diff options
Diffstat (limited to 'block/blk-core.c')
| -rw-r--r-- | block/blk-core.c | 2158 |
1 files changed, 2158 insertions, 0 deletions
diff --git a/block/blk-core.c b/block/blk-core.c new file mode 100644 index 0000000..c36aa98 --- /dev/null +++ b/block/blk-core.c @@ -0,0 +1,2158 @@ +/* + * Copyright (C) 1991, 1992 Linus Torvalds + * Copyright (C) 1994, Karl Keyte: Added support for disk statistics + * Elevator latency, (C) 2000 Andrea Arcangeli <andrea@suse.de> SuSE + * Queue request tables / lock, selectable elevator, Jens Axboe <axboe@suse.de> + * kernel-doc documentation started by NeilBrown <neilb@cse.unsw.edu.au> + * - July2000 + * bio rewrite, highmem i/o, etc, Jens Axboe <axboe@suse.de> - may 2001 + */ + +/* + * This handles all read/write requests to block devices + */ +#include <linux/kernel.h> +#include <linux/module.h> +#include <linux/backing-dev.h> +#include <linux/bio.h> +#include <linux/blkdev.h> +#include <linux/highmem.h> +#include <linux/mm.h> +#include <linux/kernel_stat.h> +#include <linux/string.h> +#include <linux/init.h> +#include <linux/completion.h> +#include <linux/slab.h> +#include <linux/swap.h> +#include <linux/writeback.h> +#include <linux/task_io_accounting_ops.h> +#include <linux/blktrace_api.h> +#include <linux/fault-inject.h> + +#include "blk.h" + +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_fs_request(rq) || !rq->rq_disk) + return; + + cpu = part_stat_lock(); + part = disk_map_sector_rcu(rq->rq_disk, rq->sector); + + if (!new_io) + part_stat_inc(cpu, part, merges[rw]); + else { + part_round_stats(cpu, part); + part_inc_in_flight(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 = rq->hard_sector = (sector_t) -1; + INIT_HLIST_NODE(&rq->hash); + RB_CLEAR_NODE(&rq->rb_node); + rq->cmd = rq->__cmd; + rq->tag = -1; + rq->ref_count = 1; +} +EXPORT_SYMBOL(blk_rq_init); + +static void req_bio_endio(struct request *rq, struct bio *bio, + unsigned int nbytes, int error) +{ + struct request_queue *q = rq->q; + + if (&q->bar_rq != rq) { + 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; + } + + bio->bi_size -= nbytes; + bio->bi_sector += (nbytes >> 9); + + if (bio_integrity(bio)) + bio_integrity_advance(bio, nbytes); + + if (bio->bi_size == 0) + bio_endio(bio, error); + } else { + + /* + * Okay, this is the barrier request in progress, just + * record the error; + */ + if (error && !q->orderr) + q->orderr = 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 %lu/%u\n", + (unsigned long long)rq->sector, + rq->nr_sectors, + rq->current_nr_sectors); + printk(KERN_INFO " bio %p, biotail %p, buffer %p, data %p, len %u\n", + rq->bio, rq->biotail, + rq->buffer, rq->data, + rq->data_len); + + if (blk_pc_request(rq)) { + 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); + +/* + * "plug" the device if there are no outstanding requests: this will + * force the transfer to start only after we have put all the requests + * on the list. + * + * This is called with interrupts off and no requests on the queue and + * with the queue lock held. + */ +void blk_plug_device(struct request_queue *q) +{ + WARN_ON(!irqs_disabled()); + + /* + * don't plug a stopped queue, it must be paired with blk_start_queue() + * which will restart the queueing + */ + if (blk_queue_stopped(q)) + return; + + if (!queue_flag_test_and_set(QUEUE_FLAG_PLUGGED, q)) { + mod_timer(&q->unplug_timer, jiffies + q->unplug_delay); + blk_add_trace_generic(q, NULL, 0, BLK_TA_PLUG); + } +} +EXPORT_SYMBOL(blk_plug_device); + +/** + * blk_plug_device_unlocked - plug a device without queue lock held + * @q: The &struct request_queue to plug + * + * Description: + * Like @blk_plug_device(), but grabs the queue lock and disables + * interrupts. + **/ +void blk_plug_device_unlocked(struct request_queue *q) +{ + unsigned long flags; + + spin_lock_irqsave(q->queue_lock, flags); + blk_plug_device(q); + spin_unlock_irqrestore(q->queue_lock, flags); +} +EXPORT_SYMBOL(blk_plug_device_unlocked); + +/* + * remove