linux/block/blk-core.c
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   1/*
   2 * Copyright (C) 1991, 1992 Linus Torvalds
   3 * Copyright (C) 1994,      Karl Keyte: Added support for disk statistics
   4 * Elevator latency, (C) 2000  Andrea Arcangeli <andrea@suse.de> SuSE
   5 * Queue request tables / lock, selectable elevator, Jens Axboe <axboe@suse.de>
   6 * kernel-doc documentation started by NeilBrown <neilb@cse.unsw.edu.au>
   7 *      -  July2000
   8 * bio rewrite, highmem i/o, etc, Jens Axboe <axboe@suse.de> - may 2001
   9 */
  10
  11/*
  12 * This handles all read/write requests to block devices
  13 */
  14#include <linux/kernel.h>
  15#include <linux/module.h>
  16#include <linux/backing-dev.h>
  17#include <linux/bio.h>
  18#include <linux/blkdev.h>
  19#include <linux/highmem.h>
  20#include <linux/mm.h>
  21#include <linux/kernel_stat.h>
  22#include <linux/string.h>
  23#include <linux/init.h>
  24#include <linux/completion.h>
  25#include <linux/slab.h>
  26#include <linux/swap.h>
  27#include <linux/writeback.h>
  28#include <linux/task_io_accounting_ops.h>
  29#include <linux/fault-inject.h>
  30#include <linux/list_sort.h>
  31
  32#define CREATE_TRACE_POINTS
  33#include <trace/events/block.h>
  34
  35#include "blk.h"
  36
  37EXPORT_TRACEPOINT_SYMBOL_GPL(block_bio_remap);
  38EXPORT_TRACEPOINT_SYMBOL_GPL(block_rq_remap);
  39EXPORT_TRACEPOINT_SYMBOL_GPL(block_bio_complete);
  40
  41static int __make_request(struct request_queue *q, struct bio *bio);
  42
  43/*
  44 * For the allocated request tables
  45 */
  46static struct kmem_cache *request_cachep;
  47
  48/*
  49 * For queue allocation
  50 */
  51struct kmem_cache *blk_requestq_cachep;
  52
  53/*
  54 * Controlling structure to kblockd
  55 */
  56static struct workqueue_struct *kblockd_workqueue;
  57
  58static void drive_stat_acct(struct request *rq, int new_io)
  59{
  60        struct hd_struct *part;
  61        int rw = rq_data_dir(rq);
  62        int cpu;
  63
  64        if (!blk_do_io_stat(rq))
  65                return;
  66
  67        cpu = part_stat_lock();
  68
  69        if (!new_io) {
  70                part = rq->part;
  71                part_stat_inc(cpu, part, merges[rw]);
  72        } else {
  73                part = disk_map_sector_rcu(rq->rq_disk, blk_rq_pos(rq));
  74                if (!hd_struct_try_get(part)) {
  75                        /*
  76                         * The partition is already being removed,
  77                         * the request will be accounted on the disk only
  78                         *
  79                         * We take a reference on disk->part0 although that
  80                         * partition will never be deleted, so we can treat
  81                         * it as any other partition.
  82                         */
  83                        part = &rq->rq_disk->part0;
  84                        hd_struct_get(part);
  85                }
  86                part_round_stats(cpu, part);
  87                part_inc_in_flight(part, rw);
  88                rq->part = part;
  89        }
  90
  91        part_stat_unlock();
  92}
  93
  94void blk_queue_congestion_threshold(struct request_queue *q)
  95{
  96        int nr;
  97
  98        nr = q->nr_requests - (q->nr_requests / 8) + 1;
  99        if (nr > q->nr_requests)
 100                nr = q->nr_requests;
 101        q->nr_congestion_on = nr;
 102
 103        nr = q->nr_requests - (q->nr_requests / 8) - (q->nr_requests / 16) - 1;
 104        if (nr < 1)
 105                nr = 1;
 106        q->nr_congestion_off = nr;
 107}
 108
 109/**
 110 * blk_get_backing_dev_info - get the address of a queue's backing_dev_info
 111 * @bdev:       device
 112 *
 113 * Locates the passed device's request queue and returns the address of its
 114 * backing_dev_info
 115 *
 116 * Will return NULL if the request queue cannot be located.
 117 */
 118struct backing_dev_info *blk_get_backing_dev_info(struct block_device *bdev)
 119{
 120        struct backing_dev_info *ret = NULL;
 121        struct request_queue *q = bdev_get_queue(bdev);
 122
 123        if (q)
 124                ret = &q->backing_dev_info;
 125        return ret;
 126}
 127EXPORT_SYMBOL(blk_get_backing_dev_info);
 128
 129void blk_rq_init(struct request_queue *q, struct request *rq)
 130{
 131        memset(rq, 0, sizeof(*rq));
 132
 133        INIT_LIST_HEAD(&rq->queuelist);
 134        INIT_LIST_HEAD(&rq->timeout_list);
 135        rq->cpu = -1;
 136        rq->q = q;
 137        rq->__sector = (sector_t) -1;
 138        INIT_HLIST_NODE(&rq->hash);
 139        RB_CLEAR_NODE(&rq->rb_node);
 140        rq->cmd = rq->__cmd;
 141        rq->cmd_len = BLK_MAX_CDB;
 142        rq->tag = -1;
 143        rq->ref_count = 1;
 144        rq->start_time = jiffies;
 145        set_start_time_ns(rq);
 146        rq->part = NULL;
 147}
 148EXPORT_SYMBOL(blk_rq_init);
 149
 150static void req_bio_endio(struct request *rq, struct bio *bio,
 151                          unsigned int nbytes, int error)
 152{
 153        if (error)
 154                clear_bit(BIO_UPTODATE, &bio->bi_flags);
 155        else if (!test_bit(BIO_UPTODATE, &bio->bi_flags))
 156                error = -EIO;
 157
 158        if (unlikely(nbytes > bio->bi_size)) {
 159                printk(KERN_ERR "%s: want %u bytes done, %u left\n",
 160                       __func__, nbytes, bio->bi_size);
 161                nbytes = bio->bi_size;
 162        }
 163
 164        if (unlikely(rq->cmd_flags & REQ_QUIET))
 165                set_bit(BIO_QUIET, &bio->bi_flags);
 166
 167        bio->bi_size -= nbytes;
 168        bio->bi_sector += (nbytes >> 9);
 169
 170        if (bio_integrity(bio))
 171                bio_integrity_advance(bio, nbytes);
 172
 173        /* don't actually finish bio if it's part of flush sequence */
 174        if (bio->bi_size == 0 && !(rq->cmd_flags & REQ_FLUSH_SEQ))
 175                bio_endio(bio, error);
 176}
 177
 178void blk_dump_rq_flags(struct request *rq, char *msg)
 179{
 180        int bit;
 181
 182        printk(KERN_INFO "%s: dev %s: type=%x, flags=%x\n", msg,
 183                rq->rq_disk ? rq->rq_disk->disk_name : "?", rq->cmd_type,
 184                rq->cmd_flags);
 185
 186        printk(KERN_INFO "  sector %llu, nr/cnr %u/%u\n",
 187               (unsigned long long)blk_rq_pos(rq),
 188               blk_rq_sectors(rq), blk_rq_cur_sectors(rq));
 189        printk(KERN_INFO "  bio %p, biotail %p, buffer %p, len %u\n",
 190               rq->bio, rq->biotail, rq->buffer, blk_rq_bytes(rq));
 191
 192        if (rq->cmd_type == REQ_TYPE_BLOCK_PC) {
 193                printk(KERN_INFO "  cdb: ");
 194                for (bit = 0; bit < BLK_MAX_CDB; bit++)
 195                        printk("%02x ", rq->cmd[bit]);
 196                printk("\n");
 197        }
 198}
 199EXPORT_SYMBOL(blk_dump_rq_flags);
 200
 201static void blk_delay_work(struct work_struct *work)
 202{
 203        struct request_queue *q;
 204
 205        q = container_of(work, struct request_queue, delay_work.work);
 206        spin_lock_irq(q->queue_lock);
 207        __blk_run_queue(q);
 208        spin_unlock_irq(q->queue_lock);
 209}
 210
 211/**
 212 * blk_delay_queue - restart queueing after defined interval
 213 * @q:          The &struct request_queue in question
 214 * @msecs:      Delay in msecs
 215 *
 216 * Description:
 217 *   Sometimes queueing needs to be postponed for a little while, to allow
 218 *   resources to come back. This function will make sure that queueing is
 219 *   restarted around the specified time.
 220 */
 221void blk_delay_queue(struct request_queue *q, unsigned long msecs)
 222{
 223        queue_delayed_work(kblockd_workqueue, &q->delay_work,
 224                                msecs_to_jiffies(msecs));
 225}
 226EXPORT_SYMBOL(blk_delay_queue);
 227
 228/**
 229 * blk_start_queue - restart a previously stopped queue
 230 * @q:    The &struct request_queue in question
 231 *
 232 * Description:
 233 *   blk_start_queue() will clear the stop flag on the queue, and call
 234 *   the request_fn for the queue if it was in a stopped state when
 235 *   entered. Also see blk_stop_queue(). Queue lock must be held.
 236 **/
 237void blk_start_queue(struct request_queue *q)
 238{
 239        WARN_ON(!irqs_disabled());
 240
 241        queue_flag_clear(QUEUE_FLAG_STOPPED, q);
 242        __blk_run_queue(q);
 243}
 244EXPORT_SYMBOL(blk_start_queue);
 245
 246/**
 247 * blk_stop_queue - stop a queue
 248 * @q:    The &struct request_queue in question
 249 *
 250 * Description:
 251 *   The Linux block layer assumes that a block driver will consume all
 252 *   entries on the request queue when the request_fn strategy is called.
 253 *   Often this will not happen, because of hardware limitations (queue
 254 *   depth settings). If a device driver gets a 'queue full' response,
 255 *   or if it simply chooses not to queue more I/O at one point, it can
 256 *   call this function to prevent the request_fn from being called until
 257 *   the driver has signalled it's ready to go again. This happens by calling
 258 *   blk_start_queue() to restart queue operations. Queue lock must be held.
 259 **/
 260void blk_stop_queue(struct request_queue *q)
 261{
 262        __cancel_delayed_work(&q->delay_work);
 263        queue_flag_set(QUEUE_FLAG_STOPPED, q);
 264}
 265EXPORT_SYMBOL(blk_stop_queue);
 266
 267/**
 268 * blk_sync_queue - cancel any pending callbacks on a queue
 269 * @q: the queue
 270 *
 271 * Description:
 272 *     The block layer may perform asynchronous callback activity
 273 *     on a queue, such as calling the unplug function after a timeout.
 274 *     A block device may call blk_sync_queue to ensure that any
 275 *     such activity is cancelled, thus allowing it to release resources
 276 *     that the callbacks might use. The caller must already have made sure
 277 *     that its ->make_request_fn will not re-add plugging prior to calling
 278 *     this function.
 279 *
 280 *     This function does not cancel any asynchronous activity arising
 281 *     out of elevator or throttling code. That would require elevaotor_exit()
 282 *     and blk_throtl_exit() to be called with queue lock initialized.
 283 *
 284 */
 285void blk_sync_queue(struct request_queue *q)
 286{
 287        del_timer_sync(&q->timeout);
 288        cancel_delayed_work_sync(&q->delay_work);
 289}
 290EXPORT_SYMBOL(blk_sync_queue);
 291
 292/**
 293 * __blk_run_queue - run a single device queue
 294 * @q:  The queue to run
 295 *
 296 * Description:
 297 *    See @blk_run_queue. This variant must be called with the queue lock
 298 *    held and interrupts disabled.
 299 */
 300void __blk_run_queue(struct request_queue *q)
 301{
 302        if (unlikely(blk_queue_stopped(q)))
 303                return;
 304
 305        q->request_fn(q);
 306}
 307EXPORT_SYMBOL(__blk_run_queue);
 308
 309/**
 310 * blk_run_queue_async - run a single device queue in workqueue context
 311 * @q:  The queue to run
 312 *
 313 * Description:
 314 *    Tells kblockd to perform the equivalent of @blk_run_queue on behalf
 315 *    of us.
 316 */
 317void blk_run_queue_async(struct request_queue *q)
 318{
 319        if (likely(!blk_queue_stopped(q))) {
 320                __cancel_delayed_work(&q->delay_work);
 321                queue_delayed_work(kblockd_workqueue, &q->delay_work, 0);
 322        }
 323}
 324EXPORT_SYMBOL(blk_run_queue_async);
 325
 326/**
 327 * blk_run_queue - run a single device queue
 328 * @q: The queue to run
 329 *
 330 * Description:
 331 *    Invoke request handling on this queue, if it has pending work to do.
 332 *    May be used to restart queueing when a request has completed.
