xref: /openbmc/linux/block/blk-core.c (revision a2fb4d78)
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/blk-mq.h>
20  #include <linux/highmem.h>
21  #include <linux/mm.h>
22  #include <linux/kernel_stat.h>
23  #include <linux/string.h>
24  #include <linux/init.h>
25  #include <linux/completion.h>
26  #include <linux/slab.h>
27  #include <linux/swap.h>
28  #include <linux/writeback.h>
29  #include <linux/task_io_accounting_ops.h>
30  #include <linux/fault-inject.h>
31  #include <linux/list_sort.h>
32  #include <linux/delay.h>
33  #include <linux/ratelimit.h>
34  #include <linux/pm_runtime.h>
35  
36  #define CREATE_TRACE_POINTS
37  #include <trace/events/block.h>
38  
39  #include "blk.h"
40  #include "blk-cgroup.h"
41  #include "blk-mq.h"
42  
43  EXPORT_TRACEPOINT_SYMBOL_GPL(block_bio_remap);
44  EXPORT_TRACEPOINT_SYMBOL_GPL(block_rq_remap);
45  EXPORT_TRACEPOINT_SYMBOL_GPL(block_bio_complete);
46  EXPORT_TRACEPOINT_SYMBOL_GPL(block_unplug);
47  
48  DEFINE_IDA(blk_queue_ida);
49  
50  /*
51   * For the allocated request tables
52   */
53  struct kmem_cache *request_cachep = NULL;
54  
55  /*
56   * For queue allocation
57   */
58  struct kmem_cache *blk_requestq_cachep;
59  
60  /*
61   * Controlling structure to kblockd
62   */
63  static struct workqueue_struct *kblockd_workqueue;
64  
65  void blk_queue_congestion_threshold(struct request_queue *q)
66  {
67  	int nr;
68  
69  	nr = q->nr_requests - (q->nr_requests / 8) + 1;
70  	if (nr > q->nr_requests)
71  		nr = q->nr_requests;
72  	q->nr_congestion_on = nr;
73  
74  	nr = q->nr_requests - (q->nr_requests / 8) - (q->nr_requests / 16) - 1;
75  	if (nr < 1)
76  		nr = 1;
77  	q->nr_congestion_off = nr;
78  }
79  
80  /**
81   * blk_get_backing_dev_info - get the address of a queue's backing_dev_info
82   * @bdev:	device
83   *
84   * Locates the passed device's request queue and returns the address of its
85   * backing_dev_info
86   *
87   * Will return NULL if the request queue cannot be located.
88   */
89  struct backing_dev_info *blk_get_backing_dev_info(struct block_device *bdev)
90  {
91  	struct backing_dev_info *ret = NULL;
92  	struct request_queue *q = bdev_get_queue(bdev);
93  
94  	if (q)
95  		ret = &q->backing_dev_info;
96  	return ret;
97  }
98  EXPORT_SYMBOL(blk_get_backing_dev_info);
99  
100  void blk_rq_init(struct request_queue *q, struct request *rq)
101  {
102  	memset(rq, 0, sizeof(*rq));
103  
104  	INIT_LIST_HEAD(&rq->queuelist);
105  	INIT_LIST_HEAD(&rq->timeout_list);
106  	rq->cpu = -1;
107  	rq->q = q;
108  	rq->__sector = (sector_t) -1;
109  	INIT_HLIST_NODE(&rq->hash);
110  	RB_CLEAR_NODE(&rq->rb_node);
111  	rq->cmd = rq->__cmd;
112  	rq->cmd_len = BLK_MAX_CDB;
113  	rq->tag = -1;
114  	rq->start_time = jiffies;
115  	set_start_time_ns(rq);
116  	rq->part = NULL;
117  }
118  EXPORT_SYMBOL(blk_rq_init);
119  
120  static void req_bio_endio(struct request *rq, struct bio *bio,
121  			  unsigned int nbytes, int error)
122  {
123  	if (error)
124  		clear_bit(BIO_UPTODATE, &bio->bi_flags);
125  	else if (!test_bit(BIO_UPTODATE, &bio->bi_flags))
126  		error = -EIO;
127  
128  	if (unlikely(rq->cmd_flags & REQ_QUIET))
129  		set_bit(BIO_QUIET, &bio->bi_flags);
130  
131  	bio_advance(bio, nbytes);
132  
133  	/* don't actually finish bio if it's part of flush sequence */
134  	if (bio->bi_iter.bi_size == 0 && !(rq->cmd_flags & REQ_FLUSH_SEQ))
135  		bio_endio(bio, error);
136  }
137  
138  void blk_dump_rq_flags(struct request *rq, char *msg)
139  {
140  	int bit;
141  
142  	printk(KERN_INFO "%s: dev %s: type=%x, flags=%llx\n", msg,
143  		rq->rq_disk ? rq->rq_disk->disk_name : "?", rq->cmd_type,
144  		(unsigned long long) rq->cmd_flags);
145  
146  	printk(KERN_INFO "  sector %llu, nr/cnr %u/%u\n",
147  	       (unsigned long long)blk_rq_pos(rq),
148  	       blk_rq_sectors(rq), blk_rq_cur_sectors(rq));
149  	printk(KERN_INFO "  bio %p, biotail %p, buffer %p, len %u\n",
150  	       rq->bio, rq->biotail, rq->buffer, blk_rq_bytes(rq));
151  
152  	if (rq->cmd_type == REQ_TYPE_BLOCK_PC) {
153  		printk(KERN_INFO "  cdb: ");
154  		for (bit = 0; bit < BLK_MAX_CDB; bit++)
155  			printk("%02x ", rq->cmd[bit]);
156  		printk("\n");
157  	}
158  }
159  EXPORT_SYMBOL(blk_dump_rq_flags);
160  
161  static void blk_delay_work(struct work_struct *work)
162  {
163  	struct request_queue *q;
164  
165  	q = container_of(work, struct request_queue, delay_work.work);
166  	spin_lock_irq(q->queue_lock);
167  	__blk_run_queue(q);
168  	spin_unlock_irq(q->queue_lock);
169  }
170  
171  /**
172   * blk_delay_queue - restart queueing after defined interval
173   * @q:		The &struct request_queue in question
174   * @msecs:	Delay in msecs
175   *
176   * Description:
177   *   Sometimes queueing needs to be postponed for a little while, to allow
178   *   resources to come back. This function will make sure that queueing is
179   *   restarted around the specified time. Queue lock must be held.
180   */
181  void blk_delay_queue(struct request_queue *q, unsigned long msecs)
182  {
183  	if (likely(!blk_queue_dead(q)))
184  		queue_delayed_work(kblockd_workqueue, &q->delay_work,
185  				   msecs_to_jiffies(msecs));
186  }
187  EXPORT_SYMBOL(blk_delay_queue);
188  
189  /**
190   * blk_start_queue - restart a previously stopped queue
191   * @q:    The &struct request_queue in question
192   *
193   * Description:
194   *   blk_start_queue() will clear the stop flag on the queue, and call
195   *   the request_fn for the queue if it was in a stopped state when
196   *   entered. Also see blk_stop_queue(). Queue lock must be held.
197   **/
198  void blk_start_queue(struct request_queue *q)
199  {
200  	WARN_ON(!irqs_disabled());
201  
202  	queue_flag_clear(QUEUE_FLAG_STOPPED, q);
203  	__blk_run_queue(q);
204  }
205  EXPORT_SYMBOL(blk_start_queue);
206  
207  /**
208   * blk_stop_queue - stop a queue
209   * @q:    The &struct request_queue in question
210   *
211   * Description:
212   *   The Linux block layer assumes that a block driver will consume all
213   *   entries on the request queue when the request_fn strategy is called.
214   *   Often this will not happen, because of hardware limitations (queue
215   *   depth settings). If a device driver gets a 'queue full' response,
216   *   or if it simply chooses not to queue more I/O at one point, it can
217   *   call this function to prevent the request_fn from being called until
218   *   the driver has signalled it's ready to go again. This happens by calling
219   *   blk_start_queue() to restart queue operations. Queue lock must be held.
220   **/
221  void blk_stop_queue(struct request_queue *q)
222  {
223  	cancel_delayed_work(&q->delay_work);
224  	queue_flag_set(QUEUE_FLAG_STOPPED, q);
225  }
226  EXPORT_SYMBOL(blk_stop_queue);
227  
228  /**
229   * blk_sync_queue - cancel any pending callbacks on a queue
230   * @q: the queue
231   *
232   * Description:
233   *     The block layer may perform asynchronous callback activity
234   *     on a queue, such as calling the unplug function after a timeout.
235   *     A block device may call blk_sync_queue to ensure that any
236   *     such activity is cancelled, thus allowing it to release resources
237   *     that the callbacks might use. The caller must already have made sure
238   *     that its ->make_request_fn will not re-add plugging prior to calling
239   *     this function.
240   *
241   *     This function does not cancel any asynchronous activity arising
242   *     out of elevator or throttling code. That would require elevaotor_exit()
243   *     and blkcg_exit_queue() to be called with queue lock initialized.
244   *
245   */
246  void blk_sync_queue(struct request_queue *q)
247  {
248  	del_timer_sync(&q->timeout);
249  
250  	if (q->mq_ops) {
251  		struct blk_mq_hw_ctx *hctx;
252  		int i;
253  
254  		queue_for_each_hw_ctx(q, hctx, i)
255  			cancel_delayed_work_sync(&hctx->delayed_work);
256  	} else {
257  		cancel_delayed_work_sync(&q->delay_work);
258  	}
259  }
260  EXPORT_SYMBOL(blk_sync_queue);
261  
262  /**
263   * __blk_run_queue_uncond - run a queue whether or not it has been stopped
264   * @q:	The queue to run
265   *
266   * Description:
267   *    Invoke request handling on a queue if there are any pending requests.
268   *    May be used to restart request handling after a request has completed.
269   *    This variant runs the queue whether or not the queue has been
270   *    stopped. Must be called with the queue lock held and interrupts
271   *    disabled. See also @blk_run_queue.
272   */
273  inline void __blk_run_queue_uncond(struct request_queue *q)
274  {
275  	if (unlikely(blk_queue_dead(q)))
276  		return;
277  
278  	/*
279  	 * Some request_fn implementations, e.g. scsi_request_fn(), unlock
280  	 * the queue lock internally. As a result multiple threads may be
281  	 * running such a request function concurrently. Keep track of the
282  	 * number of active request_fn invocations such that blk_drain_queue()
283  	 * can wait until all these request_fn calls have finished.
284  	 */
285  	q->request_fn_active++;
286  	q->request_fn(q);
287  	q->request_fn_active--;
288  }
289  
290  /**
291   * __blk_run_queue - run a single device queue
292   * @q:	The queue to run
293   *
294   * Description:
295   *    See @blk_run_queue. This variant must be called with the queue lock
296   *    held and interrupts disabled.
297   */
298  void __blk_run_queue(struct request_queue *q)
299  {
300  	if (unlikely(blk_queue_stopped(q)))
301  		return;
302  
303  	__blk_run_queue_uncond(q);
304  }
305  EXPORT_SYMBOL(__blk_run_queue);
306  
307  /**
308   * blk_run_queue_async - run a single device queue in workqueue context
309   * @q:	The queue to run
310   *
311   * Description:
312   *    Tells kblockd to perform the equivalent of @blk_run_queue on behalf
313   *    of us. The caller must hold the queue lock.
314   */
315  void blk_run_queue_async(struct request_queue *q)
316  {
317  	if (likely(!blk_queue_stopped(q) && !blk_queue_dead(q)))
318  		mod_delayed_work(kblockd_workqueue, &q->delay_work, 0);
319  }
320  EXPORT_SYMBOL(blk_run_queue_async);
321  
322  /**
323   * blk_run_queue - run a single device queue
324   * @q: The queue to run
325   *
326   * Description:
327   *    Invoke request handling on this queue, if it has pending work to do.
328   *    May be used to restart queueing when a request has completed.
329   */
330  void blk_run_queue(struct request_queue *q)
331  {
332  	unsigned long flags;
333  
334  	spin_lock_irqsave(q->queue_lock, flags);
335  	__blk_run_queue(q);
336  	spin_unlock_irqrestore(q->queue_lock, flags);
337  }
338  EXPORT_SYMBOL(blk_run_queue);
339  
340  void blk_put_queue(struct request_queue *q)
341  {
342  	kobject_put(&q->kobj);
343  }
344  EXPORT_SYMBOL(blk_put_queue);
345  
346  /**
347   * __blk_drain_queue - drain requests from request_queue
348   * @q: queue to drain
349   * @drain_all: whether to drain all requests or only the ones w/ ELVPRIV
350   *
351   * Drain requests from @q.  If @drain_all is set, all requests are drained.
352   * If not, only ELVPRIV requests are drained.  The caller is responsible
353   * for ensuring that no new requests which need to be drained are queued.
354   */
355  static void __blk_drain_queue(struct request_queue *q, bool drain_all)
356  	__releases(q->queue_lock)
357  	__acquires(q->queue_lock)
358  {
359  	int i;
360  
361  	lockdep_assert_held(q->queue_lock);
362  
363  	while (true) {
364  		bool drain = false;
365  
366  		/*
367  		 * The caller might be trying to drain @q before its
368  		 * elevator is initialized.
369  		 */
370  		if (q->elevator)
371  			elv_drain_elevator(q);
372  
373  		blkcg_drain_queue(q);
374  
375  		/*
376  		 * This function might be called on a queue which failed
377  		 * driver init after queue creation or is not yet fully
378  		 * active yet.  Some drivers (e.g. fd and loop) get unhappy
379  		 * in such cases.  Kick queue iff dispatch queue has
380  		 * something on it and @q has request_fn set.
381  		 */
382  		if (!list_empty(&q->queue_head) && q->request_fn)
383  			__blk_run_queue(q);
384  
385  		drain |= q->nr_rqs_elvpriv;
386  		drain |= q->request_fn_active;
387  
388  		/*
389  		 * Unfortunately, requests are queued at and tracked from
390  		 * multiple places and there's no single counter which can
391  		 * be drained.  Check all the queues and counters.
392  		 */
393  		if (drain_all) {
394  			drain |= !list_empty(&q->queue_head);
395  			for (i = 0; i < 2; i++) {
396  				drain |= q->nr_rqs[i];
397  				drain |= q->in_flight[i];
398  				drain |= !list_empty(&q->flush_queue[i]);
399  			}
400  		}
401  
402  		if (!drain)
403  			break;
404  
405  		spin_unlock_irq(q->queue_lock);
406  
407  		msleep(10);
408  
409  		spin_lock_irq(q->queue_lock);
410  	}
411  
412  	/*
413  	 * With queue marked dead, any woken up waiter will fail the
414  	 * allocation path, so the wakeup chaining is lost and we're
415  	 * left with hung waiters. We need to wake up those waiters.
416  	 */
417  	if (q->request_fn) {
418  		struct request_list *rl;
419  
420  		blk_queue_for_each_rl(rl, q)
421  			for (i = 0; i < ARRAY_SIZE(rl->wait); i++)
422  				wake_up_all(&rl->wait[i]);
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   */
436  void 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  		spin_lock_irq(q->queue_lock);
447  		__blk_drain_queue(q, false);
448  		spin_unlock_irq(q->queue_lock);
449  
450  		/* ensure blk_queue_bypass() is %true inside RCU read lock */
451  		synchronize_rcu();
452  	}
453  }
454  EXPORT_SYMBOL_GPL(blk_queue_bypass_start);
455  
456  /**
457   * blk_queue_bypass_end - leave queue bypass mode
458   * @q: queue of interest
459   *
460   * Leave bypass mode and restore the normal queueing behavior.