the queue from the plugged list, if present. called with + * queue lock held and interrupts disabled. + */ +int blk_remove_plug(struct request_queue *q) +{ + WARN_ON(!irqs_disabled()); + + if (!queue_flag_test_and_clear(QUEUE_FLAG_PLUGGED, q)) + return 0; + + del_timer(&q->unplug_timer); + return 1; +} +EXPORT_SYMBOL(blk_remove_plug); + +/* + * remove the plug and let it rip.. + */ +void __generic_unplug_device(struct request_queue *q) +{ + if (unlikely(blk_queue_stopped(q))) + return; + + if (!blk_remove_plug(q)) + return; + + q->request_fn(q); +} + +/** + * generic_unplug_device - fire a request queue + * @q: The &struct request_queue in question + * + * Description: + * Linux uses plugging to build bigger requests queues before letting + * the device have at them. If a queue is plugged, the I/O scheduler + * is still adding and merging requests on the queue. Once the queue + * gets unplugged, the request_fn defined for the queue is invoked and + * transfers started. + **/ +void generic_unplug_device(struct request_queue *q) +{ + if (blk_queue_plugged(q)) { + spin_lock_irq(q->queue_lock); + __generic_unplug_device(q); + spin_unlock_irq(q->queue_lock); + } +} +EXPORT_SYMBOL(generic_unplug_device); + +static void blk_backing_dev_unplug(struct backing_dev_info *bdi, + struct page *page) +{ + struct request_queue *q = bdi->unplug_io_data; + + blk_unplug(q); +} + +void blk_unplug_work(struct work_struct *work) +{ + struct request_queue *q = + container_of(work, struct request_queue, unplug_work); + + blk_add_trace_pdu_int(q, BLK_TA_UNPLUG_IO, NULL, + q->rq.count[READ] + q->rq.count[WRITE]); + + q->unplug_fn(q); +} + +void blk_unplug_timeout(unsigned long data) +{ + struct request_queue *q = (struct request_queue *)data; + + blk_add_trace_pdu_int(q, BLK_TA_UNPLUG_TIMER, NULL, + q->rq.count[READ] + q->rq.count[WRITE]); + + kblockd_schedule_work(q, &q->unplug_work); +} + +void blk_unplug(struct request_queue *q) +{ + /* + * devices don't necessarily have an ->unplug_fn defined + */ + if (q->unplug_fn) { + blk_add_trace_pdu_int(q, BLK_TA_UNPLUG_IO, NULL, + q->rq.count[READ] + q->rq.count[WRITE]); + + q->unplug_fn(q); + } +} +EXPORT_SYMBOL(blk_unplug); + +static void blk_invoke_request_fn(struct request_queue *q) +{ + if (unlikely(blk_queue_stopped(q))) + return; + + /* + * one level of recursion is ok and is much faster than kicking + * the unplug handling + */ + if (!queue_flag_test_and_set(QUEUE_FLAG_REENTER, q)) { + q->request_fn(q); + queue_flag_clear(QUEUE_FLAG_REENTER, q); + } else { + queue_flag_set(QUEUE_FLAG_PLUGGED, q); + kblockd_schedule_work(q, &q->unplug_work); + } +} + +/** + * 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_invoke_request_fn(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) +{ + blk_remove_plug(q); + 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. + * + */ +void blk_sync_queue(struct request_queue *q) +{ + del_timer_sync(&q->unplug_timer); + kblockd_flush_work(&q->unplug_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) +{ + blk_remove_plug(q); + + /* + * Only recurse once to avoid overrunning the stack, let the unplug + * handling reinvoke the handler shortly if we already got there. + */ + if (!elv_queue_empty(q)) + blk_invoke_request_fn(q); +} +EXPORT_SYMBOL(__blk_run_queue); + +/** + * 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. Also + * See @blk_start_queueing. + * + */ +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); +} + +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); + + 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_put_queue(q); +} +EXPORT_SYMBOL(blk_cleanup_queue); + +static int blk_init_free_list(struct request_queue *q) +{ + struct request_list *rl = &q->rq; + + rl->count[READ] = rl->count[WRITE] = 0; + rl->starved[READ] = rl->starved[WRITE] = 0; + rl->elvpriv = 0; + init_waitqueue_head(&rl->wait[READ]); + init_waitqueue_head(&rl->wait[WRITE]); + + 