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/fault-inject.h>
  30#include <linux/list_sort.h>
  31#include <linux/delay.h>
  32#include <linux/ratelimit.h>
 
 
 
 
 
 
 
  33
  34#define CREATE_TRACE_POINTS
  35#include <trace/events/block.h>
  36
  37#include "blk.h"
 
 
  38#include "blk-cgroup.h"
 
 
 
 
  39
  40EXPORT_TRACEPOINT_SYMBOL_GPL(block_bio_remap);
  41EXPORT_TRACEPOINT_SYMBOL_GPL(block_rq_remap);
  42EXPORT_TRACEPOINT_SYMBOL_GPL(block_bio_complete);
 
 
 
  43
  44DEFINE_IDA(blk_queue_ida);
  45
  46/*
  47 * For the allocated request tables
  48 */
  49static struct kmem_cache *request_cachep;
  50
  51/*
  52 * For queue allocation
  53 */
  54struct kmem_cache *blk_requestq_cachep;
  55
  56/*
  57 * Controlling structure to kblockd
  58 */
  59static struct workqueue_struct *kblockd_workqueue;
  60
  61static void drive_stat_acct(struct request *rq, int new_io)
 
 
 
 
 
  62{
  63	struct hd_struct *part;
  64	int rw = rq_data_dir(rq);
  65	int cpu;
  66
  67	if (!blk_do_io_stat(rq))
  68		return;
  69
  70	cpu = part_stat_lock();
  71
  72	if (!new_io) {
  73		part = rq->part;
  74		part_stat_inc(cpu, part, merges[rw]);
  75	} else {
  76		part = disk_map_sector_rcu(rq->rq_disk, blk_rq_pos(rq));
  77		if (!hd_struct_try_get(part)) {
  78			/*
  79			 * The partition is already being removed,
  80			 * the request will be accounted on the disk only
  81			 *
  82			 * We take a reference on disk->part0 although that
  83			 * partition will never be deleted, so we can treat
  84			 * it as any other partition.
  85			 */
  86			part = &rq->rq_disk->part0;
  87			hd_struct_get(part);
  88		}
  89		part_round_stats(cpu, part);
  90		part_inc_in_flight(part, rw);
  91		rq->part = part;
  92	}
  93
  94	part_stat_unlock();
  95}
 
  96
  97void blk_queue_congestion_threshold(struct request_queue *q)
 
 
 
 
 
  98{
  99	int nr;
 100
 101	nr = q->nr_requests - (q->nr_requests / 8) + 1;
 102	if (nr > q->nr_requests)
 103		nr = q->nr_requests;
 104	q->nr_congestion_on = nr;
 105
 106	nr = q->nr_requests - (q->nr_requests / 8) - (q->nr_requests / 16) - 1;
 107	if (nr < 1)
 108		nr = 1;
 109	q->nr_congestion_off = nr;
 110}
 
 111
 112/**
 113 * blk_get_backing_dev_info - get the address of a queue's backing_dev_info
 114 * @bdev:	device
 
 115 *
 116 * Locates the passed device's request queue and returns the address of its
 117 * backing_dev_info
 118 *
 119 * Will return NULL if the request queue cannot be located.
 120 */
 121struct backing_dev_info *blk_get_backing_dev_info(struct block_device *bdev)
 122{
 123	struct backing_dev_info *ret = NULL;
 124	struct request_queue *q = bdev_get_queue(bdev);
 125
 126	if (q)
 127		ret = &q->backing_dev_info;
 128	return ret;
 129}
 130EXPORT_SYMBOL(blk_get_backing_dev_info);
 131
 132void blk_rq_init(struct request_queue *q, struct request *rq)
 133{
 134	memset(rq, 0, sizeof(*rq));
 135
 136	INIT_LIST_HEAD(&rq->queuelist);
 137	INIT_LIST_HEAD(&rq->timeout_list);
 138	rq->cpu = -1;
 139	rq->q = q;
 140	rq->__sector = (sector_t) -1;
 141	INIT_HLIST_NODE(&rq->hash);
 142	RB_CLEAR_NODE(&rq->rb_node);
 143	rq->cmd = rq->__cmd;
 144	rq->cmd_len = BLK_MAX_CDB;
 145	rq->tag = -1;
 146	rq->ref_count = 1;
 147	rq->start_time = jiffies;
 148	set_start_time_ns(rq);
 149	rq->part = NULL;
 150}
 151EXPORT_SYMBOL(blk_rq_init);
 
 
 152
 153static void req_bio_endio(struct request *rq, struct bio *bio,
 154			  unsigned int nbytes, int error)
 
 
 
 
 
 
 
 155{
 156	if (error)
 157		clear_bit(BIO_UPTODATE, &bio->bi_flags);
 158	else if (!test_bit(BIO_UPTODATE, &bio->bi_flags))
 159		error = -EIO;
 160
 161	if (unlikely(nbytes > bio->bi_size)) {
 162		printk(KERN_ERR "%s: want %u bytes done, %u left\n",
 163		       __func__, nbytes, bio->bi_size);
 164		nbytes = bio->bi_size;
 165	}
 166
 167	if (unlikely(rq->cmd_flags & REQ_QUIET))
 168		set_bit(BIO_QUIET, &bio->bi_flags);
 169
 170	bio->bi_size -= nbytes;
 171	bio->bi_sector += (nbytes >> 9);
 172
 173	if (bio_integrity(bio))
 174		bio_integrity_advance(bio, nbytes);
 175
 176	/* don't actually finish bio if it's part of flush sequence */
 177	if (bio->bi_size == 0 && !(rq->cmd_flags & REQ_FLUSH_SEQ))
 178		bio_endio(bio, error);
 179}
 
 180
 181void blk_dump_rq_flags(struct request *rq, char *msg)
 182{
 183	int bit;
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 184
 185	printk(KERN_INFO "%s: dev %s: type=%x, flags=%x\n", msg,
 186		rq->rq_disk ? rq->rq_disk->disk_name : "?", rq->cmd_type,
 187		rq->cmd_flags);
 188
 189	printk(KERN_INFO "  sector %llu, nr/cnr %u/%u\n",
 190	       (unsigned long long)blk_rq_pos(rq),
 191	       blk_rq_sectors(rq), blk_rq_cur_sectors(rq));
 192	printk(KERN_INFO "  bio %p, biotail %p, buffer %p, len %u\n",
 193	       rq->bio, rq->biotail, rq->buffer, blk_rq_bytes(rq));
 194
 195	if (rq->cmd_type == REQ_TYPE_BLOCK_PC) {
 196		printk(KERN_INFO "  cdb: ");
 197		for (bit = 0; bit < BLK_MAX_CDB; bit++)
 198			printk("%02x ", rq->cmd[bit]);
 199		printk("\n");
 200	}
 201}
 202EXPORT_SYMBOL(blk_dump_rq_flags);
 203
 204static void blk_delay_work(struct work_struct *work)
 
 
 
 
 205{
 206	struct request_queue *q;
 207
 208	q = container_of(work, struct request_queue, delay_work.work);
 209	spin_lock_irq(q->queue_lock);
 210	__blk_run_queue(q);
 211	spin_unlock_irq(q->queue_lock);
 212}
 213
 214/**
 215 * blk_delay_queue - restart queueing after defined interval
 216 * @q:		The &struct request_queue in question
 217 * @msecs:	Delay in msecs
 218 *
 219 * Description:
 220 *   Sometimes queueing needs to be postponed for a little while, to allow
 221 *   resources to come back. This function will make sure that queueing is
 222 *   restarted around the specified time.
 223 */
 224void blk_delay_queue(struct request_queue *q, unsigned long msecs)
 225{
 226	queue_delayed_work(kblockd_workqueue, &q->delay_work,
 227				msecs_to_jiffies(msecs));
 228}
 229EXPORT_SYMBOL(blk_delay_queue);
 230
 231/**
 232 * blk_start_queue - restart a previously stopped queue
 233 * @q:    The &struct request_queue in question
 234 *
 235 * Description:
 236 *   blk_start_queue() will clear the stop flag on the queue, and call
 237 *   the request_fn for the queue if it was in a stopped state when
 238 *   entered. Also see blk_stop_queue(). Queue lock must be held.
 239 **/
 240void blk_start_queue(struct request_queue *q)
 241{
 242	WARN_ON(!irqs_disabled());
 243
 244	queue_flag_clear(QUEUE_FLAG_STOPPED, q);
 245	__blk_run_queue(q);
 
 246}
 247EXPORT_SYMBOL(blk_start_queue);
 248
 249/**
 250 * blk_stop_queue - stop a queue
 251 * @q:    The &struct request_queue in question
 252 *
 253 * Description:
 254 *   The Linux block layer assumes that a block driver will consume all
 255 *   entries on the request queue when the request_fn strategy is called.
 256 *   Often this will not happen, because of hardware limitations (queue
 257 *   depth settings). If a device driver gets a 'queue full' response,
 258 *   or if it simply chooses not to queue more I/O at one point, it can
 259 *   call this function to prevent the request_fn from being called until
 260 *   the driver has signalled it's ready to go again. This happens by calling
 261 *   blk_start_queue() to restart queue operations. Queue lock must be held.
 262 **/
 263void blk_stop_queue(struct request_queue *q)
 264{
 265	__cancel_delayed_work(&q->delay_work);
 266	queue_flag_set(QUEUE_FLAG_STOPPED, q);
 
 
 
 267}
 268EXPORT_SYMBOL(blk_stop_queue);
 269
 270/**
 271 * blk_sync_queue - cancel any pending callbacks on a queue
 272 * @q: the queue
 273 *
 274 * Description:
 275 *     The block layer may perform asynchronous callback activity
 276 *     on a queue, such as calling the unplug function after a timeout.
 277 *     A block device may call blk_sync_queue to ensure that any
 278 *     such activity is cancelled, thus allowing it to release resources
 279 *     that the callbacks might use. The caller must already have made sure
 280 *     that its ->make_request_fn will not re-add plugging prior to calling
 281 *     this function.
 282 *
 283 *     This function does not cancel any asynchronous activity arising
 284 *     out of elevator or throttling code. That would require elevaotor_exit()
 285 *     and blkcg_exit_queue() to be called with queue lock initialized.
 286 *
 287 */
 288void blk_sync_queue(struct request_queue *q)
 289{
 290	del_timer_sync(&q->timeout);
 291	cancel_delayed_work_sync(&q->delay_work);
 292}
 293EXPORT_SYMBOL(blk_sync_queue);
 294
 295/**
 296 * __blk_run_queue - run a single device queue
 297 * @q:	The queue to run
 298 *
 299 * Description:
 300 *    See @blk_run_queue. This variant must be called with the queue lock
 301 *    held and interrupts disabled.
 302 */
 303void __blk_run_queue(struct request_queue *q)
 304{
 305	if (unlikely(blk_queue_stopped(q)))
 306		return;
 
 
 
 
 
 307
 308	q->request_fn(q);
 
 
 
 309}
 310EXPORT_SYMBOL(__blk_run_queue);
 311
 312/**
 313 * blk_run_queue_async - run a single device queue in workqueue context
 314 * @q:	The queue to run
 315 *
 316 * Description:
 317 *    Tells kblockd to perform the equivalent of @blk_run_queue on behalf
 318 *    of us.
 319 */
 320void blk_run_queue_async(struct request_queue *q)
 321{
 322	if (likely(!blk_queue_stopped(q))) {
 323		__cancel_delayed_work(&q->delay_work);
 324		queue_delayed_work(kblockd_workqueue, &q->delay_work, 0);
 325	}
 
 326}
 327EXPORT_SYMBOL(blk_run_queue_async);
 328
 329/**
 330 * blk_run_queue - run a single device queue
 331 * @q: The queue to run
 332 *
 333 * Description:
 334 *    Invoke request handling on this queue, if it has pending work to do.
 335 *    May be used to restart queueing when a request has completed.
 336 */
 337void blk_run_queue(struct request_queue *q)
 338{
 339	unsigned long flags;
 
 
 340
 341	spin_lock_irqsave(q->queue_lock, flags);
 342	__blk_run_queue(q);
 343	spin_unlock_irqrestore(q->queue_lock, flags);
 344}
 345EXPORT_SYMBOL(blk_run_queue);
 346
 
 
 
 
 
 
 
 347void blk_put_queue(struct request_queue *q)
 348{
 349	kobject_put(&q->kobj);
 
 350}
 351EXPORT_SYMBOL(blk_put_queue);
 352
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 353/**
 354 * blk_drain_queue - drain requests from request_queue
 355 * @q: queue to drain
 356 * @drain_all: whether to drain all requests or only the ones w/ ELVPRIV
 357 *
 358 * Drain requests from @q.  If @drain_all is set, all requests are drained.
 359 * If not, only ELVPRIV requests are drained.  The caller is responsible
 360 * for ensuring that no new requests which need to be drained are queued.
 361 */
 362void blk_drain_queue(struct request_queue *q, bool drain_all)
 363{
 364	int i;
 365
 366	while (true) {
 367		bool drain = false;
 368
 369		spin_lock_irq(q->queue_lock);
 370
 371		/*
 372		 * The caller might be trying to drain @q before its
 373		 * elevator is initialized.
 
 
 
 374		 */
 375		if (q->elevator)
 376			elv_drain_elevator(q);
 
 
 
 
 
 
 377
 378		blkcg_drain_queue(q);
 
 379
 380		/*
 381		 * This function might be called on a queue which failed
 382		 * driver init after queue creation or is not yet fully
 383		 * active yet.  Some drivers (e.g. fd and loop) get unhappy
 384		 * in such cases.  Kick queue iff dispatch queue has
 385		 * something on it and @q has request_fn set.
 386		 */
 387		if (!list_empty(&q->queue_head) && q->request_fn)
 388			__blk_run_queue(q);
 389
 390		drain |= q->rq.elvpriv;
 
 
 
 
 
 391
 392		/*
 393		 * Unfortunately, requests are queued at and tracked from
 394		 * multiple places and there's no single counter which can
 395		 * be drained.  Check all the queues and counters.
 