461   */
462  void blk_queue_bypass_end(struct request_queue *q)
463  {
464  	spin_lock_irq(q->queue_lock);
465  	if (!--q->bypass_depth)
466  		queue_flag_clear(QUEUE_FLAG_BYPASS, q);
467  	WARN_ON_ONCE(q->bypass_depth < 0);
468  	spin_unlock_irq(q->queue_lock);
469  }
470  EXPORT_SYMBOL_GPL(blk_queue_bypass_end);
471  
472  /**
473   * blk_cleanup_queue - shutdown a request queue
474   * @q: request queue to shutdown
475   *
476   * Mark @q DYING, drain all pending requests, mark @q DEAD, destroy and
477   * put it.  All future requests will be failed immediately with -ENODEV.
478   */
479  void blk_cleanup_queue(struct request_queue *q)
480  {
481  	spinlock_t *lock = q->queue_lock;
482  
483  	/* mark @q DYING, no new request or merges will be allowed afterwards */
484  	mutex_lock(&q->sysfs_lock);
485  	queue_flag_set_unlocked(QUEUE_FLAG_DYING, q);
486  	spin_lock_irq(lock);
487  
488  	/*
489  	 * A dying queue is permanently in bypass mode till released.  Note
490  	 * that, unlike blk_queue_bypass_start(), we aren't performing
491  	 * synchronize_rcu() after entering bypass mode to avoid the delay
492  	 * as some drivers create and destroy a lot of queues while
493  	 * probing.  This is still safe because blk_release_queue() will be
494  	 * called only after the queue refcnt drops to zero and nothing,
495  	 * RCU or not, would be traversing the queue by then.
496  	 */
497  	q->bypass_depth++;
498  	queue_flag_set(QUEUE_FLAG_BYPASS, q);
499  
500  	queue_flag_set(QUEUE_FLAG_NOMERGES, q);
501  	queue_flag_set(QUEUE_FLAG_NOXMERGES, q);
502  	queue_flag_set(QUEUE_FLAG_DYING, q);
503  	spin_unlock_irq(lock);
504  	mutex_unlock(&q->sysfs_lock);
505  
506  	/*
507  	 * Drain all requests queued before DYING marking. Set DEAD flag to
508  	 * prevent that q->request_fn() gets invoked after draining finished.
509  	 */
510  	if (q->mq_ops) {
511  		blk_mq_drain_queue(q);
512  		spin_lock_irq(lock);
513  	} else {
514  		spin_lock_irq(lock);
515  		__blk_drain_queue(q, true);
516  	}
517  	queue_flag_set(QUEUE_FLAG_DEAD, q);
518  	spin_unlock_irq(lock);
519  
520  	/* @q won't process any more request, flush async actions */
521  	del_timer_sync(&q->backing_dev_info.laptop_mode_wb_timer);
522  	blk_sync_queue(q);
523  
524  	spin_lock_irq(lock);
525  	if (q->queue_lock != &q->__queue_lock)
526  		q->queue_lock = &q->__queue_lock;
527  	spin_unlock_irq(lock);
528  
529  	/* @q is and will stay empty, shutdown and put */
530  	blk_put_queue(q);
531  }
532  EXPORT_SYMBOL(blk_cleanup_queue);
533  
534  int blk_init_rl(struct request_list *rl, struct request_queue *q,
535  		gfp_t gfp_mask)
536  {
537  	if (unlikely(rl->rq_pool))
538  		return 0;
539  
540  	rl->q = q;
541  	rl->count[BLK_RW_SYNC] = rl->count[BLK_RW_ASYNC] = 0;
542  	rl->starved[BLK_RW_SYNC] = rl->starved[BLK_RW_ASYNC] = 0;
543  	init_waitqueue_head(&rl->wait[BLK_RW_SYNC]);
544  	init_waitqueue_head(&rl->wait[BLK_RW_ASYNC]);
545  
546  	rl->rq_pool = mempool_create_node(BLKDEV_MIN_RQ, mempool_alloc_slab,
547  					  mempool_free_slab, request_cachep,
548  					  gfp_mask, q->node);
549  	if (!rl->rq_pool)
550  		return -ENOMEM;
551  
552  	return 0;
553  }
554  
555  void blk_exit_rl(struct request_list *rl)
556  {
557  	if (rl->rq_pool)
558  		mempool_destroy(rl->rq_pool);
559  }
560  
561  struct request_queue *blk_alloc_queue(gfp_t gfp_mask)
562  {
563  	return blk_alloc_queue_node(gfp_mask, NUMA_NO_NODE);
564  }
565  EXPORT_SYMBOL(blk_alloc_queue);
566  
567  struct request_queue *blk_alloc_queue_node(gfp_t gfp_mask, int node_id)
568  {
569  	struct request_queue *q;
570  	int err;
571  
572  	q = kmem_cache_alloc_node(blk_requestq_cachep,
573  				gfp_mask | __GFP_ZERO, node_id);
574  	if (!q)
575  		return NULL;
576  
577  	if (percpu_counter_init(&q->mq_usage_counter, 0))
578  		goto fail_q;
579  
580  	q->id = ida_simple_get(&blk_queue_ida, 0, 0, gfp_mask);
581  	if (q->id < 0)
582  		goto fail_c;
583  
584  	q->backing_dev_info.ra_pages =
585  			(VM_MAX_READAHEAD * 1024) / PAGE_CACHE_SIZE;
586  	q->backing_dev_info.state = 0;
587  	q->backing_dev_info.capabilities = BDI_CAP_MAP_COPY;
588  	q->backing_dev_info.name = "block";
589  	q->node = node_id;
590  
591  	err = bdi_init(&q->backing_dev_info);
592  	if (err)
593  		goto fail_id;
594  
595  	setup_timer(&q->backing_dev_info.laptop_mode_wb_timer,
596  		    laptop_mode_timer_fn, (unsigned long) q);
597  	setup_timer(&q->timeout, blk_rq_timed_out_timer, (unsigned long) q);
598  	INIT_LIST_HEAD(&q->queue_head);
599  	INIT_LIST_HEAD(&q->timeout_list);
600  	INIT_LIST_HEAD(&q->icq_list);
601  #ifdef CONFIG_BLK_CGROUP
602  	INIT_LIST_HEAD(&q->blkg_list);
603  #endif
604  	INIT_LIST_HEAD(&q->flush_queue[0]);
605  	INIT_LIST_HEAD(&q->flush_queue[1]);
606  	INIT_LIST_HEAD(&q->flush_data_in_flight);
607  	INIT_DELAYED_WORK(&q->delay_work, blk_delay_work);
608  
609  	kobject_init(&q->kobj, &blk_queue_ktype);
610  
611  	mutex_init(&q->sysfs_lock);
612  	spin_lock_init(&q->__queue_lock);
613  
614  	/*
615  	 * By default initialize queue_lock to internal lock and driver can
616  	 * override it later if need be.
617  	 */
618  	q->queue_lock = &q->__queue_lock;
619  
620  	/*
621  	 * A queue starts its life with bypass turned on to avoid
622  	 * unnecessary bypass on/off overhead and nasty surprises during
623  	 * init.  The initial bypass will be finished when the queue is
624  	 * registered by blk_register_queue().
625  	 */
626  	q->bypass_depth = 1;
627  	__set_bit(QUEUE_FLAG_BYPASS, &q->queue_flags);
628  
629  	init_waitqueue_head(&q->mq_freeze_wq);
630  
631  	if (blkcg_init_queue(q))
632  		goto fail_bdi;
633  
634  	return q;
635  
636  fail_bdi:
637  	bdi_destroy(&q->backing_dev_info);
638  fail_id:
639  	ida_simple_remove(&blk_queue_ida, q->id);
640  fail_c:
641  	percpu_counter_destroy(&q->mq_usage_counter);
642  fail_q:
643  	kmem_cache_free(blk_requestq_cachep, q);
644  	return NULL;
645  }
646  EXPORT_SYMBOL(blk_alloc_queue_node);
647  
648  /**
649   * blk_init_queue  - prepare a request queue for use with a block device
650   * @rfn:  The function to be called to process requests that have been
651   *        placed on the queue.
652   * @lock: Request queue spin lock
653   *
654   * Description:
655   *    If a block device wishes to use the standard request handling procedures,
656   *    which sorts requests and coalesces adjacent requests, then it must
657   *    call blk_init_queue().  The function @rfn will be called when there
658   *    are requests on the queue that need to be processed.  If the device
659   *    supports plugging, then @rfn may not be called immediately when requests
660   *    are available on the queue, but may be called at some time later instead.
661   *    Plugged queues are generally unplugged when a buffer belonging to one
662   *    of the requests on the queue is needed, or due to memory pressure.
663   *
664   *    @rfn is not required, or even expected, to remove all requests off the
665   *    queue, but only as many as it can handle at a time.  If it does leave
666   *    requests on the queue, it is responsible for arranging that the requests
667   *    get dealt with eventually.
668   *
669   *    The queue spin lock must be held while manipulating the requests on the
670   *    request queue; this lock will be taken also from interrupt context, so irq
671   *    disabling is needed for it.
672   *
673   *    Function returns a pointer to the initialized request queue, or %NULL if
674   *    it didn't succeed.
675   *
676   * Note:
677   *    blk_init_queue() must be paired with a blk_cleanup_queue() call
678   *    when the block device is deactivated (such as at module unload).
679   **/
680  
681  struct request_queue *blk_init_queue(request_fn_proc *rfn, spinlock_t *lock)
682  {
683  	return blk_init_queue_node(rfn, lock, NUMA_NO_NODE);
684  }
685  EXPORT_SYMBOL(blk_init_queue);
686  
687  struct request_queue *
688  blk_init_queue_node(request_fn_proc *rfn, spinlock_t *lock, int node_id)
689  {
690  	struct request_queue *uninit_q, *q;
691  
692  	uninit_q = blk_alloc_queue_node(GFP_KERNEL, node_id);
693  	if (!uninit_q)
694  		return NULL;
695  
696  	q = blk_init_allocated_queue(uninit_q, rfn, lock);
697  	if (!q)
698  		blk_cleanup_queue(uninit_q);
699  
700  	return q;
701  }
702  EXPORT_SYMBOL(blk_init_queue_node);
703  
704  struct request_queue *
705  blk_init_allocated_queue(struct request_queue *q, request_fn_proc *rfn,
706  			 spinlock_t *lock)
707  {
708  	if (!q)
709  		return NULL;
710  
711  	q->flush_rq = kzalloc(sizeof(struct request), GFP_KERNEL);
712  	if (!q->flush_rq)
713  		return NULL;
714  
715  	if (blk_init_rl(&q->root_rl, q, GFP_KERNEL))
716  		goto fail;
717  
718  	q->request_fn		= rfn;
719  	q->prep_rq_fn		= NULL;
720  	q->unprep_rq_fn		= NULL;
721  	q->queue_flags		|= QUEUE_FLAG_DEFAULT;
722  
723  	/* Override internal queue lock with supplied lock pointer */
724  	if (lock)
725  		q->queue_lock		= lock;
726  
727  	/*
728  	 * This also sets hw/phys segments, boundary and size
729  	 */
730  	blk_queue_make_request(q, blk_queue_bio);
731  
732  	q->sg_reserved_size = INT_MAX;
733  
734  	/* Protect q->elevator from elevator_change */
735  	mutex_lock(&q->sysfs_lock);
736  
737  	/* init elevator */
738  	if (elevator_init(q, NULL)) {
739  		mutex_unlock(&q->sysfs_lock);
740  		goto fail;
741  	}
742  
743  	mutex_unlock(&q->sysfs_lock);
744  
745  	return q;
746  
747  fail:
748  	kfree(q->flush_rq);
749  	return NULL;
750  }
751  EXPORT_SYMBOL(blk_init_allocated_queue);
752  
753  bool blk_get_queue(struct request_queue *q)
754  {
755  	if (likely(!blk_queue_dying(q))) {
756  		__blk_get_queue(q);
757  		return true;
758  	}
759  
760  	return false;
761  }
762  EXPORT_SYMBOL(blk_get_queue);
763  
764  static inline void blk_free_request(struct request_list *rl, struct request *rq)
765  {
766  	if (rq->cmd_flags & REQ_ELVPRIV) {
767  		elv_put_request(rl->q, rq);
768  		if (rq->elv.icq)
769  			put_io_context(rq->elv.icq->ioc);
770  	}
771  
772  	mempool_free(rq, rl->rq_pool);
773  }
774  
775  /*
776   * ioc_batching returns true if the ioc is a valid batching request and
777   * should be given priority access to a request.
778   */
779  static inline int ioc_batching(struct request_queue *q, struct io_context *ioc)
780  {
781  	if (!ioc)
782  		return 0;
783  
784  	/*
785  	 * Make sure the process is able to allocate at least 1 request
786  	 * even if the batch times out, otherwise we could theoretically
787  	 * lose wakeups.
788  	 */
789  	return ioc->nr_batch_requests == q->nr_batching ||
790  		(ioc->nr_batch_requests > 0
791  		&& time_before(jiffies, ioc->last_waited + BLK_BATCH_TIME));
792  }
793  
794  /*
795   * ioc_set_batching sets ioc to be a new "batcher" if it is not one. This
796   * will cause the process to be a "batcher" on all queues in the system. This
797   * is the behaviour we want though - once it gets a wakeup it should be given
798   * a nice run.
799   */
800  static void ioc_set_batching(struct request_queue *q, struct io_context *ioc)
801  {
802  	if (!ioc || ioc_batching(q, ioc))
803  		return;
804  
805  	ioc->nr_batch_requests = q->nr_batching;
806  	ioc->last_waited = jiffies;
807  }
808  
809  static void __freed_request(struct request_list *rl, int sync)
810  {
811  	struct request_queue *q = rl->q;
812  
813  	/*
814  	 * bdi isn't aware of blkcg yet.  As all async IOs end up root
815  	 * blkcg anyway, just use root blkcg state.
816  	 */
817  	if (rl == &q->root_rl &&
818  	    rl->count[sync] < queue_congestion_off_threshold(q))
819  		blk_clear_queue_congested(q, sync);
820  
821  	if (rl->count[sync] + 1 <= q->nr_requests) {
822  		if (waitqueue_active(&rl->wait[sync]))
823  			wake_up(&rl->wait[sync]);
824  
825  		blk_clear_rl_full(rl, sync);
826  	}
827  }
828  
829  /*
830   * A request has just been released.  Account for it, update the full and
831   * congestion status, wake up any waiters.   Called under q->queue_lock.
832   */
833  static void freed_request(struct request_list *rl, unsigned int flags)
834  {
835  	struct request_queue *q = rl->q;
836  	int sync = rw_is_sync(flags);
837  
838  	q->nr_rqs[sync]--;
839  	rl->count[sync]--;
840  	if (flags & REQ_ELVPRIV)
841  		q->nr_rqs_elvpriv--;
842  
843  	__freed_request(rl, sync);
844  
845  	if (unlikely(rl->starved[sync ^ 1]))
846  		__freed_request(rl, sync ^ 1);
847  }
848  
849  /*
850   * Determine if elevator data should be initialized when allocating the
851   * request associated with @bio.