 333 */
 334void blk_run_queue(struct request_queue *q)
 335{
 336        unsigned long flags;
 337
 338        spin_lock_irqsave(q->queue_lock, flags);
 339        __blk_run_queue(q);
 340        spin_unlock_irqrestore(q->queue_lock, flags);
 341}
 342EXPORT_SYMBOL(blk_run_queue);
 343
 344void blk_put_queue(struct request_queue *q)
 345{
 346        kobject_put(&q->kobj);
 347}
 348
 349/*
 350 * Note: If a driver supplied the queue lock, it should not zap that lock
 351 * unexpectedly as some queue cleanup components like elevator_exit() and
 352 * blk_throtl_exit() need queue lock.
 353 */
 354void blk_cleanup_queue(struct request_queue *q)
 355{
 356        /*
 357         * We know we have process context here, so we can be a little
 358         * cautious and ensure that pending block actions on this device
 359         * are done before moving on. Going into this function, we should
 360         * not have processes doing IO to this device.
 361         */
 362        blk_sync_queue(q);
 363
 364        del_timer_sync(&q->backing_dev_info.laptop_mode_wb_timer);
 365        mutex_lock(&q->sysfs_lock);
 366        queue_flag_set_unlocked(QUEUE_FLAG_DEAD, q);
 367        mutex_unlock(&q->sysfs_lock);
 368
 369        if (q->elevator)
 370                elevator_exit(q->elevator);
 371
 372        blk_throtl_exit(q);
 373
 374        blk_put_queue(q);
 375}
 376EXPORT_SYMBOL(blk_cleanup_queue);
 377
 378static int blk_init_free_list(struct request_queue *q)
 379{
 380        struct request_list *rl = &q->rq;
 381
 382        if (unlikely(rl->rq_pool))
 383                return 0;
 384
 385        rl->count[BLK_RW_SYNC] = rl->count[BLK_RW_ASYNC] = 0;
 386        rl->starved[BLK_RW_SYNC] = rl->starved[BLK_RW_ASYNC] = 0;
 387        rl->elvpriv = 0;
 388        init_waitqueue_head(&rl->wait[BLK_RW_SYNC]);
 389        init_waitqueue_head(&rl->wait[BLK_RW_ASYNC]);
 390
 391        rl->rq_pool = mempool_create_node(BLKDEV_MIN_RQ, mempool_alloc_slab,
 392                                mempool_free_slab, request_cachep, q->node);
 393
 394        if (!rl->rq_pool)
 395                return -ENOMEM;
 396
 397        return 0;
 398}
 399
 400struct request_queue *blk_alloc_queue(gfp_t gfp_mask)
 401{
 402        return blk_alloc_queue_node(gfp_mask, -1);
 403}
 404EXPORT_SYMBOL(blk_alloc_queue);
 405
 406struct request_queue *blk_alloc_queue_node(gfp_t gfp_mask, int node_id)
 407{
 408        struct request_queue *q;
 409        int err;
 410
 411        q = kmem_cache_alloc_node(blk_requestq_cachep,
 412                                gfp_mask | __GFP_ZERO, node_id);
 413        if (!q)
 414                return NULL;
 415
 416        q->backing_dev_info.ra_pages =
 417                        (VM_MAX_READAHEAD * 1024) / PAGE_CACHE_SIZE;
 418        q->backing_dev_info.state = 0;
 419        q->backing_dev_info.capabilities = BDI_CAP_MAP_COPY;
 420        q->backing_dev_info.name = "block";
 421
 422        err = bdi_init(&q->backing_dev_info);
 423        if (err) {
 424                kmem_cache_free(blk_requestq_cachep, q);
 425                return NULL;
 426        }
 427
 428        if (blk_throtl_init(q)) {
 429                kmem_cache_free(blk_requestq_cachep, q);
 430                return NULL;
 431        }
 432
 433        setup_timer(&q->backing_dev_info.laptop_mode_wb_timer,
 434                    laptop_mode_timer_fn, (unsigned long) q);
 435        setup_timer(&q->timeout, blk_rq_timed_out_timer, (unsigned long) q);
 436        INIT_LIST_HEAD(&q->timeout_list);
 437        INIT_LIST_HEAD(&q->flush_queue[0]);
 438        INIT_LIST_HEAD(&q->flush_queue[1]);
 439        INIT_LIST_HEAD(&q->flush_data_in_flight);
 440        INIT_DELAYED_WORK(&q->delay_work, blk_delay_work);
 441
 442        kobject_init(&q->kobj, &blk_queue_ktype);
 443
 444        mutex_init(&q->sysfs_lock);
 445        spin_lock_init(&q->__queue_lock);
 446
 447        /*
 448         * By default initialize queue_lock to internal lock and driver can
 449         * override it later if need be.
 450         */
 451        q->queue_lock = &q->__queue_lock;
 452
 453        return q;
 454}
 455EXPORT_SYMBOL(blk_alloc_queue_node);
 456
 457/**
 458 * blk_init_queue  - prepare a request queue for use with a block device
 459 * @rfn:  The function to be called to process requests that have been
 460 *        placed on the queue.
 461 * @lock: Request queue spin lock
 462 *
 463 * Description:
 464 *    If a block device wishes to use the standard request handling procedures,
 465 *    which sorts requests and coalesces adjacent requests, then it must
 466 *    call blk_init_queue().  The function @rfn will be called when there
 467 *    are requests on the queue that need to be processed.  If the device
 468 *    supports plugging, then @rfn may not be called immediately when requests
 469 *    are available on the queue, but may be called at some time later instead.
 470 *    Plugged queues are generally unplugged when a buffer belonging to one
 471 *    of the requests on the queue is needed, or due to memory pressure.
 472 *
 473 *    @rfn is not required, or even expected, to remove all requests off the
 474 *    queue, but only as many as it can handle at a time.  If it does leave
 475 *    requests on the queue, it is responsible for arranging that the requests
 476 *    get dealt with eventually.
 477 *
 478 *    The queue spin lock must be held while manipulating the requests on the
 479 *    request queue; this lock will be taken also from interrupt context, so irq
 480 *    disabling is needed for it.
 481 *
 482 *    Function returns a pointer to the initialized request queue, or %NULL if
 483 *    it didn't succeed.
 484 *
 485 * Note:
 486 *    blk_init_queue() must be paired with a blk_cleanup_queue() call
 487 *    when the block device is deactivated (such as at module unload).
 488 **/
 489
 490struct request_queue *blk_init_queue(request_fn_proc *rfn, spinlock_t *lock)
 491{
 492        return blk_init_queue_node(rfn, lock, -1);
 493}
 494EXPORT_SYMBOL(blk_init_queue);
 495
 496struct request_queue *
 497blk_init_queue_node(request_fn_proc *rfn, spinlock_t *lock, int node_id)
 498{
 499        struct request_queue *uninit_q, *q;
 500
 501        uninit_q = blk_alloc_queue_node(GFP_KERNEL, node_id);
 502        if (!uninit_q)
 503                return NULL;
 504
 505        q = blk_init_allocated_queue_node(uninit_q, rfn, lock, node_id);
 506        if (!q)
 507                blk_cleanup_queue(uninit_q);
 508
 509        return q;
 510}
 511EXPORT_SYMBOL(blk_init_queue_node);
 512
 513struct request_queue *
 514blk_init_allocated_queue(struct request_queue *q, request_fn_proc *rfn,
 515                         spinlock_t *lock)
 516{
 517        return blk_init_allocated_queue_node(q, rfn, lock, -1);
 518}
 519EXPORT_SYMBOL(blk_init_allocated_queue);
 520
 521struct request_queue *
 522blk_init_allocated_queue_node(struct request_queue *q, request_fn_proc *rfn,
 523                              spinlock_t *lock, int node_id)
 524{
 525        if (!q)
 526                return NULL;
 527
 528        q->node = node_id;
 529        if (blk_init_free_list(q))
 530                return NULL;
 531
 532        q->request_fn           = rfn;
 533        q->prep_rq_fn           = NULL;
 534        q->unprep_rq_fn         = NULL;
 535        q->queue_flags          = QUEUE_FLAG_DEFAULT;
 536
 537        /* Override internal queue lock with supplied lock pointer */
 538        if (lock)
 539                q->queue_lock           = lock;
 540
 541        /*
 542         * This also sets hw/phys segments, boundary and size
 543         */
 544        blk_queue_make_request(q, __make_request);
 545
 546        q->sg_reserved_size = INT_MAX;
 547
 548        /*
 549         * all done
 550         */
 551        if (!elevator_init(q, NULL)) {
 552                blk_queue_congestion_threshold(q);
 553                return q;
 554        }
 555
 556        return NULL;
 557}
 558EXPORT_SYMBOL(blk_init_allocated_queue_node);
 559
 560int blk_get_queue(struct request_queue *q)
 561{
 562        if (likely(!test_bit(QUEUE_FLAG_DEAD, &q->queue_flags))) {
 563                kobject_get(&q->kobj);
 564                return 0;
 565        }
 566
 567        return 1;
 568}
 569
 570static inline void blk_free_request(struct request_queue *q, struct request *rq)
 571{
 572        BUG_ON(rq->cmd_flags & REQ_ON_PLUG);
 573
 574        if (rq->cmd_flags & REQ_ELVPRIV)
 575                elv_put_request(q, rq);
 576        mempool_free(rq, q->rq.rq_pool);
 577}
 578
 579static struct request *
 580blk_alloc_request(struct request_queue *q, int flags, int priv, gfp_t gfp_mask)
 581{
 582        struct request *rq = mempool_alloc(q->rq.rq_pool, gfp_mask);
 583
 584        if (!rq)
 585                return NULL;
 586
 587        blk_rq_init(q, rq);
 588
 589        rq->cmd_flags = flags | REQ_ALLOCED;
 590
 591        if (priv) {
 592                if (unlikely(elv_set_request(q, rq, gfp_mask))) {
 593                        mempool_free(rq, q->rq.rq_pool);
 594                        return NULL;
 595                }
 596                rq->cmd_flags |= REQ_ELVPRIV;
 597        }
 598
 599        return rq;
 600}
 601
 602/*
 603 * ioc_batching returns true if the ioc is a valid batching request and
 604 * should be given priority access to a request.
 605 */
 606static inline int ioc_batching(struct request_queue *q, struct io_context *ioc)
 607{
 608        if (!ioc)
 609                return 0;
 610
 611        /*
 612         * Make sure the process is able to allocate at least 1 request
 613         * even if the batch times out, otherwise we could theoretically
 614         * lose wakeups.
 615         */
 616        return ioc->nr_batch_requests == q->nr_batching ||
 617                (ioc->nr_batch_requests > 0
 618                && time_before(jiffies, ioc->last_waited + BLK_BATCH_TIME));
 619}
 620
 621/*
 622 * ioc_set_batching sets ioc to be a new "batcher" if it is not one. This
 623 * will cause the process to be a "batcher" on all queues in the system. This
 624 * is the behaviour we want though - once it gets a wakeup it should be given
 625 * a nice run.
 626 */
 627static void ioc_set_batching(struct request_queue *q, struct io_context *ioc)
 628{
 629        if (!ioc || ioc_batching(q, ioc))
 630                return;
 631
 632        ioc->nr_batch_requests = q->nr_batching;
 633        ioc->last_waited = jiffies;
 634}
 635
 636static void __freed_request(struct request_queue *q, int sync)
 637{
 638        struct request_list *rl = &q->rq;
 639
 640        if (rl->count[sync] < queue_congestion_off_threshold(q))
 641                blk_clear_queue_congested(q, sync);
 642
 643        if (rl->count[sync] + 1 <= q->nr_requests) {
 644                if (waitqueue_active(&rl->wait[sync]))
 645                        wake_up(&rl->wait[sync]);
 646
 647                blk_clear_queue_full(q, sync);
 648        }
 649}
 650
 651/*
 652 * A request has just been released.  Account for it, update the full and
 653 * congestion status, wake up any waiters.   Called under q->queue_lock.
 654 */
 655static void freed_request(struct request_queue *q, int sync, int priv)
 656{
 657        struct request_list *rl = &q->rq;
 658
 659        rl->count[sync]--;
 660        if (priv)
 661                rl->elvpriv--;
 662
 663        __freed_request(q, sync);
 664
 665        if (unlikely(rl->starved[sync ^ 1]))
 666                __freed_request(q, sync ^ 1);
 667}
 668
 669/*
 670 * Determine if elevator data should be initialized when allocating the
 671 * request associated with @bio.
 672 */
 673static bool blk_rq_should_init_elevator(struct bio *bio)
 674{
 675        if (!bio)
 676                return true;
 677
 678        /*
 679         * Flush requests do not use the elevator so skip initialization.
 680         * This allows a request to share the flush and elevator data.
