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    set_start_time_ns(rq);
131}
132EXPORT_SYMBOL(blk_rq_init);
133
134static void req_bio_endio(struct request *rq, struct bio *bio,
135              unsigned int nbytes, int error)
136{
137    struct request_queue *q = rq->q;
138
139    if (&q->bar_rq != rq) {
140        if (error)
141            clear_bit(BIO_UPTODATE, &bio->bi_flags);
142        else if (!test_bit(BIO_UPTODATE, &bio->bi_flags))
143            error = -EIO;
144
145        if (unlikely(nbytes > bio->bi_size)) {
146            printk(KERN_ERR "%s: want %u bytes done, %u left\n",
147                   __func__, nbytes, bio->bi_size);
148            nbytes = bio->bi_size;
149        }
150
151        if (unlikely(rq->cmd_flags & REQ_QUIET))
152            set_bit(BIO_QUIET, &bio->bi_flags);
153
154        bio->bi_size -= nbytes;
155        bio->bi_sector += (nbytes >> 9);
156
157        if (bio_integrity(bio))
158            bio_integrity_advance(bio, nbytes);
159
160        if (bio->bi_size == 0)
161            bio_endio(bio, error);
162    } else {
163
164        /*
165         * Okay, this is the barrier request in progress, just
166         * record the error;
167         */
168        if (error && !q->orderr)
169            q->orderr = error;
170    }
171}
172
173void blk_dump_rq_flags(struct request *rq, char *msg)
174{
175    int bit;
176
177    printk(KERN_INFO "%s: dev %s: type=%x, flags=%x\n", msg,
178        rq->rq_disk ? rq->rq_disk->disk_name : "?", rq->cmd_type,
179        rq->cmd_flags);
180
181    printk(KERN_INFO " sector %llu, nr/cnr %u/%u\n",
182           (unsigned long long)blk_rq_pos(rq),
183           blk_rq_sectors(rq), blk_rq_cur_sectors(rq));
184    printk(KERN_INFO " bio %p, biotail %p, buffer %p, len %u\n",
185           rq->bio, rq->biotail, rq->buffer, blk_rq_bytes(rq));
186
187    if (blk_pc_request(rq)) {
188        printk(KERN_INFO " cdb: ");
189        for (bit = 0; bit < BLK_MAX_CDB; bit++)
190            printk("%02x ", rq->cmd[bit]);
191        printk("\n");
192    }
193}
194EXPORT_SYMBOL(blk_dump_rq_flags);
195
196/*
197 * "plug" the device if there are no outstanding requests: this will
198 * force the transfer to start only after we have put all the requests
199 * on the list.
200 *
201 * This is called with interrupts off and no requests on the queue and
202 * with the queue lock held.
203 */
204void blk_plug_device(struct request_queue *q)
205{
206    WARN_ON(!irqs_disabled());
207
208    /*
209     * don't plug a stopped queue, it must be paired with blk_start_queue()
210     * which will restart the queueing
211     */
212    if (blk_queue_stopped(q))
213        return;
214
215    if (!queue_flag_test_and_set(QUEUE_FLAG_PLUGGED, q)) {
216        mod_timer(&q->unplug_timer, jiffies + q->unplug_delay);
217        trace_block_plug(q);
218    }
219}
220EXPORT_SYMBOL(blk_plug_device);
221
222/**
223 * blk_plug_device_unlocked - plug a device without queue lock held
224 * @q: The &struct request_queue to plug
225 *
226 * Description:
227 * Like @blk_plug_device(), but grabs the queue lock and disables
228 * interrupts.
229 **/
230void blk_plug_device_unlocked(struct request_queue *q)
231{
232    unsigned long flags;
233
234    spin_lock_irqsave(q->queue_lock, flags);
235    blk_plug_device(q);
236    spin_unlock_irqrestore(q->queue_lock, flags);
237}
238EXPORT_SYMBOL(blk_plug_device_unlocked);
239
240/*
241 * remove the queue from the plugged list, if present. called with
242 * queue lock held and interrupts disabled.
243 */
244int blk_remove_plug(struct request_queue *q)
245{
246    WARN_ON(!irqs_disabled());
247
248    if (!queue_flag_test_and_clear(QUEUE_FLAG_PLUGGED, q))
249        return 0;
250
251    del_timer(&q->unplug_timer);
252    return 1;
253}
254EXPORT_SYMBOL(blk_remove_plug);
255
256/*
257 * remove the plug and let it rip..
258 */
259void __generic_unplug_device(struct request_queue *q)
260{
261    if (unlikely(blk_queue_stopped(q)))
262        return;
263    if (!blk_remove_plug(q) && !blk_queue_nonrot(q))
264        return;
265
266    q->request_fn(q);
267}
268
269/**
270 * generic_unplug_device - fire a request queue
271 * @q: The &struct request_queue in question
272 *
273 * Description:
274 * Linux uses plugging to build bigger requests queues before letting
275 * the device have at them. If a queue is plugged, the I/O scheduler
276 * is still adding and merging requests on the queue. Once the queue
277 * gets unplugged, the request_fn defined for the queue is invoked and
278 * transfers started.
279 **/
280void generic_unplug_device(struct request_queue *q)
281{
282    if (blk_queue_plugged(q)) {
283        spin_lock_irq(q->queue_lock);
284        __generic_unplug_device(q);
285        spin_unlock_irq(q->queue_lock);
286    }
287}
288EXPORT_SYMBOL(generic_unplug_device);
289
290static void blk_backing_dev_unplug(struct backing_dev_info *bdi,
291                   struct page *page)
292{
293    struct request_queue *q = bdi->unplug_io_data;
294
295    blk_unplug(q);
296}
297
298void blk_unplug_work(struct work_struct *work)
299{
300    struct request_queue *q =
301        container_of(work, struct request_queue, unplug_work);
302
303    trace_block_unplug_io(q);
304    q->unplug_fn(q);
305}
306
307void blk_unplug_timeout(unsigned long data)
308{
309    struct request_queue *q = (struct request_queue *)data;
310
311    trace_block_unplug_timer(q);
312    kblockd_schedule_work(q, &q->unplug_work);
313}
314
315void blk_unplug(struct request_queue *q)
316{
317    /*
318     * devices don't necessarily have an ->unplug_fn defined
319     */
320    if (q->unplug_fn) {
321        trace_block_unplug_io(q);
322        q->unplug_fn(q);
323    }
324}
325EXPORT_SYMBOL(blk_unplug);
326
327/**
328 * blk_start_queue - restart a previously stopped queue
329 * @q: The &struct request_queue in question
330 *
331 * Description:
332 * blk_start_queue() will clear the stop flag on the queue, and call
333 * the request_fn for the queue if it was in a stopped state when
334 * entered. Also see blk_stop_queue(). Queue lock must be held.
335 **/
336void blk_start_queue(struct request_queue *q)
337{
338    WARN_ON(!irqs_disabled());
339
340    queue_flag_clear(QUEUE_FLAG_STOPPED, q);
341    __blk_run_queue(q);
342}
343EXPORT_SYMBOL(blk_start_queue);
344
345/**
346 * blk_stop_queue - stop a queue
347 * @q: The &struct request_queue in question
348 *
349 * Description:
350 * The Linux block layer assumes that a block driver will consume all
351 * entries on the request queue when the request_fn strategy is called.
352 * Often this will not happen, because of hardware limitations (queue
353 * depth settings). If a device driver gets a 'queue full' response,
354 * or if it simply chooses not to queue more I/O at one point, it can
355 * call this function to prevent the request_fn from being called until
356 * the driver has signalled it's ready to go again. This happens by calling
357 * blk_start_queue() to restart queue operations. Queue lock must be held.
358 **/
359void blk_stop_queue(struct request_queue *q)
360{
361    blk_remove_plug(q);
362    queue_flag_set(QUEUE_FLAG_STOPPED, q);
363}
364EXPORT_SYMBOL(blk_stop_queue);
365
366/**
367 * blk_sync_queue - cancel any pending callbacks on a queue
368 * @q: the queue
369 *
370 * Description:
371 * The block layer may perform asynchronous callback activity
372 * on a queue, such as calling the unplug function after a timeout.
373 * A block device may call blk_sync_queue to ensure that any
374 * such activity is cancelled, thus allowing it to release resources
375 * that the callbacks might use. The caller must already have made sure
376 * that its ->make_request_fn will not re-add plugging prior to calling
377 * this function.
378 *
379 */
380void blk_sync_queue(struct request_queue *q)
381{
382    del_timer_sync(&q->unplug_timer);
383    del_timer_sync(&q->timeout);
384    cancel_work_sync(&q->unplug_work);
385}
386EXPORT_SYMBOL(blk_sync_queue);
387
388/**
389 * __blk_run_queue - run a single device queue
390 * @q: The queue to run
391 *
392 * Description:
393 * See @blk_run_queue. This variant must be called with the queue lock
394 * held and interrupts disabled.
395 *
396 */
397void __blk_run_queue(struct request_queue *q)
398{
399    blk_remove_plug(q);
400
401    if (unlikely(blk_queue_stopped(q)))
402        return;
403
404    if (elv_queue_empty(q))
405        return;
406
407    /*
408     * Only recurse once to avoid overrunning the stack, let the unplug
409     * handling reinvoke the handler shortly if we already got there.
410     */
411    if (!queue_flag_test_and_set(QUEUE_FLAG_REENTER, q)) {
412        q->request_fn(q);
413        queue_flag_clear(QUEUE_FLAG_REENTER, q);
414    } else {
415        queue_flag_set(QUEUE_FLAG_PLUGGED, q);
416        kblockd_schedule_work(q, &q->unplug_work);
417    }
418}
419EXPORT_SYMBOL(__blk_run_queue);
420
421/**
422 * blk_run_queue - run a single device queue
423 * @q: The queue to run
424 *
425 * Description:
426 * Invoke request handling on this queue, if it has pending work to do.
427 * May be used to restart queueing when a request has completed.
428 */
429void blk_run_queue(struct request_queue *q)
430{
431    unsigned long flags;
432
433    spin_lock_irqsave(q->queue_lock, flags);
434    __blk_run_queue(q);
435    spin_unlock_irqrestore(q->queue_lock, flags);
436}
437EXPORT_SYMBOL(blk_run_queue);
438
439void blk_put_queue(struct request_queue *q)
440{
441    kobject_put(&q->kobj);
442}
443
444void blk_cleanup_queue(struct request_queue *q)
445{
446    /*
447     * We know we have process context here, so we can be a little
448     * cautious and ensure that pending block actions on this device
449     * are done before moving on. Going into this function, we should
450     * not have processes doing IO to this device.