852   */
853  static bool blk_rq_should_init_elevator(struct bio *bio)
854  {
855  	if (!bio)
856  		return true;
857  
858  	/*
859  	 * Flush requests do not use the elevator so skip initialization.
860  	 * This allows a request to share the flush and elevator data.
861  	 */
862  	if (bio->bi_rw & (REQ_FLUSH | REQ_FUA))
863  		return false;
864  
865  	return true;
866  }
867  
868  /**
869   * rq_ioc - determine io_context for request allocation
870   * @bio: request being allocated is for this bio (can be %NULL)
871   *
872   * Determine io_context to use for request allocation for @bio.  May return
873   * %NULL if %current->io_context doesn't exist.
874   */
875  static struct io_context *rq_ioc(struct bio *bio)
876  {
877  #ifdef CONFIG_BLK_CGROUP
878  	if (bio && bio->bi_ioc)
879  		return bio->bi_ioc;
880  #endif
881  	return current->io_context;
882  }
883  
884  /**
885   * __get_request - get a free request
886   * @rl: request list to allocate from
887   * @rw_flags: RW and SYNC flags
888   * @bio: bio to allocate request for (can be %NULL)
889   * @gfp_mask: allocation mask
890   *
891   * Get a free request from @q.  This function may fail under memory
892   * pressure or if @q is dead.
893   *
894   * Must be callled with @q->queue_lock held and,
895   * Returns %NULL on failure, with @q->queue_lock held.
896   * Returns !%NULL on success, with @q->queue_lock *not held*.
897   */
898  static struct request *__get_request(struct request_list *rl, int rw_flags,
899  				     struct bio *bio, gfp_t gfp_mask)
900  {
901  	struct request_queue *q = rl->q;
902  	struct request *rq;
903  	struct elevator_type *et = q->elevator->type;
904  	struct io_context *ioc = rq_ioc(bio);
905  	struct io_cq *icq = NULL;
906  	const bool is_sync = rw_is_sync(rw_flags) != 0;
907  	int may_queue;
908  
909  	if (unlikely(blk_queue_dying(q)))
910  		return NULL;
911  
912  	may_queue = elv_may_queue(q, rw_flags);
913  	if (may_queue == ELV_MQUEUE_NO)
914  		goto rq_starved;
915  
916  	if (rl->count[is_sync]+1 >= queue_congestion_on_threshold(q)) {
917  		if (rl->count[is_sync]+1 >= q->nr_requests) {
918  			/*
919  			 * The queue will fill after this allocation, so set
920  			 * it as full, and mark this process as "batching".
921  			 * This process will be allowed to complete a batch of
922  			 * requests, others will be blocked.
923  			 */
924  			if (!blk_rl_full(rl, is_sync)) {
925  				ioc_set_batching(q, ioc);
926  				blk_set_rl_full(rl, is_sync);
927  			} else {
928  				if (may_queue != ELV_MQUEUE_MUST
929  						&& !ioc_batching(q, ioc)) {
930  					/*
931  					 * The queue is full and the allocating
932  					 * process is not a "batcher", and not
933  					 * exempted by the IO scheduler
934  					 */
935  					return NULL;
936  				}
937  			}
938  		}
939  		/*
940  		 * bdi isn't aware of blkcg yet.  As all async IOs end up
941  		 * root blkcg anyway, just use root blkcg state.
942  		 */
943  		if (rl == &q->root_rl)
944  			blk_set_queue_congested(q, is_sync);
945  	}
946  
947  	/*
948  	 * Only allow batching queuers to allocate up to 50% over the defined
949  	 * limit of requests, otherwise we could have thousands of requests
950  	 * allocated with any setting of ->nr_requests
951  	 */
952  	if (rl->count[is_sync] >= (3 * q->nr_requests / 2))
953  		return NULL;
954  
955  	q->nr_rqs[is_sync]++;
956  	rl->count[is_sync]++;
957  	rl->starved[is_sync] = 0;
958  
959  	/*
960  	 * Decide whether the new request will be managed by elevator.  If
961  	 * so, mark @rw_flags and increment elvpriv.  Non-zero elvpriv will
962  	 * prevent the current elevator from being destroyed until the new
963  	 * request is freed.  This guarantees icq's won't be destroyed and
964  	 * makes creating new ones safe.
965  	 *
966  	 * Also, lookup icq while holding queue_lock.  If it doesn't exist,
967  	 * it will be created after releasing queue_lock.
968  	 */
969  	if (blk_rq_should_init_elevator(bio) && !blk_queue_bypass(q)) {
970  		rw_flags |= REQ_ELVPRIV;
971  		q->nr_rqs_elvpriv++;
972  		if (et->icq_cache && ioc)
973  			icq = ioc_lookup_icq(ioc, q);
974  	}
975  
976  	if (blk_queue_io_stat(q))
977  		rw_flags |= REQ_IO_STAT;
978  	spin_unlock_irq(q->queue_lock);
979  
980  	/* allocate and init request */
981  	rq = mempool_alloc(rl->rq_pool, gfp_mask);
982  	if (!rq)
983  		goto fail_alloc;
984  
985  	blk_rq_init(q, rq);
986  	blk_rq_set_rl(rq, rl);
987  	rq->cmd_flags = rw_flags | REQ_ALLOCED;
988  
989  	/* init elvpriv */
990  	if (rw_flags & REQ_ELVPRIV) {
991  		if (unlikely(et->icq_cache && !icq)) {
992  			if (ioc)
993  				icq = ioc_create_icq(ioc, q, gfp_mask);
994  			if (!icq)
995  				goto fail_elvpriv;
996  		}
997  
998  		rq->elv.icq = icq;
999  		if (unlikely(elv_set_request(q, rq, bio, gfp_mask)))
1000  			goto fail_elvpriv;
1001  
1002  		/* @rq->elv.icq holds io_context until @rq is freed */
1003  		if (icq)
1004  			get_io_context(icq->ioc);
1005  	}
1006  out:
1007  	/*
1008  	 * ioc may be NULL here, and ioc_batching will be false. That's
1009  	 * OK, if the queue is under the request limit then requests need
1010  	 * not count toward the nr_batch_requests limit. There will always
1011  	 * be some limit enforced by BLK_BATCH_TIME.
1012  	 */
1013  	if (ioc_batching(q, ioc))
1014  		ioc->nr_batch_requests--;
1015  
1016  	trace_block_getrq(q, bio, rw_flags & 1);
1017  	return rq;
1018  
1019  fail_elvpriv:
1020  	/*
1021  	 * elvpriv init failed.  ioc, icq and elvpriv aren't mempool backed
1022  	 * and may fail indefinitely under memory pressure and thus
1023  	 * shouldn't stall IO.  Treat this request as !elvpriv.  This will
1024  	 * disturb iosched and blkcg but weird is bettern than dead.
1025  	 */
1026  	printk_ratelimited(KERN_WARNING "%s: request aux data allocation failed, iosched may be disturbed\n",
1027  			   dev_name(q->backing_dev_info.dev));
1028  
1029  	rq->cmd_flags &= ~REQ_ELVPRIV;
1030  	rq->elv.icq = NULL;
1031  
1032  	spin_lock_irq(q->queue_lock);
1033  	q->nr_rqs_elvpriv--;
1034  	spin_unlock_irq(q->queue_lock);
1035  	goto out;
1036  
1037  fail_alloc:
1038  	/*
1039  	 * Allocation failed presumably due to memory. Undo anything we
1040  	 * might have messed up.
1041  	 *
1042  	 * Allocating task should really be put onto the front of the wait
1043  	 * queue, but this is pretty rare.
1044  	 */
1045  	spin_lock_irq(q->queue_lock);
1046  	freed_request(rl, rw_flags);
1047  
1048  	/*
1049  	 * in the very unlikely event that allocation failed and no
1050  	 * requests for this direction was pending, mark us starved so that
1051  	 * freeing of a request in the other direction will notice
1052  	 * us. another possible fix would be to split the rq mempool into
1053  	 * READ and WRITE
1054  	 */
1055  rq_starved:
1056  	if (unlikely(rl->count[is_sync] == 0))
1057  		rl->starved[is_sync] = 1;
1058  	return NULL;
1059  }
1060  
1061  /**
1062   * get_request - get a free request
1063   * @q: request_queue to allocate request from
1064   * @rw_flags: RW and SYNC flags
1065   * @bio: bio to allocate request for (can be %NULL)
1066   * @gfp_mask: allocation mask
1067   *
1068   * Get a free request from @q.  If %__GFP_WAIT is set in @gfp_mask, this
1069   * function keeps retrying under memory pressure and fails iff @q is dead.
1070   *
1071   * Must be callled with @q->queue_lock held and,
1072   * Returns %NULL on failure, with @q->queue_lock held.
1073   * Returns !%NULL on success, with @q->queue_lock *not held*.
1074   */
1075  static struct request *get_request(struct request_queue *q, int rw_flags,
1076  				   struct bio *bio, gfp_t gfp_mask)
1077  {
1078  	const bool is_sync = rw_is_sync(rw_flags) != 0;
1079  	DEFINE_WAIT(wait);
1080  	struct request_list *rl;
1081  	struct request *rq;
1082  
1083  	rl = blk_get_rl(q, bio);	/* transferred to @rq on success */
1084  retry:
1085  	rq = __get_request(rl, rw_flags, bio, gfp_mask);
1086  	if (rq)
1087  		return rq;
1088  
1089  	if (!(gfp_mask & __GFP_WAIT) || unlikely(blk_queue_dying(q))) {
1090  		blk_put_rl(rl);
1091  		return NULL;
1092  	}
1093  
1094  	/* wait on @rl and retry */
1095  	prepare_to_wait_exclusive(&rl->wait[is_sync], &wait,
1096  				  TASK_UNINTERRUPTIBLE);
1097  
1098  	trace_block_sleeprq(q, bio, rw_flags & 1);
1099  
1100  	spin_unlock_irq(q->queue_lock);
1101  	io_schedule();
1102  
1103  	/*
1104  	 * After sleeping, we become a "batching" process and will be able
1105  	 * to allocate at least one request, and up to a big batch of them
1106  	 * for a small period time.  See ioc_batching, ioc_set_batching
1107  	 */
1108  	ioc_set_batching(q, current->io_context);
1109  
1110  	spin_lock_irq(q->queue_lock);
1111  	finish_wait(&rl->wait[is_sync], &wait);
1112  
1113  	goto retry;
1114  }
1115  
1116  static struct request *blk_old_get_request(struct request_queue *q, int rw,
1117  		gfp_t gfp_mask)
1118  {
1119  	struct request *rq;
1120  
1121  	BUG_ON(rw != READ && rw != WRITE);
1122  
1123  	/* create ioc upfront */
1124  	create_io_context(gfp_mask, q->node);
1125  
1126  	spin_lock_irq(q->queue_lock);
1127  	rq = get_request(q, rw, NULL, gfp_mask);
1128  	if (!rq)
1129  		spin_unlock_irq(q->queue_lock);
1130  	/* q->queue_lock is unlocked at this point */
1131  
1132  	return rq;
1133  }
1134  
1135  struct request *blk_get_request(struct request_queue *q, int rw, gfp_t gfp_mask)
1136  {
1137  	if (q->mq_ops)
1138  		return blk_mq_alloc_request(q, rw, gfp_mask);
1139  	else
1140  		return blk_old_get_request(q, rw, gfp_mask);
1141  }
1142  EXPORT_SYMBOL(blk_get_request);
1143  
1144  /**
1145   * blk_make_request - given a bio, allocate a corresponding struct request.
1146   * @q: target request queue
1147   * @bio:  The bio describing the memory mappings that will be submitted for IO.
1148   *        It may be a chained-bio properly constructed by block/bio layer.
1149   * @gfp_mask: gfp flags to be used for memory allocation
1150   *
1151   * blk_make_request is the parallel of generic_make_request for BLOCK_PC
1152   * type commands. Where the struct request needs to be farther initialized by
1153   * the caller. It is passed a &struct bio, which describes the memory info of
1154   * the I/O transfer.
1155   *
1156   * The caller of blk_make_request must make sure that bi_io_vec
1157   * are set to describe the memory buffers. That bio_data_dir() will return
1158   * the needed direction of the request. (And all bio's in the passed bio-chain
1159   * are properly set accordingly)
1160   *
1161   * If called under none-sleepable conditions, mapped bio buffers must not
1162   * need bouncing, by calling the appropriate masked or flagged allocator,
1163   * suitable for the target device. Otherwise the call to blk_queue_bounce will
1164   * BUG.
1165   *
1166   * WARNING: When allocating/cloning a bio-chain, careful consideration should be
1167   * given to how you allocate bios. In particular, you cannot use __GFP_WAIT for
1168   * anything but the first bio in the chain. Otherwise you risk waiting for IO
1169   * completion of a bio that hasn't been submitted yet, thus resulting in a
1170   * deadlock. Alternatively bios should be allocated using bio_kmalloc() instead
1171   * of bio_alloc(), as that avoids the mempool deadlock.
1172   * If possible a big IO should be split into smaller parts when allocation
1173   * fails. Partial allocation should not be an error, or you risk a live-lock.
1174   */
1175  struct request *blk_make_request(struct request_queue *q, struct bio *bio,
1176  				 gfp_t gfp_mask)
1177  {
1178  	struct request *rq = blk_get_request(q, bio_data_dir(bio), gfp_mask);
1179  
1180  	if (unlikely(!rq))
1181  		return ERR_PTR(-ENOMEM);
1182  
1183  	for_each_bio(bio) {
1184  		struct bio *bounce_bio = bio;
1185  		int ret;
1186  
1187  		blk_queue_bounce(q, &bounce_bio);
1188  		ret = blk_rq_append_bio(q, rq, bounce_bio);
1189  		if (unlikely(ret)) {
1190  			blk_put_request(rq);
1191  			return ERR_PTR(ret);
1192  		}
1193  	}
1194  
1195  	return rq;
1196  }
1197  EXPORT_SYMBOL(blk_make_request);
1198  
1199  /**
1200   * blk_requeue_request - put a request back on queue
1201   * @q:		request queue where request should be inserted
1202   * @rq:		request to be inserted
1203   *
1204   * Description:
1205   *    Drivers often keep queueing requests until the hardware cannot accept
1206   *    more, when that condition happens we need to put the request back
1207   *    on the queue. Must be called with queue lock held.
1208   */
1209  void blk_requeue_request(struct request_queue *q, struct request *rq)
1210  {
1211  	blk_delete_timer(rq);
1212  	blk_clear_rq_complete(rq);
1213  	trace_block_rq_requeue(q, rq);
1214  
1215  	if (blk_rq_tagged(rq))
1216  		blk_queue_end_tag(q, rq);
1217  
1218  	BUG_ON(blk_queued_rq(rq));
1219  
1220  	elv_requeue_request(q, rq);
1221  }
1222  EXPORT_SYMBOL(blk_requeue_request);
1223  
1224  static void add_acct_request(struct request_queue *q, struct request *rq,
1225  			     int where)
1226  {
1227  	blk_account_io_start(rq, true);
1228  	__elv_add_request(q, rq, where);
1229  }
1230  
1231  static void part_round_stats_single(int cpu, struct hd_struct *part,
1232  				    unsigned long now)
1233  {
1234  	if (now == part->stamp)
1235  		return;
1236  
1237  	if (part_in_flight(part)) {
1238  		__part_stat_add(cpu, part, time_in_queue,
1239  				part_in_flight(part) * (now - part->stamp));
1240  		__part_stat_add(cpu, part, io_ticks, (now - part->stamp));
1241  	}
1242  	part->stamp = now;
1243  }
1244  
1245  /**
1246   * part_round_stats() - Round off the performance stats on a struct disk_stats.