 
 396		 */
 397		if (drain_all) {
 398			drain |= !list_empty(&q->queue_head);
 399			for (i = 0; i < 2; i++) {
 400				drain |= q->rq.count[i];
 401				drain |= q->in_flight[i];
 402				drain |= !list_empty(&q->flush_queue[i]);
 403			}
 404		}
 405
 406		spin_unlock_irq(q->queue_lock);
 407
 408		if (!drain)
 409			break;
 410		msleep(10);
 411	}
 412
 413	/*
 414	 * With queue marked dead, any woken up waiter will fail the
 415	 * allocation path, so the wakeup chaining is lost and we're
 416	 * left with hung waiters. We need to wake up those waiters.
 417	 */
 418	if (q->request_fn) {
 419		spin_lock_irq(q->queue_lock);
 420		for (i = 0; i < ARRAY_SIZE(q->rq.wait); i++)
 421			wake_up_all(&q->rq.wait[i]);
 422		spin_unlock_irq(q->queue_lock);
 423	}
 424}
 425
 426/**
 427 * blk_queue_bypass_start - enter queue bypass mode
 428 * @q: queue of interest
 429 *
 430 * In bypass mode, only the dispatch FIFO queue of @q is used.  This
 431 * function makes @q enter bypass mode and drains all requests which were
 432 * throttled or issued before.  On return, it's guaranteed that no request
 433 * is being throttled or has ELVPRIV set and blk_queue_bypass() %true
 434 * inside queue or RCU read lock.
 435 */
 436void blk_queue_bypass_start(struct request_queue *q)
 437{
 438	bool drain;
 439
 440	spin_lock_irq(q->queue_lock);
 441	drain = !q->bypass_depth++;
 442	queue_flag_set(QUEUE_FLAG_BYPASS, q);
 443	spin_unlock_irq(q->queue_lock);
 444
 445	if (drain) {
 446		blk_drain_queue(q, false);
 447		/* ensure blk_queue_bypass() is %true inside RCU read lock */
 448		synchronize_rcu();
 449	}
 450}
 451EXPORT_SYMBOL_GPL(blk_queue_bypass_start);
 452
 453/**
 454 * blk_queue_bypass_end - leave queue bypass mode
 455 * @q: queue of interest
 456 *
 457 * Leave bypass mode and restore the normal queueing behavior.
 458 */
 459void blk_queue_bypass_end(struct request_queue *q)
 460{
 461	spin_lock_irq(q->queue_lock);
 462	if (!--q->bypass_depth)
 463		queue_flag_clear(QUEUE_FLAG_BYPASS, q);
 464	WARN_ON_ONCE(q->bypass_depth < 0);
 465	spin_unlock_irq(q->queue_lock);
 466}
 467EXPORT_SYMBOL_GPL(blk_queue_bypass_end);
 468
 469/**
 470 * blk_cleanup_queue - shutdown a request queue
 471 * @q: request queue to shutdown
 472 *
 473 * Mark @q DEAD, drain all pending requests, destroy and put it.  All
 474 * future requests will be failed immediately with -ENODEV.
 475 */
 476void blk_cleanup_queue(struct request_queue *q)
 477{
 478	spinlock_t *lock = q->queue_lock;
 479
 480	/* mark @q DEAD, no new request or merges will be allowed afterwards */
 481	mutex_lock(&q->sysfs_lock);
 482	queue_flag_set_unlocked(QUEUE_FLAG_DEAD, q);
 483	spin_lock_irq(lock);
 484
 485	/*
 486	 * Dead queue is permanently in bypass mode till released.  Note
 487	 * that, unlike blk_queue_bypass_start(), we aren't performing
 488	 * synchronize_rcu() after entering bypass mode to avoid the delay
 489	 * as some drivers create and destroy a lot of queues while
 490	 * probing.  This is still safe because blk_release_queue() will be
 491	 * called only after the queue refcnt drops to zero and nothing,
 492	 * RCU or not, would be traversing the queue by then.
 493	 */
 494	q->bypass_depth++;
 495	queue_flag_set(QUEUE_FLAG_BYPASS, q);
 496
 497	queue_flag_set(QUEUE_FLAG_NOMERGES, q);
 498	queue_flag_set(QUEUE_FLAG_NOXMERGES, q);
 499	queue_flag_set(QUEUE_FLAG_DEAD, q);
 500	spin_unlock_irq(lock);
 501	mutex_unlock(&q->sysfs_lock);
 502
 503	/* drain all requests queued before DEAD marking */
 504	blk_drain_queue(q, true);
 505
 506	/* @q won't process any more request, flush async actions */
 507	del_timer_sync(&q->backing_dev_info.laptop_mode_wb_timer);
 508	blk_sync_queue(q);
 509
 510	spin_lock_irq(lock);
 511	if (q->queue_lock != &q->__queue_lock)
 512		q->queue_lock = &q->__queue_lock;
 513	spin_unlock_irq(lock);
 514
 515	/* @q is and will stay empty, shutdown and put */
 516	blk_put_queue(q);
 517}
 518EXPORT_SYMBOL(blk_cleanup_queue);
 519
 520static int blk_init_free_list(struct request_queue *q)
 521{
 522	struct request_list *rl = &q->rq;
 523
 524	if (unlikely(rl->rq_pool))
 525		return 0;
 526
 527	rl->count[BLK_RW_SYNC] = rl->count[BLK_RW_ASYNC] = 0;
 528	rl->starved[BLK_RW_SYNC] = rl->starved[BLK_RW_ASYNC] = 0;
 529	rl->elvpriv = 0;
 530	init_waitqueue_head(&rl->wait[BLK_RW_SYNC]);
 531	init_waitqueue_head(&rl->wait[BLK_RW_ASYNC]);
 532
 533	rl->rq_pool = mempool_create_node(BLKDEV_MIN_RQ, mempool_alloc_slab,
 534				mempool_free_slab, request_cachep, q->node);
 535
 536	if (!rl->rq_pool)
 537		return -ENOMEM;
 538
 539	return 0;
 540}
 541
 542struct request_queue *blk_alloc_queue(gfp_t gfp_mask)
 543{
 544	return blk_alloc_queue_node(gfp_mask, -1);
 545}
 546EXPORT_SYMBOL(blk_alloc_queue);
 547
 548struct request_queue *blk_alloc_queue_node(gfp_t gfp_mask, int node_id)
 549{
 550	struct request_queue *q;
 551	int err;
 552
 553	q = kmem_cache_alloc_node(blk_requestq_cachep,
 554				gfp_mask | __GFP_ZERO, node_id);
 555	if (!q)
 556		return NULL;
 
 
 557
 558	q->id = ida_simple_get(&blk_queue_ida, 0, 0, gfp_mask);
 559	if (q->id < 0)
 
 560		goto fail_q;
 
 
 
 
 
 
 
 
 
 
 
 
 561
 562	q->backing_dev_info.ra_pages =
 563			(VM_MAX_READAHEAD * 1024) / PAGE_CACHE_SIZE;
 564	q->backing_dev_info.state = 0;
 565	q->backing_dev_info.capabilities = BDI_CAP_MAP_COPY;
 566	q->backing_dev_info.name = "block";
 567	q->node = node_id;
 568
 569	err = bdi_init(&q->backing_dev_info);
 570	if (err)
 571		goto fail_id;
 572
 573	setup_timer(&q->backing_dev_info.laptop_mode_wb_timer,
 574		    laptop_mode_timer_fn, (unsigned long) q);
 575	setup_timer(&q->timeout, blk_rq_timed_out_timer, (unsigned long) q);
 576	INIT_LIST_HEAD(&q->queue_head);
 577	INIT_LIST_HEAD(&q->timeout_list);
 578	INIT_LIST_HEAD(&q->icq_list);
 579#ifdef CONFIG_BLK_CGROUP
 580	INIT_LIST_HEAD(&q->blkg_list);
 581#endif
 582	INIT_LIST_HEAD(&q->flush_queue[0]);
 583	INIT_LIST_HEAD(&q->flush_queue[1]);
 584	INIT_LIST_HEAD(&q->flush_data_in_flight);
 585	INIT_DELAYED_WORK(&q->delay_work, blk_delay_work);
 586
 587	kobject_init(&q->kobj, &blk_queue_ktype);
 588
 
 
 589	mutex_init(&q->sysfs_lock);
 590	spin_lock_init(&q->__queue_lock);
 
 
 
 591
 592	/*
 593	 * By default initialize queue_lock to internal lock and driver can
 594	 * override it later if need be.
 595	 */
 596	q->queue_lock = &q->__queue_lock;
 597
 598	/*
 599	 * A queue starts its life with bypass turned on to avoid
 600	 * unnecessary bypass on/off overhead and nasty surprises during
 601	 * init.  The initial bypass will be finished at the end of
 602	 * blk_init_allocated_queue().
 603	 */
 604	q->bypass_depth = 1;
 605	__set_bit(QUEUE_FLAG_BYPASS, &q->queue_flags);
 
 
 
 606
 607	if (blkcg_init_queue(q))
 608		goto fail_id;
 609
 610	return q;
 611
 
 
 612fail_id:
 613	ida_simple_remove(&blk_queue_ida, q->id);
 614fail_q:
 615	kmem_cache_free(blk_requestq_cachep, q);
 616	return NULL;
 617}
 618EXPORT_SYMBOL(blk_alloc_queue_node);
 619
 620/**
 621 * blk_init_queue  - prepare a request queue for use with a block device
 622 * @rfn:  The function to be called to process requests that have been
 623 *        placed on the queue.
 624 * @lock: Request queue spin lock
 625 *
 626 * Description:
 627 *    If a block device wishes to use the standard request handling procedures,
 628 *    which sorts requests and coalesces adjacent requests, then it must
 629 *    call blk_init_queue().  The function @rfn will be called when there
 630 *    are requests on the queue that need to be processed.  If the device
 631 *    supports plugging, then @rfn may not be called immediately when requests
 632 *    are available on the queue, but may be called at some time later instead.
 633 *    Plugged queues are generally unplugged when a buffer belonging to one
 634 *    of the requests on the queue is needed, or due to memory pressure.
 635 *
 636 *    @rfn is not required, or even expected, to remove all requests off the
 637 *    queue, but only as many as it can handle at a time.  If it does leave
 638 *    requests on the queue, it is responsible for arranging that the requests
 639 *    get dealt with eventually.
 640 *
 641 *    The queue spin lock must be held while manipulating the requests on the
 642 *    request queue; this lock will be taken also from interrupt context, so irq
 643 *    disabling is needed for it.
 644 *
 645 *    Function returns a pointer to the initialized request queue, or %NULL if
 646 *    it didn't succeed.
 647 *
 648 * Note:
 649 *    blk_init_queue() must be paired with a blk_cleanup_queue() call
 650 *    when the block device is deactivated (such as at module unload).
 651 **/
 652
 653struct request_queue *blk_init_queue(request_fn_proc *rfn, spinlock_t *lock)
 654{
 655	return blk_init_queue_node(rfn, lock, -1);
 656}
 657EXPORT_SYMBOL(blk_init_queue);
 658
 659struct request_queue *
 660blk_init_queue_node(request_fn_proc *rfn, spinlock_t *lock, int node_id)
 661{
 662	struct request_queue *uninit_q, *q;
 663
 664	uninit_q = blk_alloc_queue_node(GFP_KERNEL, node_id);
 665	if (!uninit_q)
 666		return NULL;
 667
 668	q = blk_init_allocated_queue(uninit_q, rfn, lock);
 669	if (!q)
 670		blk_cleanup_queue(uninit_q);
 671
 672	return q;
 673}
 674EXPORT_SYMBOL(blk_init_queue_node);
 675
 676struct request_queue *
 677blk_init_allocated_queue(struct request_queue *q, request_fn_proc *rfn,
 678			 spinlock_t *lock)
 679{
 680	if (!q)
 681		return NULL;
 682
 683	if (blk_init_free_list(q))
 684		return NULL;
 685
 686	q->request_fn		= rfn;
 687	q->prep_rq_fn		= NULL;
 688	q->unprep_rq_fn		= NULL;
 689	q->queue_flags		= QUEUE_FLAG_DEFAULT;
 690
 691	/* Override internal queue lock with supplied lock pointer */
 692	if (lock)
 693		q->queue_lock		= lock;
 694
 695	/*
 696	 * This also sets hw/phys segments, boundary and size
 697	 */
 698	blk_queue_make_request(q, blk_queue_bio);
 699
 700	q->sg_reserved_size = INT_MAX;
 701
 702	/* init elevator */
 703	if (elevator_init(q, NULL))
 704		return NULL;
 705
 706	blk_queue_congestion_threshold(q);
 707
 708	/* all done, end the initial bypass */
 709	blk_queue_bypass_end(q);
 710	return q;
 711}
 712EXPORT_SYMBOL(blk_init_allocated_queue);
 713
 714bool blk_get_queue(struct request_queue *q)
 715{
 716	if (likely(!blk_queue_dead(q))) {
 717		__blk_get_queue(q);
 718		return true;
 719	}
 720
 721	return false;
 722}
 723EXPORT_SYMBOL(blk_get_queue);
 724
 725static inline void blk_free_request(struct request_queue *q, struct request *rq)
 726{
 727	if (rq->cmd_flags & REQ_ELVPRIV) {
 728		elv_put_request(q, rq);
 729		if (rq->elv.icq)
 730			put_io_context(rq->elv.icq->ioc);
 731	}
 732
 733	mempool_free(rq, q->rq.rq_pool);
 734}
 735
 736/*
 737 * ioc_batching returns true if the ioc is a valid batching request and
 738 * should be given priority access to a request.
 739 */
 740static inline int ioc_batching(struct request_queue *q, struct io_context *ioc)
 741{
 742	if (!ioc)
 743		return 0;
 744
 745	/*
 746	 * Make sure the process is able to allocate at least 1 request
 747	 * even if the batch times out, otherwise we could theoretically
 748	 * lose wakeups.
 749	 */
 750	return ioc->nr_batch_requests == q->nr_batching ||
 751		(ioc->nr_batch_requests > 0
 752		&& time_before(jiffies, ioc->last_waited + BLK_BATCH_TIME));
 753}
 754
 755/*
 756 * ioc_set_batching sets ioc to be a new "batcher" if it is not one. This
 757 * will cause the process to be a "batcher" on all queues in the system. This
 758 * is the behaviour we want though - once it gets a wakeup it should be given
 759 * a nice run.
 760 */
 761static void ioc_set_batching(struct request_queue *q, struct io_context *ioc)
 762{
 763	if (!ioc || ioc_batching(q, ioc))
 764		return;
 765
 766	ioc->nr_batch_requests = q->nr_batching;
 767	ioc->last_waited = jiffies;
 768}
 769
 770static void __freed_request(struct request_queue *q, int sync)
 771{
 772	struct request_list *rl = &q->rq;
 773
 774	if (rl->count[sync] < queue_congestion_off_threshold(q))
 775		blk_clear_queue_congested(q, sync);
 776
 777	if (rl->count[sync] + 1 <= q->nr_requests) {
 778		if (waitqueue_active(&rl->wait[sync]))
 779			wake_up(&rl->wait[sync]);
 780
 781		blk_clear_queue_full(q, sync);
 782	}
 783}
 
