/* * Copyright (C) 1991, 1992 Linus Torvalds * Copyright (C) 1994, Karl Keyte: Added support for disk statistics * Elevator latency, (C) 2000 Andrea Arcangeli SuSE * Queue request tables / lock, selectable elevator, Jens Axboe * kernel-doc documentation started by NeilBrown * - July2000 * bio rewrite, highmem i/o, etc, Jens Axboe - may 2001 */ /* * This handles all read/write requests to block devices */ #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #define CREATE_TRACE_POINTS #include #include "blk.h" EXPORT_TRACEPOINT_SYMBOL_GPL(block_bio_remap); EXPORT_TRACEPOINT_SYMBOL_GPL(block_rq_remap); EXPORT_TRACEPOINT_SYMBOL_GPL(block_bio_complete); static int __make_request(struct request_queue *q, struct bio *bio); /* * For the allocated request tables */ static struct kmem_cache *request_cachep; /* * For queue allocation */ struct kmem_cache *blk_requestq_cachep; /* * Controlling structure to kblockd */ static struct workqueue_struct *kblockd_workqueue; static void drive_stat_acct(struct request *rq, int new_io) { struct hd_struct *part; int rw = rq_data_dir(rq); int cpu; if (!blk_do_io_stat(rq)) return; cpu = part_stat_lock(); if (!new_io) { part = rq->part; part_stat_inc(cpu, part, merges[rw]); } else { part = disk_map_sector_rcu(rq->rq_disk, blk_rq_pos(rq)); if (!hd_struct_try_get(part)) { /* * The partition is already being removed, * the request will be accounted on the disk only * * We take a reference on disk->part0 although that * partition will never be deleted, so we can treat * it as any other partition. */ part = &rq->rq_disk->part0; hd_struct_get(part); } part_round_stats(cpu, part); part_inc_in_flight(part, rw); rq->part = part; } part_stat_unlock(); } void blk_queue_congestion_threshold(struct request_queue *q) { int nr; nr = q->nr_requests - (q->nr_requests / 8) + 1; if (nr > q->nr_requests) nr = q->nr_requests; q->nr_congestion_on = nr; nr = q->nr_requests - (q->nr_requests / 8) - (q->nr_requests / 16) - 1; if (nr < 1) nr = 1; q->nr_congestion_off = nr; } /** * blk_get_backing_dev_info - get the address of a queue's backing_dev_info * @bdev: device * * Locates the passed device's request queue and returns the address of its * backing_dev_info * * Will return NULL if the request queue cannot be located. */ struct backing_dev_info *blk_get_backing_dev_info(struct block_device *bdev) { struct backing_dev_info *ret = NULL; struct request_queue *q = bdev_get_queue(bdev); if (q) ret = &q->backing_dev_info; return ret; } EXPORT_SYMBOL(blk_get_backing_dev_info); void blk_rq_init(struct request_queue *q, struct request *rq) { memset(rq, 0, sizeof(*rq)); INIT_LIST_HEAD(&rq->queuelist); INIT_LIST_HEAD(&rq->timeout_list); rq->cpu = -1; rq->q = q; rq->__sector = (sector_t) -1; INIT_HLIST_NODE(&rq->hash); RB_CLEAR_NODE(&rq->rb_node); rq->cmd = rq->__cmd; rq->cmd_len = BLK_MAX_CDB; rq->tag = -1; rq->ref_count = 1; rq->start_time = jiffies; set_start_time_ns(rq); rq->part = NULL; } EXPORT_SYMBOL(blk_rq_init); static void req_bio_endio(struct request *rq, struct bio *bio, unsigned int nbytes, int error) { if (error) clear_bit(BIO_UPTODATE, &bio->bi_flags); else if (!test_bit(BIO_UPTODATE, &bio->bi_flags)) error = -EIO; if (unlikely(nbytes > bio->bi_size)) { printk(KERN_ERR "%s: want %u bytes done, %u left\n", __func__, nbytes, bio->bi_size); nbytes = bio->bi_size; } if (unlikely(rq->cmd_flags & REQ_QUIET)) set_bit(BIO_QUIET, &bio->bi_flags); bio->bi_size -= nbytes; bio->bi_sector += (nbytes >> 9); if (bio_integrity(bio)) bio_integrity_advance(bio, nbytes); /* don't actually finish bio if it's part of flush sequence */ if (bio->bi_size == 0 && !(rq->cmd_flags & REQ_FLUSH_SEQ)) bio_endio(bio, error); } void blk_dump_rq_flags(struct request *rq, char *msg) { int bit; printk(KERN_INFO "%s: dev %s: type=%x, flags=%x\n", msg, rq->rq_disk ? rq->rq_disk->disk_name : "?", rq->cmd_type, rq->cmd_flags); printk(KERN_INFO " sector %llu, nr/cnr %u/%u\n", (unsigned long long)blk_rq_pos(rq), blk_rq_sectors(rq), blk_rq_cur_sectors(rq)); printk(KERN_INFO " bio %p, biotail %p, buffer %p, len %u\n", rq->bio, rq->biotail, rq->buffer, blk_rq_bytes(rq)); if (rq->cmd_type == REQ_TYPE_BLOCK_PC) { printk(KERN_INFO " cdb: "); for (bit = 0; bit < BLK_MAX_CDB; bit++) printk("%02x ", rq->cmd[bit]); printk("\n"); } } EXPORT_SYMBOL(blk_dump_rq_flags); static void blk_delay_work(struct work_struct *work) { struct request_queue *q; q = container_of(work, struct request_queue, delay_work.work); spin_lock_irq(q->queue_lock); __blk_run_queue(q); spin_unlock_irq(q->queue_lock); } /** * blk_delay_queue - restart queueing after defined interval * @q: The &struct request_queue in question * @msecs: Delay in msecs * * Description: * Sometimes queueing needs to be postponed for a little while, to allow * resources to come back. This function will make sure that queueing is * restarted around the specified time. */ void blk_delay_queue(struct request_queue *q, unsigned long msecs) { queue_delayed_work(kblockd_workqueue, &q->delay_work, msecs_to_jiffies(msecs)); } EXPORT_SYMBOL(blk_delay_queue); /** * blk_start_queue - restart a previously stopped queue * @q: The &struct request_queue in question * * Description: * blk_start_queue() will clear the stop flag on the queue, and call * the request_fn for the queue if it was in a stopped state when * entered. Also see blk_stop_queue(). Queue lock must be held. **/ void blk_start_queue(struct request_queue *q) { WARN_ON(!irqs_disabled()); queue_flag_clear(QUEUE_FLAG_STOPPED, q); __blk_run_queue(q); } EXPORT_SYMBOL(blk_start_queue); /** * blk_stop_queue - stop a queue * @q: The &struct request_queue in question * * Description: * The Linux block layer assumes that a block driver will consume all * entries on the request queue when the request_fn strategy is called. * Often this will not happen, because of hardware limitations (queue * depth settings). If a device driver gets a 'queue full' response, * or if it simply chooses not to queue more I/O at one point, it can * call this function to prevent the request_fn from being called until * the driver has signalled it's ready to go again. This happens by calling * blk_start_queue() to restart queue operations. Queue lock must be held. **/ void blk_stop_queue(struct request_queue *q) { __cancel_delayed_work(&q->delay_work); queue_flag_set(QUEUE_FLAG_STOPPED, q); } EXPORT_SYMBOL(blk_stop_queue); /** * blk_sync_queue - cancel any pending callbacks on a queue * @q: the queue * * Description: * The block layer may perform asynchronous callback activity * on a queue, such as calling the unplug function after a timeout. * A block device may call blk_sync_queue to ensure that any * such activity is cancelled, thus allowing it to release resources * that the callbacks might use. The caller must already have made sure * that its ->make_request_fn will not re-add plugging prior to calling * this function. * * This function does not cancel any asynchronous activity arising * out of elevator or throttling code. That would require elevaotor_exit() * and blk_throtl_exit() to be called with queue lock initialized. * */ void blk_sync_queue(struct request_queue *q) { del_timer_sync(&q->timeout); cancel_delayed_work_sync(&q->delay_work); } EXPORT_SYMBOL(blk_sync_queue); /** * __blk_run_queue - run a single device queue * @q: The queue to run * * Description: * See @blk_run_queue. This variant must be called with the queue lock * held and interrupts disabled. */ void __blk_run_queue(struct request_queue *q) { if (unlikely(blk_queue_stopped(q))) return; q->request_fn(q); } EXPORT_SYMBOL(__blk_run_queue); /** * blk_run_queue_async - run a single device queue in workqueue context * @q: The queue to run * * Description: * Tells kblockd to perform the equivalent of @blk_run_queue on behalf * of us. */ void blk_run_queue_async(struct request_queue *q) { if (likely(!blk_queue_stopped(q))) { __cancel_delayed_work(&q->delay_work); queue_delayed_work(kblockd_workqueue, &q->delay_work, 0); } } EXPORT_SYMBOL(blk_run_queue_async); /** * blk_run_queue - run a single device queue * @q: The queue to run * * Description: * Invoke request handling on this queue, if it has pending work to do. * May be used to restart queueing when a request has completed. */ void blk_run_queue(struct request_queue *q) { unsigned long flags; spin_lock_irqsave(q->queue_lock, flags); __blk_run_queue(q); spin_unlock_irqrestore(q->queue_lock, flags); } EXPORT_SYMBOL(blk_run_queue); void blk_put_queue(struct request_queue *q) { kobject_put(&q->kobj); } EXPORT_SYMBOL(blk_put_queue); /* * Note: If a driver supplied the queue lock, it should not zap that lock * unexpectedly as some queue cleanup components like elevator_exit() and * blk_throtl_exit() need queue lock. */ void blk_cleanup_queue(struct request_queue *q) { /* * We know we have process context here, so we can be