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.unplug_io_fn = blk_backing_dev_unplug; + q->backing_dev_info.unplug_io_data = q; + err = bdi_init(&q->backing_dev_info); + if (err) { + kmem_cache_free(blk_requestq_cachep, q); + return NULL; + } + + init_timer(&q->unplug_timer); + setup_timer(&q->timeout, blk_rq_timed_out_timer, (unsigned long) q); + INIT_LIST_HEAD(&q->timeout_list); + INIT_WORK(&q->unplug_work, blk_unplug_work); + + kobject_init(&q->kobj, &blk_queue_ktype); + + mutex_init(&q->sysfs_lock); + spin_lock_init(&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 *q = blk_alloc_queue_node(GFP_KERNEL, node_id); + + if (!q) + return NULL; + + q->node = node_id; + if (blk_init_free_list(q)) { + kmem_cache_free(blk_requestq_cachep, q); + return NULL; + } + + /* + * if caller didn't supply a lock, they get per-queue locking with + * our embedded lock + */ + if (!lock) + lock = &q->__queue_lock; + + q->request_fn = rfn; + q->prep_rq_fn = NULL; + q->unplug_fn = generic_unplug_device; + q->queue_flags = (1 << QUEUE_FLAG_CLUSTER | + 1 << QUEUE_FLAG_STACKABLE); + q->queue_lock = lock; + + blk_queue_segment_boundary(q, BLK_SEG_BOUNDARY_MASK); + + blk_queue_make_request(q, __make_request); + blk_queue_max_segment_size(q, MAX_SEGMENT_SIZE); + + blk_queue_max_hw_segments(q, MAX_HW_SEGMENTS); + blk_queue_max_phys_segments(q, MAX_PHYS_SEGMENTS); + + q->sg_reserved_size = INT_MAX; + + blk_set_cmd_filter_defaults(&q->cmd_filter); + + /* + * all done + */ + if (!elevator_init(q, NULL)) { + blk_queue_congestion_threshold(q); + return q; + } + + blk_put_queue(q); + return NULL; +} +EXPORT_SYMBOL(blk_init_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; +} + +static inline void blk_free_request(struct request_queue *q, struct request *rq) +{ + 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 rw, 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 = rw | 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 rw) +{ + struct request_list *rl = &q->rq; + + if (rl->count[rw] < queue_congestion_off_threshold(q)) + blk_clear_queue_congested(q, rw); + + if (rl->count[rw] + 1 <= q->nr_requests) { + if (waitqueue_active(&rl->wait[rw])) + wake_up(&rl->wait[rw]); + + blk_clear_queue_full(q, rw); + } +} + +/* + * 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 rw, int priv) +{ + struct request_list *rl = &q->rq; + + rl->count[rw]--; + if (priv) + rl->elvpriv--; + + __freed_request(q, rw); + + if (unlikely(rl->starved[rw ^ 1])) + __freed_request(q, rw ^ 1); +} + +#define blkdev_free_rq(list) list_entry((list)->next, struct request, queuelist) +/* + * 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 int rw = rw_flags & 0x01; + int may_queue, priv; + + may_queue = elv_may_queue(q, rw_flags); + if (may_queue == ELV_MQUEUE_NO) + goto rq_starved; + + if (rl->count[rw]+1 >= queue_congestion_on_threshold(q)) { + if (rl->count[rw]+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, rw)) { + ioc_set_batching(q, ioc); + blk_set_queue_full(q, rw); + } 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, rw); + } + + /* + * 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[rw] >= (3 * q->nr_requests / 2)) + goto out; + + rl->count[rw]++; + rl->starved[rw] = 0; + + priv = !test_bit(QUEUE_FLAG_ELVSWITCH, &q->queue_flags); + if (priv) + rl->elvpriv++; + + 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, rw, 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[rw] == 0)) + rl->starved[rw] = 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--; + + blk_add_trace_generic(q, bio, rw, BLK_TA_GETRQ); +out: + return rq; +} + +/* + * No available requests for this queue, unplug the device and 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 int rw = rw_flags & 0x01; + 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[rw], &wait, + TASK_UNINTERRUPTIBLE); + + blk_add_trace_generic(q, bio, rw, BLK_TA_SLEEPRQ); + + __generic_unplug_device(q); + 