 681         */
 682        if (bio->bi_rw & (REQ_FLUSH | REQ_FUA))
 683                return false;
 684
 685        return true;
 686}
 687
 688/*
 689 * Get a free request, queue_lock must be held.
 690 * Returns NULL on failure, with queue_lock held.
 691 * Returns !NULL on success, with queue_lock *not held*.
 692 */
 693static struct request *get_request(struct request_queue *q, int rw_flags,
 694                                   struct bio *bio, gfp_t gfp_mask)
 695{
 696        struct request *rq = NULL;
 697        struct request_list *rl = &q->rq;
 698        struct io_context *ioc = NULL;
 699        const bool is_sync = rw_is_sync(rw_flags) != 0;
 700        int may_queue, priv = 0;
 701
 702        may_queue = elv_may_queue(q, rw_flags);
 703        if (may_queue == ELV_MQUEUE_NO)
 704                goto rq_starved;
 705
 706        if (rl->count[is_sync]+1 >= queue_congestion_on_threshold(q)) {
 707                if (rl->count[is_sync]+1 >= q->nr_requests) {
 708                        ioc = current_io_context(GFP_ATOMIC, q->node);
 709                        /*
 710                         * The queue will fill after this allocation, so set
 711                         * it as full, and mark this process as "batching".
 712                         * This process will be allowed to complete a batch of
 713                         * requests, others will be blocked.
 714                         */
 715                        if (!blk_queue_full(q, is_sync)) {
 716                                ioc_set_batching(q, ioc);
 717                                blk_set_queue_full(q, is_sync);
 718                        } else {
 719                                if (may_queue != ELV_MQUEUE_MUST
 720                                                && !ioc_batching(q, ioc)) {
 721                                        /*
 722                                         * The queue is full and the allocating
 723                                         * process is not a "batcher", and not
 724                                         * exempted by the IO scheduler
 725                                         */
 726                                        goto out;
 727                                }
 728                        }
 729                }
 730                blk_set_queue_congested(q, is_sync);
 731        }
 732
 733        /*
 734         * Only allow batching queuers to allocate up to 50% over the defined
 735         * limit of requests, otherwise we could have thousands of requests
 736         * allocated with any setting of ->nr_requests
 737         */
 738        if (rl->count[is_sync] >= (3 * q->nr_requests / 2))
 739                goto out;
 740
 741        rl->count[is_sync]++;
 742        rl->starved[is_sync] = 0;
 743
 744        if (blk_rq_should_init_elevator(bio)) {
 745                priv = !test_bit(QUEUE_FLAG_ELVSWITCH, &q->queue_flags);
 746                if (priv)
 747                        rl->elvpriv++;
 748        }
 749
 750        if (blk_queue_io_stat(q))
 751                rw_flags |= REQ_IO_STAT;
 752        spin_unlock_irq(q->queue_lock);
 753
 754        rq = blk_alloc_request(q, rw_flags, priv, gfp_mask);
 755        if (unlikely(!rq)) {
 756                /*
 757                 * Allocation failed presumably due to memory. Undo anything
 758                 * we might have messed up.
 759                 *
 760                 * Allocating task should really be put onto the front of the
 761                 * wait queue, but this is pretty rare.
 762                 */
 763                spin_lock_irq(q->queue_lock);
 764                freed_request(q, is_sync, priv);
 765
 766                /*
 767                 * in the very unlikely event that allocation failed and no
 768                 * requests for this direction was pending, mark us starved
 769                 * so that freeing of a request in the other direction will
 770                 * notice us. another possible fix would be to split the
 771                 * rq mempool into READ and WRITE
 772                 */
 773rq_starved:
 774                if (unlikely(rl->count[is_sync] == 0))
 775                        rl->starved[is_sync] = 1;
 776
 777                goto out;
 778        }
 779
 780        /*
 781         * ioc may be NULL here, and ioc_batching will be false. That's
 782         * OK, if the queue is under the request limit then requests need
 783         * not count toward the nr_batch_requests limit. There will always
 784         * be some limit enforced by BLK_BATCH_TIME.
 785         */
 786        if (ioc_batching(q, ioc))
 787                ioc->nr_batch_requests--;
 788
 789        trace_block_getrq(q, bio, rw_flags & 1);
 790out:
 791        return rq;
 792}
 793
 794/*
 795 * No available requests for this queue, wait for some requests to become
 796 * available.
 797 *
 798 * Called with q->queue_lock held, and returns with it unlocked.
 799 */
 800static struct request *get_request_wait(struct request_queue *q, int rw_flags,
 801                                        struct bio *bio)
 802{
 803        const bool is_sync = rw_is_sync(rw_flags) != 0;
 804        struct request *rq;
 805
 806        rq = get_request(q, rw_flags, bio, GFP_NOIO);
 807        while (!rq) {
 808                DEFINE_WAIT(wait);
 809                struct io_context *ioc;
 810                struct request_list *rl = &q->rq;
 811
 812                prepare_to_wait_exclusive(&rl->wait[is_sync], &wait,
 813                                TASK_UNINTERRUPTIBLE);
 814
 815                trace_block_sleeprq(q, bio, rw_flags & 1);
 816
 817                spin_unlock_irq(q->queue_lock);
 818                io_schedule();
 819
 820                /*
 821                 * After sleeping, we become a "batching" process and
 822                 * will be able to allocate at least one request, and
 823                 * up to a big batch of them for a small period time.
 824                 * See ioc_batching, ioc_set_batching
 825                 */
 826                ioc = current_io_context(GFP_NOIO, q->node);
 827                ioc_set_batching(q, ioc);
 828
 829                spin_lock_irq(q->queue_lock);
 830                finish_wait(&rl->wait[is_sync], &wait);
 831
 832                rq = get_request(q, rw_flags, bio, GFP_NOIO);
 833        };
 834
 835        return rq;
 836}
 837
 838struct request *blk_get_request(struct request_queue *q, int rw, gfp_t gfp_mask)
 839{
 840        struct request *rq;
 841
 842        BUG_ON(rw != READ && rw != WRITE);
 843
 844        spin_lock_irq(q->queue_lock);
 845        if (gfp_mask & __GFP_WAIT) {
 846                rq = get_request_wait(q, rw, NULL);
 847        } else {
 848                rq = get_request(q, rw, NULL, gfp_mask);
 849                if (!rq)
 850                        spin_unlock_irq(q->queue_lock);
 851        }
 852        /* q->queue_lock is unlocked at this point */
 853
 854        return rq;
 855}
 856EXPORT_SYMBOL(blk_get_request);
 857
 858/**
 859 * blk_make_request - given a bio, allocate a corresponding struct request.
 860 * @q: target request queue
 861 * @bio:  The bio describing the memory mappings that will be submitted for IO.
 862 *        It may be a chained-bio properly constructed by block/bio layer.
 863 * @gfp_mask: gfp flags to be used for memory allocation
 864 *
 865 * blk_make_request is the parallel of generic_make_request for BLOCK_PC
 866 * type commands. Where the struct request needs to be farther initialized by
 867 * the caller. It is passed a &struct bio, which describes the memory info of
 868 * the I/O transfer.
 869 *
 870 * The caller of blk_make_request must make sure that bi_io_vec
 871 * are set to describe the memory buffers. That bio_data_dir() will return
 872 * the needed direction of the request. (And all bio's in the passed bio-chain
 873 * are properly set accordingly)
 874 *
 875 * If called under none-sleepable conditions, mapped bio buffers must not
 876 * need bouncing, by calling the appropriate masked or flagged allocator,
 877 * suitable for the target device. Otherwise the call to blk_queue_bounce will
 878 * BUG.
 879 *
 880 * WARNING: When allocating/cloning a bio-chain, careful consideration should be
 881 * given to how you allocate bios. In particular, you cannot use __GFP_WAIT for
 882 * anything but the first bio in the chain. Otherwise you risk waiting for IO
 883 * completion of a bio that hasn't been submitted yet, thus resulting in a
 884 * deadlock. Alternatively bios should be allocated using bio_kmalloc() instead
 885 * of bio_alloc(), as that avoids the mempool deadlock.
 886 * If possible a big IO should be split into smaller parts when allocation
 887 * fails. Partial allocation should not be an error, or you risk a live-lock.
 888 */
 889struct request *blk_make_request(struct request_queue *q, struct bio *bio,
 890                                 gfp_t gfp_mask)
 891{
 892        struct request *rq = blk_get_request(q, bio_data_dir(bio), gfp_mask);
 893
 894        if (unlikely(!rq))
 895                return ERR_PTR(-ENOMEM);
 896
 897        for_each_bio(bio) {
 898                struct bio *bounce_bio = bio;
 899                int ret;
 900
 901                blk_queue_bounce(q, &bounce_bio);
 902                ret = blk_rq_append_bio(q, rq, bounce_bio);
 903                if (unlikely(ret)) {
 904                        blk_put_request(rq);
 905                        return ERR_PTR(ret);
 906                }
 907        }
 908
 909        return rq;
 910}
 911EXPORT_SYMBOL(blk_make_request);
 912
 913/**
 914 * blk_requeue_request - put a request back on queue
 915 * @q:          request queue where request should be inserted
 916 * @rq:         request to be inserted
 917 *
 918 * Description:
 919 *    Drivers often keep queueing requests until the hardware cannot accept
 920 *    more, when that condition happens we need to put the request back
 921 *    on the queue. Must be called with queue lock held.
 922 */
 923void blk_requeue_request(struct request_queue *q, struct request *rq)
 924{
 925        blk_delete_timer(rq);
 926        blk_clear_rq_complete(rq);
 927        trace_block_rq_requeue(q, rq);
 928
 929        if (blk_rq_tagged(rq))
 930                blk_queue_end_tag(q, rq);
 931
 932        BUG_ON(blk_queued_rq(rq));
 933
 934        elv_requeue_request(q, rq);
 935}
 936EXPORT_SYMBOL(blk_requeue_request);
 937
 938static void add_acct_request(struct request_queue *q, struct request *rq,
 939                             int where)
 940{
 941        drive_stat_acct(rq, 1);
 942        __elv_add_request(q, rq, where);
 943}
 944
 945/**
 946 * blk_insert_request - insert a special request into a request queue
 947 * @q:          request queue where request should be inserted
 948 * @rq:         request to be inserted
 949 * @at_head:    insert request at head or tail of queue
 950 * @data:       private data
 951 *
 952 * Description:
 953 *    Many block devices need to execute commands asynchronously, so they don't
 954 *    block the whole kernel from preemption during request execution.  This is
 955 *    accomplished normally by inserting aritficial requests tagged as
 956 *    REQ_TYPE_SPECIAL in to the corresponding request queue, and letting them
 957 *    be scheduled for actual execution by the request queue.
 958 *
 959 *    We have the option of inserting the head or the tail of the queue.
 960 *    Typically we use the tail for new ioctls and so forth.  We use the head
 961 *    of the queue for things like a QUEUE_FULL message from a device, or a
 962 *    host that is unable to accept a particular command.
 963 */
 964void blk_insert_request(struct request_queue *q, struct request *rq,
 965                        int at_head, void *data)
 966{
 967        int where = at_head ? ELEVATOR_INSERT_FRONT : ELEVATOR_INSERT_BACK;
 968        unsigned long flags;
 969
 970        /*
 971         * tell I/O scheduler that this isn't a regular read/write (ie it
 972         * must not attempt merges on this) and that it acts as a soft
 973         * barrier
 974         */
 975        rq->cmd_type = REQ_TYPE_SPECIAL;
 976
 977        rq->special = data;
 978
 979        spin_lock_irqsave(q->queue_lock, flags);
 980
 981        /*
 982         * If command is tagged, release the tag
 983         */
 984        if (blk_rq_tagged(rq))
 985                blk_queue_end_tag(q, rq);
 986
 987        add_acct_request(q, rq, where);
 988        __blk_run_queue(q);
 989        spin_unlock_irqrestore(q->queue_lock, flags);
 990}
 991EXPORT_SYMBOL(blk_insert_request);
 992
 993static void part_round_stats_single(int cpu, struct hd_struct *part,
 994                                    unsigned long now)
 995{
 996        if (now == part->stamp)
 997                return;
 998
 999        if (part_in_flight(part)) {
1000                __part_stat_add(cpu, part, time_in_queue,
1001                                part_in_flight(part) * (now - part->stamp));
1002                __part_stat_add(cpu, part, io_ticks, (now - part->stamp));
1003        }
1004        part->stamp = now;
1005}
1006
1007/**
1008 * part_round_stats() - Round off the performance stats on a struct disk_stats.
1009 * @cpu: cpu number for stats access
1010 * @part: target partition
1011 *
1012 * The average IO queue length and utilisation statistics are maintained
1013 * by observing the current state of the queue length and the amount of
1014 * time it has been in this state for.
