors(bio); 1544 1545 bio->bi_rw |= rw; 1546 1547 /* 1548 * If it's a regular read/write or a barrier with data attached, 1549 * go through the normal accounting stuff before submission. 1550 */ 1551 if (bio_has_data(bio)) { 1552 if (rw & WRITE) { 1553 count_vm_events(PGPGOUT, count); 1554 } else { 1555 task_io_account_read(bio->bi_size); 1556 count_vm_events(PGPGIN, count); 1557 } 1558 1559 if (unlikely(block_dump)) { 1560 char b[BDEVNAME_SIZE]; 1561 printk(KERN_DEBUG "%s(%d): %s block %Lu on %s\n", 1562 current->comm, task_pid_nr(current), 1563 (rw & WRITE) ? "WRITE" : "READ", 1564 (unsigned long long)bio->bi_sector, 1565 bdevname(bio->bi_bdev, b)); 1566 } 1567 } 1568 1569 generic_make_request(bio); 1570 } 1571 EXPORT_SYMBOL(submit_bio); 1572 1573 /** 1574 * blk_rq_check_limits - Helper function to check a request for the queue limit 1575 * @q: the queue 1576 * @rq: the request being checked 1577 * 1578 * Description: 1579 * @rq may have been made based on weaker limitations of upper-level queues 1580 * in request stacking drivers, and it may violate the limitation of @q. 1581 * Since the block layer and the underlying device driver trust @rq 1582 * after it is inserted to @q, it should be checked against @q before 1583 * the insertion using this generic function. 1584 * 1585 * This function should also be useful for request stacking drivers 1586 * in some cases below, so export this fuction. 1587 * Request stacking drivers like request-based dm may change the queue 1588 * limits while requests are in the queue (e.g. dm's table swapping). 1589 * Such request stacking drivers should check those requests agaist 1590 * the new queue limits again when they dispatch those requests, 1591 * although such checkings are also done against the old queue limits 1592 * when submitting requests. 1593 */ 1594 int blk_rq_check_limits(struct request_queue *q, struct request *rq) 1595 { 1596 if (rq->nr_sectors > q->max_sectors || 1597 rq->data_len > q->max_hw_sectors << 9) { 1598 printk(KERN_ERR "%s: over max size limit.\n", __func__); 1599 return -EIO; 1600 } 1601 1602 /* 1603 * queue's settings related to segment counting like q->bounce_pfn 1604 * may differ from that of other stacking queues. 1605 * Recalculate it to check the request correctly on this queue's 1606 * limitation. 1607 */ 1608 blk_recalc_rq_segments(rq); 1609 if (rq->nr_phys_segments > q->max_phys_segments || 1610 rq->nr_phys_segments > q->max_hw_segments) { 1611 printk(KERN_ERR "%s: over max segments limit.\n", __func__); 1612 return -EIO; 1613 } 1614 1615 return 0; 1616 } 1617 EXPORT_SYMBOL_GPL(blk_rq_check_limits); 1618 1619 /** 1620 * blk_insert_cloned_request - Helper for stacking drivers to submit a request 1621 * @q: the queue to submit the request 1622 * @rq: the request being queued 1623 */ 1624 int blk_insert_cloned_request(struct request_queue *q, struct request *rq) 1625 { 1626 unsigned long flags; 1627 1628 if (blk_rq_check_limits(q, rq)) 1629 return -EIO; 1630 1631 #ifdef CONFIG_FAIL_MAKE_REQUEST 1632 if (rq->rq_disk && rq->rq_disk->part0.make_it_fail && 1633 should_fail(&fail_make_request, blk_rq_bytes(rq))) 1634 return -EIO; 1635 #endif 1636 1637 spin_lock_irqsave(q->queue_lock, flags); 1638 1639 /* 1640 * Submitting request must be dequeued before calling this function 1641 * because