451     */
452    blk_sync_queue(q);
453
454    del_timer_sync(&q->backing_dev_info.laptop_mode_wb_timer);
455    mutex_lock(&q->sysfs_lock);
456    queue_flag_set_unlocked(QUEUE_FLAG_DEAD, q);
457    mutex_unlock(&q->sysfs_lock);
458
459    if (q->elevator)
460        elevator_exit(q->elevator);
461
462    blk_put_queue(q);
463}
464EXPORT_SYMBOL(blk_cleanup_queue);
465
466static int blk_init_free_list(struct request_queue *q)
467{
468    struct request_list *rl = &q->rq;
469
470    if (unlikely(rl->rq_pool))
471        return 0;
472
473    rl->count[BLK_RW_SYNC] = rl->count[BLK_RW_ASYNC] = 0;
474    rl->starved[BLK_RW_SYNC] = rl->starved[BLK_RW_ASYNC] = 0;
475    rl->elvpriv = 0;
476    init_waitqueue_head(&rl->wait[BLK_RW_SYNC]);
477    init_waitqueue_head(&rl->wait[BLK_RW_ASYNC]);
478
479    rl->rq_pool = mempool_create_node(BLKDEV_MIN_RQ, mempool_alloc_slab,
480                mempool_free_slab, request_cachep, q->node);
481
482    if (!rl->rq_pool)
483        return -ENOMEM;
484
485    return 0;
486}
487
488struct request_queue *blk_alloc_queue(gfp_t gfp_mask)
489{
490    return blk_alloc_queue_node(gfp_mask, -1);
491}
492EXPORT_SYMBOL(blk_alloc_queue);
493
494struct request_queue *blk_alloc_queue_node(gfp_t gfp_mask, int node_id)
495{
496    struct request_queue *q;
497    int err;
498
499    q = kmem_cache_alloc_node(blk_requestq_cachep,
500                gfp_mask | __GFP_ZERO, node_id);
501    if (!q)
502        return NULL;
503
504    q->backing_dev_info.unplug_io_fn = blk_backing_dev_unplug;
505    q->backing_dev_info.unplug_io_data = q;
506    q->backing_dev_info.ra_pages =
507            (VM_MAX_READAHEAD * 1024) / PAGE_CACHE_SIZE;
508    q->backing_dev_info.state = 0;
509    q->backing_dev_info.capabilities = BDI_CAP_MAP_COPY;
510    q->backing_dev_info.name = "block";
511
512    err = bdi_init(&q->backing_dev_info);
513    if (err) {
514        kmem_cache_free(blk_requestq_cachep, q);
515        return NULL;
516    }
517
518    setup_timer(&q->backing_dev_info.laptop_mode_wb_timer,
519            laptop_mode_timer_fn, (unsigned long) q);
520    init_timer(&q->unplug_timer);
521    setup_timer(&q->timeout, blk_rq_timed_out_timer, (unsigned long) q);
522    INIT_LIST_HEAD(&q->timeout_list);
523    INIT_WORK(&q->unplug_work, blk_unplug_work);
524
525    kobject_init(&q->kobj, &blk_queue_ktype);
526
527    mutex_init(&q->sysfs_lock);
528    spin_lock_init(&q->__queue_lock);
529
530    return q;
531}
532EXPORT_SYMBOL(blk_alloc_queue_node);
533
534/**
535 * blk_init_queue - prepare a request queue for use with a block device
536 * @rfn: The function to be called to process requests that have been
537 * placed on the queue.
538 * @lock: Request queue spin lock
539 *
540 * Description:
541 * If a block device wishes to use the standard request handling procedures,
542 * which sorts requests and coalesces adjacent requests, then it must
543 * call blk_init_queue(). The function @rfn will be called when there
544 * are requests on the queue that need to be processed. If the device
545 * supports plugging, then @rfn may not be called immediately when requests
546 * are available on the queue, but may be called at some time later instead.
547 * Plugged queues are generally unplugged when a buffer belonging to one
548 * of the requests on the queue is needed, or due to memory pressure.
549 *
550 * @rfn is not required, or even expected, to remove all requests off the
551 * queue, but only as many as it can handle at a time. If it does leave
552 * requests on the queue, it is responsible for arranging that the requests
553 * get dealt with eventually.
554 *
555 * The queue spin lock must be held while manipulating the requests on the
556 * request queue; this lock will be taken also from interrupt context, so irq
557 * disabling is needed for it.
558 *
559 * Function returns a pointer to the initialized request queue, or %NULL if
560 * it didn't succeed.
561 *
562 * Note:
563 * blk_init_queue() must be paired with a blk_cleanup_queue() call
564 * when the block device is deactivated (such as at module unload).
565 **/
566
567struct request_queue *blk_init_queue(request_fn_proc *rfn, spinlock_t *lock)
568{
569    return blk_init_queue_node(rfn, lock, -1);
570}
571EXPORT_SYMBOL(blk_init_queue);
572
573struct request_queue *
574blk_init_queue_node(request_fn_proc *rfn, spinlock_t *lock, int node_id)
575{
576    struct request_queue *uninit_q, *q;
577
578    uninit_q = blk_alloc_queue_node(GFP_KERNEL, node_id);
579    if (!uninit_q)
580        return NULL;
581
582    q = blk_init_allocated_queue_node(uninit_q, rfn, lock, node_id);
583    if (!q)
584        blk_cleanup_queue(uninit_q);
585
586    return q;
587}
588EXPORT_SYMBOL(blk_init_queue_node);
589
590struct request_queue *
591blk_init_allocated_queue(struct request_queue *q, request_fn_proc *rfn,
592             spinlock_t *lock)
593{
594    return blk_init_allocated_queue_node(q, rfn, lock, -1);
595}
596EXPORT_SYMBOL(blk_init_allocated_queue);
597
598struct request_queue *
599blk_init_allocated_queue_node(struct request_queue *q, request_fn_proc *rfn,
600                  spinlock_t *lock, int node_id)
601{
602    if (!q)
603        return NULL;
604
605    q->node = node_id;
606    if (blk_init_free_list(q))
607        return NULL;
608
609    q->request_fn = rfn;
610    q->prep_rq_fn = NULL;
611    q->unplug_fn = generic_unplug_device;
612    q->queue_flags = QUEUE_FLAG_DEFAULT;
613    q->queue_lock = lock;
614
615    /*
616     * This also sets hw/phys segments, boundary and size
617     */
618    blk_queue_make_request(q, __make_request);
619
620    q->sg_reserved_size = INT_MAX;
621
622    /*
623     * all done
624     */
625    if (!elevator_init(q, NULL)) {
626        blk_queue_congestion_threshold(q);
627        return q;
628    }
629
630    return NULL;
631}
632EXPORT_SYMBOL(blk_init_allocated_queue_node);
633
634int blk_get_queue(struct request_queue *q)
635{
636    if (likely(!test_bit(QUEUE_FLAG_DEAD, &q->queue_flags))) {
637        kobject_get(&q->kobj);
638        return 0;
639    }
640
641    return 1;
642}
643
644static inline void blk_free_request(struct request_queue *q, struct request *rq)
645{
646    if (rq->cmd_flags & REQ_ELVPRIV)
647        elv_put_request(q, rq);
648    mempool_free(rq, q->rq.rq_pool);
649}
650
651static struct request *
652blk_alloc_request(struct request_queue *q, int flags, int priv, gfp_t gfp_mask)
653{
654    struct request *rq = mempool_alloc(q->rq.rq_pool, gfp_mask);
655
656    if (!rq)
657        return NULL;
658
659    blk_rq_init(q, rq);
660
661    rq->cmd_flags = flags | REQ_ALLOCED;
662
663    if (priv) {
664        if (unlikely(elv_set_request(q, rq, gfp_mask))) {
665            mempool_free(rq, q->rq.rq_pool);
666            return NULL;
667        }
668        rq->cmd_flags |= REQ_ELVPRIV;
669    }
670
671    return rq;
672}
673
674/*
675 * ioc_batching returns true if the ioc is a valid batching request and
676 * should be given priority access to a request.
677 */
678static inline int ioc_batching(struct request_queue *q, struct io_context *ioc)
679{
680    if (!ioc)
681        return 0;
682
683    /*
684     * Make sure the process is able to allocate at least 1 request
685     * even if the batch times out, otherwise we could theoretically
686     * lose wakeups.
687     */
688    return ioc->nr_batch_requests == q->nr_batching ||
689        (ioc->nr_batch_requests > 0
690        && time_before(jiffies, ioc->last_waited + BLK_BATCH_TIME));
691}
692
693/*
694 * ioc_set_batching sets ioc to be a new "batcher" if it is not one. This
695 * will cause the process to be a "batcher" on all queues in the system. This
696 * is the behaviour we want though - once it gets a wakeup it should be given
697 * a nice run.
698 */
699static void ioc_set_batching(struct request_queue *q, struct io_context *ioc)
700{
701    if (!ioc || ioc_batching(q, ioc))
702        return;
703
704    ioc->nr_batch_requests = q->nr_batching;
705    ioc->last_waited = jiffies;
706}
707
708static void __freed_request(struct request_queue *q, int sync)
709{
710    struct request_list *rl = &q->rq;
711
712    if (rl->count[sync] < queue_congestion_off_threshold(q))
713        blk_clear_queue_congested(q, sync);
714
715    if (rl->count[sync] + 1 <= q->nr_requests) {
716        if (waitqueue_active(&rl->wait[sync]))
717            wake_up(&rl->wait[sync]);
718
719        blk_clear_queue_full(q, sync);
720    }
721}
722
723/*
724 * A request has just been released. Account for it, update the full and
725 * congestion status, wake up any waiters. Called under q->queue_lock.
726 */
727static void freed_request(struct request_queue *q, int sync, int priv)
728{
729    struct request_list *rl = &q->rq;
730
731    rl->count[sync]--;
732    if (priv)
733        rl->elvpriv--;
734
735    __freed_request(q, sync);
736
737    if (unlikely(rl->starved[sync ^ 1]))
738        __freed_request(q, sync ^ 1);
739}
740
741/*
742 * Get a free request, queue_lock must be held.
743 * Returns NULL on failure, with queue_lock held.
744 * Returns !NULL on success, with queue_lock *not held*.
745 */
746static struct request *get_request(struct request_queue *q, int rw_flags,
747                   struct bio *bio, gfp_t gfp_mask)
748{
749    struct request *rq = NULL;
750    struct request_list *rl = &q->rq;
751    struct io_context *ioc = NULL;
752    const bool is_sync = rw_is_sync(rw_flags) != 0;
753    int may_queue, priv;
754
755    may_queue = elv_may_queue(q, rw_flags);
756    if (may_queue == ELV_MQUEUE_NO)
757        goto rq_starved;
758
759    if (rl->count[is_sync]+1 >= queue_congestion_on_threshold(q)) {
760        if (rl->count[is_sync]+1 >= q->nr_requests) {
761            ioc = current_io_context(GFP_ATOMIC, q->node);
762            /*
763             * The queue will fill after this allocation, so set
764             * it as full, and mark this process as "batching".
