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_queuing(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,tail} to keep a list of requests
1494 * submited by a make_request_fn function.
1495 * current->bio_tail 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    if (current->bio_tail) {
1504        /* make_request is active */
1505        *(current->bio_tail) = bio;
1506        bio->bi_next = NULL;
1507        current->bio_tail = &bio->bi_next;
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 the next (which is NULL) and bio_tail
1516     * to &bio_list, 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 fixup bio_list and
1522     * bio_tail or bi_next, 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    do {
1530        current->bio_list = bio->bi_next;
1531        if (bio->bi_next == NULL)
1532            current->bio_tail = &current->bio_list;
1533        else
1534            bio->bi_next = NULL;
1535        __generic_make_request(bio);
1536        bio = current->bio_list;
1537    } while (bio);
1538    current->bio_tail = NULL; /* deactivate */
1539}
1540EXPORT_SYMBOL(generic_make_request);
1541
1542/**
1543 * submit_bio - submit a bio to the block device layer for I/O
1544 * @rw: whether to %READ or %WRITE, or maybe to %READA (read ahead)
1545 * @bio: The &struct bio which describes the I/O
1546 *
1547 * submit_bio() is very similar in purpose to generic_make_request(), and
1548 * uses that function to do most of the work. Both are fairly rough
1549 * interfaces; @bio must be presetup and ready for I/O.
1550 *
1551 */
1552void submit_bio(int rw, struct bio *bio)
1553{
1554    int count = bio_sectors(bio);
1555
1556    bio->bi_rw |= rw;
1557
1558    /*
1559     * If it's a regular read/write or a barrier with data attached,
1560     * go through the normal accounting stuff before submission.
1561     */
1562    if (bio_has_data(bio)) {
1563        if (rw & WRITE) {
1564            count_vm_events(PGPGOUT, count);
1565        } else {
1566            task_io_account_read(bio->bi_size);
1567            count_vm_events(PGPGIN, count);
1568        }
1569
1570        if (unlikely(block_dump)) {
1571            char b[BDEVNAME_SIZE];
1572            printk(KERN_DEBUG "%s(%d): %s block %Lu on %s\n",
1573            current->comm, task_pid_nr(current),
1574                (rw & WRITE) ? "WRITE" : "READ",
1575                (unsigned long long)bio->bi_sector,
1576                bdevname(bio->bi_bdev, b));
1577        }
1578    }
1579
1580    generic_make_request(bio);
1581}
1582EXPORT_SYMBOL(submit_bio);
1583
1584/**
1585 * blk_rq_check_limits - Helper function to check a request for the queue limit
1586 * @q: the queue
1587 * @rq: the request being checked
1588 *
1589 * Description:
1590 * @rq may have been made based on weaker limitations of upper-level queues
1591 * in request stacking drivers, and it may violate the limitation of @q.
1592 * Since the block layer and the underlying device driver trust @rq
1593 * after it is inserted to @q, it should be checked against @q before
1594 * the insertion using this generic function.
1595 *
1596 * This function should also be useful for request stacking drivers
1597 * in some cases below, so export this fuction.
1598 * Request stacking drivers like request-based dm may change the queue
1599 * limits while requests are in the queue (e.g. dm's table swapping).
1600 * Such request stacking drivers should check those requests agaist
1601 * the new queue limits again when they dispatch those requests,
1602 * although such checkings are also done against the old queue limits
1603 * when submitting requests.
1604 */
1605int blk_rq_check_limits(struct request_queue *q, struct request *rq)
1606{
1607    if (blk_rq_sectors(rq) > queue_max_sectors(q) ||
1608        blk_rq_bytes(rq) > queue_max_hw_sectors(q) << 9) {
1609        printk(KERN_ERR "%s: over max size limit.\n", __func__);
1610        return -EIO;
1611    }
1612
1613    /*
1614     * queue's settings related to segment counting like q->bounce_pfn
1615     * may differ from that of other stacking queues.
1616     * Recalculate it to check the request correctly on this queue's
1617     * limitation.