a little * cautious and ensure that pending block actions on this device * are done before moving on. Going into this function, we should * not have processes doing IO to this device. */ blk_sync_queue(q); del_timer_sync(&q->backing_dev_info.laptop_mode_wb_timer); mutex_lock(&q->sysfs_lock); queue_flag_set_unlocked(QUEUE_FLAG_DEAD, q); mutex_unlock(&q->sysfs_lock); if (q->elevator) elevator_exit(q->elevator); blk_throtl_exit(q); blk_put_queue(q); } EXPORT_SYMBOL(blk_cleanup_queue); static int blk_init_free_list(struct request_queue *q) { struct request_list *rl = &q->rq; if (unlikely(rl->rq_pool)) return 0; rl->count[BLK_RW_SYNC] = rl->count[BLK_RW_ASYNC] = 0; rl->starved[BLK_RW_SYNC] = rl->starved[BLK_RW_ASYNC] = 0; rl->elvpriv = 0; init_waitqueue_head(&rl->wait[BLK_RW_SYNC]); init_waitqueue_head(&rl->wait[BLK_RW_ASYNC]); rl->rq_pool = mempool_create_node(BLKDEV_MIN_RQ, mempool_alloc_slab, mempool_free_slab, request_cachep, q->node); if (!rl->rq_pool) return -ENOMEM; return 0; } struct request_queue *blk_alloc_queue(gfp_t gfp_mask) { return blk_alloc_queue_node(gfp_mask, -1); } EXPORT_SYMBOL(blk_alloc_queue); struct request_queue *blk_alloc_queue_node(gfp_t gfp_mask, int node_id) { struct request_queue *q; int err; q = kmem_cache_alloc_node(blk_requestq_cachep, gfp_mask | __GFP_ZERO, node_id); if (!q) return NULL; q->backing_dev_info.ra_pages = (VM_MAX_READAHEAD * 1024) / PAGE_CACHE_SIZE; q->backing_dev_info.state = 0; q->backing_dev_info.capabilities = BDI_CAP_MAP_COPY; q->backing_dev_info.name = "block"; err = bdi_init(&q->backing_dev_info); if (err) { kmem_cache_free(blk_requestq_cachep, q); return NULL; } if (blk_throtl_init(q)) { kmem_cache_free(blk_requestq_cachep, q); return NULL; } setup_timer(&q->backing_dev_info.laptop_mode_wb_timer, laptop_mode_timer_fn, (unsigned long) q); setup_timer(&q->timeout, blk_rq_timed_out_timer, (unsigned long) q); INIT_LIST_HEAD(&q->timeout_list); INIT_LIST_HEAD(&q->flush_queue[0]); INIT_LIST_HEAD(&q->flush_queue[1]); INIT_LIST_HEAD(&q->flush_data_in_flight); INIT_DELAYED_WORK(&q->delay_work, blk_delay_work); kobject_init(&q->kobj, &blk_queue_ktype); mutex_init(&q->sysfs_lock); spin_lock_init(&q->__queue_lock); /* * By default initialize queue_lock to internal lock and driver can * override it later if need be. */ q->queue_lock = &q->__queue_lock; return q; } EXPORT_SYMBOL(blk_alloc_queue_node); /** * blk_init_queue - prepare a request queue for use with a block device * @rfn: The function to be called to process requests that have been * placed on the queue. * @lock: Request queue spin lock * * Description: * If a block device wishes to use the standard request handling procedures, * which sorts requests and coalesces adjacent requests, then it must * call blk_init_queue(). The function @rfn will be called when there * are requests on the queue that need to be processed. If the device * supports plugging, then @rfn may not be called immediately when requests * are available on the queue, but may be called at some time later instead. * Plugged queues are generally unplugged when a buffer belonging to one * of the requests on the queue is needed, or due to memory pressure. * * @rfn is not required, or even expected, to remove all requests off the * queue, but only as many as it can handle at a time. If it does leave * requests on the queue, it is responsible for arranging that the requests * get dealt with eventually. * * The queue spin lock must be held while manipulating the requests on the * request queue; this lock will be taken also from interrupt context, so irq * disabling is needed for it. * * Function returns a pointer to the initialized request queue, or %NULL if * it didn't succeed. * * Note: * blk_init_queue() must be paired with a blk_cleanup_queue() call * when the block device is deactivated (such as at module unload). **/ struct request_queue *blk_init_queue(request_fn_proc *rfn, spinlock_t *lock) { return blk_init_queue_node(rfn, lock, -1); } EXPORT_SYMBOL(blk_init_queue); struct request_queue * blk_init_queue_node(request_fn_proc *rfn, spinlock_t *lock, int node_id) { struct request_queue *uninit_q, *q; uninit_q = blk_alloc_queue_node(GFP_KERNEL, node_id); if (!uninit_q) return NULL; q = blk_init_allocated_queue_node(uninit_q, rfn, lock, node_id); if (!q) blk_cleanup_queue(uninit_q); return q; } EXPORT_SYMBOL(blk_init_queue_node); struct request_queue * blk_init_allocated_queue(struct request_queue *q, request_fn_proc *rfn, spinlock_t *lock) { return blk_init_allocated_queue_node(q, rfn, lock, -1); } EXPORT_SYMBOL(blk_init_allocated_queue); struct request_queue * blk_init_allocated_queue_node(struct request_queue *q, request_fn_proc *rfn, spinlock_t *lock, int node_id) { if (!q) return NULL; q->node = node_id; if (blk_init_free_list(q)) return NULL; q->request_fn = rfn; q->prep_rq_fn = NULL; q->unprep_rq_fn = NULL; q->queue_flags = QUEUE_FLAG_DEFAULT; /* Override internal queue lock with supplied lock pointer */ if (lock) q->queue_lock = lock; /* * This also sets hw/phys segments, boundary and size */ blk_queue_make_request(q, __make_request); q->sg_reserved_size = INT_MAX; /* * all done */ if (!elevator_init(q, NULL)) { blk_queue_congestion_threshold(q); return q; } return NULL; } EXPORT_SYMBOL(blk_init_allocated_queue_node); int blk_get_queue(struct request_queue *q) { if (likely(!test_bit(QUEUE_FLAG_DEAD, &q->queue_flags))) { kobject_get(&q->kobj); return 0; } return 1; } EXPORT_SYMBOL(blk_get_queue); static inline void blk_free_request(struct request_queue *q, struct request *rq) { BUG_ON(rq->cmd_flags & REQ_ON_PLUG); if (rq->cmd_flags & REQ_ELVPRIV) elv_put_request(q, rq); mempool_free(rq, q->rq.rq_pool); } static struct request * blk_alloc_request(struct request_queue *q, int flags, int priv, gfp_t gfp_mask) { struct request *rq = mempool_alloc(q->rq.rq_pool, gfp_mask); if (!rq) return NULL; blk_rq_init(q, rq); rq->cmd_flags = flags | REQ_ALLOCED; if (priv) { if (unlikely(elv_set_request(q, rq, gfp_mask))) { mempool_free(rq, q->rq.rq_pool); return NULL; } rq->cmd_flags |= REQ_ELVPRIV; } return rq; } /* * ioc_batching returns true if the ioc is a valid batching request and * should be given priority access to a request. */ static inline int ioc_batching(struct request_queue *q, struct io_context *ioc) { if (!ioc) return 0; /* * Make sure the process is able to allocate at least 1 request * even if the batch times out, otherwise we could theoretically * lose wakeups. */ return ioc->nr_batch_requests == q->nr_batching || (ioc->nr_batch_requests > 0 && time_before(jiffies, ioc->last_waited + BLK_BATCH_TIME)); } /* * ioc_set_batching sets ioc to be a new "batcher" if it is not one. This * will cause the process to be a "batcher" on all queues in the system. This * is the behaviour we want though - once it gets a wakeup it should be given * a nice run. */ static void ioc_set_batching(struct request_queue *q, struct io_context *ioc) { if (!ioc || ioc_batching(q, ioc)) return; ioc->nr_batch_requests = q->nr_batching; ioc->last_waited = jiffies; } static void __freed_request(struct request_queue *q, int sync) { struct request_list *rl = &q->rq; if (rl->count[sync] < queue_congestion_off_threshold(q)) blk_clear_queue_congested(q, sync); if (rl->count[sync] + 1 <= q->nr_requests) { if (waitqueue_active(&rl->wait[sync])) wake_up(&rl->wait[sync]); blk_clear_queue_full(q, sync); } } /* * A request has just been released. Account for it, update the full and * congestion status, wake up any waiters. Called under q->queue_lock. */ static void freed_request(struct request_queue *q, int sync, int priv) { struct request_list *rl = &q->rq; rl->count[sync]--; if (priv) rl->elvpriv--; __freed_request(q, sync); if (unlikely(rl->starved[sync ^ 1])) __freed_request(q, sync ^ 1); } /* * Determine if elevator data should be initialized when allocating the * request associated with @bio. */ static bool blk_rq_should_init_elevator(struct bio *bio) { if (!bio) return true; /* * Flush requests do not use the elevator so skip initialization. * This allows a request to share the flush and elevator data. */ if (bio->bi_rw & (REQ_FLUSH | REQ_FUA)) return false; return true; } /* * Get a free request, queue_lock must be held. * Returns NULL on failure, with queue_lock held. * Returns !NULL on success, with queue_lock *not held*. */ static struct request *get_request(struct request_queue *q, int rw_flags, struct bio *bio, gfp_t gfp_mask) { struct request *rq = NULL; struct request_list *rl = &q->rq; struct io_context *ioc = NULL; const bool is_sync = rw_is_sync(rw_flags) != 0; int may_queue, priv = 0; may_queue = elv_may_queue(q, rw_flags); if (may_queue == ELV_MQUEUE_NO) goto rq_starved; if (rl->count[is_sync]+1 >= queue_congestion_on_threshold(q)) { if (rl->count[is_sync]+1 >= q->nr_requests) { ioc = current_io_context(GFP_ATOMIC, q->node); /* * The