 784
 785/*
 786 * A request has just been released.  Account for it, update the full and
 787 * congestion status, wake up any waiters.   Called under q->queue_lock.
 788 */
 789static void freed_request(struct request_queue *q, unsigned int flags)
 790{
 791	struct request_list *rl = &q->rq;
 792	int sync = rw_is_sync(flags);
 793
 794	rl->count[sync]--;
 795	if (flags & REQ_ELVPRIV)
 796		rl->elvpriv--;
 797
 798	__freed_request(q, sync);
 799
 800	if (unlikely(rl->starved[sync ^ 1]))
 801		__freed_request(q, sync ^ 1);
 802}
 803
 804/*
 805 * Determine if elevator data should be initialized when allocating the
 806 * request associated with @bio.
 807 */
 808static bool blk_rq_should_init_elevator(struct bio *bio)
 809{
 810	if (!bio)
 811		return true;
 812
 813	/*
 814	 * Flush requests do not use the elevator so skip initialization.
 815	 * This allows a request to share the flush and elevator data.
 816	 */
 817	if (bio->bi_rw & (REQ_FLUSH | REQ_FUA))
 818		return false;
 819
 820	return true;
 821}
 822
 823/**
 824 * rq_ioc - determine io_context for request allocation
 825 * @bio: request being allocated is for this bio (can be %NULL)
 826 *
 827 * Determine io_context to use for request allocation for @bio.  May return
 828 * %NULL if %current->io_context doesn't exist.
 829 */
 830static struct io_context *rq_ioc(struct bio *bio)
 831{
 832#ifdef CONFIG_BLK_CGROUP
 833	if (bio && bio->bi_ioc)
 834		return bio->bi_ioc;
 835#endif
 836	return current->io_context;
 837}
 838
 839/**
 840 * get_request - get a free request
 841 * @q: request_queue to allocate request from
 842 * @rw_flags: RW and SYNC flags
 843 * @bio: bio to allocate request for (can be %NULL)
 844 * @gfp_mask: allocation mask
 845 *
 846 * Get a free request from @q.  This function may fail under memory
 847 * pressure or if @q is dead.
 848 *
 849 * Must be callled with @q->queue_lock held and,
 850 * Returns %NULL on failure, with @q->queue_lock held.
 851 * Returns !%NULL on success, with @q->queue_lock *not held*.
 852 */
 853static struct request *get_request(struct request_queue *q, int rw_flags,
 854				   struct bio *bio, gfp_t gfp_mask)
 855{
 856	struct request *rq;
 857	struct request_list *rl = &q->rq;
 858	struct elevator_type *et;
 859	struct io_context *ioc;
 860	struct io_cq *icq = NULL;
 861	const bool is_sync = rw_is_sync(rw_flags) != 0;
 862	bool retried = false;
 863	int may_queue;
 864retry:
 865	et = q->elevator->type;
 866	ioc = rq_ioc(bio);
 867
 868	if (unlikely(blk_queue_dead(q)))
 869		return NULL;
 870
 871	may_queue = elv_may_queue(q, rw_flags);
 872	if (may_queue == ELV_MQUEUE_NO)
 873		goto rq_starved;
 874
 875	if (rl->count[is_sync]+1 >= queue_congestion_on_threshold(q)) {
 876		if (rl->count[is_sync]+1 >= q->nr_requests) {
 877			/*
 878			 * We want ioc to record batching state.  If it's
 879			 * not already there, creating a new one requires
 880			 * dropping queue_lock, which in turn requires
 881			 * retesting conditions to avoid queue hang.
 882			 */
 883			if (!ioc && !retried) {
 884				spin_unlock_irq(q->queue_lock);
 885				create_io_context(gfp_mask, q->node);
 886				spin_lock_irq(q->queue_lock);
 887				retried = true;
 888				goto retry;
 889			}
 890
 891			/*
 892			 * The queue will fill after this allocation, so set
 893			 * it as full, and mark this process as "batching".
 894			 * This process will be allowed to complete a batch of
 895			 * requests, others will be blocked.
 896			 */
 897			if (!blk_queue_full(q, is_sync)) {
 898				ioc_set_batching(q, ioc);
 899				blk_set_queue_full(q, is_sync);
 900			} else {
 901				if (may_queue != ELV_MQUEUE_MUST
 902						&& !ioc_batching(q, ioc)) {
 903					/*
 904					 * The queue is full and the allocating
 905					 * process is not a "batcher", and not
 906					 * exempted by the IO scheduler
 907					 */
 908					return NULL;
 909				}
 910			}
 911		}
 912		blk_set_queue_congested(q, is_sync);
 913	}
 914
 915	/*
 916	 * Only allow batching queuers to allocate up to 50% over the defined
 917	 * limit of requests, otherwise we could have thousands of requests
 918	 * allocated with any setting of ->nr_requests
 919	 */
 920	if (rl->count[is_sync] >= (3 * q->nr_requests / 2))
 921		return NULL;
 922
 923	rl->count[is_sync]++;
 924	rl->starved[is_sync] = 0;
 925
 926	/*
 927	 * Decide whether the new request will be managed by elevator.  If
 928	 * so, mark @rw_flags and increment elvpriv.  Non-zero elvpriv will
 929	 * prevent the current elevator from being destroyed until the new
 930	 * request is freed.  This guarantees icq's won't be destroyed and
 931	 * makes creating new ones safe.
 932	 *
 933	 * Also, lookup icq while holding queue_lock.  If it doesn't exist,
 934	 * it will be created after releasing queue_lock.
 935	 */
 936	if (blk_rq_should_init_elevator(bio) && !blk_queue_bypass(q)) {
 937		rw_flags |= REQ_ELVPRIV;
 938		rl->elvpriv++;
 939		if (et->icq_cache && ioc)
 940			icq = ioc_lookup_icq(ioc, q);
 941	}
 942
 943	if (blk_queue_io_stat(q))
 944		rw_flags |= REQ_IO_STAT;
 945	spin_unlock_irq(q->queue_lock);
 946
 947	/* allocate and init request */
 948	rq = mempool_alloc(q->rq.rq_pool, gfp_mask);
 949	if (!rq)
 950		goto fail_alloc;
 951
 952	blk_rq_init(q, rq);
 953	rq->cmd_flags = rw_flags | REQ_ALLOCED;
 954
 955	/* init elvpriv */
 956	if (rw_flags & REQ_ELVPRIV) {
 957		if (unlikely(et->icq_cache && !icq)) {
 958			create_io_context(gfp_mask, q->node);
 959			ioc = rq_ioc(bio);
 960			if (!ioc)
 961				goto fail_elvpriv;
 962
 963			icq = ioc_create_icq(ioc, q, gfp_mask);
 964			if (!icq)
 965				goto fail_elvpriv;
 966		}
 967
 968		rq->elv.icq = icq;
 969		if (unlikely(elv_set_request(q, rq, bio, gfp_mask)))
 970			goto fail_elvpriv;
 971
 972		/* @rq->elv.icq holds io_context until @rq is freed */
 973		if (icq)
 974			get_io_context(icq->ioc);
 975	}
 976out:
 977	/*
 978	 * ioc may be NULL here, and ioc_batching will be false. That's
 979	 * OK, if the queue is under the request limit then requests need
 980	 * not count toward the nr_batch_requests limit. There will always
 981	 * be some limit enforced by BLK_BATCH_TIME.
 982	 */
 983	if (ioc_batching(q, ioc))
 984		ioc->nr_batch_requests--;
 985
 986	trace_block_getrq(q, bio, rw_flags & 1);
 987	return rq;
 988
 989fail_elvpriv:
 990	/*
 991	 * elvpriv init failed.  ioc, icq and elvpriv aren't mempool backed
 992	 * and may fail indefinitely under memory pressure and thus
 993	 * shouldn't stall IO.  Treat this request as !elvpriv.  This will
 994	 * disturb iosched and blkcg but weird is bettern than dead.
 995	 */
 996	printk_ratelimited(KERN_WARNING "%s: request aux data allocation failed, iosched may be disturbed\n",
 997			   dev_name(q->backing_dev_info.dev));
 998
 999	rq->cmd_flags &= ~REQ_ELVPRIV;
1000	rq->elv.icq = NULL;
1001
1002	spin_lock_irq(q->queue_lock);
1003	rl->elvpriv--;
1004	spin_unlock_irq(q->queue_lock);
1005	goto out;
1006
1007fail_alloc:
1008	/*
1009	 * Allocation failed presumably due to memory. Undo anything we
1010	 * might have messed up.
1011	 *
1012	 * Allocating task should really be put onto the front of the wait
1013	 * queue, but this is pretty rare.
1014	 */
1015	spin_lock_irq(q->queue_lock);
1016	freed_request(q, rw_flags);
1017
1018	/*
1019	 * in the very unlikely event that allocation failed and no
1020	 * requests for this direction was pending, mark us starved so that
1021	 * freeing of a request in the other direction will notice
1022	 * us. another possible fix would be to split the rq mempool into
1023	 * READ and WRITE
1024	 */
1025rq_starved:
1026	if (unlikely(rl->count[is_sync] == 0))
1027		rl->starved[is_sync] = 1;
1028	return NULL;
1029}
1030
1031/**
1032 * get_request_wait - get a free request with retry
1033 * @q: request_queue to allocate request from
1034 * @rw_flags: RW and SYNC flags
1035 * @bio: bio to allocate request for (can be %NULL)
1036 *
1037 * Get a free request from @q.  This function keeps retrying under memory
1038 * pressure and fails iff @q is dead.
1039 *
1040 * Must be callled with @q->queue_lock held and,
1041 * Returns %NULL on failure, with @q->queue_lock held.
1042 * Returns !%NULL on success, with @q->queue_lock *not held*.
1043 */
1044static struct request *get_request_wait(struct request_queue *q, int rw_flags,
1045					struct bio *bio)
1046{
1047	const bool is_sync = rw_is_sync(rw_flags) != 0;
1048	struct request *rq;
1049
1050	rq = get_request(q, rw_flags, bio, GFP_NOIO);
1051	while (!rq) {
1052		DEFINE_WAIT(wait);
1053		struct request_list *rl = &q->rq;
1054
1055		if (unlikely(blk_queue_dead(q)))
1056			return NULL;
1057
1058		prepare_to_wait_exclusive(&rl->wait[is_sync], &wait,
1059				TASK_UNINTERRUPTIBLE);
1060
1061		trace_block_sleeprq(q, bio, rw_flags & 1);
1062
1063		spin_unlock_irq(q->queue_lock);
1064		io_schedule();
1065
 