765             * This process will be allowed to complete a batch of
766             * requests, others will be blocked.
767             */
768            if (!blk_queue_full(q, is_sync)) {
769                ioc_set_batching(q, ioc);
770                blk_set_queue_full(q, is_sync);
771            } else {
772                if (may_queue != ELV_MQUEUE_MUST
773                        && !ioc_batching(q, ioc)) {
774                    /*
775                     * The queue is full and the allocating
776                     * process is not a "batcher", and not
777                     * exempted by the IO scheduler
778                     */
779                    goto out;
780                }
781            }
782        }
783        blk_set_queue_congested(q, is_sync);
784    }
785
786    /*
787     * Only allow batching queuers to allocate up to 50% over the defined
788     * limit of requests, otherwise we could have thousands of requests
789     * allocated with any setting of ->nr_requests
790     */
791    if (rl->count[is_sync] >= (3 * q->nr_requests / 2))
792        goto out;
793
794    rl->count[is_sync]++;
795    rl->starved[is_sync] = 0;
796
797    priv = !test_bit(QUEUE_FLAG_ELVSWITCH, &q->queue_flags);
798    if (priv)
799        rl->elvpriv++;
800
801    if (blk_queue_io_stat(q))
802        rw_flags |= REQ_IO_STAT;
803    spin_unlock_irq(q->queue_lock);
804
805    rq = blk_alloc_request(q, rw_flags, priv, gfp_mask);
806    if (unlikely(!rq)) {
807        /*
808         * Allocation failed presumably due to memory. Undo anything
809         * we might have messed up.
810         *
811         * Allocating task should really be put onto the front of the
812         * wait queue, but this is pretty rare.
813         */
814        spin_lock_irq(q->queue_lock);
815        freed_request(q, is_sync, priv);
816
817        /*
818         * in the very unlikely event that allocation failed and no
819         * requests for this direction was pending, mark us starved
820         * so that freeing of a request in the other direction will
821         * notice us. another possible fix would be to split the
822         * rq mempool into READ and WRITE
823         */
824rq_starved:
825        if (unlikely(rl->count[is_sync] == 0))
826            rl->starved[is_sync] = 1;
827
828        goto out;
829    }
830
831    /*
832     * ioc may be NULL here, and ioc_batching will be false. That's
833     * OK, if the queue is under the request limit then requests need
834     * not count toward the nr_batch_requests limit. There will always
835     * be some limit enforced by BLK_BATCH_TIME.
836     */
837    if (ioc_batching(q, ioc))
838        ioc->nr_batch_requests--;
839
840    trace_block_getrq(q, bio, rw_flags & 1);
841out:
842    return rq;
843}
844
845/*
846 * No available requests for this queue, unplug the device and wait for some
847 * requests to become available.
848 *
849 * Called with q->queue_lock held, and returns with it unlocked.
850 */
851static struct request *get_request_wait(struct request_queue *q, int rw_flags,
852                    struct bio *bio)
853{
854    const bool is_sync = rw_is_sync(rw_flags) != 0;
855    struct request *rq;
856
857    rq = get_request(q, rw_flags, bio, GFP_NOIO);
858    while (!rq) {
859        DEFINE_WAIT(wait);
860        struct io_context *ioc;
861        struct request_list *rl = &q->rq;
862
863        prepare_to_wait_exclusive(&rl->wait[is_sync], &wait,
864                TASK_UNINTERRUPTIBLE);
865
866        trace_block_sleeprq(q, bio, rw_flags & 1);
867
868        __generic_unplug_device(q);
869        spin_unlock_irq(q->queue_lock);
870        io_schedule();
871
872        /*
873         * After sleeping, we become a "batching" process and
874         * will be able to allocate at least one request, and
875         * up to a big batch of them for a small period time.
876         * See ioc_batching, ioc_set_batching
877         */
878        ioc = current_io_context(GFP_NOIO, q->node);
879        ioc_set_batching(q, ioc);
880
881        spin_lock_irq(q->queue_lock);
882        finish_wait(&rl->wait[is_sync], &wait);
883
884        rq = get_request(q, rw_flags, bio, GFP_NOIO);
885    };
886
887    return rq;
888}
889
890struct request *blk_get_request(struct request_queue *q, int rw, gfp_t gfp_mask)
891{
892    struct request *rq;
893
894    BUG_ON(rw != READ && rw != WRITE);
895
896    spin_lock_irq(q->queue_lock);
897    if (gfp_mask & __GFP_WAIT) {
898        rq = get_request_wait(q, rw, NULL);
899    } else {
900        rq = get_request(q, rw, NULL, gfp_mask);
901        if (!rq)
902            spin_unlock_irq(q->queue_lock);
903    }
904    /* q->queue_lock is unlocked at this point */
905
906    return rq;
907}
908EXPORT_SYMBOL(blk_get_request);
909
910/**
911 * blk_make_request - given a bio, allocate a corresponding struct request.
912 * @q: target request queue
913 * @bio: The bio describing the memory mappings that will be submitted for IO.
914 * It may be a chained-bio properly constructed by block/bio layer.
915 * @gfp_mask: gfp flags to be used for memory allocation
916 *
917 * blk_make_request is the parallel of generic_make_request for BLOCK_PC
918 * type commands. Where the struct request needs to be farther initialized by
919 * the caller. It is passed a &struct bio, which describes the memory info of
920 * the I/O transfer.
921 *
922 * The caller of blk_make_request must make sure that bi_io_vec
923 * are set to describe the memory buffers. That bio_data_dir() will return
924 * the needed direction of the request. (And all bio's in the passed bio-chain
925 * are properly set accordingly)
926 *
927 * If called under none-sleepable conditions, mapped bio buffers must not
928 * need bouncing, by calling the appropriate masked or flagged allocator,
929 * suitable for the target device. Otherwise the call to blk_queue_bounce will
930 * BUG.
931 *
932 * WARNING: When allocating/cloning a bio-chain, careful consideration should be
933 * given to how you allocate bios. In particular, you cannot use __GFP_WAIT for
934 * anything but the first bio in the chain. Otherwise you risk waiting for IO
935 * completion of a bio that hasn't been submitted yet, thus resulting in a
936 * deadlock. Alternatively bios should be allocated using bio_kmalloc() instead
937 * of bio_alloc(), as that avoids the mempool deadlock.
938 * If possible a big IO should be split into smaller parts when allocation
939 * fails. Partial allocation should not be an error, or you risk a live-lock.
940 */
941struct request *blk_make_request(struct request_queue *q, struct bio *bio,
942                 gfp_t gfp_mask)
943{
944    struct request *rq = blk_get_request(q, bio_data_dir(bio), gfp_mask);
945
946    if (unlikely(!rq))
947        return ERR_PTR(-ENOMEM);
948
949    for_each_bio(bio) {
950        struct bio *bounce_bio = bio;
951        int ret;
952
953        blk_queue_bounce(q, &bounce_bio);
954        ret = blk_rq_append_bio(q, rq, bounce_bio);
955        if (unlikely(ret)) {
956            blk_put_request(rq);
957            return ERR_PTR(ret);
958        }
959    }
960
961    return rq;
962}
963EXPORT_SYMBOL(blk_make_request);
964
965/**
966 * blk_requeue_request - put a request back on queue
967 * @q: request queue where request should be inserted
968 * @rq: request to be inserted
969 *
970 * Description:
971 * Drivers often keep queueing requests until the hardware cannot accept
972 * more, when that condition happens we need to put the request back
973 * on the queue. Must be called with queue lock held.
974 */
975void blk_requeue_request(struct request_queue *q, struct request *rq)
976{
977    blk_delete_timer(rq);
978    blk_clear_rq_complete(rq);
979    trace_block_rq_requeue(q, rq);
980
981    if (blk_rq_tagged(rq))
982        blk_queue_end_tag(q, rq);
983
984    BUG_ON(blk_queued_rq(rq));
985
986    elv_requeue_request(q, rq);
987}
988EXPORT_SYMBOL(blk_requeue_request);
989
990/**
991 * blk_insert_request - insert a special request into a request queue
992 * @q: request queue where request should be inserted
993 * @rq: request to be inserted
994 * @at_head: insert request at head or tail of queue
995 * @data: private data
996 *
997 * Description:
998 * Many block devices need to execute commands asynchronously, so they don't
999 * block the whole kernel from preemption during request execution. This is
1000 * accomplished normally by inserting aritficial requests tagged as
1001 * REQ_TYPE_SPECIAL in to the corresponding request queue, and letting them
1002 * be scheduled for actual execution by the request queue.
1003 *
1004 * We have the option of inserting the head or the tail of the queue.
1005 * Typically we use the tail for new ioctls and so forth. We use the head
1006 * of the queue for things like a QUEUE_FULL message from a device, or a
1007 * host that is unable to accept a particular command.
1008 */
1009void blk_insert_request(struct request_queue *q, struct request *rq,
1010            int at_head, void *data)
1011{
1012    int where = at_head ? ELEVATOR_INSERT_FRONT : ELEVATOR_INSERT_BACK;
1013    unsigned long flags;
1014
1015    /*
1016     * tell I/O scheduler that this isn't a regular read/write (ie it
1017     * must not attempt merges on this) and that it acts as a soft
1018     * barrier
1019     */
1020    rq->cmd_type = REQ_TYPE_SPECIAL;
1021
1022    rq->special = data;
1023
1024    spin_lock_irqsave(q->queue_lock, flags);
1025
1026    /*
1027     * If command is tagged, release the tag
1028     */
1029    if (blk_rq_tagged(rq))
1030        blk_queue_end_tag(q, rq);
1031
1032    drive_stat_acct(rq, 1);
1033    __elv_add_request(q, rq, where, 0);
1034    __blk_run_queue(q);
1035    spin_unlock_irqrestore(q->queue_lock, flags);
1036}
1037EXPORT_SYMBOL(blk_insert_request);
1038
1039/*
1040 * add-request adds a request to the linked list.
1041 * queue lock is held and interrupts disabled, as we muck with the
1042 * request queue list.
1043 */
1044static inline void add_request(struct request_queue *q, struct request *req)
1045{
1046    drive_stat_acct(req, 1);
1047
1048    /*
1049     * elevator indicated where it wants this request to be
1050     * inserted at elevator_merge time
1051     */
1052    __elv_add_request(q, req, ELEVATOR_INSERT_SORT, 0);
1053}
1054
1055static void part_round_stats_single(int cpu, struct hd_struct *part,
1056                    unsigned long now)
1057{
1058    if (now == part->stamp)
1059        return;
1060
1061    if (part_in_flight(part)) {
1062        __part_stat_add(cpu, part, time_in_queue,
1063                part_in_flight(part) * (now - part->stamp));
1064        __part_stat_add(cpu, part, io_ticks, (now - part->stamp));
1065    }
1066    part->stamp = now;
1067}
1068
1069/**
1070 * part_round_stats() - Round off the performance stats on a struct disk_stats.