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[rw], &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; + + 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_start_queueing - initiate dispatch of requests to device + * @q: request queue to kick into gear + * + * This is basically a helper to remove the need to know whether a queue + * is plugged or not if someone just wants to initiate dispatch of requests + * for this queue. Should be used to start queueing on a device outside + * of ->request_fn() context. Also see @blk_run_queue. + * + * The queue lock must be held with interrupts disabled. + */ +void blk_start_queueing(struct request_queue *q) +{ + if (!blk_queue_plugged(q)) { + if (unlikely(blk_queue_stopped(q))) + return; + q->request_fn(q); + } else + __generic_unplug_device(q); +} +EXPORT_SYMBOL(blk_start_queueing); + +/** + * 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); + blk_add_trace_rq(q, rq, BLK_TA_REQUEUE); + + if (blk_rq_tagged(rq)) + blk_queue_end_tag(q, rq); + + elv_requeue_request(q, rq); +} +EXPORT_SYMBOL(blk_requeue_request); + +/** + * 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->cmd_flags |= REQ_SOFTBARRIER; + + 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); + + drive_stat_acct(rq, 1); + __elv_add_request(q, rq, where, 0); + blk_start_queueing(q); + spin_unlock_irqrestore(q->queue_lock, flags); +} +EXPORT_SYMBOL(blk_insert_request); + +/* + * add-request adds a request to the linked list. + * queue lock is held and interrupts disabled, as we muck with the + * request queue list. + */ +static inline void add_request(struct request_queue *q, struct request *req) +{ + drive_stat_acct(req, 1); + + /* + * elevator indicated where it wants this request to be + * inserted at elevator_merge time + */ + __elv_add_request(q, req, ELEVATOR_INSERT_SORT, 0); +} + +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_stat_add(cpu, part, time_in_queue, + part->in_flight * (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); + + /* + * 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 rw = rq_data_dir(req); + 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, rw, priv); + } +} +EXPORT_SYMBOL_GPL(__blk_put_request); + +void blk_put_request(struct request *req) +{ + unsigned long flags; + struct request_queue *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); + +void init_request_from_bio(struct request *req, struct bio *bio) +{ + req->cpu = bio->bi_comp_cpu; + req->cmd_type = REQ_TYPE_FS; + + /* + * inherit FAILFAST from bio (for read-ahead, and explicit FAILFAST) + */ + if (bio_rw_ahead(bio)) + req->cmd_flags |= (REQ_FAILFAST_DEV | REQ_FAILFAST_TRANSPORT | + REQ_FAILFAST_DRIVER); + if (bio_failfast_dev(bio)) + req->cmd_flags |= REQ_FAILFAST_DEV; + if (bio_failfast_transport(bio)) + req->cmd_flags |= REQ_FAILFAST_TRANSPORT; + if (bio_failfast_driver(bio)) + req->cmd_flags |= REQ_FAILFAST_DRIVER; + + /* + * REQ_BARRIER implies no merging, but lets make it explicit + */ + if (unlikely(bio_discard(bio))) { + req->cmd_flags |= REQ_DISCARD; + if (bio_barrier(bio)) + req->cmd_flags |= REQ_SOFTBARRIER; + req->q->prepare_discard_fn(req->q, req); + } else if (unlikely(bio_barrier(bio))) + req->cmd_flags |= (REQ_HARDBARRIER | REQ_NOMERGE); + + if (bio_sync(bio)) + req->cmd_flags |= REQ_RW_SYNC; + if (bio_rw_meta(bio)) + req->cmd_flags |= REQ_RW_META; + + req->errors = 0; + req->hard_sector = req->sector = bio->bi_sector; + req->ioprio = bio_prio(bio); + req->start_time = jiffies; + blk_rq_bio_prep(req->q, req, bio); +} + +static int __make_request(struct request_queue *q, struct bio *bio) +{ + struct request *req; + int el_ret, nr_sectors, barrier, discard, err; + const unsigned short prio = bio_prio(bio); + const int sync = bio_sync(bio); + int rw_flags; + + nr_sectors = bio_sectors(bio); + + /* + * 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); + + barrier = bio_barrier(bio); + if (unlikely(barrier) && bio_has_data(bio) && + (q->next_ordered == QUEUE_ORDERED_NONE)) { + err = -EOPNOTSUPP; + goto end_io; + } + + discard = bio_discard(bio); + if (unlikely(discard) && !q->prepare_discard_fn) { + err = -EOPNOTSUPP; + goto end_io; + } + + spin_lock_irq(q->queue_lock); + + if (unlikely(barrier) || elv_queue_empty(q)) + goto get_rq; + + el_ret = elv_merge(q, &req, bio); + switch (el_ret) { + case ELEVATOR_BACK_MERGE: + BUG_ON(!rq_mergeable(req)); + + if (!ll_back_merge_fn(q, req, bio)) + break; + + blk_add_trace_bio(q, bio, BLK_TA_BACKMERGE); + + req->biotail->bi_next = bio; + req->biotail = bio; + req->nr_sectors = req->hard_nr_sectors += nr_sectors; + req->ioprio = ioprio_best(req->ioprio, prio); + if (!blk_rq_cpu_valid(req)) + req->cpu = bio->bi_comp_cpu; + drive_stat_acct(req, 0); + if (!attempt_back_merge(q, req)) + elv_merged_request(q, req, el_ret); + goto out; + + case ELEVATOR_FRONT_MERGE: + BUG_ON(!rq_mergeable(req)); + + if (!ll_front_merge_fn(q, req, bio)) + break; + + blk_add_trace_bio(q, bio, BLK_TA_FRONTMERGE); + + 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->current_nr_sectors = bio_cur_sectors(bio); + req->hard_cur_sectors = req->current_nr_sectors; + req->sector = req->hard_sector = bio->bi_sector; + req->nr_sectors = req->hard_nr_sectors += nr_sectors; + req->ioprio = ioprio_best(req->ioprio, prio); + if (!blk_rq_cpu_valid(req)) + req->cpu = bio->bi_comp_cpu; + drive_stat_acct(req, 0); + if (!attempt_front_merge(q, req)) + elv_merged_request(q, req, el_ret); + goto out; + + /* ELV_NO_MERGE: elevator says don't/can't merge. */ + default: + ; + } + +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_RW_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); + + spin_lock_irq(q->queue_lock); + if (test_bit(QUEUE_FLAG_SAME_COMP, &q->queue_flags) || + bio_flagged(bio, BIO_CPU_AFFINE)) + req->cpu = blk_cpu_to_group(smp_processor_id()); + if (elv_queue_empty(q)) + blk_plug_device(q); + add_request(q, req); +out: + if (sync) + __generic_unplug_device(q); + spin_unlock_irq(q->queue_lock); + return 0; + +end_io: + bio_endio(bio, err); + 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; + + blk_add_trace_remap(bdev_get_queue(bio->bi_bdev), bio, + bdev->bd_dev, bio->bi_sector, + 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)(bio->bi_bdev->bd_inode->i_size >> 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 = bio->bi_bdev->bd_inode->i_size >> 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 (!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); +end_io: + bio_endio(bio, err); + break; + } + + if (unlikely(nr_sectors > q->max_hw_sectors)) { + printk(KERN_ERR "bio too big device %s (%u > %u)\n", + bdevname(bio->bi_bdev, b), + bio_sectors(bio), + q->max_hw_sectors); + 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) + blk_add_trace_remap(q, bio, old_dev, bio->bi_sector, + old_sector); + + blk_add_trace_bio(q, bio, BLK_TA_QUEUE); + + old_sector = bio->bi_sector; + old_dev = bio->bi_bdev->bd_dev; + + if (bio_check_eod(bio, nr_sectors)) + goto end_io; + if ((bio_empty_barrier(bio) && !q->prepare_flush_fn) || + (bio_discard(bio) && !q->prepare_discard_fn)) { + err = -EOPNOTSUPP; + goto end_io; + } + + ret = q->make_request_fn(q, bio); + } while (ret); +} + +/* + * 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,tail} to keep a list of requests + * submited by a make_request_fn function. + * current->bio_tail 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) +{ + if (current->bio_tail) { + /* make_request is active */ + *(current->bio_tail) = bio; + bio->bi_next = NULL; + current->bio_tail = &bio->bi_next; + 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 the next (which is NULL) and bio_tail + * to &bio_list, 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 fixup bio_list and + * bio_tail or bi_next, 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); + do { + current->bio_list = bio->bi_next; + if (bio->bi_next == NULL) + current->bio_tail = ¤t->bio_list; + else + bio->bi_next = NULL; + __generic_make_request(bio); + bio = current->bio_list; + } while (bio); + current->bio_tail = 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)) { + 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\n", + current->comm, task_pid_nr(current), + (rw & WRITE) ? "WRITE" : "READ", + (unsigned long long)bio->bi_sector, + bdevname(bio->bi_bdev, b)); + } + } + + 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 fuction. + * 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->nr_sectors > q->max_sectors || + rq->data_len > q->max_hw_sectors << 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 > q->max_phys_segments || + rq->nr_phys_segments > q->max_hw_segments) { + 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)); + + drive_stat_acct(rq, 1); + __elv_add_request(q, rq, ELEVATOR_INSERT_BACK, 0); + + spin_unlock_irqrestore(q->queue_lock, flags); + + return 0; +} +EXPORT_SYMBOL_GPL(blk_insert_cloned_request); + +/** + * blkdev_dequeue_request - dequeue request and start timeout timer + * @req: request to dequeue + * + * 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 elv_dequeue_request(). + */ +void blkdev_dequeue_request(struct request *req) +{ + elv_dequeue_request(req->q, req); + + /* + * We are now handing the request to the hardware, add the + * timeout handler. + */ + blk_add_timer(req); +} +EXPORT_SYMBOL(blkdev_dequeue_request); + +/** + * __end_that_request_first - end I/O on a request + * @req: 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 @req, and sets it up + * for the next range of segments (if any) in the cluster. + * + * Return: + * %0 - we are done with this request, call end_that_request_last() + * %1 - still buffers pending for this request + **/ +static int __end_that_request_first(struct request *req, int error, + int nr_bytes) +{ + int total_bytes, bio_nbytes, next_idx = 0; + struct bio *bio; + + blk_add_trace_rq(req->q, req, BLK_TA_COMPLETE); + + /* + * for a REQ_TYPE_BLOCK_PC request, we want to carry any eventual + * sense key with us all the way through + */ + if (!blk_pc_request(req)) + req->errors = 0; + + if (error && (blk_fs_request(req) && !(req->cmd_flags & REQ_QUIET))) { + printk(KERN_ERR "end_request: I/O error, dev %s, sector %llu\n", + req->rq_disk ? req->rq_disk->disk_name : "?", + (unsigned long long)req->sector); + } + + if (blk_fs_request(req) && req->rq_disk) { + const int rw = rq_data_dir(req); + struct hd_struct *part; + int cpu; + + cpu = part_stat_lock(); + part = disk_map_sector_rcu(req->rq_disk, req->sector); + part_stat_add(cpu, part, sectors[rw], nr_bytes >> 9); + part_stat_unlock(); + } + + total_bytes = bio_nbytes = 0; + while ((bio = req->bio) != NULL) { + int nbytes; + + /* + * For an empty barrier request, the low level driver must + * store a potential error location in ->sector. We pass + * that back up in ->bi_sector. + */ + if (blk_empty_barrier(req)) + bio->bi_sector = req->sector; + + 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(bio->bi_idx >= bio->bi_vcnt)) { + blk_dump_rq_flags(req, "__end_that"); + printk(KERN_ERR "%s: bio idx %d >= vcnt %d\n", + __func__, bio->bi_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) + return 0; + + /* + * 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; + } + + blk_recalc_rq_sectors(req, total_bytes >> 9); + blk_recalc_rq_segments(req); + return 1; +} + +/* + * queue lock must be held + */ +static void end_that_request_last(struct request *req, int error) +{ + struct gendisk *disk = req->rq_disk; + + if (blk_rq_tagged(req)) + blk_queue_end_tag(req->q, req); + + if (blk_queued_rq(req)) + elv_dequeue_request(req->q, req); + + if (unlikely(laptop_mode) && blk_fs_request(req)) + laptop_io_completion(); + + blk_delete_timer(req); + + /* + * Account IO completion. bar_rq isn't accounted as a normal + * IO on queueing nor completion. Accounting the containing + * request is enough. + */ + if (disk && blk_fs_request(req) && req != &req->q->bar_rq) { + 