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#include <linux/delay.h>
  32#include <linux/ratelimit.h>
  33
  34#define CREATE_TRACE_POINTS
  35#include <trace/events/block.h>
  36
  37#include "blk.h"
  38#include "blk-cgroup.h"
  39
  40EXPORT_TRACEPOINT_SYMBOL_GPL(block_bio_remap);
  41EXPORT_TRACEPOINT_SYMBOL_GPL(block_rq_remap);
  42EXPORT_TRACEPOINT_SYMBOL_GPL(block_bio_complete);
  43
  44DEFINE_IDA(blk_queue_ida);
  45
  46/*
  47 * For the allocated request tables
  48 */
  49static struct kmem_cache *request_cachep;
  50
  51/*
  52 * For queue allocation
  53 */
  54struct kmem_cache *blk_requestq_cachep;
  55
  56/*
  57 * Controlling structure to kblockd
  58 */
  59static struct workqueue_struct *kblockd_workqueue;
  60
  61static void drive_stat_acct(struct request *rq, int new_io)
  62{
  63        struct hd_struct *part;
  64        int rw = rq_data_dir(rq);
  65        int cpu;
  66
  67        if (!blk_do_io_stat(rq))
  68                return;
  69
  70        cpu = part_stat_lock();
  71
  72        if (!new_io) {
  73                part = rq->part;
  74                part_stat_inc(cpu, part, merges[rw]);
  75        } else {
  76                part = disk_map_sector_rcu(rq->rq_disk, blk_rq_pos(rq));
  77                if (!hd_struct_try_get(part)) {
  78                        /*
  79                         * The partition is already being removed,
  80                         * the request will be accounted on the disk only
  81                         *
  82                         * We take a reference on disk->part0 although that
  83                         * partition will never be deleted, so we can treat
  84                         * it as any other partition.
  85                         */
  86                        part = &rq->rq_disk->part0;
  87                        hd_struct_get(part);
  88                }
  89                part_round_stats(cpu, part);
  90                part_inc_in_flight(part, rw);
  91                rq->part = part;
  92        }
  93
  94        part_stat_unlock();
  95}
  96
  97void blk_queue_congestion_threshold(struct request_queue *q)
  98{
  99        int nr;
 100
 101        nr = q->nr_requests - (q->nr_requests / 8) + 1;
 102        if (nr > q->nr_requests)
 103                nr = q->nr_requests;
 104        q->nr_congestion_on = nr;
 105
 106        nr = q->nr_requests - (q->nr_requests / 8) - (q->nr_requests / 16) - 1;
 107        if (nr < 1)
 108                nr = 1;
 109        q->nr_congestion_off = nr;
 110}
 111
 112/**
 113 * blk_get_backing_dev_info - get the address of a queue's backing_dev_info
 114 * @bdev:       device
 115 *
 116 * Locates the passed device's request queue and returns the address of its
 117 * backing_dev_info
 118 *
 119 * Will return NULL if the request queue cannot be located.
 120 */
 121struct backing_dev_info *blk_get_backing_dev_info(struct block_device *bdev)
 122{
 123        struct backing_dev_info *ret = NULL;
 124        struct request_queue *q = bdev_get_queue(bdev);
 125
 126        if (q)
 127                ret = &q->backing_dev_info;
 128        return ret;
 129}
 130EXPORT_SYMBOL(blk_get_backing_dev_info);
 131
 132void blk_rq_init(struct request_queue *q, struct request *rq)
 133{
 134        memset(rq, 0, sizeof(*rq));
 135
 136        INIT_LIST_HEAD(&rq->queuelist);
 137        INIT_LIST_HEAD(&rq->timeout_list);
 138        rq->cpu = -1;
 139        rq->q = q;
 140        rq->__sector = (sector_t) -1;
 141        INIT_HLIST_NODE(&rq->hash);
 142        RB_CLEAR_NODE(&rq->rb_node);
 143        rq->cmd = rq->__cmd;
 144        rq->cmd_len = BLK_MAX_CDB;
 145        rq->tag = -1;
 146        rq->ref_count = 1;
 147        rq->start_time = jiffies;
 148        set_start_time_ns(rq);
 149        rq->part = NULL;
 150}
 151EXPORT_SYMBOL(blk_rq_init);
 152
 153static void req_bio_endio(struct request *rq, struct bio *bio,
 154                          unsigned int nbytes, int error)
 155{
 156        if (error)
 157                clear_bit(BIO_UPTODATE, &bio->bi_flags);
 158        else if (!test_bit(BIO_UPTODATE, &bio->bi_flags))
 159                error = -EIO;
 160
 161        if (unlikely(nbytes > bio->bi_size)) {
 162                printk(KERN_ERR "%s: want %u bytes done, %u left\n",
 163                       __func__, nbytes, bio->bi_size);
 164                nbytes = bio->bi_size;
 165        }
 166
 167        if (unlikely(rq->cmd_flags & REQ_QUIET))
 168                set_bit(BIO_QUIET, &bio->bi_flags);
 169
 170        bio->bi_size -= nbytes;
 171        bio->bi_sector += (nbytes >> 9);
 172
 173        if (bio_integrity(bio))
 174                bio_integrity_advance(bio, nbytes);
 175
 176        /* don't actually finish bio if it's part of flush sequence */
 177        if (bio->bi_size == 0 && !(rq->cmd_flags & REQ_FLUSH_SEQ))
 178                bio_endio(bio, error);
 179}
 180
 181void blk_dump_rq_flags(struct request *rq, char *msg)
 182{
 183        int bit;
 184
 185        printk(KERN_INFO "%s: dev %s: type=%x, flags=%x\n", msg,
 186                rq->rq_disk ? rq->rq_disk->disk_name : "?", rq->cmd_type,
 187                rq->cmd_flags);
 188
 189        printk(KERN_INFO "  sector %llu, nr/cnr %u/%u\n",
 190               (unsigned long long)blk_rq_pos(rq),
 191               blk_rq_sectors(rq), blk_rq_cur_sectors(rq));
 192        printk(KERN_INFO "  bio %p, biotail %p, buffer %p, len %u\n",
 193               rq->bio, rq->biotail, rq->buffer, blk_rq_bytes(rq));
 194
 195        if (rq->cmd_type == REQ_TYPE_BLOCK_PC) {
 196                printk(KERN_INFO "  cdb: ");
 197                for (bit = 0; bit < BLK_MAX_CDB; bit++)
 198                        printk("%02x ", rq->cmd[bit]);
 199                printk("\n");
 200        }
 201}
 202EXPORT_SYMBOL(blk_dump_rq_flags);
 203
 204static void blk_delay_work(struct work_struct *work)
 205{
 206        struct request_queue *q;
 207
 208        q = container_of(work, struct request_queue, delay_work.work);
 209        spin_lock_irq(q->queue_lock);
 210        __blk_run_queue(q);
 211        spin_unlock_irq(q->queue_lock);
 212}
 213
 214/**
 215 * blk_delay_queue - restart queueing after defined interval
 216 * @q:          The &struct request_queue in question
 217 * @msecs:      Delay in msecs
 218 *
 219 * Description:
 220 *   Sometimes queueing needs to be postponed for a little while, to allow
 221 *   resources to come back. This function will make sure that queueing is
 222 *   restarted around the specified time.
 223 */
 224void blk_delay_queue(struct request_queue *q, unsigned long msecs)
 225{
 226        queue_delayed_work(kblockd_workqueue, &q->delay_work,
 227                                msecs_to_jiffies(msecs));
 228}
 229EXPORT_SYMBOL(blk_delay_queue);
 230
 231/**
 232 * blk_start_queue - restart a previously stopped queue
 233 * @q:    The &struct request_queue in question
 234 *
 235 * Description:
 236 *   blk_start_queue() will clear the stop flag on the queue, and call
 237 *   the request_fn for the queue if it was in a stopped state when
 238 *   entered. Also see blk_stop_queue(). Queue lock must be held.
 239 **/
 240void blk_start_queue(struct request_queue *q)
 241{
 242        WARN_ON(!irqs_disabled());
 243
 244        queue_flag_clear(QUEUE_FLAG_STOPPED, q);
 245        __blk_run_queue(q);
 246}
 247EXPORT_SYMBOL(blk_start_queue);
 248
 249/**
 250 * blk_stop_queue - stop a queue
 251 * @q:    The &struct request_queue in question
 252 *
 253 * Description:
 254 *   The Linux block layer assumes that a block driver will consume all
 255 *   entries on the request queue when the request_fn strategy is called.
 256 *   Often this will not happen, because of hardware limitations (queue
 257 *   depth settings). If a device driver gets a 'queue full' response,
 258 *   or if it simply chooses not to queue more I/O at one point, it can
 259 *   call this function to prevent the request_fn from being called until
 260 *   the driver has signalled it's ready to go again. This happens by calling
 261 *   blk_start_queue() to restart queue operations. Queue lock must be held.
 262 **/
 263void blk_stop_queue(struct request_queue *q)
 264{
 265        __cancel_delayed_work(&q->delay_work);
 266        queue_flag_set(QUEUE_FLAG_STOPPED, q);
 267}
 268EXPORT_SYMBOL(blk_stop_queue);
 269
 270/**
 271 * blk_sync_queue - cancel any pending callbacks on a queue
 272 * @q: the queue
 273 *
 274 * Description:
 275 *     The block layer may perform asynchronous callback activity
 276 *     on a queue, such as calling the unplug function after a timeout.
 277 *     A block device may call blk_sync_queue to ensure that any
 278 *     such activity is cancelled, thus allowing it to release resources
 279 *     that the callbacks might use. The caller must already have made sure
 280 *     that its ->make_request_fn will not re-add plugging prior to calling
 281 *     this function.
 282 *
 283 *     This function does not cancel any asynchronous activity arising
 284 *     out of elevator or throttling code. That would require elevaotor_exit()
 285 *     and blkcg_exit_queue() to be called with queue lock initialized.
 286 *
 287 */
 288void blk_sync_queue(struct request_queue *q)
 289{
 290        del_timer_sync(&q->timeout);
 291        cancel_delayed_work_sync(&q->delay_work);
 292}
 293EXPORT_SYMBOL(blk_sync_queue);
 294
 295/**
 296 * __blk_run_queue - run a single device queue
 297 * @q:  The queue to run
 298 *
 299 * Description:
 300 *    See @blk_run_queue. This variant must be called with the queue lock
 301 *    held and interrupts disabled.
 302 */
 303void __blk_run_queue(struct request_queue *q)
 304{
 305        if (unlikely(blk_queue_stopped(q)))
 306                return;
 307
 308        q->request_fn(q);
 309}
 310EXPORT_SYMBOL(__blk_run_queue);
 311
 312/**
 313 * blk_run_queue_async - run a single device queue in workqueue context
 314 * @q:  The queue to run
 315 *
 316 * Description:
 317 *    Tells kblockd to perform the equivalent of @blk_run_queue on behalf
 318 *    of us.
 319 */
 320void blk_run_queue_async(struct request_queue *q)
 321{
 322        if (likely(!blk_queue_stopped(q))) {
 323                __cancel_delayed_work(&q->delay_work);
 324                queue_delayed_work(kblockd_workqueue, &q->delay_work, 0);
 325        }
 326}
 327EXPORT_SYMBOL(blk_run_queue_async);
 328
 329/**
 330 * blk_run_queue - run a single device queue
 331 * @q: The queue to run
 332 *
 333 * Description:
 334 *    Invoke request handling on this queue, if it has pending work to do.
 335 *    May be used to restart queueing when a request has completed.
 336 */
 337void blk_run_queue(struct request_queue *q)
 338{
 339        unsigned long flags;
 340
 341        spin_lock_irqsave(q->queue_lock, flags);
 342        __blk_run_queue(q);
 343        spin_unlock_irqrestore(q->queue_lock, flags);
 344}
 345EXPORT_SYMBOL(blk_run_queue);
 346
 347void blk_put_queue(struct request_queue *q)
 348{
 349        kobject_put(&q->kobj);
 350}
 351EXPORT_SYMBOL(blk_put_queue);
 352
 353/**
 354 * blk_drain_queue - drain requests from request_queue
 355 * @q: queue to drain
 356 * @drain_all: whether to drain all requests or only the ones w/ ELVPRIV
 357 *
 358 * Drain requests from @q.  If @drain_all is set, all requests are drained.
 359 * If not, only ELVPRIV requests are drained.  The caller is responsible
 360 * for ensuring that no new requests which need to be drained are queued.
 361 */
 362void blk_drain_queue(struct request_queue *q, bool drain_all)
 363{
 364        int i;
 365
 366        while (true) {
 367                bool drain = false;
 368
 369                spin_lock_irq(q->queue_lock);
 370
 371                /*
 372                 * The caller might be trying to drain @q before its
 373                 * elevator is initialized.
 374                 */
 375                if (q->elevator)
 376                        elv_drain_elevator(q);
 377
 378                blkcg_drain_queue(q);
 379
 380                /*
 381                 * This function might be called on a queue which failed
 382                 * driver init after queue creation or is not yet fully
 383                 * active yet.  Some drivers (e.g. fd and loop) get unhappy
 384                 * in such cases.  Kick queue iff dispatch queue has
 385                 * something on it and @q has request_fn set.
 386                 */
 387                if (!list_empty(&q->queue_head) && q->request_fn)
 388                        __blk_run_queue(q);
 389
 390                drain |= q->rq.elvpriv;
 391
 392                /*
 393                 * Unfortunately, requests are queued at and tracked from
 394                 * multiple places and there's no single counter which can
 395                 * be drained.  Check all the queues and counters.