1618     */
1619    blk_recalc_rq_segments(rq);
1620    if (rq->nr_phys_segments > queue_max_phys_segments(q) ||
1621        rq->nr_phys_segments > queue_max_hw_segments(q)) {
1622        printk(KERN_ERR "%s: over max segments limit.\n", __func__);
1623        return -EIO;
1624    }
1625
1626    return 0;
1627}
1628EXPORT_SYMBOL_GPL(blk_rq_check_limits);
1629
1630/**
1631 * blk_insert_cloned_request - Helper for stacking drivers to submit a request
1632 * @q: the queue to submit the request
1633 * @rq: the request being queued
1634 */
1635int blk_insert_cloned_request(struct request_queue *q, struct request *rq)
1636{
1637    unsigned long flags;
1638
1639    if (blk_rq_check_limits(q, rq))
1640        return -EIO;
1641
1642#ifdef CONFIG_FAIL_MAKE_REQUEST
1643    if (rq->rq_disk && rq->rq_disk->part0.make_it_fail &&
1644        should_fail(&fail_make_request, blk_rq_bytes(rq)))
1645        return -EIO;
1646#endif
1647
1648    spin_lock_irqsave(q->queue_lock, flags);
1649
1650    /*
1651     * Submitting request must be dequeued before calling this function
1652     * because it will be linked to another request_queue
1653     */
1654    BUG_ON(blk_queued_rq(rq));
1655
1656    drive_stat_acct(rq, 1);
1657    __elv_add_request(q, rq, ELEVATOR_INSERT_BACK, 0);
1658
1659    spin_unlock_irqrestore(q->queue_lock, flags);
1660
1661    return 0;
1662}
1663EXPORT_SYMBOL_GPL(blk_insert_cloned_request);
1664
1665/**
1666 * blk_rq_err_bytes - determine number of bytes till the next failure boundary
1667 * @rq: request to examine
1668 *
1669 * Description:
1670 * A request could be merge of IOs which require different failure
1671 * handling. This function determines the number of bytes which
1672 * can be failed from the beginning of the request without
1673 * crossing into area which need to be retried further.
1674 *
1675 * Return:
1676 * The number of bytes to fail.
1677 *
1678 * Context:
1679 * queue_lock must be held.
1680 */
1681unsigned int blk_rq_err_bytes(const struct request *rq)
1682{
1683    unsigned int ff = rq->cmd_flags & REQ_FAILFAST_MASK;
1684    unsigned int bytes = 0;
1685    struct bio *bio;
1686
1687    if (!(rq->cmd_flags & REQ_MIXED_MERGE))
1688        return blk_rq_bytes(rq);
1689
1690    /*
1691     * Currently the only 'mixing' which can happen is between
1692     * different fastfail types. We can safely fail portions
1693     * which have all the failfast bits that the first one has -
1694     * the ones which are at least as eager to fail as the first
1695     * one.
1696     */
1697    for (bio = rq->bio; bio; bio = bio->bi_next) {
1698        if ((bio->bi_rw & ff) != ff)
1699            break;
1700        bytes += bio->bi_size;
1701    }
1702
1703    /* this could lead to infinite loop */
1704    BUG_ON(blk_rq_bytes(rq) && !bytes);
1705    return bytes;
1706}
1707EXPORT_SYMBOL_GPL(blk_rq_err_bytes);
1708
1709static void blk_account_io_completion(struct request *req, unsigned int bytes)
1710{
1711    if (blk_do_io_stat(req)) {
1712        const int rw = rq_data_dir(req);
1713        struct hd_struct *part;
1714        int cpu;
1715
1716        cpu = part_stat_lock();
1717        part = disk_map_sector_rcu(req->rq_disk, blk_rq_pos(req));
1718        part_stat_add(cpu, part, sectors[rw], bytes >> 9);
1719        part_stat_unlock();
1720    }
1721}
1722
1723static void blk_account_io_done(struct request *req)
1724{
1725    /*
1726     * Account IO completion. bar_rq isn't accounted as a normal
1727     * IO on queueing nor completion. Accounting the containing
1728     * request is enough.
1729     */
1730    if (blk_do_io_stat(req) && req != &req->q->bar_rq) {
1731        unsigned long duration = jiffies - req->start_time;
1732        const int rw = rq_data_dir(req);
1733        struct hd_struct *part;
1734        int cpu;
1735
1736        cpu = part_stat_lock();
1737        part = disk_map_sector_rcu(req->rq_disk, blk_rq_pos(req));
1738
1739        part_stat_inc(cpu, part, ios[rw]);
1740        part_stat_add(cpu, part, ticks[rw], duration);
1741        part_round_stats(cpu, part);
1742        part_dec_in_flight(part, rw);
1743
1744        part_stat_unlock();
1745    }
1746}
1747
1748/**
1749 * blk_peek_request - peek at the top of a request queue
1750 * @q: request queue to peek at
1751 *
1752 * Description:
1753 * Return the request at the top of @q. The returned request
1754 * should be started using blk_start_request() before LLD starts
1755 * processing it.