1247   * @cpu: cpu number for stats access
1248   * @part: target partition
1249   *
1250   * The average IO queue length and utilisation statistics are maintained
1251   * by observing the current state of the queue length and the amount of
1252   * time it has been in this state for.
1253   *
1254   * Normally, that accounting is done on IO completion, but that can result
1255   * in more than a second's worth of IO being accounted for within any one
1256   * second, leading to >100% utilisation.  To deal with that, we call this
1257   * function to do a round-off before returning the results when reading
1258   * /proc/diskstats.  This accounts immediately for all queue usage up to
1259   * the current jiffies and restarts the counters again.
1260   */
1261  void part_round_stats(int cpu, struct hd_struct *part)
1262  {
1263  	unsigned long now = jiffies;
1264  
1265  	if (part->partno)
1266  		part_round_stats_single(cpu, &part_to_disk(part)->part0, now);
1267  	part_round_stats_single(cpu, part, now);
1268  }
1269  EXPORT_SYMBOL_GPL(part_round_stats);
1270  
1271  #ifdef CONFIG_PM_RUNTIME
1272  static void blk_pm_put_request(struct request *rq)
1273  {
1274  	if (rq->q->dev && !(rq->cmd_flags & REQ_PM) && !--rq->q->nr_pending)
1275  		pm_runtime_mark_last_busy(rq->q->dev);
1276  }
1277  #else
1278  static inline void blk_pm_put_request(struct request *rq) {}
1279  #endif
1280  
1281  /*
1282   * queue lock must be held
1283   */
1284  void __blk_put_request(struct request_queue *q, struct request *req)
1285  {
1286  	if (unlikely(!q))
1287  		return;
1288  
1289  	if (q->mq_ops) {
1290  		blk_mq_free_request(req);
1291  		return;
1292  	}
1293  
1294  	blk_pm_put_request(req);
1295  
1296  	elv_completed_request(q, req);
1297  
1298  	/* this is a bio leak */
1299  	WARN_ON(req->bio != NULL);
1300  
1301  	/*
1302  	 * Request may not have originated from ll_rw_blk. if not,
1303  	 * it didn't come out of our reserved rq pools
1304  	 */
1305  	if (req->cmd_flags & REQ_ALLOCED) {
1306  		unsigned int flags = req->cmd_flags;
1307  		struct request_list *rl = blk_rq_rl(req);
1308  
1309  		BUG_ON(!list_empty(&req->queuelist));
1310  		BUG_ON(!hlist_unhashed(&req->hash));
1311  
1312  		blk_free_request(rl, req);
1313  		freed_request(rl, flags);
1314  		blk_put_rl(rl);
1315  	}
1316  }
1317  EXPORT_SYMBOL_GPL(__blk_put_request);
1318  
1319  void blk_put_request(struct request *req)
1320  {
1321  	struct request_queue *q = req->q;
1322  
1323  	if (q->mq_ops)
1324  		blk_mq_free_request(req);
1325  	else {
1326  		unsigned long flags;
1327  
1328  		spin_lock_irqsave(q->queue_lock, flags);
1329  		__blk_put_request(q, req);
1330  		spin_unlock_irqrestore(q->queue_lock, flags);
1331  	}
1332  }
1333  EXPORT_SYMBOL(blk_put_request);
1334  
1335  /**
1336   * blk_add_request_payload - add a payload to a request
1337   * @rq: request to update
1338   * @page: page backing the payload
1339   * @len: length of the payload.
1340   *
1341   * This allows to later add a payload to an already submitted request by
1342   * a block driver.  The driver needs to take care of freeing the payload
1343   * itself.
1344   *
1345   * Note that this is a quite horrible hack and nothing but handling of
1346   * discard requests should ever use it.
1347   */
1348  void blk_add_request_payload(struct request *rq, struct page *page,
1349  		unsigned int len)
1350  {
1351  	struct bio *bio = rq->bio;
1352  
1353  	bio->bi_io_vec->bv_page = page;
1354  	bio->bi_io_vec->bv_offset = 0;
1355  	bio->bi_io_vec->bv_len = len;
1356  
1357  	bio->bi_iter.bi_size = len;
1358  	bio->bi_vcnt = 1;
1359  	bio->bi_phys_segments = 1;
1360  
1361  	rq->__data_len = rq->resid_len = len;
1362  	rq->nr_phys_segments = 1;
1363  	rq->buffer = bio_data(bio);
1364  }
1365  EXPORT_SYMBOL_GPL(blk_add_request_payload);
1366  
1367  bool bio_attempt_back_merge(struct request_queue *q, struct request *req,
1368  			    struct bio *bio)
1369  {
1370  	const int ff = bio->bi_rw & REQ_FAILFAST_MASK;
1371  
1372  	if (!ll_back_merge_fn(q, req, bio))
1373  		return false;
1374  
1375  	trace_block_bio_backmerge(q, req, bio);
1376  
1377  	if ((req->cmd_flags & REQ_FAILFAST_MASK) != ff)
1378  		blk_rq_set_mixed_merge(req);
1379  
1380  	req->biotail->bi_next = bio;
1381  	req->biotail = bio;
1382  	req->__data_len += bio->bi_iter.bi_size;
1383  	req->ioprio = ioprio_best(req->ioprio, bio_prio(bio));
1384  
1385  	blk_account_io_start(req, false);
1386  	return true;
1387  }
1388  
1389  bool bio_attempt_front_merge(struct request_queue *q, struct request *req,
1390  			     struct bio *bio)
1391  {
1392  	const int ff = bio->bi_rw & REQ_FAILFAST_MASK;
1393  
1394  	if (!ll_front_merge_fn(q, req, bio))
1395  		return false;
1396  
1397  	trace_block_bio_frontmerge(q, req, bio);
1398  
1399  	if ((req->cmd_flags & REQ_FAILFAST_MASK) != ff)
1400  		blk_rq_set_mixed_merge(req);
1401  
1402  	bio->bi_next = req->bio;
1403  	req->bio = bio;
1404  
1405  	/*
1406  	 * may not be valid. if the low level driver said
1407  	 * it didn't need a bounce buffer then it better
1408  	 * not touch req->buffer either...
1409  	 */
1410  	req->buffer = bio_data(bio);
1411  	req->__sector = bio->bi_iter.bi_sector;
1412  	req->__data_len += bio->bi_iter.bi_size;
1413  	req->ioprio = ioprio_best(req->ioprio, bio_prio(bio));
1414  
1415  	blk_account_io_start(req, false);
1416  	return true;
1417  }
1418  
1419  /**
1420   * blk_attempt_plug_merge - try to merge with %current's plugged list
1421   * @q: request_queue new bio is being queued at
1422   * @bio: new bio being queued
1423   * @request_count: out parameter for number of traversed plugged requests
1424   *
1425   * Determine whether @bio being queued on @q can be merged with a request
1426   * on %current's plugged list.  Returns %true if merge was successful,
1427   * otherwise %false.
1428   *
1429   * Plugging coalesces IOs from the same issuer for the same purpose without
1430   * going through @q->queue_lock.  As such it's more of an issuing mechanism
1431   * than scheduling, and the request, while may have elvpriv data, is not
1432   * added on the elevator at this point.  In addition, we don't have
1433   * reliable access to the elevator outside queue lock.  Only check basic
1434   * merging parameters without querying the elevator.
1435   */
1436  bool blk_attempt_plug_merge(struct request_queue *q, struct bio *bio,
1437  			    unsigned int *request_count)
1438  {
1439  	struct blk_plug *plug;
1440  	struct request *rq;
1441  	bool ret = false;
1442  	struct list_head *plug_list;
1443  
1444  	if (blk_queue_nomerges(q))
1445  		goto out;
1446  
1447  	plug = current->plug;
1448  	if (!plug)
1449  		goto out;
1450  	*request_count = 0;
1451  
1452  	if (q->mq_ops)
1453  		plug_list = &plug->mq_list;
1454  	else
1455  		plug_list = &plug->list;
1456  
1457  	list_for_each_entry_reverse(rq, plug_list, queuelist) {
1458  		int el_ret;
1459  
1460  		if (rq->q == q)
1461  			(*request_count)++;
1462  
1463  		if (rq->q != q || !blk_rq_merge_ok(rq, bio))
1464  			continue;
1465  
1466  		el_ret = blk_try_merge(rq, bio);
1467  		if (el_ret == ELEVATOR_BACK_MERGE) {
1468  			ret = bio_attempt_back_merge(q, rq, bio);
1469  			if (ret)
1470  				break;
1471  		} else if (el_ret == ELEVATOR_FRONT_MERGE) {
1472  			ret = bio_attempt_front_merge(q, rq, bio);
1473  			if (ret)
1474  				break;
1475  		}
1476  	}
1477  out:
1478  	return ret;
1479  }
1480  
1481  void init_request_from_bio(struct request *req, struct bio *bio)
1482  {
1483  	req->cmd_type = REQ_TYPE_FS;
1484  
1485  	req->cmd_flags |= bio->bi_rw & REQ_COMMON_MASK;
1486  	if (bio->bi_rw & REQ_RAHEAD)
1487  		req->cmd_flags |= REQ_FAILFAST_MASK;
1488  
1489  	req->errors = 0;
1490  	req->__sector = bio->bi_iter.bi_sector;
1491  	req->ioprio = bio_prio(bio);
1492  	blk_rq_bio_prep(req->q, req, bio);
1493  }
1494  
1495  void blk_queue_bio(struct request_queue *q, struct bio *bio)
1496  {
1497  	const bool sync = !!(bio->bi_rw & REQ_SYNC);
1498  	struct blk_plug *plug;
1499  	int el_ret, rw_flags, where = ELEVATOR_INSERT_SORT;
1500  	struct request *req;
1501  	unsigned int request_count = 0;
1502  
1503  	/*
1504  	 * low level driver can indicate that it wants pages above a
1505  	 * certain limit bounced to low memory (ie for highmem, or even
1506  	 * ISA dma in theory)
1507  	 */
1508  	blk_queue_bounce(q, &bio);
1509  
1510  	if (bio_integrity_enabled(bio) && bio_integrity_prep(bio)) {
1511  		bio_endio(bio, -EIO);
1512  		return;
1513  	}
1514  
1515  	if (bio->bi_rw & (REQ_FLUSH | REQ_FUA)) {
1516  		spin_lock_irq(q->queue_lock);
1517  		where = ELEVATOR_INSERT_FLUSH;
1518  		goto get_rq;
1519  	}
1520  
1521  	/*
1522  	 * Check if we can merge with the plugged list before grabbing
1523  	 * any locks.
1524  	 */
1525  	if (blk_attempt_plug_merge(q, bio, &request_count))
1526  		return;
1527  
1528  	spin_lock_irq(q->queue_lock);
1529  
1530  	el_ret = elv_merge(q, &req, bio);
1531  	if (el_ret == ELEVATOR_BACK_MERGE) {
1532  		if (bio_attempt_back_merge(q, req, bio)) {
1533  			elv_bio_merged(q, req, bio);
1534  			if (!attempt_back_merge(q, req))
1535  				elv_merged_request(q, req, el_ret);
1536  			goto out_unlock;
1537  		}
1538  	} else if (el_ret == ELEVATOR_FRONT_MERGE) {
1539  		if (bio_attempt_front_merge(q, req, bio)) {
1540  			elv_bio_merged(q, req, bio);
1541  			if (!attempt_front_merge(q, req))
1542  				elv_merged_request(q, req, el_ret);
1543  			goto out_unlock;
1544  		}
1545  	}
1546  
1547  get_rq:
1548  	/*
1549  	 * This sync check and mask will be re-done in init_request_from_bio(),
1550  	 * but we need to set it earlier to expose the sync flag to the
1551  	 * rq allocator and io schedulers.
1552  	 */
1553  	rw_flags = bio_data_dir(bio);
1554  	if (sync)
1555  		rw_flags |= REQ_SYNC;
1556  
1557  	/*
1558  	 * Grab a free request. This is might sleep but can not fail.
1559  	 * Returns with the queue unlocked.
1560  	 */
1561  	req = get_request(q, rw_flags, bio, GFP_NOIO);
1562  	if (unlikely(!req)) {
1563  		bio_endio(bio, -ENODEV);	/* @q is dead */
1564  		goto out_unlock;
1565  	}
1566  
1567  	/*
1568  	 * After dropping the lock and possibly sleeping here, our request
1569  	 * may now be mergeable after it had proven unmergeable (above).
1570  	 * We don't worry about that case for efficiency. It won't happen
1571  	 * often, and the elevators are able to handle it.
1572  	 */
1573  	init_request_from_bio(req, bio);
1574  
1575  	if (test_bit(QUEUE_FLAG_SAME_COMP, &q->queue_flags))
1576  		req->cpu = raw_smp_processor_id();
1577  
1578  	plug = current->plug;
1579  	if (plug) {
1580  		/*
1581  		 * If this is the first request added after a plug, fire
1582  		 * of a plug trace.
1583  		 */
1584  		if (!request_count)
1585  			trace_block_plug(q);
1586  		else {
1587  			if (request_count >= BLK_MAX_REQUEST_COUNT) {
1588  				blk_flush_plug_list(plug, false);
1589  				trace_block_plug(q);
1590  			}
1591  		}
1592  		list_add_tail(&req->queuelist, &plug->list);
1593  		blk_account_io_start(req, true);
1594  	} else {
1595  		spin_lock_irq(q->queue_lock);
1596  		add_acct_request(q, req, where);
1597  		__blk_run_queue(q);
1598  out_unlock:
1599  		spin_unlock_irq(q->queue_lock);
1600  	}
1601  }
1602  EXPORT_SYMBOL_GPL(blk_queue_bio);	/* for device mapper only */
1603  
1604  /*
1605   * If bio->bi_dev is a partition, remap the location
1606   */
1607  static inline void blk_partition_remap(struct bio *bio)
1608  {
1609  	struct block_device *bdev = bio->bi_bdev;
1610  
1611  	if (bio_sectors(bio) && bdev != bdev->bd_contains) {
1612  		struct hd_struct *p = bdev->bd_part;
1613  
1614  		bio->bi_iter.bi_sector += p->start_sect;
1615  		bio->bi_bdev = bdev->bd_contains;
1616  
1617  		trace_block_bio_remap(bdev_get_queue(bio->bi_bdev), bio,
1618  				      bdev->bd_dev,
1619  				      bio->bi_iter.bi_sector - p->start_sect);
1620  	}
1621  }
1622  
1623  static void handle_bad_sector(struct bio *bio)
1624  {
1625  	char b[BDEVNAME_SIZE];
1626  
1627  	printk(KERN_INFO "attempt to access beyond end of device\n");
1628  	printk(KERN_INFO "%s: rw=%ld, want=%Lu, limit=%Lu\n",
1629  			bdevname(bio->bi_bdev, b),
1630  			bio->bi_rw,
1631  			(unsigned long long)bio_end_sector(bio),
1632  			(long long)(i_size_read(bio->bi_bdev->bd_inode) >> 9));
1633  
1634  	set_bit(BIO_EOF, &bio->bi_flags);
1635  }
1636  
1637  #ifdef CONFIG_FAIL_MAKE_REQUEST
1638  
1639  static DECLARE_FAULT_ATTR(fail_make_request);
1640  
1641  static int __init setup_fail_make_request(char *str)
1642  {
1643  	return setup_fault_attr(&fail_make_request, str);
1644  }
1645  __setup("fail_make_request=", setup_fail_make_request);
1646  
1647  static bool should_fail_request(struct hd_struct *part, unsigned int bytes)
1648  {
1649  	return part->make_it_fail && should_fail(&fail_make_request, bytes);
1650  }
1651  
1652  static int __init fail_make_request_debugfs(void)
1653  {
1654  	struct dentry *dir = fault_create_debugfs_attr("fail_make_request",
1655  						NULL, &fail_make_request);
1656  
1657  	return IS_ERR(dir) ? PTR_ERR(dir) : 0;
1658  }
1659  
1660  late_initcall(fail_make_request_debugfs);
1661  
1662  #else /* CONFIG_FAIL_MAKE_REQUEST */
1663  
1664  static inline bool should_fail_request(struct hd_struct *part,
1665  					unsigned int bytes)
1666  {
1667  	return false;
1668  }
1669  
1670  #endif /* CONFIG_FAIL_MAKE_REQUEST */
1671  
1672  /*
1673   * Check whether this bio extends beyond the end of the device.
