/* * 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 #include #include #define CREATE_TRACE_POINTS #include #include "blk.h" #include "blk-cgroup.h" EXPORT_TRACEPOINT_SYMBOL_GPL(block_bio_remap); EXPORT_TRACEPOINT_SYMBOL_GPL(block_rq_remap); EXPORT_TRACEPOINT_SYMBOL_GPL(block_bio_complete); EXPORT_TRACEPOINT_SYMBOL_GPL(block_unplug); DEFINE_IDA(blk_queue_ida); /* * 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. Queue lock must be held. */ void blk_delay_queue(struct request_queue *q, unsigned long msecs) { if (likely(!blk_queue_dead(q))) 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 blkcg_exit_queue() 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_uncond - run a queue whether or not it has been stopped * @q: The queue to run * * Description: * Invoke request handling on a queue if there are any pending requests. * May be used to restart request handling after a request has completed. * This variant runs the queue whether or not the queue has been * stopped. Must be called with the queue lock held and interrupts * disabled. See also @blk_run_queue. */ inline void __blk_run_queue_uncond(struct request_queue *q) { if (unlikely(blk_queue_dead(q))) return; /* * Some request_fn implementations, e.g. scsi_request_fn(), unlock * the queue lock internally. As a result multiple threads may be * running such a request function concurrently. Keep track of the * number of active request_fn invocations such that blk_drain_queue() * can wait until all these request_fn calls have finished. */ q->request_fn_active++; q->request_fn(q); q->request_fn_active--; } /** * __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; __blk_run_queue_uncond(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. The caller must hold the queue lock. */ void blk_run_queue_async(struct request_queue *q) { if (likely(!blk_queue_stopped(q) && !blk_queue_dead(q))) mod_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); /** * __blk_drain_queue - drain requests from request_queue * @q: queue to drain * @drain_all: whether to drain all requests or only the ones w/ ELVPRIV * * Drain requests from @q. If @drain_all is set, all requests are drained. * If not, only ELVPRIV requests are drained. The caller is responsible * for ensuring that no new requests which need to be drained are queued. */ static void __blk_drain_queue(struct request_queue *q, bool drain_all) __releases(q->queue_lock) __acquires(q->queue_lock) { int i; lockdep_assert_held(q->queue_lock); while (true) { bool drain = false; /* * The caller might be trying to drain @q before its * elevator is initialized. */ if (q->elevator) elv_drain_elevator(q); blkcg_drain_queue(q); /* * This function might be called on a queue which failed * driver init after queue creation or is not yet fully * active yet. Some drivers (e.g. fd and loop) get unhappy * in such cases. Kick queue iff dispatch queue has * something on it and @q has request_fn set. */ if (!list_empty(&q->queue_head) && q->request_fn) __blk_run_queue(q); drain |= q->nr_rqs_elvpriv; drain |= q->request_fn_active; /* * Unfortunately, requests are queued at and tracked from * multiple places and there's no single counter which can * be drained. Check all the queues and counters. */ if (drain_all) { drain |= !list_empty(&q->queue_head); for (i = 0; i < 2; i++) { drain |= q->nr_rqs[i]; drain |= q->in_flight[i]; drain |= !list_empty(&q->flush_queue[i]); } } if (!drain) break; spin_unlock_irq(q->queue_lock); msleep(10); spin_lock_irq(q->queue_lock); } /* * With queue marked dead, any woken up waiter will fail the * allocation path, so the wakeup chaining is lost and we're * left with hung waiters. We need to wake up those waiters. */ if (q->request_fn) { struct request_list *rl; blk_queue_for_each_rl(rl, q) for (i = 0; i < ARRAY_SIZE(rl->wait); i++) wake_up_all(&rl->wait[i]); } } /** * blk_queue_bypass_start - enter queue bypass mode * @q: queue of interest * * In bypass mode, only the dispatch FIFO queue of @q is used. This * function makes @q enter bypass mode and drains all requests which were * throttled or issued before. On return, it's guaranteed that no request * is being throttled or has ELVPRIV set and blk_queue_bypass() %true * inside queue or RCU read lock. */ void blk_queue_bypass_start(struct request_queue *q) { bool drain; spin_lock_irq(q->queue_lock); drain = !q->bypass_depth++; queue_flag_set(QUEUE_FLAG_BYPASS, q); spin_unlock_irq(q->queue_lock); if (drain) { spin_lock_irq(q->queue_lock); __blk_drain_queue(q, false); spin_unlock_irq(q->queue_lock); /* ensure blk_queue_bypass() is %true inside RCU read lock */ synchronize_rcu(); } } EXPORT_SYMBOL_GPL(blk_queue_bypass_start); /** * blk_queue_bypass_end - leave queue bypass mode * @q: queue of interest * * Leave bypass mode and restore the normal queueing behavior. */ void blk_queue_bypass_end(struct request_queue *q) { spin_lock_irq(q->queue_lock); if (!