1071 * @cpu: cpu number for stats access
1072 * @part: target partition
1073 *
1074 * The average IO queue length and utilisation statistics are maintained
1075 * by observing the current state of the queue length and the amount of
1076 * time it has been in this state for.
1077 *
1078 * Normally, that accounting is done on IO completion, but that can result
1079 * in more than a second's worth of IO being accounted for within any one
1080 * second, leading to >100% utilisation. To deal with that, we call this
1081 * function to do a round-off before returning the results when reading
1082 * /proc/diskstats. This accounts immediately for all queue usage up to
1083 * the current jiffies and restarts the counters again.
1084 */
1085void part_round_stats(int cpu, struct hd_struct *part)
1086{
1087    unsigned long now = jiffies;
1088
1089    if (part->partno)
1090        part_round_stats_single(cpu, &part_to_disk(part)->part0, now);
1091    part_round_stats_single(cpu, part, now);
1092}
1093EXPORT_SYMBOL_GPL(part_round_stats);
1094
1095/*
1096 * queue lock must be held
1097 */
1098void __blk_put_request(struct request_queue *q, struct request *req)
1099{
1100    if (unlikely(!q))
1101        return;
1102    if (unlikely(--req->ref_count))
1103        return;
1104
1105    elv_completed_request(q, req);
1106
1107    /* this is a bio leak */
1108    WARN_ON(req->bio != NULL);
1109
1110    /*
1111     * Request may not have originated from ll_rw_blk. if not,
1112     * it didn't come out of our reserved rq pools
1113     */
1114    if (req->cmd_flags & REQ_ALLOCED) {
1115        int is_sync = rq_is_sync(req) != 0;
1116        int priv = req->cmd_flags & REQ_ELVPRIV;
1117
1118        BUG_ON(!list_empty(&req->queuelist));
1119        BUG_ON(!hlist_unhashed(&req->hash));
1120
1121        blk_free_request(q, req);
1122        freed_request(q, is_sync, priv);
1123    }
1124}
1125EXPORT_SYMBOL_GPL(__blk_put_request);
1126
1127void blk_put_request(struct request *req)
1128{
1129    unsigned long flags;
1130    struct request_queue *q = req->q;
1131
1132    spin_lock_irqsave(q->queue_lock, flags);
1133    __blk_put_request(q, req);
1134    spin_unlock_irqrestore(q->queue_lock, flags);
1135}
1136EXPORT_SYMBOL(blk_put_request);
1137
1138void init_request_from_bio(struct request *req, struct bio *bio)
1139{
1140    req->cpu = bio->bi_comp_cpu;
1141    req->cmd_type = REQ_TYPE_FS;
1142
1143    /*
1144     * Inherit FAILFAST from bio (for read-ahead, and explicit
1145     * FAILFAST). FAILFAST flags are identical for req and bio.
1146     */
1147    if (bio_rw_flagged(bio, BIO_RW_AHEAD))
1148        req->cmd_flags |= REQ_FAILFAST_MASK;
1149    else
1150        req->cmd_flags |= bio->bi_rw & REQ_FAILFAST_MASK;
1151
1152    if (bio_rw_flagged(bio, BIO_RW_DISCARD))
1153        req->cmd_flags |= REQ_DISCARD;
1154    if (bio_rw_flagged(bio, BIO_RW_BARRIER))
1155        req->cmd_flags |= REQ_HARDBARRIER;
1156    if (bio_rw_flagged(bio, BIO_RW_SYNCIO))
1157        req->cmd_flags |= REQ_RW_SYNC;
1158    if (bio_rw_flagged(bio, BIO_RW_META))
1159        req->cmd_flags |= REQ_RW_META;
1160    if (bio_rw_flagged(bio, BIO_RW_NOIDLE))
1161        req->cmd_flags |= REQ_NOIDLE;
1162
1163    req->errors = 0;
1164    req->__sector = bio->bi_sector;
1165    req->ioprio = bio_prio(bio);
1166    blk_rq_bio_prep(req->q, req, bio);
1167}
1168
1169/*
1170 * Only disabling plugging for non-rotational devices if it does tagging
1171 * as well, otherwise we do need the proper merging
1172 */
1173static inline bool queue_should_plug(struct request_queue *q)
1174{
1175    return !(blk_queue_nonrot(q) && blk_queue_tagged(q));
1176}
1177
1178static int __make_request(struct request_queue *q, struct bio *bio)
1179{
1180    struct request *req;
1181    int el_ret;
1182    unsigned int bytes = bio->bi_size;
1183    const unsigned short prio = bio_prio(bio);
1184    const bool sync = bio_rw_flagged(bio, BIO_RW_SYNCIO);
1185    const bool unplug = bio_rw_flagged(bio, BIO_RW_UNPLUG);
1186    const unsigned int ff = bio->bi_rw & REQ_FAILFAST_MASK;
1187    int rw_flags;
1188
1189    if (bio_rw_flagged(bio, BIO_RW_BARRIER) &&
1190        (q->next_ordered == QUEUE_ORDERED_NONE)) {
1191        bio_endio(bio, -EOPNOTSUPP);
1192        return 0;
1193    }
1194    /*
1195     * low level driver can indicate that it wants pages above a
1196     * certain limit bounced to low memory (ie for highmem, or even
1197     * ISA dma in theory)
1198     */
1199    blk_queue_bounce(q, &bio);
1200
1201    spin_lock_irq(q->queue_lock);
1202
1203    if (unlikely(bio_rw_flagged(bio, BIO_RW_BARRIER)) || elv_queue_empty(q))
1204        goto get_rq;
1205
1206    el_ret = elv_merge(q, &req, bio);
1207    switch (el_ret) {
1208    case ELEVATOR_BACK_MERGE:
1209        BUG_ON(!rq_mergeable(req));
1210
1211        if (!ll_back_merge_fn(q, req, bio))
1212            break;
1213
1214        trace_block_bio_backmerge(q, bio);
1215
1216        if ((req->cmd_flags & REQ_FAILFAST_MASK) != ff)
1217            blk_rq_set_mixed_merge(req);
1218
1219        req->biotail->bi_next = bio;
1220        req->biotail = bio;
1221        req->__data_len += bytes;
1222        req->ioprio = ioprio_best(req->ioprio, prio);
1223        if (!blk_rq_cpu_valid(req))
1224            req->cpu = bio->bi_comp_cpu;
1225        drive_stat_acct(req, 0);
1226        elv_bio_merged(q, req, bio);
1227        if (!attempt_back_merge(q, req))
1228            elv_merged_request(q, req, el_ret);
1229        goto out;
1230
1231    case ELEVATOR_FRONT_MERGE:
1232        BUG_ON(!rq_mergeable(req));
1233
1234        if (!ll_front_merge_fn(q, req, bio))
1235            break;
1236
1237        trace_block_bio_frontmerge(q, bio);
1238
1239        if ((req->cmd_flags & REQ_FAILFAST_MASK) != ff) {
1240            blk_rq_set_mixed_merge(req);
1241            req->cmd_flags &= ~REQ_FAILFAST_MASK;
1242            req->cmd_flags |= ff;
1243        }
1244
1245        bio->bi_next = req->bio;
1246        req->bio = bio;
1247
1248        /*
1249         * may not be valid. if the low level driver said
1250         * it didn't need a bounce buffer then it better
1251         * not touch req->buffer either...
1252         */
1253        req->buffer = bio_data(bio);
1254        req->__sector = bio->bi_sector;
1255        req->__data_len += bytes;
1256        req->ioprio = ioprio_best(req->ioprio, prio);
1257        if (!blk_rq_cpu_valid(req))
1258            req->cpu = bio->bi_comp_cpu;
1259        drive_stat_acct(req, 0);
1260        elv_bio_merged(q, req, bio);
1261        if (!attempt_front_merge(q, req))
1262            elv_merged_request(q, req, el_ret);
1263        goto out;
1264
1265    /* ELV_NO_MERGE: elevator says don't/can't merge. */
1266    default:
1267        ;
1268    }
1269
1270get_rq:
1271    /*
1272     * This sync check and mask will be re-done in init_request_from_bio(),
1273     * but we need to set it earlier to expose the sync flag to the
1274     * rq allocator and io schedulers.
1275     */
1276    rw_flags = bio_data_dir(bio);
1277    if (sync)
1278        rw_flags |= REQ_RW_SYNC;
1279
1280    /*
1281     * Grab a free request. This is might sleep but can not fail.
1282     * Returns with the queue unlocked.
1283     */
1284    req = get_request_wait(q, rw_flags, bio);
1285
1286    /*
1287     * After dropping the lock and possibly sleeping here, our request
1288     * may now be mergeable after it had proven unmergeable (above).
1289     * We don't worry about that case for efficiency. It won't happen
1290     * often, and the elevators are able to handle it.
1291     */
1292    init_request_from_bio(req, bio);
1293
1294    spin_lock_irq(q->queue_lock);
1295    if (test_bit(QUEUE_FLAG_SAME_COMP, &q->queue_flags) ||
1296        bio_flagged(bio, BIO_CPU_AFFINE))
1297        req->cpu = blk_cpu_to_group(smp_processor_id());
1298    if (queue_should_plug(q) && elv_queue_empty(q))
1299        blk_plug_device(q);
1300    add_request(q, req);
1301out:
1302    if (unplug || !queue_should_plug(q))
1303        __generic_unplug_device(q);
1304    spin_unlock_irq(q->queue_lock);
1305    return 0;
1306}
1307
1308/*
1309 * If bio->bi_dev is a partition, remap the location
1310 */
1311static inline void blk_partition_remap(struct bio *bio)
1312{
1313    struct block_device *bdev = bio->bi_bdev;
1314
1315    if (bio_sectors(bio) && bdev != bdev->bd_contains) {
1316        struct hd_struct *p = bdev->bd_part;
1317
1318        bio->bi_sector += p->start_sect;
1319        bio->bi_bdev = bdev->bd_contains;
1320
1321        trace_block_remap(bdev_get_queue(bio->bi_bdev), bio,
1322                    bdev->bd_dev,
1323                    bio->bi_sector - p->start_sect);
1324    }
1325}
1326
1327static void handle_bad_sector(struct bio *bio)
1328{
1329    char b[BDEVNAME_SIZE];
1330
1331    printk(KERN_INFO "attempt to access beyond end of device\n");
1332    printk(KERN_INFO "%s: rw=%ld, want=%Lu, limit=%Lu\n",
1333            bdevname(bio->bi_bdev, b),
1334            bio->bi_rw,
1335            (unsigned long long)bio->bi_sector + bio_sectors(bio),
1336            (long long)(bio->bi_bdev->bd_inode->i_size >> 9));
1337
1338    set_bit(BIO_EOF, &bio->bi_flags);
1339}
1340
1341#ifdef CONFIG_FAIL_MAKE_REQUEST
1342
1343static DECLARE_FAULT_ATTR(fail_make_request);
1344
1345static int __init setup_fail_make_request(char *str)
1346{
1347    return setup_fault_attr(&fail_make_request, str);
1348}
1349__setup("fail_make_request=", setup_fail_make_request);
1350
1351static int should_fail_request(struct bio *bio)
1352{
1353    struct hd_struct *part = bio->bi_bdev->bd_part;
1354
1355    if (part_to_disk(part)->part0.make_it_fail || part->make_it_fail)
1356        return should_fail(&fail_make_request, bio->bi_size);
1357
1358    return 0;
1359}
1360
1361static int __init fail_make_request_debugfs(void)
1362{
1363    return init_fault_attr_dentries(&fail_make_request,
1364                    "fail_make_request");
1365}
1366
1367late_initcall(fail_make_request_debugfs);
1368
1369#else /* CONFIG_FAIL_MAKE_REQUEST */
1370
1371static inline int should_fail_request(struct bio *bio)
1372{
1373    return 0;
1374}
1375
1376#endif /* CONFIG_FAIL_MAKE_REQUEST */
1377
1378/*
1379 * Check whether this bio extends beyond the end of the device.