queue will fill after this allocation, so set * it as full, and mark this process as "batching". * This process will be allowed to complete a batch of * requests, others will be blocked. */ if (!blk_queue_full(q, is_sync)) { ioc_set_batching(q, ioc); blk_set_queue_full(q, is_sync); } else { if (may_queue != ELV_MQUEUE_MUST && !ioc_batching(q, ioc)) { /* * The queue is full and the allocating * process is not a "batcher", and not * exempted by the IO scheduler */ goto out; } } } blk_set_queue_congested(q, is_sync); } /* * Only allow batching queuers to allocate up to 50% over the defined * limit of requests, otherwise we could have thousands of requests * allocated with any setting of ->nr_requests */ if (rl->count[is_sync] >= (3 * q->nr_requests / 2)) goto out; rl->count[is_sync]++; rl->starved[is_sync] = 0; if (blk_rq_should_init_elevator(bio)) { priv = !test_bit(QUEUE_FLAG_ELVSWITCH, &q->queue_flags); if (priv) rl->elvpriv++; } if (blk_queue_io_stat(q)) rw_flags |= REQ_IO_STAT; spin_unlock_irq(q->queue_lock); rq = blk_alloc_request(q, rw_flags, priv, gfp_mask); if (unlikely(!rq)) { /* * Allocation failed presumably due to memory. Undo anything * we might have messed up. * * Allocating task should really be put onto the front of the * wait queue, but this is pretty rare. */ spin_lock_irq(q->queue_lock); freed_request(q, is_sync, priv); /* * in the very unlikely event that allocation failed and no * requests for this direction was pending, mark us starved * so that freeing of a request in the other direction will * notice us. another possible fix would be to split the * rq mempool into READ and WRITE */ rq_starved: if (unlikely(rl->count[is_sync] == 0)) rl->starved[is_sync] = 1; goto out; } /* * ioc may be NULL here, and ioc_batching will be false. That's * OK, if the queue is under the request limit then requests need * not count toward the nr_batch_requests limit. There will always * be some limit enforced by BLK_BATCH_TIME. */ if (ioc_batching(q, ioc)) ioc->nr_batch_requests--; trace_block_getrq(q, bio, rw_flags & 1); out: return rq; } /* * No available requests for this queue, wait for some requests to become * available. * * Called with q->queue_lock held, and returns with it unlocked. */ static struct request *get_request_wait(struct request_queue *q, int rw_flags, struct bio *bio) { const bool is_sync = rw_is_sync(rw_flags) != 0; struct request *rq; rq = get_request(q, rw_flags, bio, GFP_NOIO); while (!rq) { DEFINE_WAIT(wait); struct io_context *ioc; struct request_list *rl = &q->rq; prepare_to_wait_exclusive(&rl->wait[is_sync], &wait, TASK_UNINTERRUPTIBLE); trace_block_sleeprq(q, bio, rw_flags & 1); spin_unlock_irq(q->queue_lock); io_schedule(); /* * After sleeping, we become a "batching" process and * will be able to allocate at least one request, and * up to a big batch of them for a small period time. * See ioc_batching, ioc_set_batching */ ioc = current_io_context(GFP_NOIO, q->node); ioc_set_batching(q, ioc); spin_lock_irq(q->queue_lock); finish_wait(&rl->wait[is_sync], &wait); rq = get_request(q, rw_flags, bio, GFP_NOIO); }; return rq; } struct request *blk_get_request(struct request_queue *q, int rw, gfp_t gfp_mask) { struct request *rq; /*== 20161123 AVM/WKR don't access dead queues ==*/ if (unlikely(test_bit(QUEUE_FLAG_DEAD, &q->queue_flags))) { return NULL; } BUG_ON(rw != READ && rw != WRITE); spin_lock_irq(q->queue_lock); if (gfp_mask & __GFP_WAIT) { rq = get_request_wait(q, rw, NULL); } else { rq = get_request(q, rw, NULL, gfp_mask); if (!rq) spin_unlock_irq(q->queue_lock); } /* q->queue_lock is unlocked at this point */ return rq; } EXPORT_SYMBOL(blk_get_request); /** * blk_make_request - given a bio, allocate a corresponding struct request. * @q: target request queue * @bio: The bio describing the memory mappings that will be submitted for IO. * It may be a chained-bio properly constructed by block/bio layer. * @gfp_mask: gfp flags to be used for memory allocation * * blk_make_request is the parallel of generic_make_request for BLOCK_PC * type commands. Where the struct request needs to be farther initialized by * the caller. It is passed a &struct bio, which describes the memory info of * the I/O transfer. * * The caller of blk_make_request must make sure that bi_io_vec * are set to describe the memory buffers. That bio_data_dir() will return * the needed direction of the request. (And all bio's in the passed bio-chain * are properly set accordingly) * * If called under none-sleepable conditions, mapped bio buffers must not * need bouncing, by calling the appropriate masked or flagged allocator, * suitable for the target device. Otherwise the call to blk_queue_bounce will * BUG. * * WARNING: When allocating/cloning a bio-chain, careful consideration should be * given to how you allocate bios. In particular, you cannot use __GFP_WAIT for * anything but the first bio in the chain. Otherwise you risk waiting for IO * completion of a bio that hasn't been submitted yet, thus resulting in a * deadlock. Alternatively bios should be allocated using bio_kmalloc() instead * of bio_alloc(), as that avoids the mempool deadlock. * If possible a big IO should be split into smaller parts when allocation * fails. Partial allocation should not be an error, or you risk a live-lock. */ struct request *blk_make_request(struct request_queue *q, struct bio *bio, gfp_t gfp_mask) { struct request *rq = blk_get_request(q, bio_data_dir(bio), gfp_mask); if (unlikely(!rq)) return ERR_PTR(-ENOMEM); for_each_bio(bio) { struct bio *bounce_bio = bio; int ret; blk_queue_bounce(q, &bounce_bio); ret = blk_rq_append_bio(q, rq, bounce_bio); if (unlikely(ret)) { blk_put_request(rq); return ERR_PTR(ret); } } return rq; } EXPORT_SYMBOL(blk_make_request); /** * blk_requeue_request - put a request back on queue * @q: request queue where request should be inserted * @rq: request to be inserted * * Description: * Drivers often keep queueing requests until the hardware cannot accept * more, when that condition happens we need to put the request back * on the queue. Must be called with queue lock held. */ void blk_requeue_request(struct request_queue *q, struct request *rq) { blk_delete_timer(rq); blk_clear_rq_complete(rq); trace_block_rq_requeue(q, rq); if (blk_rq_tagged(rq)) blk_queue_end_tag(q, rq); BUG_ON(blk_queued_rq(rq)); elv_requeue_request(q, rq); } EXPORT_SYMBOL(blk_requeue_request); static void add_acct_request(struct request_queue *q, struct request *rq, int where) { drive_stat_acct(rq, 1); __elv_add_request(q, rq, where); } /** * blk_insert_request - insert a special request into a request queue * @q: request queue where request should be inserted * @rq: request to be inserted * @at_head: insert request at head or tail of queue * @data: private data * * Description: * Many block devices need to execute commands asynchronously, so they don't * block the whole kernel from preemption during request execution. This is * accomplished normally by inserting aritficial requests tagged as * REQ_TYPE_SPECIAL in to the corresponding request queue, and letting them * be scheduled for actual execution by the request queue. * * We have the option of inserting the head or the tail of the queue. * Typically we use the tail for new ioctls and so forth. We use the head * of the queue for things like a QUEUE_FULL message from a device, or a * host that is unable to accept a particular command. */ void blk_insert_request(struct request_queue *q, struct request *rq, int at_head, void *data) { int where = at_head ? ELEVATOR_INSERT_FRONT : ELEVATOR_INSERT_BACK; unsigned long flags; /* * tell I/O scheduler that this isn't a regular read/write (ie it * must not attempt merges on this) and that it acts as a soft * barrier */ rq->cmd_type = REQ_TYPE_SPECIAL; rq->special = data; spin_lock_irqsave(q->queue_lock, flags); /* * If command is tagged, release the tag */ if (blk_rq_tagged(rq)) blk_queue_end_tag(q, rq); add_acct_request(q, rq, where); __blk_run_queue(q); spin_unlock_irqrestore(q->queue_lock, flags); } EXPORT_SYMBOL(blk_insert_request); static void part_round_stats_single(int cpu, struct hd_struct *part, unsigned long now) { if (now == part->stamp) return; if (part_in_flight(part)) { __part_stat_add(cpu, part, time_in_queue, part_in_flight(part) * (now - part->stamp)); __part_stat_add(cpu, part, io_ticks, (now - part->stamp)); } part->stamp = now; } /** * part_round_stats() - Round off the performance stats on a struct disk_stats. * @cpu: cpu number for stats access * @part: target partition * * The average IO queue length and utilisation statistics are maintained * by observing the current state of the queue length and the amount of * time it has been in this state for. * * Normally, that accounting is done on IO completion, but that can result * in more than a second's worth