1015 *
1016 * Normally, that accounting is done on IO completion, but that can result
1017 * in more than a second's worth of IO being accounted for within any one
1018 * second, leading to >100% utilisation.  To deal with that, we call this
1019 * function to do a round-off before returning the results when reading
1020 * /proc/diskstats.  This accounts immediately for all queue usage up to
1021 * the current jiffies and restarts the counters again.
1022 */
1023void part_round_stats(int cpu, struct hd_struct *part)
1024{
1025        unsigned long now = jiffies;
1026
1027        if (part->partno)
1028                part_round_stats_single(cpu, &part_to_disk(part)->part0, now);
1029        part_round_stats_single(cpu, part, now);
1030}
1031EXPORT_SYMBOL_GPL(part_round_stats);
1032
1033/*
1034 * queue lock must be held
1035 */
1036void __blk_put_request(struct request_queue *q, struct request *req)
1037{
1038        if (unlikely(!q))
1039                return;
1040        if (unlikely(--req->ref_count))
1041                return;
1042
1043        elv_completed_request(q, req);
1044
1045        /* this is a bio leak */
1046        WARN_ON(req->bio != NULL);
1047
1048        /*
1049         * Request may not have originated from ll_rw_blk. if not,
1050         * it didn't come out of our reserved rq pools
1051         */
1052        if (req->cmd_flags & REQ_ALLOCED) {
1053                int is_sync = rq_is_sync(req) != 0;
1054                int priv = req->cmd_flags & REQ_ELVPRIV;
1055
1056                BUG_ON(!list_empty(&req->queuelist));
1057                BUG_ON(!hlist_unhashed(&req->hash));
1058
1059                blk_free_request(q, req);
1060                freed_request(q, is_sync, priv);
1061        }
1062}
1063EXPORT_SYMBOL_GPL(__blk_put_request);
1064
1065void blk_put_request(struct request *req)
1066{
1067        unsigned long flags;
1068        struct request_queue *q = req->q;
1069
1070        spin_lock_irqsave(q->queue_lock, flags);
1071        __blk_put_request(q, req);
1072        spin_unlock_irqrestore(q->queue_lock, flags);
1073}
1074EXPORT_SYMBOL(blk_put_request);
1075
1076/**
1077 * blk_add_request_payload - add a payload to a request
1078 * @rq: request to update
1079 * @page: page backing the payload
1080 * @len: length of the payload.
1081 *
1082 * This allows to later add a payload to an already submitted request by
1083 * a block driver.  The driver needs to take care of freeing the payload
1084 * itself.
1085 *
1086 * Note that this is a quite horrible hack and nothing but handling of
1087 * discard requests should ever use it.
1088 */
1089void blk_add_request_payload(struct request *rq, struct page *page,
1090                unsigned int len)
1091{
1092        struct bio *bio = rq->bio;
1093
1094        bio->bi_io_vec->bv_page = page;
1095        bio->bi_io_vec->bv_offset = 0;
1096        bio->bi_io_vec->bv_len = len;
1097
1098        bio->bi_size = len;
1099        bio->bi_vcnt = 1;
1100        bio->bi_phys_segments = 1;
1101
1102        rq->__data_len = rq->resid_len = len;
1103        rq->nr_phys_segments = 1;
1104        rq->buffer = bio_data(bio);
1105}
1106EXPORT_SYMBOL_GPL(blk_add_request_payload);
1107
1108static bool bio_attempt_back_merge(struct request_queue *q, struct request *req,
1109                                   struct bio *bio)
1110{
1111        const int ff = bio->bi_rw & REQ_FAILFAST_MASK;
1112
1113        /*
1114         * Debug stuff, kill later
1115         */
1116        if (!rq_mergeable(req)) {
1117                blk_dump_rq_flags(req, "back");
1118                return false;
1119        }
1120
1121        if (!ll_back_merge_fn(q, req, bio))
1122                return false;
1123
1124        trace_block_bio_backmerge(q, bio);
1125
1126        if ((req->cmd_flags & REQ_FAILFAST_MASK) != ff)
1127                blk_rq_set_mixed_merge(req);
1128
1129        req->biotail->bi_next = bio;
1130        req->biotail = bio;
1131        req->__data_len += bio->bi_size;
1132        req->ioprio = ioprio_best(req->ioprio, bio_prio(bio));
1133
1134        drive_stat_acct(req, 0);
1135        return true;
1136}
1137
1138static bool bio_attempt_front_merge(struct request_queue *q,
1139                                    struct request *req, struct bio *bio)
1140{
1141        const int ff = bio->bi_rw & REQ_FAILFAST_MASK;
1142        sector_t sector;
1143
1144        /*
1145         * Debug stuff, kill later
1146         */
1147        if (!rq_mergeable(req)) {
1148                blk_dump_rq_flags(req, "front");
1149                return false;
1150        }
1151
1152        if (!ll_front_merge_fn(q, req, bio))
1153                return false;
1154
1155        trace_block_bio_frontmerge(q, bio);
1156
1157        if ((req->cmd_flags & REQ_FAILFAST_MASK) != ff)
1158                blk_rq_set_mixed_merge(req);
1159
1160        sector = bio->bi_sector;
1161
1162        bio->bi_next = req->bio;
1163        req->bio = bio;
1164
1165        /*
1166         * may not be valid. if the low level driver said
1167         * it didn't need a bounce buffer then it better
1168         * not touch req->buffer either...
1169         */
1170        req->buffer = bio_data(bio);
1171        req->__sector = bio->bi_sector;
1172        req->__data_len += bio->bi_size;
1173        req->ioprio = ioprio_best(req->ioprio, bio_prio(bio));
1174
1175        drive_stat_acct(req, 0);
1176        return true;
1177}
1178
1179/*
1180 * Attempts to merge with the plugged list in the current process. Returns
1181 * true if merge was successful, otherwise false.
1182 */
1183static bool attempt_plug_merge(struct task_struct *tsk, struct request_queue *q,
1184                               struct bio *bio)
1185{
1186        struct blk_plug *plug;
1187        struct request *rq;
1188        bool ret = false;
1189
1190        plug = tsk->plug;
1191        if (!plug)
1192                goto out;
1193
1194        list_for_each_entry_reverse(rq, &plug->list, queuelist) {
1195                int el_ret;
1196
1197                if (rq->q != q)
1198                        continue;
1199
1200                el_ret = elv_try_merge(rq, bio);
1201                if (el_ret == ELEVATOR_BACK_MERGE) {
1202                        ret = bio_attempt_back_merge(q, rq, bio);
1203                        if (ret)
1204                                break;
1205                } else if (el_ret == ELEVATOR_FRONT_MERGE) {
1206                        ret = bio_attempt_front_merge(q, rq, bio);
1207                        if (ret)
1208                                break;
1209                }
1210        }
1211out:
1212        return ret;
1213}
1214
1215void init_request_from_bio(struct request *req, struct bio *bio)
1216{
1217        req->cpu = bio->bi_comp_cpu;
1218        req->cmd_type = REQ_TYPE_FS;
1219
1220        req->cmd_flags |= bio->bi_rw & REQ_COMMON_MASK;
1221        if (bio->bi_rw & REQ_RAHEAD)
1222                req->cmd_flags |= REQ_FAILFAST_MASK;
1223
1224        req->errors = 0;
1225        req->__sector = bio->bi_sector;
1226        req->ioprio = bio_prio(bio);
1227        blk_rq_bio_prep(req->q, req, bio);
1228}
1229
1230static int __make_request(struct request_queue *q, struct bio *bio)
1231{
1232        const bool sync = !!(bio->bi_rw & REQ_SYNC);
1233        struct blk_plug *plug;
1234        int el_ret, rw_flags, where = ELEVATOR_INSERT_SORT;
1235        struct request *req;
1236
1237        /*
1238         * low level driver can indicate that it wants pages above a
1239         * certain limit bounced to low memory (ie for highmem, or even
1240         * ISA dma in theory)
1241         */
1242        blk_queue_bounce(q, &bio);
1243
1244        if (bio->bi_rw & (REQ_FLUSH | REQ_FUA)) {
1245                spin_lock_irq(q->queue_lock);
1246                where = ELEVATOR_INSERT_FLUSH;
1247                goto get_rq;
1248        }
1249
1250        /*
1251         * Check if we can merge with the plugged list before grabbing
1252         * any locks.
1253         */
1254        if (attempt_plug_merge(current, q, bio))
1255                goto out;
1256
1257        spin_lock_irq(q->queue_lock);
1258
1259        el_ret = elv_merge(q, &req, bio);
1260        if (el_ret == ELEVATOR_BACK_MERGE) {
1261                BUG_ON(req->cmd_flags & REQ_ON_PLUG);
1262                if (bio_attempt_back_merge(q, req, bio)) {
1263                        if (!attempt_back_merge(q, req))
1264                                elv_merged_request(q, req, el_ret);
1265                        goto out_unlock;
1266                }
1267        } else if (el_ret == ELEVATOR_FRONT_MERGE) {
1268                BUG_ON(req->cmd_flags & REQ_ON_PLUG);
1269                if (bio_attempt_front_merge(q, req, bio)) {
1270                        if (!attempt_front_merge(q, req))
1271                                elv_merged_request(q, req, el_ret);
1272                        goto out_unlock;
1273                }
1274        }
1275
1276get_rq:
1277        /*
1278         * This sync check and mask will be re-done in init_request_from_bio(),
1279         * but we need to set it earlier to expose the sync flag to the
1280         * rq allocator and io schedulers.
1281         */
1282        rw_flags = bio_data_dir(bio);
1283        if (sync)
1284                rw_flags |= REQ_SYNC;
1285
1286        /*
1287         * Grab a free request. This is might sleep but can not fail.
1288         * Returns with the queue unlocked.
1289         */
1290        req = get_request_wait(q, rw_flags, bio);
1291
1292        /*
1293         * After dropping the lock and possibly sleeping here, our request
1294         * may now be mergeable after it had proven unmergeable (above).
1295         * We don't worry about that case for efficiency. It won't happen
1296         * often, and the elevators are able to handle it.
1297         */
1298        init_request_from_bio(req, bio);
1299
1300        if (test_bit(QUEUE_FLAG_SAME_COMP, &q->queue_flags) ||
1301            bio_flagged(bio, BIO_CPU_AFFINE)) {
1302                req->cpu = blk_cpu_to_group(get_cpu());
1303                put_cpu();
1304        }
1305
1306        plug = current->plug;
1307        if (plug) {
1308                /*
1309                 * If this is the first request added after a plug, fire
1310                 * of a plug trace. If others have been added before, check
1311                 * if we have multiple devices in this plug. If so, make a
1312                 * note to sort the list before dispatch.
1313                 */
1314                if (list_empty(&plug->list))
1315                        trace_block_plug(q);
1316                else if (!plug->should_sort) {
1317                        struct request *__rq;
1318
1319                        __rq = list_entry_rq(plug->list.prev);
1320                        if (__rq->q != q)
1321                                plug->should_sort = 1;
1322                }
1323                /*
1324                 * Debug flag, kill later
1325                 */
1326                req->cmd_flags |= REQ_ON_PLUG;
1327                list_add_tail(&req->queuelist, &plug->list);
1328                drive_stat_acct(req, 1);
1329        } else {
1330                spin_lock_irq(q->queue_lock);
1331                add_acct_request(q, req, where);
1332                __blk_run_queue(q);
1333out_unlock:
1334                spin_unlock_irq(q->queue_lock);
1335        }
1336out:
1337        return 0;
1338}
1339
1340/*
1341 * If bio->bi_dev is a partition, remap the location
1342 */
1343static inline void blk_partition_remap(struct bio *bio)
1344{
1345        struct block_device *bdev = bio->bi_bdev;
1346
1347        if (bio_sectors(bio) && bdev != bdev->bd_contains) {
1348                struct hd_struct *p = bdev->bd_part;
1349
1350                bio->bi_sector += p->start_sect;
1351                bio->bi_bdev = bdev->bd_contains;
1352
1353                trace_block_bio_remap(bdev_get_queue(bio->bi_bdev), bio,
1354                                      bdev->bd_dev,
1355                                      bio->bi_sector - p->start_sect);
1356        }
1357}
1358
1359static void handle_bad_sector(struct bio *bio)
1360{
1361        char b[BDEVNAME_SIZE];
1362
1363        printk(KERN_INFO "attempt to access beyond end of device\n");
1364        printk(KERN_INFO "%s: rw=%ld, want=%Lu, limit=%Lu\n",
1365                        bdevname(bio->bi_bdev, b),
1366                        bio->bi_rw,
1367                        (unsigned long long)bio->bi_sector + bio_sectors(bio),
1368                        (long long)(i_size_read(bio->bi_bdev->bd_inode) >> 9));
1369
1370        set_bit(BIO_EOF, &bio->bi_flags);
1371}
1372
1373#ifdef CONFIG_FAIL_MAKE_REQUEST
1374
1375static DECLARE_FAULT_ATTR(fail_make_request);
1376
1377static int __init setup_fail_make_request(char *str)
1378{
1379        return setup_fault_attr(&fail_make_request, str);
1380}
1381__setup("fail_make_request=", setup_fail_make_request);
1382
1383static int should_fail_request(struct bio *bio)
1384{
1385        struct hd_struct *part = bio->bi_bdev->bd_part;
1386
1387        if (part_to_disk(part)->part0.make_it_fail || part->make_it_fail)
1388                return should_fail(&fail_make_request, bio->bi_size);
1389
1390        return 0;
1391}
1392
1393static int __init fail_make_request_debugfs(void)
1394{
1395        return init_fault_attr_dentries(&fail_make_request,
1396                                        "fail_make_request");
1397}
1398
1399late_initcall(fail_make_request_debugfs);
1400
1401#else /* CONFIG_FAIL_MAKE_REQUEST */
1402
1403static inline int should_fail_request(struct bio *bio)
1404{
1405        return 0;
1406}
1407
1408#endif /* CONFIG_FAIL_MAKE_REQUEST */
1409
1410/*
1411 * Check whether this bio extends beyond the end of the device.
