Root/block/blk-core.c

1/*
2 * Copyright (C) 1991, 1992 Linus Torvalds
3 * Copyright (C) 1994, Karl Keyte: Added support for disk statistics
4 * Elevator latency, (C) 2000 Andrea Arcangeli <andrea@suse.de> SuSE
5 * Queue request tables / lock, selectable elevator, Jens Axboe <axboe@suse.de>
6 * kernel-doc documentation started by NeilBrown <neilb@cse.unsw.edu.au>
7 * - July2000
8 * bio rewrite, highmem i/o, etc, Jens Axboe <axboe@suse.de> - may 2001
9 */
10
11/*
12 * This handles all read/write requests to block devices
13 */
14#include <linux/kernel.h>
15#include <linux/module.h>
16#include <linux/backing-dev.h>
17#include <linux/bio.h>
18#include <linux/blkdev.h>
19#include <linux/highmem.h>
20#include <linux/mm.h>
21#include <linux/kernel_stat.h>
22#include <linux/string.h>
23#include <linux/init.h>
24#include <linux/completion.h>
25#include <linux/slab.h>
26#include <linux/swap.h>
27#include <linux/writeback.h>
28#include <linux/task_io_accounting_ops.h>
29#include <linux/fault-inject.h>
30
31#define CREATE_TRACE_POINTS
32#include <trace/events/block.h>
33
34#include "blk.h"
35
36EXPORT_TRACEPOINT_SYMBOL_GPL(block_remap);
37EXPORT_TRACEPOINT_SYMBOL_GPL(block_rq_remap);
38EXPORT_TRACEPOINT_SYMBOL_GPL(block_bio_complete);
39
40static int __make_request(struct request_queue *q, struct bio *bio);
41
42/*
43 * For the allocated request tables
44 */
45static struct kmem_cache *request_cachep;
46
47/*
48 * For queue allocation
49 */
50struct kmem_cache *blk_requestq_cachep;
51
52/*
53 * Controlling structure to kblockd
54 */
55static struct workqueue_struct *kblockd_workqueue;
56
57static void drive_stat_acct(struct request *rq, int new_io)
58{
59    struct hd_struct *part;
60    int rw = rq_data_dir(rq);
61    int cpu;
62
63    if (!blk_do_io_stat(rq))
64        return;
65
66    cpu = part_stat_lock();
67    part = disk_map_sector_rcu(rq->rq_disk, blk_rq_pos(rq));
68
69    if (!new_io)
70        part_stat_inc(cpu, part, merges[rw]);
71    else {
72        part_round_stats(cpu, part);
73        part_inc_in_flight(part, rw);
74    }
75
76    part_stat_unlock();
77}
78
79void blk_queue_congestion_threshold(struct request_queue *q)
80{
81    int nr;
82
83    nr = q->nr_requests - (q->nr_requests / 8) + 1;
84    if (nr > q->nr_requests)
85        nr = q->nr_requests;
86    q->nr_congestion_on = nr;
87
88    nr = q->nr_requests - (q->nr_requests / 8) - (q->nr_requests / 16) - 1;
89    if (nr < 1)
90        nr = 1;
91    q->nr_congestion_off = nr;
92}
93
94/**
95 * blk_get_backing_dev_info - get the address of a queue's backing_dev_info
96 * @bdev: device
97 *
98 * Locates the passed device's request queue and returns the address of its
99 * backing_dev_info
100 *
101 * Will return NULL if the request queue cannot be located.
102 */
103struct backing_dev_info *blk_get_backing_dev_info(struct block_device *bdev)
104{
105    struct backing_dev_info *ret = NULL;
106    struct request_queue *q = bdev_get_queue(bdev);
107
108    if (q)
109        ret = &q->backing_dev_info;
110    return ret;
111}
112EXPORT_SYMBOL(blk_get_backing_dev_info);
113
114void blk_rq_init(struct request_queue *q, struct request *rq)
115{
116    memset(rq, 0, sizeof(*rq));
117
118    INIT_LIST_HEAD(&rq->queuelist);
119    INIT_LIST_HEAD(&rq->timeout_list);
120    rq->cpu = -1;
121    rq->q = q;
122    rq->__sector = (sector_t) -1;
123    INIT_HLIST_NODE(&rq->hash);
124    RB_CLEAR_NODE(&rq->rb_node);
125    rq->cmd = rq->__cmd;
126    rq->cmd_len = BLK_MAX_CDB;
127    rq->tag = -1;
128    rq->ref_count = 1;
129    rq->start_time = jiffies;
130}
131EXPORT_SYMBOL(blk_rq_init);
132
133static void req_bio_endio(struct request *rq, struct bio *bio,
134              unsigned int nbytes, int error)
135{
136    struct request_queue *q = rq->q;
137
138    if (&q->bar_rq != rq) {
139        if (error)
140            clear_bit(BIO_UPTODATE, &bio->bi_flags);
141        else if (!test_bit(BIO_UPTODATE, &bio->bi_flags))
142            error = -EIO;
143
144        if (unlikely(nbytes > bio->bi_size)) {
145            printk(KERN_ERR "%s: want %u bytes done, %u left\n",
146                   __func__, nbytes, bio->bi_size);
147            nbytes = bio->bi_size;
148        }
149
150        if (unlikely(rq->cmd_flags & REQ_QUIET))
151            set_bit(BIO_QUIET, &bio->bi_flags);
152
153        bio->bi_size -= nbytes;
154        bio->bi_sector += (nbytes >> 9);
155
156        if (bio_integrity(bio))
157            bio_integrity_advance(bio, nbytes);
158
159        if (bio->bi_size == 0)
160            bio_endio(bio, error);
161    } else {
162
163        /*
164         * Okay, this is the barrier request in progress, just
165         * record the error;
166         */
167        if (error && !q->orderr)
168            q->orderr = error;
169    }
170}
171
172void blk_dump_rq_flags(struct request *rq, char *msg)
173{
174    int bit;
175
176    printk(KERN_INFO "%s: dev %s: type=%x, flags=%x\n", msg,
177        rq->rq_disk ? rq->rq_disk->disk_name : "?", rq->cmd_type,
178        rq->cmd_flags);
179
180    printk(KERN_INFO " sector %llu, nr/cnr %u/%u\n",
181           (unsigned long long)blk_rq_pos(rq),
182           blk_rq_sectors(rq), blk_rq_cur_sectors(rq));
183    printk(KERN_INFO " bio %p, biotail %p, buffer %p, len %u\n",
184           rq->bio, rq->biotail, rq->buffer, blk_rq_bytes(rq));
185
186    if (blk_pc_request(rq)) {
187        printk(KERN_INFO " cdb: ");
188        for (bit = 0; bit < BLK_MAX_CDB; bit++)
189            printk("%02x ", rq->cmd[bit]);
190        printk("\n");
191    }
192}
193EXPORT_SYMBOL(blk_dump_rq_flags);
194
195/*
196 * "plug" the device if there are no outstanding requests: this will
197 * force the transfer to start only after we have put all the requests
198 * on the list.
199 *
200 * This is called with interrupts off and no requests on the queue and
201 * with the queue lock held.
202 */
203void blk_plug_device(struct request_queue *q)
204{
205    WARN_ON(!irqs_disabled());
206
207    /*
208     * don't plug a stopped queue, it must be paired with blk_start_queue()
209     * which will restart the queueing
210     */
211    if (blk_queue_stopped(q))
212        return;
213
214    if (!queue_flag_test_and_set(QUEUE_FLAG_PLUGGED, q)) {
215        mod_timer(&q->unplug_timer, jiffies + q->unplug_delay);
216        trace_block_plug(q);
217    }
218}
219EXPORT_SYMBOL(blk_plug_device);
220
221/**
222 * blk_plug_device_unlocked - plug a device without queue lock held
223 * @q: The &struct request_queue to plug
224 *
225 * Description:
226 * Like @blk_plug_device(), but grabs the queue lock and disables
227 * interrupts.
228 **/
229void blk_plug_device_unlocked(struct request_queue *q)
230{
231    unsigned long flags;
232
233    spin_lock_irqsave(q->queue_lock, flags);
234    blk_plug_device(q);
235    spin_unlock_irqrestore(q->queue_lock, flags);
236}
237EXPORT_SYMBOL(blk_plug_device_unlocked);
238
239/*
240 * remove the queue from the plugged list, if present. called with
241 * queue lock held and interrupts disabled.
242 */
243int blk_remove_plug(struct request_queue *q)
244{
245    WARN_ON(!irqs_disabled());
246
247    if (!queue_flag_test_and_clear(QUEUE_FLAG_PLUGGED, q))
248        return 0;
249
250    del_timer(&q->unplug_timer);
251    return 1;
252}
253EXPORT_SYMBOL(blk_remove_plug);
254
255/*
256 * remove the plug and let it rip..
257 */
258void __generic_unplug_device(struct request_queue *q)
259{
260    if (unlikely(blk_queue_stopped(q)))
261        return;
262    if (!blk_remove_plug(q) && !blk_queue_nonrot(q))
263        return;
264
265    q->request_fn(q);
266}
267
268/**
269 * generic_unplug_device - fire a request queue
270 * @q: The &struct request_queue in question
271 *
272 * Description:
273 * Linux uses plugging to build bigger requests queues before letting
274 * the device have at them. If a queue is plugged, the I/O scheduler
275 * is still adding and merging requests on the queue. Once the queue
276 * gets unplugged, the request_fn defined for the queue is invoked and
277 * transfers started.
278 **/
279void generic_unplug_device(struct request_queue *q)
280{
281    if (blk_queue_plugged(q)) {
282        spin_lock_irq(q->queue_lock);
283        __generic_unplug_device(q);
284        spin_unlock_irq(q->queue_lock);
285    }
286}
287EXPORT_SYMBOL(generic_unplug_device);
288
289static void blk_backing_dev_unplug(struct backing_dev_info *bdi,
290                   struct page *page)
291{
292    struct request_queue *q = bdi->unplug_io_data;
293
294    blk_unplug(q);
295}
296
297void blk_unplug_work(struct work_struct *work)
298{
299    struct request_queue *q =
300        container_of(work, struct request_queue, unplug_work);
301
302    trace_block_unplug_io(q);
303    q->unplug_fn(q);
304}
305
306void blk_unplug_timeout(unsigned long data)
307{
308    struct request_queue *q = (struct request_queue *)data;
309
310    trace_block_unplug_timer(q);
311    kblockd_schedule_work(q, &q->unplug_work);
312}
313
314void blk_unplug(struct request_queue *q)
315{
316    /*
317     * devices don't necessarily have an ->unplug_fn defined
318     */
319    if (q->unplug_fn) {
320        trace_block_unplug_io(q);
321        q->unplug_fn(q);
322    }
323}
324EXPORT_SYMBOL(blk_unplug);
325
326/**
327 * blk_start_queue - restart a previously stopped queue
328 * @q: The &struct request_queue in question
329 *
330 * Description:
331 * blk_start_queue() will clear the stop flag on the queue, and call
332 * the request_fn for the queue if it was in a stopped state when
333 * entered. Also see blk_stop_queue(). Queue lock must be held.