1066		/*
1067		 * After sleeping, we become a "batching" process and
1068		 * will be able to allocate at least one request, and
1069		 * up to a big batch of them for a small period time.
1070		 * See ioc_batching, ioc_set_batching
1071		 */
1072		create_io_context(GFP_NOIO, q->node);
1073		ioc_set_batching(q, current->io_context);
1074
1075		spin_lock_irq(q->queue_lock);
1076		finish_wait(&rl->wait[is_sync], &wait);
1077
1078		rq = get_request(q, rw_flags, bio, GFP_NOIO);
1079	};
1080
1081	return rq;
1082}
1083
1084struct request *blk_get_request(struct request_queue *q, int rw, gfp_t gfp_mask)
1085{
1086	struct request *rq;
1087
1088	BUG_ON(rw != READ && rw != WRITE);
1089
1090	spin_lock_irq(q->queue_lock);
1091	if (gfp_mask & __GFP_WAIT)
1092		rq = get_request_wait(q, rw, NULL);
1093	else
1094		rq = get_request(q, rw, NULL, gfp_mask);
1095	if (!rq)
1096		spin_unlock_irq(q->queue_lock);
1097	/* q->queue_lock is unlocked at this point */
1098
1099	return rq;
1100}
1101EXPORT_SYMBOL(blk_get_request);
1102
1103/**
1104 * blk_make_request - given a bio, allocate a corresponding struct request.
1105 * @q: target request queue
1106 * @bio:  The bio describing the memory mappings that will be submitted for IO.
1107 *        It may be a chained-bio properly constructed by block/bio layer.
1108 * @gfp_mask: gfp flags to be used for memory allocation
1109 *
1110 * blk_make_request is the parallel of generic_make_request for BLOCK_PC
1111 * type commands. Where the struct request needs to be farther initialized by
1112 * the caller. It is passed a &struct bio, which describes the memory info of
1113 * the I/O transfer.
1114 *
1115 * The caller of blk_make_request must make sure that bi_io_vec
1116 * are set to describe the memory buffers. That bio_data_dir() will return
1117 * the needed direction of the request. (And all bio's in the passed bio-chain
1118 * are properly set accordingly)
1119 *
1120 * If called under none-sleepable conditions, mapped bio buffers must not
1121 * need bouncing, by calling the appropriate masked or flagged allocator,
1122 * suitable for the target device. Otherwise the call to blk_queue_bounce will
1123 * BUG.
1124 *
1125 * WARNING: When allocating/cloning a bio-chain, careful consideration should be
1126 * given to how you allocate bios. In particular, you cannot use __GFP_WAIT for
1127 * anything but the first bio in the chain. Otherwise you risk waiting for IO
1128 * completion of a bio that hasn't been submitted yet, thus resulting in a
1129 * deadlock. Alternatively bios should be allocated using bio_kmalloc() instead
1130 * of bio_alloc(), as that avoids the mempool deadlock.
1131 * If possible a big IO should be split into smaller parts when allocation
1132 * fails. Partial allocation should not be an error, or you risk a live-lock.
1133 */
1134struct request *blk_make_request(struct request_queue *q, struct bio *bio,
1135				 gfp_t gfp_mask)
1136{
1137	struct request *rq = blk_get_request(q, bio_data_dir(bio), gfp_mask);
1138
1139	if (unlikely(!rq))
1140		return ERR_PTR(-ENOMEM);
1141
1142	for_each_bio(bio) {
1143		struct bio *bounce_bio = bio;
1144		int ret;
1145
1146		blk_queue_bounce(q, &bounce_bio);
1147		ret = blk_rq_append_bio(q, rq, bounce_bio);
1148		if (unlikely(ret)) {
1149			blk_put_request(rq);
1150			return ERR_PTR(ret);
1151		}
1152	}
1153
1154	return rq;
1155}
1156EXPORT_SYMBOL(blk_make_request);
1157
1158/**
1159 * blk_requeue_request - put a request back on queue
1160 * @q:		request queue where request should be inserted
1161 * @rq:		request to be inserted
1162 *
1163 * Description:
1164 *    Drivers often keep queueing requests until the hardware cannot accept
1165 *    more, when that condition happens we need to put the request back
1166 *    on the queue. Must be called with queue lock held.
1167 */
1168void blk_requeue_request(struct request_queue *q, struct request *rq)
1169{
1170	blk_delete_timer(rq);
1171	blk_clear_rq_complete(rq);
1172	trace_block_rq_requeue(q, rq);
1173
1174	if (blk_rq_tagged(rq))
1175		blk_queue_end_tag(q, rq);
1176
1177	BUG_ON(blk_queued_rq(rq));
1178
1179	elv_requeue_request(q, rq);
1180}
1181EXPORT_SYMBOL(blk_requeue_request);
1182
1183static void add_acct_request(struct request_queue *q, struct request *rq,
1184			     int where)
1185{
1186	drive_stat_acct(rq, 1);
1187	__elv_add_request(q, rq, where);
 
1188}
 
1189
1190static void part_round_stats_single(int cpu, struct hd_struct *part,
1191				    unsigned long now)
1192{
1193	if (now == part->stamp)
1194		return;
1195
1196	if (part_in_flight(part)) {
1197		__part_stat_add(cpu, part, time_in_queue,
1198				part_in_flight(part) * (now - part->stamp));
1199		__part_stat_add(cpu, part, io_ticks, (now - part->stamp));
 
 
 
 
 
 
 
 
1200	}
1201	part->stamp = now;
1202}
1203
1204/**
1205 * part_round_stats() - Round off the performance stats on a struct disk_stats.
1206 * @cpu: cpu number for stats access
1207 * @part: target partition
1208 *
1209 * The average IO queue length and utilisation statistics are maintained
1210 * by observing the current state of the queue length and the amount of
1211 * time it has been in this state for.
1212 *
1213 * Normally, that accounting is done on IO completion, but that can result
1214 * in more than a second's worth of IO being accounted for within any one
1215 * second, leading to >100% utilisation.  To deal with that, we call this
1216 * function to do a round-off before returning the results when reading
1217 * /proc/diskstats.  This accounts immediately for all queue usage up to
1218 * the current jiffies and restarts the counters again.
1219 */
1220void part_round_stats(int cpu, struct hd_struct *part)
1221{
1222	unsigned long now = jiffies;
1223
1224	if (part->partno)
1225		part_round_stats_single(cpu, &part_to_disk(part)->part0, now);
1226	part_round_stats_single(cpu, part, now);
1227}
1228EXPORT_SYMBOL_GPL(part_round_stats);
1229
1230/*
1231 * queue lock must be held
1232 */
1233void __blk_put_request(struct request_queue *q, struct request *req)
1234{
1235	if (unlikely(!q))
1236		return;
1237	if (unlikely(--req->ref_count))
1238		return;
1239
1240	elv_completed_request(q, req);
1241
1242	/* this is a bio leak */
1243	WARN_ON(req->bio != NULL);
1244
1245	/*
1246	 * Request may not have originated from ll_rw_blk. if not,
1247	 * it didn't come out of our reserved rq pools
1248	 */
1249	if (req->cmd_flags & REQ_ALLOCED) {
1250		unsigned int flags = req->cmd_flags;
1251
1252		BUG_ON(!list_empty(&req->queuelist));
1253		BUG_ON(!hlist_unhashed(&req->hash));
1254
1255		blk_free_request(q, req);
1256		freed_request(q, flags);
1257	}
 
 
1258}
1259EXPORT_SYMBOL_GPL(__blk_put_request);
1260
1261void blk_put_request(struct request *req)
1262{
1263	unsigned long flags;
1264	struct request_queue *q = req->q;
1265
1266	spin_lock_irqsave(q->queue_lock, flags);
1267	__blk_put_request(q, req);
1268	spin_unlock_irqrestore(q->queue_lock, flags);
1269}
1270EXPORT_SYMBOL(blk_put_request);
1271
1272/**
1273 * blk_add_request_payload - add a payload to a request
1274 * @rq: request to update
1275 * @page: page backing the payload
1276 * @len: length of the payload.
1277 *
1278 * This allows to later add a payload to an already submitted request by
1279 * a block driver.  The driver needs to take care of freeing the payload
1280 * itself.
1281 *
1282 * Note that this is a quite horrible hack and nothing but handling of
1283 * discard requests should ever use it.
1284 */
1285void blk_add_request_payload(struct request *rq, struct page *page,
1286		unsigned int len)
1287{
1288	struct bio *bio = rq->bio;
1289
1290	bio->bi_io_vec->bv_page = page;
1291	bio->bi_io_vec->bv_offset = 0;
1292	bio->bi_io_vec->bv_len = len;
1293
1294	bio->bi_size = len;
1295	bio->bi_vcnt = 1;
1296	bio->bi_phys_segments = 1;
1297
1298	rq->__data_len = rq->resid_len = len;
1299	rq->nr_phys_segments = 1;
1300	rq->buffer = bio_data(bio);
1301}
1302EXPORT_SYMBOL_GPL(blk_add_request_payload);
1303
1304static bool bio_attempt_back_merge(struct request_queue *q, struct request *req,
1305				   struct bio *bio)
1306{
1307	const int ff = bio->bi_rw & REQ_FAILFAST_MASK;
1308
1309	if (!ll_back_merge_fn(q, req, bio))
1310		return false;
1311
1312	trace_block_bio_backmerge(q, bio);
1313
1314	if ((req->cmd_flags & REQ_FAILFAST_MASK) != ff)
1315		blk_rq_set_mixed_merge(req);
1316
1317	req->biotail->bi_next = bio;
1318	req->biotail = bio;
1319	req->__data_len += bio->bi_size;
1320	req->ioprio = ioprio_best(req->ioprio, bio_prio(bio));
1321
1322	drive_stat_acct(req, 0);
1323	return true;
1324}
1325
1326static bool bio_attempt_front_merge(struct request_queue *q,
1327				    struct request *req, struct bio *bio)
1328{
1329	const int ff = bio->bi_rw & REQ_FAILFAST_MASK;
1330
1331	if (!ll_front_merge_fn(q, req, bio))
1332		return false;
1333
1334	trace_block_bio_frontmerge(q, bio);
1335
1336	if ((req->cmd_flags & REQ_FAILFAST_MASK) != ff)
1337		blk_rq_set_mixed_merge(req);
 
1338
1339	bio->bi_next = req->bio;
1340	req->bio = bio;
 
 
1341
1342	/*
1343	 * may not be valid. if the low level driver said
1344	 * it didn't need a bounce buffer then it better
1345	 * not touch req->buffer either...
1346	 */
1347	req->buffer = bio_data(bio);
1348	req->__sector = bio->bi_sector;
1349	req->__data_len += bio->bi_size;
1350	req->ioprio = ioprio_best(req->ioprio, bio_prio(bio));
1351
1352	drive_stat_acct(req, 0);
1353	return true;
1354}
1355
1356/**
1357 * attempt_plug_merge - try to merge with %current's plugged list
1358 * @q: request_queue new bio is being queued at
1359 * @bio: new bio being queued
1360 * @request_count: out parameter for number of traversed plugged requests
1361 *
1362 * Determine whether @bio being queued on @q can be merged with a request
1363 * on %current's plugged list.  Returns %true if merge was successful,
1364 * otherwise %false.
1365 *
1366 * Plugging coalesces IOs from the same issuer for the same purpose without
1367 * going through @q->queue_lock.  As such it's more of an issuing mechanism
1368 * than scheduling, and the request, while may have elvpriv data, is not
1369 * added on the elevator at this point.  In addition, we don't have
1370 * reliable access to the elevator outside queue lock.  Only check basic
1371 * merging parameters without querying the elevator.
1372 */
1373static bool attempt_plug_merge(struct request_queue *q, struct bio *bio,
1374			       unsigned int *request_count)
1375{
1376	struct blk_plug *plug;
1377	struct request *rq;
1378	bool ret = false;
1379
1380	plug = current->plug;
1381	if (!plug)
1382		goto out;
1383	*request_count = 0;
1384
1385	list_for_each_entry_reverse(rq, &plug->list, queuelist) {
1386		int el_ret;
1387
1388		if (rq->q == q)
1389			(*request_count)++;
1390
1391		if (rq->q != q || !blk_rq_merge_ok(rq, bio))
1392			continue;
1393
1394		el_ret = blk_try_merge(rq, bio);
1395		if (el_ret == ELEVATOR_BACK_MERGE) {
1396			ret = bio_attempt_back_merge(q, rq, bio);
1397			if (ret)
1398				break;
1399		} else if (el_ret == ELEVATOR_FRONT_MERGE) {
1400			ret = bio_attempt_front_merge(q, rq, bio);
1401			if (ret)
1402				break;
1403		}
1404	}
1405out:
1406	return ret;
1407}
1408
1409void init_request_from_bio(struct request *req, struct bio *bio)
1410{
1411	req->cmd_type = REQ_TYPE_FS;
1412
1413	req->cmd_flags |= bio->bi_rw & REQ_COMMON_MASK;
1414	if (bio->bi_rw & REQ_RAHEAD)
1415		req->cmd_flags |= REQ_FAILFAST_MASK;
1416
1417	req->errors = 0;
1418	req->__sector = bio->bi_sector;
1419	req->ioprio = bio_prio(bio);
1420	blk_rq_bio_prep(req->q, req, bio);
1421}
1422
1423void blk_queue_bio(struct request_queue *q, struct bio *bio)
1424{
1425	const bool sync = !!(bio->bi_rw & REQ_SYNC);
1426	struct blk_plug *plug;
1427	int el_ret, rw_flags, where = ELEVATOR_INSERT_SORT;
1428	struct request *req;
1429	unsigned int request_count = 0;
1430
1431	/*
1432	 * low level driver can indicate that it wants pages above a
1433	 * certain limit bounced to low memory (ie for highmem, or even
1434	 * ISA dma in theory)
1435	 */
1436	blk_queue_bounce(q, &bio);
1437
1438	if (bio->bi_rw & (REQ_FLUSH | REQ_FUA)) {
1439		spin_lock_irq(q->queue_lock);
1440		where = ELEVATOR_INSERT_FLUSH;
1441		goto get_rq;
1442	}
1443
1444	/*
1445	 * Check if we can merge with the plugged list before grabbing
1446	 * any locks.
1447	 */
1448	if (attempt_plug_merge(q, bio, &request_count))
1449		return;
1450
1451	spin_lock_irq(q->queue_lock);
 
 
 