1412 */
1413static inline int bio_check_eod(struct bio *bio, unsigned int nr_sectors)
1414{
1415        sector_t maxsector;
1416
1417        if (!nr_sectors)
1418                return 0;
1419
1420        /* Test device or partition size, when known. */
1421        maxsector = i_size_read(bio->bi_bdev->bd_inode) >> 9;
1422        if (maxsector) {
1423                sector_t sector = bio->bi_sector;
1424
1425                if (maxsector < nr_sectors || maxsector - nr_sectors < sector) {
1426                        /*
1427                         * This may well happen - the kernel calls bread()
1428                         * without checking the size of the device, e.g., when
1429                         * mounting a device.
1430                         */
1431                        handle_bad_sector(bio);
1432                        return 1;
1433                }
1434        }
1435
1436        return 0;
1437}
1438
1439/**
1440 * generic_make_request - hand a buffer to its device driver for I/O
1441 * @bio:  The bio describing the location in memory and on the device.
1442 *
1443 * generic_make_request() is used to make I/O requests of block
1444 * devices. It is passed a &struct bio, which describes the I/O that needs
1445 * to be done.
1446 *
1447 * generic_make_request() does not return any status.  The
1448 * success/failure status of the request, along with notification of
1449 * completion, is delivered asynchronously through the bio->bi_end_io
1450 * function described (one day) else where.
1451 *
1452 * The caller of generic_make_request must make sure that bi_io_vec
1453 * are set to describe the memory buffer, and that bi_dev and bi_sector are
1454 * set to describe the device address, and the
1455 * bi_end_io and optionally bi_private are set to describe how
1456 * completion notification should be signaled.
1457 *
1458 * generic_make_request and the drivers it calls may use bi_next if this
1459 * bio happens to be merged with someone else, and may change bi_dev and
1460 * bi_sector for remaps as it sees fit.  So the values of these fields
1461 * should NOT be depended on after the call to generic_make_request.
1462 */
1463static inline void __generic_make_request(struct bio *bio)
1464{
1465        struct request_queue *q;
1466        sector_t old_sector;
1467        int ret, nr_sectors = bio_sectors(bio);
1468        dev_t old_dev;
1469        int err = -EIO;
1470
1471        might_sleep();
1472
1473        if (bio_check_eod(bio, nr_sectors))
1474                goto end_io;
1475
1476        /*
1477         * Resolve the mapping until finished. (drivers are
1478         * still free to implement/resolve their own stacking
1479         * by explicitly returning 0)
1480         *
1481         * NOTE: we don't repeat the blk_size check for each new device.
1482         * Stacking drivers are expected to know what they are doing.
1483         */
1484        old_sector = -1;
1485        old_dev = 0;
1486        do {
1487                char b[BDEVNAME_SIZE];
1488
1489                q = bdev_get_queue(bio->bi_bdev);
1490                if (unlikely(!q)) {
1491                        printk(KERN_ERR
1492                               "generic_make_request: Trying to access "
1493                                "nonexistent block-device %s (%Lu)\n",
1494                                bdevname(bio->bi_bdev, b),
1495                                (long long) bio->bi_sector);
1496                        goto end_io;
1497                }
1498
1499                if (unlikely(!(bio->bi_rw & REQ_DISCARD) &&
1500                             nr_sectors > queue_max_hw_sectors(q))) {
1501                        printk(KERN_ERR "bio too big device %s (%u > %u)\n",
1502                               bdevname(bio->bi_bdev, b),
1503                               bio_sectors(bio),
1504                               queue_max_hw_sectors(q));
1505                        goto end_io;
1506                }
1507
1508                if (unlikely(test_bit(QUEUE_FLAG_DEAD, &q->queue_flags)))
1509                        goto end_io;
1510
1511                if (should_fail_request(bio))
1512                        goto end_io;
1513
1514                /*
1515                 * If this device has partitions, remap block n
1516                 * of partition p to block n+start(p) of the disk.
1517                 */
1518                blk_partition_remap(bio);
1519
1520                if (bio_integrity_enabled(bio) && bio_integrity_prep(bio))
1521                        goto end_io;
1522
1523                if (old_sector != -1)
1524                        trace_block_bio_remap(q, bio, old_dev, old_sector);
1525
1526                old_sector = bio->bi_sector;
1527                old_dev = bio->bi_bdev->bd_dev;
1528
1529                if (bio_check_eod(bio, nr_sectors))
1530                        goto end_io;
1531
1532                /*
1533                 * Filter flush bio's early so that make_request based
1534                 * drivers without flush support don't have to worry
1535                 * about them.
1536                 */
1537                if ((bio->bi_rw & (REQ_FLUSH | REQ_FUA)) && !q->flush_flags) {
1538                        bio->bi_rw &= ~(REQ_FLUSH | REQ_FUA);
1539                        if (!nr_sectors) {
1540                                err = 0;
1541                                goto end_io;
1542                        }
1543                }
1544
1545                if ((bio->bi_rw & REQ_DISCARD) &&
1546                    (!blk_queue_discard(q) ||
1547                     ((bio->bi_rw & REQ_SECURE) &&
1548                      !blk_queue_secdiscard(q)))) {
1549                        err = -EOPNOTSUPP;
1550                        goto end_io;
1551                }
1552
1553                blk_throtl_bio(q, &bio);
1554
1555                /*
1556                 * If bio = NULL, bio has been throttled and will be submitted
1557                 * later.
1558                 */
1559                if (!bio)
1560                        break;
1561
1562                trace_block_bio_queue(q, bio);
1563
1564                ret = q->make_request_fn(q, bio);
1565        } while (ret);
1566
1567        return;
1568
1569end_io:
1570        bio_endio(bio, err);
1571}
1572
1573/*
1574 * We only want one ->make_request_fn to be active at a time,
1575 * else stack usage with stacked devices could be a problem.
1576 * So use current->bio_list to keep a list of requests
1577 * submited by a make_request_fn function.
1578 * current->bio_list is also used as a flag to say if
1579 * generic_make_request is currently active in this task or not.
1580 * If it is NULL, then no make_request is active.  If it is non-NULL,
1581 * then a make_request is active, and new requests should be added
1582 * at the tail
1583 */
1584void generic_make_request(struct bio *bio)
1585{
1586        struct bio_list bio_list_on_stack;
1587
1588        if (current->bio_list) {
1589                /* make_request is active */
1590                bio_list_add(current->bio_list, bio);
1591                return;
1592        }
1593        /* following loop may be a bit non-obvious, and so deserves some
1594         * explanation.
1595         * Before entering the loop, bio->bi_next is NULL (as all callers
1596         * ensure that) so we have a list with a single bio.
1597         * We pretend that we have just taken it off a longer list, so
1598         * we assign bio_list to a pointer to the bio_list_on_stack,
1599         * thus initialising the bio_list of new bios to be
1600         * added.  __generic_make_request may indeed add some more bios
1601         * through a recursive call to generic_make_request.  If it
1602         * did, we find a non-NULL value in bio_list and re-enter the loop
1603         * from the top.  In this case we really did just take the bio
1604         * of the top of the list (no pretending) and so remove it from
1605         * bio_list, and call into __generic_make_request again.
1606         *
1607         * The loop was structured like this to make only one call to
1608         * __generic_make_request (which is important as it is large and
1609         * inlined) and to keep the structure simple.
1610         */
1611        BUG_ON(bio->bi_next);
1612        bio_list_init(&bio_list_on_stack);
1613        current->bio_list = &bio_list_on_stack;
1614        do {
1615                __generic_make_request(bio);
1616                bio = bio_list_pop(current->bio_list);
1617        } while (bio);
1618        current->bio_list = NULL; /* deactivate */
1619}
1620EXPORT_SYMBOL(generic_make_request);
1621
1622/**
1623 * submit_bio - submit a bio to the block device layer for I/O
1624 * @rw: whether to %READ or %WRITE, or maybe to %READA (read ahead)
1625 * @bio: The &struct bio which describes the I/O
1626 *
1627 * submit_bio() is very similar in purpose to generic_make_request(), and
1628 * uses that function to do most of the work. Both are fairly rough
1629 * interfaces; @bio must be presetup and ready for I/O.
1630 *
1631 */
1632void submit_bio(int rw, struct bio *bio)
1633{
1634        int count = bio_sectors(bio);
1635
1636        bio->bi_rw |= rw;
1637
1638        /*
1639         * If it's a regular read/write or a barrier with data attached,
1640         * go through the normal accounting stuff before submission.
1641         */
1642        if (bio_has_data(bio) && !(rw & REQ_DISCARD)) {
1643                if (rw & WRITE) {
1644                        count_vm_events(PGPGOUT, count);
1645                } else {
1646                        task_io_account_read(bio->bi_size);
1647                        count_vm_events(PGPGIN, count);
1648                }
1649
1650                if (unlikely(block_dump)) {
1651                        char b[BDEVNAME_SIZE];
1652                        printk(KERN_DEBUG "%s(%d): %s block %Lu on %s (%u sectors)\n",
1653                        current->comm, task_pid_nr(current),
1654                                (rw & WRITE) ? "WRITE" : "READ",
1655                                (unsigned long long)bio->bi_sector,
1656                                bdevname(bio->bi_bdev, b),
1657                                count);
1658                }
1659        }
1660
1661        generic_make_request(bio);
1662}
1663EXPORT_SYMBOL(submit_bio);
1664
1665/**
1666 * blk_rq_check_limits - Helper function to check a request for the queue limit
1667 * @q:  the queue
1668 * @rq: the request being checked
1669 *
1670 * Description:
1671 *    @rq may have been made based on weaker limitations of upper-level queues
1672 *    in request stacking drivers, and it may violate the limitation of @q.
1673 *    Since the block layer and the underlying device driver trust @rq
1674 *    after it is inserted to @q, it should be checked against @q before
1675 *    the insertion using this generic function.
1676 *
1677 *    This function should also be useful for request stacking drivers
1678 *    in some cases below, so export this function.
1679 *    Request stacking drivers like request-based dm may change the queue
1680 *    limits while requests are in the queue (e.g. dm's table swapping).
1681 *    Such request stacking drivers should check those requests agaist
1682 *    the new queue limits again when they dispatch those requests,
1683 *    although such checkings are also done against the old queue limits
1684 *    when submitting requests.
1685 */
1686int blk_rq_check_limits(struct request_queue *q, struct request *rq)
1687{
1688        if (rq->cmd_flags & REQ_DISCARD)
1689                return 0;
1690
1691        if (blk_rq_sectors(rq) > queue_max_sectors(q) ||
1692            blk_rq_bytes(rq) > queue_max_hw_sectors(q) << 9) {
1693                printk(KERN_ERR "%s: over max size limit.\n", __func__);
1694                return -EIO;
1695        }
1696
1697        /*
1698         * queue's settings related to segment counting like q->bounce_pfn
1699         * may differ from that of other stacking queues.
1700         * Recalculate it to check the request correctly on this queue's
1701         * limitation.