1380 */
1381static inline int bio_check_eod(struct bio *bio, unsigned int nr_sectors)
1382{
1383    sector_t maxsector;
1384
1385    if (!nr_sectors)
1386        return 0;
1387
1388    /* Test device or partition size, when known. */
1389    maxsector = bio->bi_bdev->bd_inode->i_size >> 9;
1390    if (maxsector) {
1391        sector_t sector = bio->bi_sector;
1392
1393        if (maxsector < nr_sectors || maxsector - nr_sectors < sector) {
1394            /*
1395             * This may well happen - the kernel calls bread()
1396             * without checking the size of the device, e.g., when
1397             * mounting a device.
1398             */
1399            handle_bad_sector(bio);
1400            return 1;
1401        }
1402    }
1403
1404    return 0;
1405}
1406
1407/**
1408 * generic_make_request - hand a buffer to its device driver for I/O
1409 * @bio: The bio describing the location in memory and on the device.
1410 *
1411 * generic_make_request() is used to make I/O requests of block
1412 * devices. It is passed a &struct bio, which describes the I/O that needs
1413 * to be done.
1414 *
1415 * generic_make_request() does not return any status. The
1416 * success/failure status of the request, along with notification of
1417 * completion, is delivered asynchronously through the bio->bi_end_io
1418 * function described (one day) else where.
1419 *
1420 * The caller of generic_make_request must make sure that bi_io_vec
1421 * are set to describe the memory buffer, and that bi_dev and bi_sector are
1422 * set to describe the device address, and the
1423 * bi_end_io and optionally bi_private are set to describe how
1424 * completion notification should be signaled.
1425 *
1426 * generic_make_request and the drivers it calls may use bi_next if this
1427 * bio happens to be merged with someone else, and may change bi_dev and
1428 * bi_sector for remaps as it sees fit. So the values of these fields
1429 * should NOT be depended on after the call to generic_make_request.
1430 */
1431static inline void __generic_make_request(struct bio *bio)
1432{
1433    struct request_queue *q;
1434    sector_t old_sector;
1435    int ret, nr_sectors = bio_sectors(bio);
1436    dev_t old_dev;
1437    int err = -EIO;
1438
1439    might_sleep();
1440
1441    if (bio_check_eod(bio, nr_sectors))
1442        goto end_io;
1443
1444    /*
1445     * Resolve the mapping until finished. (drivers are
1446     * still free to implement/resolve their own stacking
1447     * by explicitly returning 0)
1448     *
1449     * NOTE: we don't repeat the blk_size check for each new device.
1450     * Stacking drivers are expected to know what they are doing.
1451     */
1452    old_sector = -1;
1453    old_dev = 0;
1454    do {
1455        char b[BDEVNAME_SIZE];
1456
1457        q = bdev_get_queue(bio->bi_bdev);
1458        if (unlikely(!q)) {
1459            printk(KERN_ERR
1460                   "generic_make_request: Trying to access "
1461                "nonexistent block-device %s (%Lu)\n",
1462                bdevname(bio->bi_bdev, b),
1463                (long long) bio->bi_sector);
1464            goto end_io;
1465        }
1466
1467        if (unlikely(!bio_rw_flagged(bio, BIO_RW_DISCARD) &&
1468                 nr_sectors > queue_max_hw_sectors(q))) {
1469            printk(KERN_ERR "bio too big device %s (%u > %u)\n",
1470                   bdevname(bio->bi_bdev, b),
1471                   bio_sectors(bio),
1472                   queue_max_hw_sectors(q));
1473            goto end_io;
1474        }
1475
1476        if (unlikely(test_bit(QUEUE_FLAG_DEAD, &q->queue_flags)))
1477            goto end_io;
1478
1479        if (should_fail_request(bio))
1480            goto end_io;
1481
1482        /*
1483         * If this device has partitions, remap block n
1484         * of partition p to block n+start(p) of the disk.
1485         */
1486        blk_partition_remap(bio);
1487
1488        if (bio_integrity_enabled(bio) && bio_integrity_prep(bio))
1489            goto end_io;
1490
1491        if (old_sector != -1)
1492            trace_block_remap(q, bio, old_dev, old_sector);
1493
1494        old_sector = bio->bi_sector;
1495        old_dev = bio->bi_bdev->bd_dev;
1496
1497        if (bio_check_eod(bio, nr_sectors))
1498            goto end_io;
1499
1500        if (bio_rw_flagged(bio, BIO_RW_DISCARD) &&
1501            !blk_queue_discard(q)) {
1502            err = -EOPNOTSUPP;
1503            goto end_io;
1504        }
1505
1506        trace_block_bio_queue(q, bio);
1507
1508        ret = q->make_request_fn(q, bio);
1509    } while (ret);
1510
1511    return;
1512
1513end_io:
1514    bio_endio(bio, err);
1515}
1516
1517/*
1518 * We only want one ->make_request_fn to be active at a time,
1519 * else stack usage with stacked devices could be a problem.
1520 * So use current->bio_list to keep a list of requests
1521 * submited by a make_request_fn function.
1522 * current->bio_list is also used as a flag to say if
1523 * generic_make_request is currently active in this task or not.
1524 * If it is NULL, then no make_request is active. If it is non-NULL,
1525 * then a make_request is active, and new requests should be added
1526 * at the tail
1527 */
1528void generic_make_request(struct bio *bio)
1529{
1530    struct bio_list bio_list_on_stack;
1531
1532    if (current->bio_list) {
1533        /* make_request is active */
1534        bio_list_add(current->bio_list, bio);
1535        return;
1536    }
1537    /* following loop may be a bit non-obvious, and so deserves some
1538     * explanation.
1539     * Before entering the loop, bio->bi_next is NULL (as all callers
1540     * ensure that) so we have a list with a single bio.
1541     * We pretend that we have just taken it off a longer list, so
1542     * we assign bio_list to a pointer to the bio_list_on_stack,
1543     * thus initialising the bio_list of new bios to be
1544     * added. __generic_make_request may indeed add some more bios
1545     * through a recursive call to generic_make_request. If it
1546     * did, we find a non-NULL value in bio_list and re-enter the loop
1547     * from the top. In this case we really did just take the bio
1548     * of the top of the list (no pretending) and so remove it from
1549     * bio_list, and call into __generic_make_request again.
1550     *
1551     * The loop was structured like this to make only one call to
1552     * __generic_make_request (which is important as it is large and
1553     * inlined) and to keep the structure simple.
1554     */
1555    BUG_ON(bio->bi_next);
1556    bio_list_init(&bio_list_on_stack);
1557    current->bio_list = &bio_list_on_stack;
1558    do {
1559        __generic_make_request(bio);
1560        bio = bio_list_pop(current->bio_list);
1561    } while (bio);
1562    current->bio_list = NULL; /* deactivate */
1563}
1564EXPORT_SYMBOL(generic_make_request);
1565
1566/**
1567 * submit_bio - submit a bio to the block device layer for I/O
1568 * @rw: whether to %READ or %WRITE, or maybe to %READA (read ahead)
1569 * @bio: The &struct bio which describes the I/O
1570 *
1571 * submit_bio() is very similar in purpose to generic_make_request(), and
1572 * uses that function to do most of the work. Both are fairly rough
1573 * interfaces; @bio must be presetup and ready for I/O.
1574 *
1575 */
1576void submit_bio(int rw, struct bio *bio)
1577{
1578    int count = bio_sectors(bio);
1579
1580    bio->bi_rw |= rw;
1581
1582    /*
1583     * If it's a regular read/write or a barrier with data attached,
1584     * go through the normal accounting stuff before submission.
1585     */
1586    if (bio_has_data(bio) && !(rw & (1 << BIO_RW_DISCARD))) {
1587        if (rw & WRITE) {
1588            count_vm_events(PGPGOUT, count);
1589        } else {
1590            task_io_account_read(bio->bi_size);
1591            count_vm_events(PGPGIN, count);
1592        }
1593
1594        if (unlikely(block_dump)) {
1595            char b[BDEVNAME_SIZE];
1596            printk(KERN_DEBUG "%s(%d): %s block %Lu on %s\n",
1597            current->comm, task_pid_nr(current),
1598                (rw & WRITE) ? "WRITE" : "READ",
1599                (unsigned long long)bio->bi_sector,
1600                bdevname(bio->bi_bdev, b));
1601        }
1602    }
1603
1604    generic_make_request(bio);
1605}
1606EXPORT_SYMBOL(submit_bio);
1607
1608/**
1609 * blk_rq_check_limits - Helper function to check a request for the queue limit
1610 * @q: the queue
1611 * @rq: the request being checked
1612 *
1613 * Description:
1614 * @rq may have been made based on weaker limitations of upper-level queues
1615 * in request stacking drivers, and it may violate the limitation of @q.
1616 * Since the block layer and the underlying device driver trust @rq
1617 * after it is inserted to @q, it should be checked against @q before
1618 * the insertion using this generic function.
1619 *
1620 * This function should also be useful for request stacking drivers
1621 * in some cases below, so export this fuction.
1622 * Request stacking drivers like request-based dm may change the queue
1623 * limits while requests are in the queue (e.g. dm's table swapping).
1624 * Such request stacking drivers should check those requests agaist
1625 * the new queue limits again when they dispatch those requests,
1626 * although such checkings are also done against the old queue limits
1627 * when submitting requests.