334 **/
335void blk_start_queue(struct request_queue *q)
336{
337    WARN_ON(!irqs_disabled());
338
339    queue_flag_clear(QUEUE_FLAG_STOPPED, q);
340    __blk_run_queue(q);
341}
342EXPORT_SYMBOL(blk_start_queue);
343
344/**
345 * blk_stop_queue - stop a queue
346 * @q: The &struct request_queue in question
347 *
348 * Description:
349 * The Linux block layer assumes that a block driver will consume all
350 * entries on the request queue when the request_fn strategy is called.
351 * Often this will not happen, because of hardware limitations (queue
352 * depth settings). If a device driver gets a 'queue full' response,
353 * or if it simply chooses not to queue more I/O at one point, it can
354 * call this function to prevent the request_fn from being called until
355 * the driver has signalled it's ready to go again. This happens by calling
356 * blk_start_queue() to restart queue operations. Queue lock must be held.
357 **/
358void blk_stop_queue(struct request_queue *q)
359{
360    blk_remove_plug(q);
361    queue_flag_set(QUEUE_FLAG_STOPPED, q);
362}
363EXPORT_SYMBOL(blk_stop_queue);
364
365/**
366 * blk_sync_queue - cancel any pending callbacks on a queue
367 * @q: the queue
368 *
369 * Description:
370 * The block layer may perform asynchronous callback activity
371 * on a queue, such as calling the unplug function after a timeout.
372 * A block device may call blk_sync_queue to ensure that any
373 * such activity is cancelled, thus allowing it to release resources
374 * that the callbacks might use. The caller must already have made sure
375 * that its ->make_request_fn will not re-add plugging prior to calling
376 * this function.
377 *
378 */
379void blk_sync_queue(struct request_queue *q)
380{
381    del_timer_sync(&q->unplug_timer);
382    del_timer_sync(&q->timeout);
383    cancel_work_sync(&q->unplug_work);
384}
385EXPORT_SYMBOL(blk_sync_queue);
386
387/**
388 * __blk_run_queue - run a single device queue
389 * @q: The queue to run
390 *
391 * Description:
392 * See @blk_run_queue. This variant must be called with the queue lock
393 * held and interrupts disabled.
394 *
395 */
396void __blk_run_queue(struct request_queue *q)
397{
398    blk_remove_plug(q);
399
400    if (unlikely(blk_queue_stopped(q)))
401        return;
402
403    if (elv_queue_empty(q))
404        return;
405
406    /*
407     * Only recurse once to avoid overrunning the stack, let the unplug
408     * handling reinvoke the handler shortly if we already got there.
409     */
410    if (!queue_flag_test_and_set(QUEUE_FLAG_REENTER, q)) {
411        q->request_fn(q);
412        queue_flag_clear(QUEUE_FLAG_REENTER, q);
413    } else {
414        queue_flag_set(QUEUE_FLAG_PLUGGED, q);
415        kblockd_schedule_work(q, &q->unplug_work);
416    }
417}
418EXPORT_SYMBOL(__blk_run_queue);
419
420/**
421 * blk_run_queue - run a single device queue
422 * @q: The queue to run
423 *
424 * Description:
425 * Invoke request handling on this queue, if it has pending work to do.
426 * May be used to restart queueing when a request has completed.
427 */
428void blk_run_queue(struct request_queue *q)
429{
430    unsigned long flags;
431
432    spin_lock_irqsave(q->queue_lock, flags);
433    __blk_run_queue(q);
434    spin_unlock_irqrestore(q->queue_lock, flags);
435}
436EXPORT_SYMBOL(blk_run_queue);
437
438void blk_put_queue(struct request_queue *q)
439{
440    kobject_put(&q->kobj);
441}
442
443void blk_cleanup_queue(struct request_queue *q)
444{
445    /*
446     * We know we have process context here, so we can be a little
447     * cautious and ensure that pending block actions on this device
448     * are done before moving on. Going into this function, we should
449     * not have processes doing IO to this device.
450     */
451    blk_sync_queue(q);
452
453    mutex_lock(&q->sysfs_lock);
454    queue_flag_set_unlocked(QUEUE_FLAG_DEAD, q);
455    mutex_unlock(&q->sysfs_lock);
456
457    if (q->elevator)
458        elevator_exit(q->elevator);
459
460    blk_put_queue(q);
461}
462EXPORT_SYMBOL(blk_cleanup_queue);
463
464static int blk_init_free_list(struct request_queue *q)
465{
466    struct request_list *rl = &q->rq;
467
468    rl->count[BLK_RW_SYNC] = rl->count[BLK_RW_ASYNC] = 0;
469    rl->starved[BLK_RW_SYNC] = rl->starved[BLK_RW_ASYNC] = 0;
470    rl->elvpriv = 0;
471    init_waitqueue_head(&rl->wait[BLK_RW_SYNC]);
472    init_waitqueue_head(&rl->wait[BLK_RW_ASYNC]);
473
474    rl->rq_pool = mempool_create_node(BLKDEV_MIN_RQ, mempool_alloc_slab,
475                mempool_free_slab, request_cachep, q->node);
476
477    if (!rl->rq_pool)
478        return -ENOMEM;
479
480    return 0;
481}
482
483struct request_queue *blk_alloc_queue(gfp_t gfp_mask)
484{
485    return blk_alloc_queue_node(gfp_mask, -1);
486}
487EXPORT_SYMBOL(blk_alloc_queue);
488
489struct request_queue *blk_alloc_queue_node(gfp_t gfp_mask, int node_id)
490{
491    struct request_queue *q;
492    int err;
493
494    q = kmem_cache_alloc_node(blk_requestq_cachep,
495                gfp_mask | __GFP_ZERO, node_id);
496    if (!q)
497        return NULL;
498
499    q->backing_dev_info.unplug_io_fn = blk_backing_dev_unplug;
500    q->backing_dev_info.unplug_io_data = q;
501    q->backing_dev_info.ra_pages =
502            (VM_MAX_READAHEAD * 1024) / PAGE_CACHE_SIZE;
503    q->backing_dev_info.state = 0;
504    q->backing_dev_info.capabilities = BDI_CAP_MAP_COPY;
505    q->backing_dev_info.name = "block";
506
507    err = bdi_init(&q->backing_dev_info);
508    if (err) {
509        kmem_cache_free(blk_requestq_cachep, q);
510        return NULL;
511    }
512
513    init_timer(&q->unplug_timer);
514    setup_timer(&q->timeout, blk_rq_timed_out_timer, (unsigned long) q);
515    INIT_LIST_HEAD(&q->timeout_list);
516    INIT_WORK(&q->unplug_work, blk_unplug_work);
517
518    kobject_init(&q->kobj, &blk_queue_ktype);
519
520    mutex_init(&q->sysfs_lock);
521    spin_lock_init(&q->__queue_lock);
522
523    return q;
524}
525EXPORT_SYMBOL(blk_alloc_queue_node);
526
527/**
528 * blk_init_queue - prepare a request queue for use with a block device
529 * @rfn: The function to be called to process requests that have been
530 * placed on the queue.
531 * @lock: Request queue spin lock
532 *
533 * Description:
534 * If a block device wishes to use the standard request handling procedures,
535 * which sorts requests and coalesces adjacent requests, then it must
536 * call blk_init_queue(). The function @rfn will be called when there
537 * are requests on the queue that need to be processed. If the device
538 * supports plugging, then @rfn may not be called immediately when requests
539 * are available on the queue, but may be called at some time later instead.
540 * Plugged queues are generally unplugged when a buffer belonging to one
541 * of the requests on the queue is needed, or due to memory pressure.
542 *
543 * @rfn is not required, or even expected, to remove all requests off the
544 * queue, but only as many as it can handle at a time. If it does leave
545 * requests on the queue, it is responsible for arranging that the requests
546 * get dealt with eventually.
547 *
548 * The queue spin lock must be held while manipulating the requests on the
549 * request queue; this lock will be taken also from interrupt context, so irq
550 * disabling is needed for it.
551 *
552 * Function returns a pointer to the initialized request queue, or %NULL if
553 * it didn't succeed.
554 *
555 * Note:
556 * blk_init_queue() must be paired with a blk_cleanup_queue() call
557 * when the block device is deactivated (such as at module unload).
558 **/
559
560struct request_queue *blk_init_queue(request_fn_proc *rfn, spinlock_t *lock)
561{
562    return blk_init_queue_node(rfn, lock, -1);
563}
564EXPORT_SYMBOL(blk_init_queue);
565
566struct request_queue *
567blk_init_queue_node(request_fn_proc *rfn, spinlock_t *lock, int node_id)
568{
569    struct request_queue *q = blk_alloc_queue_node(GFP_KERNEL, node_id);
570
571    if (!q)
572        return NULL;
573
574    q->node = node_id;
575    if (blk_init_free_list(q)) {
576        kmem_cache_free(blk_requestq_cachep, q);
577        return NULL;
578    }
579
580    q->request_fn = rfn;
581    q->prep_rq_fn = NULL;
582    q->unplug_fn = generic_unplug_device;
583    q->queue_flags = QUEUE_FLAG_DEFAULT;
584    q->queue_lock = lock;
585
586    /*
587     * This also sets hw/phys segments, boundary and size
588     */
589    blk_queue_make_request(q, __make_request);
590
591    q->sg_reserved_size = INT_MAX;
592
593    /*
594     * all done
595     */
596    if (!elevator_init(q, NULL)) {
597        blk_queue_congestion_threshold(q);
598        return q;
599    }
600
601    blk_put_queue(q);
602    return NULL;
603}
604EXPORT_SYMBOL(blk_init_queue_node);
605
606int blk_get_queue(struct request_queue *q)
607{
608    if (likely(!test_bit(QUEUE_FLAG_DEAD, &q->queue_flags))) {
609        kobject_get(&q->kobj);
610        return 0;
611    }
612
613    return 1;
614}
615
616static inline void blk_free_request(struct request_queue *q, struct request *rq)
617{
618    if (rq->cmd_flags & REQ_ELVPRIV)
619        elv_put_request(q, rq);
620    mempool_free(rq, q->rq.rq_pool);
621}
622
623static struct request *
624blk_alloc_request(struct request_queue *q, int flags, int priv, gfp_t gfp_mask)
625{
626    struct request *rq = mempool_alloc(q->rq.rq_pool, gfp_mask);
627
628    if (!rq)
629        return NULL;
630
631    blk_rq_init(q, rq);
632
633    rq->cmd_flags = flags | REQ_ALLOCED;
634
635    if (priv) {
636        if (unlikely(elv_set_request(q, rq, gfp_mask))) {
637            mempool_free(rq, q->rq.rq_pool);
638            return NULL;
639        }
640        rq->cmd_flags |= REQ_ELVPRIV;
641    }
642
643    return rq;
644}
645
646/*
647 * ioc_batching returns true if the ioc is a valid batching request and
648 * should be given priority access to a request.
649 */
650static inline int ioc_batching(struct request_queue *q, struct io_context *ioc)
651{
652    if (!ioc)
653        return 0;
654
655    /*
656     * Make sure the process is able to allocate at least 1 request
657     * even if the batch times out, otherwise we could theoretically
658     * lose wakeups.