1756 *
1757 * Return:
1758 * Pointer to the request at the top of @q if available. Null
1759 * otherwise.
1760 *
1761 * Context:
1762 * queue_lock must be held.
1763 */
1764struct request *blk_peek_request(struct request_queue *q)
1765{
1766    struct request *rq;
1767    int ret;
1768
1769    while ((rq = __elv_next_request(q)) != NULL) {
1770        if (!(rq->cmd_flags & REQ_STARTED)) {
1771            /*
1772             * This is the first time the device driver
1773             * sees this request (possibly after
1774             * requeueing). Notify IO scheduler.
1775             */
1776            if (blk_sorted_rq(rq))
1777                elv_activate_rq(q, rq);
1778
1779            /*
1780             * just mark as started even if we don't start
1781             * it, a request that has been delayed should
1782             * not be passed by new incoming requests
1783             */
1784            rq->cmd_flags |= REQ_STARTED;
1785            trace_block_rq_issue(q, rq);
1786        }
1787
1788        if (!q->boundary_rq || q->boundary_rq == rq) {
1789            q->end_sector = rq_end_sector(rq);
1790            q->boundary_rq = NULL;
1791        }
1792
1793        if (rq->cmd_flags & REQ_DONTPREP)
1794            break;
1795
1796        if (q->dma_drain_size && blk_rq_bytes(rq)) {
1797            /*
1798             * make sure space for the drain appears we
1799             * know we can do this because max_hw_segments
1800             * has been adjusted to be one fewer than the
1801             * device can handle
1802             */
1803            rq->nr_phys_segments++;
1804        }
1805
1806        if (!q->prep_rq_fn)
1807            break;
1808
1809        ret = q->prep_rq_fn(q, rq);
1810        if (ret == BLKPREP_OK) {
1811            break;
1812        } else if (ret == BLKPREP_DEFER) {
1813            /*
1814             * the request may have been (partially) prepped.
1815             * we need to keep this request in the front to
1816             * avoid resource deadlock. REQ_STARTED will
1817             * prevent other fs requests from passing this one.
1818             */
1819            if (q->dma_drain_size && blk_rq_bytes(rq) &&
1820                !(rq->cmd_flags & REQ_DONTPREP)) {
1821                /*
1822                 * remove the space for the drain we added
1823                 * so that we don't add it again
1824                 */
1825                --rq->nr_phys_segments;
1826            }
1827
1828            rq = NULL;
1829            break;
1830        } else if (ret == BLKPREP_KILL) {
1831            rq->cmd_flags |= REQ_QUIET;
1832            /*
1833             * Mark this request as started so we don't trigger
1834             * any debug logic in the end I/O path.
1835             */
1836            blk_start_request(rq);
1837            __blk_end_request_all(rq, -EIO);
1838        } else {
1839            printk(KERN_ERR "%s: bad return=%d\n", __func__, ret);
1840            break;
1841        }
1842    }
1843
1844    return rq;
1845}
1846EXPORT_SYMBOL(blk_peek_request);
1847
1848void blk_dequeue_request(struct request *rq)
1849{
1850    struct request_queue *q = rq->q;
1851
1852    BUG_ON(list_empty(&rq->queuelist));
1853    BUG_ON(ELV_ON_HASH(rq));
1854
1855    list_del_init(&rq->queuelist);
1856
1857    /*
1858     * the time frame between a request being removed from the lists
1859     * and to it is freed is accounted as io that is in progress at
1860     * the driver side.
1861     */
1862    if (blk_account_rq(rq)) {
1863        q->in_flight[rq_is_sync(rq)]++;
1864        /*
1865         * Mark this device as supporting hardware queuing, if
1866         * we have more IOs in flight than 4.
1867         */
1868        if (!blk_queue_queuing(q) && queue_in_flight(q) > 4)
1869            set_bit(QUEUE_FLAG_CQ, &q->queue_flags);
1870    }
1871}
1872
1873/**
1874 * blk_start_request - start request processing on the driver
1875 * @req: request to dequeue
1876 *
1877 * Description:
1878 * Dequeue @req and start timeout timer on it. This hands off the
1879 * request to the driver.
1880 *
1881 * Block internal functions which don't want to start timer should
1882 * call blk_dequeue_request().
1883 *
1884 * Context:
1885 * queue_lock must be held.
1886 */
1887void blk_start_request(struct request *req)
1888{
1889    blk_dequeue_request(req);
1890
1891    /*
1892     * We are now handing the request to the hardware, initialize
1893     * resid_len to full count and add the timeout handler.