of IO being accounted for within any one * second, leading to >100% utilisation. To deal with that, we call this * function to do a round-off before returning the results when reading * /proc/diskstats. This accounts immediately for all queue usage up to * the current jiffies and restarts the counters again. */ void part_round_stats(int cpu, struct hd_struct *part) { unsigned long now = jiffies; if (part->partno) part_round_stats_single(cpu, &part_to_disk(part)->part0, now); part_round_stats_single(cpu, part, now); } EXPORT_SYMBOL_GPL(part_round_stats); /* * queue lock must be held */ void __blk_put_request(struct request_queue *q, struct request *req) { if (unlikely(!q)) return; if (unlikely(--req->ref_count)) return; elv_completed_request(q, req); /* this is a bio leak */ WARN_ON(req->bio != NULL); /* * Request may not have originated from ll_rw_blk. if not, * it didn't come out of our reserved rq pools */ if (req->cmd_flags & REQ_ALLOCED) { int is_sync = rq_is_sync(req) != 0; int priv = req->cmd_flags & REQ_ELVPRIV; BUG_ON(!list_empty(&req->queuelist)); BUG_ON(!hlist_unhashed(&req->hash)); blk_free_request(q, req); freed_request(q, is_sync, priv); } } EXPORT_SYMBOL_GPL(__blk_put_request); void blk_put_request(struct request *req) { unsigned long flags; struct request_queue *q; /*== 20161124 AVM/WKR don't access empty req ==*/ if (unlikely(!req)) { return; } q = req->q; spin_lock_irqsave(q->queue_lock, flags); __blk_put_request(q, req); spin_unlock_irqrestore(q->queue_lock, flags); } EXPORT_SYMBOL(blk_put_request); /** * blk_add_request_payload - add a payload to a request * @rq: request to update * @page: page backing the payload * @len: length of the payload. * * This allows to later add a payload to an already submitted request by * a block driver. The driver needs to take care of freeing the payload * itself. * * Note that this is a quite horrible hack and nothing but handling of * discard requests should ever use it. */ void blk_add_request_payload(struct request *rq, struct page *page, unsigned int len) { struct bio *bio = rq->bio; bio->bi_io_vec->bv_page = page; bio->bi_io_vec->bv_offset = 0; bio->bi_io_vec->bv_len = len; bio->bi_size = len; bio->bi_vcnt = 1; bio->bi_phys_segments = 1; rq->__data_len = rq->resid_len = len; rq->nr_phys_segments = 1; rq->buffer = bio_data(bio); } EXPORT_SYMBOL_GPL(blk_add_request_payload); static bool bio_attempt_back_merge(struct request_queue *q, struct request *req, struct bio *bio) { const int ff = bio->bi_rw & REQ_FAILFAST_MASK; /* * Debug stuff, kill later */ if (!rq_mergeable(req)) { blk_dump_rq_flags(req, "back"); return false; } if (!ll_back_merge_fn(q, req, bio)) return false; trace_block_bio_backmerge(q, bio); if ((req->cmd_flags & REQ_FAILFAST_MASK) != ff) blk_rq_set_mixed_merge(req); req->biotail->bi_next = bio; req->biotail = bio; req->__data_len += bio->bi_size; req->ioprio = ioprio_best(req->ioprio, bio_prio(bio)); drive_stat_acct(req, 0); return true; } static bool bio_attempt_front_merge(struct request_queue *q, struct request *req, struct bio *bio) { const int ff = bio->bi_rw & REQ_FAILFAST_MASK; /*--- sector_t sector; ---*/ /* * Debug stuff, kill later */ if (!rq_mergeable(req)) { blk_dump_rq_flags(req, "front"); return false; } if (!ll_front_merge_fn(q, req, bio)) return false; trace_block_bio_frontmerge(q, bio); if ((req->cmd_flags & REQ_FAILFAST_MASK) != ff) blk_rq_set_mixed_merge(req); /*--- sector = bio->bi_sector; ---*/ bio->bi_next = req->bio; req->bio = bio; /* * may not be valid. if the low level driver said * it didn't need a bounce buffer then it better * not touch req->buffer either... */ req->buffer = bio_data(bio); req->__sector = bio->bi_sector; req->__data_len += bio->bi_size; req->ioprio = ioprio_best(req->ioprio, bio_prio(bio)); drive_stat_acct(req, 0); return true; } /* * Attempts to merge with the plugged list in the current process. Returns * true if merge was successful, otherwise false. */ static bool attempt_plug_merge(struct task_struct *tsk, struct request_queue *q, struct bio *bio) { struct blk_plug *plug; struct request *rq; bool ret = false; plug = tsk->plug; if (!plug) goto out; list_for_each_entry_reverse(rq, &plug->list, queuelist) { int el_ret; if (rq->q != q) continue; el_ret = elv_try_merge(rq, bio); if (el_ret == ELEVATOR_BACK_MERGE) { ret = bio_attempt_back_merge(q, rq, bio); if (ret) break; } else if (el_ret == ELEVATOR_FRONT_MERGE) { ret = bio_attempt_front_merge(q, rq, bio); if (ret) break; } } out: return ret; } void init_request_from_bio(struct request *req, struct bio *bio) { req->cpu = bio->bi_comp_cpu; req->cmd_type = REQ_TYPE_FS; req->cmd_flags |= bio->bi_rw & REQ_COMMON_MASK; if (bio->bi_rw & REQ_RAHEAD) req->cmd_flags |= REQ_FAILFAST_MASK; req->errors = 0; req->__sector = bio->bi_sector; req->ioprio = bio_prio(bio); blk_rq_bio_prep(req->q, req, bio); } static int __make_request(struct request_queue *q, struct bio *bio) { const bool sync = !!(bio->bi_rw & REQ_SYNC); struct blk_plug *plug; int el_ret, rw_flags, where = ELEVATOR_INSERT_SORT; struct request *req; /* * low level driver can indicate that it wants pages above a * certain limit bounced to low memory (ie for highmem, or even * ISA dma in theory) */ blk_queue_bounce(q, &bio); if (bio->bi_rw & (REQ_FLUSH | REQ_FUA)) { spin_lock_irq(q->queue_lock); where = ELEVATOR_INSERT_FLUSH; goto get_rq; } /* * Check if we can merge with the plugged list before grabbing * any locks. */ if (attempt_plug_merge(current, q, bio)) goto out; spin_lock_irq(q->queue_lock); el_ret = elv_merge(q, &req, bio); if (el_ret == ELEVATOR_BACK_MERGE) { BUG_ON(req->cmd_flags & REQ_ON_PLUG); if (bio_attempt_back_merge(q, req, bio)) { if (!attempt_back_merge(q, req)) elv_merged_request(q, req, el_ret); goto out_unlock; } } else if (el_ret == ELEVATOR_FRONT_MERGE) { BUG_ON(req->cmd_flags & REQ_ON_PLUG); if (bio_attempt_front_merge(q, req, bio)) { if (!attempt_front_merge(q, req)) elv_merged_request(q, req, el_ret); goto out_unlock; } } get_rq: /* * This sync check and mask will be re-done in init_request_from_bio(), * but we need to set it earlier to expose the sync flag to the * rq allocator and io schedulers. */ rw_flags = bio_data_dir(bio); if (sync) rw_flags |= REQ_SYNC; /* * Grab a free request. This is might sleep but can not fail. * Returns with the queue unlocked. */ req = get_request_wait(q, rw_flags, bio); /* * After dropping the lock and possibly sleeping here, our request * may now be mergeable after it had proven unmergeable (above). * We don't worry about that case for efficiency. It won't happen * often, and the elevators are able to handle it. */ init_request_from_bio(req, bio); if (test_bit(QUEUE_FLAG_SAME_COMP, &q->queue_flags) || bio_flagged(bio, BIO_CPU_AFFINE)) { req->cpu = blk_cpu_to_group(get_cpu()); put_cpu(); } plug = current->plug; if (plug) { /* * If this is the first request added after a plug, fire * of a plug trace. If others have been added before, check * if we have multiple devices in this plug. If so, make a * note to sort the list before dispatch. */ if (list_empty(&plug->list)) trace_block_plug(q); else if (!plug->should_sort) { struct request *__rq; __rq = list_entry_rq(plug->list.prev); if (__rq->q != q) plug->should_sort = 1; } /* * Debug flag, kill later */ req->cmd_flags |= REQ_ON_PLUG; list_add_tail(&req->queuelist, &plug->list); drive_stat_acct(req, 1); } else { spin_lock_irq(q->queue_lock); add_acct_request(q, req, where); __blk_run_queue(q); out_unlock: spin_unlock_irq(q->queue_lock); } out: return 0; } /* * If bio->bi_dev is a partition, remap the location */ static inline void blk_partition_remap(struct bio *bio) { struct block_device *bdev = bio->bi_bdev; if (bio_sectors(bio) && bdev != bdev->bd_contains) { struct hd_struct *p = bdev->bd_part; bio->bi_sector += p->start_sect; bio->bi_bdev = bdev->bd_contains; trace_block_bio_remap(bdev_get_queue(bio->bi_bdev), bio, bdev->bd_dev, bio->bi_sector - p->start_sect); } } static void handle_bad_sector(struct bio *bio) { char b[BDEVNAME_SIZE]; printk(KERN_INFO "attempt to access beyond end of device\n"); printk(KERN_INFO "%s: rw=%ld, want=%Lu, limit=%Lu\n", bdevname(bio->bi_bdev, b), bio->bi_rw, (unsigned long long)bio->bi_sector + bio_sectors(bio), (long long)(i_size_read(bio->bi_bdev->bd_inode) >> 9)); set_bit(BIO_EOF, &bio->bi_flags); } #ifdef CONFIG_FAIL_MAKE_REQUEST static DECLARE_FAULT_ATTR(fail_make_request); static int __init setup_fail_make_request(char *str) { return setup_fault_attr(&fail_make_request, str); } __setup("fail_make_request=", setup_fail_make_request); static int should_fail_request(struct bio *bio) { struct hd_struct *part = bio->bi_bdev->bd_part; if (part_to_disk(part)->part0.make_it_fail || part->make_it_fail) return should_fail(&fail_make_request, bio->bi_size); return 0; } static int __init fail_make_request_debugfs(void) { return