1628 */
1629int blk_rq_check_limits(struct request_queue *q, struct request *rq)
1630{
1631    if (blk_rq_sectors(rq) > queue_max_sectors(q) ||
1632        blk_rq_bytes(rq) > queue_max_hw_sectors(q) << 9) {
1633        printk(KERN_ERR "%s: over max size limit.\n", __func__);
1634        return -EIO;
1635    }
1636
1637    /*
1638     * queue's settings related to segment counting like q->bounce_pfn
1639     * may differ from that of other stacking queues.
1640     * Recalculate it to check the request correctly on this queue's
1641     * limitation.
1642     */
1643    blk_recalc_rq_segments(rq);
1644    if (rq->nr_phys_segments > queue_max_segments(q)) {
1645        printk(KERN_ERR "%s: over max segments limit.\n", __func__);
1646        return -EIO;
1647    }
1648
1649    return 0;
1650}
1651EXPORT_SYMBOL_GPL(blk_rq_check_limits);
1652
1653/**
1654 * blk_insert_cloned_request - Helper for stacking drivers to submit a request
1655 * @q: the queue to submit the request
1656 * @rq: the request being queued
1657 */
1658int blk_insert_cloned_request(struct request_queue *q, struct request *rq)
1659{
1660    unsigned long flags;
1661
1662    if (blk_rq_check_limits(q, rq))
1663        return -EIO;
1664
1665#ifdef CONFIG_FAIL_MAKE_REQUEST
1666    if (rq->rq_disk && rq->rq_disk->part0.make_it_fail &&
1667        should_fail(&fail_make_request, blk_rq_bytes(rq)))
1668        return -EIO;
1669#endif
1670
1671    spin_lock_irqsave(q->queue_lock, flags);
1672
1673    /*
1674     * Submitting request must be dequeued before calling this function
1675     * because it will be linked to another request_queue
1676     */
1677    BUG_ON(blk_queued_rq(rq));
1678
1679    drive_stat_acct(rq, 1);
1680    __elv_add_request(q, rq, ELEVATOR_INSERT_BACK, 0);
1681
1682    spin_unlock_irqrestore(q->queue_lock, flags);
1683
1684    return 0;
1685}
1686EXPORT_SYMBOL_GPL(blk_insert_cloned_request);
1687
1688/**
1689 * blk_rq_err_bytes - determine number of bytes till the next failure boundary
1690 * @rq: request to examine
1691 *
1692 * Description:
1693 * A request could be merge of IOs which require different failure
1694 * handling. This function determines the number of bytes which
1695 * can be failed from the beginning of the request without
1696 * crossing into area which need to be retried further.
1697 *
1698 * Return:
1699 * The number of bytes to fail.
1700 *
1701 * Context:
1702 * queue_lock must be held.
1703 */
1704unsigned int blk_rq_err_bytes(const struct request *rq)
1705{
1706    unsigned int ff = rq->cmd_flags & REQ_FAILFAST_MASK;
1707    unsigned int bytes = 0;
1708    struct bio *bio;
1709
1710    if (!(rq->cmd_flags & REQ_MIXED_MERGE))
1711        return blk_rq_bytes(rq);
1712
1713    /*
1714     * Currently the only 'mixing' which can happen is between
1715     * different fastfail types. We can safely fail portions
1716     * which have all the failfast bits that the first one has -
1717     * the ones which are at least as eager to fail as the first
1718     * one.
1719     */
1720    for (bio = rq->bio; bio; bio = bio->bi_next) {
1721        if ((bio->bi_rw & ff) != ff)
1722            break;
1723        bytes += bio->bi_size;
1724    }
1725
1726    /* this could lead to infinite loop */
1727    BUG_ON(blk_rq_bytes(rq) && !bytes);
1728    return bytes;
1729}
1730EXPORT_SYMBOL_GPL(blk_rq_err_bytes);
1731
1732static void blk_account_io_completion(struct request *req, unsigned int bytes)
1733{
1734    if (blk_do_io_stat(req)) {
1735        const int rw = rq_data_dir(req);
1736        struct hd_struct *part;
1737        int cpu;
1738
1739        cpu = part_stat_lock();
1740        part = disk_map_sector_rcu(req->rq_disk, blk_rq_pos(req));
1741        part_stat_add(cpu, part, sectors[rw], bytes >> 9);
1742        part_stat_unlock();
1743    }
1744}
1745
1746static void blk_account_io_done(struct request *req)
1747{
1748    /*
1749     * Account IO completion. bar_rq isn't accounted as a normal
1750     * IO on queueing nor completion. Accounting the containing
1751     * request is enough.
1752     */
1753    if (blk_do_io_stat(req) && req != &req->q->bar_rq) {
1754        unsigned long duration = jiffies - req->start_time;
1755        const int rw = rq_data_dir(req);
1756        struct hd_struct *part;
1757        int cpu;
1758
1759        cpu = part_stat_lock();
1760        part = disk_map_sector_rcu(req->rq_disk, blk_rq_pos(req));
1761
1762        part_stat_inc(cpu, part, ios[rw]);
1763        part_stat_add(cpu, part, ticks[rw], duration);
1764        part_round_stats(cpu, part);
1765        part_dec_in_flight(part, rw);
1766
1767        part_stat_unlock();
1768    }
1769}
1770
1771/**
1772 * blk_peek_request - peek at the top of a request queue
1773 * @q: request queue to peek at
1774 *
1775 * Description:
1776 * Return the request at the top of @q. The returned request
1777 * should be started using blk_start_request() before LLD starts
1778 * processing it.
1779 *
1780 * Return:
1781 * Pointer to the request at the top of @q if available. Null
1782 * otherwise.
1783 *
1784 * Context:
1785 * queue_lock must be held.
1786 */
1787struct request *blk_peek_request(struct request_queue *q)
1788{
1789    struct request *rq;
1790    int ret;
1791
1792    while ((rq = __elv_next_request(q)) != NULL) {
1793        if (!(rq->cmd_flags & REQ_STARTED)) {
1794            /*
1795             * This is the first time the device driver
1796             * sees this request (possibly after
1797             * requeueing). Notify IO scheduler.
1798             */
1799            if (blk_sorted_rq(rq))
1800                elv_activate_rq(q, rq);
1801
1802            /*
1803             * just mark as started even if we don't start
1804             * it, a request that has been delayed should
1805             * not be passed by new incoming requests
1806             */
1807            rq->cmd_flags |= REQ_STARTED;
1808            trace_block_rq_issue(q, rq);
1809        }
1810
1811        if (!q->boundary_rq || q->boundary_rq == rq) {
1812            q->end_sector = rq_end_sector(rq);
1813            q->boundary_rq = NULL;
1814        }
1815
1816        if (rq->cmd_flags & REQ_DONTPREP)
1817            break;
1818
1819        if (q->dma_drain_size && blk_rq_bytes(rq)) {
1820            /*
1821             * make sure space for the drain appears we
1822             * know we can do this because max_hw_segments
1823             * has been adjusted to be one fewer than the
1824             * device can handle
1825             */
1826            rq->nr_phys_segments++;
1827        }
1828
1829        if (!q->prep_rq_fn)
1830            break;
1831
1832        ret = q->prep_rq_fn(q, rq);
1833        if (ret == BLKPREP_OK) {
1834            break;
1835        } else if (ret == BLKPREP_DEFER) {
1836            /*
1837             * the request may have been (partially) prepped.
1838             * we need to keep this request in the front to
1839             * avoid resource deadlock. REQ_STARTED will
1840             * prevent other fs requests from passing this one.
1841             */
1842            if (q->dma_drain_size && blk_rq_bytes(rq) &&
1843                !(rq->cmd_flags & REQ_DONTPREP)) {
1844                /*
1845                 * remove the space for the drain we added
1846                 * so that we don't add it again
1847                 */
1848                --rq->nr_phys_segments;
1849            }
1850
1851            rq = NULL;
1852            break;
1853        } else if (ret == BLKPREP_KILL) {
1854            rq->cmd_flags |= REQ_QUIET;
1855            /*
1856             * Mark this request as started so we don't trigger
1857             * any debug logic in the end I/O path.
1858             */
1859            blk_start_request(rq);
1860            __blk_end_request_all(rq, -EIO);
1861        } else {
1862            printk(KERN_ERR "%s: bad return=%d\n", __func__, ret);
1863            break;
1864        }
1865    }
1866
1867    return rq;
1868}
1869EXPORT_SYMBOL(blk_peek_request);
1870
1871void blk_dequeue_request(struct request *rq)
1872{
1873    struct request_queue *q = rq->q;
1874
1875    BUG_ON(list_empty(&rq->queuelist));
1876    BUG_ON(ELV_ON_HASH(rq));
1877
1878    list_del_init(&rq->queuelist);
1879
1880    /*
1881     * the time frame between a request being removed from the lists
1882     * and to it is freed is accounted as io that is in progress at
1883     * the driver side.
1884     */
1885    if (blk_account_rq(rq)) {
1886        q->in_flight[rq_is_sync(rq)]++;
1887        set_io_start_time_ns(rq);
1888    }
1889}
1890
1891/**
1892 * blk_start_request - start request processing on the driver
1893 * @req: request to dequeue
1894 *
1895 * Description:
1896 * Dequeue @req and start timeout timer on it. This hands off the
1897 * request to the driver.
1898 *
1899 * Block internal functions which don't want to start timer should
1900 * call blk_dequeue_request().
1901 *
1902 * Context:
1903 * queue_lock must be held.
1904 */
1905void blk_start_request(struct request *req)
1906{
1907    blk_dequeue_request(req);
1908
1909    /*
1910     * We are now handing the request to the hardware, initialize
1911     * resid_len to full count and add the timeout handler.
1912     */
1913    req->resid_len = blk_rq_bytes(req);
1914    if (unlikely(blk_bidi_rq(req)))
1915        req->next_rq->resid_len = blk_rq_bytes(req->next_rq);
1916
1917    blk_add_timer(req);
1918}
1919EXPORT_SYMBOL(blk_start_request);
1920
1921/**
1922 * blk_fetch_request - fetch a request from a request queue
1923 * @q: request queue to fetch a request from
1924 *
1925 * Description:
1926 * Return the request at the top of @q. The request is started on
1927 * return and LLD can start processing it immediately.
1928 *
1929 * Return:
1930 * Pointer to the request at the top of @q if available. Null
1931 * otherwise.
1932 *
1933 * Context:
1934 * queue_lock must be held.
1935 */
1936struct request *blk_fetch_request(struct request_queue *q)
1937{
1938    struct request *rq;
1939
1940    rq = blk_peek_request(q);
1941    if (rq)
1942        blk_start_request(rq);
1943    return rq;
1944}
1945EXPORT_SYMBOL(blk_fetch_request);
1946
1947/**
1948 * blk_update_request - Special helper function for request stacking drivers
1949 * @req: the request being processed
1950 * @error: %0 for success, < %0 for error
1951 * @nr_bytes: number of bytes to complete @req
1952 *
1953 * Description:
1954 * Ends I/O on a number of bytes attached to @req, but doesn't complete
1955 * the request structure even if @req doesn't have leftover.