 396                 */
 397                if (drain_all) {
 398                        drain |= !list_empty(&q->queue_head);
 399                        for (i = 0; i < 2; i++) {
 400                                drain |= q->rq.count[i];
 401                                drain |= q->in_flight[i];
 402                                drain |= !list_empty(&q->flush_queue[i]);
 403                        }
 404                }
 405
 406                spin_unlock_irq(q->queue_lock);
 407
 408                if (!drain)
 409                        break;
 410                msleep(10);
 411        }
 412
 413        /*
 414         * With queue marked dead, any woken up waiter will fail the
 415         * allocation path, so the wakeup chaining is lost and we're
 416         * left with hung waiters. We need to wake up those waiters.
 417         */
 418        if (q->request_fn) {
 419                spin_lock_irq(q->queue_lock);
 420                for (i = 0; i < ARRAY_SIZE(q->rq.wait); i++)
 421                        wake_up_all(&q->rq.wait[i]);
 422                spin_unlock_irq(q->queue_lock);
 423        }
 424}
 425
 426/**
 427 * blk_queue_bypass_start - enter queue bypass mode
 428 * @q: queue of interest
 429 *
 430 * In bypass mode, only the dispatch FIFO queue of @q is used.  This
 431 * function makes @q enter bypass mode and drains all requests which were
 432 * throttled or issued before.  On return, it's guaranteed that no request
 433 * is being throttled or has ELVPRIV set and blk_queue_bypass() %true
 434 * inside queue or RCU read lock.
 435 */
 436void blk_queue_bypass_start(struct request_queue *q)
 437{
 438        bool drain;
 439
 440        spin_lock_irq(q->queue_lock);
 441        drain = !q->bypass_depth++;
 442        queue_flag_set(QUEUE_FLAG_BYPASS, q);
 443        spin_unlock_irq(q->queue_lock);
 444
 445        if (drain) {
 446                blk_drain_queue(q, false);
 447                /* ensure blk_queue_bypass() is %true inside RCU read lock */
 448                synchronize_rcu();
 449        }
 450}
 451EXPORT_SYMBOL_GPL(blk_queue_bypass_start);
 452
 453/**
 454 * blk_queue_bypass_end - leave queue bypass mode
 455 * @q: queue of interest
 456 *
 457 * Leave bypass mode and restore the normal queueing behavior.
 458 */
 459void blk_queue_bypass_end(struct request_queue *q)
 460{
 461        spin_lock_irq(q->queue_lock);
 462        if (!--q->bypass_depth)
 463                queue_flag_clear(QUEUE_FLAG_BYPASS, q);
 464        WARN_ON_ONCE(q->bypass_depth < 0);
 465        spin_unlock_irq(q->queue_lock);
 466}
 467EXPORT_SYMBOL_GPL(blk_queue_bypass_end);
 468
 469/**
 470 * blk_cleanup_queue - shutdown a request queue
 471 * @q: request queue to shutdown
 472 *
 473 * Mark @q DEAD, drain all pending requests, destroy and put it.  All
 474 * future requests will be failed immediately with -ENODEV.
 475 */
 476void blk_cleanup_queue(struct request_queue *q)
 477{
 478        spinlock_t *lock = q->queue_lock;
 479
 480        /* mark @q DEAD, no new request or merges will be allowed afterwards */
 481        mutex_lock(&q->sysfs_lock);
 482        queue_flag_set_unlocked(QUEUE_FLAG_DEAD, q);
 483        spin_lock_irq(lock);
 484
 485        /*
 486         * Dead queue is permanently in bypass mode till released.  Note
 487         * that, unlike blk_queue_bypass_start(), we aren't performing
 488         * synchronize_rcu() after entering bypass mode to avoid the delay
 489         * as some drivers create and destroy a lot of queues while
 490         * probing.  This is still safe because blk_release_queue() will be
 491         * called only after the queue refcnt drops to zero and nothing,
 492         * RCU or not, would be traversing the queue by then.
 493         */
 494        q->bypass_depth++;
 495        queue_flag_set(QUEUE_FLAG_BYPASS, q);
 496
 497        queue_flag_set(QUEUE_FLAG_NOMERGES, q);
 498        queue_flag_set(QUEUE_FLAG_NOXMERGES, q);
 499        queue_flag_set(QUEUE_FLAG_DEAD, q);
 500        spin_unlock_irq(lock);
 501        mutex_unlock(&q->sysfs_lock);
 502
 503        /* drain all requests queued before DEAD marking */
 504        blk_drain_queue(q, true);
 505
 506        /* @q won't process any more request, flush async actions */
 507        del_timer_sync(&q->backing_dev_info.laptop_mode_wb_timer);
 508        blk_sync_queue(q);
 509
 510        spin_lock_irq(lock);
 511        if (q->queue_lock != &q->__queue_lock)
 512                q->queue_lock = &q->__queue_lock;
 513        spin_unlock_irq(lock);
 514
 515        /* @q is and will stay empty, shutdown and put */
 516        blk_put_queue(q);
 517}
 518EXPORT_SYMBOL(blk_cleanup_queue);
 519
 520static int blk_init_free_list(struct request_queue *q)
 521{
 522        struct request_list *rl = &q->rq;
 523
 524        if (unlikely(rl->rq_pool))
 525                return 0;
 526
 527        rl->count[BLK_RW_SYNC] = rl->count[BLK_RW_ASYNC] = 0;
 528        rl->starved[BLK_RW_SYNC] = rl->starved[BLK_RW_ASYNC] = 0;
 529        rl->elvpriv = 0;
 530        init_waitqueue_head(&rl->wait[BLK_RW_SYNC]);
 531        init_waitqueue_head(&rl->wait[BLK_RW_ASYNC]);
 532
 533        rl->rq_pool = mempool_create_node(BLKDEV_MIN_RQ, mempool_alloc_slab,
 534                                mempool_free_slab, request_cachep, q->node);
 535
 536        if (!rl->rq_pool)
 537                return -ENOMEM;
 538
 539        return 0;
 540}
 541
 542struct request_queue *blk_alloc_queue(gfp_t gfp_mask)
 543{
 544        return blk_alloc_queue_node(gfp_mask, -1);
 545}
 546EXPORT_SYMBOL(blk_alloc_queue);
 547
 548struct request_queue *blk_alloc_queue_node(gfp_t gfp_mask, int node_id)
 549{
 550        struct request_queue *q;
 551        int err;
 552
 553        q = kmem_cache_alloc_node(blk_requestq_cachep,
 554                                gfp_mask | __GFP_ZERO, node_id);
 555        if (!q)
 556                return NULL;
 557
 558        q->id = ida_simple_get(&blk_queue_ida, 0, 0, gfp_mask);
 559        if (q->id < 0)
 560                goto fail_q;
 561
 562        q->backing_dev_info.ra_pages =
 563                        (VM_MAX_READAHEAD * 1024) / PAGE_CACHE_SIZE;
 564        q->backing_dev_info.state = 0;
 565        q->backing_dev_info.capabilities = BDI_CAP_MAP_COPY;
 566        q->backing_dev_info.name = "block";
 567        q->node = node_id;
 568
 569        err = bdi_init(&q->backing_dev_info);
 570        if (err)
 571                goto fail_id;
 572
 573        setup_timer(&q->backing_dev_info.laptop_mode_wb_timer,
 574                    laptop_mode_timer_fn, (unsigned long) q);
 575        setup_timer(&q->timeout, blk_rq_timed_out_timer, (unsigned long) q);
 576        INIT_LIST_HEAD(&q->queue_head);
 577        INIT_LIST_HEAD(&q->timeout_list);
 578        INIT_LIST_HEAD(&q->icq_list);
 579#ifdef CONFIG_BLK_CGROUP
 580        INIT_LIST_HEAD(&q->blkg_list);
 581#endif
 582        INIT_LIST_HEAD(&q->flush_queue[0]);
 583        INIT_LIST_HEAD(&q->flush_queue[1]);
 584        INIT_LIST_HEAD(&q->flush_data_in_flight);
 585        INIT_DELAYED_WORK(&q->delay_work, blk_delay_work);
 586
 587        kobject_init(&q->kobj, &blk_queue_ktype);
 588
 589        mutex_init(&q->sysfs_lock);
 590        spin_lock_init(&q->__queue_lock);
 591
 592        /*
 593         * By default initialize queue_lock to internal lock and driver can
 594         * override it later if need be.
 595         */
 596        q->queue_lock = &q->__queue_lock;
 597
 598        /*
 599         * A queue starts its life with bypass turned on to avoid
 600         * unnecessary bypass on/off overhead and nasty surprises during
 601         * init.  The initial bypass will be finished at the end of
 602         * blk_init_allocated_queue().
 603         */
 604        q->bypass_depth = 1;
 605        __set_bit(QUEUE_FLAG_BYPASS, &q->queue_flags);
 606
 607        if (blkcg_init_queue(q))
 608                goto fail_id;
 609
 610        return q;
 611
 612fail_id:
 613        ida_simple_remove(&blk_queue_ida, q->id);
 614fail_q:
 615        kmem_cache_free(blk_requestq_cachep, q);
 616        return NULL;
 617}
 618EXPORT_SYMBOL(blk_alloc_queue_node);
 619
 620/**
 621 * blk_init_queue  - prepare a request queue for use with a block device
 622 * @rfn:  The function to be called to process requests that have been
 623 *        placed on the queue.
 624 * @lock: Request queue spin lock
 625 *
 626 * Description:
 627 *    If a block device wishes to use the standard request handling procedures,
 628 *    which sorts requests and coalesces adjacent requests, then it must
 629 *    call blk_init_queue().  The function @rfn will be called when there
 630 *    are requests on the queue that need to be processed.  If the device
 631 *    supports plugging, then @rfn may not be called immediately when requests
 632 *    are available on the queue, but may be called at some time later instead.
 633 *    Plugged queues are generally unplugged when a buffer belonging to one
 634 *    of the requests on the queue is needed, or due to memory pressure.
 635 *
 636 *    @rfn is not required, or even expected, to remove all requests off the
 637 *    queue, but only as many as it can handle at a time.  If it does leave
 638 *    requests on the queue, it is responsible for arranging that the requests
 639 *    get dealt with eventually.
 640 *
 641 *    The queue spin lock must be held while manipulating the requests on the
 642 *    request queue; this lock will be taken also from interrupt context, so irq
 643 *    disabling is needed for it.
 644 *
 645 *    Function returns a pointer to the initialized request queue, or %NULL if
 646 *    it didn't succeed.
 647 *
 648 * Note:
 649 *    blk_init_queue() must be paired with a blk_cleanup_queue() call
 650 *    when the block device is deactivated (such as at module unload).
 651 **/
 652
 653struct request_queue *blk_init_queue(request_fn_proc *rfn, spinlock_t *lock)
 654{
 655        return blk_init_queue_node(rfn, lock, -1);
 656}
 657EXPORT_SYMBOL(blk_init_queue);
 658
 659struct request_queue *
 660blk_init_queue_node(request_fn_proc *rfn, spinlock_t *lock, int node_id)
 661{
 662        struct request_queue *uninit_q, *q;
 663
 664        uninit_q = blk_alloc_queue_node(GFP_KERNEL, node_id);
 665        if (!uninit_q)
 666                return NULL;
 667
 668        q = blk_init_allocated_queue(uninit_q, rfn, lock);
 669        if (!q)
 670                blk_cleanup_queue(uninit_q);
 671
 672        return q;
 673}
 674EXPORT_SYMBOL(blk_init_queue_node);
 675
 676struct request_queue *
 677blk_init_allocated_queue(struct request_queue *q, request_fn_proc *rfn,
 678                         spinlock_t *lock)
 679{
 680        if (!q)
 681                return NULL;
 682
 683        if (blk_init_free_list(q))
 684                return NULL;
 685
 686        q->request_fn           = rfn;
 687        q->prep_rq_fn           = NULL;
 688        q->unprep_rq_fn         = NULL;
 689        q->queue_flags          = QUEUE_FLAG_DEFAULT;
 690
 691        /* Override internal queue lock with supplied lock pointer */
 692        if (lock)
 693                q->queue_lock           = lock;
 694
 695        /*
 696         * This also sets hw/phys segments, boundary and size
 697         */
 698        blk_queue_make_request(q, blk_queue_bio);
 699
 700        q->sg_reserved_size = INT_MAX;
 701
 702        /* init elevator */
 703        if (elevator_init(q, NULL))
 704                return NULL;
 705
 706        blk_queue_congestion_threshold(q);
 707
 708        /* all done, end the initial bypass */
 709        blk_queue_bypass_end(q);
 710        return q;
 711}
 712EXPORT_SYMBOL(blk_init_allocated_queue);
 713
 714bool blk_get_queue(struct request_queue *q)
 715{
 716        if (likely(!blk_queue_dead(q))) {
 717                __blk_get_queue(q);
 718                return true;
 719        }
 720
 721        return false;
 722}
 723EXPORT_SYMBOL(blk_get_queue);
 724
 725static inline void blk_free_request(struct request_queue *q, struct request *rq)
 726{
 727        if (rq->cmd_flags & REQ_ELVPRIV) {
 728                elv_put_request(q, rq);
 729                if (rq->elv.icq)
 730                        put_io_context(rq->elv.icq->ioc);
 731        }
 732
 733        mempool_free(rq, q->rq.rq_pool);
 734}
 735
 736/*
 737 * ioc_batching returns true if the ioc is a valid batching request and
 738 * should be given priority access to a request.
 739 */
 740static inline int ioc_batching(struct request_queue *q, struct io_context *ioc)
 741{
 742        if (!ioc)
 743                return 0;
 744
 745        /*
 746         * Make sure the process is able to allocate at least 1 request
 747         * even if the batch times out, otherwise we could theoretically
 748         * lose wakeups.