init_fault_attr_dentries(&fail_make_request, "fail_make_request"); } late_initcall(fail_make_request_debugfs); #else /* CONFIG_FAIL_MAKE_REQUEST */ static inline int should_fail_request(struct bio *bio) { return 0; } #endif /* CONFIG_FAIL_MAKE_REQUEST */ /* * Check whether this bio extends beyond the end of the device. */ static inline int bio_check_eod(struct bio *bio, unsigned int nr_sectors) { sector_t maxsector; if (!nr_sectors) return 0; /* Test device or partition size, when known. */ maxsector = i_size_read(bio->bi_bdev->bd_inode) >> 9; if (maxsector) { sector_t sector = bio->bi_sector; if (maxsector < nr_sectors || maxsector - nr_sectors < sector) { /* * This may well happen - the kernel calls bread() * without checking the size of the device, e.g., when * mounting a device. */ handle_bad_sector(bio); return 1; } } return 0; } /** * generic_make_request - hand a buffer to its device driver for I/O * @bio: The bio describing the location in memory and on the device. * * generic_make_request() is used to make I/O requests of block * devices. It is passed a &struct bio, which describes the I/O that needs * to be done. * * generic_make_request() does not return any status. The * success/failure status of the request, along with notification of * completion, is delivered asynchronously through the bio->bi_end_io * function described (one day) else where. * * The caller of generic_make_request must make sure that bi_io_vec * are set to describe the memory buffer, and that bi_dev and bi_sector are * set to describe the device address, and the * bi_end_io and optionally bi_private are set to describe how * completion notification should be signaled. * * generic_make_request and the drivers it calls may use bi_next if this * bio happens to be merged with someone else, and may change bi_dev and * bi_sector for remaps as it sees fit. So the values of these fields * should NOT be depended on after the call to generic_make_request. */ static inline void __generic_make_request(struct bio *bio) { struct request_queue *q; sector_t old_sector; int ret, nr_sectors = bio_sectors(bio); dev_t old_dev; int err = -EIO; might_sleep(); if (bio_check_eod(bio, nr_sectors)) goto end_io; /* * Resolve the mapping until finished. (drivers are * still free to implement/resolve their own stacking * by explicitly returning 0) * * NOTE: we don't repeat the blk_size check for each new device. * Stacking drivers are expected to know what they are doing. */ old_sector = -1; old_dev = 0; do { char b[BDEVNAME_SIZE]; q = bdev_get_queue(bio->bi_bdev); if (unlikely(!q)) { printk(KERN_ERR "generic_make_request: Trying to access " "nonexistent block-device %s (%Lu)\n", bdevname(bio->bi_bdev, b), (long long) bio->bi_sector); goto end_io; } if (unlikely(!(bio->bi_rw & REQ_DISCARD) && nr_sectors > queue_max_hw_sectors(q))) { printk(KERN_ERR "bio too big device %s (%u > %u)\n", bdevname(bio->bi_bdev, b), bio_sectors(bio), queue_max_hw_sectors(q)); goto end_io; } if (unlikely(test_bit(QUEUE_FLAG_DEAD, &q->queue_flags))) goto end_io; if (should_fail_request(bio)) goto end_io; /* * If this device has partitions, remap block n * of partition p to block n+start(p) of the disk. */ blk_partition_remap(bio); if (bio_integrity_enabled(bio) && bio_integrity_prep(bio)) goto end_io; if (old_sector != -1) trace_block_bio_remap(q, bio, old_dev, old_sector); old_sector = bio->bi_sector; old_dev = bio->bi_bdev->bd_dev; if (bio_check_eod(bio, nr_sectors)) goto end_io; /* * Filter flush bio's early so that make_request based * drivers without flush support don't have to worry * about them. */ if ((bio->bi_rw & (REQ_FLUSH | REQ_FUA)) && !q->flush_flags) { bio->bi_rw &= ~(REQ_FLUSH | REQ_FUA); if (!nr_sectors) { err = 0; goto end_io; } } if ((bio->bi_rw & REQ_DISCARD) && (!blk_queue_discard(q) || ((bio->bi_rw & REQ_SECURE) && !blk_queue_secdiscard(q)))) { err = -EOPNOTSUPP; goto end_io; } blk_throtl_bio(q, &bio); /* * If bio = NULL, bio has been throttled and will be submitted * later. */ if (!bio) break; trace_block_bio_queue(q, bio); ret = q->make_request_fn(q, bio); } while (ret); return; end_io: bio_endio(bio, err); } /* * We only want one ->make_request_fn to be active at a time, * else stack usage with stacked devices could be a problem. * So use current->bio_list to keep a list of requests * submited by a make_request_fn function. * current->bio_list is also used as a flag to say if * generic_make_request is currently active in this task or not. * If it is NULL, then no make_request is active. If it is non-NULL, * then a make_request is active, and new requests should be added * at the tail */ void generic_make_request(struct bio *bio) { struct bio_list bio_list_on_stack; if (current->bio_list) { /* make_request is active */ bio_list_add(current->bio_list, bio); return; } /* following loop may be a bit non-obvious, and so deserves some * explanation. * Before entering the loop, bio->bi_next is NULL (as all callers * ensure that) so we have a list with a single bio. * We pretend that we have just taken it off a longer list, so * we assign bio_list to a pointer to the bio_list_on_stack, * thus initialising the bio_list of new bios to be * added. __generic_make_request may indeed add some more bios * through a recursive call to generic_make_request. If it * did, we find a non-NULL value in bio_list and re-enter the loop * from the top. In this case we really did just take the bio * of the top of the list (no pretending) and so remove it from * bio_list, and call into __generic_make_request again. * * The loop was structured like this to make only one call to * __generic_make_request (which is important as it is large and * inlined) and to keep the structure simple. */ BUG_ON(bio->bi_next); bio_list_init(&bio_list_on_stack); current->bio_list = &bio_list_on_stack; do { __generic_make_request(bio); bio = bio_list_pop(current->bio_list); } while (bio); current->bio_list = NULL; /* deactivate */ } EXPORT_SYMBOL(generic_make_request); /** * submit_bio - submit a bio to the block device layer for I/O * @rw: whether to %READ or %WRITE, or maybe to %READA (read ahead) * @bio: The &struct bio which describes the I/O * * submit_bio() is very similar in purpose to generic_make_request(), and * uses that function to do most of the work. Both are fairly rough * interfaces; @bio must be presetup and ready for I/O. * */ void submit_bio(int rw, struct bio *bio) { int count = bio_sectors(bio); bio->bi_rw |= rw; /* * If it's a regular read/write or a barrier with data attached, * go through the normal accounting stuff before submission. */ if (bio_has_data(bio) && !(rw & REQ_DISCARD)) { if (rw & WRITE) { count_vm_events(PGPGOUT, count); } else { task_io_account_read(bio->bi_size); count_vm_events(PGPGIN, count); } if (unlikely(block_dump)) { char b[BDEVNAME_SIZE]; printk(KERN_DEBUG "%s(%d): %s block %Lu on %s (%u sectors)\n", current->comm, task_pid_nr(current), (rw & WRITE) ? "WRITE" : "READ", (unsigned long long)bio->bi_sector, bdevname(bio->bi_bdev, b), count); } } generic_make_request(bio); } EXPORT_SYMBOL(submit_bio); /** * blk_rq_check_limits - Helper function to check a request for the queue limit * @q: the queue * @rq: the request being checked * * Description: * @rq may have been made based on weaker limitations of upper-level queues * in request stacking drivers, and it may violate the limitation of @q. * Since the block layer and the underlying device driver trust @rq * after it is inserted to @q, it should be checked against @q before * the insertion using this generic function. * * This function should also be useful for request stacking drivers * in some cases below, so export this function. * Request stacking drivers like request-based dm may change the queue * limits while requests are in the queue (e.g. dm's table swapping). * Such request stacking drivers should check those requests agaist * the new queue limits again when they dispatch those requests, * although such checkings are also done against the old queue limits * when submitting requests. */ int blk_rq_check_limits(struct request_queue *q, struct request *rq) { if (rq->cmd_flags & REQ_DISCARD) return 0; if (blk_rq_sectors(rq) > queue_max_sectors(q) || blk_rq_bytes(rq) > queue_max_hw_sectors(q) << 9) { printk(KERN_ERR "%s: over max size limit.\n", __func__); return -EIO; } /* * queue's settings related to segment counting like q->bounce_pfn * may differ from that of other stacking queues. * Recalculate it to check the request correctly on this queue's * limitation. */ blk_recalc_rq_segments(rq); if (rq->nr_phys_segments > queue_max_segments(q)) { printk(KERN_ERR "%s: over max segments limit.