1894     */
1895    req->resid_len = blk_rq_bytes(req);
1896    if (unlikely(blk_bidi_rq(req)))
1897        req->next_rq->resid_len = blk_rq_bytes(req->next_rq);
1898
1899    blk_add_timer(req);
1900}
1901EXPORT_SYMBOL(blk_start_request);
1902
1903/**
1904 * blk_fetch_request - fetch a request from a request queue
1905 * @q: request queue to fetch a request from
1906 *
1907 * Description:
1908 * Return the request at the top of @q. The request is started on
1909 * return and LLD can start processing it immediately.
1910 *
1911 * Return:
1912 * Pointer to the request at the top of @q if available. Null
1913 * otherwise.
1914 *
1915 * Context:
1916 * queue_lock must be held.
1917 */
1918struct request *blk_fetch_request(struct request_queue *q)
1919{
1920    struct request *rq;
1921
1922    rq = blk_peek_request(q);
1923    if (rq)
1924        blk_start_request(rq);
1925    return rq;
1926}
1927EXPORT_SYMBOL(blk_fetch_request);
1928
1929/**
1930 * blk_update_request - Special helper function for request stacking drivers
1931 * @req: the request being processed
1932 * @error: %0 for success, < %0 for error
1933 * @nr_bytes: number of bytes to complete @req
1934 *
1935 * Description:
1936 * Ends I/O on a number of bytes attached to @req, but doesn't complete
1937 * the request structure even if @req doesn't have leftover.
1938 * If @req has leftover, sets it up for the next range of segments.
1939 *
1940 * This special helper function is only for request stacking drivers
1941 * (e.g. request-based dm) so that they can handle partial completion.
1942 * Actual device drivers should use blk_end_request instead.
1943 *
1944 * Passing the result of blk_rq_bytes() as @nr_bytes guarantees
1945 * %false return from this function.
1946 *
1947 * Return:
1948 * %false - this request doesn't have any more data
1949 * %true - this request has more data
1950 **/
1951bool blk_update_request(struct request *req, int error, unsigned int nr_bytes)
1952{
1953    int total_bytes, bio_nbytes, next_idx = 0;
1954    struct bio *bio;
1955
1956    if (!req->bio)
1957        return false;
1958
1959    trace_block_rq_complete(req->q, req);
1960
1961    /*
1962     * For fs requests, rq is just carrier of independent bio's
1963     * and each partial completion should be handled separately.
1964     * Reset per-request error on each partial completion.
1965     *
1966     * TODO: tj: This is too subtle. It would be better to let
1967     * low level drivers do what they see fit.
1968     */
1969    if (blk_fs_request(req))
1970        req->errors = 0;
1971
1972    if (error && (blk_fs_request(req) && !(req->cmd_flags & REQ_QUIET))) {
1973        printk(KERN_ERR "end_request: I/O error, dev %s, sector %llu\n",
1974                req->rq_disk ? req->rq_disk->disk_name : "?",
1975                (unsigned long long)blk_rq_pos(req));
1976    }
1977
1978    blk_account_io_completion(req, nr_bytes);
1979
1980    total_bytes = bio_nbytes = 0;
1981    while ((bio = req->bio) != NULL) {
1982        int nbytes;
1983
1984        if (nr_bytes >= bio->bi_size) {
1985            req->bio = bio->bi_next;
1986            nbytes = bio->bi_size;
1987            req_bio_endio(req, bio, nbytes, error);
1988            next_idx = 0;
1989            bio_nbytes = 0;
1990        } else {
1991            int idx = bio->bi_idx + next_idx;
1992
1993            if (unlikely(idx >= bio->bi_vcnt)) {
1994                blk_dump_rq_flags(req, "__end_that");
1995                printk(KERN_ERR "%s: bio idx %d >= vcnt %d\n",
1996                       __func__, idx, bio->bi_vcnt);
1997                break;
1998            }
1999
2000            nbytes = bio_iovec_idx(bio, idx)->bv_len;
2001            BIO_BUG_ON(nbytes > bio->bi_size);
2002
2003            /*
2004             * not a complete bvec done
2005             */
2006            if (unlikely(nbytes > nr_bytes)) {
2007                bio_nbytes += nr_bytes;
2008                total_bytes += nr_bytes;
2009                break;
2010            }
2011
2012            /*
2013             * advance to the next vector
2014             */
2015            next_idx++;
2016            bio_nbytes += nbytes;
2017        }
2018
2019        total_bytes += nbytes;
2020        nr_bytes -= nbytes;
2021
2022        bio = req->bio;
2023        if (bio) {
2024            /*
2025             * end more in this run, or just return 'not-done'
2026             */
2027            if (unlikely(nr_bytes <= 0))
2028                break;
2029        }
2030    }
2031
2032    /*
2033     * completely done
2034     */
2035    if (!req->bio) {
2036        /*
2037         * Reset counters so that the request stacking driver
2038         * can find how many bytes remain in the request
2039         * later.