 749         */
 750        return ioc->nr_batch_requests == q->nr_batching ||
 751                (ioc->nr_batch_requests > 0
 752                && time_before(jiffies, ioc->last_waited + BLK_BATCH_TIME));
 753}
 754
 755/*
 756 * ioc_set_batching sets ioc to be a new "batcher" if it is not one. This
 757 * will cause the process to be a "batcher" on all queues in the system. This
 758 * is the behaviour we want though - once it gets a wakeup it should be given
 759 * a nice run.
 760 */
 761static void ioc_set_batching(struct request_queue *q, struct io_context *ioc)
 762{
 763        if (!ioc || ioc_batching(q, ioc))
 764                return;
 765
 766        ioc->nr_batch_requests = q->nr_batching;
 767        ioc->last_waited = jiffies;
 768}
 769
 770static void __freed_request(struct request_queue *q, int sync)
 771{
 772        struct request_list *rl = &q->rq;
 773
 774        if (rl->count[sync] < queue_congestion_off_threshold(q))
 775                blk_clear_queue_congested(q, sync);
 776
 777        if (rl->count[sync] + 1 <= q->nr_requests) {
 778                if (waitqueue_active(&rl->wait[sync]))
 779                        wake_up(&rl->wait[sync]);
 780
 781                blk_clear_queue_full(q, sync);
 782        }
 783}
 784
 785/*
 786 * A request has just been released.  Account for it, update the full and
 787 * congestion status, wake up any waiters.   Called under q->queue_lock.
 788 */
 789static void freed_request(struct request_queue *q, unsigned int flags)
 790{
 791        struct request_list *rl = &q->rq;
 792        int sync = rw_is_sync(flags);
 793
 794        rl->count[sync]--;
 795        if (flags & REQ_ELVPRIV)
 796                rl->elvpriv--;
 797
 798        __freed_request(q, sync);
 799
 800        if (unlikely(rl->starved[sync ^ 1]))
 801                __freed_request(q, sync ^ 1);
 802}
 803
 804/*
 805 * Determine if elevator data should be initialized when allocating the
 806 * request associated with @bio.
 807 */
 808static bool blk_rq_should_init_elevator(struct bio *bio)
 809{
 810        if (!bio)
 811                return true;
 812
 813        /*
 814         * Flush requests do not use the elevator so skip initialization.
 815         * This allows a request to share the flush and elevator data.
 816         */
 817        if (bio->bi_rw & (REQ_FLUSH | REQ_FUA))
 818                return false;
 819
 820        return true;
 821}
 822
 823/**
 824 * rq_ioc - determine io_context for request allocation
 825 * @bio: request being allocated is for this bio (can be %NULL)
 826 *
 827 * Determine io_context to use for request allocation for @bio.  May return
 828 * %NULL if %current->io_context doesn't exist.
 829 */
 830static struct io_context *rq_ioc(struct bio *bio)
 831{
 832#ifdef CONFIG_BLK_CGROUP
 833        if (bio && bio->bi_ioc)
 834                return bio->bi_ioc;
 835#endif
 836        return current->io_context;
 837}
 838
 839/**
 840 * get_request - get a free request
 841 * @q: request_queue to allocate request from
 842 * @rw_flags: RW and SYNC flags
 843 * @bio: bio to allocate request for (can be %NULL)
 844 * @gfp_mask: allocation mask
 845 *
 846 * Get a free request from @q.  This function may fail under memory
 847 * pressure or if @q is dead.
 848 *
 849 * Must be callled with @q->queue_lock held and,
 850 * Returns %NULL on failure, with @q->queue_lock held.
 851 * Returns !%NULL on success, with @q->queue_lock *not held*.
 852 */
 853static struct request *get_request(struct request_queue *q, int rw_flags,
 854                                   struct bio *bio, gfp_t gfp_mask)
 855{
 856        struct request *rq;
 857        struct request_list *rl = &q->rq;
 858        struct elevator_type *et;
 859        struct io_context *ioc;
 860        struct io_cq *icq = NULL;
 861        const bool is_sync = rw_is_sync(rw_flags) != 0;
 862        bool retried = false;
 863        int may_queue;
 864retry:
 865        et = q->elevator->type;
 866        ioc = rq_ioc(bio);
 867
 868        if (unlikely(blk_queue_dead(q)))
 869                return NULL;
 870
 871        may_queue = elv_may_queue(q, rw_flags);
 872        if (may_queue == ELV_MQUEUE_NO)
 873                goto rq_starved;
 874
 875        if (rl->count[is_sync]+1 >= queue_congestion_on_threshold(q)) {
 876                if (rl->count[is_sync]+1 >= q->nr_requests) {
 877                        /*
 878                         * We want ioc to record batching state.  If it's
 879                         * not already there, creating a new one requires
 880                         * dropping queue_lock, which in turn requires
 881                         * retesting conditions to avoid queue hang.
 882                         */
 883                        if (!ioc && !retried) {
 884                                spin_unlock_irq(q->queue_lock);
 885                                create_io_context(gfp_mask, q->node);
 886                                spin_lock_irq(q->queue_lock);
 887                                retried = true;
 888                                goto retry;
 889                        }
 890
 891                        /*
 892                         * The queue will fill after this allocation, so set
 893                         * it as full, and mark this process as "batching".
 894                         * This process will be allowed to complete a batch of
 895                         * requests, others will be blocked.
 896                         */
 897                        if (!blk_queue_full(q, is_sync)) {
 898                                ioc_set_batching(q, ioc);
 899                                blk_set_queue_full(q, is_sync);
 900                        } else {
 901                                if (may_queue != ELV_MQUEUE_MUST
 902                                                && !ioc_batching(q, ioc)) {
 903                                        /*
 904                                         * The queue is full and the allocating
 905                                         * process is not a "batcher", and not
 906                                         * exempted by the IO scheduler
 907                                         */
 908                                        return NULL;
 909                                }
 910                        }
 911                }
 912                blk_set_queue_congested(q, is_sync);
 913        }
 914
 915        /*
 916         * Only allow batching queuers to allocate up to 50% over the defined
 917         * limit of requests, otherwise we could have thousands of requests
 918         * allocated with any setting of ->nr_requests
 919         */
 920        if (rl->count[is_sync] >= (3 * q->nr_requests / 2))
 921                return NULL;
 922
 923        rl->count[is_sync]++;
 924        rl->starved[is_sync] = 0;
 925
 926        /*
 927         * Decide whether the new request will be managed by elevator.  If
 928         * so, mark @rw_flags and increment elvpriv.  Non-zero elvpriv will
 929         * prevent the current elevator from being destroyed until the new
 930         * request is freed.  This guarantees icq's won't be destroyed and
 931         * makes creating new ones safe.
 932         *
 933         * Also, lookup icq while holding queue_lock.  If it doesn't exist,
 934         * it will be created after releasing queue_lock.
 935         */
 936        if (blk_rq_should_init_elevator(bio) && !blk_queue_bypass(q)) {
 937                rw_flags |= REQ_ELVPRIV;
 938                rl->elvpriv++;
 939                if (et->icq_cache && ioc)
 940                        icq = ioc_lookup_icq(ioc, q);
 941        }
 942
 943        if (blk_queue_io_stat(q))
 944                rw_flags |= REQ_IO_STAT;
 945        spin_unlock_irq(q->queue_lock);
 946
 947        /* allocate and init request */
 948        rq = mempool_alloc(q->rq.rq_pool, gfp_mask);
 949        if (!rq)
 950                goto fail_alloc;
 951
 952        blk_rq_init(q, rq);
 953        rq->cmd_flags = rw_flags | REQ_ALLOCED;
 954
 955        /* init elvpriv */
 956        if (rw_flags & REQ_ELVPRIV) {
 957                if (unlikely(et->icq_cache && !icq)) {
 958                        create_io_context(gfp_mask, q->node);
 959                        ioc = rq_ioc(bio);
 960                        if (!ioc)
 961                                goto fail_elvpriv;
 962
 963                        icq = ioc_create_icq(ioc, q, gfp_mask);
 964                        if (!icq)
 965                                goto fail_elvpriv;
 966                }
 967
 968                rq->elv.icq = icq;
 969                if (unlikely(elv_set_request(q, rq, bio, gfp_mask)))
 970                        goto fail_elvpriv;
 971
 972                /* @rq->elv.icq holds io_context until @rq is freed */
 973                if (icq)
 974                        get_io_context(icq->ioc);
 975        }
 976out:
 977        /*
 978         * ioc may be NULL here, and ioc_batching will be false. That's
 979         * OK, if the queue is under the request limit then requests need
 980         * not count toward the nr_batch_requests limit. There will always
 981         * be some limit enforced by BLK_BATCH_TIME.
 982         */
 983        if (ioc_batching(q, ioc))
 984                ioc->nr_batch_requests--;
 985
 986        trace_block_getrq(q, bio, rw_flags & 1);
 987        return rq;
 988
 989fail_elvpriv:
 990        /*
 991         * elvpriv init failed.  ioc, icq and elvpriv aren't mempool backed
 992         * and may fail indefinitely under memory pressure and thus
 993         * shouldn't stall IO.  Treat this request as !elvpriv.  This will
 994         * disturb iosched and blkcg but weird is bettern than dead.
 995         */
 996        printk_ratelimited(KERN_WARNING "%s: request aux data allocation failed, iosched may be disturbed\n",
 997                           dev_name(q->backing_dev_info.dev));
 998
 999        rq->cmd_flags &= ~REQ_ELVPRIV;
1000        rq->elv.icq = NULL;
1001
1002        spin_lock_irq(q->queue_lock);
1003        rl->elvpriv--;
1004        spin_unlock_irq(q->queue_lock);
1005        goto out;
1006
1007fail_alloc:
1008        /*
1009         * Allocation failed presumably due to memory. Undo anything we
1010         * might have messed up.
1011         *
1012         * Allocating task should really be put onto the front of the wait
1013         * queue, but this is pretty rare.
1014         */
1015        spin_lock_irq(q->queue_lock);
1016        freed_request(q, rw_flags);
1017
1018        /*
1019         * in the very unlikely event that allocation failed and no
1020         * requests for this direction was pending, mark us starved so that
1021         * freeing of a request in the other direction will notice
1022         * us. another possible fix would be to split the rq mempool into
1023         * READ and WRITE
1024         */
1025rq_starved:
1026        if (unlikely(rl->count[is_sync] == 0))
1027                rl->starved[is_sync] = 1;
1028        return NULL;
1029}
1030
1031/**
1032 * get_request_wait - get a free request with retry
1033 * @q: request_queue to allocate request from
1034 * @rw_flags: RW and SYNC flags
1035 * @bio: bio to allocate request for (can be %NULL)
1036 *
1037 * Get a free request from @q.  This function keeps retrying under memory
1038 * pressure and fails iff @q is dead.
1039 *
1040 * Must be callled with @q->queue_lock held and,
1041 * Returns %NULL on failure, with @q->queue_lock held.
1042 * Returns !%NULL on success, with @q->queue_lock *not held*.
1043 */
1044static struct request *get_request_wait(struct request_queue *q, int rw_flags,
1045                                        struct bio *bio)
1046{
1047        const bool is_sync = rw_is_sync(rw_flags) != 0;
1048        struct request *rq;
1049
1050        rq = get_request(q, rw_flags, bio, GFP_NOIO);
1051        while (!rq) {
1052                DEFINE_WAIT(wait);
1053                struct request_list *rl = &q->rq;
1054
1055                if (unlikely(blk_queue_dead(q)))
1056                        return NULL;
1057
1058                prepare_to_wait_exclusive(&rl->wait[is_sync], &wait,
1059                                TASK_UNINTERRUPTIBLE);
1060
1061                trace_block_sleeprq(q, bio, rw_flags & 1);
1062
1063                spin_unlock_irq(q->queue_lock);
1064                io_schedule();
1065
1066                /*
1067                 * After sleeping, we become a "batching" process and
1068                 * will be able to allocate at least one request, and
1069                 * up to a big batch of them for a small period time.
1070                 * See ioc_batching, ioc_set_batching
1071                 */
1072                create_io_context(GFP_NOIO, q->node);
1073                ioc_set_batching(q, current->io_context);
1074
1075                spin_lock_irq(q->queue_lock);
1076                finish_wait(&rl->wait[is_sync], &wait);
1077
1078                rq = get_request(q, rw_flags, bio, GFP_NOIO);
1079        };
1080
1081        return rq;
1082}
1083
1084struct request *blk_get_request(struct request_queue *q, int rw, gfp_t gfp_mask)
1085{
1086        struct request *rq;
1087
1088        BUG_ON(rw != READ && rw != WRITE);
1089
1090        spin_lock_irq(q->queue_lock);
1091        if (gfp_mask & __GFP_WAIT)
1092                rq = get_request_wait(q, rw, NULL);
1093        else
1094                rq = get_request(q, rw, NULL, gfp_mask);
1095        if (!rq)
1096                spin_unlock_irq(q->queue_lock);
1097        /* q->queue_lock is unlocked at this point */
1098
1099        return rq;
1100}
1101EXPORT_SYMBOL(blk_get_request);
1102
1103/**
1104 * blk_make_request - given a bio, allocate a corresponding struct request.
1105 * @q: target request queue
1106 * @bio:  The bio describing the memory mappings that will be submitted for IO.
1107 *        It may be a chained-bio properly constructed by block/bio layer.
1108 * @gfp_mask: gfp flags to be used for memory allocation
1109 *
1110 * blk_make_request is the parallel of generic_make_request for BLOCK_PC
1111 * type commands. Where the struct request needs to be farther initialized by
1112 * the caller. It is passed a &struct bio, which describes the memory info of
1113 * the I/O transfer.