659     */
660    return ioc->nr_batch_requests == q->nr_batching ||
661        (ioc->nr_batch_requests > 0
662        && time_before(jiffies, ioc->last_waited + BLK_BATCH_TIME));
663}
664
665/*
666 * ioc_set_batching sets ioc to be a new "batcher" if it is not one. This
667 * will cause the process to be a "batcher" on all queues in the system. This
668 * is the behaviour we want though - once it gets a wakeup it should be given
669 * a nice run.
670 */
671static void ioc_set_batching(struct request_queue *q, struct io_context *ioc)
672{
673    if (!ioc || ioc_batching(q, ioc))
674        return;
675
676    ioc->nr_batch_requests = q->nr_batching;
677    ioc->last_waited = jiffies;
678}
679
680static void __freed_request(struct request_queue *q, int sync)
681{
682    struct request_list *rl = &q->rq;
683
684    if (rl->count[sync] < queue_congestion_off_threshold(q))
685        blk_clear_queue_congested(q, sync);
686
687    if (rl->count[sync] + 1 <= q->nr_requests) {
688        if (waitqueue_active(&rl->wait[sync]))
689            wake_up(&rl->wait[sync]);
690
691        blk_clear_queue_full(q, sync);
692    }
693}
694
695/*
696 * A request has just been released. Account for it, update the full and
697 * congestion status, wake up any waiters. Called under q->queue_lock.
698 */
699static void freed_request(struct request_queue *q, int sync, int priv)
700{
701    struct request_list *rl = &q->rq;
702
703    rl->count[sync]--;
704    if (priv)
705        rl->elvpriv--;
706
707    __freed_request(q, sync);
708
709    if (unlikely(rl->starved[sync ^ 1]))
710        __freed_request(q, sync ^ 1);
711}
712
713/*
714 * Get a free request, queue_lock must be held.
715 * Returns NULL on failure, with queue_lock held.
716 * Returns !NULL on success, with queue_lock *not held*.
717 */
718static struct request *get_request(struct request_queue *q, int rw_flags,
719                   struct bio *bio, gfp_t gfp_mask)
720{
721    struct request *rq = NULL;
722    struct request_list *rl = &q->rq;
723    struct io_context *ioc = NULL;
724    const bool is_sync = rw_is_sync(rw_flags) != 0;
725    int may_queue, priv;
726
727    may_queue = elv_may_queue(q, rw_flags);
728    if (may_queue == ELV_MQUEUE_NO)
729        goto rq_starved;
730
731    if (rl->count[is_sync]+1 >= queue_congestion_on_threshold(q)) {
732        if (rl->count[is_sync]+1 >= q->nr_requests) {
733            ioc = current_io_context(GFP_ATOMIC, q->node);
734            /*
735             * The queue will fill after this allocation, so set
736             * it as full, and mark this process as "batching".
737             * This process will be allowed to complete a batch of
738             * requests, others will be blocked.
739             */
740            if (!blk_queue_full(q, is_sync)) {
741                ioc_set_batching(q, ioc);
742                blk_set_queue_full(q, is_sync);
743            } else {
744                if (may_queue != ELV_MQUEUE_MUST
745                        && !ioc_batching(q, ioc)) {
746                    /*
747                     * The queue is full and the allocating
748                     * process is not a "batcher", and not
749                     * exempted by the IO scheduler
750                     */
751                    goto out;
752                }
753            }
754        }
755        blk_set_queue_congested(q, is_sync);
756    }
757
758    /*
759     * Only allow batching queuers to allocate up to 50% over the defined
760     * limit of requests, otherwise we could have thousands of requests
761     * allocated with any setting of ->nr_requests
762     */
763    if (rl->count[is_sync] >= (3 * q->nr_requests / 2))
764        goto out;
765
766    rl->count[is_sync]++;
767    rl->starved[is_sync] = 0;
768
769    priv = !test_bit(QUEUE_FLAG_ELVSWITCH, &q->queue_flags);
770    if (priv)
771        rl->elvpriv++;
772
773    if (blk_queue_io_stat(q))
774        rw_flags |= REQ_IO_STAT;
775    spin_unlock_irq(q->queue_lock);
776
777    rq = blk_alloc_request(q, rw_flags, priv, gfp_mask);
778    if (unlikely(!rq)) {
779        /*
780         * Allocation failed presumably due to memory. Undo anything
781         * we might have messed up.
782         *
783         * Allocating task should really be put onto the front of the
784         * wait queue, but this is pretty rare.
785         */
786        spin_lock_irq(q->queue_lock);
787        freed_request(q, is_sync, priv);
788
789        /*
790         * in the very unlikely event that allocation failed and no
791         * requests for this direction was pending, mark us starved
792         * so that freeing of a request in the other direction will
793         * notice us. another possible fix would be to split the
794         * rq mempool into READ and WRITE
795         */
796rq_starved:
797        if (unlikely(rl->count[is_sync] == 0))
798            rl->starved[is_sync] = 1;
799
800        goto out;
801    }
802
803    /*
804     * ioc may be NULL here, and ioc_batching will be false. That's
805     * OK, if the queue is under the request limit then requests need
806     * not count toward the nr_batch_requests limit. There will always
807     * be some limit enforced by BLK_BATCH_TIME.
808     */
809    if (ioc_batching(q, ioc))
810        ioc->nr_batch_requests--;
811
812    trace_block_getrq(q, bio, rw_flags & 1);
813out:
814    return rq;
815}
816
817/*
818 * No available requests for this queue, unplug the device and wait for some
819 * requests to become available.
820 *
821 * Called with q->queue_lock held, and returns with it unlocked.
822 */
823static struct request *get_request_wait(struct request_queue *q, int rw_flags,
824                    struct bio *bio)
825{
826    const bool is_sync = rw_is_sync(rw_flags) != 0;
827    struct request *rq;
828
829    rq = get_request(q, rw_flags, bio, GFP_NOIO);
830    while (!rq) {
831        DEFINE_WAIT(wait);
832        struct io_context *ioc;
833        struct request_list *rl = &q->rq;
834
835        prepare_to_wait_exclusive(&rl->wait[is_sync], &wait,
836                TASK_UNINTERRUPTIBLE);
837
838        trace_block_sleeprq(q, bio, rw_flags & 1);
839
840        __generic_unplug_device(q);
841        spin_unlock_irq(q->queue_lock);
842        io_schedule();
843
844        /*
845         * After sleeping, we become a "batching" process and
846         * will be able to allocate at least one request, and
847         * up to a big batch of them for a small period time.
848         * See ioc_batching, ioc_set_batching
849         */
850        ioc = current_io_context(GFP_NOIO, q->node);
851        ioc_set_batching(q, ioc);
852
853        spin_lock_irq(q->queue_lock);
854        finish_wait(&rl->wait[is_sync], &wait);
855
856        rq = get_request(q, rw_flags, bio, GFP_NOIO);
857    };
858
859    return rq;
860}
861
862struct request *blk_get_request(struct request_queue *q, int rw, gfp_t gfp_mask)
863{
864    struct request *rq;
865
866    BUG_ON(rw != READ && rw != WRITE);
867
868    spin_lock_irq(q->queue_lock);
869    if (gfp_mask & __GFP_WAIT) {
870        rq = get_request_wait(q, rw, NULL);
871    } else {
872        rq = get_request(q, rw, NULL, gfp_mask);
873        if (!rq)
874            spin_unlock_irq(q->queue_lock);
875    }
876    /* q->queue_lock is unlocked at this point */
877
878    return rq;
879}
880EXPORT_SYMBOL(blk_get_request);
881
882/**
883 * blk_make_request - given a bio, allocate a corresponding struct request.
884 * @q: target request queue
885 * @bio: The bio describing the memory mappings that will be submitted for IO.
886 * It may be a chained-bio properly constructed by block/bio layer.
887 * @gfp_mask: gfp flags to be used for memory allocation
888 *
889 * blk_make_request is the parallel of generic_make_request for BLOCK_PC
890 * type commands. Where the struct request needs to be farther initialized by
891 * the caller. It is passed a &struct bio, which describes the memory info of
892 * the I/O transfer.
893 *
894 * The caller of blk_make_request must make sure that bi_io_vec
895 * are set to describe the memory buffers. That bio_data_dir() will return
896 * the needed direction of the request. (And all bio's in the passed bio-chain
897 * are properly set accordingly)
898 *
899 * If called under none-sleepable conditions, mapped bio buffers must not
900 * need bouncing, by calling the appropriate masked or flagged allocator,
901 * suitable for the target device. Otherwise the call to blk_queue_bounce will
902 * BUG.
903 *
904 * WARNING: When allocating/cloning a bio-chain, careful consideration should be
905 * given to how you allocate bios. In particular, you cannot use __GFP_WAIT for
906 * anything but the first bio in the chain. Otherwise you risk waiting for IO
907 * completion of a bio that hasn't been submitted yet, thus resulting in a
908 * deadlock. Alternatively bios should be allocated using bio_kmalloc() instead
909 * of bio_alloc(), as that avoids the mempool deadlock.
910 * If possible a big IO should be split into smaller parts when allocation
911 * fails. Partial allocation should not be an error, or you risk a live-lock.
912 */
913struct request *blk_make_request(struct request_queue *q, struct bio *bio,
914                 gfp_t gfp_mask)
915{
916    struct request *rq = blk_get_request(q, bio_data_dir(bio), gfp_mask);
917
918    if (unlikely(!rq))
919        return ERR_PTR(-ENOMEM);
920
921    for_each_bio(bio) {
922        struct bio *bounce_bio = bio;
923        int ret;
924
925        blk_queue_bounce(q, &bounce_bio);
926        ret = blk_rq_append_bio(q, rq, bounce_bio);
927        if (unlikely(ret)) {
928            blk_put_request(rq);
929            return ERR_PTR(ret);
930        }
931    }
932
933    return rq;
934}
935EXPORT_SYMBOL(blk_make_request);
936
937/**
938 * blk_requeue_request - put a request back on queue
939 * @q: request queue where request should be inserted
940 * @rq: request to be inserted
941 *
942 * Description:
943 * Drivers often keep queueing requests until the hardware cannot accept
944 * more, when that condition happens we need to put the request back
945 * on the queue. Must be called with queue lock held.
946 */
947void blk_requeue_request(struct request_queue *q, struct request *rq)
948{
949    blk_delete_timer(rq);
950    blk_clear_rq_complete(rq);
951    trace_block_rq_requeue(q, rq);
952
953    if (blk_rq_tagged(rq))
954        blk_queue_end_tag(q, rq);
955
956    BUG_ON(blk_queued_rq(rq));
957
958    elv_requeue_request(q, rq);
959}
960EXPORT_SYMBOL(blk_requeue_request);
961
962/**
963 * blk_insert_request - insert a special request into a request queue
964 * @q: request queue where request should be inserted
965 * @rq: request to be inserted
966 * @at_head: insert request at head or tail of queue
967 * @data: private data
968 *
969 * Description:
970 * Many block devices need to execute commands asynchronously, so they don't
971 * block the whole kernel from preemption during request execution. This is
972 * accomplished normally by inserting aritficial requests tagged as
973 * REQ_TYPE_SPECIAL in to the corresponding request queue, and letting them
974 * be scheduled for actual execution by the request queue.
975 *
976 * We have the option of inserting the head or the tail of the queue.