1452
1453	el_ret = elv_merge(q, &req, bio);
1454	if (el_ret == ELEVATOR_BACK_MERGE) {
1455		if (bio_attempt_back_merge(q, req, bio)) {
1456			elv_bio_merged(q, req, bio);
1457			if (!attempt_back_merge(q, req))
1458				elv_merged_request(q, req, el_ret);
1459			goto out_unlock;
1460		}
1461	} else if (el_ret == ELEVATOR_FRONT_MERGE) {
1462		if (bio_attempt_front_merge(q, req, bio)) {
1463			elv_bio_merged(q, req, bio);
1464			if (!attempt_front_merge(q, req))
1465				elv_merged_request(q, req, el_ret);
1466			goto out_unlock;
1467		}
1468	}
1469
1470get_rq:
1471	/*
1472	 * This sync check and mask will be re-done in init_request_from_bio(),
1473	 * but we need to set it earlier to expose the sync flag to the
1474	 * rq allocator and io schedulers.
1475	 */
1476	rw_flags = bio_data_dir(bio);
1477	if (sync)
1478		rw_flags |= REQ_SYNC;
1479
1480	/*
1481	 * Grab a free request. This is might sleep but can not fail.
1482	 * Returns with the queue unlocked.
1483	 */
1484	req = get_request_wait(q, rw_flags, bio);
1485	if (unlikely(!req)) {
1486		bio_endio(bio, -ENODEV);	/* @q is dead */
1487		goto out_unlock;
1488	}
1489
1490	/*
1491	 * After dropping the lock and possibly sleeping here, our request
1492	 * may now be mergeable after it had proven unmergeable (above).
1493	 * We don't worry about that case for efficiency. It won't happen
1494	 * often, and the elevators are able to handle it.
1495	 */
1496	init_request_from_bio(req, bio);
1497
1498	if (test_bit(QUEUE_FLAG_SAME_COMP, &q->queue_flags))
1499		req->cpu = raw_smp_processor_id();
1500
1501	plug = current->plug;
1502	if (plug) {
1503		/*
1504		 * If this is the first request added after a plug, fire
1505		 * of a plug trace. If others have been added before, check
1506		 * if we have multiple devices in this plug. If so, make a
1507		 * note to sort the list before dispatch.
1508		 */
1509		if (list_empty(&plug->list))
1510			trace_block_plug(q);
1511		else {
1512			if (!plug->should_sort) {
1513				struct request *__rq;
1514
1515				__rq = list_entry_rq(plug->list.prev);
1516				if (__rq->q != q)
1517					plug->should_sort = 1;
1518			}
1519			if (request_count >= BLK_MAX_REQUEST_COUNT) {
1520				blk_flush_plug_list(plug, false);
1521				trace_block_plug(q);
1522			}
1523		}
1524		list_add_tail(&req->queuelist, &plug->list);
1525		drive_stat_acct(req, 1);
1526	} else {
1527		spin_lock_irq(q->queue_lock);
1528		add_acct_request(q, req, where);
1529		__blk_run_queue(q);
1530out_unlock:
1531		spin_unlock_irq(q->queue_lock);
1532	}
1533}
1534EXPORT_SYMBOL_GPL(blk_queue_bio);	/* for device mapper only */
1535
1536/*
1537 * If bio->bi_dev is a partition, remap the location
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1538 */
1539static inline void blk_partition_remap(struct bio *bio)
1540{
1541	struct block_device *bdev = bio->bi_bdev;
1542
1543	if (bio_sectors(bio) && bdev != bdev->bd_contains) {
1544		struct hd_struct *p = bdev->bd_part;
1545
1546		bio->bi_sector += p->start_sect;
1547		bio->bi_bdev = bdev->bd_contains;
1548
1549		trace_block_bio_remap(bdev_get_queue(bio->bi_bdev), bio,
1550				      bdev->bd_dev,
1551				      bio->bi_sector - p->start_sect);
1552	}
1553}
1554
1555static void handle_bad_sector(struct bio *bio)
1556{
1557	char b[BDEVNAME_SIZE];
1558
1559	printk(KERN_INFO "attempt to access beyond end of device\n");
1560	printk(KERN_INFO "%s: rw=%ld, want=%Lu, limit=%Lu\n",
1561			bdevname(bio->bi_bdev, b),
1562			bio->bi_rw,
1563			(unsigned long long)bio->bi_sector + bio_sectors(bio),
1564			(long long)(i_size_read(bio->bi_bdev->bd_inode) >> 9));
1565
1566	set_bit(BIO_EOF, &bio->bi_flags);
1567}
 
 
 
1568
1569#ifdef CONFIG_FAIL_MAKE_REQUEST
1570
1571static DECLARE_FAULT_ATTR(fail_make_request);
 
 
 
 
 
 
 
 
 
 
1572
1573static int __init setup_fail_make_request(char *str)
1574{
1575	return setup_fault_attr(&fail_make_request, str);
1576}
1577__setup("fail_make_request=", setup_fail_make_request);
 
 
1578
1579static bool should_fail_request(struct hd_struct *part, unsigned int bytes)
1580{
1581	return part->make_it_fail && should_fail(&fail_make_request, bytes);
1582}
1583
1584static int __init fail_make_request_debugfs(void)
1585{
1586	struct dentry *dir = fault_create_debugfs_attr("fail_make_request",
1587						NULL, &fail_make_request);
1588
1589	return IS_ERR(dir) ? PTR_ERR(dir) : 0;
1590}
1591
1592late_initcall(fail_make_request_debugfs);
1593
1594#else /* CONFIG_FAIL_MAKE_REQUEST */
1595
1596static inline bool should_fail_request(struct hd_struct *part,
1597					unsigned int bytes)
1598{
1599	return false;
1600}
1601
1602#endif /* CONFIG_FAIL_MAKE_REQUEST */
1603
1604/*
1605 * Check whether this bio extends beyond the end of the device.
1606 */
1607static inline int bio_check_eod(struct bio *bio, unsigned int nr_sectors)
1608{
1609	sector_t maxsector;
1610
1611	if (!nr_sectors)
1612		return 0;
1613
1614	/* Test device or partition size, when known. */
1615	maxsector = i_size_read(bio->bi_bdev->bd_inode) >> 9;
1616	if (maxsector) {
1617		sector_t sector = bio->bi_sector;
1618
1619		if (maxsector < nr_sectors || maxsector - nr_sectors < sector) {
1620			/*
1621			 * This may well happen - the kernel calls bread()
1622			 * without checking the size of the device, e.g., when
1623			 * mounting a device.
1624			 */
1625			handle_bad_sector(bio);
1626			return 1;
1627		}
1628	}
1629
1630	return 0;
 
 
 
 
 
 
 
 
 
 
 
1631}
1632
1633static noinline_for_stack bool
1634generic_make_request_checks(struct bio *bio)
 
 
 
 
 
 
 
 
1635{
1636	struct request_queue *q;
1637	int nr_sectors = bio_sectors(bio);
1638	int err = -EIO;
1639	char b[BDEVNAME_SIZE];
1640	struct hd_struct *part;
1641
1642	might_sleep();
1643
1644	if (bio_check_eod(bio, nr_sectors))
1645		goto end_io;
1646
1647	q = bdev_get_queue(bio->bi_bdev);
1648	if (unlikely(!q)) {
1649		printk(KERN_ERR
1650		       "generic_make_request: Trying to access "
1651			"nonexistent block-device %s (%Lu)\n",
1652			bdevname(bio->bi_bdev, b),
1653			(long long) bio->bi_sector);
1654		goto end_io;
1655	}
1656
1657	if (unlikely(!(bio->bi_rw & REQ_DISCARD) &&
1658		     nr_sectors > queue_max_hw_sectors(q))) {
1659		printk(KERN_ERR "bio too big device %s (%u > %u)\n",
1660		       bdevname(bio->bi_bdev, b),
1661		       bio_sectors(bio),
1662		       queue_max_hw_sectors(q));
1663		goto end_io;
1664	}
1665
1666	part = bio->bi_bdev->bd_part;
1667	if (should_fail_request(part, bio->bi_size) ||
1668	    should_fail_request(&part_to_disk(part)->part0,
1669				bio->bi_size))
1670		goto end_io;
1671
1672	/*
1673	 * If this device has partitions, remap block n
1674	 * of partition p to block n+start(p) of the disk.
1675	 */
1676	blk_partition_remap(bio);
 
1677
1678	if (bio_integrity_enabled(bio) && bio_integrity_prep(bio))
1679		goto end_io;
1680
1681	if (bio_check_eod(bio, nr_sectors))
1682		goto end_io;
 
 
 
 
 
 
 
1683
1684	/*
1685	 * Filter flush bio's early so that make_request based
1686	 * drivers without flush support don't have to worry
1687	 * about them.
1688	 */
1689	if ((bio->bi_rw & (REQ_FLUSH | REQ_FUA)) && !q->flush_flags) {
1690		bio->bi_rw &= ~(REQ_FLUSH | REQ_FUA);
1691		if (!nr_sectors) {
1692			err = 0;
1693			goto end_io;
 
 
 
 
 
 
1694		}
1695	}
1696
1697	if ((bio->bi_rw & REQ_DISCARD) &&
1698	    (!blk_queue_discard(q) ||
1699	     ((bio->bi_rw & REQ_SECURE) &&
1700	      !blk_queue_secdiscard(q)))) {
1701		err = -EOPNOTSUPP;
1702		goto end_io;
1703	}
1704
1705	if (blk_throtl_bio(q, bio))
1706		return false;	/* throttled, will be resubmitted later */
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1707
1708	trace_block_bio_queue(q, bio);
1709	return true;
 
 
1710
 
 
1711end_io:
1712	bio_endio(bio, err);
1713	return false;
1714}
 
1715
1716/**
1717 * generic_make_request - hand a buffer to its device driver for I/O
1718 * @bio:  The bio describing the location in memory and on the device.
1719 *
1720 * generic_make_request() is used to make I/O requests of block
1721 * devices. It is passed a &struct bio, which describes the I/O that needs
1722 * to be done.
1723 *
1724 * generic_make_request() does not return any status.  The
1725 * success/failure status of the request, along with notification of
1726 * completion, is delivered asynchronously through the bio->bi_end_io
1727 * function described (one day) else where.
1728 *
1729 * The caller of generic_make_request must make sure that bi_io_vec
1730 * are set to describe the memory buffer, and that bi_dev and bi_sector are
1731 * set to describe the device address, and the
1732 * bi_end_io and optionally bi_private are set to describe how
1733 * completion notification should be signaled.
1734 *
1735 * generic_make_request and the drivers it calls may use bi_next if this
1736 * bio happens to be merged with someone else, and may resubmit the bio to
1737 * a lower device by calling into generic_make_request recursively, which
1738 * means the bio should NOT be touched after the call to ->make_request_fn.
1739 */
1740void generic_make_request(struct bio *bio)
1741{
1742	struct bio_list bio_list_on_stack;
1743
1744	if (!generic_make_request_checks(bio))
1745		return;
1746
1747	/*
1748	 * We only want one ->make_request_fn to be active at a time, else
1749	 * stack usage with stacked devices could be a problem.  So use
1750	 * current->bio_list to keep a list of requests submited by a
1751	 * make_request_fn function.  current->bio_list is also used as a
1752	 * flag to say if generic_make_request is currently active in this
1753	 * task or not.  If it is NULL, then no make_request is active.  If
1754	 * it is non-NULL, then a make_request is active, and new requests
1755	 * should be added at the tail
1756	 */
1757	if (current->bio_list) {
1758		bio_list_add(current->bio_list, bio);
1759		return;
1760	}
1761
1762	/* following loop may be a bit non-obvious, and so deserves some
1763	 * explanation.
1764	 * Before entering the loop, bio->bi_next is NULL (as all callers
1765	 * ensure that) so we have a list with a single bio.
1766	 * We pretend that we have just taken it off a longer list, so
1767	 * we assign bio_list to a pointer to the bio_list_on_stack,
1768	 * thus initialising the bio_list of new bios to be
1769	 * added.  ->make_request() may indeed add some more bios
1770	 * through a recursive call to generic_make_request.  If it
1771	 * did, we find a non-NULL value in bio_list and re-enter the loop
1772	 * from the top.  In this case we really did just take the bio
1773	 * of the top of the list (no pretending) and so remove it from
1774	 * bio_list, and call into ->make_request() again.
1775	 */
1776	BUG_ON(bio->bi_next);
1777	bio_list_init(&bio_list_on_stack);
1778	current->bio_list = &bio_list_on_stack;
1779	do {
1780		struct request_queue *q = bdev_get_queue(bio->bi_bdev);
1781
1782		q->make_request_fn(q, bio);
1783
1784		bio = bio_list_pop(current->bio_list);
1785	} while (bio);
1786	current->bio_list = NULL; /* deactivate */
1787}
1788EXPORT_SYMBOL(generic_make_request);
1789
1790/**
1791 * submit_bio - submit a bio to the block device layer for I/O
1792 * @rw: whether to %READ or %WRITE, or maybe to %READA (read ahead)
1793 * @bio: The &struct bio which describes the I/O
1794 *
1795 * submit_bio() is very similar in purpose to generic_make_request(), and
1796 * uses that function to do most of the work. Both are fairly rough
1797 * interfaces; @bio must be presetup and ready for I/O.
1798 *
1799 */
1800void submit_bio(int rw, struct bio *bio)
1801{
1802	int count = bio_sectors(bio);
1803
1804	bio->bi_rw |= rw;
1805
1806	/*
1807	 * If it's a regular read/write or a barrier with data attached,
1808	 * go through the normal accounting stuff before submission.
1809	 */
1810	if (bio_has_data(bio) && !(rw & REQ_DISCARD)) {
1811		if (rw & WRITE) {
1812			count_vm_events(PGPGOUT, count);
1813		} else {
1814			task_io_account_read(bio->bi_size);
1815			count_vm_events(PGPGIN, count);
1816		}
1817
1818		if (unlikely(block_dump)) {
1819			char b[BDEVNAME_SIZE];
1820			printk(KERN_DEBUG "%s(%d): %s block %Lu on %s (%u sectors)\n",
1821			current->comm, task_pid_nr(current),
1822				(rw & WRITE) ? "WRITE" : "READ",
1823				(unsigned long long)bio->bi_sector,
1824				bdevname(bio->bi_bdev, b),
1825				count);
1826		}
1827	}
1828
1829	generic_make_request(bio);
 