1114 *
1115 * The caller of blk_make_request must make sure that bi_io_vec
1116 * are set to describe the memory buffers. That bio_data_dir() will return
1117 * the needed direction of the request. (And all bio's in the passed bio-chain
1118 * are properly set accordingly)
1119 *
1120 * If called under none-sleepable conditions, mapped bio buffers must not
1121 * need bouncing, by calling the appropriate masked or flagged allocator,
1122 * suitable for the target device. Otherwise the call to blk_queue_bounce will
1123 * BUG.
1124 *
1125 * WARNING: When allocating/cloning a bio-chain, careful consideration should be
1126 * given to how you allocate bios. In particular, you cannot use __GFP_WAIT for
1127 * anything but the first bio in the chain. Otherwise you risk waiting for IO
1128 * completion of a bio that hasn't been submitted yet, thus resulting in a
1129 * deadlock. Alternatively bios should be allocated using bio_kmalloc() instead
1130 * of bio_alloc(), as that avoids the mempool deadlock.
1131 * If possible a big IO should be split into smaller parts when allocation
1132 * fails. Partial allocation should not be an error, or you risk a live-lock.
1133 */
1134struct request *blk_make_request(struct request_queue *q, struct bio *bio,
1135                                 gfp_t gfp_mask)
1136{
1137        struct request *rq = blk_get_request(q, bio_data_dir(bio), gfp_mask);
1138
1139        if (unlikely(!rq))
1140                return ERR_PTR(-ENOMEM);
1141
1142        for_each_bio(bio) {
1143                struct bio *bounce_bio = bio;
1144                int ret;
1145
1146                blk_queue_bounce(q, &bounce_bio);
1147                ret = blk_rq_append_bio(q, rq, bounce_bio);
1148                if (unlikely(ret)) {
1149                        blk_put_request(rq);
1150                        return ERR_PTR(ret);
1151                }
1152        }
1153
1154        return rq;
1155}
1156EXPORT_SYMBOL(blk_make_request);
1157
1158/**
1159 * blk_requeue_request - put a request back on queue
1160 * @q:          request queue where request should be inserted
1161 * @rq:         request to be inserted
1162 *
1163 * Description:
1164 *    Drivers often keep queueing requests until the hardware cannot accept
1165 *    more, when that condition happens we need to put the request back
1166 *    on the queue. Must be called with queue lock held.
1167 */
1168void blk_requeue_request(struct request_queue *q, struct request *rq)
1169{
1170        blk_delete_timer(rq);
1171        blk_clear_rq_complete(rq);
1172        trace_block_rq_requeue(q, rq);
1173
1174        if (blk_rq_tagged(rq))
1175                blk_queue_end_tag(q, rq);
1176
1177        BUG_ON(blk_queued_rq(rq));
1178
1179        elv_requeue_request(q, rq);
1180}
1181EXPORT_SYMBOL(blk_requeue_request);
1182
1183static void add_acct_request(struct request_queue *q, struct request *rq,
1184                             int where)
1185{
1186        drive_stat_acct(rq, 1);
1187        __elv_add_request(q, rq, where);
1188}
1189
1190static void part_round_stats_single(int cpu, struct hd_struct *part,
1191                                    unsigned long now)
1192{
1193        if (now == part->stamp)
1194                return;
1195
1196        if (part_in_flight(part)) {
1197                __part_stat_add(cpu, part, time_in_queue,
1198                                part_in_flight(part) * (now - part->stamp));
1199                __part_stat_add(cpu, part, io_ticks, (now - part->stamp));
1200        }
1201        part->stamp = now;
1202}
1203
1204/**
1205 * part_round_stats() - Round off the performance stats on a struct disk_stats.
1206 * @cpu: cpu number for stats access
1207 * @part: target partition
1208 *
1209 * The average IO queue length and utilisation statistics are maintained
1210 * by observing the current state of the queue length and the amount of
1211 * time it has been in this state for.
1212 *
1213 * Normally, that accounting is done on IO completion, but that can result
1214 * in more than a second's worth of IO being accounted for within any one
1215 * second, leading to >100% utilisation.  To deal with that, we call this
1216 * function to do a round-off before returning the results when reading
1217 * /proc/diskstats.  This accounts immediately for all queue usage up to
1218 * the current jiffies and restarts the counters again.
1219 */
1220void part_round_stats(int cpu, struct hd_struct *part)
1221{
1222        unsigned long now = jiffies;
1223
1224        if (part->partno)
1225                part_round_stats_single(cpu, &part_to_disk(part)->part0, now);
1226        part_round_stats_single(cpu, part, now);
1227}
1228EXPORT_SYMBOL_GPL(part_round_stats);
1229
1230/*
1231 * queue lock must be held
1232 */
1233void __blk_put_request(struct request_queue *q, struct request *req)
1234{
1235        if (unlikely(!q))
1236                return;
1237        if (unlikely(--req->ref_count))
1238                return;
1239
1240        elv_completed_request(q, req);
1241
1242        /* this is a bio leak */
1243        WARN_ON(req->bio != NULL);
1244
1245        /*
1246         * Request may not have originated from ll_rw_blk. if not,
1247         * it didn't come out of our reserved rq pools
1248         */
1249        if (req->cmd_flags & REQ_ALLOCED) {
1250                unsigned int flags = req->cmd_flags;
1251
1252                BUG_ON(!list_empty(&req->queuelist));
1253                BUG_ON(!hlist_unhashed(&req->hash));
1254
1255                blk_free_request(q, req);
1256                freed_request(q, flags);
1257        }
1258}
1259EXPORT_SYMBOL_GPL(__blk_put_request);
1260
1261void blk_put_request(struct request *req)
1262{
1263        unsigned long flags;
1264        struct request_queue *q = req->q;
1265
1266        spin_lock_irqsave(q->queue_lock, flags);
1267        __blk_put_request(q, req);
1268        spin_unlock_irqrestore(q->queue_lock, flags);
1269}
1270EXPORT_SYMBOL(blk_put_request);
1271
1272/**
1273 * blk_add_request_payload - add a payload to a request
1274 * @rq: request to update
1275 * @page: page backing the payload
1276 * @len: length of the payload.
1277 *
1278 * This allows to later add a payload to an already submitted request by
1279 * a block driver.  The driver needs to take care of freeing the payload
1280 * itself.
1281 *
1282 * Note that this is a quite horrible hack and nothing but handling of
1283 * discard requests should ever use it.
1284 */
1285void blk_add_request_payload(struct request *rq, struct page *page,
1286                unsigned int len)
1287{
1288        struct bio *bio = rq->bio;
1289
1290        bio->bi_io_vec->bv_page = page;
1291        bio->bi_io_vec->bv_offset = 0;
1292        bio->bi_io_vec->bv_len = len;
1293
1294        bio->bi_size = len;
1295        bio->bi_vcnt = 1;
1296        bio->bi_phys_segments = 1;
1297
1298        rq->__data_len = rq->resid_len = len;
1299        rq->nr_phys_segments = 1;
1300        rq->buffer = bio_data(bio);
1301}
1302EXPORT_SYMBOL_GPL(blk_add_request_payload);
1303
1304static bool bio_attempt_back_merge(struct request_queue *q, struct request *req,
1305                                   struct bio *bio)
1306{
1307        const int ff = bio->bi_rw & REQ_FAILFAST_MASK;
1308
1309        if (!ll_back_merge_fn(q, req, bio))
1310                return false;
1311
1312        trace_block_bio_backmerge(q, bio);
1313
1314        if ((req->cmd_flags & REQ_FAILFAST_MASK) != ff)
1315                blk_rq_set_mixed_merge(req);
1316
1317        req->biotail->bi_next = bio;
1318        req->biotail = bio;
1319        req->__data_len += bio->bi_size;
1320        req->ioprio = ioprio_best(req->ioprio, bio_prio(bio));
1321
1322        drive_stat_acct(req, 0);
1323        return true;
1324}
1325
1326static bool bio_attempt_front_merge(struct request_queue *q,
1327                                    struct request *req, struct bio *bio)
1328{
1329        const int ff = bio->bi_rw & REQ_FAILFAST_MASK;
1330
1331        if (!ll_front_merge_fn(q, req, bio))
1332                return false;
1333
1334        trace_block_bio_frontmerge(q, bio);
1335
1336        if ((req->cmd_flags & REQ_FAILFAST_MASK) != ff)
1337                blk_rq_set_mixed_merge(req);
1338
1339        bio->bi_next = req->bio;
1340        req->bio = bio;
1341
1342        /*
1343         * may not be valid. if the low level driver said
1344         * it didn't need a bounce buffer then it better
1345         * not touch req->buffer either...
1346         */
1347        req->buffer = bio_data(bio);
1348        req->__sector = bio->bi_sector;
1349        req->__data_len += bio->bi_size;
1350        req->ioprio = ioprio_best(req->ioprio, bio_prio(bio));
1351
1352        drive_stat_acct(req, 0);
1353        return true;
1354}
1355
1356/**
1357 * attempt_plug_merge - try to merge with %current's plugged list
1358 * @q: request_queue new bio is being queued at
1359 * @bio: new bio being queued
1360 * @request_count: out parameter for number of traversed plugged requests
1361 *
1362 * Determine whether @bio being queued on @q can be merged with a request
1363 * on %current's plugged list.  Returns %true if merge was successful,
1364 * otherwise %false.
1365 *
1366 * Plugging coalesces IOs from the same issuer for the same purpose without
1367 * going through @q->queue_lock.  As such it's more of an issuing mechanism
1368 * than scheduling, and the request, while may have elvpriv data, is not
1369 * added on the elevator at this point.  In addition, we don't have
1370 * reliable access to the elevator outside queue lock.  Only check basic
1371 * merging parameters without querying the elevator.
1372 */
1373static bool attempt_plug_merge(struct request_queue *q, struct bio *bio,
1374                               unsigned int *request_count)
1375{
1376        struct blk_plug *plug;
1377        struct request *rq;
1378        bool ret = false;
1379
1380        plug = current->plug;
1381        if (!plug)
1382                goto out;
1383        *request_count = 0;
1384
1385        list_for_each_entry_reverse(rq, &plug->list, queuelist) {
1386                int el_ret;
1387
1388                if (rq->q == q)
1389                        (*request_count)++;
1390
1391                if (rq->q != q || !blk_rq_merge_ok(rq, bio))
1392                        continue;
1393
1394                el_ret = blk_try_merge(rq, bio);
1395                if (el_ret == ELEVATOR_BACK_MERGE) {
1396                        ret = bio_attempt_back_merge(q, rq, bio);
1397                        if (ret)
1398                                break;
1399                } else if (el_ret == ELEVATOR_FRONT_MERGE) {
1400                        ret = bio_attempt_front_merge(q, rq, bio);
1401                        if (ret)
1402                                break;
1403                }
1404        }
1405out:
1406        return ret;
1407}
1408
1409void init_request_from_bio(struct request *req, struct bio *bio)
1410{
1411        req->cmd_type = REQ_TYPE_FS;
1412
1413        req->cmd_flags |= bio->bi_rw & REQ_COMMON_MASK;
1414        if (bio->bi_rw & REQ_RAHEAD)
1415                req->cmd_flags |= REQ_FAILFAST_MASK;
1416
1417        req->errors = 0;
1418        req->__sector = bio->bi_sector;
1419        req->ioprio = bio_prio(bio);
1420        blk_rq_bio_prep(req->q, req, bio);
1421}
1422
1423void blk_queue_bio(struct request_queue *q, struct bio *bio)
1424{
1425        const bool sync = !!(bio->bi_rw & REQ_SYNC);
1426        struct blk_plug *plug;
1427        int el_ret, rw_flags, where = ELEVATOR_INSERT_SORT;
1428        struct request *req;
1429        unsigned int request_count = 0;
1430
1431        /*
1432         * low level driver can indicate that it wants pages above a
1433         * certain limit bounced to low memory (ie for highmem, or even
1434         * ISA dma in theory)
1435         */
1436        blk_queue_bounce(q, &bio);
1437
1438        if (bio->bi_rw & (REQ_FLUSH | REQ_FUA)) {
1439                spin_lock_irq(q->queue_lock);
1440                where = ELEVATOR_INSERT_FLUSH;
1441                goto get_rq;
1442        }
1443
1444        /*
1445         * Check if we can merge with the plugged list before grabbing
1446         * any locks.
1447         */
1448        if (attempt_plug_merge(q, bio, &request_count))
1449                return;
1450
1451        spin_lock_irq(q->queue_lock);
1452
1453        el_ret = elv_merge(q, &req, bio);
1454        if (el_ret == ELEVATOR_BACK_MERGE) {
1455                if (bio_attempt_back_merge(q, req, bio)) {
1456                        elv_bio_merged(q, req, bio);
1457                        if (!attempt_back_merge(q, req))
1458                                elv_merged_request(q, req, el_ret);
1459                        goto out_unlock;
1460                }
1461        } else if (el_ret == ELEVATOR_FRONT_MERGE) {
1462                if (bio_attempt_front_merge(q, req, bio)) {
1463                        elv_bio_merged(q, req, bio);
1464                        if (!attempt_front_merge(q, req))
1465                                elv_merged_request(q, req, el_ret);
1466                        goto out_unlock;
1467                }
1468        }
1469
1470get_rq:
1471        /*
1472         * This sync check and mask will be re-done in init_request_from_bio(),
1473         * but we need to set it earlier to expose the sync flag to the
1474         * rq allocator and io schedulers.
1475         */
1476        rw_flags = bio_data_dir(bio);
1477        if (sync)
1478                rw_flags |= REQ_SYNC;
1479
1480        /*
1481         * Grab a free request. This is might sleep but can not fail.
1482         * Returns with the queue unlocked.