2040         */
2041        req->__data_len = 0;
2042        return false;
2043    }
2044
2045    /*
2046     * if the request wasn't completed, update state
2047     */
2048    if (bio_nbytes) {
2049        req_bio_endio(req, bio, bio_nbytes, error);
2050        bio->bi_idx += next_idx;
2051        bio_iovec(bio)->bv_offset += nr_bytes;
2052        bio_iovec(bio)->bv_len -= nr_bytes;
2053    }
2054
2055    req->__data_len -= total_bytes;
2056    req->buffer = bio_data(req->bio);
2057
2058    /* update sector only for requests with clear definition of sector */
2059    if (blk_fs_request(req) || blk_discard_rq(req))
2060        req->__sector += total_bytes >> 9;
2061
2062    /* mixed attributes always follow the first bio */
2063    if (req->cmd_flags & REQ_MIXED_MERGE) {
2064        req->cmd_flags &= ~REQ_FAILFAST_MASK;
2065        req->cmd_flags |= req->bio->bi_rw & REQ_FAILFAST_MASK;
2066    }
2067
2068    /*
2069     * If total number of sectors is less than the first segment
2070     * size, something has gone terribly wrong.
2071     */
2072    if (blk_rq_bytes(req) < blk_rq_cur_bytes(req)) {
2073        printk(KERN_ERR "blk: request botched\n");
2074        req->__data_len = blk_rq_cur_bytes(req);
2075    }
2076
2077    /* recalculate the number of segments */
2078    blk_recalc_rq_segments(req);
2079
2080    return true;
2081}
2082EXPORT_SYMBOL_GPL(blk_update_request);
2083
2084static bool blk_update_bidi_request(struct request *rq, int error,
2085                    unsigned int nr_bytes,
2086                    unsigned int bidi_bytes)
2087{
2088    if (blk_update_request(rq, error, nr_bytes))
2089        return true;
2090
2091    /* Bidi request must be completed as a whole */
2092    if (unlikely(blk_bidi_rq(rq)) &&
2093        blk_update_request(rq->next_rq, error, bidi_bytes))
2094        return true;
2095
2096    add_disk_randomness(rq->rq_disk);
2097
2098    return false;
2099}
2100
2101/*
2102 * queue lock must be held
2103 */
2104static void blk_finish_request(struct request *req, int error)
2105{
2106    if (blk_rq_tagged(req))
2107        blk_queue_end_tag(req->q, req);
2108
2109    BUG_ON(blk_queued_rq(req));
2110
2111    if (unlikely(laptop_mode) && blk_fs_request(req))
2112        laptop_io_completion();
2113
2114    blk_delete_timer(req);
2115
2116    blk_account_io_done(req);
2117
2118    if (req->end_io)
2119        req->end_io(req, error);
2120    else {
2121        if (blk_bidi_rq(req))
2122            __blk_put_request(req->next_rq->q, req->next_rq);
2123
2124        __blk_put_request(req->q, req);
2125    }
2126}
2127
2128/**
2129 * blk_end_bidi_request - Complete a bidi request
2130 * @rq: the request to complete
2131 * @error: %0 for success, < %0 for error
2132 * @nr_bytes: number of bytes to complete @rq
2133 * @bidi_bytes: number of bytes to complete @rq->next_rq
2134 *
2135 * Description:
2136 * Ends I/O on a number of bytes attached to @rq and @rq->next_rq.
2137 * Drivers that supports bidi can safely call this member for any
2138 * type of request, bidi or uni. In the later case @bidi_bytes is
2139 * just ignored.