\n", __func__); return -EIO; } return 0; } EXPORT_SYMBOL_GPL(blk_rq_check_limits); /** * blk_insert_cloned_request - Helper for stacking drivers to submit a request * @q: the queue to submit the request * @rq: the request being queued */ int blk_insert_cloned_request(struct request_queue *q, struct request *rq) { unsigned long flags; if (blk_rq_check_limits(q, rq)) return -EIO; #ifdef CONFIG_FAIL_MAKE_REQUEST if (rq->rq_disk && rq->rq_disk->part0.make_it_fail && should_fail(&fail_make_request, blk_rq_bytes(rq))) return -EIO; #endif spin_lock_irqsave(q->queue_lock, flags); /* * Submitting request must be dequeued before calling this function * because it will be linked to another request_queue */ BUG_ON(blk_queued_rq(rq)); add_acct_request(q, rq, ELEVATOR_INSERT_BACK); spin_unlock_irqrestore(q->queue_lock, flags); return 0; } EXPORT_SYMBOL_GPL(blk_insert_cloned_request); /** * blk_rq_err_bytes - determine number of bytes till the next failure boundary * @rq: request to examine * * Description: * A request could be merge of IOs which require different failure * handling. This function determines the number of bytes which * can be failed from the beginning of the request without * crossing into area which need to be retried further. * * Return: * The number of bytes to fail. * * Context: * queue_lock must be held. */ unsigned int blk_rq_err_bytes(const struct request *rq) { unsigned int ff = rq->cmd_flags & REQ_FAILFAST_MASK; unsigned int bytes = 0; struct bio *bio; if (!(rq->cmd_flags & REQ_MIXED_MERGE)) return blk_rq_bytes(rq); /* * Currently the only 'mixing' which can happen is between * different fastfail types. We can safely fail portions * which have all the failfast bits that the first one has - * the ones which are at least as eager to fail as the first * one. */ for (bio = rq->bio; bio; bio = bio->bi_next) { if ((bio->bi_rw & ff) != ff) break; bytes += bio->bi_size; } /* this could lead to infinite loop */ BUG_ON(blk_rq_bytes(rq) && !bytes); return bytes; } EXPORT_SYMBOL_GPL(blk_rq_err_bytes); static void blk_account_io_completion(struct request *req, unsigned int bytes) { if (blk_do_io_stat(req)) { const int rw = rq_data_dir(req); struct hd_struct *part; int cpu; cpu = part_stat_lock(); part = req->part; part_stat_add(cpu, part, sectors[rw], bytes >> 9); part_stat_unlock(); } } static void blk_account_io_done(struct request *req) { /* * Account IO completion. flush_rq isn't accounted as a * normal IO on queueing nor completion. Accounting the * containing request is enough. */ if (blk_do_io_stat(req) && !(req->cmd_flags & REQ_FLUSH_SEQ)) { unsigned long duration = jiffies - req->start_time; const int rw = rq_data_dir(req); struct hd_struct *part; int cpu; cpu = part_stat_lock(); part = req->part; part_stat_inc(cpu, part, ios[rw]); part_stat_add(cpu, part, ticks[rw], duration); part_round_stats(cpu, part); part_dec_in_flight(part, rw); hd_struct_put(part); part_stat_unlock(); } } /** * blk_peek_request - peek at the top of a request queue * @q: request queue to peek at * * Description: * Return the request at the top of @q. The returned request * should be started using blk_start_request() before LLD starts * processing it. * * Return: * Pointer to the request at the top of @q if available. Null * otherwise. * * Context: * queue_lock must be held. */ struct request *blk_peek_request(struct request_queue *q) { struct request *rq; int ret; while ((rq = __elv_next_request(q)) != NULL) { if (!(rq->cmd_flags & REQ_STARTED)) { /* * This is the first time the device driver * sees this request (possibly after * requeueing). Notify IO scheduler. */ if (rq->cmd_flags & REQ_SORTED) elv_activate_rq(q, rq); /* * just mark as started even if we don't start * it, a request that has been delayed should * not be passed by new incoming requests */ rq->cmd_flags |= REQ_STARTED; trace_block_rq_issue(q, rq); } if (!q->boundary_rq || q->boundary_rq == rq) { q->end_sector = rq_end_sector(rq); q->boundary_rq = NULL; } if (rq->cmd_flags & REQ_DONTPREP) break; if (q->dma_drain_size && blk_rq_bytes(rq)) { /* * make sure space for the drain appears we * know we can do this because max_hw_segments * has been adjusted to be one fewer than the * device can handle */ rq->nr_phys_segments++; } if (!q->prep_rq_fn) break; ret = q->prep_rq_fn(q, rq); if (ret == BLKPREP_OK) { break; } else if (ret == BLKPREP_DEFER) { /* * the request may have been (partially) prepped. * we need to keep this request in the front to * avoid resource deadlock. REQ_STARTED will * prevent other fs requests from passing this one. */ if (q->dma_drain_size && blk_rq_bytes(rq) && !(rq->cmd_flags & REQ_DONTPREP)) { /* * remove the space for the drain we added * so that we don't add it again */ --rq->nr_phys_segments; } rq = NULL; break; } else if (ret == BLKPREP_KILL) { rq->cmd_flags |= REQ_QUIET; /* * Mark this request as started so we don't trigger * any debug logic in the end I/O path. */ blk_start_request(rq); __blk_end_request_all(rq, -EIO); } else { printk(KERN_ERR "%s: bad return=%d\n", __func__, ret); break; } } return rq; } EXPORT_SYMBOL(blk_peek_request); void blk_dequeue_request(struct request *rq) { struct request_queue *q = rq->q; BUG_ON(list_empty(&rq->queuelist)); BUG_ON(ELV_ON_HASH(rq)); list_del_init(&rq->queuelist); /* * the time frame between a request being removed from the lists * and to it is freed is accounted as io that is in progress at * the driver side. */ if (blk_account_rq(rq)) { q->in_flight[rq_is_sync(rq)]++; set_io_start_time_ns(rq); } } /** * blk_start_request - start request processing on the driver * @req: request to dequeue * * Description: * Dequeue @req and start timeout timer on it. This hands off the * request to the driver. * * Block internal functions which don't want to start timer should * call blk_dequeue_request(). * * Context: * queue_lock must be held. */ void blk_start_request(struct request *req) { blk_dequeue_request(req); /* * We are now handing the request to the hardware, initialize * resid_len to full count and add the timeout handler. */ req->resid_len = blk_rq_bytes(req); if (unlikely(blk_bidi_rq(req))) req->next_rq->resid_len = blk_rq_bytes(req->next_rq); blk_add_timer(req); } EXPORT_SYMBOL(blk_start_request); /** * blk_fetch_request - fetch a request from a request queue * @q: request queue to fetch a request from * * Description: * Return the request at the top of @q. The request is started on * return and LLD can start processing it immediately. * * Return: * Pointer to the request at the top of @q if available. Null * otherwise. * * Context: * queue_lock must be held. */ struct request *blk_fetch_request(struct request_queue *q) { struct request *rq; rq = blk_peek_request(q); if (rq) blk_start_request(rq); return rq; } EXPORT_SYMBOL(blk_fetch_request); /** * blk_update_request - Special helper function for request stacking drivers * @req: the request being processed * @error: %0 for success, < %0 for error * @nr_bytes: number of bytes to complete @req * * Description: * Ends I/O on a number of bytes attached to @req, but doesn't complete * the request structure even if @req doesn't have leftover. * If @req has leftover, sets it up for the next range of segments. * * This special helper function is only for request stacking drivers * (e.g. request-based dm) so that they can handle partial completion. * Actual device drivers should use blk_end_request instead. * * Passing the result of blk_rq_bytes() as @nr_bytes guarantees * %false return from this function. * * Return: * %false - this request doesn't have any more data * %true - this request has more data **/ bool blk_update_request(struct request *req, int error, unsigned int nr_bytes) { int total_bytes, bio_nbytes, next_idx = 0; struct bio *bio; if (!req->bio) return false; trace_block_rq_complete(req->q, req); /* * For fs requests, rq is just carrier of independent bio's * and each partial completion should be handled separately. * Reset per-request error on each partial completion. * * TODO: tj: This is too subtle. It would be better to let * low level drivers do what they see fit. */ if (req->cmd_type == REQ_TYPE_FS) req->errors = 0; if (error && req->cmd_type == REQ_TYPE_FS && !