1483         */
1484        req = get_request_wait(q, rw_flags, bio);
1485        if (unlikely(!req)) {
1486                bio_endio(bio, -ENODEV);        /* @q is dead */
1487                goto out_unlock;
1488        }
1489
1490        /*
1491         * After dropping the lock and possibly sleeping here, our request
1492         * may now be mergeable after it had proven unmergeable (above).
1493         * We don't worry about that case for efficiency. It won't happen
1494         * often, and the elevators are able to handle it.
1495         */
1496        init_request_from_bio(req, bio);
1497
1498        if (test_bit(QUEUE_FLAG_SAME_COMP, &q->queue_flags))
1499                req->cpu = raw_smp_processor_id();
1500
1501        plug = current->plug;
1502        if (plug) {
1503                /*
1504                 * If this is the first request added after a plug, fire
1505                 * of a plug trace. If others have been added before, check
1506                 * if we have multiple devices in this plug. If so, make a
1507                 * note to sort the list before dispatch.
1508                 */
1509                if (list_empty(&plug->list))
1510                        trace_block_plug(q);
1511                else {
1512                        if (!plug->should_sort) {
1513                                struct request *__rq;
1514
1515                                __rq = list_entry_rq(plug->list.prev);
1516                                if (__rq->q != q)
1517                                        plug->should_sort = 1;
1518                        }
1519                        if (request_count >= BLK_MAX_REQUEST_COUNT) {
1520                                blk_flush_plug_list(plug, false);
1521                                trace_block_plug(q);
1522                        }
1523                }
1524                list_add_tail(&req->queuelist, &plug->list);
1525                drive_stat_acct(req, 1);
1526        } else {
1527                spin_lock_irq(q->queue_lock);
1528                add_acct_request(q, req, where);
1529                __blk_run_queue(q);
1530out_unlock:
1531                spin_unlock_irq(q->queue_lock);
1532        }
1533}
1534EXPORT_SYMBOL_GPL(blk_queue_bio);       /* for device mapper only */
1535
1536/*
1537 * If bio->bi_dev is a partition, remap the location
1538 */
1539static inline void blk_partition_remap(struct bio *bio)
1540{
1541        struct block_device *bdev = bio->bi_bdev;
1542
1543        if (bio_sectors(bio) && bdev != bdev->bd_contains) {
1544                struct hd_struct *p = bdev->bd_part;
1545
1546                bio->bi_sector += p->start_sect;
1547                bio->bi_bdev = bdev->bd_contains;
1548
1549                trace_block_bio_remap(bdev_get_queue(bio->bi_bdev), bio,
1550                                      bdev->bd_dev,
1551                                      bio->bi_sector - p->start_sect);
1552        }
1553}
1554
1555static void handle_bad_sector(struct bio *bio)
1556{
1557        char b[BDEVNAME_SIZE];
1558
1559        printk(KERN_INFO "attempt to access beyond end of device\n");
1560        printk(KERN_INFO "%s: rw=%ld, want=%Lu, limit=%Lu\n",
1561                        bdevname(bio->bi_bdev, b),
1562                        bio->bi_rw,
1563                        (unsigned long long)bio->bi_sector + bio_sectors(bio),
1564                        (long long)(i_size_read(bio->bi_bdev->bd_inode) >> 9));
1565
1566        set_bit(BIO_EOF, &bio->bi_flags);
1567}
1568
1569#ifdef CONFIG_FAIL_MAKE_REQUEST
1570
1571static DECLARE_FAULT_ATTR(fail_make_request);
1572
1573static int __init setup_fail_make_request(char *str)
1574{
1575        return setup_fault_attr(&fail_make_request, str);
1576}
1577__setup("fail_make_request=", setup_fail_make_request);
1578
1579static bool should_fail_request(struct hd_struct *part, unsigned int bytes)
1580{
1581        return part->make_it_fail && should_fail(&fail_make_request, bytes);
1582}
1583
1584static int __init fail_make_request_debugfs(void)
1585{
1586        struct dentry *dir = fault_create_debugfs_attr("fail_make_request",
1587                                                NULL, &fail_make_request);
1588
1589        return IS_ERR(dir) ? PTR_ERR(dir) : 0;
1590}
1591
1592late_initcall(fail_make_request_debugfs);
1593
1594#else /* CONFIG_FAIL_MAKE_REQUEST */
1595
1596static inline bool should_fail_request(struct hd_struct *part,
1597                                        unsigned int bytes)
1598{
1599        return false;
1600}
1601
1602#endif /* CONFIG_FAIL_MAKE_REQUEST */
1603
1604/*
1605 * Check whether this bio extends beyond the end of the device.
1606 */
1607static inline int bio_check_eod(struct bio *bio, unsigned int nr_sectors)
1608{
1609        sector_t maxsector;
1610
1611        if (!nr_sectors)
1612                return 0;
1613
1614        /* Test device or partition size, when known. */
1615        maxsector = i_size_read(bio->bi_bdev->bd_inode) >> 9;
1616        if (maxsector) {
1617                sector_t sector = bio->bi_sector;
1618
1619                if (maxsector < nr_sectors || maxsector - nr_sectors < sector) {
1620                        /*
1621                         * This may well happen - the kernel calls bread()
1622                         * without checking the size of the device, e.g., when
1623                         * mounting a device.
1624                         */
1625                        handle_bad_sector(bio);
1626                        return 1;
1627                }
1628        }
1629
1630        return 0;
1631}
1632
1633static noinline_for_stack bool
1634generic_make_request_checks(struct bio *bio)
1635{
1636        struct request_queue *q;
1637        int nr_sectors = bio_sectors(bio);
1638        int err = -EIO;
1639        char b[BDEVNAME_SIZE];
1640        struct hd_struct *part;
1641
1642        might_sleep();
1643
1644        if (bio_check_eod(bio, nr_sectors))
1645                goto end_io;
1646
1647        q = bdev_get_queue(bio->bi_bdev);
1648        if (unlikely(!q)) {
1649                printk(KERN_ERR
1650                       "generic_make_request: Trying to access "
1651                        "nonexistent block-device %s (%Lu)\n",
1652                        bdevname(bio->bi_bdev, b),
1653                        (long long) bio->bi_sector);
1654                goto end_io;
1655        }
1656
1657        if (unlikely(!(bio->bi_rw & REQ_DISCARD) &&
1658                     nr_sectors > queue_max_hw_sectors(q))) {
1659                printk(KERN_ERR "bio too big device %s (%u > %u)\n",
1660                       bdevname(bio->bi_bdev, b),
1661                       bio_sectors(bio),
1662                       queue_max_hw_sectors(q));
1663                goto end_io;
1664        }
1665
1666        part = bio->bi_bdev->bd_part;
1667        if (should_fail_request(part, bio->bi_size) ||
1668            should_fail_request(&part_to_disk(part)->part0,
1669                                bio->bi_size))
1670                goto end_io;
1671
1672        /*
1673         * If this device has partitions, remap block n
1674         * of partition p to block n+start(p) of the disk.
1675         */
1676        blk_partition_remap(bio);
1677
1678        if (bio_integrity_enabled(bio) && bio_integrity_prep(bio))
1679                goto end_io;
1680
1681        if (bio_check_eod(bio, nr_sectors))
1682                goto end_io;
1683
1684        /*
1685         * Filter flush bio's early so that make_request based
1686         * drivers without flush support don't have to worry
1687         * about them.
1688         */
1689        if ((bio->bi_rw & (REQ_FLUSH | REQ_FUA)) && !q->flush_flags) {
1690                bio->bi_rw &= ~(REQ_FLUSH | REQ_FUA);
1691                if (!nr_sectors) {
1692                        err = 0;
1693                        goto end_io;
1694                }
1695        }
1696
1697        if ((bio->bi_rw & REQ_DISCARD) &&
1698            (!blk_queue_discard(q) ||
1699             ((bio->bi_rw & REQ_SECURE) &&
1700              !blk_queue_secdiscard(q)))) {
1701                err = -EOPNOTSUPP;
1702                goto end_io;
1703        }
1704
1705        if (blk_throtl_bio(q, bio))
1706                return false;   /* throttled, will be resubmitted later */
1707
1708        trace_block_bio_queue(q, bio);
1709        return true;
1710
1711end_io:
1712        bio_endio(bio, err);
1713        return false;
1714}
1715
1716/**
1717 * generic_make_request - hand a buffer to its device driver for I/O
1718 * @bio:  The bio describing the location in memory and on the device.
1719 *
1720 * generic_make_request() is used to make I/O requests of block
1721 * devices. It is passed a &struct bio, which describes the I/O that needs
1722 * to be done.
1723 *
1724 * generic_make_request() does not return any status.  The
1725 * success/failure status of the request, along with notification of
1726 * completion, is delivered asynchronously through the bio->bi_end_io
1727 * function described (one day) else where.
1728 *
1729 * The caller of generic_make_request must make sure that bi_io_vec
1730 * are set to describe the memory buffer, and that bi_dev and bi_sector are
1731 * set to describe the device address, and the
1732 * bi_end_io and optionally bi_private are set to describe how
1733 * completion notification should be signaled.
1734 *
1735 * generic_make_request and the drivers it calls may use bi_next if this
1736 * bio happens to be merged with someone else, and may resubmit the bio to
1737 * a lower device by calling into generic_make_request recursively, which
1738 * means the bio should NOT be touched after the call to ->make_request_fn.
1739 */
1740void generic_make_request(struct bio *bio)
1741{
1742        struct bio_list bio_list_on_stack;
1743
1744        if (!generic_make_request_checks(bio))
1745                return;
1746
1747        /*
1748         * We only want one ->make_request_fn to be active at a time, else
1749         * stack usage with stacked devices could be a problem.  So use
1750         * current->bio_list to keep a list of requests submited by a
1751         * make_request_fn function.  current->bio_list is also used as a
1752         * flag to say if generic_make_request is currently active in this
1753         * task or not.  If it is NULL, then no make_request is active.  If
1754         * it is non-NULL, then a make_request is active, and new requests
1755         * should be added at the tail
1756         */
1757        if (current->bio_list) {
1758                bio_list_add(current->bio_list, bio);
1759                return;
1760        }
1761
1762        /* following loop may be a bit non-obvious, and so deserves some
1763         * explanation.
1764         * Before entering the loop, bio->bi_next is NULL (as all callers
1765         * ensure that) so we have a list with a single bio.
1766         * We pretend that we have just taken it off a longer list, so
1767         * we assign bio_list to a pointer to the bio_list_on_stack,
1768         * thus initialising the bio_list of new bios to be
1769         * added.  ->make_request() may indeed add some more bios
1770         * through a recursive call to generic_make_request.  If it
1771         * did, we find a non-NULL value in bio_list and re-enter the loop
1772         * from the top.  In this case we really did just take the bio
1773         * of the top of the list (no pretending) and so remove it from
1774         * bio_list, and call into ->make_request() again.
1775         */
1776        BUG_ON(bio->bi_next);
1777        bio_list_init(&bio_list_on_stack);
1778        current->bio_list = &bio_list_on_stack;
1779        do {
1780                struct request_queue *q = bdev_get_queue(bio->bi_bdev);
1781
1782                q->make_request_fn(q, bio);
1783
1784                bio = bio_list_pop(current->bio_list);
1785        } while (bio);
1786        current->bio_list = NULL; /* deactivate */
1787}
1788EXPORT_SYMBOL(generic_make_request);
1789
1790/**
1791 * submit_bio - submit a bio to the block device layer for I/O
1792 * @rw: whether to %READ or %WRITE, or maybe to %READA (read ahead)
1793 * @bio: The &struct bio which describes the I/O
1794 *
1795 * submit_bio() is very similar in purpose to generic_make_request(), and
1796 * uses that function to do most of the work. Both are fairly rough
1797 * interfaces; @bio must be presetup and ready for I/O.
1798 *
1799 */
1800void submit_bio(int rw, struct bio *bio)
1801{
1802        int count = bio_sectors(bio);
1803
1804        bio->bi_rw |= rw;
1805
1806        /*
1807         * If it's a regular read/write or a barrier with data attached,
1808         * go through the normal accounting stuff before submission.
1809         */
1810        if (bio_has_data(bio) && !(rw & REQ_DISCARD)) {
1811                if (rw & WRITE) {
1812                        count_vm_events(PGPGOUT, count);
1813                } else {
1814                        task_io_account_read(bio->bi_size);
1815                        count_vm_events(PGPGIN, count);
1816                }
1817
1818                if (unlikely(block_dump)) {
1819                        char b[BDEVNAME_SIZE];
1820                        printk(KERN_DEBUG "%s(%d): %s block %Lu on %s (%u sectors)\n",
1821                        current->comm, task_pid_nr(current),
1822                                (rw & WRITE) ? "WRITE" : "READ",
1823                                (unsigned long long)bio->bi_sector,
1824                                bdevname(bio->bi_bdev, b),
1825                                count);
1826                }
1827        }
1828
1829        generic_make_request(bio);
1830}
1831EXPORT_SYMBOL(submit_bio);
1832
1833/**
1834 * blk_rq_check_limits - Helper function to check a request for the queue limit
1835 * @q:  the queue
1836 * @rq: the request being checked
1837 *
1838 * Description:
1839 *    @rq may have been made based on weaker limitations of upper-level queues
1840 *    in request stacking drivers, and it may violate the limitation of @q.
1841 *    Since the block layer and the underlying device driver trust @rq
1842 *    after it is inserted to @q, it should be checked against @q before
1843 *    the insertion using this generic function.
1844 *
1845 *    This function should also be useful for request stacking drivers
1846 *    in some cases below, so export this function.
1847 *    Request stacking drivers like request-based dm may change the queue
1848 *    limits while requests are in the queue (e.g. dm's table swapping).
1849 *    Such request stacking drivers should check those requests agaist
1850 *    the new queue limits again when they dispatch those requests,
1851 *    although such checkings are also done against the old queue limits
1852 *    when submitting requests.