1830}
1831EXPORT_SYMBOL(submit_bio);
1832
1833/**
1834 * blk_rq_check_limits - Helper function to check a request for the queue limit
1835 * @q:  the queue
1836 * @rq: the request being checked
1837 *
1838 * Description:
1839 *    @rq may have been made based on weaker limitations of upper-level queues
1840 *    in request stacking drivers, and it may violate the limitation of @q.
1841 *    Since the block layer and the underlying device driver trust @rq
1842 *    after it is inserted to @q, it should be checked against @q before
1843 *    the insertion using this generic function.
1844 *
1845 *    This function should also be useful for request stacking drivers
1846 *    in some cases below, so export this function.
1847 *    Request stacking drivers like request-based dm may change the queue
1848 *    limits while requests are in the queue (e.g. dm's table swapping).
1849 *    Such request stacking drivers should check those requests agaist
1850 *    the new queue limits again when they dispatch those requests,
1851 *    although such checkings are also done against the old queue limits
1852 *    when submitting requests.
1853 */
1854int blk_rq_check_limits(struct request_queue *q, struct request *rq)
1855{
1856	if (rq->cmd_flags & REQ_DISCARD)
1857		return 0;
1858
1859	if (blk_rq_sectors(rq) > queue_max_sectors(q) ||
1860	    blk_rq_bytes(rq) > queue_max_hw_sectors(q) << 9) {
1861		printk(KERN_ERR "%s: over max size limit.\n", __func__);
1862		return -EIO;
1863	}
1864
1865	/*
1866	 * queue's settings related to segment counting like q->bounce_pfn
1867	 * may differ from that of other stacking queues.
1868	 * Recalculate it to check the request correctly on this queue's
1869	 * limitation.
1870	 */
1871	blk_recalc_rq_segments(rq);
1872	if (rq->nr_phys_segments > queue_max_segments(q)) {
1873		printk(KERN_ERR "%s: over max segments limit.\n", __func__);
1874		return -EIO;
1875	}
1876
1877	return 0;
1878}
1879EXPORT_SYMBOL_GPL(blk_rq_check_limits);
1880
1881/**
1882 * blk_insert_cloned_request - Helper for stacking drivers to submit a request
1883 * @q:  the queue to submit the request
1884 * @rq: the request being queued
1885 */
1886int blk_insert_cloned_request(struct request_queue *q, struct request *rq)
1887{
1888	unsigned long flags;
1889	int where = ELEVATOR_INSERT_BACK;
1890
1891	if (blk_rq_check_limits(q, rq))
1892		return -EIO;
1893
1894	if (rq->rq_disk &&
1895	    should_fail_request(&rq->rq_disk->part0, blk_rq_bytes(rq)))
1896		return -EIO;
1897
1898	spin_lock_irqsave(q->queue_lock, flags);
1899	if (unlikely(blk_queue_dead(q))) {
1900		spin_unlock_irqrestore(q->queue_lock, flags);
1901		return -ENODEV;
1902	}
1903
1904	/*
1905	 * Submitting request must be dequeued before calling this function
1906	 * because it will be linked to another request_queue
1907	 */
1908	BUG_ON(blk_queued_rq(rq));
1909
1910	if (rq->cmd_flags & (REQ_FLUSH|REQ_FUA))
1911		where = ELEVATOR_INSERT_FLUSH;
1912
1913	add_acct_request(q, rq, where);
1914	if (where == ELEVATOR_INSERT_FLUSH)
1915		__blk_run_queue(q);
1916	spin_unlock_irqrestore(q->queue_lock, flags);
1917
1918	return 0;
1919}
1920EXPORT_SYMBOL_GPL(blk_insert_cloned_request);
1921
1922/**
1923 * blk_rq_err_bytes - determine number of bytes till the next failure boundary
1924 * @rq: request to examine
1925 *
1926 * Description:
1927 *     A request could be merge of IOs which require different failure
1928 *     handling.  This function determines the number of bytes which
1929 *     can be failed from the beginning of the request without
1930 *     crossing into area which need to be retried further.
1931 *
1932 * Return:
1933 *     The number of bytes to fail.
1934 *
1935 * Context:
1936 *     queue_lock must be held.
1937 */
1938unsigned int blk_rq_err_bytes(const struct request *rq)
1939{
1940	unsigned int ff = rq->cmd_flags & REQ_FAILFAST_MASK;
1941	unsigned int bytes = 0;
1942	struct bio *bio;
1943
1944	if (!(rq->cmd_flags & REQ_MIXED_MERGE))
1945		return blk_rq_bytes(rq);
1946
1947	/*
1948	 * Currently the only 'mixing' which can happen is between
1949	 * different fastfail types.  We can safely fail portions
1950	 * which have all the failfast bits that the first one has -
1951	 * the ones which are at least as eager to fail as the first
1952	 * one.
1953	 */
1954	for (bio = rq->bio; bio; bio = bio->bi_next) {
1955		if ((bio->bi_rw & ff) != ff)
1956			break;
1957		bytes += bio->bi_size;
1958	}
1959
1960	/* this could lead to infinite loop */
1961	BUG_ON(blk_rq_bytes(rq) && !bytes);
1962	return bytes;
1963}
1964EXPORT_SYMBOL_GPL(blk_rq_err_bytes);
1965
1966static void blk_account_io_completion(struct request *req, unsigned int bytes)
1967{
1968	if (blk_do_io_stat(req)) {
1969		const int rw = rq_data_dir(req);
1970		struct hd_struct *part;
1971		int cpu;
1972
1973		cpu = part_stat_lock();
1974		part = req->part;
1975		part_stat_add(cpu, part, sectors[rw], bytes >> 9);
1976		part_stat_unlock();
1977	}
1978}
1979
1980static void blk_account_io_done(struct request *req)
1981{
1982	/*
1983	 * Account IO completion.  flush_rq isn't accounted as a
1984	 * normal IO on queueing nor completion.  Accounting the
1985	 * containing request is enough.
 
 
 
 
 
 
 
 
 
 
 
 
1986	 */
1987	if (blk_do_io_stat(req) && !(req->cmd_flags & REQ_FLUSH_SEQ)) {
1988		unsigned long duration = jiffies - req->start_time;
1989		const int rw = rq_data_dir(req);
1990		struct hd_struct *part;
1991		int cpu;
1992
1993		cpu = part_stat_lock();
1994		part = req->part;
1995
1996		part_stat_inc(cpu, part, ios[rw]);
1997		part_stat_add(cpu, part, ticks[rw], duration);
1998		part_round_stats(cpu, part);
1999		part_dec_in_flight(part, rw);
2000
2001		hd_struct_put(part);
2002		part_stat_unlock();
2003	}
2004}
2005
2006/**
2007 * blk_peek_request - peek at the top of a request queue
2008 * @q: request queue to peek at
2009 *
2010 * Description:
2011 *     Return the request at the top of @q.  The returned request
2012 *     should be started using blk_start_request() before LLD starts
2013 *     processing it.
2014 *
2015 * Return:
2016 *     Pointer to the request at the top of @q if available.  Null
2017 *     otherwise.
2018 *
2019 * Context:
2020 *     queue_lock must be held.
2021 */
2022struct request *blk_peek_request(struct request_queue *q)
2023{
2024	struct request *rq;
2025	int ret;
2026
2027	while ((rq = __elv_next_request(q)) != NULL) {
2028		if (!(rq->cmd_flags & REQ_STARTED)) {
2029			/*
2030			 * This is the first time the device driver
2031			 * sees this request (possibly after
2032			 * requeueing).  Notify IO scheduler.
2033			 */
2034			if (rq->cmd_flags & REQ_SORTED)
2035				elv_activate_rq(q, rq);
2036
2037			/*
2038			 * just mark as started even if we don't start
2039			 * it, a request that has been delayed should
2040			 * not be passed by new incoming requests
2041			 */
2042			rq->cmd_flags |= REQ_STARTED;
2043			trace_block_rq_issue(q, rq);
2044		}
2045
2046		if (!q->boundary_rq || q->boundary_rq == rq) {
2047			q->end_sector = rq_end_sector(rq);
2048			q->boundary_rq = NULL;
2049		}
2050
2051		if (rq->cmd_flags & REQ_DONTPREP)
2052			break;
2053
2054		if (q->dma_drain_size && blk_rq_bytes(rq)) {
2055			/*
2056			 * make sure space for the drain appears we
2057			 * know we can do this because max_hw_segments
2058			 * has been adjusted to be one fewer than the
2059			 * device can handle
2060			 */
2061			rq->nr_phys_segments++;
2062		}
2063
2064		if (!q->prep_rq_fn)
2065			break;
2066
2067		ret = q->prep_rq_fn(q, rq);
2068		if (ret == BLKPREP_OK) {
2069			break;
2070		} else if (ret == BLKPREP_DEFER) {
2071			/*
2072			 * the request may have been (partially) prepped.
2073			 * we need to keep this request in the front to
2074			 * avoid resource deadlock.  REQ_STARTED will
2075			 * prevent other fs requests from passing this one.
2076			 */
2077			if (q->dma_drain_size && blk_rq_bytes(rq) &&
2078			    !(rq->cmd_flags & REQ_DONTPREP)) {
2079				/*
2080				 * remove the space for the drain we added
2081				 * so that we don't add it again
2082				 */
2083				--rq->nr_phys_segments;
2084			}
2085
2086			rq = NULL;
2087			break;
2088		} else if (ret == BLKPREP_KILL) {
2089			rq->cmd_flags |= REQ_QUIET;
2090			/*
2091			 * Mark this request as started so we don't trigger
2092			 * any debug logic in the end I/O path.
2093			 */
2094			blk_start_request(rq);
2095			__blk_end_request_all(rq, -EIO);
2096		} else {
2097			printk(KERN_ERR "%s: bad return=%d\n", __func__, ret);
2098			break;
2099		}
2100	}
2101
2102	return rq;
2103}
2104EXPORT_SYMBOL(blk_peek_request);
2105
2106void blk_dequeue_request(struct request *rq)
2107{
2108	struct request_queue *q = rq->q;
2109
2110	BUG_ON(list_empty(&rq->queuelist));
2111	BUG_ON(ELV_ON_HASH(rq));
2112
2113	list_del_init(&rq->queuelist);
2114
2115	/*
2116	 * the time frame between a request being removed from the lists
2117	 * and to it is freed is accounted as io that is in progress at
2118	 * the driver side.
2119	 */
2120	if (blk_account_rq(rq)) {
2121		q->in_flight[rq_is_sync(rq)]++;
2122		set_io_start_time_ns(rq);
2123	}
2124}
2125
2126/**
2127 * blk_start_request - start request processing on the driver
2128 * @req: request to dequeue
2129 *
2130 * Description:
2131 *     Dequeue @req and start timeout timer on it.  This hands off the
2132 *     request to the driver.
2133 *
2134 *     Block internal functions which don't want to start timer should
2135 *     call blk_dequeue_request().
2136 *
2137 * Context:
2138 *     queue_lock must be held.
2139 */
2140void blk_start_request(struct request *req)
2141{
2142	blk_dequeue_request(req);
2143
2144	/*
2145	 * We are now handing the request to the hardware, initialize
2146	 * resid_len to full count and add the timeout handler.
2147	 */
2148	req->resid_len = blk_rq_bytes(req);
2149	if (unlikely(blk_bidi_rq(req)))
2150		req->next_rq->resid_len = blk_rq_bytes(req->next_rq);
2151
2152	blk_add_timer(req);
2153}
2154EXPORT_SYMBOL(blk_start_request);
2155
2156/**
2157 * blk_fetch_request - fetch a request from a request queue
2158 * @q: request queue to fetch a request from
2159 *
2160 * Description:
2161 *     Return the request at the top of @q.  The request is started on
2162 *     return and LLD can start processing it immediately.
2163 *
2164 * Return:
2165 *     Pointer to the request at the top of @q if available.  Null
2166 *     otherwise.
2167 *
2168 * Context:
2169 *     queue_lock must be held.
2170 */
2171struct request *blk_fetch_request(struct request_queue *q)
 