977 * Typically we use the tail for new ioctls and so forth. We use the head
978 * of the queue for things like a QUEUE_FULL message from a device, or a
979 * host that is unable to accept a particular command.
980 */
981void blk_insert_request(struct request_queue *q, struct request *rq,
982            int at_head, void *data)
983{
984    int where = at_head ? ELEVATOR_INSERT_FRONT : ELEVATOR_INSERT_BACK;
985    unsigned long flags;
986
987    /*
988     * tell I/O scheduler that this isn't a regular read/write (ie it
989     * must not attempt merges on this) and that it acts as a soft
990     * barrier
991     */
992    rq->cmd_type = REQ_TYPE_SPECIAL;
993
994    rq->special = data;
995
996    spin_lock_irqsave(q->queue_lock, flags);
997
998    /*
999     * If command is tagged, release the tag
1000     */
1001    if (blk_rq_tagged(rq))
1002        blk_queue_end_tag(q, rq);
1003
1004    drive_stat_acct(rq, 1);
1005    __elv_add_request(q, rq, where, 0);
1006    __blk_run_queue(q);
1007    spin_unlock_irqrestore(q->queue_lock, flags);
1008}
1009EXPORT_SYMBOL(blk_insert_request);
1010
1011/*
1012 * add-request adds a request to the linked list.
1013 * queue lock is held and interrupts disabled, as we muck with the
1014 * request queue list.
1015 */
1016static inline void add_request(struct request_queue *q, struct request *req)
1017{
1018    drive_stat_acct(req, 1);
1019
1020    /*
1021     * elevator indicated where it wants this request to be
1022     * inserted at elevator_merge time
1023     */
1024    __elv_add_request(q, req, ELEVATOR_INSERT_SORT, 0);
1025}
1026
1027static void part_round_stats_single(int cpu, struct hd_struct *part,
1028                    unsigned long now)
1029{
1030    if (now == part->stamp)
1031        return;
1032
1033    if (part_in_flight(part)) {
1034        __part_stat_add(cpu, part, time_in_queue,
1035                part_in_flight(part) * (now - part->stamp));
1036        __part_stat_add(cpu, part, io_ticks, (now - part->stamp));
1037    }
1038    part->stamp = now;
1039}
1040
1041/**
1042 * part_round_stats() - Round off the performance stats on a struct disk_stats.
1043 * @cpu: cpu number for stats access
1044 * @part: target partition
1045 *
1046 * The average IO queue length and utilisation statistics are maintained
1047 * by observing the current state of the queue length and the amount of
1048 * time it has been in this state for.
1049 *
1050 * Normally, that accounting is done on IO completion, but that can result
1051 * in more than a second's worth of IO being accounted for within any one
1052 * second, leading to >100% utilisation. To deal with that, we call this
1053 * function to do a round-off before returning the results when reading
1054 * /proc/diskstats. This accounts immediately for all queue usage up to
1055 * the current jiffies and restarts the counters again.
1056 */
1057void part_round_stats(int cpu, struct hd_struct *part)
1058{
1059    unsigned long now = jiffies;
1060
1061    if (part->partno)
1062        part_round_stats_single(cpu, &part_to_disk(part)->part0, now);
1063    part_round_stats_single(cpu, part, now);
1064}
1065EXPORT_SYMBOL_GPL(part_round_stats);
1066
1067/*
1068 * queue lock must be held
1069 */
1070void __blk_put_request(struct request_queue *q, struct request *req)
1071{
1072    if (unlikely(!q))
1073        return;
1074    if (unlikely(--req->ref_count))
1075        return;
1076
1077    elv_completed_request(q, req);
1078
1079    /* this is a bio leak */
1080    WARN_ON(req->bio != NULL);
1081
1082    /*
1083     * Request may not have originated from ll_rw_blk. if not,
1084     * it didn't come out of our reserved rq pools
1085     */
1086    if (req->cmd_flags & REQ_ALLOCED) {
1087        int is_sync = rq_is_sync(req) != 0;
1088        int priv = req->cmd_flags & REQ_ELVPRIV;
1089
1090        BUG_ON(!list_empty(&req->queuelist));
1091        BUG_ON(!hlist_unhashed(&req->hash));
1092
1093        blk_free_request(q, req);
1094        freed_request(q, is_sync, priv);
1095    }
1096}
1097EXPORT_SYMBOL_GPL(__blk_put_request);
1098
1099void blk_put_request(struct request *req)
1100{
1101    unsigned long flags;
1102    struct request_queue *q = req->q;
1103
1104    spin_lock_irqsave(q->queue_lock, flags);
1105    __blk_put_request(q, req);
1106    spin_unlock_irqrestore(q->queue_lock, flags);
1107}
1108EXPORT_SYMBOL(blk_put_request);
1109
1110void init_request_from_bio(struct request *req, struct bio *bio)
1111{
1112    req->cpu = bio->bi_comp_cpu;
1113    req->cmd_type = REQ_TYPE_FS;
1114
1115    /*
1116     * Inherit FAILFAST from bio (for read-ahead, and explicit
1117     * FAILFAST). FAILFAST flags are identical for req and bio.
1118     */
1119    if (bio_rw_flagged(bio, BIO_RW_AHEAD))
1120        req->cmd_flags |= REQ_FAILFAST_MASK;
1121    else
1122        req->cmd_flags |= bio->bi_rw & REQ_FAILFAST_MASK;
1123
1124    if (unlikely(bio_rw_flagged(bio, BIO_RW_DISCARD))) {
1125        req->cmd_flags |= REQ_DISCARD;
1126        if (bio_rw_flagged(bio, BIO_RW_BARRIER))
1127            req->cmd_flags |= REQ_SOFTBARRIER;
1128    } else if (unlikely(bio_rw_flagged(bio, BIO_RW_BARRIER)))
1129        req->cmd_flags |= REQ_HARDBARRIER;
1130
1131    if (bio_rw_flagged(bio, BIO_RW_SYNCIO))
1132        req->cmd_flags |= REQ_RW_SYNC;
1133    if (bio_rw_flagged(bio, BIO_RW_META))
1134        req->cmd_flags |= REQ_RW_META;
1135    if (bio_rw_flagged(bio, BIO_RW_NOIDLE))
1136        req->cmd_flags |= REQ_NOIDLE;
1137
1138    req->errors = 0;
1139    req->__sector = bio->bi_sector;
1140    req->ioprio = bio_prio(bio);
1141    blk_rq_bio_prep(req->q, req, bio);
1142}
1143
1144/*
1145 * Only disabling plugging for non-rotational devices if it does tagging
1146 * as well, otherwise we do need the proper merging
1147 */
1148static inline bool queue_should_plug(struct request_queue *q)
1149{
1150    return !(blk_queue_nonrot(q) && blk_queue_tagged(q));
1151}
1152
1153static int __make_request(struct request_queue *q, struct bio *bio)
1154{
1155    struct request *req;
1156    int el_ret;
1157    unsigned int bytes = bio->bi_size;
1158    const unsigned short prio = bio_prio(bio);
1159    const bool sync = bio_rw_flagged(bio, BIO_RW_SYNCIO);
1160    const bool unplug = bio_rw_flagged(bio, BIO_RW_UNPLUG);
1161    const unsigned int ff = bio->bi_rw & REQ_FAILFAST_MASK;
1162    int rw_flags;
1163
1164    if (bio_rw_flagged(bio, BIO_RW_BARRIER) &&
1165        (q->next_ordered == QUEUE_ORDERED_NONE)) {
1166        bio_endio(bio, -EOPNOTSUPP);
1167        return 0;
1168    }
1169    /*
1170     * low level driver can indicate that it wants pages above a
1171     * certain limit bounced to low memory (ie for highmem, or even
1172     * ISA dma in theory)
1173     */
1174    blk_queue_bounce(q, &bio);
1175
1176    spin_lock_irq(q->queue_lock);
1177
1178    if (unlikely(bio_rw_flagged(bio, BIO_RW_BARRIER)) || elv_queue_empty(q))
1179        goto get_rq;
1180
1181    el_ret = elv_merge(q, &req, bio);
1182    switch (el_ret) {
1183    case ELEVATOR_BACK_MERGE:
1184        BUG_ON(!rq_mergeable(req));
1185
1186        if (!ll_back_merge_fn(q, req, bio))
1187            break;
1188
1189        trace_block_bio_backmerge(q, bio);
1190
1191        if ((req->cmd_flags & REQ_FAILFAST_MASK) != ff)
1192            blk_rq_set_mixed_merge(req);
1193
1194        req->biotail->bi_next = bio;
1195        req->biotail = bio;
1196        req->__data_len += bytes;
1197        req->ioprio = ioprio_best(req->ioprio, prio);
1198        if (!blk_rq_cpu_valid(req))
1199            req->cpu = bio->bi_comp_cpu;
1200        drive_stat_acct(req, 0);
1201        if (!attempt_back_merge(q, req))
1202            elv_merged_request(q, req, el_ret);
1203        goto out;
1204
1205    case ELEVATOR_FRONT_MERGE:
1206        BUG_ON(!rq_mergeable(req));
1207
1208        if (!ll_front_merge_fn(q, req, bio))
1209            break;
1210
1211        trace_block_bio_frontmerge(q, bio);
1212
1213        if ((req->cmd_flags & REQ_FAILFAST_MASK) != ff) {
1214            blk_rq_set_mixed_merge(req);
1215            req->cmd_flags &= ~REQ_FAILFAST_MASK;
1216            req->cmd_flags |= ff;
1217        }
1218
1219        bio->bi_next = req->bio;
1220        req->bio = bio;
1221
1222        /*
1223         * may not be valid. if the low level driver said
1224         * it didn't need a bounce buffer then it better
1225         * not touch req->buffer either...
1226         */
1227        req->buffer = bio_data(bio);
1228        req->__sector = bio->bi_sector;
1229        req->__data_len += bytes;
1230        req->ioprio = ioprio_best(req->ioprio, prio);
1231        if (!blk_rq_cpu_valid(req))
1232            req->cpu = bio->bi_comp_cpu;
1233        drive_stat_acct(req, 0);
1234        if (!attempt_front_merge(q, req))
1235            elv_merged_request(q, req, el_ret);
1236        goto out;
1237
1238    /* ELV_NO_MERGE: elevator says don't/can't merge. */
1239    default:
1240        ;
1241    }
1242
1243get_rq:
1244    /*
1245     * This sync check and mask will be re-done in init_request_from_bio(),
1246     * but we need to set it earlier to expose the sync flag to the
1247     * rq allocator and io schedulers.
1248     */
1249    rw_flags = bio_data_dir(bio);
1250    if (sync)
1251        rw_flags |= REQ_RW_SYNC;
1252
1253    /*
1254     * Grab a free request. This is might sleep but can not fail.
1255     * Returns with the queue unlocked.
1256     */
1257    req = get_request_wait(q, rw_flags, bio);
1258
1259    /*
1260     * After dropping the lock and possibly sleeping here, our request
1261     * may now be mergeable after it had proven unmergeable (above).
1262     * We don't worry about that case for efficiency. It won't happen
1263     * often, and the elevators are able to handle it.