1956 * If @req has leftover, sets it up for the next range of segments.
1957 *
1958 * This special helper function is only for request stacking drivers
1959 * (e.g. request-based dm) so that they can handle partial completion.
1960 * Actual device drivers should use blk_end_request instead.
1961 *
1962 * Passing the result of blk_rq_bytes() as @nr_bytes guarantees
1963 * %false return from this function.
1964 *
1965 * Return:
1966 * %false - this request doesn't have any more data
1967 * %true - this request has more data
1968 **/
1969bool blk_update_request(struct request *req, int error, unsigned int nr_bytes)
1970{
1971    int total_bytes, bio_nbytes, next_idx = 0;
1972    struct bio *bio;
1973
1974    if (!req->bio)
1975        return false;
1976
1977    trace_block_rq_complete(req->q, req);
1978
1979    /*
1980     * For fs requests, rq is just carrier of independent bio's
1981     * and each partial completion should be handled separately.
1982     * Reset per-request error on each partial completion.
1983     *
1984     * TODO: tj: This is too subtle. It would be better to let
1985     * low level drivers do what they see fit.
1986     */
1987    if (blk_fs_request(req))
1988        req->errors = 0;
1989
1990    if (error && (blk_fs_request(req) && !(req->cmd_flags & REQ_QUIET))) {
1991        printk(KERN_ERR "end_request: I/O error, dev %s, sector %llu\n",
1992                req->rq_disk ? req->rq_disk->disk_name : "?",
1993                (unsigned long long)blk_rq_pos(req));
1994    }
1995
1996    blk_account_io_completion(req, nr_bytes);
1997
1998    total_bytes = bio_nbytes = 0;
1999    while ((bio = req->bio) != NULL) {
2000        int nbytes;
2001
2002        if (nr_bytes >= bio->bi_size) {
2003            req->bio = bio->bi_next;
2004            nbytes = bio->bi_size;
2005            req_bio_endio(req, bio, nbytes, error);
2006            next_idx = 0;
2007            bio_nbytes = 0;
2008        } else {
2009            int idx = bio->bi_idx + next_idx;
2010
2011            if (unlikely(idx >= bio->bi_vcnt)) {
2012                blk_dump_rq_flags(req, "__end_that");
2013                printk(KERN_ERR "%s: bio idx %d >= vcnt %d\n",
2014                       __func__, idx, bio->bi_vcnt);
2015                break;
2016            }
2017
2018            nbytes = bio_iovec_idx(bio, idx)->bv_len;
2019            BIO_BUG_ON(nbytes > bio->bi_size);
2020
2021            /*
2022             * not a complete bvec done
2023             */
2024            if (unlikely(nbytes > nr_bytes)) {
2025                bio_nbytes += nr_bytes;
2026                total_bytes += nr_bytes;
2027                break;
2028            }
2029
2030            /*
2031             * advance to the next vector
2032             */
2033            next_idx++;
2034            bio_nbytes += nbytes;
2035        }
2036
2037        total_bytes += nbytes;
2038        nr_bytes -= nbytes;
2039
2040        bio = req->bio;
2041        if (bio) {
2042            /*
2043             * end more in this run, or just return 'not-done'
2044             */
2045            if (unlikely(nr_bytes <= 0))
2046                break;
2047        }
2048    }
2049
2050    /*
2051     * completely done
2052     */
2053    if (!req->bio) {
2054        /*
2055         * Reset counters so that the request stacking driver
2056         * can find how many bytes remain in the request
2057         * later.
2058         */
2059        req->__data_len = 0;
2060        return false;
2061    }
2062
2063    /*
2064     * if the request wasn't completed, update state
2065     */
2066    if (bio_nbytes) {
2067        req_bio_endio(req, bio, bio_nbytes, error);
2068        bio->bi_idx += next_idx;
2069        bio_iovec(bio)->bv_offset += nr_bytes;
2070        bio_iovec(bio)->bv_len -= nr_bytes;
2071    }
2072
2073    req->__data_len -= total_bytes;
2074    req->buffer = bio_data(req->bio);
2075
2076    /* update sector only for requests with clear definition of sector */
2077    if (blk_fs_request(req) || blk_discard_rq(req))
2078        req->__sector += total_bytes >> 9;
2079
2080    /* mixed attributes always follow the first bio */
2081    if (req->cmd_flags & REQ_MIXED_MERGE) {
2082        req->cmd_flags &= ~REQ_FAILFAST_MASK;
2083        req->cmd_flags |= req->bio->bi_rw & REQ_FAILFAST_MASK;
2084    }
2085
2086    /*
2087     * If total number of sectors is less than the first segment
2088     * size, something has gone terribly wrong.
2089     */
2090    if (blk_rq_bytes(req) < blk_rq_cur_bytes(req)) {
2091        printk(KERN_ERR "blk: request botched\n");
2092        req->__data_len = blk_rq_cur_bytes(req);
2093    }
2094
2095    /* recalculate the number of segments */
2096    blk_recalc_rq_segments(req);
2097
2098    return true;
2099}
2100EXPORT_SYMBOL_GPL(blk_update_request);
2101
2102static bool blk_update_bidi_request(struct request *rq, int error,
2103                    unsigned int nr_bytes,
2104                    unsigned int bidi_bytes)
2105{
2106    if (blk_update_request(rq, error, nr_bytes))
2107        return true;
2108
2109    /* Bidi request must be completed as a whole */
2110    if (unlikely(blk_bidi_rq(rq)) &&
2111        blk_update_request(rq->next_rq, error, bidi_bytes))
2112        return true;
2113
2114    add_disk_randomness(rq->rq_disk);
2115
2116    return false;
2117}
2118
2119/*
2120 * queue lock must be held
2121 */
2122static void blk_finish_request(struct request *req, int error)
2123{
2124    if (blk_rq_tagged(req))
2125        blk_queue_end_tag(req->q, req);
2126
2127    BUG_ON(blk_queued_rq(req));
2128
2129    if (unlikely(laptop_mode) && blk_fs_request(req))
2130        laptop_io_completion(&req->q->backing_dev_info);
2131
2132    blk_delete_timer(req);
2133
2134    blk_account_io_done(req);
2135
2136    if (req->end_io)
2137        req->end_io(req, error);
2138    else {
2139        if (blk_bidi_rq(req))
2140            __blk_put_request(req->next_rq->q, req->next_rq);
2141
2142        __blk_put_request(req->q, req);
2143    }
2144}
2145
2146/**
2147 * blk_end_bidi_request - Complete a bidi request
2148 * @rq: the request to complete
2149 * @error: %0 for success, < %0 for error
2150 * @nr_bytes: number of bytes to complete @rq
2151 * @bidi_bytes: number of bytes to complete @rq->next_rq
2152 *
2153 * Description:
2154 * Ends I/O on a number of bytes attached to @rq and @rq->next_rq.
2155 * Drivers that supports bidi can safely call this member for any
2156 * type of request, bidi or uni. In the later case @bidi_bytes is
2157 * just ignored.
2158 *
2159 * Return:
2160 * %false - we are done with this request
2161 * %true - still buffers pending for this request
2162 **/
2163static bool blk_end_bidi_request(struct request *rq, int error,
2164                 unsigned int nr_bytes, unsigned int bidi_bytes)
2165{
2166    struct request_queue *q = rq->q;
2167    unsigned long flags;
2168
2169    if (blk_update_bidi_request(rq, error, nr_bytes, bidi_bytes))
2170        return true;
2171
2172    spin_lock_irqsave(q->queue_lock, flags);
2173    blk_finish_request(rq, error);
2174    spin_unlock_irqrestore(q->queue_lock, flags);
2175
2176    return false;
2177}
2178
2179/**
2180 * __blk_end_bidi_request - Complete a bidi request with queue lock held
2181 * @rq: the request to complete
2182 * @error: %0 for success, < %0 for error
2183 * @nr_bytes: number of bytes to complete @rq
2184 * @bidi_bytes: number of bytes to complete @rq->next_rq
2185 *
2186 * Description:
2187 * Identical to blk_end_bidi_request() except that queue lock is
2188 * assumed to be locked on entry and remains so on return.
2189 *
2190 * Return:
2191 * %false - we are done with this request
2192 * %true - still buffers pending for this request
2193 **/
2194static bool __blk_end_bidi_request(struct request *rq, int error,
2195                   unsigned int nr_bytes, unsigned int bidi_bytes)
2196{
2197    if (blk_update_bidi_request(rq, error, nr_bytes, bidi_bytes))
2198        return true;
2199
2200    blk_finish_request(rq, error);
2201
2202    return false;
2203}
2204
2205/**
2206 * blk_end_request - Helper function for drivers to complete the request.
2207 * @rq: the request being processed
2208 * @error: %0 for success, < %0 for error
2209 * @nr_bytes: number of bytes to complete
2210 *
2211 * Description:
2212 * Ends I/O on a number of bytes attached to @rq.
2213 * If @rq has leftover, sets it up for the next range of segments.
2214 *
2215 * Return:
2216 * %false - we are done with this request
2217 * %true - still buffers pending for this request
2218 **/
2219bool blk_end_request(struct request *rq, int error, unsigned int nr_bytes)
2220{
2221    return blk_end_bidi_request(rq, error, nr_bytes, 0);
2222}
2223EXPORT_SYMBOL(blk_end_request);
2224
2225/**
2226 * blk_end_request_all - Helper function for drives to finish the request.
2227 * @rq: the request to finish
2228 * @error: %0 for success, < %0 for error
2229 *
2230 * Description:
2231 * Completely finish @rq.
2232 */
2233void blk_end_request_all(struct request *rq, int error)
2234{
2235    bool pending;
2236    unsigned int bidi_bytes = 0;
2237
2238    if (unlikely(blk_bidi_rq(rq)))
2239        bidi_bytes = blk_rq_bytes(rq->next_rq);
2240
2241    pending = blk_end_bidi_request(rq, error, blk_rq_bytes(rq), bidi_bytes);
2242    BUG_ON(pending);
2243}
2244EXPORT_SYMBOL(blk_end_request_all);
2245
2246/**
2247 * blk_end_request_cur - Helper function to finish the current request chunk.
2248 * @rq: the request to finish the current chunk for
2249 * @error: %0 for success, < %0 for error
2250 *
2251 * Description:
2252 * Complete the current consecutively mapped chunk from @rq.
2253 *
2254 * Return:
2255 * %false - we are done with this request
2256 * %true - still buffers pending for this request
2257 */
2258bool blk_end_request_cur(struct request *rq, int error)
2259{
2260    return blk_end_request(rq, error, blk_rq_cur_bytes(rq));
2261}
2262EXPORT_SYMBOL(blk_end_request_cur);
2263
2264/**
2265 * blk_end_request_err - Finish a request till the next failure boundary.