1674   */
1675  static inline int bio_check_eod(struct bio *bio, unsigned int nr_sectors)
1676  {
1677  	sector_t maxsector;
1678  
1679  	if (!nr_sectors)
1680  		return 0;
1681  
1682  	/* Test device or partition size, when known. */
1683  	maxsector = i_size_read(bio->bi_bdev->bd_inode) >> 9;
1684  	if (maxsector) {
1685  		sector_t sector = bio->bi_iter.bi_sector;
1686  
1687  		if (maxsector < nr_sectors || maxsector - nr_sectors < sector) {
1688  			/*
1689  			 * This may well happen - the kernel calls bread()
1690  			 * without checking the size of the device, e.g., when
1691  			 * mounting a device.
1692  			 */
1693  			handle_bad_sector(bio);
1694  			return 1;
1695  		}
1696  	}
1697  
1698  	return 0;
1699  }
1700  
1701  static noinline_for_stack bool
1702  generic_make_request_checks(struct bio *bio)
1703  {
1704  	struct request_queue *q;
1705  	int nr_sectors = bio_sectors(bio);
1706  	int err = -EIO;
1707  	char b[BDEVNAME_SIZE];
1708  	struct hd_struct *part;
1709  
1710  	might_sleep();
1711  
1712  	if (bio_check_eod(bio, nr_sectors))
1713  		goto end_io;
1714  
1715  	q = bdev_get_queue(bio->bi_bdev);
1716  	if (unlikely(!q)) {
1717  		printk(KERN_ERR
1718  		       "generic_make_request: Trying to access "
1719  			"nonexistent block-device %s (%Lu)\n",
1720  			bdevname(bio->bi_bdev, b),
1721  			(long long) bio->bi_iter.bi_sector);
1722  		goto end_io;
1723  	}
1724  
1725  	if (likely(bio_is_rw(bio) &&
1726  		   nr_sectors > queue_max_hw_sectors(q))) {
1727  		printk(KERN_ERR "bio too big device %s (%u > %u)\n",
1728  		       bdevname(bio->bi_bdev, b),
1729  		       bio_sectors(bio),
1730  		       queue_max_hw_sectors(q));
1731  		goto end_io;
1732  	}
1733  
1734  	part = bio->bi_bdev->bd_part;
1735  	if (should_fail_request(part, bio->bi_iter.bi_size) ||
1736  	    should_fail_request(&part_to_disk(part)->part0,
1737  				bio->bi_iter.bi_size))
1738  		goto end_io;
1739  
1740  	/*
1741  	 * If this device has partitions, remap block n
1742  	 * of partition p to block n+start(p) of the disk.
1743  	 */
1744  	blk_partition_remap(bio);
1745  
1746  	if (bio_check_eod(bio, nr_sectors))
1747  		goto end_io;
1748  
1749  	/*
1750  	 * Filter flush bio's early so that make_request based
1751  	 * drivers without flush support don't have to worry
1752  	 * about them.
1753  	 */
1754  	if ((bio->bi_rw & (REQ_FLUSH | REQ_FUA)) && !q->flush_flags) {
1755  		bio->bi_rw &= ~(REQ_FLUSH | REQ_FUA);
1756  		if (!nr_sectors) {
1757  			err = 0;
1758  			goto end_io;
1759  		}
1760  	}
1761  
1762  	if ((bio->bi_rw & REQ_DISCARD) &&
1763  	    (!blk_queue_discard(q) ||
1764  	     ((bio->bi_rw & REQ_SECURE) && !blk_queue_secdiscard(q)))) {
1765  		err = -EOPNOTSUPP;
1766  		goto end_io;
1767  	}
1768  
1769  	if (bio->bi_rw & REQ_WRITE_SAME && !bdev_write_same(bio->bi_bdev)) {
1770  		err = -EOPNOTSUPP;
1771  		goto end_io;
1772  	}
1773  
1774  	/*
1775  	 * Various block parts want %current->io_context and lazy ioc
1776  	 * allocation ends up trading a lot of pain for a small amount of
1777  	 * memory.  Just allocate it upfront.  This may fail and block
1778  	 * layer knows how to live with it.
1779  	 */
1780  	create_io_context(GFP_ATOMIC, q->node);
1781  
1782  	if (blk_throtl_bio(q, bio))
1783  		return false;	/* throttled, will be resubmitted later */
1784  
1785  	trace_block_bio_queue(q, bio);
1786  	return true;
1787  
1788  end_io:
1789  	bio_endio(bio, err);
1790  	return false;
1791  }
1792  
1793  /**
1794   * generic_make_request - hand a buffer to its device driver for I/O
1795   * @bio:  The bio describing the location in memory and on the device.
1796   *
1797   * generic_make_request() is used to make I/O requests of block
1798   * devices. It is passed a &struct bio, which describes the I/O that needs
1799   * to be done.
1800   *
1801   * generic_make_request() does not return any status.  The
1802   * success/failure status of the request, along with notification of
1803   * completion, is delivered asynchronously through the bio->bi_end_io
1804   * function described (one day) else where.
1805   *
1806   * The caller of generic_make_request must make sure that bi_io_vec
1807   * are set to describe the memory buffer, and that bi_dev and bi_sector are
1808   * set to describe the device address, and the
1809   * bi_end_io and optionally bi_private are set to describe how
1810   * completion notification should be signaled.
1811   *
1812   * generic_make_request and the drivers it calls may use bi_next if this
1813   * bio happens to be merged with someone else, and may resubmit the bio to
1814   * a lower device by calling into generic_make_request recursively, which
1815   * means the bio should NOT be touched after the call to ->make_request_fn.
1816   */
1817  void generic_make_request(struct bio *bio)
1818  {
1819  	struct bio_list bio_list_on_stack;
1820  
1821  	if (!generic_make_request_checks(bio))
1822  		return;
1823  
1824  	/*
1825  	 * We only want one ->make_request_fn to be active at a time, else
1826  	 * stack usage with stacked devices could be a problem.  So use
1827  	 * current->bio_list to keep a list of requests submited by a
1828  	 * make_request_fn function.  current->bio_list is also used as a
1829  	 * flag to say if generic_make_request is currently active in this
1830  	 * task or not.  If it is NULL, then no make_request is active.  If
1831  	 * it is non-NULL, then a make_request is active, and new requests
1832  	 * should be added at the tail
1833  	 */
1834  	if (current->bio_list) {
1835  		bio_list_add(current->bio_list, bio);
1836  		return;
1837  	}
1838  
1839  	/* following loop may be a bit non-obvious, and so deserves some
1840  	 * explanation.
1841  	 * Before entering the loop, bio->bi_next is NULL (as all callers
1842  	 * ensure that) so we have a list with a single bio.
1843  	 * We pretend that we have just taken it off a longer list, so
1844  	 * we assign bio_list to a pointer to the bio_list_on_stack,
1845  	 * thus initialising the bio_list of new bios to be
1846  	 * added.  ->make_request() may indeed add some more bios
1847  	 * through a recursive call to generic_make_request.  If it
1848  	 * did, we find a non-NULL value in bio_list and re-enter the loop
1849  	 * from the top.  In this case we really did just take the bio
1850  	 * of the top of the list (no pretending) and so remove it from
1851  	 * bio_list, and call into ->make_request() again.
1852  	 */
1853  	BUG_ON(bio->bi_next);
1854  	bio_list_init(&bio_list_on_stack);
1855  	current->bio_list = &bio_list_on_stack;
1856  	do {
1857  		struct request_queue *q = bdev_get_queue(bio->bi_bdev);
1858  
1859  		q->make_request_fn(q, bio);
1860  
1861  		bio = bio_list_pop(current->bio_list);
1862  	} while (bio);
1863  	current->bio_list = NULL; /* deactivate */
1864  }
1865  EXPORT_SYMBOL(generic_make_request);
1866  
1867  /**
1868   * submit_bio - submit a bio to the block device layer for I/O
1869   * @rw: whether to %READ or %WRITE, or maybe to %READA (read ahead)
1870   * @bio: The &struct bio which describes the I/O
1871   *
1872   * submit_bio() is very similar in purpose to generic_make_request(), and
1873   * uses that function to do most of the work. Both are fairly rough
1874   * interfaces; @bio must be presetup and ready for I/O.
1875   *
1876   */
1877  void submit_bio(int rw, struct bio *bio)
1878  {
1879  	bio->bi_rw |= rw;
1880  
1881  	/*
1882  	 * If it's a regular read/write or a barrier with data attached,
1883  	 * go through the normal accounting stuff before submission.
1884  	 */
1885  	if (bio_has_data(bio)) {
1886  		unsigned int count;
1887  
1888  		if (unlikely(rw & REQ_WRITE_SAME))
1889  			count = bdev_logical_block_size(bio->bi_bdev) >> 9;
1890  		else
1891  			count = bio_sectors(bio);
1892  
1893  		if (rw & WRITE) {
1894  			count_vm_events(PGPGOUT, count);
1895  		} else {
1896  			task_io_account_read(bio->bi_iter.bi_size);
1897  			count_vm_events(PGPGIN, count);
1898  		}
1899  
1900  		if (unlikely(block_dump)) {
1901  			char b[BDEVNAME_SIZE];
1902  			printk(KERN_DEBUG "%s(%d): %s block %Lu on %s (%u sectors)\n",
1903  			current->comm, task_pid_nr(current),
1904  				(rw & WRITE) ? "WRITE" : "READ",
1905  				(unsigned long long)bio->bi_iter.bi_sector,
1906  				bdevname(bio->bi_bdev, b),
1907  				count);
1908  		}
1909  	}
1910  
1911  	generic_make_request(bio);
1912  }
1913  EXPORT_SYMBOL(submit_bio);
1914  
1915  /**
1916   * blk_rq_check_limits - Helper function to check a request for the queue limit
1917   * @q:  the queue
1918   * @rq: the request being checked
1919   *
1920   * Description:
1921   *    @rq may have been made based on weaker limitations of upper-level queues
1922   *    in request stacking drivers, and it may violate the limitation of @q.
1923   *    Since the block layer and the underlying device driver trust @rq
1924   *    after it is inserted to @q, it should be checked against @q before
1925   *    the insertion using this generic function.
1926   *
1927   *    This function should also be useful for request stacking drivers
1928   *    in some cases below, so export this function.
1929   *    Request stacking drivers like request-based dm may change the queue
1930   *    limits while requests are in the queue (e.g. dm's table swapping).
1931   *    Such request stacking drivers should check those requests agaist
1932   *    the new queue limits again when they dispatch those requests,
1933   *    although such checkings are also done against the old queue limits
1934   *    when submitting requests.
1935   */
1936  int blk_rq_check_limits(struct request_queue *q, struct request *rq)
1937  {
1938  	if (!rq_mergeable(rq))
1939  		return 0;
1940  
1941  	if (blk_rq_sectors(rq) > blk_queue_get_max_sectors(q, rq->cmd_flags)) {
1942  		printk(KERN_ERR "%s: over max size limit.\n", __func__);
1943  		return -EIO;
1944  	}
1945  
1946  	/*
1947  	 * queue's settings related to segment counting like q->bounce_pfn
1948  	 * may differ from that of other stacking queues.
1949  	 * Recalculate it to check the request correctly on this queue's
1950  	 * limitation.
1951  	 */
1952  	blk_recalc_rq_segments(rq);
1953  	if (rq->nr_phys_segments > queue_max_segments(q)) {
1954  		printk(KERN_ERR "%s: over max segments limit.\n", __func__);
1955  		return -EIO;
1956  	}
1957  
1958  	return 0;
1959  }
1960  EXPORT_SYMBOL_GPL(blk_rq_check_limits);
1961  
1962  /**
1963   * blk_insert_cloned_request - Helper for stacking drivers to submit a request
1964   * @q:  the queue to submit the request
1965   * @rq: the request being queued
1966   */
1967  int blk_insert_cloned_request(struct request_queue *q, struct request *rq)
1968  {
1969  	unsigned long flags;
1970  	int where = ELEVATOR_INSERT_BACK;
1971  
1972  	if (blk_rq_check_limits(q, rq))
1973  		return -EIO;
1974  
1975  	if (rq->rq_disk &&
1976  	    should_fail_request(&rq->rq_disk->part0, blk_rq_bytes(rq)))
1977  		return -EIO;
1978  
1979  	spin_lock_irqsave(q->queue_lock, flags);
1980  	if (unlikely(blk_queue_dying(q))) {
1981  		spin_unlock_irqrestore(q->queue_lock, flags);
1982  		return -ENODEV;
1983  	}
1984  
1985  	/*
1986  	 * Submitting request must be dequeued before calling this function
1987  	 * because it will be linked to another request_queue
1988  	 */
1989  	BUG_ON(blk_queued_rq(rq));
1990  
1991  	if (rq->cmd_flags & (REQ_FLUSH|REQ_FUA))
1992  		where = ELEVATOR_INSERT_FLUSH;
1993  
1994  	add_acct_request(q, rq, where);
1995  	if (where == ELEVATOR_INSERT_FLUSH)
1996  		__blk_run_queue(q);
1997  	spin_unlock_irqrestore(q->queue_lock, flags);
1998  
1999  	return 0;
2000  }
2001  EXPORT_SYMBOL_GPL(blk_insert_cloned_request);
2002  
2003  /**
2004   * blk_rq_err_bytes - determine number of bytes till the next failure boundary
2005   * @rq: request to examine
2006   *
2007   * Description:
2008   *     A request could be merge of IOs which require different failure
2009   *     handling.  This function determines the number of bytes which
2010   *     can be failed from the beginning of the request without
2011   *     crossing into area which need to be retried further.
2012   *
2013   * Return:
2014   *     The number of bytes to fail.
2015   *
2016   * Context:
2017   *     queue_lock must be held.
2018   */
2019  unsigned int blk_rq_err_bytes(const struct request *rq)
2020  {
2021  	unsigned int ff = rq->cmd_flags & REQ_FAILFAST_MASK;
2022  	unsigned int bytes = 0;
2023  	struct bio *bio;
2024  
2025  	if (!(rq->cmd_flags & REQ_MIXED_MERGE))
2026  		return blk_rq_bytes(rq);
2027  
2028  	/*
2029  	 * Currently the only 'mixing' which can happen is between
2030  	 * different fastfail types.  We can safely fail portions
2031  	 * which have all the failfast bits that the first one has -
2032  	 * the ones which are at least as eager to fail as the first
2033  	 * one.