it will be linked to another request_queue 1642 */ 1643 BUG_ON(blk_queued_rq(rq)); 1644 1645 drive_stat_acct(rq, 1); 1646 __elv_add_request(q, rq, ELEVATOR_INSERT_BACK, 0); 1647 1648 spin_unlock_irqrestore(q->queue_lock, flags); 1649 1650 return 0; 1651 } 1652 EXPORT_SYMBOL_GPL(blk_insert_cloned_request); 1653 1654 /** 1655 * blkdev_dequeue_request - dequeue request and start timeout timer 1656 * @req: request to dequeue 1657 * 1658 * Dequeue @req and start timeout timer on it. This hands off the 1659 * request to the driver. 1660 * 1661 * Block internal functions which don't want to start timer should 1662 * call elv_dequeue_request(). 1663 */ 1664 void blkdev_dequeue_request(struct request *req) 1665 { 1666 elv_dequeue_request(req->q, req); 1667 1668 /* 1669 * We are now handing the request to the hardware, add the 1670 * timeout handler. 1671 */ 1672 blk_add_timer(req); 1673 } 1674 EXPORT_SYMBOL(blkdev_dequeue_request); 1675 1676 static void blk_account_io_completion(struct request *req, unsigned int bytes) 1677 { 1678 if (!blk_do_io_stat(req)) 1679 return; 1680 1681 if (blk_fs_request(req)) { 1682 const int rw = rq_data_dir(req); 1683 struct hd_struct *part; 1684 int cpu; 1685 1686 cpu = part_stat_lock(); 1687 part = disk_map_sector_rcu(req->rq_disk, req->sector); 1688 part_stat_add(cpu, part, sectors[rw], bytes >> 9); 1689 part_stat_unlock(); 1690 } 1691 } 1692 1693 static void blk_account_io_done(struct request *req) 1694 { 1695 if (!blk_do_io_stat(req)) 1696 return; 1697 1698 /* 1699 * Account IO completion. bar_rq isn't accounted as a normal 1700 * IO on queueing nor completion. Accounting the containing 1701 * request is enough. 1702 */ 1703 if (blk_fs_request(req) && req != &req->q->bar_rq) { 1704 unsigned long duration = jiffies - req->start_time; 1705 const int rw = rq_data_dir(req); 1706 struct hd_struct *part; 1707 int cpu; 1708 1709 cpu = part_stat_lock(); 1710 part = disk_map_sector_rcu(req->rq_disk, req->sector); 1711 1712 part_stat_inc(cpu, part, ios[rw]); 1713 part_stat_add(cpu, part, ticks[rw], duration); 1714 part_round_stats(cpu, part); 1715 part_dec_in_flight(part); 1716 1717 part_stat_unlock(); 1718 } 1719 } 1720 1721 /** 1722 * __end_that_request_first - end I/O on a request 1723 * @req: the request being processed 1724 * @error: %0 for success, < %0 for error 1725 * @nr_bytes: number of bytes to complete 1726 * 1727 * Description: 1728 * Ends I/O on a number of bytes attached to @req, and sets it up 1729 * for the next range of segments (if any) in the cluster. 1730 * 1731 * Return: 1732 * %0 - we are done with this request, call end_that_request_last() 1733 * %1 - still buffers pending for this request 1734 **/ 1735 static int __end_that_request_first(struct request *req, int error, 1736 int nr_bytes) 1737 { 1738 int total_bytes, bio_nbytes, next_idx = 0; 1739 struct bio *bio; 1740 1741 trace_block_rq_complete(req->q, req); 1742 1743 /* 1744 * for a REQ_TYPE_BLOCK_PC request, we want to carry any eventual 1745 * sense key with us all the way through 1746 */ 1747 if (!blk_pc_request(req)) 1748 req->errors = 0; 1749 1750 if (error && (blk_fs_request(req) && !