2172{
2173	struct request *rq;
2174
2175	rq = blk_peek_request(q);
2176	if (rq)
2177		blk_start_request(rq);
2178	return rq;
2179}
2180EXPORT_SYMBOL(blk_fetch_request);
2181
2182/**
2183 * blk_update_request - Special helper function for request stacking drivers
2184 * @req:      the request being processed
2185 * @error:    %0 for success, < %0 for error
2186 * @nr_bytes: number of bytes to complete @req
2187 *
2188 * Description:
2189 *     Ends I/O on a number of bytes attached to @req, but doesn't complete
2190 *     the request structure even if @req doesn't have leftover.
2191 *     If @req has leftover, sets it up for the next range of segments.
2192 *
2193 *     This special helper function is only for request stacking drivers
2194 *     (e.g. request-based dm) so that they can handle partial completion.
2195 *     Actual device drivers should use blk_end_request instead.
2196 *
2197 *     Passing the result of blk_rq_bytes() as @nr_bytes guarantees
2198 *     %false return from this function.
2199 *
2200 * Return:
2201 *     %false - this request doesn't have any more data
2202 *     %true  - this request has more data
2203 **/
2204bool blk_update_request(struct request *req, int error, unsigned int nr_bytes)
2205{
2206	int total_bytes, bio_nbytes, next_idx = 0;
2207	struct bio *bio;
2208
2209	if (!req->bio)
2210		return false;
2211
2212	trace_block_rq_complete(req->q, req);
2213
2214	/*
2215	 * For fs requests, rq is just carrier of independent bio's
2216	 * and each partial completion should be handled separately.
2217	 * Reset per-request error on each partial completion.
2218	 *
2219	 * TODO: tj: This is too subtle.  It would be better to let
2220	 * low level drivers do what they see fit.
2221	 */
2222	if (req->cmd_type == REQ_TYPE_FS)
2223		req->errors = 0;
2224
2225	if (error && req->cmd_type == REQ_TYPE_FS &&
2226	    !(req->cmd_flags & REQ_QUIET)) {
2227		char *error_type;
2228
2229		switch (error) {
2230		case -ENOLINK:
2231			error_type = "recoverable transport";
2232			break;
2233		case -EREMOTEIO:
2234			error_type = "critical target";
2235			break;
2236		case -EBADE:
2237			error_type = "critical nexus";
2238			break;
2239		case -EIO:
2240		default:
2241			error_type = "I/O";
2242			break;
2243		}
2244		printk(KERN_ERR "end_request: %s error, dev %s, sector %llu\n",
2245		       error_type, req->rq_disk ? req->rq_disk->disk_name : "?",
2246		       (unsigned long long)blk_rq_pos(req));
2247	}
2248
2249	blk_account_io_completion(req, nr_bytes);
2250
2251	total_bytes = bio_nbytes = 0;
2252	while ((bio = req->bio) != NULL) {
2253		int nbytes;
2254
2255		if (nr_bytes >= bio->bi_size) {
2256			req->bio = bio->bi_next;
2257			nbytes = bio->bi_size;
2258			req_bio_endio(req, bio, nbytes, error);
2259			next_idx = 0;
2260			bio_nbytes = 0;
2261		} else {
2262			int idx = bio->bi_idx + next_idx;
2263
2264			if (unlikely(idx >= bio->bi_vcnt)) {
2265				blk_dump_rq_flags(req, "__end_that");
2266				printk(KERN_ERR "%s: bio idx %d >= vcnt %d\n",
2267				       __func__, idx, bio->bi_vcnt);
2268				break;
2269			}
2270
2271			nbytes = bio_iovec_idx(bio, idx)->bv_len;
2272			BIO_BUG_ON(nbytes > bio->bi_size);
2273
2274			/*
2275			 * not a complete bvec done
2276			 */
2277			if (unlikely(nbytes > nr_bytes)) {
2278				bio_nbytes += nr_bytes;
2279				total_bytes += nr_bytes;
2280				break;
2281			}
2282
2283			/*
2284			 * advance to the next vector
2285			 */
2286			next_idx++;
2287			bio_nbytes += nbytes;
2288		}
2289
2290		total_bytes += nbytes;
2291		nr_bytes -= nbytes;
2292
2293		bio = req->bio;
2294		if (bio) {
2295			/*
2296			 * end more in this run, or just return 'not-done'
2297			 */
2298			if (unlikely(nr_bytes <= 0))
2299				break;
2300		}
2301	}
2302
2303	/*
2304	 * completely done
2305	 */
2306	if (!req->bio) {
2307		/*
2308		 * Reset counters so that the request stacking driver
2309		 * can find how many bytes remain in the request
2310		 * later.
2311		 */
2312		req->__data_len = 0;
2313		return false;
2314	}
2315
2316	/*
2317	 * if the request wasn't completed, update state
2318	 */
2319	if (bio_nbytes) {
2320		req_bio_endio(req, bio, bio_nbytes, error);
2321		bio->bi_idx += next_idx;
2322		bio_iovec(bio)->bv_offset += nr_bytes;
2323		bio_iovec(bio)->bv_len -= nr_bytes;
2324	}
2325
2326	req->__data_len -= total_bytes;
2327	req->buffer = bio_data(req->bio);
2328
2329	/* update sector only for requests with clear definition of sector */
2330	if (req->cmd_type == REQ_TYPE_FS || (req->cmd_flags & REQ_DISCARD))
2331		req->__sector += total_bytes >> 9;
2332
2333	/* mixed attributes always follow the first bio */
2334	if (req->cmd_flags & REQ_MIXED_MERGE) {
2335		req->cmd_flags &= ~REQ_FAILFAST_MASK;
2336		req->cmd_flags |= req->bio->bi_rw & REQ_FAILFAST_MASK;
2337	}
2338
2339	/*
2340	 * If total number of sectors is less than the first segment
2341	 * size, something has gone terribly wrong.
2342	 */
2343	if (blk_rq_bytes(req) < blk_rq_cur_bytes(req)) {
2344		blk_dump_rq_flags(req, "request botched");
2345		req->__data_len = blk_rq_cur_bytes(req);
2346	}
2347
2348	/* recalculate the number of segments */
2349	blk_recalc_rq_segments(req);
2350
2351	return true;
2352}
2353EXPORT_SYMBOL_GPL(blk_update_request);
2354
2355static bool blk_update_bidi_request(struct request *rq, int error,
2356				    unsigned int nr_bytes,
2357				    unsigned int bidi_bytes)
2358{
2359	if (blk_update_request(rq, error, nr_bytes))
2360		return true;
2361
2362	/* Bidi request must be completed as a whole */
2363	if (unlikely(blk_bidi_rq(rq)) &&
2364	    blk_update_request(rq->next_rq, error, bidi_bytes))
2365		return true;
2366
2367	if (blk_queue_add_random(rq->q))
2368		add_disk_randomness(rq->rq_disk);
2369
2370	return false;
2371}
2372
2373/**
2374 * blk_unprep_request - unprepare a request
2375 * @req:	the request
2376 *
2377 * This function makes a request ready for complete resubmission (or
2378 * completion).  It happens only after all error handling is complete,
2379 * so represents the appropriate moment to deallocate any resources
2380 * that were allocated to the request in the prep_rq_fn.  The queue
2381 * lock is held when calling this.
2382 */
2383void blk_unprep_request(struct request *req)
2384{
2385	struct request_queue *q = req->q;
2386
2387	req->cmd_flags &= ~REQ_DONTPREP;
2388	if (q->unprep_rq_fn)
2389		q->unprep_rq_fn(q, req);
2390}
2391EXPORT_SYMBOL_GPL(blk_unprep_request);
2392
2393/*
2394 * queue lock must be held
2395 */
2396static void blk_finish_request(struct request *req, int error)
2397{
2398	if (blk_rq_tagged(req))
2399		blk_queue_end_tag(req->q, req);
2400
2401	BUG_ON(blk_queued_rq(req));
2402
2403	if (unlikely(laptop_mode) && req->cmd_type == REQ_TYPE_FS)
2404		laptop_io_completion(&req->q->backing_dev_info);
2405
2406	blk_delete_timer(req);
2407
2408	if (req->cmd_flags & REQ_DONTPREP)
2409		blk_unprep_request(req);
2410
2411
2412	blk_account_io_done(req);
2413
2414	if (req->end_io)
2415		req->end_io(req, error);
2416	else {
2417		if (blk_bidi_rq(req))
2418			__blk_put_request(req->next_rq->q, req->next_rq);
2419
2420		__blk_put_request(req->q, req);
2421	}
2422}
2423
2424/**
2425 * blk_end_bidi_request - Complete a bidi request
2426 * @rq:         the request to complete
2427 * @error:      %0 for success, < %0 for error
2428 * @nr_bytes:   number of bytes to complete @rq
2429 * @bidi_bytes: number of bytes to complete @rq->next_rq
2430 *
2431 * Description:
2432 *     Ends I/O on a number of bytes attached to @rq and @rq->next_rq.
2433 *     Drivers that supports bidi can safely call this member for any
2434 *     type of request, bidi or uni.  In the later case @bidi_bytes is
2435 *     just ignored.
2436 *
2437 * Return:
2438 *     %false - we are done with this request
2439 *     %true  - still buffers pending for this request
2440 **/
2441static bool blk_end_bidi_request(struct request *rq, int error,
2442				 unsigned int nr_bytes, unsigned int bidi_bytes)
2443{
2444	struct request_queue *q = rq->q;
2445	unsigned long flags;
2446
2447	if (blk_update_bidi_request(rq, error, nr_bytes, bidi_bytes))
2448		return true;
2449
2450	spin_lock_irqsave(q->queue_lock, flags);
2451	blk_finish_request(rq, error);
2452	spin_unlock_irqrestore(q->queue_lock, flags);
2453
2454	return false;
2455}
2456
2457/**
2458 * __blk_end_bidi_request - Complete a bidi request with queue lock held
2459 * @rq:         the request to complete
2460 * @error:      %0 for success, < %0 for error
2461 * @nr_bytes:   number of bytes to complete @rq
2462 * @bidi_bytes: number of bytes to complete @rq->next_rq
2463 *
2464 * Description:
2465 *     Identical to blk_end_bidi_request() except that queue lock is
2466 *     assumed to be locked on entry and remains so on return.
2467 *
2468 * Return:
2469 *     %false - we are done with this request
2470 *     %true  - still buffers pending for this request
2471 **/
2472bool __blk_end_bidi_request(struct request *rq, int error,
2473				   unsigned int nr_bytes, unsigned int bidi_bytes)
2474{
2475	if (blk_update_bidi_request(rq, error, nr_bytes, bidi_bytes))
2476		return true;
2477
2478	blk_finish_request(rq, error);
2479
2480	return false;
2481}
2482
2483/**
2484 * blk_end_request - Helper function for drivers to complete the request.
2485 * @rq:       the request being processed
2486 * @error:    %0 for success, < %0 for error
2487 * @nr_bytes: number of bytes to complete
2488 *
2489 * Description:
2490 *     Ends I/O on a number of bytes attached to @rq.
2491 *     If @rq has leftover, sets it up for the next range of segments.
2492 *
2493 * Return:
2494 *     %false - we are done with this request
2495 *     %true  - still buffers pending for this request
2496 **/
2497bool blk_end_request(struct request *rq, int error, unsigned int nr_bytes)
2498{
2499	return blk_end_bidi_request(rq, error, nr_bytes, 0);
2500}
2501EXPORT_SYMBOL(blk_end_request);
2502
2503/**
2504 * blk_end_request_all - Helper function for drives to finish the request.
2505 * @rq: the request to finish
2506 * @error: %0 for success, < %0 for error
2507 *
2508 * Description:
2509 *     Completely finish @rq.
2510 */
2511void blk_end_request_all(struct request *rq, int error)
2512{
2513	bool pending;
2514	unsigned int bidi_bytes = 0;
2515
2516	if (unlikely(blk_bidi_rq(rq)))
2517		bidi_bytes = blk_rq_bytes(rq->next_rq);
2518
2519	pending = blk_end_bidi_request(rq, error, blk_rq_bytes(rq), bidi_bytes);
2520	BUG_ON(pending);
2521}
2522EXPORT_SYMBOL(blk_end_request_all);
2523
2524/**
2525 * blk_end_request_cur - Helper function to finish the current request chunk.
2526 * @rq: the request to finish the current chunk for
2527 * @error: %0 for success, < %0 for error
2528 *
2529 * Description:
2530 *     Complete the current consecutively mapped chunk from @rq.
2531 *
2532 * Return:
2533 *     %false - we are done with this request
2534 *     %true  - still buffers pending for this request
2535 */
2536bool blk_end_request_cur(struct request *rq, int error)
2537{
2538	return blk_end_request(rq, error, blk_rq_cur_bytes(rq));
2539}
2540EXPORT_SYMBOL(blk_end_request_cur);
2541
2542/**
2543 * blk_end_request_err - Finish a request till the next failure boundary.
2544 * @rq: the request to finish till the next failure boundary for
2545 * @error: must be negative errno
2546 *
2547 * Description:
2548 *     Complete @rq till the next failure boundary.
2549 *
2550 * Return:
2551 *     %false - we are done with this request
2552 *     %true  - still buffers pending for this request
2553 */
2554bool blk_end_request_err(struct request *rq, int error)
2555{
2556	WARN_ON(error >= 0);
2557	return blk_end_request(rq, error, blk_rq_err_bytes(rq));
2558}
2559EXPORT_SYMBOL_GPL(blk_end_request_err);
2560
2561/**
2562 * __blk_end_request - Helper function for drivers to complete the request.
2563 * @rq:       the request being processed
2564 * @error:    %0 for success, < %0 for error
2565 * @nr_bytes: number of bytes to complete
2566 *
2567 * Description:
2568 *     Must be called with queue lock held unlike blk_end_request().
2569 *
2570 * Return:
2571 *     %false - we are done with this request
2572 *     %true  - still buffers pending for this request
2573 **/
2574bool __blk_end_request(struct request *rq, int error, unsigned int nr_bytes)
2575{
2576	return __blk_end_bidi_request(rq, error, nr_bytes, 0);
2577}
2578EXPORT_SYMBOL(__blk_end_request);
2579
2580/**
2581 * __blk_end_request_all - Helper function for drives to finish the request.
2582 * @rq: the request to finish
2583 * @error: %0 for success, < %0 for error
2584 *
2585 * Description:
2586 *     Completely finish @rq.  Must be called with queue lock held.
2587 */
2588void __blk_end_request_all(struct request *rq, int error)
2589{
2590	bool pending;
2591	unsigned int bidi_bytes = 0;
2592
2593	if (unlikely(blk_bidi_rq(rq)))
2594		bidi_bytes = blk_rq_bytes(rq->next_rq);
2595
2596	pending = __blk_end_bidi_request(rq, error, blk_rq_bytes(rq), bidi_bytes);
2597	BUG_ON(pending);
2598}
2599EXPORT_SYMBOL(__blk_end_request_all);
2600
2601/**
2602 * __blk_end_request_cur - Helper function to finish the current request chunk.
2603 * @rq: the request to finish the current chunk for
2604 * @error: %0 for success, < %0 for error
2605 *
2606 * Description:
2607 *     Complete the current consecutively mapped chunk from @rq.  Must
2608 *     be called with queue lock held.
2609 *
2610 * Return:
2611 *     %false - we are done with this request
2612 *     %true  - still buffers pending for this request
2613 */
2614bool __blk_end_request_cur(struct request *rq, int error)
2615{
2616	return __blk_end_request(rq, error, blk_rq_cur_bytes(rq));
2617}
2618EXPORT_SYMBOL(__blk_end_request_cur);
2619
2620/**
2621 * __blk_end_request_err - Finish a request till the next failure boundary.
2622 * @rq: the request to finish till the next failure boundary for
2623 * @error: must be negative errno
2624 *
2625 * Description:
2626 *     Complete @rq till the next failure boundary.  Must be called
2627 *     with queue lock held.
2628 *
2629 * Return:
2630 *     %false - we are done with this request
2631 *     %true  - still buffers pending for this request
2632 */
2633bool __blk_end_request_err(struct request *rq, int error)
2634{
2635	WARN_ON(error >= 0);
2636	return __blk_end_request(rq, error, blk_rq_err_bytes(rq));
2637}
2638EXPORT_SYMBOL_GPL(__blk_end_request_err);
2639
2640void blk_rq_bio_prep(struct request_queue *q, struct request *rq,
2641		     struct bio *bio)
2642{
2643	/* Bit 0 (R/W) is identical in rq->cmd_flags and bio->bi_rw */
2644	rq->cmd_flags |= bio->bi_rw & REQ_WRITE;
 