2034  	 */
2035  	for (bio = rq->bio; bio; bio = bio->bi_next) {
2036  		if ((bio->bi_rw & ff) != ff)
2037  			break;
2038  		bytes += bio->bi_iter.bi_size;
2039  	}
2040  
2041  	/* this could lead to infinite loop */
2042  	BUG_ON(blk_rq_bytes(rq) && !bytes);
2043  	return bytes;
2044  }
2045  EXPORT_SYMBOL_GPL(blk_rq_err_bytes);
2046  
2047  void blk_account_io_completion(struct request *req, unsigned int bytes)
2048  {
2049  	if (blk_do_io_stat(req)) {
2050  		const int rw = rq_data_dir(req);
2051  		struct hd_struct *part;
2052  		int cpu;
2053  
2054  		cpu = part_stat_lock();
2055  		part = req->part;
2056  		part_stat_add(cpu, part, sectors[rw], bytes >> 9);
2057  		part_stat_unlock();
2058  	}
2059  }
2060  
2061  void blk_account_io_done(struct request *req)
2062  {
2063  	/*
2064  	 * Account IO completion.  flush_rq isn't accounted as a
2065  	 * normal IO on queueing nor completion.  Accounting the
2066  	 * containing request is enough.
2067  	 */
2068  	if (blk_do_io_stat(req) && !(req->cmd_flags & REQ_FLUSH_SEQ)) {
2069  		unsigned long duration = jiffies - req->start_time;
2070  		const int rw = rq_data_dir(req);
2071  		struct hd_struct *part;
2072  		int cpu;
2073  
2074  		cpu = part_stat_lock();
2075  		part = req->part;
2076  
2077  		part_stat_inc(cpu, part, ios[rw]);
2078  		part_stat_add(cpu, part, ticks[rw], duration);
2079  		part_round_stats(cpu, part);
2080  		part_dec_in_flight(part, rw);
2081  
2082  		hd_struct_put(part);
2083  		part_stat_unlock();
2084  	}
2085  }
2086  
2087  #ifdef CONFIG_PM_RUNTIME
2088  /*
2089   * Don't process normal requests when queue is suspended
2090   * or in the process of suspending/resuming
2091   */
2092  static struct request *blk_pm_peek_request(struct request_queue *q,
2093  					   struct request *rq)
2094  {
2095  	if (q->dev && (q->rpm_status == RPM_SUSPENDED ||
2096  	    (q->rpm_status != RPM_ACTIVE && !(rq->cmd_flags & REQ_PM))))
2097  		return NULL;
2098  	else
2099  		return rq;
2100  }
2101  #else
2102  static inline struct request *blk_pm_peek_request(struct request_queue *q,
2103  						  struct request *rq)
2104  {
2105  	return rq;
2106  }
2107  #endif
2108  
2109  void blk_account_io_start(struct request *rq, bool new_io)
2110  {
2111  	struct hd_struct *part;
2112  	int rw = rq_data_dir(rq);
2113  	int cpu;
2114  
2115  	if (!blk_do_io_stat(rq))
2116  		return;
2117  
2118  	cpu = part_stat_lock();
2119  
2120  	if (!new_io) {
2121  		part = rq->part;
2122  		part_stat_inc(cpu, part, merges[rw]);
2123  	} else {
2124  		part = disk_map_sector_rcu(rq->rq_disk, blk_rq_pos(rq));
2125  		if (!hd_struct_try_get(part)) {
2126  			/*
2127  			 * The partition is already being removed,
2128  			 * the request will be accounted on the disk only
2129  			 *
2130  			 * We take a reference on disk->part0 although that
2131  			 * partition will never be deleted, so we can treat
2132  			 * it as any other partition.
2133  			 */
2134  			part = &rq->rq_disk->part0;
2135  			hd_struct_get(part);
2136  		}
2137  		part_round_stats(cpu, part);
2138  		part_inc_in_flight(part, rw);
2139  		rq->part = part;
2140  	}
2141  
2142  	part_stat_unlock();
2143  }
2144  
2145  /**
2146   * blk_peek_request - peek at the top of a request queue
2147   * @q: request queue to peek at
2148   *
2149   * Description:
2150   *     Return the request at the top of @q.  The returned request
2151   *     should be started using blk_start_request() before LLD starts
2152   *     processing it.
2153   *
2154   * Return:
2155   *     Pointer to the request at the top of @q if available.  Null
2156   *     otherwise.
2157   *
2158   * Context:
2159   *     queue_lock must be held.
2160   */
2161  struct request *blk_peek_request(struct request_queue *q)
2162  {
2163  	struct request *rq;
2164  	int ret;
2165  
2166  	while ((rq = __elv_next_request(q)) != NULL) {
2167  
2168  		rq = blk_pm_peek_request(q, rq);
2169  		if (!rq)
2170  			break;
2171  
2172  		if (!(rq->cmd_flags & REQ_STARTED)) {
2173  			/*
2174  			 * This is the first time the device driver
2175  			 * sees this request (possibly after
2176  			 * requeueing).  Notify IO scheduler.
2177  			 */
2178  			if (rq->cmd_flags & REQ_SORTED)
2179  				elv_activate_rq(q, rq);
2180  
2181  			/*
2182  			 * just mark as started even if we don't start
2183  			 * it, a request that has been delayed should
2184  			 * not be passed by new incoming requests
2185  			 */
2186  			rq->cmd_flags |= REQ_STARTED;
2187  			trace_block_rq_issue(q, rq);
2188  		}
2189  
2190  		if (!q->boundary_rq || q->boundary_rq == rq) {
2191  			q->end_sector = rq_end_sector(rq);
2192  			q->boundary_rq = NULL;
2193  		}
2194  
2195  		if (rq->cmd_flags & REQ_DONTPREP)
2196  			break;
2197  
2198  		if (q->dma_drain_size && blk_rq_bytes(rq)) {
2199  			/*
2200  			 * make sure space for the drain appears we
2201  			 * know we can do this because max_hw_segments
2202  			 * has been adjusted to be one fewer than the
2203  			 * device can handle
2204  			 */
2205  			rq->nr_phys_segments++;
2206  		}
2207  
2208  		if (!q->prep_rq_fn)
2209  			break;
2210  
2211  		ret = q->prep_rq_fn(q, rq);
2212  		if (ret == BLKPREP_OK) {
2213  			break;
2214  		} else if (ret == BLKPREP_DEFER) {
2215  			/*
2216  			 * the request may have been (partially) prepped.
2217  			 * we need to keep this request in the front to
2218  			 * avoid resource deadlock.  REQ_STARTED will
2219  			 * prevent other fs requests from passing this one.
2220  			 */
2221  			if (q->dma_drain_size && blk_rq_bytes(rq) &&
2222  			    !(rq->cmd_flags & REQ_DONTPREP)) {
2223  				/*
2224  				 * remove the space for the drain we added
2225  				 * so that we don't add it again
2226  				 */
2227  				--rq->nr_phys_segments;
2228  			}
2229  
2230  			rq = NULL;
2231  			break;
2232  		} else if (ret == BLKPREP_KILL) {
2233  			rq->cmd_flags |= REQ_QUIET;
2234  			/*
2235  			 * Mark this request as started so we don't trigger
2236  			 * any debug logic in the end I/O path.
2237  			 */
2238  			blk_start_request(rq);
2239  			__blk_end_request_all(rq, -EIO);
2240  		} else {
2241  			printk(KERN_ERR "%s: bad return=%d\n", __func__, ret);
2242  			break;
2243  		}
2244  	}
2245  
2246  	return rq;
2247  }
2248  EXPORT_SYMBOL(blk_peek_request);
2249  
2250  void blk_dequeue_request(struct request *rq)
2251  {
2252  	struct request_queue *q = rq->q;
2253  
2254  	BUG_ON(list_empty(&rq->queuelist));
2255  	BUG_ON(ELV_ON_HASH(rq));
2256  
2257  	list_del_init(&rq->queuelist);
2258  
2259  	/*
2260  	 * the time frame between a request being removed from the lists
2261  	 * and to it is freed is accounted as io that is in progress at
2262  	 * the driver side.
2263  	 */
2264  	if (blk_account_rq(rq)) {
2265  		q->in_flight[rq_is_sync(rq)]++;
2266  		set_io_start_time_ns(rq);
2267  	}
2268  }
2269  
2270  /**
2271   * blk_start_request - start request processing on the driver
2272   * @req: request to dequeue
2273   *
2274   * Description:
2275   *     Dequeue @req and start timeout timer on it.  This hands off the
2276   *     request to the driver.
2277   *
2278   *     Block internal functions which don't want to start timer should
2279   *     call blk_dequeue_request().
2280   *
2281   * Context:
2282   *     queue_lock must be held.
2283   */
2284  void blk_start_request(struct request *req)
2285  {
2286  	blk_dequeue_request(req);
2287  
2288  	/*
2289  	 * We are now handing the request to the hardware, initialize
2290  	 * resid_len to full count and add the timeout handler.
2291  	 */
2292  	req->resid_len = blk_rq_bytes(req);
2293  	if (unlikely(blk_bidi_rq(req)))
2294  		req->next_rq->resid_len = blk_rq_bytes(req->next_rq);
2295  
2296  	BUG_ON(test_bit(REQ_ATOM_COMPLETE, &req->atomic_flags));
2297  	blk_add_timer(req);
2298  }
2299  EXPORT_SYMBOL(blk_start_request);
2300  
2301  /**
2302   * blk_fetch_request - fetch a request from a request queue
2303   * @q: request queue to fetch a request from
2304   *
2305   * Description:
2306   *     Return the request at the top of @q.  The request is started on
2307   *     return and LLD can start processing it immediately.
2308   *
2309   * Return:
2310   *     Pointer to the request at the top of @q if available.  Null
2311   *     otherwise.
2312   *
2313   * Context:
2314   *     queue_lock must be held.
2315   */
2316  struct request *blk_fetch_request(struct request_queue *q)
2317  {
2318  	struct request *rq;
2319  
2320  	rq = blk_peek_request(q);
2321  	if (rq)
2322  		blk_start_request(rq);
2323  	return rq;
2324  }
2325  EXPORT_SYMBOL(blk_fetch_request);
2326  
2327  /**
2328   * blk_update_request - Special helper function for request stacking drivers
2329   * @req:      the request being processed
2330   * @error:    %0 for success, < %0 for error
2331   * @nr_bytes: number of bytes to complete @req
2332   *
2333   * Description:
2334   *     Ends I/O on a number of bytes attached to @req, but doesn't complete
2335   *     the request structure even if @req doesn't have leftover.
2336   *     If @req has leftover, sets it up for the next range of segments.
2337   *
2338   *     This special helper function is only for request stacking drivers
2339   *     (e.g. request-based dm) so that they can handle partial completion.
2340   *     Actual device drivers should use blk_end_request instead.
2341   *
2342   *     Passing the result of blk_rq_bytes() as @nr_bytes guarantees
2343   *     %false return from this function.
2344   *
2345   * Return:
2346   *     %false - this request doesn't have any more data
2347   *     %true  - this request has more data
2348   **/
2349  bool blk_update_request(struct request *req, int error, unsigned int nr_bytes)
2350  {
2351  	int total_bytes;
2352  
2353  	if (!req->bio)
2354  		return false;
2355  
2356  	trace_block_rq_complete(req->q, req);
2357  
2358  	/*
2359  	 * For fs requests, rq is just carrier of independent bio's
2360  	 * and each partial completion should be handled separately.
2361  	 * Reset per-request error on each partial completion.
2362  	 *
2363  	 * TODO: tj: This is too subtle.  It would be better to let
2364  	 * low level drivers do what they see fit.
2365  	 */
2366  	if (req->cmd_type == REQ_TYPE_FS)
2367  		req->errors = 0;
2368  
2369  	if (error && req->cmd_type == REQ_TYPE_FS &&
2370  	    !(req->cmd_flags & REQ_QUIET)) {
2371  		char *error_type;
2372  
2373  		switch (error) {
2374  		case -ENOLINK:
2375  			error_type = "recoverable transport";
2376  			break;
2377  		case -EREMOTEIO:
2378  			error_type = "critical target";
2379  			break;
2380  		case -EBADE:
2381  			error_type = "critical nexus";
2382  			break;
2383  		case -ETIMEDOUT:
2384  			error_type = "timeout";
2385  			break;
2386  		case -ENOSPC:
2387  			error_type = "critical space allocation";
2388  			break;
2389  		case -ENODATA:
2390  			error_type = "critical medium";
2391  			break;
2392  		case -EIO:
2393  		default:
2394  			error_type = "I/O";
2395  			break;
2396  		}
2397  		printk_ratelimited(KERN_ERR "end_request: %s error, dev %s, sector %llu\n",
2398  				   error_type, req->rq_disk ?
2399  				   req->rq_disk->disk_name : "?",
2400  				   (unsigned long long)blk_rq_pos(req));
2401  
2402  	}
2403  
2404  	blk_account_io_completion(req, nr_bytes);
2405  
2406  	total_bytes = 0;
2407  	while (req->bio) {
2408  		struct bio *bio = req->bio;
2409  		unsigned bio_bytes = min(bio->bi_iter.bi_size, nr_bytes);
2410  
2411  		if (bio_bytes == bio->bi_iter.bi_size)
2412  			req->bio = bio->bi_next;
2413  
2414  		req_bio_endio(req, bio, bio_bytes, error);
2415  
2416  		total_bytes += bio_bytes;
2417  		nr_bytes -= bio_bytes;
2418  
2419  		if (!nr_bytes)
2420  			break;
2421  	}
2422  
2423  	/*
2424  	 * completely done
2425  	 */
2426  	if (!req->bio) {
2427  		/*
2428  		 * Reset counters so that the request stacking driver
2429  		 * can find how many bytes remain in the request
2430  		 * later.
2431  		 */
2432  		req->__data_len = 0;
2433  		return false;
2434  	}
2435  
2436  	req->__data_len -= total_bytes;
2437  	req->buffer = bio_data(req->bio);
2438  
2439  	/* update sector only for requests with clear definition of sector */
2440  	if (req->cmd_type == REQ_TYPE_FS)
2441  		req->__sector += total_bytes >> 9;
2442  
2443  	/* mixed attributes always follow the first bio */
2444  	if (req->cmd_flags & REQ_MIXED_MERGE) {
2445  		req->cmd_flags &= ~REQ_FAILFAST_MASK;
2446  		req->cmd_flags |= req->bio->bi_rw & REQ_FAILFAST_MASK;
2447  	}
2448  
2449  	/*
2450  	 * If total number of sectors is less than the first segment
2451  	 * size, something has gone terribly wrong.
2452  	 */
2453  	if (blk_rq_bytes(req) < blk_rq_cur_bytes(req)) {
2454  		blk_dump_rq_flags(req, "request botched");
2455  		req->__data_len = blk_rq_cur_bytes(req);
2456  	}
2457  
2458  	/* recalculate the number of segments */
2459  	blk_recalc_rq_segments(req);
2460  
2461  	return true;
2462  }
2463  EXPORT_SYMBOL_GPL(blk_update_request);
2464  
2465  static bool blk_update_bidi_request(struct request *rq, int error,
2466  				    unsigned int nr_bytes,
2467  				    unsigned int bidi_bytes)
2468  {
2469  	if (blk_update_request(rq, error, nr_bytes))
2470  		return true;
2471  
2472  	/* Bidi request must be completed as a whole */
2473  	if (unlikely(blk_bidi_rq(rq)) &&
2474  	    blk_update_request(rq->next_rq, error, bidi_bytes))
2475  		return true;
2476  
2477  	if (blk_queue_add_random(rq->q))
2478  		add_disk_randomness(rq->rq_disk);
2479  
2480  	return false;
2481  }
2482  
2483  /**
2484   * blk_unprep_request - unprepare a request
2485   * @req:	the request
2486   *
2487   * This function makes a request ready for complete resubmission (or
2488   * completion).  It happens only after all error handling is complete,
2489   * so represents the appropriate moment to deallocate any resources
2490   * that were allocated to the request in the prep_rq_fn.  The queue
2491   * lock is held when calling this.