1264     */
1265    init_request_from_bio(req, bio);
1266
1267    spin_lock_irq(q->queue_lock);
1268    if (test_bit(QUEUE_FLAG_SAME_COMP, &q->queue_flags) ||
1269        bio_flagged(bio, BIO_CPU_AFFINE))
1270        req->cpu = blk_cpu_to_group(smp_processor_id());
1271    if (queue_should_plug(q) && elv_queue_empty(q))
1272        blk_plug_device(q);
1273    add_request(q, req);
1274out:
1275    if (unplug || !queue_should_plug(q))
1276        __generic_unplug_device(q);
1277    spin_unlock_irq(q->queue_lock);
1278    return 0;
1279}
1280
1281/*
1282 * If bio->bi_dev is a partition, remap the location
1283 */
1284static inline void blk_partition_remap(struct bio *bio)
1285{
1286    struct block_device *bdev = bio->bi_bdev;
1287
1288    if (bio_sectors(bio) && bdev != bdev->bd_contains) {
1289        struct hd_struct *p = bdev->bd_part;
1290
1291        bio->bi_sector += p->start_sect;
1292        bio->bi_bdev = bdev->bd_contains;
1293
1294        trace_block_remap(bdev_get_queue(bio->bi_bdev), bio,
1295                    bdev->bd_dev,
1296                    bio->bi_sector - p->start_sect);
1297    }
1298}
1299
1300static void handle_bad_sector(struct bio *bio)
1301{
1302    char b[BDEVNAME_SIZE];
1303
1304    printk(KERN_INFO "attempt to access beyond end of device\n");
1305    printk(KERN_INFO "%s: rw=%ld, want=%Lu, limit=%Lu\n",
1306            bdevname(bio->bi_bdev, b),
1307            bio->bi_rw,
1308            (unsigned long long)bio->bi_sector + bio_sectors(bio),
1309            (long long)(bio->bi_bdev->bd_inode->i_size >> 9));
1310
1311    set_bit(BIO_EOF, &bio->bi_flags);
1312}
1313
1314#ifdef CONFIG_FAIL_MAKE_REQUEST
1315
1316static DECLARE_FAULT_ATTR(fail_make_request);
1317
1318static int __init setup_fail_make_request(char *str)
1319{
1320    return setup_fault_attr(&fail_make_request, str);
1321}
1322__setup("fail_make_request=", setup_fail_make_request);
1323
1324static int should_fail_request(struct bio *bio)
1325{
1326    struct hd_struct *part = bio->bi_bdev->bd_part;
1327
1328    if (part_to_disk(part)->part0.make_it_fail || part->make_it_fail)
1329        return should_fail(&fail_make_request, bio->bi_size);
1330
1331    return 0;
1332}
1333
1334static int __init fail_make_request_debugfs(void)
1335{
1336    return init_fault_attr_dentries(&fail_make_request,
1337                    "fail_make_request");
1338}
1339
1340late_initcall(fail_make_request_debugfs);
1341
1342#else /* CONFIG_FAIL_MAKE_REQUEST */
1343
1344static inline int should_fail_request(struct bio *bio)
1345{
1346    return 0;
1347}
1348
1349#endif /* CONFIG_FAIL_MAKE_REQUEST */
1350
1351/*
1352 * Check whether this bio extends beyond the end of the device.
1353 */
1354static inline int bio_check_eod(struct bio *bio, unsigned int nr_sectors)
1355{
1356    sector_t maxsector;
1357
1358    if (!nr_sectors)
1359        return 0;
1360
1361    /* Test device or partition size, when known. */
1362    maxsector = bio->bi_bdev->bd_inode->i_size >> 9;
1363    if (maxsector) {
1364        sector_t sector = bio->bi_sector;
1365
1366        if (maxsector < nr_sectors || maxsector - nr_sectors < sector) {
1367            /*
1368             * This may well happen - the kernel calls bread()
1369             * without checking the size of the device, e.g., when
1370             * mounting a device.
1371             */
1372            handle_bad_sector(bio);
1373            return 1;
1374        }
1375    }
1376
1377    return 0;
1378}
1379
1380/**
1381 * generic_make_request - hand a buffer to its device driver for I/O
1382 * @bio: The bio describing the location in memory and on the device.
1383 *
1384 * generic_make_request() is used to make I/O requests of block
1385 * devices. It is passed a &struct bio, which describes the I/O that needs
1386 * to be done.
1387 *
1388 * generic_make_request() does not return any status. The
1389 * success/failure status of the request, along with notification of
1390 * completion, is delivered asynchronously through the bio->bi_end_io
1391 * function described (one day) else where.
1392 *
1393 * The caller of generic_make_request must make sure that bi_io_vec
1394 * are set to describe the memory buffer, and that bi_dev and bi_sector are
1395 * set to describe the device address, and the
1396 * bi_end_io and optionally bi_private are set to describe how
1397 * completion notification should be signaled.
1398 *
1399 * generic_make_request and the drivers it calls may use bi_next if this
1400 * bio happens to be merged with someone else, and may change bi_dev and
1401 * bi_sector for remaps as it sees fit. So the values of these fields
1402 * should NOT be depended on after the call to generic_make_request.
1403 */
1404static inline void __generic_make_request(struct bio *bio)
1405{
1406    struct request_queue *q;
1407    sector_t old_sector;
1408    int ret, nr_sectors = bio_sectors(bio);
1409    dev_t old_dev;
1410    int err = -EIO;
1411
1412    might_sleep();
1413
1414    if (bio_check_eod(bio, nr_sectors))
1415        goto end_io;
1416
1417    /*
1418     * Resolve the mapping until finished. (drivers are
1419     * still free to implement/resolve their own stacking
1420     * by explicitly returning 0)
1421     *
1422     * NOTE: we don't repeat the blk_size check for each new device.
1423     * Stacking drivers are expected to know what they are doing.
1424     */
1425    old_sector = -1;
1426    old_dev = 0;
1427    do {
1428        char b[BDEVNAME_SIZE];
1429
1430        q = bdev_get_queue(bio->bi_bdev);
1431        if (unlikely(!q)) {
1432            printk(KERN_ERR
1433                   "generic_make_request: Trying to access "
1434                "nonexistent block-device %s (%Lu)\n",
1435                bdevname(bio->bi_bdev, b),
1436                (long long) bio->bi_sector);
1437            goto end_io;
1438        }
1439
1440        if (unlikely(!bio_rw_flagged(bio, BIO_RW_DISCARD) &&
1441                 nr_sectors > queue_max_hw_sectors(q))) {
1442            printk(KERN_ERR "bio too big device %s (%u > %u)\n",
1443                   bdevname(bio->bi_bdev, b),
1444                   bio_sectors(bio),
1445                   queue_max_hw_sectors(q));
1446            goto end_io;
1447        }
1448
1449        if (unlikely(test_bit(QUEUE_FLAG_DEAD, &q->queue_flags)))
1450            goto end_io;
1451
1452        if (should_fail_request(bio))
1453            goto end_io;
1454
1455        /*
1456         * If this device has partitions, remap block n
1457         * of partition p to block n+start(p) of the disk.
1458         */
1459        blk_partition_remap(bio);
1460
1461        if (bio_integrity_enabled(bio) && bio_integrity_prep(bio))
1462            goto end_io;
1463
1464        if (old_sector != -1)
1465            trace_block_remap(q, bio, old_dev, old_sector);
1466
1467        old_sector = bio->bi_sector;
1468        old_dev = bio->bi_bdev->bd_dev;
1469
1470        if (bio_check_eod(bio, nr_sectors))
1471            goto end_io;
1472
1473        if (bio_rw_flagged(bio, BIO_RW_DISCARD) &&
1474            !blk_queue_discard(q)) {
1475            err = -EOPNOTSUPP;
1476            goto end_io;
1477        }
1478
1479        trace_block_bio_queue(q, bio);
1480
1481        ret = q->make_request_fn(q, bio);
1482    } while (ret);
1483
1484    return;
1485
1486end_io:
1487    bio_endio(bio, err);
1488}
1489
1490/*
1491 * We only want one ->make_request_fn to be active at a time,
1492 * else stack usage with stacked devices could be a problem.
1493 * So use current->bio_list to keep a list of requests
1494 * submited by a make_request_fn function.
1495 * current->bio_list is also used as a flag to say if
1496 * generic_make_request is currently active in this task or not.
1497 * If it is NULL, then no make_request is active. If it is non-NULL,
1498 * then a make_request is active, and new requests should be added
1499 * at the tail
1500 */
1501void generic_make_request(struct bio *bio)
1502{
1503    struct bio_list bio_list_on_stack;
1504
1505    if (current->bio_list) {
1506        /* make_request is active */
1507        bio_list_add(current->bio_list, bio);
1508        return;
1509    }
1510    /* following loop may be a bit non-obvious, and so deserves some
1511     * explanation.
1512     * Before entering the loop, bio->bi_next is NULL (as all callers
1513     * ensure that) so we have a list with a single bio.
1514     * We pretend that we have just taken it off a longer list, so
1515     * we assign bio_list to a pointer to the bio_list_on_stack,
1516     * thus initialising the bio_list of new bios to be
1517     * added. __generic_make_request may indeed add some more bios
1518     * through a recursive call to generic_make_request. If it
1519     * did, we find a non-NULL value in bio_list and re-enter the loop
1520     * from the top. In this case we really did just take the bio
1521     * of the top of the list (no pretending) and so remove it from
1522     * bio_list, and call into __generic_make_request again.
1523     *
1524     * The loop was structured like this to make only one call to
1525     * __generic_make_request (which is important as it is large and
1526     * inlined) and to keep the structure simple.
1527     */
1528    BUG_ON(bio->bi_next);
1529    bio_list_init(&bio_list_on_stack);
1530    current->bio_list = &bio_list_on_stack;
1531    do {
1532        __generic_make_request(bio);
1533        bio = bio_list_pop(current->bio_list);
1534    } while (bio);
1535    current->bio_list = NULL; /* deactivate */
1536}
1537EXPORT_SYMBOL(generic_make_request);
1538
1539/**
1540 * submit_bio - submit a bio to the block device layer for I/O
1541 * @rw: whether to %READ or %WRITE, or maybe to %READA (read ahead)
1542 * @bio: The &struct bio which describes the I/O
1543 *
1544 * submit_bio() is very similar in purpose to generic_make_request(), and
1545 * uses that function to do most of the work. Both are fairly rough
1546 * interfaces; @bio must be presetup and ready for I/O.
1547 *
1548 */
1549void submit_bio(int rw, struct bio *bio)
1550{
1551    int count = bio_sectors(bio);
1552
1553    bio->bi_rw |= rw;
1554
1555    /*
1556     * If it's a regular read/write or a barrier with data attached,
1557     * go through the normal accounting stuff before submission.