2140 *
2141 * Return:
2142 * %false - we are done with this request
2143 * %true - still buffers pending for this request
2144 **/
2145static bool blk_end_bidi_request(struct request *rq, int error,
2146                 unsigned int nr_bytes, unsigned int bidi_bytes)
2147{
2148    struct request_queue *q = rq->q;
2149    unsigned long flags;
2150
2151    if (blk_update_bidi_request(rq, error, nr_bytes, bidi_bytes))
2152        return true;
2153
2154    spin_lock_irqsave(q->queue_lock, flags);
2155    blk_finish_request(rq, error);
2156    spin_unlock_irqrestore(q->queue_lock, flags);
2157
2158    return false;
2159}
2160
2161/**
2162 * __blk_end_bidi_request - Complete a bidi request with queue lock held
2163 * @rq: the request to complete
2164 * @error: %0 for success, < %0 for error
2165 * @nr_bytes: number of bytes to complete @rq
2166 * @bidi_bytes: number of bytes to complete @rq->next_rq
2167 *
2168 * Description:
2169 * Identical to blk_end_bidi_request() except that queue lock is
2170 * assumed to be locked on entry and remains so on return.
2171 *
2172 * Return:
2173 * %false - we are done with this request
2174 * %true - still buffers pending for this request
2175 **/
2176static bool __blk_end_bidi_request(struct request *rq, int error,
2177                   unsigned int nr_bytes, unsigned int bidi_bytes)
2178{
2179    if (blk_update_bidi_request(rq, error, nr_bytes, bidi_bytes))
2180        return true;
2181
2182    blk_finish_request(rq, error);
2183
2184    return false;
2185}
2186
2187/**
2188 * blk_end_request - Helper function for drivers to complete the request.
2189 * @rq: the request being processed
2190 * @error: %0 for success, < %0 for error
2191 * @nr_bytes: number of bytes to complete
2192 *
2193 * Description:
2194 * Ends I/O on a number of bytes attached to @rq.
2195 * If @rq has leftover, sets it up for the next range of segments.
2196 *
2197 * Return:
2198 * %false - we are done with this request
2199 * %true - still buffers pending for this request
2200 **/
2201bool blk_end_request(struct request *rq, int error, unsigned int nr_bytes)
2202{
2203    return blk_end_bidi_request(rq, error, nr_bytes, 0);
2204}
2205EXPORT_SYMBOL(blk_end_request);
2206
2207/**
2208 * blk_end_request_all - Helper function for drives to finish the request.
2209 * @rq: the request to finish
2210 * @error: %0 for success, < %0 for error
2211 *
2212 * Description:
2213 * Completely finish @rq.
2214 */
2215void blk_end_request_all(struct request *rq, int error)
2216{
2217    bool pending;
2218    unsigned int bidi_bytes = 0;
2219
2220    if (unlikely(blk_bidi_rq(rq)))
2221        bidi_bytes = blk_rq_bytes(rq->next_rq);
2222
2223    pending = blk_end_bidi_request(rq, error, blk_rq_bytes(rq), bidi_bytes);
2224    BUG_ON(pending);
2225}
2226EXPORT_SYMBOL(blk_end_request_all);
2227
2228/**
2229 * blk_end_request_cur - Helper function to finish the current request chunk.
2230 * @rq: the request to finish the current chunk for
2231 * @error: %0 for success, < %0 for error
2232 *
2233 * Description:
2234 * Complete the current consecutively mapped chunk from @rq.
2235 *
2236 * Return:
2237 * %false - we are done with this request
2238 * %true - still buffers pending for this request
2239 */
2240bool blk_end_request_cur(struct request *rq, int error)
2241{
2242    return blk_end_request(rq, error, blk_rq_cur_bytes(rq));
2243}
2244EXPORT_SYMBOL(blk_end_request_cur);
2245
2246/**
2247 * blk_end_request_err - Finish a request till the next failure boundary.
2248 * @rq: the request to finish till the next failure boundary for
2249 * @error: must be negative errno
2250 *
2251 * Description:
2252 * Complete @rq till the next failure boundary.
2253 *
2254 * Return:
2255 * %false - we are done with this request
2256 * %true - still buffers pending for this request
2257 */
2258bool blk_end_request_err(struct request *rq, int error)
2259{
2260    WARN_ON(error >= 0);
2261    return blk_end_request(rq, error, blk_rq_err_bytes(rq));
2262}
2263EXPORT_SYMBOL_GPL(blk_end_request_err);
2264
2265/**
2266 * __blk_end_request - Helper function for drivers to complete the request.
2267 * @rq: the request being processed
2268 * @error: %0 for success, < %0 for error
2269 * @nr_bytes: number of bytes to complete
2270 *
2271 * Description:
2272 * Must be called with queue lock held unlike blk_end_request().
2273 *
2274 * Return:
2275 * %false - we are done with this request
2276 * %true - still buffers pending for this request
2277 **/
2278bool __blk_end_request(struct request *rq, int error, unsigned int nr_bytes)
2279{
2280    return __blk_end_bidi_request(rq, error, nr_bytes, 0);
2281}
2282EXPORT_SYMBOL(__blk_end_request);
2283
2284/**
2285 * __blk_end_request_all - Helper function for drives to finish the request.