(req->cmd_flags & REQ_QUIET))) { 1751 printk(KERN_ERR "end_request: I/O error, dev %s, sector %llu\n", 1752 req->rq_disk ? req->rq_disk->disk_name : "?", 1753 (unsigned long long)req->sector); 1754 } 1755 1756 blk_account_io_completion(req, nr_bytes); 1757 1758 total_bytes = bio_nbytes = 0; 1759 while ((bio = req->bio) != NULL) { 1760 int nbytes; 1761 1762 if (nr_bytes >= bio->bi_size) { 1763 req->bio = bio->bi_next; 1764 nbytes = bio->bi_size; 1765 req_bio_endio(req, bio, nbytes, error); 1766 next_idx = 0; 1767 bio_nbytes = 0; 1768 } else { 1769 int idx = bio->bi_idx + next_idx; 1770 1771 if (unlikely(idx >= bio->bi_vcnt)) { 1772 blk_dump_rq_flags(req, "__end_that"); 1773 printk(KERN_ERR "%s: bio idx %d >= vcnt %d\n", 1774 __func__, idx, bio->bi_vcnt); 1775 break; 1776 } 1777 1778 nbytes = bio_iovec_idx(bio, idx)->bv_len; 1779 BIO_BUG_ON(nbytes > bio->bi_size); 1780 1781 /* 1782 * not a complete bvec done 1783 */ 1784 if (unlikely(nbytes > nr_bytes)) { 1785 bio_nbytes += nr_bytes; 1786 total_bytes += nr_bytes; 1787 break; 1788 } 1789 1790 /* 1791 * advance to the next vector 1792 */ 1793 next_idx++; 1794 bio_nbytes += nbytes; 1795 } 1796 1797 total_bytes += nbytes; 1798 nr_bytes -= nbytes; 1799 1800 bio = req->bio; 1801 if (bio) { 1802 /* 1803 * end more in this run, or just return 'not-done' 1804 */ 1805 if (unlikely(nr_bytes <= 0)) 1806 break; 1807 } 1808 } 1809 1810 /* 1811 * completely done 1812 */ 1813 if (!req->bio) 1814 return 0; 1815 1816 /* 1817 * if the request wasn't completed, update state 1818 */ 1819 if (bio_nbytes) { 1820 req_bio_endio(req, bio, bio_nbytes, error); 1821 bio->bi_idx += next_idx; 1822 bio_iovec(bio)->bv_offset += nr_bytes; 1823 bio_iovec(bio)->bv_len -= nr_bytes; 1824 } 1825 1826 blk_recalc_rq_sectors(req, total_bytes >> 9); 1827 blk_recalc_rq_segments(req); 1828 return 1; 1829 } 1830 1831 /* 1832 * queue lock must be held 1833 */ 1834 static void end_that_request_last(struct request *req, int error) 1835 { 1836 if (blk_rq_tagged(req)) 1837 blk_queue_end_tag(req->q, req); 1838 1839 if (blk_queued_rq(req)) 1840 elv_dequeue_request(req->q, req); 1841 1842 if (unlikely(laptop_mode) && blk_fs_request(req)) 1843 laptop_io_completion(); 1844 1845 blk_delete_timer(req); 1846 1847 blk_account_io_done(req); 1848 1849 if (req->end_io) 1850 req->end_io(req, error); 1851 else { 1852 if (blk_bidi_rq(req)) 1853 __blk_put_request(req->next_rq->q, req->next_rq); 1854 1855 __blk_put_request(req->q, req); 1856 } 1857 } 1858 1859 /** 1860 * blk_rq_bytes - Returns bytes left to complete in the entire request 1861 * @rq: the request being processed 1862 **/ 1863 unsigned int blk_rq_bytes(struct request *rq) 1864 { 1865 if (blk_fs_request(rq)) 1866 return rq->hard_nr_sectors << 9; 1867 1868 return rq->data_len; 1869 } 1870 EXPORT_SYMBOL_GPL(blk_rq_bytes); 1871 1872 /** 1873 * blk_rq_cur_bytes - Returns bytes left to complete in the current segment 1874 * @rq: the request being processed 1875 **/ 1876 unsigned int blk_rq_cur_bytes(struct request *rq) 1877 { 1878 if (blk_fs_request(rq)) 1879 return rq->current_nr_sectors << 9; 1880 1881 if (rq->bio) 1882 return rq->bio->bi_size; 1883 1884 return rq->data_len; 1885 } 1886 EXPORT_SYMBOL_GPL(blk_rq_cur_bytes); 1887 1888 /** 1889 * end_request - end I/O on the current segment of the request 1890 * @req: the request being processed 1891 * @uptodate: error value or %0/%1 uptodate flag 1892 * 1893 * Description: 1894 * Ends I/O on the current segment of a request. If that is the only 1895 * remaining segment, the request is also completed and freed. 