1558     */
1559    if (bio_has_data(bio)) {
1560        if (rw & WRITE) {
1561            count_vm_events(PGPGOUT, count);
1562        } else {
1563            task_io_account_read(bio->bi_size);
1564            count_vm_events(PGPGIN, count);
1565        }
1566
1567        if (unlikely(block_dump)) {
1568            char b[BDEVNAME_SIZE];
1569            printk(KERN_DEBUG "%s(%d): %s block %Lu on %s\n",
1570            current->comm, task_pid_nr(current),
1571                (rw & WRITE) ? "WRITE" : "READ",
1572                (unsigned long long)bio->bi_sector,
1573                bdevname(bio->bi_bdev, b));
1574        }
1575    }
1576
1577    generic_make_request(bio);
1578}
1579EXPORT_SYMBOL(submit_bio);
1580
1581/**
1582 * blk_rq_check_limits - Helper function to check a request for the queue limit
1583 * @q: the queue
1584 * @rq: the request being checked
1585 *
1586 * Description:
1587 * @rq may have been made based on weaker limitations of upper-level queues
1588 * in request stacking drivers, and it may violate the limitation of @q.
1589 * Since the block layer and the underlying device driver trust @rq
1590 * after it is inserted to @q, it should be checked against @q before
1591 * the insertion using this generic function.
1592 *
1593 * This function should also be useful for request stacking drivers
1594 * in some cases below, so export this fuction.
1595 * Request stacking drivers like request-based dm may change the queue
1596 * limits while requests are in the queue (e.g. dm's table swapping).
1597 * Such request stacking drivers should check those requests agaist
1598 * the new queue limits again when they dispatch those requests,
1599 * although such checkings are also done against the old queue limits
1600 * when submitting requests.
1601 */
1602int blk_rq_check_limits(struct request_queue *q, struct request *rq)
1603{
1604    if (blk_rq_sectors(rq) > queue_max_sectors(q) ||
1605        blk_rq_bytes(rq) > queue_max_hw_sectors(q) << 9) {
1606        printk(KERN_ERR "%s: over max size limit.\n", __func__);
1607        return -EIO;
1608    }
1609
1610    /*
1611     * queue's settings related to segment counting like q->bounce_pfn
1612     * may differ from that of other stacking queues.
1613     * Recalculate it to check the request correctly on this queue's
1614     * limitation.
1615     */
1616    blk_recalc_rq_segments(rq);
1617    if (rq->nr_phys_segments > queue_max_segments(q)) {
1618        printk(KERN_ERR "%s: over max segments limit.\n", __func__);
1619        return -EIO;
1620    }
1621
1622    return 0;
1623}
1624EXPORT_SYMBOL_GPL(blk_rq_check_limits);
1625
1626/**
1627 * blk_insert_cloned_request - Helper for stacking drivers to submit a request
1628 * @q: the queue to submit the request
1629 * @rq: the request being queued
1630 */
1631int blk_insert_cloned_request(struct request_queue *q, struct request *rq)
1632{
1633    unsigned long flags;
1634
1635    if (blk_rq_check_limits(q, rq))
1636        return -EIO;
1637
1638#ifdef CONFIG_FAIL_MAKE_REQUEST
1639    if (rq->rq_disk && rq->rq_disk->part0.make_it_fail &&
1640        should_fail(&fail_make_request, blk_rq_bytes(rq)))
1641        return -EIO;
1642#endif
1643
1644    spin_lock_irqsave(q->queue_lock, flags);
1645
1646    /*
1647     * Submitting request must be dequeued before calling this function
1648     * because it will be linked to another request_queue
1649     */
1650    BUG_ON(blk_queued_rq(rq));
1651
1652    drive_stat_acct(rq, 1);
1653    __elv_add_request(q, rq, ELEVATOR_INSERT_BACK, 0);
1654
1655    spin_unlock_irqrestore(q->queue_lock, flags);
1656
1657    return 0;
1658}
1659EXPORT_SYMBOL_GPL(blk_insert_cloned_request);
1660
1661/**
1662 * blk_rq_err_bytes - determine number of bytes till the next failure boundary
1663 * @rq: request to examine
1664 *
1665 * Description:
1666 * A request could be merge of IOs which require different failure
1667 * handling. This function determines the number of bytes which
1668 * can be failed from the beginning of the request without
1669 * crossing into area which need to be retried further.
1670 *
1671 * Return:
1672 * The number of bytes to fail.
1673 *
1674 * Context:
1675 * queue_lock must be held.
1676 */
1677unsigned int blk_rq_err_bytes(const struct request *rq)
1678{
1679    unsigned int ff = rq->cmd_flags & REQ_FAILFAST_MASK;
1680    unsigned int bytes = 0;
1681    struct bio *bio;
1682
1683    if (!(rq->cmd_flags & REQ_MIXED_MERGE))
1684        return blk_rq_bytes(rq);
1685
1686    /*
1687     * Currently the only 'mixing' which can happen is between
1688     * different fastfail types. We can safely fail portions
1689     * which have all the failfast bits that the first one has -
1690     * the ones which are at least as eager to fail as the first
1691     * one.
1692     */
1693    for (bio = rq->bio; bio; bio = bio->bi_next) {
1694        if ((bio->bi_rw & ff) != ff)
1695            break;
1696        bytes += bio->bi_size;
1697    }
1698
1699    /* this could lead to infinite loop */
1700    BUG_ON(blk_rq_bytes(rq) && !bytes);
1701    return bytes;
1702}
1703EXPORT_SYMBOL_GPL(blk_rq_err_bytes);
1704
1705static void blk_account_io_completion(struct request *req, unsigned int bytes)
1706{
1707    if (blk_do_io_stat(req)) {
1708        const int rw = rq_data_dir(req);
1709        struct hd_struct *part;
1710        int cpu;
1711
1712        cpu = part_stat_lock();
1713        part = disk_map_sector_rcu(req->rq_disk, blk_rq_pos(req));
1714        part_stat_add(cpu, part, sectors[rw], bytes >> 9);
1715        part_stat_unlock();
1716    }
1717}
1718
1719static void blk_account_io_done(struct request *req)
1720{
1721    /*
1722     * Account IO completion. bar_rq isn't accounted as a normal
1723     * IO on queueing nor completion. Accounting the containing
1724     * request is enough.
1725     */
1726    if (blk_do_io_stat(req) && req != &req->q->bar_rq) {
1727        unsigned long duration = jiffies - req->start_time;
1728        const int rw = rq_data_dir(req);
1729        struct hd_struct *part;
1730        int cpu;
1731
1732        cpu = part_stat_lock();
1733        part = disk_map_sector_rcu(req->rq_disk, blk_rq_pos(req));
1734
1735        part_stat_inc(cpu, part, ios[rw]);
1736        part_stat_add(cpu, part, ticks[rw], duration);
1737        part_round_stats(cpu, part);
1738        part_dec_in_flight(part, rw);
1739
1740        part_stat_unlock();
1741    }
1742}
1743
1744/**
1745 * blk_peek_request - peek at the top of a request queue
1746 * @q: request queue to peek at
1747 *
1748 * Description:
1749 * Return the request at the top of @q. The returned request
1750 * should be started using blk_start_request() before LLD starts
1751 * processing it.
1752 *
1753 * Return:
1754 * Pointer to the request at the top of @q if available. Null
1755 * otherwise.
1756 *
1757 * Context:
1758 * queue_lock must be held.
1759 */
1760struct request *blk_peek_request(struct request_queue *q)
1761{
1762    struct request *rq;
1763    int ret;
1764
1765    while ((rq = __elv_next_request(q)) != NULL) {
1766        if (!(rq->cmd_flags & REQ_STARTED)) {
1767            /*
1768             * This is the first time the device driver
1769             * sees this request (possibly after
1770             * requeueing). Notify IO scheduler.
1771             */
1772            if (blk_sorted_rq(rq))
1773                elv_activate_rq(q, rq);
1774
1775            /*
1776             * just mark as started even if we don't start
1777             * it, a request that has been delayed should
1778             * not be passed by new incoming requests
1779             */
1780            rq->cmd_flags |= REQ_STARTED;
1781            trace_block_rq_issue(q, rq);
1782        }
1783
1784        if (!q->boundary_rq || q->boundary_rq == rq) {
1785            q->end_sector = rq_end_sector(rq);
1786            q->boundary_rq = NULL;
1787        }
1788
1789        if (rq->cmd_flags & REQ_DONTPREP)
1790            break;
1791
1792        if (q->dma_drain_size && blk_rq_bytes(rq)) {
1793            /*
1794             * make sure space for the drain appears we
1795             * know we can do this because max_hw_segments
1796             * has been adjusted to be one fewer than the
1797             * device can handle
1798             */
1799            rq->nr_phys_segments++;
1800        }
1801
1802        if (!q->prep_rq_fn)
1803            break;
1804
1805        ret = q->prep_rq_fn(q, rq);
1806        if (ret == BLKPREP_OK) {
1807            break;
1808        } else if (ret == BLKPREP_DEFER) {
1809            /*
1810             * the request may have been (partially) prepped.
1811             * we need to keep this request in the front to
1812             * avoid resource deadlock. REQ_STARTED will
1813             * prevent other fs requests from passing this one.
1814             */
1815            if (q->dma_drain_size && blk_rq_bytes(rq) &&
1816                !(rq->cmd_flags & REQ_DONTPREP)) {
1817                /*
1818                 * remove the space for the drain we added
1819                 * so that we don't add it again
1820                 */
1821                --rq->nr_phys_segments;
1822            }
1823
1824            rq = NULL;
1825            break;
1826        } else if (ret == BLKPREP_KILL) {
1827            rq->cmd_flags |= REQ_QUIET;
1828            /*
1829             * Mark this request as started so we don't trigger
1830             * any debug logic in the end I/O path.
1831             */
1832            blk_start_request(rq);
1833            __blk_end_request_all(rq, -EIO);
1834        } else {
1835            printk(KERN_ERR "%s: bad return=%d\n", __func__, ret);
1836            break;
1837        }
1838    }
1839
1840    return rq;
1841}
1842EXPORT_SYMBOL(blk_peek_request);
1843
1844void blk_dequeue_request(struct request *rq)
1845{
1846    struct request_queue *q = rq->q;
1847
1848    BUG_ON(list_empty(&rq->queuelist));
1849    BUG_ON(ELV_ON_HASH(rq));
1850
1851    list_del_init(&rq->queuelist);
1852
1853    /*
1854     * the time frame between a request being removed from the lists
1855     * and to it is freed is accounted as io that is in progress at
1856     * the driver side.
1857     */
1858    if (blk_account_rq(rq))
1859        q->in_flight[rq_is_sync(rq)]++;
1860}
1861
1862/**
1863 * blk_start_request - start request processing on the driver
1864 * @req: request to dequeue
1865 *
1866 * Description:
1867 * Dequeue @req and start timeout timer on it. This hands off the
1868 * request to the driver.
1869 *
1870 * Block internal functions which don't want to start timer should
1871 * call blk_dequeue_request().
1872 *
1873 * Context:
1874 * queue_lock must be held.
1875 */
1876void blk_start_request(struct request *req)
1877{
1878    blk_dequeue_request(req);
1879
1880    /*
1881     * We are now handing the request to the hardware, initialize
1882     * resid_len to full count and add the timeout handler.
1883     */
1884    req->resid_len = blk_rq_bytes(req);
1885    if (unlikely(blk_bidi_rq(req)))
1886        req->next_rq->resid_len = blk_rq_bytes(req->next_rq);
1887
1888    blk_add_timer(req);
1889}
1890EXPORT_SYMBOL(blk_start_request);
1891
1892/**
1893 * blk_fetch_request - fetch a request from a request queue
1894 * @q: request queue to fetch a request from
1895 *
1896 * Description:
1897 * Return the request at the top of @q. The request is started on
1898 * return and LLD can start processing it immediately.