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 = disk_map_sector_rcu(disk, req->sector); + + 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); + + part_stat_unlock(); + } + + 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_rq_bytes - Returns bytes left to complete in the entire request + * @rq: the request being processed + **/ +unsigned int blk_rq_bytes(struct request *rq) +{ + if (blk_fs_request(rq)) + return rq->hard_nr_sectors << 9; + + return rq->data_len; +} +EXPORT_SYMBOL_GPL(blk_rq_bytes); + +/** + * blk_rq_cur_bytes - Returns bytes left to complete in the current segment + * @rq: the request being processed + **/ +unsigned int blk_rq_cur_bytes(struct request *rq) +{ + if (blk_fs_request(rq)) + return rq->current_nr_sectors << 9; + + if (rq->bio) + return rq->bio->bi_size; + + return rq->data_len; +} +EXPORT_SYMBOL_GPL(blk_rq_cur_bytes); + +/** + * end_request - end I/O on the current segment of the request + * @req: the request being processed + * @uptodate: error value or %0/%1 uptodate flag + * + * Description: + * Ends I/O on the current segment of a request. If that is the only + * remaining segment, the request is also completed and freed. + * + * This is a remnant of how older block drivers handled I/O completions. + * Modern drivers typically end I/O on the full request in one go, unless + * they have a residual value to account for. For that case this function + * isn't really useful, unless the residual just happens to be the + * full current segment. In other words, don't use this function in new + * code. Use blk_end_request() or __blk_end_request() to end a request. + **/ +void end_request(struct request *req, int uptodate) +{ + int error = 0; + + if (uptodate <= 0) + error = uptodate ? uptodate : -EIO; + + __blk_end_request(req, error, req->hard_cur_sectors << 9); +} +EXPORT_SYMBOL(end_request); + +static int end_that_request_data(struct request *rq, int error, + unsigned int nr_bytes, unsigned int bidi_bytes) +{ + if (rq->bio) { + if (__end_that_request_first(rq, error, nr_bytes)) + return 1; + + /* Bidi request must be completed as a whole */ + if (blk_bidi_rq(rq) && + __end_that_request_first(rq->next_rq, error, bidi_bytes)) + return 1; + } + + return 0; +} + +/** + * blk_end_io - Generic end_io function to complete a request. + * @rq: the request being processed + * @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 + * @drv_callback: function called between completion of bios in the request + * and completion of the request. + * If the callback returns non %0, this helper returns without + * completion of the request. + * + * Description: + * Ends I/O on a number of bytes attached to @rq and @rq->next_rq. + * If @rq has leftover, sets it up for the next range of segments. + * + * Return: + * %0 - we are done with this request + * %1 - this request is not freed yet, it still has pending buffers. + **/ +static int blk_end_io(struct request *rq, int error, unsigned int nr_bytes, + unsigned int bidi_bytes, + int (drv_callback)(struct request *)) +{ + struct request_queue *q = rq->q; + unsigned long flags = 0UL; + + if (end_that_request_data(rq, error, nr_bytes, bidi_bytes)) + return 1; + + /* Special feature for tricky drivers */ + if (drv_callback && drv_callback(rq)) + return 1; + + add_disk_randomness(rq->rq_disk); + + spin_lock_irqsave(q->queue_lock, flags); + end_that_request_last(rq, error); + spin_unlock_irqrestore(q->queue_lock, flags); + + return 0; +} + +/** + * 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: + * %0 - we are done with this request + * %1 - still buffers pending for this request + **/ +int blk_end_request(struct request *rq, int error, unsigned int nr_bytes) +{ + return blk_end_io(rq, error, nr_bytes, 0, NULL); +} +EXPORT_SYMBOL_GPL(blk_end_request); + +/** + * __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: + * %0 - we are done with this request + * %1 - still buffers pending for this request + **/ +int __blk_end_request(struct request *rq, int error, unsigned int nr_bytes) +{ + if (rq->bio && __end_that_request_first(rq, error, nr_bytes)) + return 1; + + add_disk_randomness(rq->rq_disk); + + end_that_request_last(rq, error); + + return 0; +} +EXPORT_SYMBOL_GPL(__blk_end_request); + +/** + * blk_end_bidi_request - Helper function for drivers to complete bidi request. + * @rq: the bidi request being processed + * @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. + * + * Return: + * %0 - we are done with this request + * %1 - still buffers pending for this request + **/ +int blk_end_bidi_request(struct request *rq, int error, unsigned int nr_bytes, + unsigned int bidi_bytes) +{ + return blk_end_io(rq, error, nr_bytes, bidi_bytes, NULL); +} +EXPORT_SYMBOL_GPL(blk_end_bidi_request); + +/** + * blk_update_request - Special helper function for request stacking drivers + * @rq: the request being processed + * @error: %0 for success, < %0 for error + * @nr_bytes: number of bytes to complete @rq + * + * Description: + * Ends I/O on a number of bytes attached to @rq, but doesn't complete + * the request structure even if @rq doesn't have leftover. + * If @rq 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. + */ +void blk_update_request(struct request *rq, int error, unsigned int nr_bytes) +{ + if (!end_that_request_data(rq, error, nr_bytes, 0)) { + /* + * These members are not updated in end_that_request_data() + * when all bios are completed. + * Update them so that the request stacking driver can find + * how many bytes remain in the request later. + */ + rq->nr_sectors = rq->hard_nr_sectors = 0; + rq->current_nr_sectors = rq->hard_cur_sectors = 0; + } +} +EXPORT_SYMBOL_GPL(blk_update_request); + +/** + * blk_end_request_callback - Special helper function for tricky drivers + * @rq: the request being processed + * @error: %0 for success, < %0 for error + * @nr_bytes: number of bytes to complete + * @drv_callback: function called between completion of bios in the request + * and completion of the request. + * If the callback returns non %0, this helper returns without + * completion of the request. + * + * 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. + * + * This special helper function is used only for existing tricky drivers. + * (e.g. cdrom_newpc_intr() of ide-cd) + * This interface will be removed when such drivers are rewritten. + * Don't use this interface in other places anymore. + * + * Return: + * %0 - we are done with this request + * %1 - this request is not freed yet. + * this request still has pending buffers or + * the driver doesn't want to finish this request yet. + **/ +int blk_end_request_callback(struct request *rq, int error, + unsigned int nr_bytes, + int (drv_callback)(struct request *)) +{ + return blk_end_io(rq, error, nr_bytes, 0, drv_callback); +} +EXPORT_SYMBOL_GPL(blk_end_request_callback); + +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, and + we want BIO_RW_AHEAD (bit 1) to imply REQ_FAILFAST (bit 1). */ + rq->cmd_flags |= (bio->bi_rw & 3); + + if (bio_has_data(bio)) { + rq->nr_phys_segments = bio_phys_segments(q, bio); + rq->buffer = bio_data(bio); + } + rq->current_nr_sectors = bio_cur_sectors(bio); + rq->hard_cur_sectors = rq->current_nr_sectors; + rq->hard_nr_sectors = rq->nr_sectors = bio_sectors(bio); + rq->data_len = bio->bi_size; + + rq->bio = rq->biotail = bio; + + if (bio->bi_bdev) + rq->rq_disk = bio->bi_bdev->bd_disk; +} + +/** + * 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); + +int kblockd_schedule_work(struct request_queue *q, struct work_struct *work) +{ + return queue_work(kblockd_workqueue, work); +} +EXPORT_SYMBOL(kblockd_schedule_work); + +void kblockd_flush_work(struct work_struct *work) +{ + cancel_work_sync(work); +} +EXPORT_SYMBOL(kblockd_flush_work); + +int __init blk_dev_init(void) +{ + kblockd_workqueue = create_workqueue("kblockd"); + 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; +} + |