(req->cmd_flags & REQ_QUIET)) { char *error_type; switch (error) { case -ENOLINK: error_type = "recoverable transport"; break; case -EREMOTEIO: error_type = "critical target"; break; case -EBADE: error_type = "critical nexus"; break; case -EIO: default: error_type = "I/O"; break; } printk(KERN_ERR "end_request: %s error, dev %s, sector %llu\n", error_type, req->rq_disk ? req->rq_disk->disk_name : "?", (unsigned long long)blk_rq_pos(req)); } blk_account_io_completion(req, nr_bytes); total_bytes = bio_nbytes = 0; while ((bio = req->bio) != NULL) { int nbytes; if (nr_bytes >= bio->bi_size) { req->bio = bio->bi_next; nbytes = bio->bi_size; req_bio_endio(req, bio, nbytes, error); next_idx = 0; bio_nbytes = 0; } else { int idx = bio->bi_idx + next_idx; if (unlikely(idx >= bio->bi_vcnt)) { blk_dump_rq_flags(req, "__end_that"); printk(KERN_ERR "%s: bio idx %d >= vcnt %d\n", __func__, idx, bio->bi_vcnt); break; } nbytes = bio_iovec_idx(bio, idx)->bv_len; BIO_BUG_ON(nbytes > bio->bi_size); /* * not a complete bvec done */ if (unlikely(nbytes > nr_bytes)) { bio_nbytes += nr_bytes; total_bytes += nr_bytes; break; } /* * advance to the next vector */ next_idx++; bio_nbytes += nbytes; } total_bytes += nbytes; nr_bytes -= nbytes; bio = req->bio; if (bio) { /* * end more in this run, or just return 'not-done' */ if (unlikely(nr_bytes <= 0)) break; } } /* * completely done */ if (!req->bio) { /* * Reset counters so that the request stacking driver * can find how many bytes remain in the request * later. */ req->__data_len = 0; return false; } /* * if the request wasn't completed, update state */ if (bio_nbytes) { req_bio_endio(req, bio, bio_nbytes, error); bio->bi_idx += next_idx; bio_iovec(bio)->bv_offset += nr_bytes; bio_iovec(bio)->bv_len -= nr_bytes; } req->__data_len -= total_bytes; req->buffer = bio_data(req->bio); /* update sector only for requests with clear definition of sector */ if (req->cmd_type == REQ_TYPE_FS || (req->cmd_flags & REQ_DISCARD)) req->__sector += total_bytes >> 9; /* mixed attributes always follow the first bio */ if (req->cmd_flags & REQ_MIXED_MERGE) { req->cmd_flags &= ~REQ_FAILFAST_MASK; req->cmd_flags |= req->bio->bi_rw & REQ_FAILFAST_MASK; } /* * If total number of sectors is less than the first segment * size, something has gone terribly wrong. */ if (blk_rq_bytes(req) < blk_rq_cur_bytes(req)) { blk_dump_rq_flags(req, "request botched"); req->__data_len = blk_rq_cur_bytes(req); } /* recalculate the number of segments */ blk_recalc_rq_segments(req); return true; } EXPORT_SYMBOL_GPL(blk_update_request); static bool blk_update_bidi_request(struct request *rq, int error, unsigned int nr_bytes, unsigned int bidi_bytes) { if (blk_update_request(rq, error, nr_bytes)) return true; /* Bidi request must be completed as a whole */ if (unlikely(blk_bidi_rq(rq)) && blk_update_request(rq->next_rq, error, bidi_bytes)) return true; if (blk_queue_add_random(rq->q)) add_disk_randomness(rq->rq_disk); return false; } /** * blk_unprep_request - unprepare a request * @req: the request * * This function makes a request ready for complete resubmission (or * completion). It happens only after all error handling is complete, * so represents the appropriate moment to deallocate any resources * that were allocated to the request in the prep_rq_fn. The queue * lock is held when calling this. */ void blk_unprep_request(struct request *req) { struct request_queue *q = req->q; req->cmd_flags &= ~REQ_DONTPREP; if (q->unprep_rq_fn) q->unprep_rq_fn(q, req); } EXPORT_SYMBOL_GPL(blk_unprep_request); /* * queue lock must be held */ static void blk_finish_request(struct request *req, int error) { if (blk_rq_tagged(req)) blk_queue_end_tag(req->q, req); BUG_ON(blk_queued_rq(req)); if (unlikely(laptop_mode) && req->cmd_type == REQ_TYPE_FS) laptop_io_completion(&req->q->backing_dev_info); blk_delete_timer(req); if (req->cmd_flags & REQ_DONTPREP) blk_unprep_request(req); blk_account_io_done(req); if (req->end_io) req->end_io(req, error); else { if (blk_bidi_rq(req)) __blk_put_request(req->next_rq->q, req->next_rq); __blk_put_request(req->q, req); } } /** * blk_end_bidi_request - Complete a bidi request * @rq: the request to complete * @error: %0 for success, < %0 for error * @nr_bytes: number of bytes to complete @rq * @bidi_bytes: number of bytes to complete @rq->next_rq * * Description: * Ends I/O on a number of bytes attached to @rq and @rq->next_rq. * Drivers that supports bidi can safely call this member for any * type of request, bidi or uni. In the later case @bidi_bytes is * just ignored. * * Return: * %false - we are done with this request * %true - still buffers pending for this request **/ static bool blk_end_bidi_request(struct request *rq, int error, unsigned int nr_bytes, unsigned int bidi_bytes) { struct request_queue *q = rq->q; unsigned long flags; if (blk_update_bidi_request(rq, error, nr_bytes, bidi_bytes)) return true; spin_lock_irqsave(q->queue_lock, flags); blk_finish_request(rq, error); spin_unlock_irqrestore(q->queue_lock, flags); return false; } /** * __blk_end_bidi_request - Complete a bidi request with queue lock held * @rq: the request to complete * @error: %0 for success, < %0 for error * @nr_bytes: number of bytes to complete @rq * @bidi_bytes: number of bytes to complete @rq->next_rq * * Description: * Identical to blk_end_bidi_request() except that queue lock is * assumed to be locked on entry and remains so on return. * * Return: * %false - we are done with this request * %true - still buffers pending for this request **/ static bool __blk_end_bidi_request(struct request *rq, int error, unsigned int nr_bytes, unsigned int bidi_bytes) { if (blk_update_bidi_request(rq, error, nr_bytes, bidi_bytes)) return true; blk_finish_request(rq, error); return false; } /** * blk_end_request - Helper function for drivers to complete the request. * @rq: the request being processed * @error: %0 for success, < %0 for error * @nr_bytes: number of bytes to complete * * Description: * Ends I/O on a number of bytes attached to @rq. * If @rq has leftover, sets it up for the next range of segments. * * Return: * %false - we are done with this request * %true - still buffers pending for this request **/ bool blk_end_request(struct request *rq, int error, unsigned int nr_bytes) { return blk_end_bidi_request(rq, error, nr_bytes, 0); } EXPORT_SYMBOL(blk_end_request); /** * blk_end_request_all - Helper function for drives to finish the request. * @rq: the request to finish * @error: %0 for success, < %0 for error * * Description: * Completely finish @rq. */ void blk_end_request_all(struct request *rq, int error) { bool pending; unsigned int bidi_bytes = 0; if (unlikely(blk_bidi_rq(rq))) bidi_bytes = blk_rq_bytes(rq->next_rq); pending = blk_end_bidi_request(rq, error, blk_rq_bytes(rq), bidi_bytes); BUG_ON(pending); } EXPORT_SYMBOL(blk_end_request_all); /** * blk_end_request_cur - Helper function to finish the current request chunk. * @rq: the request to finish the current chunk for * @error: %0 for success, < %0 for error * * Description: * Complete the current consecutively mapped chunk from @rq. * * Return: * %false - we are done with this request * %true - still buffers pending for this request */ bool blk_end_request_cur(struct request *rq, int error) { return blk_end_request(rq, error, blk_rq_cur_bytes(rq)); } EXPORT_SYMBOL(blk_end_request_cur); /** * blk_end_request_err - Finish a request till the next failure boundary. * @rq: the request to finish till the next failure boundary for * @error: must be negative errno * * Description: * Complete @rq till the next failure boundary. * * Return: * %false - we are done with this request * %true - still buffers pending for this request */ bool blk_end_request_err(struct request *rq, int error) { WARN_ON(error >= 0); return blk_end_request(rq, error, blk_rq_err_bytes(rq)); } EXPORT_SYMBOL_GPL(blk_end_request_err); /** * __blk_end_request - Helper function for drivers to complete the request. * @rq: the request being processed * @error: %0 for success, < %0 for error * @nr_bytes: number of bytes to complete * * Description: * Must be called with queue lock held unlike blk_end_request(). * * Return: * %false - we are done with this request * %true - still buffers pending for this request **/ bool __blk_end_request(struct request *rq, int error, unsigned int nr_bytes) { return __blk_end_bidi_request(rq, error, nr_bytes, 0); } EXPORT_SYMBOL(__blk_end_request); /** * __blk_end_request_all - Helper function for drives to finish the request. * @rq: the request to finish * @error: %0 for success, < %0 for error * * Description: * Completely finish @rq. Must be called with queue lock held. */ void __blk_end_request_all(struct request *rq, int error) { bool pending; unsigned int bidi_bytes = 0; if (unlikely(blk_bidi_rq(rq))) bidi_bytes = blk_rq_bytes(rq->next_rq); pending = __blk_end_bidi_request(rq, error, blk_rq_bytes(rq), bidi_bytes); BUG_ON(pending); } EXPORT_SYMBOL(__blk_end_request_all); /** * __blk_end_request_cur - Helper function to finish the current request chunk. * @rq: the request to finish the current chunk for * @error: %0 for success, < %0 for error * * Description: * Complete the current consecutively mapped chunk from @rq. Must * be called with queue lock held. * * Return: * %false - we are done with this request * %true - still buffers pending for this request */ bool __blk_end_request_cur(struct request *rq, int error) { return __blk_end_request(rq, error, blk_rq_cur_bytes(rq)); } EXPORT_SYMBOL(__blk_end_request_cur); /** * __blk_end_request_err - Finish a request till the next failure boundary. * @rq: the