1853 */
1854int blk_rq_check_limits(struct request_queue *q, struct request *rq)
1855{
1856        if (rq->cmd_flags & REQ_DISCARD)
1857                return 0;
1858
1859        if (blk_rq_sectors(rq) > queue_max_sectors(q) ||
1860            blk_rq_bytes(rq) > queue_max_hw_sectors(q) << 9) {
1861                printk(KERN_ERR "%s: over max size limit.\n", __func__);
1862                return -EIO;
1863        }
1864
1865        /*
1866         * queue's settings related to segment counting like q->bounce_pfn
1867         * may differ from that of other stacking queues.
1868         * Recalculate it to check the request correctly on this queue's
1869         * limitation.
1870         */
1871        blk_recalc_rq_segments(rq);
1872        if (rq->nr_phys_segments > queue_max_segments(q)) {
1873                printk(KERN_ERR "%s: over max segments limit.\n", __func__);
1874                return -EIO;
1875        }
1876
1877        return 0;
1878}
1879EXPORT_SYMBOL_GPL(blk_rq_check_limits);
1880
1881/**
1882 * blk_insert_cloned_request - Helper for stacking drivers to submit a request
1883 * @q:  the queue to submit the request
1884 * @rq: the request being queued
1885 */
1886int blk_insert_cloned_request(struct request_queue *q, struct request *rq)
1887{
1888        unsigned long flags;
1889        int where = ELEVATOR_INSERT_BACK;
1890
1891        if (blk_rq_check_limits(q, rq))
1892                return -EIO;
1893
1894        if (rq->rq_disk &&
1895            should_fail_request(&rq->rq_disk->part0, blk_rq_bytes(rq)))
1896                return -EIO;
1897
1898        spin_lock_irqsave(q->queue_lock, flags);
1899        if (unlikely(blk_queue_dead(q))) {
1900                spin_unlock_irqrestore(q->queue_lock, flags);
1901                return -ENODEV;
1902        }
1903
1904        /*
1905         * Submitting request must be dequeued before calling this function
1906         * because it will be linked to another request_queue
1907         */
1908        BUG_ON(blk_queued_rq(rq));
1909
1910        if (rq->cmd_flags & (REQ_FLUSH|REQ_FUA))
1911                where = ELEVATOR_INSERT_FLUSH;
1912
1913        add_acct_request(q, rq, where);
1914        if (where == ELEVATOR_INSERT_FLUSH)
1915                __blk_run_queue(q);
1916        spin_unlock_irqrestore(q->queue_lock, flags);
1917
1918        return 0;
1919}
1920EXPORT_SYMBOL_GPL(blk_insert_cloned_request);
1921
1922/**
1923 * blk_rq_err_bytes - determine number of bytes till the next failure boundary
1924 * @rq: request to examine
1925 *
1926 * Description:
1927 *     A request could be merge of IOs which require different failure
1928 *     handling.  This function determines the number of bytes which
1929 *     can be failed from the beginning of the request without
1930 *     crossing into area which need to be retried further.
1931 *
1932 * Return:
1933 *     The number of bytes to fail.
1934 *
1935 * Context:
1936 *     queue_lock must be held.
1937 */
1938unsigned int blk_rq_err_bytes(const struct request *rq)
1939{
1940        unsigned int ff = rq->cmd_flags & REQ_FAILFAST_MASK;
1941        unsigned int bytes = 0;
1942        struct bio *bio;
1943
1944        if (!(rq->cmd_flags & REQ_MIXED_MERGE))
1945                return blk_rq_bytes(rq);
1946
1947        /*
1948         * Currently the only 'mixing' which can happen is between
1949         * different fastfail types.  We can safely fail portions
1950         * which have all the failfast bits that the first one has -
1951         * the ones which are at least as eager to fail as the first
1952         * one.
1953         */
1954        for (bio = rq->bio; bio; bio = bio->bi_next) {
1955                if ((bio->bi_rw & ff) != ff)
1956                        break;
1957                bytes += bio->bi_size;
1958        }
1959
1960        /* this could lead to infinite loop */
1961        BUG_ON(blk_rq_bytes(rq) && !bytes);
1962        return bytes;
1963}
1964EXPORT_SYMBOL_GPL(blk_rq_err_bytes);
1965
1966static void blk_account_io_completion(struct request *req, unsigned int bytes)
1967{
1968        if (blk_do_io_stat(req)) {
1969                const int rw = rq_data_dir(req);
1970                struct hd_struct *part;
1971                int cpu;
1972
1973                cpu = part_stat_lock();
1974                part = req->part;
1975                part_stat_add(cpu, part, sectors[rw], bytes >> 9);
1976                part_stat_unlock();
1977        }
1978}
1979
1980static void blk_account_io_done(struct request *req)
1981{
1982        /*
1983         * Account IO completion.  flush_rq isn't accounted as a
1984         * normal IO on queueing nor completion.  Accounting the
1985         * containing request is enough.
1986         */
1987        if (blk_do_io_stat(req) && !(req->cmd_flags & REQ_FLUSH_SEQ)) {
1988                unsigned long duration = jiffies - req->start_time;
1989                const int rw = rq_data_dir(req);
1990                struct hd_struct *part;
1991                int cpu;
1992
1993                cpu = part_stat_lock();
1994                part = req->part;
1995
1996                part_stat_inc(cpu, part, ios[rw]);
1997                part_stat_add(cpu, part, ticks[rw], duration);
1998                part_round_stats(cpu, part);
1999                part_dec_in_flight(part, rw);
2000
2001                hd_struct_put(part);
2002                part_stat_unlock();
2003        }
2004}
2005
2006/**
2007 * blk_peek_request - peek at the top of a request queue
2008 * @q: request queue to peek at
2009 *
2010 * Description:
2011 *     Return the request at the top of @q.  The returned request
2012 *     should be started using blk_start_request() before LLD starts
2013 *     processing it.
2014 *
2015 * Return:
2016 *     Pointer to the request at the top of @q if available.  Null
2017 *     otherwise.
2018 *
2019 * Context:
2020 *     queue_lock must be held.
2021 */
2022struct request *blk_peek_request(struct request_queue *q)
2023{
2024        struct request *rq;
2025        int ret;
2026
2027        while ((rq = __elv_next_request(q)) != NULL) {
2028                if (!(rq->cmd_flags & REQ_STARTED)) {
2029                        /*
2030                         * This is the first time the device driver
2031                         * sees this request (possibly after
2032                         * requeueing).  Notify IO scheduler.
2033                         */
2034                        if (rq->cmd_flags & REQ_SORTED)
2035                                elv_activate_rq(q, rq);
2036
2037                        /*
2038                         * just mark as started even if we don't start
2039                         * it, a request that has been delayed should
2040                         * not be passed by new incoming requests
2041                         */
2042                        rq->cmd_flags |= REQ_STARTED;
2043                        trace_block_rq_issue(q, rq);
2044                }
2045
2046                if (!q->boundary_rq || q->boundary_rq == rq) {
2047                        q->end_sector = rq_end_sector(rq);
2048                        q->boundary_rq = NULL;
2049                }
2050
2051                if (rq->cmd_flags & REQ_DONTPREP)
2052                        break;
2053
2054                if (q->dma_drain_size && blk_rq_bytes(rq)) {
2055                        /*
2056                         * make sure space for the drain appears we
2057                         * know we can do this because max_hw_segments
2058                         * has been adjusted to be one fewer than the
2059                         * device can handle
2060                         */
2061                        rq->nr_phys_segments++;
2062                }
2063
2064                if (!q->prep_rq_fn)
2065                        break;
2066
2067                ret = q->prep_rq_fn(q, rq);
2068                if (ret == BLKPREP_OK) {
2069                        break;
2070                } else if (ret == BLKPREP_DEFER) {
2071                        /*
2072                         * the request may have been (partially) prepped.
2073                         * we need to keep this request in the front to
2074                         * avoid resource deadlock.  REQ_STARTED will
2075                         * prevent other fs requests from passing this one.
2076                         */
2077                        if (q->dma_drain_size && blk_rq_bytes(rq) &&
2078                            !(rq->cmd_flags & REQ_DONTPREP)) {
2079                                /*
2080                                 * remove the space for the drain we added
2081                                 * so that we don't add it again
2082                                 */
2083                                --rq->nr_phys_segments;
2084                        }
2085
2086                        rq = NULL;
2087                        break;
2088                } else if (ret == BLKPREP_KILL) {
2089                        rq->cmd_flags |= REQ_QUIET;
2090                        /*
2091                         * Mark this request as started so we don't trigger
2092                         * any debug logic in the end I/O path.
2093                         */
2094                        blk_start_request(rq);
2095                        __blk_end_request_all(rq, -EIO);
2096                } else {
2097                        printk(KERN_ERR "%s: bad return=%d\n", __func__, ret);
2098                        break;
2099                }
2100        }
2101
2102        return rq;
2103}
2104EXPORT_SYMBOL(blk_peek_request);
2105
2106void blk_dequeue_request(struct request *rq)
2107{
2108        struct request_queue *q = rq->q;
2109
2110        BUG_ON(list_empty(&rq->queuelist));
2111        BUG_ON(ELV_ON_HASH(rq));
2112
2113        list_del_init(&rq->queuelist);
2114
2115        /*
2116         * the time frame between a request being removed from the lists
2117         * and to it is freed is accounted as io that is in progress at
2118         * the driver side.
2119         */
2120        if (blk_account_rq(rq)) {
2121                q->in_flight[rq_is_sync(rq)]++;
2122                set_io_start_time_ns(rq);
2123        }
2124}
2125
2126/**
2127 * blk_start_request - start request processing on the driver
2128 * @req: request to dequeue
2129 *
2130 * Description:
2131 *     Dequeue @req and start timeout timer on it.  This hands off the
2132 *     request to the driver.
2133 *
2134 *     Block internal functions which don't want to start timer should
2135 *     call blk_dequeue_request().
2136 *
2137 * Context:
2138 *     queue_lock must be held.
2139 */
2140void blk_start_request(struct request *req)
2141{
2142        blk_dequeue_request(req);
2143
2144        /*
2145         * We are now handing the request to the hardware, initialize
2146         * resid_len to full count and add the timeout handler.
2147         */
2148        req->resid_len = blk_rq_bytes(req);
2149        if (unlikely(blk_bidi_rq(req)))
2150                req->next_rq->resid_len = blk_rq_bytes(req->next_rq);
2151
2152        blk_add_timer(req);
2153}
2154EXPORT_SYMBOL(blk_start_request);
2155
2156/**
2157 * blk_fetch_request - fetch a request from a request queue
2158 * @q: request queue to fetch a request from
2159 *
2160 * Description:
2161 *     Return the request at the top of @q.  The request is started on
2162 *     return and LLD can start processing it immediately.
2163 *
2164 * Return:
2165 *     Pointer to the request at the top of @q if available.  Null
2166 *     otherwise.
2167 *
2168 * Context:
2169 *     queue_lock must be held.
2170 */
2171struct request *blk_fetch_request(struct request_queue *q)
2172{
2173        struct request *rq;
2174
2175        rq = blk_peek_request(q);
2176        if (rq)
2177                blk_start_request(rq);
2178        return rq;
2179}
2180EXPORT_SYMBOL(blk_fetch_request);
2181
2182/**
2183 * blk_update_request - Special helper function for request stacking drivers
2184 * @req:      the request being processed
2185 * @error:    %0 for success, < %0 for error
2186 * @nr_bytes: number of bytes to complete @req
2187 *
2188 * Description:
2189 *     Ends I/O on a number of bytes attached to @req, but doesn't complete
2190 *     the request structure even if @req doesn't have leftover.
2191 *     If @req has leftover, sets it up for the next range of segments.
2192 *
2193 *     This special helper function is only for request stacking drivers
2194 *     (e.g. request-based dm) so that they can handle partial completion.
2195 *     Actual device drivers should use blk_end_request instead.
2196 *
2197 *     Passing the result of blk_rq_bytes() as @nr_bytes guarantees
2198 *     %false return from this function.
2199 *
2200 * Return:
2201 *     %false - this request doesn't have any more data
2202 *     %true  - this request has more data
2203 **/
2204bool blk_update_request(struct request *req, int error, unsigned int nr_bytes)
2205{
2206        int total_bytes, bio_nbytes, next_idx = 0;
2207        struct bio *bio;
2208
2209        if (!req->bio)
2210                return false;
2211
2212        trace_block_rq_complete(req->q, req);
2213
2214        /*
2215         * For fs requests, rq is just carrier of independent bio's
2216         * and each partial completion should be handled separately.
2217         * Reset per-request error on each partial completion.
2218         *
2219         * TODO: tj: This is too subtle.  It would be better to let
2220         * low level drivers do what they see fit.