1899 *
1900 * Return:
1901 * Pointer to the request at the top of @q if available. Null
1902 * otherwise.
1903 *
1904 * Context:
1905 * queue_lock must be held.
1906 */
1907struct request *blk_fetch_request(struct request_queue *q)
1908{
1909    struct request *rq;
1910
1911    rq = blk_peek_request(q);
1912    if (rq)
1913        blk_start_request(rq);
1914    return rq;
1915}
1916EXPORT_SYMBOL(blk_fetch_request);
1917
1918/**
1919 * blk_update_request - Special helper function for request stacking drivers
1920 * @req: the request being processed
1921 * @error: %0 for success, < %0 for error
1922 * @nr_bytes: number of bytes to complete @req
1923 *
1924 * Description:
1925 * Ends I/O on a number of bytes attached to @req, but doesn't complete
1926 * the request structure even if @req doesn't have leftover.
1927 * If @req has leftover, sets it up for the next range of segments.
1928 *
1929 * This special helper function is only for request stacking drivers
1930 * (e.g. request-based dm) so that they can handle partial completion.
1931 * Actual device drivers should use blk_end_request instead.
1932 *
1933 * Passing the result of blk_rq_bytes() as @nr_bytes guarantees
1934 * %false return from this function.
1935 *
1936 * Return:
1937 * %false - this request doesn't have any more data
1938 * %true - this request has more data
1939 **/
1940bool blk_update_request(struct request *req, int error, unsigned int nr_bytes)
1941{
1942    int total_bytes, bio_nbytes, next_idx = 0;
1943    struct bio *bio;
1944
1945    if (!req->bio)
1946        return false;
1947
1948    trace_block_rq_complete(req->q, req);
1949
1950    /*
1951     * For fs requests, rq is just carrier of independent bio's
1952     * and each partial completion should be handled separately.
1953     * Reset per-request error on each partial completion.
1954     *
1955     * TODO: tj: This is too subtle. It would be better to let
1956     * low level drivers do what they see fit.
1957     */
1958    if (blk_fs_request(req))
1959        req->errors = 0;
1960
1961    if (error && (blk_fs_request(req) && !(req->cmd_flags & REQ_QUIET))) {
1962        printk(KERN_ERR "end_request: I/O error, dev %s, sector %llu\n",
1963                req->rq_disk ? req->rq_disk->disk_name : "?",
1964                (unsigned long long)blk_rq_pos(req));
1965    }
1966
1967    blk_account_io_completion(req, nr_bytes);
1968
1969    total_bytes = bio_nbytes = 0;
1970    while ((bio = req->bio) != NULL) {
1971        int nbytes;
1972
1973        if (nr_bytes >= bio->bi_size) {
1974            req->bio = bio->bi_next;
1975            nbytes = bio->bi_size;
1976            req_bio_endio(req, bio, nbytes, error);
1977            next_idx = 0;
1978            bio_nbytes = 0;
1979        } else {
1980            int idx = bio->bi_idx + next_idx;
1981
1982            if (unlikely(idx >= bio->bi_vcnt)) {
1983                blk_dump_rq_flags(req, "__end_that");
1984                printk(KERN_ERR "%s: bio idx %d >= vcnt %d\n",
1985                       __func__, idx, bio->bi_vcnt);
1986                break;
1987            }
1988
1989            nbytes = bio_iovec_idx(bio, idx)->bv_len;
1990            BIO_BUG_ON(nbytes > bio->bi_size);
1991
1992            /*
1993             * not a complete bvec done
1994             */
1995            if (unlikely(nbytes > nr_bytes)) {
1996                bio_nbytes += nr_bytes;
1997                total_bytes += nr_bytes;
1998                break;
1999            }
2000
2001            /*
2002             * advance to the next vector
2003             */
2004            next_idx++;
2005            bio_nbytes += nbytes;
2006        }
2007
2008        total_bytes += nbytes;
2009        nr_bytes -= nbytes;
2010
2011        bio = req->bio;
2012        if (bio) {
2013            /*
2014             * end more in this run, or just return 'not-done'
2015             */
2016            if (unlikely(nr_bytes <= 0))
2017                break;
2018        }
2019    }
2020
2021    /*
2022     * completely done
2023     */
2024    if (!req->bio) {
2025        /*
2026         * Reset counters so that the request stacking driver
2027         * can find how many bytes remain in the request
2028         * later.
2029         */
2030        req->__data_len = 0;
2031        return false;
2032    }
2033
2034    /*
2035     * if the request wasn't completed, update state
2036     */
2037    if (bio_nbytes) {
2038        req_bio_endio(req, bio, bio_nbytes, error);
2039        bio->bi_idx += next_idx;
2040        bio_iovec(bio)->bv_offset += nr_bytes;
2041        bio_iovec(bio)->bv_len -= nr_bytes;
2042    }
2043
2044    req->__data_len -= total_bytes;
2045    req->buffer = bio_data(req->bio);
2046
2047    /* update sector only for requests with clear definition of sector */
2048    if (blk_fs_request(req) || blk_discard_rq(req))
2049        req->__sector += total_bytes >> 9;
2050
2051    /* mixed attributes always follow the first bio */
2052    if (req->cmd_flags & REQ_MIXED_MERGE) {
2053        req->cmd_flags &= ~REQ_FAILFAST_MASK;
2054        req->cmd_flags |= req->bio->bi_rw & REQ_FAILFAST_MASK;
2055    }
2056
2057    /*
2058     * If total number of sectors is less than the first segment
2059     * size, something has gone terribly wrong.
2060     */
2061    if (blk_rq_bytes(req) < blk_rq_cur_bytes(req)) {
2062        printk(KERN_ERR "blk: request botched\n");
2063        req->__data_len = blk_rq_cur_bytes(req);
2064    }
2065
2066    /* recalculate the number of segments */
2067    blk_recalc_rq_segments(req);
2068
2069    return true;
2070}
2071EXPORT_SYMBOL_GPL(blk_update_request);
2072
2073static bool blk_update_bidi_request(struct request *rq, int error,
2074                    unsigned int nr_bytes,
2075                    unsigned int bidi_bytes)
2076{
2077    if (blk_update_request(rq, error, nr_bytes))
2078        return true;
2079
2080    /* Bidi request must be completed as a whole */
2081    if (unlikely(blk_bidi_rq(rq)) &&
2082        blk_update_request(rq->next_rq, error, bidi_bytes))
2083        return true;
2084
2085    add_disk_randomness(rq->rq_disk);
2086
2087    return false;
2088}
2089
2090/*
2091 * queue lock must be held
2092 */
2093static void blk_finish_request(struct request *req, int error)
2094{
2095    if (blk_rq_tagged(req))
2096        blk_queue_end_tag(req->q, req);
2097
2098    BUG_ON(blk_queued_rq(req));
2099
2100    if (unlikely(laptop_mode) && blk_fs_request(req))
2101        laptop_io_completion();
2102
2103    blk_delete_timer(req);
2104
2105    blk_account_io_done(req);
2106
2107    if (req->end_io)
2108        req->end_io(req, error);
2109    else {
2110        if (blk_bidi_rq(req))
2111            __blk_put_request(req->next_rq->q, req->next_rq);
2112
2113        __blk_put_request(req->q, req);
2114    }
2115}
2116
2117/**
2118 * blk_end_bidi_request - Complete a bidi request
2119 * @rq: the request to complete
2120 * @error: %0 for success, < %0 for error
2121 * @nr_bytes: number of bytes to complete @rq
2122 * @bidi_bytes: number of bytes to complete @rq->next_rq
2123 *
2124 * Description:
2125 * Ends I/O on a number of bytes attached to @rq and @rq->next_rq.
2126 * Drivers that supports bidi can safely call this member for any
2127 * type of request, bidi or uni. In the later case @bidi_bytes is
2128 * just ignored.
2129 *
2130 * Return:
2131 * %false - we are done with this request
2132 * %true - still buffers pending for this request
2133 **/
2134static bool blk_end_bidi_request(struct request *rq, int error,
2135                 unsigned int nr_bytes, unsigned int bidi_bytes)
2136{
2137    struct request_queue *q = rq->q;
2138    unsigned long flags;
2139
2140    if (blk_update_bidi_request(rq, error, nr_bytes, bidi_bytes))
2141        return true;
2142
2143    spin_lock_irqsave(q->queue_lock, flags);
2144    blk_finish_request(rq, error);
2145    spin_unlock_irqrestore(q->queue_lock, flags);
2146
2147    return false;
2148}
2149
2150/**
2151 * __blk_end_bidi_request - Complete a bidi request with queue lock held
2152 * @rq: the request to complete
2153 * @error: %0 for success, < %0 for error
2154 * @nr_bytes: number of bytes to complete @rq
2155 * @bidi_bytes: number of bytes to complete @rq->next_rq
2156 *
2157 * Description:
2158 * Identical to blk_end_bidi_request() except that queue lock is
2159 * assumed to be locked on entry and remains so on return.
2160 *
2161 * Return:
2162 * %false - we are done with this request
2163 * %true - still buffers pending for this request
2164 **/
2165static bool __blk_end_bidi_request(struct request *rq, int error,
2166                   unsigned int nr_bytes, unsigned int bidi_bytes)
2167{
2168    if (blk_update_bidi_request(rq, error, nr_bytes, bidi_bytes))
2169        return true;
2170
2171    blk_finish_request(rq, error);
2172
2173    return false;
2174}
2175
2176/**
2177 * blk_end_request - Helper function for drivers to complete the request.
2178 * @rq: the request being processed
2179 * @error: %0 for success, < %0 for error
2180 * @nr_bytes: number of bytes to complete
2181 *
2182 * Description:
2183 * Ends I/O on a number of bytes attached to @rq.
2184 * If @rq has leftover, sets it up for the next range of segments.
2185 *
2186 * Return:
2187 * %false - we are done with this request
2188 * %true - still buffers pending for this request
2189 **/
2190bool blk_end_request(struct request *rq, int error, unsigned int nr_bytes)
2191{
2192    return blk_end_bidi_request(rq, error, nr_bytes, 0);
2193}
2194EXPORT_SYMBOL(blk_end_request);
2195
2196/**
2197 * blk_end_request_all - Helper function for drives to finish the request.
2198 * @rq: the request to finish
2199 * @error: %0 for success, < %0 for error
2200 *
2201 * Description:
2202 * Completely finish @rq.
2203 */
2204void blk_end_request_all(struct request *rq, int error)
2205{
2206    bool pending;
2207    unsigned int bidi_bytes = 0;
2208
2209    if (unlikely(blk_bidi_rq(rq)))
2210        bidi_bytes = blk_rq_bytes(rq->next_rq);
2211
2212    pending = blk_end_bidi_request(rq, error, blk_rq_bytes(rq), bidi_bytes);
2213    BUG_ON(pending);
2214}
2215EXPORT_SYMBOL(blk_end_request_all);
2216
2217/**
2218 * blk_end_request_cur - Helper function to finish the current request chunk.