request to finish till the next failure boundary for * @error: must be negative errno * * Description: * Complete @rq till the next failure boundary. Must be called * with queue lock held. * * Return: * %false - we are done with this request * %true - still buffers pending for this request */ bool __blk_end_request_err(struct request *rq, int error) { WARN_ON(error >= 0); return __blk_end_request(rq, error, blk_rq_err_bytes(rq)); } EXPORT_SYMBOL_GPL(__blk_end_request_err); void blk_rq_bio_prep(struct request_queue *q, struct request *rq, struct bio *bio) { /* Bit 0 (R/W) is identical in rq->cmd_flags and bio->bi_rw */ rq->cmd_flags |= bio->bi_rw & REQ_WRITE; if (bio_has_data(bio)) { rq->nr_phys_segments = bio_phys_segments(q, bio); rq->buffer = bio_data(bio); } rq->__data_len = bio->bi_size; rq->bio = rq->biotail = bio; if (bio->bi_bdev) rq->rq_disk = bio->bi_bdev->bd_disk; } #if ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE /** * rq_flush_dcache_pages - Helper function to flush all pages in a request * @rq: the request to be flushed * * Description: * Flush all pages in @rq. */ void rq_flush_dcache_pages(struct request *rq) { struct req_iterator iter; struct bio_vec *bvec; rq_for_each_segment(bvec, rq, iter) flush_dcache_page(bvec->bv_page); } EXPORT_SYMBOL_GPL(rq_flush_dcache_pages); #endif /** * blk_lld_busy - Check if underlying low-level drivers of a device are busy * @q : the queue of the device being checked * * Description: * Check if underlying low-level drivers of a device are busy. * If the drivers want to export their busy state, they must set own * exporting function using blk_queue_lld_busy() first. * * Basically, this function is used only by request stacking drivers * to stop dispatching requests to underlying devices when underlying * devices are busy. This behavior helps more I/O merging on the queue * of the request stacking driver and prevents I/O throughput regression * on burst I/O load. * * Return: * 0 - Not busy (The request stacking driver should dispatch request) * 1 - Busy (The request stacking driver should stop dispatching request) */ int blk_lld_busy(struct request_queue *q) { if (q->lld_busy_fn) return q->lld_busy_fn(q); return 0; } EXPORT_SYMBOL_GPL(blk_lld_busy); /** * blk_rq_unprep_clone - Helper function to free all bios in a cloned request * @rq: the clone request to be cleaned up * * Description: * Free all bios in @rq for a cloned request. */ void blk_rq_unprep_clone(struct request *rq) { struct bio *bio; while ((bio = rq->bio) != NULL) { rq->bio = bio->bi_next; bio_put(bio); } } EXPORT_SYMBOL_GPL(blk_rq_unprep_clone); /* * Copy attributes of the original request to the clone request. * The actual data parts (e.g. ->cmd, ->buffer, ->sense) are not copied. */ static void __blk_rq_prep_clone(struct request *dst, struct request *src) { dst->cpu = src->cpu; dst->cmd_flags = (src->cmd_flags & REQ_CLONE_MASK) | REQ_NOMERGE; dst->cmd_type = src->cmd_type; dst->__sector = blk_rq_pos(src); dst->__data_len = blk_rq_bytes(src); dst->nr_phys_segments = src->nr_phys_segments; dst->ioprio = src->ioprio; dst->extra_len = src->extra_len; } /** * blk_rq_prep_clone - Helper function to setup clone request * @rq: the request to be setup * @rq_src: original request to be cloned * @bs: bio_set that bios for clone are allocated from * @gfp_mask: memory allocation mask for bio * @bio_ctr: setup function to be called for each clone bio. * Returns %0 for success, non %0 for failure. * @data: private data to be passed to @bio_ctr * * Description: * Clones bios in @rq_src to @rq, and copies attributes of @rq_src to @rq. * The actual data parts of @rq_src (e.g. ->cmd, ->buffer, ->sense) * are not copied, and copying such parts is the caller's responsibility. * Also, pages which the original bios are pointing to are not copied * and the cloned bios just point same pages. * So cloned bios must be completed before original bios, which means * the caller must complete @rq before @rq_src. */ int blk_rq_prep_clone(struct request *rq, struct request *rq_src, struct bio_set *bs, gfp_t gfp_mask, int (*bio_ctr)(struct bio *, struct bio *, void *), void *data) { struct bio *bio, *bio_src; if (!bs) bs = fs_bio_set; blk_rq_init(NULL, rq); __rq_for_each_bio(bio_src, rq_src) { bio = bio_alloc_bioset(gfp_mask, bio_src->bi_max_vecs, bs); if (!bio) goto free_and_out; __bio_clone(bio, bio_src); if (bio_integrity(bio_src) && bio_integrity_clone(bio, bio_src, gfp_mask, bs)) goto free_and_out; if (bio_ctr && bio_ctr(bio, bio_src, data)) goto free_and_out; if (rq->bio) { rq->biotail->bi_next = bio; rq->biotail = bio; } else rq->bio = rq->biotail = bio; } __blk_rq_prep_clone(rq, rq_src); return 0; free_and_out: if (bio) bio_free(bio, bs); blk_rq_unprep_clone(rq); return -ENOMEM; } EXPORT_SYMBOL_GPL(blk_rq_prep_clone); int kblockd_schedule_work(struct request_queue *q, struct work_struct *work) { return queue_work(kblockd_workqueue, work); } EXPORT_SYMBOL(kblockd_schedule_work); int kblockd_schedule_delayed_work(struct request_queue *q, struct delayed_work *dwork, unsigned long delay) { return queue_delayed_work(kblockd_workqueue, dwork, delay); } EXPORT_SYMBOL(kblockd_schedule_delayed_work); #define PLUG_MAGIC 0x91827364 void blk_start_plug(struct blk_plug *plug) { struct task_struct *tsk = current; plug->magic = PLUG_MAGIC; INIT_LIST_HEAD(&plug->list); INIT_LIST_HEAD(&plug->cb_list); plug->should_sort = 0; /* * If this is a nested plug, don't actually assign it. It will be * flushed on its own. */ if (!tsk->plug) { /* * Store ordering should not be needed here, since a potential * preempt will imply a full memory barrier */ tsk->plug = plug; } } EXPORT_SYMBOL(blk_start_plug); static int plug_rq_cmp(void *priv, struct list_head *a, struct list_head *b) { struct request *rqa = container_of(a, struct request, queuelist); struct request *rqb = container_of(b, struct request, queuelist); return !(rqa->q <= rqb->q); } /* * If 'from_schedule' is true, then postpone the dispatch of requests * until a safe kblockd context. We due this to avoid accidental big * additional stack usage in driver dispatch, in places where the originally * plugger did not intend it. */ static void queue_unplugged(struct request_queue *q, unsigned int depth, bool from_schedule) __releases(q->queue_lock) { trace_block_unplug(q, depth, !from_schedule); /* * If we are punting this to kblockd, then we can safely drop * the queue_lock before waking kblockd (which needs to take * this lock). */ if (from_schedule) { spin_unlock(q->queue_lock); blk_run_queue_async(q); } else { __blk_run_queue(q); spin_unlock(q->queue_lock); } } static void flush_plug_callbacks(struct blk_plug *plug) { LIST_HEAD(callbacks); if (list_empty(&plug->cb_list)) return; list_splice_init(&plug->cb_list, &callbacks); while (!list_empty(&callbacks)) { struct blk_plug_cb *cb = list_first_entry(&callbacks, struct blk_plug_cb, list); list_del(&cb->list); cb->callback(cb); } } void blk_flush_plug_list(struct blk_plug *plug, bool from_schedule) { struct request_queue *q; unsigned long flags; struct request *rq; LIST_HEAD(list); unsigned int depth; BUG_ON(plug->magic != PLUG_MAGIC); flush_plug_callbacks(plug); if (list_empty(&plug->list)) return; list_splice_init(&plug->list, &list); if (plug->should_sort) { list_sort(NULL, &list, plug_rq_cmp); plug->should_sort = 0; } q = NULL; depth = 0; /* * Save and disable interrupts here, to avoid doing it for every * queue lock we have to take. */ local_irq_save(flags); while (!list_empty(&list)) { rq = list_entry_rq(list.next); list_del_init(&rq->queuelist); BUG_ON(!(rq->cmd_flags & REQ_ON_PLUG)); BUG_ON(!rq->q); if (rq->q != q) { /* * This drops the queue lock */ if (q) queue_unplugged(q, depth, from_schedule); q = rq->q; depth = 0; spin_lock(q->queue_lock); } rq->cmd_flags &= ~REQ_ON_PLUG; /* * rq is already accounted, so use raw insert */ if (rq->cmd_flags & (REQ_FLUSH | REQ_FUA)) __elv_add_request(q, rq, ELEVATOR_INSERT_FLUSH); else __elv_add_request(q, rq, ELEVATOR_INSERT_SORT_MERGE); depth++; } /* * This drops the queue lock */ if (q) queue_unplugged(q, depth, from_schedule); local_irq_restore(flags); } void blk_finish_plug(struct blk_plug *plug) { blk_flush_plug_list(plug, false); if (plug == current->plug) current->plug = NULL; } EXPORT_SYMBOL(blk_finish_plug); int __init blk_dev_init(void) { BUILD_BUG_ON(__REQ_NR_BITS > 8 * sizeof(((struct request *)0)->cmd_flags)); /* used for unplugging and affects IO latency/throughput - HIGHPRI */ kblockd_workqueue = alloc_workqueue("kblockd", WQ_MEM_RECLAIM | WQ_HIGHPRI, 0); if (!kblockd_workqueue) panic("Failed to create kblockd\n"); request_cachep = kmem_cache_create("blkdev_requests", sizeof(struct request), 0, SLAB_PANIC, NULL); blk_requestq_cachep = kmem_cache_create("blkdev_queue", sizeof(struct request_queue), 0, SLAB_PANIC, NULL); return 0; }