2286 * @rq: the request to finish
2287 * @error: %0 for success, < %0 for error
2288 *
2289 * Description:
2290 * Completely finish @rq. Must be called with queue lock held.
2291 */
2292void __blk_end_request_all(struct request *rq, int error)
2293{
2294    bool pending;
2295    unsigned int bidi_bytes = 0;
2296
2297    if (unlikely(blk_bidi_rq(rq)))
2298        bidi_bytes = blk_rq_bytes(rq->next_rq);
2299
2300    pending = __blk_end_bidi_request(rq, error, blk_rq_bytes(rq), bidi_bytes);
2301    BUG_ON(pending);
2302}
2303EXPORT_SYMBOL(__blk_end_request_all);
2304
2305/**
2306 * __blk_end_request_cur - Helper function to finish the current request chunk.
2307 * @rq: the request to finish the current chunk for
2308 * @error: %0 for success, < %0 for error
2309 *
2310 * Description:
2311 * Complete the current consecutively mapped chunk from @rq. Must
2312 * be called with queue lock held.
2313 *
2314 * Return:
2315 * %false - we are done with this request
2316 * %true - still buffers pending for this request
2317 */
2318bool __blk_end_request_cur(struct request *rq, int error)
2319{
2320    return __blk_end_request(rq, error, blk_rq_cur_bytes(rq));
2321}
2322EXPORT_SYMBOL(__blk_end_request_cur);
2323
2324/**
2325 * __blk_end_request_err - Finish a request till the next failure boundary.
2326 * @rq: the request to finish till the next failure boundary for
2327 * @error: must be negative errno
2328 *
2329 * Description:
2330 * Complete @rq till the next failure boundary. Must be called
2331 * with queue lock held.
2332 *
2333 * Return:
2334 * %false - we are done with this request
2335 * %true - still buffers pending for this request
2336 */
2337bool __blk_end_request_err(struct request *rq, int error)
2338{
2339    WARN_ON(error >= 0);
2340    return __blk_end_request(rq, error, blk_rq_err_bytes(rq));
2341}
2342EXPORT_SYMBOL_GPL(__blk_end_request_err);
2343
2344void blk_rq_bio_prep(struct request_queue *q, struct request *rq,
2345             struct bio *bio)
2346{
2347    /* Bit 0 (R/W) is identical in rq->cmd_flags and bio->bi_rw */
2348    rq->cmd_flags |= bio->bi_rw & REQ_RW;
2349
2350    if (bio_has_data(bio)) {
2351        rq->nr_phys_segments = bio_phys_segments(q, bio);
2352        rq->buffer = bio_data(bio);
2353    }
2354    rq->__data_len = bio->bi_size;
2355    rq->bio = rq->biotail = bio;
2356
2357    if (bio->bi_bdev)
2358        rq->rq_disk = bio->bi_bdev->bd_disk;
2359}
2360
2361/**
2362 * blk_lld_busy - Check if underlying low-level drivers of a device are busy
2363 * @q : the queue of the device being checked
2364 *
2365 * Description:
2366 * Check if underlying low-level drivers of a device are busy.
2367 * If the drivers want to export their busy state, they must set own
2368 * exporting function using blk_queue_lld_busy() first.
2369 *
2370 * Basically, this function is used only by request stacking drivers
2371 * to stop dispatching requests to underlying devices when underlying
2372 * devices are busy. This behavior helps more I/O merging on the queue
2373 * of the request stacking driver and prevents I/O throughput regression
2374 * on burst I/O load.
2375 *
2376 * Return:
2377 * 0 - Not busy (The request stacking driver should dispatch request)
2378 * 1 - Busy (The request stacking driver should stop dispatching request)
2379 */
2380int blk_lld_busy(struct request_queue *q)
2381{
2382    if (q->lld_busy_fn)
2383        return q->lld_busy_fn(q);
2384
2385    return 0;
2386}
2387EXPORT_SYMBOL_GPL(blk_lld_busy);
2388
2389/**
2390 * blk_rq_unprep_clone - Helper function to free all bios in a cloned request
2391 * @rq: the clone request to be cleaned up
2392 *
2393 * Description:
2394 * Free all bios in @rq for a cloned request.