1702         */
1703        blk_recalc_rq_segments(rq);
1704        if (rq->nr_phys_segments > queue_max_segments(q)) {
1705                printk(KERN_ERR "%s: over max segments limit.\n", __func__);
1706                return -EIO;
1707        }
1708
1709        return 0;
1710}
1711EXPORT_SYMBOL_GPL(blk_rq_check_limits);
1712
1713/**
1714 * blk_insert_cloned_request - Helper for stacking drivers to submit a request
1715 * @q:  the queue to submit the request
1716 * @rq: the request being queued
1717 */
1718int blk_insert_cloned_request(struct request_queue *q, struct request *rq)
1719{
1720        unsigned long flags;
1721
1722        if (blk_rq_check_limits(q, rq))
1723                return -EIO;
1724
1725#ifdef CONFIG_FAIL_MAKE_REQUEST
1726        if (rq->rq_disk && rq->rq_disk->part0.make_it_fail &&
1727            should_fail(&fail_make_request, blk_rq_bytes(rq)))
1728                return -EIO;
1729#endif
1730
1731        spin_lock_irqsave(q->queue_lock, flags);
1732
1733        /*
1734         * Submitting request must be dequeued before calling this function
1735         * because it will be linked to another request_queue
1736         */
1737        BUG_ON(blk_queued_rq(rq));
1738
1739        add_acct_request(q, rq, ELEVATOR_INSERT_BACK);
1740        spin_unlock_irqrestore(q->queue_lock, flags);
1741
1742        return 0;
1743}
1744EXPORT_SYMBOL_GPL(blk_insert_cloned_request);
1745
1746/**
1747 * blk_rq_err_bytes - determine number of bytes till the next failure boundary
1748 * @rq: request to examine
1749 *
1750 * Description:
1751 *     A request could be merge of IOs which require different failure
1752 *     handling.  This function determines the number of bytes which
1753 *     can be failed from the beginning of the request without
1754 *     crossing into area which need to be retried further.
1755 *
1756 * Return:
1757 *     The number of bytes to fail.
1758 *
1759 * Context:
1760 *     queue_lock must be held.
1761 */
1762unsigned int blk_rq_err_bytes(const struct request *rq)
1763{
1764        unsigned int ff = rq->cmd_flags & REQ_FAILFAST_MASK;
1765        unsigned int bytes = 0;
1766        struct bio *bio;
1767
1768        if (!(rq->cmd_flags & REQ_MIXED_MERGE))
1769                return blk_rq_bytes(rq);
1770
1771        /*
1772         * Currently the only 'mixing' which can happen is between
1773         * different fastfail types.  We can safely fail portions
1774         * which have all the failfast bits that the first one has -
1775         * the ones which are at least as eager to fail as the first
1776         * one.
1777         */
1778        for (bio = rq->bio; bio; bio = bio->bi_next) {
1779                if ((bio->bi_rw & ff) != ff)
1780                        break;
1781                bytes += bio->bi_size;
1782        }
1783
1784        /* this could lead to infinite loop */
1785        BUG_ON(blk_rq_bytes(rq) && !bytes);
1786        return bytes;
1787}
1788EXPORT_SYMBOL_GPL(blk_rq_err_bytes);
1789
1790static void blk_account_io_completion(struct request *req, unsigned int bytes)
1791{
1792        if (blk_do_io_stat(req)) {
1793                const int rw = rq_data_dir(req);
1794                struct hd_struct *part;
1795                int cpu;
1796
1797                cpu = part_stat_lock();
1798                part = req->part;
1799                part_stat_add(cpu, part, sectors[rw], bytes >> 9);
1800                part_stat_unlock();
1801        }
1802}
1803
1804static void blk_account_io_done(struct request *req)
1805{
1806        /*
1807         * Account IO completion.  flush_rq isn't accounted as a
1808         * normal IO on queueing nor completion.  Accounting the
1809         * containing request is enough.
1810         */
1811        if (blk_do_io_stat(req) && !(req->cmd_flags & REQ_FLUSH_SEQ)) {
1812                unsigned long duration = jiffies - req->start_time;
1813                const int rw = rq_data_dir(req);
1814                struct hd_struct *part;
1815                int cpu;
1816
1817                cpu = part_stat_lock();
1818                part = req->part;
1819
1820                part_stat_inc(cpu, part, ios[rw]);
1821                part_stat_add(cpu, part, ticks[rw], duration);
1822                part_round_stats(cpu, part);
1823                part_dec_in_flight(part, rw);
1824
1825                hd_struct_put(part);
1826                part_stat_unlock();
1827        }
1828}
1829
1830/**
1831 * blk_peek_request - peek at the top of a request queue
1832 * @q: request queue to peek at
1833 *
1834 * Description:
1835 *     Return the request at the top of @q.  The returned request
1836 *     should be started using blk_start_request() before LLD starts
1837 *     processing it.
1838 *
1839 * Return:
1840 *     Pointer to the request at the top of @q if available.  Null
1841 *     otherwise.
1842 *
1843 * Context:
1844 *     queue_lock must be held.
1845 */
1846struct request *blk_peek_request(struct request_queue *q)
1847{
1848        struct request *rq;
1849        int ret;
1850
1851        while ((rq = __elv_next_request(q)) != NULL) {
1852                if (!(rq->cmd_flags & REQ_STARTED)) {
1853                        /*
1854                         * This is the first time the device driver
1855                         * sees this request (possibly after
1856                         * requeueing).  Notify IO scheduler.
1857                         */
1858                        if (rq->cmd_flags & REQ_SORTED)
1859                                elv_activate_rq(q, rq);
1860
1861                        /*
1862                         * just mark as started even if we don't start
1863                         * it, a request that has been delayed should
1864                         * not be passed by new incoming requests
1865                         */
1866                        rq->cmd_flags |= REQ_STARTED;
1867                        trace_block_rq_issue(q, rq);
1868                }
1869
1870                if (!q->boundary_rq || q->boundary_rq == rq) {
1871                        q->end_sector = rq_end_sector(rq);
1872                        q->boundary_rq = NULL;
1873                }
1874
1875                if (rq->cmd_flags & REQ_DONTPREP)
1876                        break;
1877
1878                if (q->dma_drain_size && blk_rq_bytes(rq)) {
1879                        /*
1880                         * make sure space for the drain appears we
1881                         * know we can do this because max_hw_segments
1882                         * has been adjusted to be one fewer than the
1883                         * device can handle
1884                         */
1885                        rq->nr_phys_segments++;
1886                }
1887
1888                if (!q->prep_rq_fn)
1889                        break;
1890
1891                ret = q->prep_rq_fn(q, rq);
1892                if (ret == BLKPREP_OK) {
1893                        break;
1894                } else if (ret == BLKPREP_DEFER) {
1895                        /*
1896                         * the request may have been (partially) prepped.
1897                         * we need to keep this request in the front to
1898                         * avoid resource deadlock.  REQ_STARTED will
1899                         * prevent other fs requests from passing this one.
1900                         */
1901                        if (q->dma_drain_size && blk_rq_bytes(rq) &&
1902                            !(rq->cmd_flags & REQ_DONTPREP)) {
1903                                /*
1904                                 * remove the space for the drain we added
1905                                 * so that we don't add it again
1906                                 */
1907                                --rq->nr_phys_segments;
1908                        }
1909
1910                        rq = NULL;
1911                        break;
1912                } else if (ret == BLKPREP_KILL) {
1913                        rq->cmd_flags |= REQ_QUIET;
1914                        /*
1915                         * Mark this request as started so we don't trigger
1916                         * any debug logic in the end I/O path.
1917                         */
1918                        blk_start_request(rq);
1919                        __blk_end_request_all(rq, -EIO);
1920                } else {
1921                        printk(KERN_ERR "%s: bad return=%d\n", __func__, ret);
1922                        break;
1923                }
1924        }
1925
1926        return rq;
1927}
1928EXPORT_SYMBOL(blk_peek_request);
1929
1930void blk_dequeue_request(struct request *rq)
1931{
1932        struct request_queue *q = rq->q;
1933
1934        BUG_ON(list_empty(&rq->queuelist));
1935        BUG_ON(ELV_ON_HASH(rq));
1936
1937        list_del_init(&rq->queuelist);
1938
1939        /*
1940         * the time frame between a request being removed from the lists
1941         * and to it is freed is accounted as io that is in progress at
1942         * the driver side.
1943         */
1944        if (blk_account_rq(rq)) {
1945                q->in_flight[rq_is_sync(rq)]++;
1946                set_io_start_time_ns(rq);
1947        }
1948}
1949
1950/**
1951 * blk_start_request - start request processing on the driver
1952 * @req: request to dequeue
1953 *
1954 * Description:
1955 *     Dequeue @req and start timeout timer on it.  This hands off the
1956 *     request to the driver.
1957 *
1958 *     Block internal functions which don't want to start timer should
1959 *     call blk_dequeue_request().
1960 *
1961 * Context:
1962 *     queue_lock must be held.
1963 */
1964void blk_start_request(struct request *req)
1965{
1966        blk_dequeue_request(req);
1967
1968        /*
1969         * We are now handing the request to the hardware, initialize
1970         * resid_len to full count and add the timeout handler.
1971         */
1972        req->resid_len = blk_rq_bytes(req);
1973        if (unlikely(blk_bidi_rq(req)))
1974                req->next_rq->resid_len = blk_rq_bytes(req->next_rq);
1975
1976        blk_add_timer(req);
1977}
1978EXPORT_SYMBOL(blk_start_request);
1979
1980/**
1981 * blk_fetch_request - fetch a request from a request queue
1982 * @q: request queue to fetch a request from
1983 *
1984 * Description:
1985 *     Return the request at the top of @q.  The request is started on
1986 *     return and LLD can start processing it immediately.
1987 *
1988 * Return:
1989 *     Pointer to the request at the top of @q if available.  Null
1990 *     otherwise.
1991 *
1992 * Context:
1993 *     queue_lock must be held.
1994 */
1995struct request *blk_fetch_request(struct request_queue *q)
1996{
1997        struct request *rq;
1998
1999        rq = blk_peek_request(q);
2000        if (rq)
2001                blk_start_request(rq);
2002        return rq;
2003}
2004EXPORT_SYMBOL(blk_fetch_request);
2005
2006/**
2007 * blk_update_request - Special helper function for request stacking drivers
2008 * @req:      the request being processed
2009 * @error:    %0 for success, < %0 for error
2010 * @nr_bytes: number of bytes to complete @req
2011 *
2012 * Description:
2013 *     Ends I/O on a number of bytes attached to @req, but doesn't complete
2014 *     the request structure even if @req doesn't have leftover.
2015 *     If @req has leftover, sets it up for the next range of segments.
2016 *
2017 *     This special helper function is only for request stacking drivers
2018 *     (e.g. request-based dm) so that they can handle partial completion.
2019 *     Actual device drivers should use blk_end_request instead.
2020 *
2021 *     Passing the result of blk_rq_bytes() as @nr_bytes guarantees
2022 *     %false return from this function.
2023 *
2024 * Return:
2025 *     %false - this request doesn't have any more data
2026 *     %true  - this request has more data
2027 **/
2028bool blk_update_request(struct request *req, int error, unsigned int nr_bytes)
2029{
2030        int total_bytes, bio_nbytes, next_idx = 0;
2031        struct bio *bio;
2032
2033        if (!req->bio)
2034                return false;
2035
2036        trace_block_rq_complete(req->q, req);
2037
2038        /*
2039         * For fs requests, rq is just carrier of independent bio's
2040         * and each partial completion should be handled separately.
2041         * Reset per-request error on each partial completion.
2042         *
2043         * TODO: tj: This is too subtle.  It would be better to let
2044         * low level drivers do what they see fit.
2045         */
2046        if (req->cmd_type == REQ_TYPE_FS)
2047                req->errors = 0;
2048
2049        if (error && req->cmd_type == REQ_TYPE_FS &&
2050            !(req->cmd_flags & REQ_QUIET)) {
2051                char *error_type;
2052
2053                switch (error) {
2054                case -ENOLINK:
2055                        error_type = "recoverable transport";
2056                        break;
2057                case -EREMOTEIO:
2058                        error_type = "critical target";
2059                        break;
2060                case -EBADE:
2061                        error_type = "critical nexus";
2062                        break;
2063                case -EIO:
2064                default:
2065                        error_type = "I/O";
2066                        break;
2067                }
2068                printk(KERN_ERR "end_request: %s error, dev %s, sector %llu\n",
2069                       error_type, req->rq_disk ? req->rq_disk->disk_name : "?",
2070                       (unsigned long long)blk_rq_pos(req));
2071        }
2072
2073        blk_account_io_completion(req, nr_bytes);
2074
2075        total_bytes = bio_nbytes = 0;
2076        while ((bio = req->bio) != NULL) {
2077                int nbytes;
2078
2079                if (nr_bytes >= bio->bi_size) {
2080                        req->bio = bio->bi_next;
2081                        nbytes = bio->bi_size;
2082                        req_bio_endio(req, bio, nbytes, error);
2083                        next_idx = 0;
2084                        bio_nbytes = 0;
2085                } else {
2086                        int idx = bio->bi_idx + next_idx;
2087
2088                        if (unlikely(idx >= bio->bi_vcnt)) {
2089                                blk_dump_rq_flags(req, "__end_that");
2090                                printk(KERN_ERR "%s: bio idx %d >= vcnt %d\n",
2091                                       __func__, idx, bio->bi_vcnt);
2092                                break;
2093                        }
2094
2095                        nbytes = bio_iovec_idx(bio, idx)->bv_len;
2096                        BIO_BUG_ON(nbytes > bio->bi_size);
2097
2098                        /*
2099                         * not a complete bvec done
2100                         */
2101                        if (unlikely(nbytes > nr_bytes)) {
2102                                bio_nbytes += nr_bytes;
2103                                total_bytes += nr_bytes;
2104                                break;
2105                        }
2106
2107                        /*
2108                         * advance to the next vector
2109                         */
2110                        next_idx++;
2111                        bio_nbytes += nbytes;
2112                }
2113
2114                total_bytes += nbytes;
2115                nr_bytes -= nbytes;
2116
2117                bio = req->bio;
2118                if (bio) {
2119                        /*
2120                         * end more in this run, or just return 'not-done'
2121                         */
2122                        if (unlikely(nr_bytes <= 0))
2123                                break;
2124                }
2125        }
2126
2127        /*
2128         * completely done
2129         */
2130        if (!req->bio) {
2131                /*
2132                 * Reset counters so that the request stacking driver
2133                 * can find how many bytes remain in the request
2134                 * later.