2266 * @rq: the request to finish till the next failure boundary for
2267 * @error: must be negative errno
2268 *
2269 * Description:
2270 * Complete @rq till the next failure boundary.
2271 *
2272 * Return:
2273 * %false - we are done with this request
2274 * %true - still buffers pending for this request
2275 */
2276bool blk_end_request_err(struct request *rq, int error)
2277{
2278    WARN_ON(error >= 0);
2279    return blk_end_request(rq, error, blk_rq_err_bytes(rq));
2280}
2281EXPORT_SYMBOL_GPL(blk_end_request_err);
2282
2283/**
2284 * __blk_end_request - Helper function for drivers to complete the request.
2285 * @rq: the request being processed
2286 * @error: %0 for success, < %0 for error
2287 * @nr_bytes: number of bytes to complete
2288 *
2289 * Description:
2290 * Must be called with queue lock held unlike blk_end_request().
2291 *
2292 * Return:
2293 * %false - we are done with this request
2294 * %true - still buffers pending for this request
2295 **/
2296bool __blk_end_request(struct request *rq, int error, unsigned int nr_bytes)
2297{
2298    return __blk_end_bidi_request(rq, error, nr_bytes, 0);
2299}
2300EXPORT_SYMBOL(__blk_end_request);
2301
2302/**
2303 * __blk_end_request_all - Helper function for drives to finish the request.
2304 * @rq: the request to finish
2305 * @error: %0 for success, < %0 for error
2306 *
2307 * Description:
2308 * Completely finish @rq. Must be called with queue lock held.
2309 */
2310void __blk_end_request_all(struct request *rq, int error)
2311{
2312    bool pending;
2313    unsigned int bidi_bytes = 0;
2314
2315    if (unlikely(blk_bidi_rq(rq)))
2316        bidi_bytes = blk_rq_bytes(rq->next_rq);
2317
2318    pending = __blk_end_bidi_request(rq, error, blk_rq_bytes(rq), bidi_bytes);
2319    BUG_ON(pending);
2320}
2321EXPORT_SYMBOL(__blk_end_request_all);
2322
2323/**
2324 * __blk_end_request_cur - Helper function to finish the current request chunk.
2325 * @rq: the request to finish the current chunk for
2326 * @error: %0 for success, < %0 for error
2327 *
2328 * Description:
2329 * Complete the current consecutively mapped chunk from @rq. Must
2330 * be called with queue lock held.
2331 *
2332 * Return:
2333 * %false - we are done with this request
2334 * %true - still buffers pending for this request
2335 */
2336bool __blk_end_request_cur(struct request *rq, int error)
2337{
2338    return __blk_end_request(rq, error, blk_rq_cur_bytes(rq));
2339}
2340EXPORT_SYMBOL(__blk_end_request_cur);
2341
2342/**
2343 * __blk_end_request_err - Finish a request till the next failure boundary.
2344 * @rq: the request to finish till the next failure boundary for
2345 * @error: must be negative errno
2346 *
2347 * Description:
2348 * Complete @rq till the next failure boundary. Must be called
2349 * with queue lock held.
2350 *
2351 * Return:
2352 * %false - we are done with this request
2353 * %true - still buffers pending for this request
2354 */
2355bool __blk_end_request_err(struct request *rq, int error)
2356{
2357    WARN_ON(error >= 0);
2358    return __blk_end_request(rq, error, blk_rq_err_bytes(rq));
2359}
2360EXPORT_SYMBOL_GPL(__blk_end_request_err);
2361
2362void blk_rq_bio_prep(struct request_queue *q, struct request *rq,
2363             struct bio *bio)
2364{
2365    /* Bit 0 (R/W) is identical in rq->cmd_flags and bio->bi_rw */
2366    rq->cmd_flags |= bio->bi_rw & REQ_RW;
2367
2368    if (bio_has_data(bio)) {
2369        rq->nr_phys_segments = bio_phys_segments(q, bio);
2370        rq->buffer = bio_data(bio);
2371    }
2372    rq->__data_len = bio->bi_size;
2373    rq->bio = rq->biotail = bio;
2374
2375    if (bio->bi_bdev)
2376        rq->rq_disk = bio->bi_bdev->bd_disk;
2377}
2378
2379#if ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE
2380/**
2381 * rq_flush_dcache_pages - Helper function to flush all pages in a request
2382 * @rq: the request to be flushed
2383 *
2384 * Description:
2385 * Flush all pages in @rq.
2386 */
2387void rq_flush_dcache_pages(struct request *rq)
2388{
2389    struct req_iterator iter;
2390    struct bio_vec *bvec;
2391
2392    rq_for_each_segment(bvec, rq, iter)
2393        flush_dcache_page(bvec->bv_page);
2394}
2395EXPORT_SYMBOL_GPL(rq_flush_dcache_pages);
2396#endif
2397
2398/**
2399 * blk_lld_busy - Check if underlying low-level drivers of a device are busy
2400 * @q : the queue of the device being checked
2401 *
2402 * Description:
2403 * Check if underlying low-level drivers of a device are busy.
2404 * If the drivers want to export their busy state, they must set own
2405 * exporting function using blk_queue_lld_busy() first.
2406 *
2407 * Basically, this function is used only by request stacking drivers
2408 * to stop dispatching requests to underlying devices when underlying
2409 * devices are busy. This behavior helps more I/O merging on the queue
2410 * of the request stacking driver and prevents I/O throughput regression
2411 * on burst I/O load.
2412 *
2413 * Return:
2414 * 0 - Not busy (The request stacking driver should dispatch request)
2415 * 1 - Busy (The request stacking driver should stop dispatching request)
2416 */
2417int blk_lld_busy(struct request_queue *q)
2418{
2419    if (q->lld_busy_fn)
2420        return q->lld_busy_fn(q);
2421
2422    return 0;
2423}
2424EXPORT_SYMBOL_GPL(blk_lld_busy);
2425
2426/**
2427 * blk_rq_unprep_clone - Helper function to free all bios in a cloned request
2428 * @rq: the clone request to be cleaned up
2429 *
2430 * Description:
2431 * Free all bios in @rq for a cloned request.
2432 */
2433void blk_rq_unprep_clone(struct request *rq)
2434{
2435    struct bio *bio;
2436
2437    while ((bio = rq->bio) != NULL) {
2438        rq->bio = bio->bi_next;
2439
2440        bio_put(bio);
2441    }
2442}
2443EXPORT_SYMBOL_GPL(blk_rq_unprep_clone);
2444
2445/*
2446 * Copy attributes of the original request to the clone request.
2447 * The actual data parts (e.g. ->cmd, ->buffer, ->sense) are not copied.
2448 */
2449static void __blk_rq_prep_clone(struct request *dst, struct request *src)
2450{
2451    dst->cpu = src->cpu;
2452    dst->cmd_flags = (rq_data_dir(src) | REQ_NOMERGE);
2453    dst->cmd_type = src->cmd_type;
2454    dst->__sector = blk_rq_pos(src);
2455    dst->__data_len = blk_rq_bytes(src);
2456    dst->nr_phys_segments = src->nr_phys_segments;
2457    dst->ioprio = src->ioprio;
2458    dst->extra_len = src->extra_len;
2459}
2460
2461/**
2462 * blk_rq_prep_clone - Helper function to setup clone request
2463 * @rq: the request to be setup
2464 * @rq_src: original request to be cloned
2465 * @bs: bio_set that bios for clone are allocated from
2466 * @gfp_mask: memory allocation mask for bio
2467 * @bio_ctr: setup function to be called for each clone bio.
2468 * Returns %0 for success, non %0 for failure.
2469 * @data: private data to be passed to @bio_ctr
2470 *
2471 * Description:
2472 * Clones bios in @rq_src to @rq, and copies attributes of @rq_src to @rq.
2473 * The actual data parts of @rq_src (e.g. ->cmd, ->buffer, ->sense)
2474 * are not copied, and copying such parts is the caller's responsibility.
2475 * Also, pages which the original bios are pointing to are not copied
2476 * and the cloned bios just point same pages.
2477 * So cloned bios must be completed before original bios, which means
2478 * the caller must complete @rq before @rq_src.
2479 */
2480int blk_rq_prep_clone(struct request *rq, struct request *rq_src,
2481              struct bio_set *bs, gfp_t gfp_mask,
2482              int (*bio_ctr)(struct bio *, struct bio *, void *),
2483              void *data)
2484{
2485    struct bio *bio, *bio_src;
2486
2487    if (!bs)
2488        bs = fs_bio_set;
2489
2490    blk_rq_init(NULL, rq);
2491
2492    __rq_for_each_bio(bio_src, rq_src) {
2493        bio = bio_alloc_bioset(gfp_mask, bio_src->bi_max_vecs, bs);
2494        if (!bio)
2495            goto free_and_out;
2496
2497        __bio_clone(bio, bio_src);
2498
2499        if (bio_integrity(bio_src) &&
2500            bio_integrity_clone(bio, bio_src, gfp_mask, bs))
2501            goto free_and_out;
2502
2503        if (bio_ctr && bio_ctr(bio, bio_src, data))
2504            goto free_and_out;
2505
2506        if (rq->bio) {
2507            rq->biotail->bi_next = bio;
2508            rq->biotail = bio;
2509        } else
2510            rq->bio = rq->biotail = bio;
2511    }
2512
2513    __blk_rq_prep_clone(rq, rq_src);
2514
2515    return 0;
2516
2517free_and_out:
2518    if (bio)
2519        bio_free(bio, bs);
2520    blk_rq_unprep_clone(rq);
2521
2522    return -ENOMEM;
2523}
2524EXPORT_SYMBOL_GPL(blk_rq_prep_clone);
2525
2526int kblockd_schedule_work(struct request_queue *q, struct work_struct *work)
2527{
2528    return queue_work(kblockd_workqueue, work);
2529}
2530EXPORT_SYMBOL(kblockd_schedule_work);
2531
2532int __init blk_dev_init(void)
2533{
2534    BUILD_BUG_ON(__REQ_NR_BITS > 8 *
2535            sizeof(((struct request *)0)->cmd_flags));
2536
2537    kblockd_workqueue = create_workqueue("kblockd");
2538    if (!kblockd_workqueue)
2539        panic("Failed to create kblockd\n");
2540
2541    request_cachep = kmem_cache_create("blkdev_requests",
2542            sizeof(struct request), 0, SLAB_PANIC, NULL);
2543
2544    blk_requestq_cachep = kmem_cache_create("blkdev_queue",
2545            sizeof(struct request_queue), 0, SLAB_PANIC, NULL);
2546
2547    return 0;
2548}
2549

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