2219 * @rq: the request to finish the current chunk for
2220 * @error: %0 for success, < %0 for error
2221 *
2222 * Description:
2223 * Complete the current consecutively mapped chunk from @rq.
2224 *
2225 * Return:
2226 * %false - we are done with this request
2227 * %true - still buffers pending for this request
2228 */
2229bool blk_end_request_cur(struct request *rq, int error)
2230{
2231    return blk_end_request(rq, error, blk_rq_cur_bytes(rq));
2232}
2233EXPORT_SYMBOL(blk_end_request_cur);
2234
2235/**
2236 * blk_end_request_err - Finish a request till the next failure boundary.
2237 * @rq: the request to finish till the next failure boundary for
2238 * @error: must be negative errno
2239 *
2240 * Description:
2241 * Complete @rq till the next failure boundary.
2242 *
2243 * Return:
2244 * %false - we are done with this request
2245 * %true - still buffers pending for this request
2246 */
2247bool blk_end_request_err(struct request *rq, int error)
2248{
2249    WARN_ON(error >= 0);
2250    return blk_end_request(rq, error, blk_rq_err_bytes(rq));
2251}
2252EXPORT_SYMBOL_GPL(blk_end_request_err);
2253
2254/**
2255 * __blk_end_request - Helper function for drivers to complete the request.
2256 * @rq: the request being processed
2257 * @error: %0 for success, < %0 for error
2258 * @nr_bytes: number of bytes to complete
2259 *
2260 * Description:
2261 * Must be called with queue lock held unlike blk_end_request().
2262 *
2263 * Return:
2264 * %false - we are done with this request
2265 * %true - still buffers pending for this request
2266 **/
2267bool __blk_end_request(struct request *rq, int error, unsigned int nr_bytes)
2268{
2269    return __blk_end_bidi_request(rq, error, nr_bytes, 0);
2270}
2271EXPORT_SYMBOL(__blk_end_request);
2272
2273/**
2274 * __blk_end_request_all - Helper function for drives to finish the request.
2275 * @rq: the request to finish
2276 * @error: %0 for success, < %0 for error
2277 *
2278 * Description:
2279 * Completely finish @rq. Must be called with queue lock held.
2280 */
2281void __blk_end_request_all(struct request *rq, int error)
2282{
2283    bool pending;
2284    unsigned int bidi_bytes = 0;
2285
2286    if (unlikely(blk_bidi_rq(rq)))
2287        bidi_bytes = blk_rq_bytes(rq->next_rq);
2288
2289    pending = __blk_end_bidi_request(rq, error, blk_rq_bytes(rq), bidi_bytes);
2290    BUG_ON(pending);
2291}
2292EXPORT_SYMBOL(__blk_end_request_all);
2293
2294/**
2295 * __blk_end_request_cur - Helper function to finish the current request chunk.
2296 * @rq: the request to finish the current chunk for
2297 * @error: %0 for success, < %0 for error
2298 *
2299 * Description:
2300 * Complete the current consecutively mapped chunk from @rq. Must
2301 * be called with queue lock held.
2302 *
2303 * Return:
2304 * %false - we are done with this request
2305 * %true - still buffers pending for this request
2306 */
2307bool __blk_end_request_cur(struct request *rq, int error)
2308{
2309    return __blk_end_request(rq, error, blk_rq_cur_bytes(rq));
2310}
2311EXPORT_SYMBOL(__blk_end_request_cur);
2312
2313/**
2314 * __blk_end_request_err - Finish a request till the next failure boundary.
2315 * @rq: the request to finish till the next failure boundary for
2316 * @error: must be negative errno
2317 *
2318 * Description:
2319 * Complete @rq till the next failure boundary. Must be called
2320 * with queue lock held.
2321 *
2322 * Return:
2323 * %false - we are done with this request
2324 * %true - still buffers pending for this request
2325 */
2326bool __blk_end_request_err(struct request *rq, int error)
2327{
2328    WARN_ON(error >= 0);
2329    return __blk_end_request(rq, error, blk_rq_err_bytes(rq));
2330}
2331EXPORT_SYMBOL_GPL(__blk_end_request_err);
2332
2333void blk_rq_bio_prep(struct request_queue *q, struct request *rq,
2334             struct bio *bio)
2335{
2336    /* Bit 0 (R/W) is identical in rq->cmd_flags and bio->bi_rw */
2337    rq->cmd_flags |= bio->bi_rw & REQ_RW;
2338
2339    if (bio_has_data(bio)) {
2340        rq->nr_phys_segments = bio_phys_segments(q, bio);
2341        rq->buffer = bio_data(bio);
2342    }
2343    rq->__data_len = bio->bi_size;
2344    rq->bio = rq->biotail = bio;
2345
2346    if (bio->bi_bdev)
2347        rq->rq_disk = bio->bi_bdev->bd_disk;
2348}
2349
2350#if ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE
2351/**
2352 * rq_flush_dcache_pages - Helper function to flush all pages in a request
2353 * @rq: the request to be flushed
2354 *
2355 * Description:
2356 * Flush all pages in @rq.
2357 */
2358void rq_flush_dcache_pages(struct request *rq)
2359{
2360    struct req_iterator iter;
2361    struct bio_vec *bvec;
2362
2363    rq_for_each_segment(bvec, rq, iter)
2364        flush_dcache_page(bvec->bv_page);
2365}
2366EXPORT_SYMBOL_GPL(rq_flush_dcache_pages);
2367#endif
2368
2369/**
2370 * blk_lld_busy - Check if underlying low-level drivers of a device are busy
2371 * @q : the queue of the device being checked
2372 *
2373 * Description:
2374 * Check if underlying low-level drivers of a device are busy.
2375 * If the drivers want to export their busy state, they must set own
2376 * exporting function using blk_queue_lld_busy() first.
2377 *
2378 * Basically, this function is used only by request stacking drivers
2379 * to stop dispatching requests to underlying devices when underlying
2380 * devices are busy. This behavior helps more I/O merging on the queue
2381 * of the request stacking driver and prevents I/O throughput regression
2382 * on burst I/O load.
2383 *
2384 * Return:
2385 * 0 - Not busy (The request stacking driver should dispatch request)
2386 * 1 - Busy (The request stacking driver should stop dispatching request)
2387 */
2388int blk_lld_busy(struct request_queue *q)
2389{
2390    if (q->lld_busy_fn)
2391        return q->lld_busy_fn(q);
2392
2393    return 0;
2394}
2395EXPORT_SYMBOL_GPL(blk_lld_busy);
2396
2397/**
2398 * blk_rq_unprep_clone - Helper function to free all bios in a cloned request
2399 * @rq: the clone request to be cleaned up
2400 *
2401 * Description:
2402 * Free all bios in @rq for a cloned request.
2403 */
2404void blk_rq_unprep_clone(struct request *rq)
2405{
2406    struct bio *bio;
2407
2408    while ((bio = rq->bio) != NULL) {
2409        rq->bio = bio->bi_next;
2410
2411        bio_put(bio);
2412    }
2413}
2414EXPORT_SYMBOL_GPL(blk_rq_unprep_clone);
2415
2416/*
2417 * Copy attributes of the original request to the clone request.
2418 * The actual data parts (e.g. ->cmd, ->buffer, ->sense) are not copied.
2419 */
2420static void __blk_rq_prep_clone(struct request *dst, struct request *src)
2421{
2422    dst->cpu = src->cpu;
2423    dst->cmd_flags = (rq_data_dir(src) | REQ_NOMERGE);
2424    dst->cmd_type = src->cmd_type;
2425    dst->__sector = blk_rq_pos(src);
2426    dst->__data_len = blk_rq_bytes(src);
2427    dst->nr_phys_segments = src->nr_phys_segments;
2428    dst->ioprio = src->ioprio;
2429    dst->extra_len = src->extra_len;
2430}
2431
2432/**
2433 * blk_rq_prep_clone - Helper function to setup clone request
2434 * @rq: the request to be setup
2435 * @rq_src: original request to be cloned
2436 * @bs: bio_set that bios for clone are allocated from
2437 * @gfp_mask: memory allocation mask for bio
2438 * @bio_ctr: setup function to be called for each clone bio.
2439 * Returns %0 for success, non %0 for failure.
2440 * @data: private data to be passed to @bio_ctr
2441 *
2442 * Description:
2443 * Clones bios in @rq_src to @rq, and copies attributes of @rq_src to @rq.
2444 * The actual data parts of @rq_src (e.g. ->cmd, ->buffer, ->sense)
2445 * are not copied, and copying such parts is the caller's responsibility.
2446 * Also, pages which the original bios are pointing to are not copied
2447 * and the cloned bios just point same pages.
2448 * So cloned bios must be completed before original bios, which means
2449 * the caller must complete @rq before @rq_src.
2450 */
2451int blk_rq_prep_clone(struct request *rq, struct request *rq_src,
2452              struct bio_set *bs, gfp_t gfp_mask,
2453              int (*bio_ctr)(struct bio *, struct bio *, void *),
2454              void *data)
2455{
2456    struct bio *bio, *bio_src;
2457
2458    if (!bs)
2459        bs = fs_bio_set;
2460
2461    blk_rq_init(NULL, rq);
2462
2463    __rq_for_each_bio(bio_src, rq_src) {
2464        bio = bio_alloc_bioset(gfp_mask, bio_src->bi_max_vecs, bs);
2465        if (!bio)
2466            goto free_and_out;
2467
2468        __bio_clone(bio, bio_src);
2469
2470        if (bio_integrity(bio_src) &&
2471            bio_integrity_clone(bio, bio_src, gfp_mask, bs))
2472            goto free_and_out;
2473
2474        if (bio_ctr && bio_ctr(bio, bio_src, data))
2475            goto free_and_out;
2476
2477        if (rq->bio) {
2478            rq->biotail->bi_next = bio;
2479            rq->biotail = bio;
2480        } else
2481            rq->bio = rq->biotail = bio;
2482    }
2483
2484    __blk_rq_prep_clone(rq, rq_src);
2485
2486    return 0;
2487
2488free_and_out:
2489    if (bio)
2490        bio_free(bio, bs);
2491    blk_rq_unprep_clone(rq);
2492
2493    return -ENOMEM;
2494}
2495EXPORT_SYMBOL_GPL(blk_rq_prep_clone);
2496
2497int kblockd_schedule_work(struct request_queue *q, struct work_struct *work)
2498{
2499    return queue_work(kblockd_workqueue, work);
2500}
2501EXPORT_SYMBOL(kblockd_schedule_work);
2502
2503int __init blk_dev_init(void)
2504{
2505    BUILD_BUG_ON(__REQ_NR_BITS > 8 *
2506            sizeof(((struct request *)0)->cmd_flags));
2507
2508    kblockd_workqueue = create_workqueue("kblockd");
2509    if (!kblockd_workqueue)
2510        panic("Failed to create kblockd\n");
2511
2512    request_cachep = kmem_cache_create("blkdev_requests",
2513            sizeof(struct request), 0, SLAB_PANIC, NULL);
2514
2515    blk_requestq_cachep = kmem_cache_create("blkdev_queue",
2516            sizeof(struct request_queue), 0, SLAB_PANIC, NULL);
2517
2518    return 0;
2519}
2520
2521

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