2645
2646	if (bio_has_data(bio)) {
2647		rq->nr_phys_segments = bio_phys_segments(q, bio);
2648		rq->buffer = bio_data(bio);
2649	}
2650	rq->__data_len = bio->bi_size;
2651	rq->bio = rq->biotail = bio;
2652
2653	if (bio->bi_bdev)
2654		rq->rq_disk = bio->bi_bdev->bd_disk;
2655}
 
2656
2657#if ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE
2658/**
2659 * rq_flush_dcache_pages - Helper function to flush all pages in a request
2660 * @rq: the request to be flushed
2661 *
2662 * Description:
2663 *     Flush all pages in @rq.
2664 */
2665void rq_flush_dcache_pages(struct request *rq)
2666{
2667	struct req_iterator iter;
2668	struct bio_vec *bvec;
2669
2670	rq_for_each_segment(bvec, rq, iter)
2671		flush_dcache_page(bvec->bv_page);
2672}
2673EXPORT_SYMBOL_GPL(rq_flush_dcache_pages);
2674#endif
2675
2676/**
2677 * blk_lld_busy - Check if underlying low-level drivers of a device are busy
2678 * @q : the queue of the device being checked
2679 *
2680 * Description:
2681 *    Check if underlying low-level drivers of a device are busy.
2682 *    If the drivers want to export their busy state, they must set own
2683 *    exporting function using blk_queue_lld_busy() first.
2684 *
2685 *    Basically, this function is used only by request stacking drivers
2686 *    to stop dispatching requests to underlying devices when underlying
2687 *    devices are busy.  This behavior helps more I/O merging on the queue
2688 *    of the request stacking driver and prevents I/O throughput regression
2689 *    on burst I/O load.
2690 *
2691 * Return:
2692 *    0 - Not busy (The request stacking driver should dispatch request)
2693 *    1 - Busy (The request stacking driver should stop dispatching request)
2694 */
2695int blk_lld_busy(struct request_queue *q)
2696{
2697	if (q->lld_busy_fn)
2698		return q->lld_busy_fn(q);
2699
2700	return 0;
2701}
2702EXPORT_SYMBOL_GPL(blk_lld_busy);
2703
2704/**
2705 * blk_rq_unprep_clone - Helper function to free all bios in a cloned request
2706 * @rq: the clone request to be cleaned up
2707 *
2708 * Description:
2709 *     Free all bios in @rq for a cloned request.
2710 */
2711void blk_rq_unprep_clone(struct request *rq)
2712{
2713	struct bio *bio;
2714
2715	while ((bio = rq->bio) != NULL) {
2716		rq->bio = bio->bi_next;
2717
2718		bio_put(bio);
2719	}
2720}
2721EXPORT_SYMBOL_GPL(blk_rq_unprep_clone);
2722
2723/*
2724 * Copy attributes of the original request to the clone request.
2725 * The actual data parts (e.g. ->cmd, ->buffer, ->sense) are not copied.
2726 */
2727static void __blk_rq_prep_clone(struct request *dst, struct request *src)
2728{
2729	dst->cpu = src->cpu;
2730	dst->cmd_flags = (src->cmd_flags & REQ_CLONE_MASK) | REQ_NOMERGE;
2731	dst->cmd_type = src->cmd_type;
2732	dst->__sector = blk_rq_pos(src);
2733	dst->__data_len = blk_rq_bytes(src);
2734	dst->nr_phys_segments = src->nr_phys_segments;
2735	dst->ioprio = src->ioprio;
2736	dst->extra_len = src->extra_len;
2737}
 
2738
2739/**
2740 * blk_rq_prep_clone - Helper function to setup clone request
2741 * @rq: the request to be setup
2742 * @rq_src: original request to be cloned
2743 * @bs: bio_set that bios for clone are allocated from
2744 * @gfp_mask: memory allocation mask for bio
2745 * @bio_ctr: setup function to be called for each clone bio.
2746 *           Returns %0 for success, non %0 for failure.
2747 * @data: private data to be passed to @bio_ctr
2748 *
2749 * Description:
2750 *     Clones bios in @rq_src to @rq, and copies attributes of @rq_src to @rq.
2751 *     The actual data parts of @rq_src (e.g. ->cmd, ->buffer, ->sense)
2752 *     are not copied, and copying such parts is the caller's responsibility.
2753 *     Also, pages which the original bios are pointing to are not copied
2754 *     and the cloned bios just point same pages.
2755 *     So cloned bios must be completed before original bios, which means
2756 *     the caller must complete @rq before @rq_src.
2757 */
2758int blk_rq_prep_clone(struct request *rq, struct request *rq_src,
2759		      struct bio_set *bs, gfp_t gfp_mask,
2760		      int (*bio_ctr)(struct bio *, struct bio *, void *),
2761		      void *data)
2762{
2763	struct bio *bio, *bio_src;
2764
2765	if (!bs)
2766		bs = fs_bio_set;
2767
2768	blk_rq_init(NULL, rq);
2769
2770	__rq_for_each_bio(bio_src, rq_src) {
2771		bio = bio_alloc_bioset(gfp_mask, bio_src->bi_max_vecs, bs);
2772		if (!bio)
2773			goto free_and_out;
2774
2775		__bio_clone(bio, bio_src);
2776
2777		if (bio_integrity(bio_src) &&
2778		    bio_integrity_clone(bio, bio_src, gfp_mask, bs))
2779			goto free_and_out;
2780
2781		if (bio_ctr && bio_ctr(bio, bio_src, data))
2782			goto free_and_out;
2783
2784		if (rq->bio) {
2785			rq->biotail->bi_next = bio;
2786			rq->biotail = bio;
2787		} else
2788			rq->bio = rq->biotail = bio;
2789	}
2790
2791	__blk_rq_prep_clone(rq, rq_src);
2792
2793	return 0;
2794
2795free_and_out:
2796	if (bio)
2797		bio_free(bio, bs);
2798	blk_rq_unprep_clone(rq);
2799
2800	return -ENOMEM;
2801}
2802EXPORT_SYMBOL_GPL(blk_rq_prep_clone);
 
 
2803
2804int kblockd_schedule_work(struct request_queue *q, struct work_struct *work)
2805{
2806	return queue_work(kblockd_workqueue, work);
2807}
2808EXPORT_SYMBOL(kblockd_schedule_work);
 
 
 
2809
2810int kblockd_schedule_delayed_work(struct request_queue *q,
2811			struct delayed_work *dwork, unsigned long delay)
2812{
2813	return queue_delayed_work(kblockd_workqueue, dwork, delay);
 
2814}
2815EXPORT_SYMBOL(kblockd_schedule_delayed_work);
2816
2817#define PLUG_MAGIC	0x91827364
2818
2819/**
2820 * blk_start_plug - initialize blk_plug and track it inside the task_struct
2821 * @plug:	The &struct blk_plug that needs to be initialized
2822 *
2823 * Description:
 
 
 
 
 
 
 
 
 
2824 *   Tracking blk_plug inside the task_struct will help with auto-flushing the
2825 *   pending I/O should the task end up blocking between blk_start_plug() and
2826 *   blk_finish_plug(). This is important from a performance perspective, but
2827 *   also ensures that we don't deadlock. For instance, if the task is blocking
2828 *   for a memory allocation, memory reclaim could end up wanting to free a
2829 *   page belonging to that request that is currently residing in our private
2830 *   plug. By flushing the pending I/O when the process goes to sleep, we avoid
2831 *   this kind of deadlock.
2832 */
2833void blk_start_plug(struct blk_plug *plug)
2834{
2835	struct task_struct *tsk = current;
2836
2837	plug->magic = PLUG_MAGIC;
2838	INIT_LIST_HEAD(&plug->list);
2839	INIT_LIST_HEAD(&plug->cb_list);
2840	plug->should_sort = 0;
2841
2842	/*
2843	 * If this is a nested plug, don't actually assign it. It will be
2844	 * flushed on its own.
2845	 */
2846	if (!tsk->plug) {
2847		/*
2848		 * Store ordering should not be needed here, since a potential
2849		 * preempt will imply a full memory barrier
2850		 */
2851		tsk->plug = plug;
2852	}
2853}
2854EXPORT_SYMBOL(blk_start_plug);
2855
2856static int plug_rq_cmp(void *priv, struct list_head *a, struct list_head *b)
2857{
2858	struct request *rqa = container_of(a, struct request, queuelist);
2859	struct request *rqb = container_of(b, struct request, queuelist);
2860
2861	return !(rqa->q <= rqb->q);
2862}
2863
2864/*
2865 * If 'from_schedule' is true, then postpone the dispatch of requests
2866 * until a safe kblockd context. We due this to avoid accidental big
2867 * additional stack usage in driver dispatch, in places where the originally
2868 * plugger did not intend it.
2869 */
2870static void queue_unplugged(struct request_queue *q, unsigned int depth,
2871			    bool from_schedule)
2872	__releases(q->queue_lock)
2873{
2874	trace_block_unplug(q, depth, !from_schedule);
2875
2876	/*
2877	 * Don't mess with dead queue.
2878	 */
2879	if (unlikely(blk_queue_dead(q))) {
2880		spin_unlock(q->queue_lock);
2881		return;
2882	}
2883
2884	/*
2885	 * If we are punting this to kblockd, then we can safely drop
2886	 * the queue_lock before waking kblockd (which needs to take
2887	 * this lock).
2888	 */
2889	if (from_schedule) {
2890		spin_unlock(q->queue_lock);
2891		blk_run_queue_async(q);
2892	} else {
2893		__blk_run_queue(q);
2894		spin_unlock(q->queue_lock);
2895	}
2896
2897}
2898
2899static void flush_plug_callbacks(struct blk_plug *plug)
2900{
2901	LIST_HEAD(callbacks);
2902
2903	if (list_empty(&plug->cb_list))
2904		return;
2905
2906	list_splice_init(&plug->cb_list, &callbacks);
2907
2908	while (!list_empty(&callbacks)) {
2909		struct blk_plug_cb *cb = list_first_entry(&callbacks,
2910							  struct blk_plug_cb,
2911							  list);
2912		list_del(&cb->list);
2913		cb->callback(cb);
 
2914	}
2915}
2916
2917void blk_flush_plug_list(struct blk_plug *plug, bool from_schedule)
 
2918{
2919	struct request_queue *q;
2920	unsigned long flags;
2921	struct request *rq;
2922	LIST_HEAD(list);
2923	unsigned int depth;
2924
2925	BUG_ON(plug->magic != PLUG_MAGIC);
2926
2927	flush_plug_callbacks(plug);
2928	if (list_empty(&plug->list))
2929		return;
2930
2931	list_splice_init(&plug->list, &list);
2932
2933	if (plug->should_sort) {
2934		list_sort(NULL, &list, plug_rq_cmp);
2935		plug->should_sort = 0;
2936	}
2937
2938	q = NULL;
2939	depth = 0;
2940
2941	/*
2942	 * Save and disable interrupts here, to avoid doing it for every
2943	 * queue lock we have to take.
2944	 */
2945	local_irq_save(flags);
2946	while (!list_empty(&list)) {
2947		rq = list_entry_rq(list.next);
2948		list_del_init(&rq->queuelist);
2949		BUG_ON(!rq->q);
2950		if (rq->q != q) {
2951			/*
2952			 * This drops the queue lock
2953			 */
2954			if (q)
2955				queue_unplugged(q, depth, from_schedule);
2956			q = rq->q;
2957			depth = 0;
2958			spin_lock(q->queue_lock);
2959		}
2960
2961		/*
2962		 * Short-circuit if @q is dead
2963		 */
2964		if (unlikely(blk_queue_dead(q))) {
2965			__blk_end_request_all(rq, -ENODEV);
2966			continue;
2967		}
2968
2969		/*
2970		 * rq is already accounted, so use raw insert
2971		 */
2972		if (rq->cmd_flags & (REQ_FLUSH | REQ_FUA))
2973			__elv_add_request(q, rq, ELEVATOR_INSERT_FLUSH);
2974		else
2975			__elv_add_request(q, rq, ELEVATOR_INSERT_SORT_MERGE);
2976
2977		depth++;
 
 
 
 
 
 
2978	}
 
 
 
2979
 
 
 
 
 
2980	/*
2981	 * This drops the queue lock
 
 
 
2982	 */
2983	if (q)
2984		queue_unplugged(q, depth, from_schedule);
2985
2986	local_irq_restore(flags);
 
2987}
2988
 
 
 
 
 
 
 
 
 
 
2989void blk_finish_plug(struct blk_plug *plug)
2990{
2991	blk_flush_plug_list(plug, false);
2992
2993	if (plug == current->plug)
2994		current->plug = NULL;
 
2995}
2996EXPORT_SYMBOL(blk_finish_plug);
2997
 
 
 
 
 
 
 
 
 
 
 
 
2998int __init blk_dev_init(void)
2999{
3000	BUILD_BUG_ON(__REQ_NR_BITS > 8 *
3001			sizeof(((struct request *)0)->cmd_flags));
 
 
 
3002
3003	/* used for unplugging and affects IO latency/throughput - HIGHPRI */
3004	kblockd_workqueue = alloc_workqueue("kblockd",
3005					    WQ_MEM_RECLAIM | WQ_HIGHPRI, 0);
3006	if (!kblockd_workqueue)
3007		panic("Failed to create kblockd\n");
3008
3009	request_cachep = kmem_cache_create("blkdev_requests",
3010			sizeof(struct request), 0, SLAB_PANIC, NULL);
3011
3012	blk_requestq_cachep = kmem_cache_create("blkdev_queue",
3013			sizeof(struct request_queue), 0, SLAB_PANIC, NULL);
3014
3015	return 0;
3016}