2221         */
2222        if (req->cmd_type == REQ_TYPE_FS)
2223                req->errors = 0;
2224
2225        if (error && req->cmd_type == REQ_TYPE_FS &&
2226            !(req->cmd_flags & REQ_QUIET)) {
2227                char *error_type;
2228
2229                switch (error) {
2230                case -ENOLINK:
2231                        error_type = "recoverable transport";
2232                        break;
2233                case -EREMOTEIO:
2234                        error_type = "critical target";
2235                        break;
2236                case -EBADE:
2237                        error_type = "critical nexus";
2238                        break;
2239                case -EIO:
2240                default:
2241                        error_type = "I/O";
2242                        break;
2243                }
2244                printk(KERN_ERR "end_request: %s error, dev %s, sector %llu\n",
2245                       error_type, req->rq_disk ? req->rq_disk->disk_name : "?",
2246                       (unsigned long long)blk_rq_pos(req));
2247        }
2248
2249        blk_account_io_completion(req, nr_bytes);
2250
2251        total_bytes = bio_nbytes = 0;
2252        while ((bio = req->bio) != NULL) {
2253                int nbytes;
2254
2255                if (nr_bytes >= bio->bi_size) {
2256                        req->bio = bio->bi_next;
2257                        nbytes = bio->bi_size;
2258                        req_bio_endio(req, bio, nbytes, error);
2259                        next_idx = 0;
2260                        bio_nbytes = 0;
2261                } else {
2262                        int idx = bio->bi_idx + next_idx;
2263
2264                        if (unlikely(idx >= bio->bi_vcnt)) {
2265                                blk_dump_rq_flags(req, "__end_that");
2266                                printk(KERN_ERR "%s: bio idx %d >= vcnt %d\n",
2267                                       __func__, idx, bio->bi_vcnt);
2268                                break;
2269                        }
2270
2271                        nbytes = bio_iovec_idx(bio, idx)->bv_len;
2272                        BIO_BUG_ON(nbytes > bio->bi_size);
2273
2274                        /*
2275                         * not a complete bvec done
2276                         */
2277                        if (unlikely(nbytes > nr_bytes)) {
2278                                bio_nbytes += nr_bytes;
2279                                total_bytes += nr_bytes;
2280                                break;
2281                        }
2282
2283                        /*
2284                         * advance to the next vector
2285                         */
2286                        next_idx++;
2287                        bio_nbytes += nbytes;
2288                }
2289
2290                total_bytes += nbytes;
2291                nr_bytes -= nbytes;
2292
2293                bio = req->bio;
2294                if (bio) {
2295                        /*
2296                         * end more in this run, or just return 'not-done'
2297                         */
2298                        if (unlikely(nr_bytes <= 0))
2299                                break;
2300                }
2301        }
2302
2303        /*
2304         * completely done
2305         */
2306        if (!req->bio) {
2307                /*
2308                 * Reset counters so that the request stacking driver
2309                 * can find how many bytes remain in the request
2310                 * later.
2311                 */
2312                req->__data_len = 0;
2313                return false;
2314        }
2315
2316        /*
2317         * if the request wasn't completed, update state
2318         */
2319        if (bio_nbytes) {
2320                req_bio_endio(req, bio, bio_nbytes, error);
2321                bio->bi_idx += next_idx;
2322                bio_iovec(bio)->bv_offset += nr_bytes;
2323                bio_iovec(bio)->bv_len -= nr_bytes;
2324        }
2325
2326        req->__data_len -= total_bytes;
2327        req->buffer = bio_data(req->bio);
2328
2329        /* update sector only for requests with clear definition of sector */
2330        if (req->cmd_type == REQ_TYPE_FS || (req->cmd_flags & REQ_DISCARD))
2331                req->__sector += total_bytes >> 9;
2332
2333        /* mixed attributes always follow the first bio */
2334        if (req->cmd_flags & REQ_MIXED_MERGE) {
2335                req->cmd_flags &= ~REQ_FAILFAST_MASK;
2336                req->cmd_flags |= req->bio->bi_rw & REQ_FAILFAST_MASK;
2337        }
2338
2339        /*
2340         * If total number of sectors is less than the first segment
2341         * size, something has gone terribly wrong.
2342         */
2343        if (blk_rq_bytes(req) < blk_rq_cur_bytes(req)) {
2344                blk_dump_rq_flags(req, "request botched");
2345                req->__data_len = blk_rq_cur_bytes(req);
2346        }
2347
2348        /* recalculate the number of segments */
2349        blk_recalc_rq_segments(req);
2350
2351        return true;
2352}
2353EXPORT_SYMBOL_GPL(blk_update_request);
2354
2355static bool blk_update_bidi_request(struct request *rq, int error,
2356                                    unsigned int nr_bytes,
2357                                    unsigned int bidi_bytes)
2358{
2359        if (blk_update_request(rq, error, nr_bytes))
2360                return true;
2361
2362        /* Bidi request must be completed as a whole */
2363        if (unlikely(blk_bidi_rq(rq)) &&
2364            blk_update_request(rq->next_rq, error, bidi_bytes))
2365                return true;
2366
2367        if (blk_queue_add_random(rq->q))
2368                add_disk_randomness(rq->rq_disk);
2369
2370        return false;
2371}
2372
2373/**
2374 * blk_unprep_request - unprepare a request
2375 * @req:        the request
2376 *
2377 * This function makes a request ready for complete resubmission (or
2378 * completion).  It happens only after all error handling is complete,
2379 * so represents the appropriate moment to deallocate any resources
2380 * that were allocated to the request in the prep_rq_fn.  The queue
2381 * lock is held when calling this.
2382 */
2383void blk_unprep_request(struct request *req)
2384{
2385        struct request_queue *q = req->q;
2386
2387        req->cmd_flags &= ~REQ_DONTPREP;
2388        if (q->unprep_rq_fn)
2389                q->unprep_rq_fn(q, req);
2390}
2391EXPORT_SYMBOL_GPL(blk_unprep_request);
2392
2393/*
2394 * queue lock must be held
2395 */
2396static void blk_finish_request(struct request *req, int error)
2397{
2398        if (blk_rq_tagged(req))
2399                blk_queue_end_tag(req->q, req);
2400
2401        BUG_ON(blk_queued_rq(req));
2402
2403        if (unlikely(laptop_mode) && req->cmd_type == REQ_TYPE_FS)
2404                laptop_io_completion(&req->q->backing_dev_info);
2405
2406        blk_delete_timer(req);
2407
2408        if (req->cmd_flags & REQ_DONTPREP)
2409                blk_unprep_request(req);
2410
2411
2412        blk_account_io_done(req);
2413
2414        if (req->end_io)
2415                req->end_io(req, error);
2416        else {
2417                if (blk_bidi_rq(req))
2418                        __blk_put_request(req->next_rq->q, req->next_rq);
2419
2420                __blk_put_request(req->q, req);
2421        }
2422}
2423
2424/**
2425 * blk_end_bidi_request - Complete a bidi request
2426 * @rq:         the request to complete
2427 * @error:      %0 for success, < %0 for error
2428 * @nr_bytes:   number of bytes to complete @rq
2429 * @bidi_bytes: number of bytes to complete @rq->next_rq
2430 *
2431 * Description:
2432 *     Ends I/O on a number of bytes attached to @rq and @rq->next_rq.
2433 *     Drivers that supports bidi can safely call this member for any
2434 *     type of request, bidi or uni.  In the later case @bidi_bytes is
2435 *     just ignored.
2436 *
2437 * Return:
2438 *     %false - we are done with this request
2439 *     %true  - still buffers pending for this request
2440 **/
2441static bool blk_end_bidi_request(struct request *rq, int error,
2442                                 unsigned int nr_bytes, unsigned int bidi_bytes)
2443{
2444        struct request_queue *q = rq->q;
2445        unsigned long flags;
2446
2447        if (blk_update_bidi_request(rq, error, nr_bytes, bidi_bytes))
2448                return true;
2449
2450        spin_lock_irqsave(q->queue_lock, flags);
2451        blk_finish_request(rq, error);
2452        spin_unlock_irqrestore(q->queue_lock, flags);
2453
2454        return false;
2455}
2456
2457/**
2458 * __blk_end_bidi_request - Complete a bidi request with queue lock held
2459 * @rq:         the request to complete
2460 * @error:      %0 for success, < %0 for error
2461 * @nr_bytes:   number of bytes to complete @rq
2462 * @bidi_bytes: number of bytes to complete @rq->next_rq
2463 *
2464 * Description:
2465 *     Identical to blk_end_bidi_request() except that queue lock is
2466 *     assumed to be locked on entry and remains so on return.
2467 *
2468 * Return:
2469 *     %false - we are done with this request
2470 *     %true  - still buffers pending for this request
2471 **/
2472bool __blk_end_bidi_request(struct request *rq, int error,
2473                                   unsigned int nr_bytes, unsigned int bidi_bytes)
2474{
2475        if (blk_update_bidi_request(rq, error, nr_bytes, bidi_bytes))
2476                return true;
2477
2478        blk_finish_request(rq, error);
2479
2480        return false;
2481}
2482
2483/**
2484 * blk_end_request - Helper function for drivers to complete the request.
2485 * @rq:       the request being processed
2486 * @error:    %0 for success, < %0 for error
2487 * @nr_bytes: number of bytes to complete
2488 *
2489 * Description:
2490 *     Ends I/O on a number of bytes attached to @rq.
2491 *     If @rq has leftover, sets it up for the next range of segments.
2492 *
2493 * Return:
2494 *     %false - we are done with this request
2495 *     %true  - still buffers pending for this request
2496 **/
2497bool blk_end_request(struct request *rq, int error, unsigned int nr_bytes)
2498{
2499        return blk_end_bidi_request(rq, error, nr_bytes, 0);
2500}
2501EXPORT_SYMBOL(blk_end_request);
2502
2503/**
2504 * blk_end_request_all - Helper function for drives to finish the request.
2505 * @rq: the request to finish
2506 * @error: %0 for success, < %0 for error
2507 *
2508 * Description:
2509 *     Completely finish @rq.
2510 */
2511void blk_end_request_all(struct request *rq, int error)
2512{
2513        bool pending;
2514        unsigned int bidi_bytes = 0;
2515
2516        if (unlikely(blk_bidi_rq(rq)))
2517                bidi_bytes = blk_rq_bytes(rq->next_rq);
2518
2519        pending = blk_end_bidi_request(rq, error, blk_rq_bytes(rq), bidi_bytes);
2520        BUG_ON(pending);
2521}
2522EXPORT_SYMBOL(blk_end_request_all);
2523
2524/**
2525 * blk_end_request_cur - Helper function to finish the current request chunk.
2526 * @rq: the request to finish the current chunk for
2527 * @error: %0 for success, < %0 for error
2528 *
2529 * Description:
2530 *     Complete the current consecutively mapped chunk from @rq.
2531 *
2532 * Return:
2533 *     %false - we are done with this request
2534 *     %true  - still buffers pending for this request
2535 */
2536bool blk_end_request_cur(struct request *rq, int error)
2537{
2538        return blk_end_request(rq, error, blk_rq_cur_bytes(rq));
2539}
2540EXPORT_SYMBOL(blk_end_request_cur);
2541
2542/**
2543 * blk_end_request_err - Finish a request till the next failure boundary.
2544 * @rq: the request to finish till the next failure boundary for
2545 * @error: must be negative errno
2546 *
2547 * Description:
2548 *     Complete @rq till the next failure boundary.
2549 *
2550 * Return:
2551 *     %false - we are done with this request
2552 *     %true  - still buffers pending for this request
2553 */
2554bool blk_end_request_err(struct request *rq, int error)
2555{
2556        WARN_ON(error >= 0);
2557        return blk_end_request(rq, error, blk_rq_err_bytes(rq));
2558}
2559EXPORT_SYMBOL_GPL(blk_end_request_err);
2560
2561/**
2562 * __blk_end_request - Helper function for drivers to complete the request.
2563 * @rq:       the request being processed
2564 * @error:    %0 for success, < %0 for error
2565 * @nr_bytes: number of bytes to complete
2566 *
2567 * Description:
2568 *     Must be called with queue lock held unlike blk_end_request().
2569 *
2570 * Return:
2571 *     %false - we are done with this request
2572 *     %true  - still buffers pending for this request
2573 **/
2574bool __blk_end_request(struct request *rq, int error, unsigned int nr_bytes)
2575{
2576        return __blk_end_bidi_request(rq, error, nr_bytes, 0);
2577}
2578EXPORT_SYMBOL(__blk_end_request);
2579
2580/**
2581 * __blk_end_request_all - Helper function for drives to finish the request.
2582 * @rq: the request to finish
2583 * @error: %0 for success, < %0 for error
2584 *
2585 * Description:
2586 *     Completely finish @rq.  Must be called with queue lock held.
2587 */
2588void __blk_end_request_all(struct request *rq, int error)
2589{
2590        bool pending;
2591        unsigned int bidi_bytes = 0;
2592
2593        if (unlikely(blk_bidi_rq(rq)))
2594                bidi_bytes = blk_rq_bytes(rq->next_rq);
2595
2596        pending = __blk_end_bidi_request(rq, error, blk_rq_bytes(rq), bidi_bytes);
2597        BUG_ON(pending);
2598}
2599EXPORT_SYMBOL(__blk_end_request_all);
2600
2601/**
2602 * __blk_end_request_cur - Helper function to finish the current request chunk.
2603 * @rq: the request to finish the current chunk for
2604 * @error: %0 for success, < %0 for error
2605 *
2606 * Description:
2607 *     Complete the current consecutively mapped chunk from @rq.  Must
2608 *     be called with queue lock held.
2609 *
2610 * Return:
2611 *     %false - we are done with this request
2612 *     %true  - still buffers pending for this request
2613 */
2614bool __blk_end_request_cur(struct request *rq, int error)
2615{
2616        return __blk_end_request(rq, error, blk_rq_cur_bytes(rq));
2617}
2618EXPORT_SYMBOL(__blk_end_request_cur);
2619
2620/**
2621 * __blk_end_request_err - Finish a request till the next failure boundary.
2622 * @rq: the request to finish till the next failure boundary for
2623 * @error: must be negative errno
2624 *
2625 * Description:
2626 *     Complete @rq till the next failure boundary.  Must be called
2627 *     with queue lock held.