1896 * 1897 * This is a remnant of how older block drivers handled I/O completions. 1898 * Modern drivers typically end I/O on the full request in one go, unless 1899 * they have a residual value to account for. For that case this function 1900 * isn't really useful, unless the residual just happens to be the 1901 * full current segment. In other words, don't use this function in new 1902 * code. Use blk_end_request() or __blk_end_request() to end a request. 1903 **/ 1904 void end_request(struct request *req, int uptodate) 1905 { 1906 int error = 0; 1907 1908 if (uptodate <= 0) 1909 error = uptodate ? uptodate : -EIO; 1910 1911 __blk_end_request(req, error, req->hard_cur_sectors << 9); 1912 } 1913 EXPORT_SYMBOL(end_request); 1914 1915 static int end_that_request_data(struct request *rq, int error, 1916 unsigned int nr_bytes, unsigned int bidi_bytes) 1917 { 1918 if (rq->bio) { 1919 if (__end_that_request_first(rq, error, nr_bytes)) 1920 return 1; 1921 1922 /* Bidi request must be completed as a whole */ 1923 if (blk_bidi_rq(rq) && 1924 __end_that_request_first(rq->next_rq, error, bidi_bytes)) 1925 return 1; 1926 } 1927 1928 return 0; 1929 } 1930 1931 /** 1932 * blk_end_io - Generic end_io function to complete a request. 1933 * @rq: the request being processed 1934 * @error: %0 for success, < %0 for error 1935 * @nr_bytes: number of bytes to complete @rq 1936 * @bidi_bytes: number of bytes to complete @rq->next_rq 1937 * @drv_callback: function called between completion of bios in the request 1938 * and completion of the request. 1939 * If the callback returns non %0, this helper returns without 1940 * completion of the request. 1941 * 1942 * Description: 1943 * Ends I/O on a number of bytes attached to @rq and @rq->next_rq. 1944 * If @rq has leftover, sets it up for the next range of segments. 1945 * 1946 * Return: 1947 * %0 - we are done with this request 1948 * %1 - this request is not freed yet, it still has pending buffers. 1949 **/ 1950 static int blk_end_io(struct request *rq, int error, unsigned int nr_bytes, 1951 unsigned int bidi_bytes, 1952 int (drv_callback)(struct request *)) 1953 { 1954 struct request_queue *q = rq->q; 1955 unsigned long flags = 0UL; 1956 1957 if (end_that_request_data(rq, error, nr_bytes, bidi_bytes)) 1958 return 1; 1959 1960 /* Special feature for tricky drivers */ 1961 if (drv_callback && drv_callback(rq)) 1962 return 1; 1963 1964 add_disk_randomness(rq->rq_disk); 1965 1966 spin_lock_irqsave(q->queue_lock, flags); 1967 end_that_request_last(rq, error); 1968 spin_unlock_irqrestore(q->queue_lock, flags); 1969 1970 return 0; 1971 } 1972 1973 /** 1974 * blk_end_request - Helper function for drivers to complete the request. 1975 * @rq: the request being processed 1976 * @error: %0 for success, < %0 for error 1977 * @nr_bytes: number of bytes to complete 1978 * 1979 * Description: 1980 * Ends I/O on a number of bytes attached to @rq. 1981 * If @rq has leftover, sets it up for the next range of segments. 1982 * 1983 * Return: 1984 * %0 - we are done with this request 1985 * %1 - still buffers pending for this request 1986 **/ 1987 int blk_end_request(struct request *rq, int error, unsigned int nr_bytes) 1988 { 1989 return blk_end_io(rq, error, nr_bytes, 0, NULL); 1990 } 1991 EXPORT_SYMBOL_GPL(blk_end_request); 1992 1993 /** 1994 * __blk_end_request - Helper function for drivers to complete the request. 