2135                 */
2136                req->__data_len = 0;
2137                return false;
2138        }
2139
2140        /*
2141         * if the request wasn't completed, update state
2142         */
2143        if (bio_nbytes) {
2144                req_bio_endio(req, bio, bio_nbytes, error);
2145                bio->bi_idx += next_idx;
2146                bio_iovec(bio)->bv_offset += nr_bytes;
2147                bio_iovec(bio)->bv_len -= nr_bytes;
2148        }
2149
2150        req->__data_len -= total_bytes;
2151        req->buffer = bio_data(req->bio);
2152
2153        /* update sector only for requests with clear definition of sector */
2154        if (req->cmd_type == REQ_TYPE_FS || (req->cmd_flags & REQ_DISCARD))
2155                req->__sector += total_bytes >> 9;
2156
2157        /* mixed attributes always follow the first bio */
2158        if (req->cmd_flags & REQ_MIXED_MERGE) {
2159                req->cmd_flags &= ~REQ_FAILFAST_MASK;
2160                req->cmd_flags |= req->bio->bi_rw & REQ_FAILFAST_MASK;
2161        }
2162
2163        /*
2164         * If total number of sectors is less than the first segment
2165         * size, something has gone terribly wrong.
2166         */
2167        if (blk_rq_bytes(req) < blk_rq_cur_bytes(req)) {
2168                blk_dump_rq_flags(req, "request botched");
2169                req->__data_len = blk_rq_cur_bytes(req);
2170        }
2171
2172        /* recalculate the number of segments */
2173        blk_recalc_rq_segments(req);
2174
2175        return true;
2176}
2177EXPORT_SYMBOL_GPL(blk_update_request);
2178
2179static bool blk_update_bidi_request(struct request *rq, int error,
2180                                    unsigned int nr_bytes,
2181                                    unsigned int bidi_bytes)
2182{
2183        if (blk_update_request(rq, error, nr_bytes))
2184                return true;
2185
2186        /* Bidi request must be completed as a whole */
2187        if (unlikely(blk_bidi_rq(rq)) &&
2188            blk_update_request(rq->next_rq, error, bidi_bytes))
2189                return true;
2190
2191        if (blk_queue_add_random(rq->q))
2192                add_disk_randomness(rq->rq_disk);
2193
2194        return false;
2195}
2196
2197/**
2198 * blk_unprep_request - unprepare a request
2199 * @req:        the request
2200 *
2201 * This function makes a request ready for complete resubmission (or
2202 * completion).  It happens only after all error handling is complete,
2203 * so represents the appropriate moment to deallocate any resources
2204 * that were allocated to the request in the prep_rq_fn.  The queue
2205 * lock is held when calling this.
2206 */
2207void blk_unprep_request(struct request *req)
2208{
2209        struct request_queue *q = req->q;
2210
2211        req->cmd_flags &= ~REQ_DONTPREP;
2212        if (q->unprep_rq_fn)
2213                q->unprep_rq_fn(q, req);
2214}
2215EXPORT_SYMBOL_GPL(blk_unprep_request);
2216
2217/*
2218 * queue lock must be held
2219 */
2220static void blk_finish_request(struct request *req, int error)
2221{
2222        if (blk_rq_tagged(req))
2223                blk_queue_end_tag(req->q, req);
2224
2225        BUG_ON(blk_queued_rq(req));
2226
2227        if (unlikely(laptop_mode) && req->cmd_type == REQ_TYPE_FS)
2228                laptop_io_completion(&req->q->backing_dev_info);
2229
2230        blk_delete_timer(req);
2231
2232        if (req->cmd_flags & REQ_DONTPREP)
2233                blk_unprep_request(req);
2234
2235
2236        blk_account_io_done(req);
2237
2238        if (req->end_io)
2239                req->end_io(req, error);
2240        else {
2241                if (blk_bidi_rq(req))
2242                        __blk_put_request(req->next_rq->q, req->next_rq);
2243
2244                __blk_put_request(req->q, req);
2245        }
2246}
2247
2248/**
2249 * blk_end_bidi_request - Complete a bidi request
2250 * @rq:         the request to complete
2251 * @error:      %0 for success, < %0 for error
2252 * @nr_bytes:   number of bytes to complete @rq
2253 * @bidi_bytes: number of bytes to complete @rq->next_rq
2254 *
2255 * Description:
2256 *     Ends I/O on a number of bytes attached to @rq and @rq->next_rq.
2257 *     Drivers that supports bidi can safely call this member for any
2258 *     type of request, bidi or uni.  In the later case @bidi_bytes is
2259 *     just ignored.
2260 *
2261 * Return:
2262 *     %false - we are done with this request
2263 *     %true  - still buffers pending for this request
2264 **/
2265static bool blk_end_bidi_request(struct request *rq, int error,
2266                                 unsigned int nr_bytes, unsigned int bidi_bytes)
2267{
2268        struct request_queue *q = rq->q;
2269        unsigned long flags;
2270
2271        if (blk_update_bidi_request(rq, error, nr_bytes, bidi_bytes))
2272                return true;
2273
2274        spin_lock_irqsave(q->queue_lock, flags);
2275        blk_finish_request(rq, error);
2276        spin_unlock_irqrestore(q->queue_lock, flags);
2277
2278        return false;
2279}
2280
2281/**
2282 * __blk_end_bidi_request - Complete a bidi request with queue lock held
2283 * @rq:         the request to complete
2284 * @error:      %0 for success, < %0 for error
2285 * @nr_bytes:   number of bytes to complete @rq
2286 * @bidi_bytes: number of bytes to complete @rq->next_rq
2287 *
2288 * Description:
2289 *     Identical to blk_end_bidi_request() except that queue lock is
2290 *     assumed to be locked on entry and remains so on return.
2291 *
2292 * Return:
2293 *     %false - we are done with this request
2294 *     %true  - still buffers pending for this request
2295 **/
2296static bool __blk_end_bidi_request(struct request *rq, int error,
2297                                   unsigned int nr_bytes, unsigned int bidi_bytes)
2298{
2299        if (blk_update_bidi_request(rq, error, nr_bytes, bidi_bytes))
2300                return true;
2301
2302        blk_finish_request(rq, error);
2303
2304        return false;
2305}
2306
2307/**
2308 * blk_end_request - Helper function for drivers to complete the request.
2309 * @rq:       the request being processed
2310 * @error:    %0 for success, < %0 for error
2311 * @nr_bytes: number of bytes to complete
2312 *
2313 * Description:
2314 *     Ends I/O on a number of bytes attached to @rq.
2315 *     If @rq has leftover, sets it up for the next range of segments.
2316 *
2317 * Return:
2318 *     %false - we are done with this request
2319 *     %true  - still buffers pending for this request
2320 **/
2321bool blk_end_request(struct request *rq, int error, unsigned int nr_bytes)
2322{
2323        return blk_end_bidi_request(rq, error, nr_bytes, 0);
2324}
2325EXPORT_SYMBOL(blk_end_request);
2326
2327/**
2328 * blk_end_request_all - Helper function for drives to finish the request.
2329 * @rq: the request to finish
2330 * @error: %0 for success, < %0 for error
2331 *
2332 * Description:
2333 *     Completely finish @rq.
2334 */
2335void blk_end_request_all(struct request *rq, int error)
2336{
2337        bool pending;
2338        unsigned int bidi_bytes = 0;
2339
2340        if (unlikely(blk_bidi_rq(rq)))
2341                bidi_bytes = blk_rq_bytes(rq->next_rq);
2342
2343        pending = blk_end_bidi_request(rq, error, blk_rq_bytes(rq), bidi_bytes);
2344        BUG_ON(pending);
2345}
2346EXPORT_SYMBOL(blk_end_request_all);
2347
2348/**
2349 * blk_end_request_cur - Helper function to finish the current request chunk.
2350 * @rq: the request to finish the current chunk for
2351 * @error: %0 for success, < %0 for error
2352 *
2353 * Description:
2354 *     Complete the current consecutively mapped chunk from @rq.
2355 *
2356 * Return:
2357 *     %false - we are done with this request
2358 *     %true  - still buffers pending for this request
2359 */
2360bool blk_end_request_cur(struct request *rq, int error)
2361{
2362        return blk_end_request(rq, error, blk_rq_cur_bytes(rq));
2363}
2364EXPORT_SYMBOL(blk_end_request_cur);
2365
2366/**
2367 * blk_end_request_err - Finish a request till the next failure boundary.
2368 * @rq: the request to finish till the next failure boundary for
2369 * @error: must be negative errno
2370 *
2371 * Description:
2372 *     Complete @rq till the next failure boundary.
2373 *
2374 * Return:
2375 *     %false - we are done with this request
2376 *     %true  - still buffers pending for this request
2377 */
2378bool blk_end_request_err(struct request *rq, int error)
2379{
2380        WARN_ON(error >= 0);
2381        return blk_end_request(rq, error, blk_rq_err_bytes(rq));
2382}
2383EXPORT_SYMBOL_GPL(blk_end_request_err);
2384
2385/**
2386 * __blk_end_request - Helper function for drivers to complete the request.
2387 * @rq:       the request being processed
2388 * @error:    %0 for success, < %0 for error
2389 * @nr_bytes: number of bytes to complete
2390 *
2391 * Description:
2392 *     Must be called with queue lock held unlike blk_end_request().
2393 *
2394 * Return:
2395 *     %false - we are done with this request
2396 *     %true  - still buffers pending for this request
2397 **/
2398bool __blk_end_request(struct request *rq, int error, unsigned int nr_bytes)
2399{
2400        return __blk_end_bidi_request(rq, error, nr_bytes, 0);
2401}
2402EXPORT_SYMBOL(__blk_end_request);
2403
2404/**
2405 * __blk_end_request_all - Helper function for drives to finish the request.
2406 * @rq: the request to finish
2407 * @error: %0 for success, < %0 for error
2408 *
2409 * Description:
2410 *     Completely finish @rq.  Must be called with queue lock held.
2411 */
2412void __blk_end_request_all(struct request *rq, int error)
2413{
2414        bool pending;
2415        unsigned int bidi_bytes = 0;
2416
2417        if (unlikely(blk_bidi_rq(rq)))
2418                bidi_bytes = blk_rq_bytes(rq->next_rq);
2419
2420        pending = __blk_end_bidi_request(rq, error, blk_rq_bytes(rq), bidi_bytes);
2421        BUG_ON(pending);
2422}
2423EXPORT_SYMBOL(__blk_end_request_all);
2424
2425/**
2426 * __blk_end_request_cur - Helper function to finish the current request chunk.
2427 * @rq: the request to finish the current chunk for
2428 * @error: %0 for success, < %0 for error
2429 *
2430 * Description:
2431 *     Complete the current consecutively mapped chunk from @rq.  Must
2432 *     be called with queue lock held.
2433 *
2434 * Return:
2435 *     %false - we are done with this request
2436 *     %true  - still buffers pending for this request
2437 */
2438bool __blk_end_request_cur(struct request *rq, int error)
2439{
2440        return __blk_end_request(rq, error, blk_rq_cur_bytes(rq));
2441}
2442EXPORT_SYMBOL(__blk_end_request_cur);
2443
2444/**
2445 * __blk_end_request_err - Finish a request till the next failure boundary.
2446 * @rq: the request to finish till the next failure boundary for
2447 * @error: must be negative errno
2448 *
2449 * Description:
2450 *     Complete @rq till the next failure boundary.  Must be called
2451 *     with queue lock held.