2492   */
2493  void blk_unprep_request(struct request *req)
2494  {
2495  	struct request_queue *q = req->q;
2496  
2497  	req->cmd_flags &= ~REQ_DONTPREP;
2498  	if (q->unprep_rq_fn)
2499  		q->unprep_rq_fn(q, req);
2500  }
2501  EXPORT_SYMBOL_GPL(blk_unprep_request);
2502  
2503  /*
2504   * queue lock must be held
2505   */
2506  static void blk_finish_request(struct request *req, int error)
2507  {
2508  	if (blk_rq_tagged(req))
2509  		blk_queue_end_tag(req->q, req);
2510  
2511  	BUG_ON(blk_queued_rq(req));
2512  
2513  	if (unlikely(laptop_mode) && req->cmd_type == REQ_TYPE_FS)
2514  		laptop_io_completion(&req->q->backing_dev_info);
2515  
2516  	blk_delete_timer(req);
2517  
2518  	if (req->cmd_flags & REQ_DONTPREP)
2519  		blk_unprep_request(req);
2520  
2521  	blk_account_io_done(req);
2522  
2523  	if (req->end_io)
2524  		req->end_io(req, error);
2525  	else {
2526  		if (blk_bidi_rq(req))
2527  			__blk_put_request(req->next_rq->q, req->next_rq);
2528  
2529  		__blk_put_request(req->q, req);
2530  	}
2531  }
2532  
2533  /**
2534   * blk_end_bidi_request - Complete a bidi request
2535   * @rq:         the request to complete
2536   * @error:      %0 for success, < %0 for error
2537   * @nr_bytes:   number of bytes to complete @rq
2538   * @bidi_bytes: number of bytes to complete @rq->next_rq
2539   *
2540   * Description:
2541   *     Ends I/O on a number of bytes attached to @rq and @rq->next_rq.
2542   *     Drivers that supports bidi can safely call this member for any
2543   *     type of request, bidi or uni.  In the later case @bidi_bytes is
2544   *     just ignored.
2545   *
2546   * Return:
2547   *     %false - we are done with this request
2548   *     %true  - still buffers pending for this request
2549   **/
2550  static bool blk_end_bidi_request(struct request *rq, int error,
2551  				 unsigned int nr_bytes, unsigned int bidi_bytes)
2552  {
2553  	struct request_queue *q = rq->q;
2554  	unsigned long flags;
2555  
2556  	if (blk_update_bidi_request(rq, error, nr_bytes, bidi_bytes))
2557  		return true;
2558  
2559  	spin_lock_irqsave(q->queue_lock, flags);
2560  	blk_finish_request(rq, error);
2561  	spin_unlock_irqrestore(q->queue_lock, flags);
2562  
2563  	return false;
2564  }
2565  
2566  /**
2567   * __blk_end_bidi_request - Complete a bidi request with queue lock held
2568   * @rq:         the request to complete
2569   * @error:      %0 for success, < %0 for error
2570   * @nr_bytes:   number of bytes to complete @rq
2571   * @bidi_bytes: number of bytes to complete @rq->next_rq
2572   *
2573   * Description:
2574   *     Identical to blk_end_bidi_request() except that queue lock is
2575   *     assumed to be locked on entry and remains so on return.
2576   *
2577   * Return:
2578   *     %false - we are done with this request
2579   *     %true  - still buffers pending for this request
2580   **/
2581  bool __blk_end_bidi_request(struct request *rq, int error,
2582  				   unsigned int nr_bytes, unsigned int bidi_bytes)
2583  {
2584  	if (blk_update_bidi_request(rq, error, nr_bytes, bidi_bytes))
2585  		return true;
2586  
2587  	blk_finish_request(rq, error);
2588  
2589  	return false;
2590  }
2591  
2592  /**
2593   * blk_end_request - Helper function for drivers to complete the request.
2594   * @rq:       the request being processed
2595   * @error:    %0 for success, < %0 for error
2596   * @nr_bytes: number of bytes to complete
2597   *
2598   * Description:
2599   *     Ends I/O on a number of bytes attached to @rq.
2600   *     If @rq has leftover, sets it up for the next range of segments.
2601   *
2602   * Return:
2603   *     %false - we are done with this request
2604   *     %true  - still buffers pending for this request
2605   **/
2606  bool blk_end_request(struct request *rq, int error, unsigned int nr_bytes)
2607  {
2608  	return blk_end_bidi_request(rq, error, nr_bytes, 0);
2609  }
2610  EXPORT_SYMBOL(blk_end_request);
2611  
2612  /**
2613   * blk_end_request_all - Helper function for drives to finish the request.
2614   * @rq: the request to finish
2615   * @error: %0 for success, < %0 for error
2616   *
2617   * Description:
2618   *     Completely finish @rq.
2619   */
2620  void blk_end_request_all(struct request *rq, int error)
2621  {
2622  	bool pending;
2623  	unsigned int bidi_bytes = 0;
2624  
2625  	if (unlikely(blk_bidi_rq(rq)))
2626  		bidi_bytes = blk_rq_bytes(rq->next_rq);
2627  
2628  	pending = blk_end_bidi_request(rq, error, blk_rq_bytes(rq), bidi_bytes);
2629  	BUG_ON(pending);
2630  }
2631  EXPORT_SYMBOL(blk_end_request_all);
2632  
2633  /**
2634   * blk_end_request_cur - Helper function to finish the current request chunk.
2635   * @rq: the request to finish the current chunk for
2636   * @error: %0 for success, < %0 for error
2637   *
2638   * Description:
2639   *     Complete the current consecutively mapped chunk from @rq.
2640   *
2641   * Return:
2642   *     %false - we are done with this request
2643   *     %true  - still buffers pending for this request
2644   */
2645  bool blk_end_request_cur(struct request *rq, int error)
2646  {
2647  	return blk_end_request(rq, error, blk_rq_cur_bytes(rq));
2648  }
2649  EXPORT_SYMBOL(blk_end_request_cur);
2650  
2651  /**
2652   * blk_end_request_err - Finish a request till the next failure boundary.
2653   * @rq: the request to finish till the next failure boundary for
2654   * @error: must be negative errno
2655   *
2656   * Description:
2657   *     Complete @rq till the next failure boundary.
2658   *
2659   * Return:
2660   *     %false - we are done with this request
2661   *     %true  - still buffers pending for this request
2662   */
2663  bool blk_end_request_err(struct request *rq, int error)
2664  {
2665  	WARN_ON(error >= 0);
2666  	return blk_end_request(rq, error, blk_rq_err_bytes(rq));
2667  }
2668  EXPORT_SYMBOL_GPL(blk_end_request_err);
2669  
2670  /**
2671   * __blk_end_request - Helper function for drivers to complete the request.
2672   * @rq:       the request being processed
2673   * @error:    %0 for success, < %0 for error
2674   * @nr_bytes: number of bytes to complete
2675   *
2676   * Description:
2677   *     Must be called with queue lock held unlike blk_end_request().
2678   *
2679   * Return:
2680   *     %false - we are done with this request
2681   *     %true  - still buffers pending for this request
2682   **/
2683  bool __blk_end_request(struct request *rq, int error, unsigned int nr_bytes)
2684  {
2685  	return __blk_end_bidi_request(rq, error, nr_bytes, 0);
2686  }
2687  EXPORT_SYMBOL(__blk_end_request);
2688  
2689  /**
2690   * __blk_end_request_all - Helper function for drives to finish the request.
2691   * @rq: the request to finish
2692   * @error: %0 for success, < %0 for error
2693   *
2694   * Description:
2695   *     Completely finish @rq.  Must be called with queue lock held.
2696   */
2697  void __blk_end_request_all(struct request *rq, int error)
2698  {
2699  	bool pending;
2700  	unsigned int bidi_bytes = 0;
2701  
2702  	if (unlikely(blk_bidi_rq(rq)))
2703  		bidi_bytes = blk_rq_bytes(rq->next_rq);
2704  
2705  	pending = __blk_end_bidi_request(rq, error, blk_rq_bytes(rq), bidi_bytes);
2706  	BUG_ON(pending);
2707  }
2708  EXPORT_SYMBOL(__blk_end_request_all);
2709  
2710  /**
2711   * __blk_end_request_cur - Helper function to finish the current request chunk.
2712   * @rq: the request to finish the current chunk for
2713   * @error: %0 for success, < %0 for error
2714   *
2715   * Description:
2716   *     Complete the current consecutively mapped chunk from @rq.  Must
2717   *     be called with queue lock held.
2718   *
2719   * Return:
2720   *     %false - we are done with this request
2721   *     %true  - still buffers pending for this request
2722   */
2723  bool __blk_end_request_cur(struct request *rq, int error)
2724  {
2725  	return __blk_end_request(rq, error, blk_rq_cur_bytes(rq));
2726  }
2727  EXPORT_SYMBOL(__blk_end_request_cur);
2728  
2729  /**
2730   * __blk_end_request_err - Finish a request till the next failure boundary.
2731   * @rq: the request to finish till the next failure boundary for
2732   * @error: must be negative errno
2733   *
2734   * Description:
2735   *     Complete @rq till the next failure boundary.  Must be called
2736   *     with queue lock held.
2737   *
2738   * Return:
2739   *     %false - we are done with this request
2740   *     %true  - still buffers pending for this request
2741   */
2742  bool __blk_end_request_err(struct request *rq, int error)
2743  {
2744  	WARN_ON(error >= 0);
2745  	return __blk_end_request(rq, error, blk_rq_err_bytes(rq));
2746  }
2747  EXPORT_SYMBOL_GPL(__blk_end_request_err);
2748  
2749  void blk_rq_bio_prep(struct request_queue *q, struct request *rq,
2750  		     struct bio *bio)
2751  {
2752  	/* Bit 0 (R/W) is identical in rq->cmd_flags and bio->bi_rw */
2753  	rq->cmd_flags |= bio->bi_rw & REQ_WRITE;
2754  
2755  	if (bio_has_data(bio)) {
2756  		rq->nr_phys_segments = bio_phys_segments(q, bio);
2757  		rq->buffer = bio_data(bio);
2758  	}
2759  	rq->__data_len = bio->bi_iter.bi_size;
2760  	rq->bio = rq->biotail = bio;
2761  
2762  	if (bio->bi_bdev)
2763  		rq->rq_disk = bio->bi_bdev->bd_disk;
2764  }
2765  
2766  #if ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE
2767  /**
2768   * rq_flush_dcache_pages - Helper function to flush all pages in a request
2769   * @rq: the request to be flushed
2770   *
2771   * Description:
2772   *     Flush all pages in @rq.
2773   */
2774  void rq_flush_dcache_pages(struct request *rq)
2775  {
2776  	struct req_iterator iter;
2777  	struct bio_vec bvec;
2778  
2779  	rq_for_each_segment(bvec, rq, iter)
2780  		flush_dcache_page(bvec.bv_page);
2781  }
2782  EXPORT_SYMBOL_GPL(rq_flush_dcache_pages);
2783  #endif
2784  
2785  /**
2786   * blk_lld_busy - Check if underlying low-level drivers of a device are busy
2787   * @q : the queue of the device being checked
2788   *
2789   * Description:
2790   *    Check if underlying low-level drivers of a device are busy.
2791   *    If the drivers want to export their busy state, they must set own
2792   *    exporting function using blk_queue_lld_busy() first.
2793   *
2794   *    Basically, this function is used only by request stacking drivers
2795   *    to stop dispatching requests to underlying devices when underlying
2796   *    devices are busy.  This behavior helps more I/O merging on the queue
2797   *    of the request stacking driver and prevents I/O throughput regression
2798   *    on burst I/O load.
2799   *
2800   * Return:
2801   *    0 - Not busy (The request stacking driver should dispatch request)
2802   *    1 - Busy (The request stacking driver should stop dispatching request)
2803   */
2804  int blk_lld_busy(struct request_queue *q)
2805  {
2806  	if (q->lld_busy_fn)
2807  		return q->lld_busy_fn(q);
2808  
2809  	return 0;
2810  }
2811  EXPORT_SYMBOL_GPL(blk_lld_busy);
2812  
2813  /**
2814   * blk_rq_unprep_clone - Helper function to free all bios in a cloned request
2815   * @rq: the clone request to be cleaned up
2816   *
2817   * Description:
2818   *     Free all bios in @rq for a cloned request.
2819   */
2820  void blk_rq_unprep_clone(struct request *rq)
2821  {
2822  	struct bio *bio;
2823  
2824  	while ((bio = rq->bio) != NULL) {
2825  		rq->bio = bio->bi_next;
2826  
2827  		bio_put(bio);
2828  	}
2829  }
2830  EXPORT_SYMBOL_GPL(blk_rq_unprep_clone);
2831  
2832  /*
2833   * Copy attributes of the original request to the clone request.
2834   * The actual data parts (e.g. ->cmd, ->buffer, ->sense) are not copied.
2835   */
2836  static void __blk_rq_prep_clone(struct request *dst, struct request *src)
2837  {
2838  	dst->cpu = src->cpu;
2839  	dst->cmd_flags = (src->cmd_flags & REQ_CLONE_MASK) | REQ_NOMERGE;
2840  	dst->cmd_type = src->cmd_type;
2841  	dst->__sector = blk_rq_pos(src);
2842  	dst->__data_len = blk_rq_bytes(src);
2843  	dst->nr_phys_segments = src->nr_phys_segments;
2844  	dst->ioprio = src->ioprio;
2845  	dst->extra_len = src->extra_len;
2846  }
2847  
2848  /**
2849   * blk_rq_prep_clone - Helper function to setup clone request
2850   * @rq: the request to be setup
2851   * @rq_src: original request to be cloned
2852   * @bs: bio_set that bios for clone are allocated from
2853   * @gfp_mask: memory allocation mask for bio
2854   * @bio_ctr: setup function to be called for each clone bio.
2855   *           Returns %0 for success, non %0 for failure.
2856   * @data: private data to be passed to @bio_ctr
2857   *
2858   * Description:
2859   *     Clones bios in @rq_src to @rq, and copies attributes of @rq_src to @rq.
2860   *     The actual data parts of @rq_src (e.g. ->cmd, ->buffer, ->sense)
2861   *     are not copied, and copying such parts is the caller's responsibility.
2862   *     Also, pages which the original bios are pointing to are not copied
2863   *     and the cloned bios just point same pages.
2864   *     So cloned bios must be completed before original bios, which means
2865   *     the caller must complete @rq before @rq_src.