1995 * @rq: the request being processed 1996 * @error: %0 for success, < %0 for error 1997 * @nr_bytes: number of bytes to complete 1998 * 1999 * Description: 2000 * Must be called with queue lock held unlike blk_end_request(). 2001 * 2002 * Return: 2003 * %0 - we are done with this request 2004 * %1 - still buffers pending for this request 2005 **/ 2006 int __blk_end_request(struct request *rq, int error, unsigned int nr_bytes) 2007 { 2008 if (rq->bio && __end_that_request_first(rq, error, nr_bytes)) 2009 return 1; 2010 2011 add_disk_randomness(rq->rq_disk); 2012 2013 end_that_request_last(rq, error); 2014 2015 return 0; 2016 } 2017 EXPORT_SYMBOL_GPL(__blk_end_request); 2018 2019 /** 2020 * blk_end_bidi_request - Helper function for drivers to complete bidi request. 2021 * @rq: the bidi request being processed 2022 * @error: %0 for success, < %0 for error 2023 * @nr_bytes: number of bytes to complete @rq 2024 * @bidi_bytes: number of bytes to complete @rq->next_rq 2025 * 2026 * Description: 2027 * Ends I/O on a number of bytes attached to @rq and @rq->next_rq. 2028 * 2029 * Return: 2030 * %0 - we are done with this request 2031 * %1 - still buffers pending for this request 2032 **/ 2033 int blk_end_bidi_request(struct request *rq, int error, unsigned int nr_bytes, 2034 unsigned int bidi_bytes) 2035 { 2036 return blk_end_io(rq, error, nr_bytes, bidi_bytes, NULL); 2037 } 2038 EXPORT_SYMBOL_GPL(blk_end_bidi_request); 2039 2040 /** 2041 * blk_update_request - Special helper function for request stacking drivers 2042 * @rq: the request being processed 2043 * @error: %0 for success, < %0 for error 2044 * @nr_bytes: number of bytes to complete @rq 2045 * 2046 * Description: 2047 * Ends I/O on a number of bytes attached to @rq, but doesn't complete 2048 * the request structure even if @rq doesn't have leftover. 2049 * If @rq has leftover, sets it up for the next range of segments. 2050 * 2051 * This special helper function is only for request stacking drivers 2052 * (e.g. request-based dm) so that they can handle partial completion. 2053 * Actual device drivers should use blk_end_request instead. 2054 */ 2055 void blk_update_request(struct request *rq, int error, unsigned int nr_bytes) 2056 { 2057 if (!end_that_request_data(rq, error, nr_bytes, 0)) { 2058 /* 2059 * These members are not updated in end_that_request_data() 2060 * when all bios are completed. 2061 * Update them so that the request stacking driver can find 2062 * how many bytes remain in the request later. 2063 */ 2064 rq->nr_sectors = rq->hard_nr_sectors = 0; 2065 rq->current_nr_sectors = rq->hard_cur_sectors = 0; 2066 } 2067 } 2068 EXPORT_SYMBOL_GPL(blk_update_request); 2069 2070 /** 2071 * blk_end_request_callback - Special helper function for tricky drivers 2072 * @rq: the request being processed 2073 * @error: %0 for success, < %0 for error 2074 * @nr_bytes: number of bytes to complete 2075 * @drv_callback: function called between completion of bios in the request 2076 * and completion of the request. 2077 * If the callback returns non %0, this helper returns without 2078 * completion of the request. 