2628 *
2629 * Return:
2630 *     %false - we are done with this request
2631 *     %true  - still buffers pending for this request
2632 */
2633bool __blk_end_request_err(struct request *rq, int error)
2634{
2635        WARN_ON(error >= 0);
2636        return __blk_end_request(rq, error, blk_rq_err_bytes(rq));
2637}
2638EXPORT_SYMBOL_GPL(__blk_end_request_err);
2639
2640void blk_rq_bio_prep(struct request_queue *q, struct request *rq,
2641                     struct bio *bio)
2642{
2643        /* Bit 0 (R/W) is identical in rq->cmd_flags and bio->bi_rw */
2644        rq->cmd_flags |= bio->bi_rw & REQ_WRITE;
2645
2646        if (bio_has_data(bio)) {
2647                rq->nr_phys_segments = bio_phys_segments(q, bio);
2648                rq->buffer = bio_data(bio);
2649        }
2650        rq->__data_len = bio->bi_size;
2651        rq->bio = rq->biotail = bio;
2652
2653        if (bio->bi_bdev)
2654                rq->rq_disk = bio->bi_bdev->bd_disk;
2655}
2656
2657#if ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE
2658/**
2659 * rq_flush_dcache_pages - Helper function to flush all pages in a request
2660 * @rq: the request to be flushed
2661 *
2662 * Description:
2663 *     Flush all pages in @rq.
2664 */
2665void rq_flush_dcache_pages(struct request *rq)
2666{
2667        struct req_iterator iter;
2668        struct bio_vec *bvec;
2669
2670        rq_for_each_segment(bvec, rq, iter)
2671                flush_dcache_page(bvec->bv_page);
2672}
2673EXPORT_SYMBOL_GPL(rq_flush_dcache_pages);
2674#endif
2675
2676/**
2677 * blk_lld_busy - Check if underlying low-level drivers of a device are busy
2678 * @q : the queue of the device being checked
2679 *
2680 * Description:
2681 *    Check if underlying low-level drivers of a device are busy.
2682 *    If the drivers want to export their busy state, they must set own
2683 *    exporting function using blk_queue_lld_busy() first.
2684 *
2685 *    Basically, this function is used only by request stacking drivers
2686 *    to stop dispatching requests to underlying devices when underlying
2687 *    devices are busy.  This behavior helps more I/O merging on the queue
2688 *    of the request stacking driver and prevents I/O throughput regression
2689 *    on burst I/O load.
2690 *
2691 * Return:
2692 *    0 - Not busy (The request stacking driver should dispatch request)
2693 *    1 - Busy (The request stacking driver should stop dispatching request)
2694 */
2695int blk_lld_busy(struct request_queue *q)
2696{
2697        if (q->lld_busy_fn)
2698                return q->lld_busy_fn(q);
2699
2700        return 0;
2701}
2702EXPORT_SYMBOL_GPL(blk_lld_busy);
2703
2704/**
2705 * blk_rq_unprep_clone - Helper function to free all bios in a cloned request
2706 * @rq: the clone request to be cleaned up
2707 *
2708 * Description:
2709 *     Free all bios in @rq for a cloned request.
2710 */
2711void blk_rq_unprep_clone(struct request *rq)
2712{
2713        struct bio *bio;
2714
2715        while ((bio = rq->bio) != NULL) {
2716                rq->bio = bio->bi_next;
2717
2718                bio_put(bio);
2719        }
2720}
2721EXPORT_SYMBOL_GPL(blk_rq_unprep_clone);
2722
2723/*
2724 * Copy attributes of the original request to the clone request.
2725 * The actual data parts (e.g. ->cmd, ->buffer, ->sense) are not copied.
2726 */
2727static void __blk_rq_prep_clone(struct request *dst, struct request *src)
2728{
2729        dst->cpu = src->cpu;
2730        dst->cmd_flags = (src->cmd_flags & REQ_CLONE_MASK) | REQ_NOMERGE;
2731        dst->cmd_type = src->cmd_type;
2732        dst->__sector = blk_rq_pos(src);
2733        dst->__data_len = blk_rq_bytes(src);
2734        dst->nr_phys_segments = src->nr_phys_segments;
2735        dst->ioprio = src->ioprio;
2736        dst->extra_len = src->extra_len;
2737}
2738
2739/**
2740 * blk_rq_prep_clone - Helper function to setup clone request
2741 * @rq: the request to be setup
2742 * @rq_src: original request to be cloned
2743 * @bs: bio_set that bios for clone are allocated from
2744 * @gfp_mask: memory allocation mask for bio
2745 * @bio_ctr: setup function to be called for each clone bio.
2746 *           Returns %0 for success, non %0 for failure.
2747 * @data: private data to be passed to @bio_ctr
2748 *
2749 * Description:
2750 *     Clones bios in @rq_src to @rq, and copies attributes of @rq_src to @rq.
2751 *     The actual data parts of @rq_src (e.g. ->cmd, ->buffer, ->sense)
2752 *     are not copied, and copying such parts is the caller's responsibility.
2753 *     Also, pages which the original bios are pointing to are not copied
2754 *     and the cloned bios just point same pages.
2755 *     So cloned bios must be completed before original bios, which means
2756 *     the caller must complete @rq before @rq_src.
2757 */
2758int blk_rq_prep_clone(struct request *rq, struct request *rq_src,
2759                      struct bio_set *bs, gfp_t gfp_mask,
2760                      int (*bio_ctr)(struct bio *, struct bio *, void *),
2761                      void *data)
2762{
2763        struct bio *bio, *bio_src;
2764
2765        if (!bs)
2766                bs = fs_bio_set;
2767
2768        blk_rq_init(NULL, rq);
2769
2770        __rq_for_each_bio(bio_src, rq_src) {
2771                bio = bio_alloc_bioset(gfp_mask, bio_src->bi_max_vecs, bs);
2772                if (!bio)
2773                        goto free_and_out;
2774
2775                __bio_clone(bio, bio_src);
2776
2777                if (bio_integrity(bio_src) &&
2778                    bio_integrity_clone(bio, bio_src, gfp_mask, bs))
2779                        goto free_and_out;
2780
2781                if (bio_ctr && bio_ctr(bio, bio_src, data))
2782                        goto free_and_out;
2783
2784                if (rq->bio) {
2785                        rq->biotail->bi_next = bio;
2786                        rq->biotail = bio;
2787                } else
2788                        rq->bio = rq->biotail = bio;
2789        }
2790
2791        __blk_rq_prep_clone(rq, rq_src);
2792
2793        return 0;
2794
2795free_and_out:
2796        if (bio)
2797                bio_free(bio, bs);
2798        blk_rq_unprep_clone(rq);
2799
2800        return -ENOMEM;
2801}
2802EXPORT_SYMBOL_GPL(blk_rq_prep_clone);
2803
2804int kblockd_schedule_work(struct request_queue *q, struct work_struct *work)
2805{
2806        return queue_work(kblockd_workqueue, work);
2807}
2808EXPORT_SYMBOL(kblockd_schedule_work);
2809
2810int kblockd_schedule_delayed_work(struct request_queue *q,
2811                        struct delayed_work *dwork, unsigned long delay)
2812{
2813        return queue_delayed_work(kblockd_workqueue, dwork, delay);
2814}
2815EXPORT_SYMBOL(kblockd_schedule_delayed_work);
2816
2817#define PLUG_MAGIC      0x91827364
2818
2819/**
2820 * blk_start_plug - initialize blk_plug and track it inside the task_struct
2821 * @plug:       The &struct blk_plug that needs to be initialized
2822 *
2823 * Description:
2824 *   Tracking blk_plug inside the task_struct will help with auto-flushing the
2825 *   pending I/O should the task end up blocking between blk_start_plug() and
2826 *   blk_finish_plug(). This is important from a performance perspective, but
2827 *   also ensures that we don't deadlock. For instance, if the task is blocking
2828 *   for a memory allocation, memory reclaim could end up wanting to free a
2829 *   page belonging to that request that is currently residing in our private
2830 *   plug. By flushing the pending I/O when the process goes to sleep, we avoid
2831 *   this kind of deadlock.
2832 */
2833void blk_start_plug(struct blk_plug *plug)
2834{
2835        struct task_struct *tsk = current;
2836
2837        plug->magic = PLUG_MAGIC;
2838        INIT_LIST_HEAD(&plug->list);
2839        INIT_LIST_HEAD(&plug->cb_list);
2840        plug->should_sort = 0;
2841
2842        /*
2843         * If this is a nested plug, don't actually assign it. It will be
2844         * flushed on its own.
2845         */
2846        if (!tsk->plug) {
2847                /*
2848                 * Store ordering should not be needed here, since a potential
2849                 * preempt will imply a full memory barrier
2850                 */
2851                tsk->plug = plug;
2852        }
2853}
2854EXPORT_SYMBOL(blk_start_plug);
2855
2856static int plug_rq_cmp(void *priv, struct list_head *a, struct list_head *b)
2857{
2858        struct request *rqa = container_of(a, struct request, queuelist);
2859        struct request *rqb = container_of(b, struct request, queuelist);
2860
2861        return !(rqa->q <= rqb->q);
2862}
2863
2864/*
2865 * If 'from_schedule' is true, then postpone the dispatch of requests
2866 * until a safe kblockd context. We due this to avoid accidental big
2867 * additional stack usage in driver dispatch, in places where the originally
2868 * plugger did not intend it.
2869 */
2870static void queue_unplugged(struct request_queue *q, unsigned int depth,
2871                            bool from_schedule)
2872        __releases(q->queue_lock)
2873{
2874        trace_block_unplug(q, depth, !from_schedule);
2875
2876        /*
2877         * Don't mess with dead queue.
2878         */
2879        if (unlikely(blk_queue_dead(q))) {
2880                spin_unlock(q->queue_lock);
2881                return;
2882        }
2883
2884        /*
2885         * If we are punting this to kblockd, then we can safely drop
2886         * the queue_lock before waking kblockd (which needs to take
2887         * this lock).
2888         */
2889        if (from_schedule) {
2890                spin_unlock(q->queue_lock);
2891                blk_run_queue_async(q);
2892        } else {
2893                __blk_run_queue(q);
2894                spin_unlock(q->queue_lock);
2895        }
2896
2897}
2898
2899static void flush_plug_callbacks(struct blk_plug *plug)
2900{
2901        LIST_HEAD(callbacks);
2902
2903        if (list_empty(&plug->cb_list))
2904                return;
2905
2906        list_splice_init(&plug->cb_list, &callbacks);
2907
2908        while (!list_empty(&callbacks)) {
2909                struct blk_plug_cb *cb = list_first_entry(&callbacks,
2910                                                          struct blk_plug_cb,
2911                                                          list);
2912                list_del(&cb->list);
2913                cb->callback(cb);
2914        }
2915}
2916
2917void blk_flush_plug_list(struct blk_plug *plug, bool from_schedule)
2918{
2919        struct request_queue *q;
2920        unsigned long flags;
2921        struct request *rq;
2922        LIST_HEAD(list);
2923        unsigned int depth;
2924
2925        BUG_ON(plug->magic != PLUG_MAGIC);
2926
2927        flush_plug_callbacks(plug);
2928        if (list_empty(&plug->list))
2929                return;
2930
2931        list_splice_init(&plug->list, &list);
2932
2933        if (plug->should_sort) {
2934                list_sort(NULL, &list, plug_rq_cmp);
2935                plug->should_sort = 0;
2936        }
2937
2938        q = NULL;
2939        depth = 0;
2940
2941        /*
2942         * Save and disable interrupts here, to avoid doing it for every
2943         * queue lock we have to take.
2944         */
2945        local_irq_save(flags);
2946        while (!list_empty(&list)) {
2947                rq = list_entry_rq(list.next);
2948                list_del_init(&rq->queuelist);
2949                BUG_ON(!rq->q);
2950                if (rq->q != q) {
2951                        /*
2952                         * This drops the queue lock
2953                         */
2954                        if (q)
2955                                queue_unplugged(q, depth, from_schedule);
2956                        q = rq->q;
2957                        depth = 0;
2958                        spin_lock(q->queue_lock);
2959                }
2960
2961                /*
2962                 * Short-circuit if @q is dead
2963                 */
2964                if (unlikely(blk_queue_dead(q))) {
2965                        __blk_end_request_all(rq, -ENODEV);
2966                        continue;
2967                }
2968
2969                /*
2970                 * rq is already accounted, so use raw insert
2971                 */
2972                if (rq->cmd_flags & (REQ_FLUSH | REQ_FUA))
2973                        __elv_add_request(q, rq, ELEVATOR_INSERT_FLUSH);
2974                else
2975                        __elv_add_request(q, rq, ELEVATOR_INSERT_SORT_MERGE);
2976
2977                depth++;
2978        }
2979
2980        /*
2981         * This drops the queue lock
2982         */
2983        if (q)
2984                queue_unplugged(q, depth, from_schedule);
2985
2986        local_irq_restore(flags);
2987}
2988
2989void blk_finish_plug(struct blk_plug *plug)
2990{
2991        blk_flush_plug_list(plug, false);
2992
2993        if (plug == current->plug)
2994                current->plug = NULL;
2995}
2996EXPORT_SYMBOL(blk_finish_plug);
2997
2998int __init blk_dev_init(void)
2999{
3000        BUILD_BUG_ON(__REQ_NR_BITS > 8 *
3001                        sizeof(((struct request *)0)->cmd_flags));
3002
3003        /* used for unplugging and affects IO latency/throughput - HIGHPRI */
3004        kblockd_workqueue = alloc_workqueue("kblockd",
3005                                            WQ_MEM_RECLAIM | WQ_HIGHPRI, 0);
3006        if (!kblockd_workqueue)
3007                panic("Failed to create kblockd\n");
3008
3009        request_cachep = kmem_cache_create("blkdev_requests",
3010                        sizeof(struct request), 0, SLAB_PANIC, NULL);
3011
3012        blk_requestq_cachep = kmem_cache_create("blkdev_queue",
3013                        sizeof(struct request_queue), 0, SLAB_PANIC, NULL);
3014
3015        return 0;
3016}
3017
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