2395 */
2396void blk_rq_unprep_clone(struct request *rq)
2397{
2398    struct bio *bio;
2399
2400    while ((bio = rq->bio) != NULL) {
2401        rq->bio = bio->bi_next;
2402
2403        bio_put(bio);
2404    }
2405}
2406EXPORT_SYMBOL_GPL(blk_rq_unprep_clone);
2407
2408/*
2409 * Copy attributes of the original request to the clone request.
2410 * The actual data parts (e.g. ->cmd, ->buffer, ->sense) are not copied.
2411 */
2412static void __blk_rq_prep_clone(struct request *dst, struct request *src)
2413{
2414    dst->cpu = src->cpu;
2415    dst->cmd_flags = (rq_data_dir(src) | REQ_NOMERGE);
2416    dst->cmd_type = src->cmd_type;
2417    dst->__sector = blk_rq_pos(src);
2418    dst->__data_len = blk_rq_bytes(src);
2419    dst->nr_phys_segments = src->nr_phys_segments;
2420    dst->ioprio = src->ioprio;
2421    dst->extra_len = src->extra_len;
2422}
2423
2424/**
2425 * blk_rq_prep_clone - Helper function to setup clone request
2426 * @rq: the request to be setup
2427 * @rq_src: original request to be cloned
2428 * @bs: bio_set that bios for clone are allocated from
2429 * @gfp_mask: memory allocation mask for bio
2430 * @bio_ctr: setup function to be called for each clone bio.
2431 * Returns %0 for success, non %0 for failure.
2432 * @data: private data to be passed to @bio_ctr
2433 *
2434 * Description:
2435 * Clones bios in @rq_src to @rq, and copies attributes of @rq_src to @rq.
2436 * The actual data parts of @rq_src (e.g. ->cmd, ->buffer, ->sense)
2437 * are not copied, and copying such parts is the caller's responsibility.
2438 * Also, pages which the original bios are pointing to are not copied
2439 * and the cloned bios just point same pages.
2440 * So cloned bios must be completed before original bios, which means
2441 * the caller must complete @rq before @rq_src.
2442 */
2443int blk_rq_prep_clone(struct request *rq, struct request *rq_src,
2444              struct bio_set *bs, gfp_t gfp_mask,
2445              int (*bio_ctr)(struct bio *, struct bio *, void *),
2446              void *data)
2447{
2448    struct bio *bio, *bio_src;
2449
2450    if (!bs)
2451        bs = fs_bio_set;
2452
2453    blk_rq_init(NULL, rq);
2454
2455    __rq_for_each_bio(bio_src, rq_src) {
2456        bio = bio_alloc_bioset(gfp_mask, bio_src->bi_max_vecs, bs);
2457        if (!bio)
2458            goto free_and_out;
2459
2460        __bio_clone(bio, bio_src);
2461
2462        if (bio_integrity(bio_src) &&
2463            bio_integrity_clone(bio, bio_src, gfp_mask, bs))
2464            goto free_and_out;
2465
2466        if (bio_ctr && bio_ctr(bio, bio_src, data))
2467            goto free_and_out;
2468
2469        if (rq->bio) {
2470            rq->biotail->bi_next = bio;
2471            rq->biotail = bio;
2472        } else
2473            rq->bio = rq->biotail = bio;
2474    }
2475
2476    __blk_rq_prep_clone(rq, rq_src);
2477
2478    return 0;
2479
2480free_and_out:
2481    if (bio)
2482        bio_free(bio, bs);
2483    blk_rq_unprep_clone(rq);
2484
2485    return -ENOMEM;
2486}
2487EXPORT_SYMBOL_GPL(blk_rq_prep_clone);
2488
2489int kblockd_schedule_work(struct request_queue *q, struct work_struct *work)
2490{
2491    return queue_work(kblockd_workqueue, work);
2492}
2493EXPORT_SYMBOL(kblockd_schedule_work);
2494
2495int __init blk_dev_init(void)
2496{
2497    BUILD_BUG_ON(__REQ_NR_BITS > 8 *
2498            sizeof(((struct request *)0)->cmd_flags));
2499
2500    kblockd_workqueue = create_workqueue("kblockd");
2501    if (!kblockd_workqueue)
2502        panic("Failed to create kblockd\n");
2503
2504    request_cachep = kmem_cache_create("blkdev_requests",
2505            sizeof(struct request), 0, SLAB_PANIC, NULL);
2506
2507    blk_requestq_cachep = kmem_cache_create("blkdev_queue",
2508            sizeof(struct request_queue), 0, SLAB_PANIC, NULL);
2509
2510    return 0;
2511}
2512
2513

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