2452 *
2453 * Return:
2454 *     %false - we are done with this request
2455 *     %true  - still buffers pending for this request
2456 */
2457bool __blk_end_request_err(struct request *rq, int error)
2458{
2459        WARN_ON(error >= 0);
2460        return __blk_end_request(rq, error, blk_rq_err_bytes(rq));
2461}
2462EXPORT_SYMBOL_GPL(__blk_end_request_err);
2463
2464void blk_rq_bio_prep(struct request_queue *q, struct request *rq,
2465                     struct bio *bio)
2466{
2467        /* Bit 0 (R/W) is identical in rq->cmd_flags and bio->bi_rw */
2468        rq->cmd_flags |= bio->bi_rw & REQ_WRITE;
2469
2470        if (bio_has_data(bio)) {
2471                rq->nr_phys_segments = bio_phys_segments(q, bio);
2472                rq->buffer = bio_data(bio);
2473        }
2474        rq->__data_len = bio->bi_size;
2475        rq->bio = rq->biotail = bio;
2476
2477        if (bio->bi_bdev)
2478                rq->rq_disk = bio->bi_bdev->bd_disk;
2479}
2480
2481#if ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE
2482/**
2483 * rq_flush_dcache_pages - Helper function to flush all pages in a request
2484 * @rq: the request to be flushed
2485 *
2486 * Description:
2487 *     Flush all pages in @rq.
2488 */
2489void rq_flush_dcache_pages(struct request *rq)
2490{
2491        struct req_iterator iter;
2492        struct bio_vec *bvec;
2493
2494        rq_for_each_segment(bvec, rq, iter)
2495                flush_dcache_page(bvec->bv_page);
2496}
2497EXPORT_SYMBOL_GPL(rq_flush_dcache_pages);
2498#endif
2499
2500/**
2501 * blk_lld_busy - Check if underlying low-level drivers of a device are busy
2502 * @q : the queue of the device being checked
2503 *
2504 * Description:
2505 *    Check if underlying low-level drivers of a device are busy.
2506 *    If the drivers want to export their busy state, they must set own
2507 *    exporting function using blk_queue_lld_busy() first.
2508 *
2509 *    Basically, this function is used only by request stacking drivers
2510 *    to stop dispatching requests to underlying devices when underlying
2511 *    devices are busy.  This behavior helps more I/O merging on the queue
2512 *    of the request stacking driver and prevents I/O throughput regression
2513 *    on burst I/O load.
2514 *
2515 * Return:
2516 *    0 - Not busy (The request stacking driver should dispatch request)
2517 *    1 - Busy (The request stacking driver should stop dispatching request)
2518 */
2519int blk_lld_busy(struct request_queue *q)
2520{
2521        if (q->lld_busy_fn)
2522                return q->lld_busy_fn(q);
2523
2524        return 0;
2525}
2526EXPORT_SYMBOL_GPL(blk_lld_busy);
2527
2528/**
2529 * blk_rq_unprep_clone - Helper function to free all bios in a cloned request
2530 * @rq: the clone request to be cleaned up
2531 *
2532 * Description:
2533 *     Free all bios in @rq for a cloned request.
2534 */
2535void blk_rq_unprep_clone(struct request *rq)
2536{
2537        struct bio *bio;
2538
2539        while ((bio = rq->bio) != NULL) {
2540                rq->bio = bio->bi_next;
2541
2542                bio_put(bio);
2543        }
2544}
2545EXPORT_SYMBOL_GPL(blk_rq_unprep_clone);
2546
2547/*
2548 * Copy attributes of the original request to the clone request.
2549 * The actual data parts (e.g. ->cmd, ->buffer, ->sense) are not copied.
2550 */
2551static void __blk_rq_prep_clone(struct request *dst, struct request *src)
2552{
2553        dst->cpu = src->cpu;
2554        dst->cmd_flags = (src->cmd_flags & REQ_CLONE_MASK) | REQ_NOMERGE;
2555        dst->cmd_type = src->cmd_type;
2556        dst->__sector = blk_rq_pos(src);
2557        dst->__data_len = blk_rq_bytes(src);
2558        dst->nr_phys_segments = src->nr_phys_segments;
2559        dst->ioprio = src->ioprio;
2560        dst->extra_len = src->extra_len;
2561}
2562
2563/**
2564 * blk_rq_prep_clone - Helper function to setup clone request
2565 * @rq: the request to be setup
2566 * @rq_src: original request to be cloned
2567 * @bs: bio_set that bios for clone are allocated from
2568 * @gfp_mask: memory allocation mask for bio
2569 * @bio_ctr: setup function to be called for each clone bio.
2570 *           Returns %0 for success, non %0 for failure.
2571 * @data: private data to be passed to @bio_ctr
2572 *
2573 * Description:
2574 *     Clones bios in @rq_src to @rq, and copies attributes of @rq_src to @rq.
2575 *     The actual data parts of @rq_src (e.g. ->cmd, ->buffer, ->sense)
2576 *     are not copied, and copying such parts is the caller's responsibility.
2577 *     Also, pages which the original bios are pointing to are not copied
2578 *     and the cloned bios just point same pages.
2579 *     So cloned bios must be completed before original bios, which means
2580 *     the caller must complete @rq before @rq_src.
2581 */
2582int blk_rq_prep_clone(struct request *rq, struct request *rq_src,
2583                      struct bio_set *bs, gfp_t gfp_mask,
2584                      int (*bio_ctr)(struct bio *, struct bio *, void *),
2585                      void *data)
2586{
2587        struct bio *bio, *bio_src;
2588
2589        if (!bs)
2590                bs = fs_bio_set;
2591
2592        blk_rq_init(NULL, rq);
2593
2594        __rq_for_each_bio(bio_src, rq_src) {
2595                bio = bio_alloc_bioset(gfp_mask, bio_src->bi_max_vecs, bs);
2596                if (!bio)
2597                        goto free_and_out;
2598
2599                __bio_clone(bio, bio_src);
2600
2601                if (bio_integrity(bio_src) &&
2602                    bio_integrity_clone(bio, bio_src, gfp_mask, bs))
2603                        goto free_and_out;
2604
2605                if (bio_ctr && bio_ctr(bio, bio_src, data))
2606                        goto free_and_out;
2607
2608                if (rq->bio) {
2609                        rq->biotail->bi_next = bio;
2610                        rq->biotail = bio;
2611                } else
2612                        rq->bio = rq->biotail = bio;
2613        }
2614
2615        __blk_rq_prep_clone(rq, rq_src);
2616
2617        return 0;
2618
2619free_and_out:
2620        if (bio)
2621                bio_free(bio, bs);
2622        blk_rq_unprep_clone(rq);
2623
2624        return -ENOMEM;
2625}
2626EXPORT_SYMBOL_GPL(blk_rq_prep_clone);
2627
2628int kblockd_schedule_work(struct request_queue *q, struct work_struct *work)
2629{
2630        return queue_work(kblockd_workqueue, work);
2631}
2632EXPORT_SYMBOL(kblockd_schedule_work);
2633
2634int kblockd_schedule_delayed_work(struct request_queue *q,
2635                        struct delayed_work *dwork, unsigned long delay)
2636{
2637        return queue_delayed_work(kblockd_workqueue, dwork, delay);
2638}
2639EXPORT_SYMBOL(kblockd_schedule_delayed_work);
2640
2641#define PLUG_MAGIC      0x91827364
2642
2643void blk_start_plug(struct blk_plug *plug)
2644{
2645        struct task_struct *tsk = current;
2646
2647        plug->magic = PLUG_MAGIC;
2648        INIT_LIST_HEAD(&plug->list);
2649        INIT_LIST_HEAD(&plug->cb_list);
2650        plug->should_sort = 0;
2651
2652        /*
2653         * If this is a nested plug, don't actually assign it. It will be
2654         * flushed on its own.
2655         */
2656        if (!tsk->plug) {
2657                /*
2658                 * Store ordering should not be needed here, since a potential
2659                 * preempt will imply a full memory barrier
2660                 */
2661                tsk->plug = plug;
2662        }
2663}
2664EXPORT_SYMBOL(blk_start_plug);
2665
2666static int plug_rq_cmp(void *priv, struct list_head *a, struct list_head *b)
2667{
2668        struct request *rqa = container_of(a, struct request, queuelist);
2669        struct request *rqb = container_of(b, struct request, queuelist);
2670
2671        return !(rqa->q <= rqb->q);
2672}
2673
2674/*
2675 * If 'from_schedule' is true, then postpone the dispatch of requests
2676 * until a safe kblockd context. We due this to avoid accidental big
2677 * additional stack usage in driver dispatch, in places where the originally
2678 * plugger did not intend it.
2679 */
2680static void queue_unplugged(struct request_queue *q, unsigned int depth,
2681                            bool from_schedule)
2682        __releases(q->queue_lock)
2683{
2684        trace_block_unplug(q, depth, !from_schedule);
2685
2686        /*
2687         * If we are punting this to kblockd, then we can safely drop
2688         * the queue_lock before waking kblockd (which needs to take
2689         * this lock).
2690         */
2691        if (from_schedule) {
2692                spin_unlock(q->queue_lock);
2693                blk_run_queue_async(q);
2694        } else {
2695                __blk_run_queue(q);
2696                spin_unlock(q->queue_lock);
2697        }
2698
2699}
2700
2701static void flush_plug_callbacks(struct blk_plug *plug)
2702{
2703        LIST_HEAD(callbacks);
2704
2705        if (list_empty(&plug->cb_list))
2706                return;
2707
2708        list_splice_init(&plug->cb_list, &callbacks);
2709
2710        while (!list_empty(&callbacks)) {
2711                struct blk_plug_cb *cb = list_first_entry(&callbacks,
2712                                                          struct blk_plug_cb,
2713                                                          list);
2714                list_del(&cb->list);
2715                cb->callback(cb);
2716        }
2717}
2718
2719void blk_flush_plug_list(struct blk_plug *plug, bool from_schedule)
2720{
2721        struct request_queue *q;
2722        unsigned long flags;
2723        struct request *rq;
2724        LIST_HEAD(list);
2725        unsigned int depth;
2726
2727        BUG_ON(plug->magic != PLUG_MAGIC);
2728
2729        flush_plug_callbacks(plug);
2730        if (list_empty(&plug->list))
2731                return;
2732
2733        list_splice_init(&plug->list, &list);
2734
2735        if (plug->should_sort) {
2736                list_sort(NULL, &list, plug_rq_cmp);
2737                plug->should_sort = 0;
2738        }
2739
2740        q = NULL;
2741        depth = 0;
2742
2743        /*
2744         * Save and disable interrupts here, to avoid doing it for every
2745         * queue lock we have to take.
2746         */
2747        local_irq_save(flags);
2748        while (!list_empty(&list)) {
2749                rq = list_entry_rq(list.next);
2750                list_del_init(&rq->queuelist);
2751                BUG_ON(!(rq->cmd_flags & REQ_ON_PLUG));
2752                BUG_ON(!rq->q);
2753                if (rq->q != q) {
2754                        /*
2755                         * This drops the queue lock
2756                         */
2757                        if (q)
2758                                queue_unplugged(q, depth, from_schedule);
2759                        q = rq->q;
2760                        depth = 0;
2761                        spin_lock(q->queue_lock);
2762                }
2763                rq->cmd_flags &= ~REQ_ON_PLUG;
2764
2765                /*
2766                 * rq is already accounted, so use raw insert
2767                 */
2768                if (rq->cmd_flags & (REQ_FLUSH | REQ_FUA))
2769                        __elv_add_request(q, rq, ELEVATOR_INSERT_FLUSH);
2770                else
2771                        __elv_add_request(q, rq, ELEVATOR_INSERT_SORT_MERGE);
2772
2773                depth++;
2774        }
2775
2776        /*
2777         * This drops the queue lock
2778         */
2779        if (q)
2780                queue_unplugged(q, depth, from_schedule);
2781
2782        local_irq_restore(flags);
2783}
2784
2785void blk_finish_plug(struct blk_plug *plug)
2786{
2787        blk_flush_plug_list(plug, false);
2788
2789        if (plug == current->plug)
2790                current->plug = NULL;
2791}
2792EXPORT_SYMBOL(blk_finish_plug);
2793
2794int __init blk_dev_init(void)
2795{
2796        BUILD_BUG_ON(__REQ_NR_BITS > 8 *
2797                        sizeof(((struct request *)0)->cmd_flags));
2798
2799        /* used for unplugging and affects IO latency/throughput - HIGHPRI */
2800        kblockd_workqueue = alloc_workqueue("kblockd",
2801                                            WQ_MEM_RECLAIM | WQ_HIGHPRI, 0);
2802        if (!kblockd_workqueue)
2803                panic("Failed to create kblockd\n");
2804
2805        request_cachep = kmem_cache_create("blkdev_requests",
2806                        sizeof(struct request), 0, SLAB_PANIC, NULL);
2807
2808        blk_requestq_cachep = kmem_cache_create("blkdev_queue",
2809                        sizeof(struct request_queue), 0, SLAB_PANIC, NULL);
2810
2811        return 0;
2812}
2813
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