2866   */
2867  int blk_rq_prep_clone(struct request *rq, struct request *rq_src,
2868  		      struct bio_set *bs, gfp_t gfp_mask,
2869  		      int (*bio_ctr)(struct bio *, struct bio *, void *),
2870  		      void *data)
2871  {
2872  	struct bio *bio, *bio_src;
2873  
2874  	if (!bs)
2875  		bs = fs_bio_set;
2876  
2877  	blk_rq_init(NULL, rq);
2878  
2879  	__rq_for_each_bio(bio_src, rq_src) {
2880  		bio = bio_clone_bioset(bio_src, gfp_mask, bs);
2881  		if (!bio)
2882  			goto free_and_out;
2883  
2884  		if (bio_ctr && bio_ctr(bio, bio_src, data))
2885  			goto free_and_out;
2886  
2887  		if (rq->bio) {
2888  			rq->biotail->bi_next = bio;
2889  			rq->biotail = bio;
2890  		} else
2891  			rq->bio = rq->biotail = bio;
2892  	}
2893  
2894  	__blk_rq_prep_clone(rq, rq_src);
2895  
2896  	return 0;
2897  
2898  free_and_out:
2899  	if (bio)
2900  		bio_put(bio);
2901  	blk_rq_unprep_clone(rq);
2902  
2903  	return -ENOMEM;
2904  }
2905  EXPORT_SYMBOL_GPL(blk_rq_prep_clone);
2906  
2907  int kblockd_schedule_work(struct request_queue *q, struct work_struct *work)
2908  {
2909  	return queue_work(kblockd_workqueue, work);
2910  }
2911  EXPORT_SYMBOL(kblockd_schedule_work);
2912  
2913  int kblockd_schedule_delayed_work(struct request_queue *q,
2914  			struct delayed_work *dwork, unsigned long delay)
2915  {
2916  	return queue_delayed_work(kblockd_workqueue, dwork, delay);
2917  }
2918  EXPORT_SYMBOL(kblockd_schedule_delayed_work);
2919  
2920  #define PLUG_MAGIC	0x91827364
2921  
2922  /**
2923   * blk_start_plug - initialize blk_plug and track it inside the task_struct
2924   * @plug:	The &struct blk_plug that needs to be initialized
2925   *
2926   * Description:
2927   *   Tracking blk_plug inside the task_struct will help with auto-flushing the
2928   *   pending I/O should the task end up blocking between blk_start_plug() and
2929   *   blk_finish_plug(). This is important from a performance perspective, but
2930   *   also ensures that we don't deadlock. For instance, if the task is blocking
2931   *   for a memory allocation, memory reclaim could end up wanting to free a
2932   *   page belonging to that request that is currently residing in our private
2933   *   plug. By flushing the pending I/O when the process goes to sleep, we avoid
2934   *   this kind of deadlock.
2935   */
2936  void blk_start_plug(struct blk_plug *plug)
2937  {
2938  	struct task_struct *tsk = current;
2939  
2940  	plug->magic = PLUG_MAGIC;
2941  	INIT_LIST_HEAD(&plug->list);
2942  	INIT_LIST_HEAD(&plug->mq_list);
2943  	INIT_LIST_HEAD(&plug->cb_list);
2944  
2945  	/*
2946  	 * If this is a nested plug, don't actually assign it. It will be
2947  	 * flushed on its own.
2948  	 */
2949  	if (!tsk->plug) {
2950  		/*
2951  		 * Store ordering should not be needed here, since a potential
2952  		 * preempt will imply a full memory barrier
2953  		 */
2954  		tsk->plug = plug;
2955  	}
2956  }
2957  EXPORT_SYMBOL(blk_start_plug);
2958  
2959  static int plug_rq_cmp(void *priv, struct list_head *a, struct list_head *b)
2960  {
2961  	struct request *rqa = container_of(a, struct request, queuelist);
2962  	struct request *rqb = container_of(b, struct request, queuelist);
2963  
2964  	return !(rqa->q < rqb->q ||
2965  		(rqa->q == rqb->q && blk_rq_pos(rqa) < blk_rq_pos(rqb)));
2966  }
2967  
2968  /*
2969   * If 'from_schedule' is true, then postpone the dispatch of requests
2970   * until a safe kblockd context. We due this to avoid accidental big
2971   * additional stack usage in driver dispatch, in places where the originally
2972   * plugger did not intend it.
2973   */
2974  static void queue_unplugged(struct request_queue *q, unsigned int depth,
2975  			    bool from_schedule)
2976  	__releases(q->queue_lock)
2977  {
2978  	trace_block_unplug(q, depth, !from_schedule);
2979  
2980  	if (from_schedule)
2981  		blk_run_queue_async(q);
2982  	else
2983  		__blk_run_queue(q);
2984  	spin_unlock(q->queue_lock);
2985  }
2986  
2987  static void flush_plug_callbacks(struct blk_plug *plug, bool from_schedule)
2988  {
2989  	LIST_HEAD(callbacks);
2990  
2991  	while (!list_empty(&plug->cb_list)) {
2992  		list_splice_init(&plug->cb_list, &callbacks);
2993  
2994  		while (!list_empty(&callbacks)) {
2995  			struct blk_plug_cb *cb = list_first_entry(&callbacks,
2996  							  struct blk_plug_cb,
2997  							  list);
2998  			list_del(&cb->list);
2999  			cb->callback(cb, from_schedule);
3000  		}
3001  	}
3002  }
3003  
3004  struct blk_plug_cb *blk_check_plugged(blk_plug_cb_fn unplug, void *data,
3005  				      int size)
3006  {
3007  	struct blk_plug *plug = current->plug;
3008  	struct blk_plug_cb *cb;
3009  
3010  	if (!plug)
3011  		return NULL;
3012  
3013  	list_for_each_entry(cb, &plug->cb_list, list)
3014  		if (cb->callback == unplug && cb->data == data)
3015  			return cb;
3016  
3017  	/* Not currently on the callback list */
3018  	BUG_ON(size < sizeof(*cb));
3019  	cb = kzalloc(size, GFP_ATOMIC);
3020  	if (cb) {
3021  		cb->data = data;
3022  		cb->callback = unplug;
3023  		list_add(&cb->list, &plug->cb_list);
3024  	}
3025  	return cb;
3026  }
3027  EXPORT_SYMBOL(blk_check_plugged);
3028  
3029  void blk_flush_plug_list(struct blk_plug *plug, bool from_schedule)
3030  {
3031  	struct request_queue *q;
3032  	unsigned long flags;
3033  	struct request *rq;
3034  	LIST_HEAD(list);
3035  	unsigned int depth;
3036  
3037  	BUG_ON(plug->magic != PLUG_MAGIC);
3038  
3039  	flush_plug_callbacks(plug, from_schedule);
3040  
3041  	if (!list_empty(&plug->mq_list))
3042  		blk_mq_flush_plug_list(plug, from_schedule);
3043  
3044  	if (list_empty(&plug->list))
3045  		return;
3046  
3047  	list_splice_init(&plug->list, &list);
3048  
3049  	list_sort(NULL, &list, plug_rq_cmp);
3050  
3051  	q = NULL;
3052  	depth = 0;
3053  
3054  	/*
3055  	 * Save and disable interrupts here, to avoid doing it for every
3056  	 * queue lock we have to take.
3057  	 */
3058  	local_irq_save(flags);
3059  	while (!list_empty(&list)) {
3060  		rq = list_entry_rq(list.next);
3061  		list_del_init(&rq->queuelist);
3062  		BUG_ON(!rq->q);
3063  		if (rq->q != q) {
3064  			/*
3065  			 * This drops the queue lock
3066  			 */
3067  			if (q)
3068  				queue_unplugged(q, depth, from_schedule);
3069  			q = rq->q;
3070  			depth = 0;
3071  			spin_lock(q->queue_lock);
3072  		}
3073  
3074  		/*
3075  		 * Short-circuit if @q is dead
3076  		 */
3077  		if (unlikely(blk_queue_dying(q))) {
3078  			__blk_end_request_all(rq, -ENODEV);
3079  			continue;
3080  		}
3081  
3082  		/*
3083  		 * rq is already accounted, so use raw insert
3084  		 */
3085  		if (rq->cmd_flags & (REQ_FLUSH | REQ_FUA))
3086  			__elv_add_request(q, rq, ELEVATOR_INSERT_FLUSH);
3087  		else
3088  			__elv_add_request(q, rq, ELEVATOR_INSERT_SORT_MERGE);
3089  
3090  		depth++;
3091  	}
3092  
3093  	/*
3094  	 * This drops the queue lock
3095  	 */
3096  	if (q)
3097  		queue_unplugged(q, depth, from_schedule);
3098  
3099  	local_irq_restore(flags);
3100  }
3101  
3102  void blk_finish_plug(struct blk_plug *plug)
3103  {
3104  	blk_flush_plug_list(plug, false);
3105  
3106  	if (plug == current->plug)
3107  		current->plug = NULL;
3108  }
3109  EXPORT_SYMBOL(blk_finish_plug);
3110  
3111  #ifdef CONFIG_PM_RUNTIME
3112  /**
3113   * blk_pm_runtime_init - Block layer runtime PM initialization routine
3114   * @q: the queue of the device
3115   * @dev: the device the queue belongs to
3116   *
3117   * Description:
3118   *    Initialize runtime-PM-related fields for @q and start auto suspend for
3119   *    @dev. Drivers that want to take advantage of request-based runtime PM
3120   *    should call this function after @dev has been initialized, and its
3121   *    request queue @q has been allocated, and runtime PM for it can not happen
3122   *    yet(either due to disabled/forbidden or its usage_count > 0). In most
3123   *    cases, driver should call this function before any I/O has taken place.
3124   *
3125   *    This function takes care of setting up using auto suspend for the device,
3126   *    the autosuspend delay is set to -1 to make runtime suspend impossible
3127   *    until an updated value is either set by user or by driver. Drivers do
3128   *    not need to touch other autosuspend settings.
3129   *
3130   *    The block layer runtime PM is request based, so only works for drivers
3131   *    that use request as their IO unit instead of those directly use bio's.
3132   */
3133  void blk_pm_runtime_init(struct request_queue *q, struct device *dev)
3134  {
3135  	q->dev = dev;
3136  	q->rpm_status = RPM_ACTIVE;
3137  	pm_runtime_set_autosuspend_delay(q->dev, -1);
3138  	pm_runtime_use_autosuspend(q->dev);
3139  }
3140  EXPORT_SYMBOL(blk_pm_runtime_init);
3141  
3142  /**
3143   * blk_pre_runtime_suspend - Pre runtime suspend check
3144   * @q: the queue of the device
3145   *
3146   * Description:
3147   *    This function will check if runtime suspend is allowed for the device
3148   *    by examining if there are any requests pending in the queue. If there
3149   *    are requests pending, the device can not be runtime suspended; otherwise,
3150   *    the queue's status will be updated to SUSPENDING and the driver can
3151   *    proceed to suspend the device.
3152   *
3153   *    For the not allowed case, we mark last busy for the device so that
3154   *    runtime PM core will try to autosuspend it some time later.
3155   *
3156   *    This function should be called near the start of the device's
3157   *    runtime_suspend callback.
3158   *
3159   * Return:
3160   *    0		- OK to runtime suspend the device
3161   *    -EBUSY	- Device should not be runtime suspended
3162   */
3163  int blk_pre_runtime_suspend(struct request_queue *q)
3164  {
3165  	int ret = 0;
3166  
3167  	spin_lock_irq(q->queue_lock);
3168  	if (q->nr_pending) {
3169  		ret = -EBUSY;
3170  		pm_runtime_mark_last_busy(q->dev);
3171  	} else {
3172  		q->rpm_status = RPM_SUSPENDING;
3173  	}
3174  	spin_unlock_irq(q->queue_lock);
3175  	return ret;
3176  }
3177  EXPORT_SYMBOL(blk_pre_runtime_suspend);
3178  
3179  /**
3180   * blk_post_runtime_suspend - Post runtime suspend processing
3181   * @q: the queue of the device
3182   * @err: return value of the device's runtime_suspend function
3183   *
3184   * Description:
3185   *    Update the queue's runtime status according to the return value of the
3186   *    device's runtime suspend function and mark last busy for the device so
3187   *    that PM core will try to auto suspend the device at a later time.
3188   *
3189   *    This function should be called near the end of the device's
3190   *    runtime_suspend callback.
3191   */
3192  void blk_post_runtime_suspend(struct request_queue *q, int err)
3193  {
3194  	spin_lock_irq(q->queue_lock);
3195  	if (!err) {
3196  		q->rpm_status = RPM_SUSPENDED;
3197  	} else {
3198  		q->rpm_status = RPM_ACTIVE;
3199  		pm_runtime_mark_last_busy(q->dev);
3200  	}
3201  	spin_unlock_irq(q->queue_lock);
3202  }
3203  EXPORT_SYMBOL(blk_post_runtime_suspend);
3204  
3205  /**
3206   * blk_pre_runtime_resume - Pre runtime resume processing
3207   * @q: the queue of the device
3208   *
3209   * Description:
3210   *    Update the queue's runtime status to RESUMING in preparation for the
3211   *    runtime resume of the device.
3212   *
3213   *    This function should be called near the start of the device's
3214   *    runtime_resume callback.
3215   */
3216  void blk_pre_runtime_resume(struct request_queue *q)
3217  {
3218  	spin_lock_irq(q->queue_lock);
3219  	q->rpm_status = RPM_RESUMING;
3220  	spin_unlock_irq(q->queue_lock);
3221  }
3222  EXPORT_SYMBOL(blk_pre_runtime_resume);
3223  
3224  /**
3225   * blk_post_runtime_resume - Post runtime resume processing
3226   * @q: the queue of the device
3227   * @err: return value of the device's runtime_resume function
3228   *
3229   * Description:
3230   *    Update the queue's runtime status according to the return value of the
3231   *    device's runtime_resume function. If it is successfully resumed, process
3232   *    the requests that are queued into the device's queue when it is resuming
3233   *    and then mark last busy and initiate autosuspend for it.
3234   *
3235   *    This function should be called near the end of the device's
3236   *    runtime_resume callback.
3237   */
3238  void blk_post_runtime_resume(struct request_queue *q, int err)
3239  {
3240  	spin_lock_irq(q->queue_lock);
3241  	if (!err) {
3242  		q->rpm_status = RPM_ACTIVE;
3243  		__blk_run_queue(q);
3244  		pm_runtime_mark_last_busy(q->dev);
3245  		pm_request_autosuspend(q->dev);
3246  	} else {
3247  		q->rpm_status = RPM_SUSPENDED;
3248  	}
3249  	spin_unlock_irq(q->queue_lock);
3250  }
3251  EXPORT_SYMBOL(blk_post_runtime_resume);
3252  #endif
3253  
3254  int __init blk_dev_init(void)
3255  {
3256  	BUILD_BUG_ON(__REQ_NR_BITS > 8 *
3257  			sizeof(((struct request *)0)->cmd_flags));
3258  
3259  	/* used for unplugging and affects IO latency/throughput - HIGHPRI */
3260  	kblockd_workqueue = alloc_workqueue("kblockd",
3261  					    WQ_MEM_RECLAIM | WQ_HIGHPRI |
3262  					    WQ_POWER_EFFICIENT, 0);
3263  	if (!kblockd_workqueue)
3264  		panic("Failed to create kblockd\n");
3265  
3266  	request_cachep = kmem_cache_create("blkdev_requests",
3267  			sizeof(struct request), 0, SLAB_PANIC, NULL);
3268  
3269  	blk_requestq_cachep = kmem_cache_create("blkdev_queue",
3270  			sizeof(struct request_queue), 0, SLAB_PANIC, NULL);
3271  
3272  	return 0;
3273  }
3274