2079 * 2080 * Description: 2081 * Ends I/O on a number of bytes attached to @rq. 2082 * If @rq has leftover, sets it up for the next range of segments. 2083 * 2084 * This special helper function is used only for existing tricky drivers. 2085 * (e.g. cdrom_newpc_intr() of ide-cd) 2086 * This interface will be removed when such drivers are rewritten. 2087 * Don't use this interface in other places anymore. 2088 * 2089 * Return: 2090 * %0 - we are done with this request 2091 * %1 - this request is not freed yet. 2092 * this request still has pending buffers or 2093 * the driver doesn't want to finish this request yet. 2094 **/ 2095 int blk_end_request_callback(struct request *rq, int error, 2096 unsigned int nr_bytes, 2097 int (drv_callback)(struct request *)) 2098 { 2099 return blk_end_io(rq, error, nr_bytes, 0, drv_callback); 2100 } 2101 EXPORT_SYMBOL_GPL(blk_end_request_callback); 2102 2103 void blk_rq_bio_prep(struct request_queue *q, struct request *rq, 2104 struct bio *bio) 2105 { 2106 /* Bit 0 (R/W) is identical in rq->cmd_flags and bio->bi_rw, and 2107 we want BIO_RW_AHEAD (bit 1) to imply REQ_FAILFAST (bit 1). */ 2108 rq->cmd_flags |= (bio->bi_rw & 3); 2109 2110 if (bio_has_data(bio)) { 2111 rq->nr_phys_segments = bio_phys_segments(q, bio); 2112 rq->buffer = bio_data(bio); 2113 } 2114 rq->current_nr_sectors = bio_cur_sectors(bio); 2115 rq->hard_cur_sectors = rq->current_nr_sectors; 2116 rq->hard_nr_sectors = rq->nr_sectors = bio_sectors(bio); 2117 rq->data_len = bio->bi_size; 2118 2119 rq->bio = rq->biotail = bio; 2120 2121 if (bio->bi_bdev) 2122 rq->rq_disk = bio->bi_bdev->bd_disk; 2123 } 2124 2125 /** 2126 * blk_lld_busy - Check if underlying low-level drivers of a device are busy 2127 * @q : the queue of the device being checked 2128 * 2129 * Description: 2130 * Check if underlying low-level drivers of a device are busy. 2131 * If the drivers want to export their busy state, they must set own 2132 * exporting function using blk_queue_lld_busy() first. 2133 * 2134 * Basically, this function is used only by request stacking drivers 2135 * to stop dispatching requests to underlying devices when underlying 2136 * devices are busy. This behavior helps more I/O merging on the queue 2137 * of the request stacking driver and prevents I/O throughput regression 2138 * on burst I/O load. 2139 * 2140 * Return: 2141 * 0 - Not busy (The request stacking driver should dispatch request) 2142 * 1 - Busy (The request stacking driver should stop dispatching request) 2143 */ 2144 int blk_lld_busy(struct request_queue *q) 2145 { 2146 if (q->lld_busy_fn) 2147 return q->lld_busy_fn(q); 2148 2149 return 0; 2150 } 2151 EXPORT_SYMBOL_GPL(blk_lld_busy); 2152 2153 int kblockd_schedule_work(struct request_queue *q, struct work_struct *work) 2154 { 2155 return queue_work(kblockd_workqueue, work); 2156 } 2157 EXPORT_SYMBOL(kblockd_schedule_work); 2158 2159 int __init blk_dev_init(void) 2160 { 2161 kblockd_workqueue = create_workqueue("kblockd"); 2162 if (!kblockd_workqueue) 2163 panic("Failed to create kblockd\n"); 2164 2165 request_cachep = kmem_cache_create("blkdev_requests", 2166 sizeof(struct request), 0, SLAB_PANIC, NULL); 2167 2168 blk_requestq_cachep = kmem_cache_create("blkdev_queue", 2169 sizeof(struct request_queue), 0, SLAB_PANIC, NULL); 2170 2171 return 0; 2172 } 2173 2174