--q->bypass_depth) queue_flag_clear(QUEUE_FLAG_BYPASS, q); WARN_ON_ONCE(q->bypass_depth < 0); spin_unlock_irq(q->queue_lock); } EXPORT_SYMBOL_GPL(blk_queue_bypass_end); /** * blk_cleanup_queue - shutdown a request queue * @q: request queue to shutdown * * Mark @q DYING, drain all pending requests, mark @q DEAD, destroy and * put it. All future requests will be failed immediately with -ENODEV. */ void blk_cleanup_queue(struct request_queue *q) { spinlock_t *lock = q->queue_lock; /* mark @q DYING, no new request or merges will be allowed afterwards */ mutex_lock(&q->sysfs_lock); queue_flag_set_unlocked(QUEUE_FLAG_DYING, q); spin_lock_irq(lock); /* * A dying queue is permanently in bypass mode till released. Note * that, unlike blk_queue_bypass_start(), we aren't performing * synchronize_rcu() after entering bypass mode to avoid the delay * as some drivers create and destroy a lot of queues while * probing. This is still safe because blk_release_queue() will be * called only after the queue refcnt drops to zero and nothing, * RCU or not, would be traversing the queue by then. */ q->bypass_depth++; queue_flag_set(QUEUE_FLAG_BYPASS, q); queue_flag_set(QUEUE_FLAG_NOMERGES, q); queue_flag_set(QUEUE_FLAG_NOXMERGES, q); queue_flag_set(QUEUE_FLAG_DYING, q); spin_unlock_irq(lock); mutex_unlock(&q->sysfs_lock); /* * Drain all requests queued before DYING marking. Set DEAD flag to * prevent that q->request_fn() gets invoked after draining finished. */ spin_lock_irq(lock); __blk_drain_queue(q, true); queue_flag_set(QUEUE_FLAG_DEAD, q); spin_unlock_irq(lock); /* @q won't process any more request, flush async actions */ del_timer_sync(&q->backing_dev_info.laptop_mode_wb_timer); blk_sync_queue(q); spin_lock_irq(lock); if (q->queue_lock != &q->__queue_lock) q->queue_lock = &q->__queue_lock; spin_unlock_irq(lock); /* @q is and will stay empty, shutdown and put */ blk_put_queue(q); } EXPORT_SYMBOL(blk_cleanup_queue); int blk_init_rl(struct request_list *rl, struct request_queue *q, gfp_t gfp_mask) { if (unlikely(rl->rq_pool)) return 0; rl->q = q; rl->count[BLK_RW_SYNC] = rl->count[BLK_RW_ASYNC] = 0; rl->starved[BLK_RW_SYNC] = rl->starved[BLK_RW_ASYNC] = 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, gfp_mask, q->node); if (!rl->rq_pool) return -ENOMEM; return 0; } void blk_exit_rl(struct request_list *rl) { if (rl->rq_pool) mempool_destroy(rl->rq_pool); } struct request_queue *blk_alloc_queue(gfp_t gfp_mask) { return blk_alloc_queue_node(gfp_mask, NUMA_NO_NODE); } 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->id = ida_simple_get(&blk_queue_ida, 0, 0, gfp_mask); if (q->id < 0) goto fail_q; 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"; q->node = node_id; err = bdi_init(&q->backing_dev_info); if (err) goto fail_id; 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->queue_head); INIT_LIST_HEAD(&q->timeout_list); INIT_LIST_HEAD(&q->icq_list); #ifdef CONFIG_BLK_CGROUP INIT_LIST_HEAD(&q->blkg_list); #endif 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; /* * A queue starts its life with bypass turned on to avoid * unnecessary bypass on/off overhead and nasty surprises during * init. The initial bypass will be finished when the queue is * registered by blk_register_queue(). */ q->bypass_depth = 1; __set_bit(QUEUE_FLAG_BYPASS, &q->queue_flags); if (blkcg_init_queue(q)) goto fail_id; return q; fail_id: ida_simple_remove(&blk_queue_ida, q->id); fail_q: kmem_cache_free(blk_requestq_cachep, q); return NULL; } 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, NUMA_NO_NODE); } 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(uninit_q, rfn, lock); 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) { if (!q) return NULL; if (blk_init_rl(&q->root_rl, q, GFP_KERNEL)) 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, blk_queue_bio); q->sg_reserved_size = INT_MAX; /* init elevator */ if (elevator_init(q, NULL)) return NULL; return q; } EXPORT_SYMBOL(blk_init_allocated_queue); bool blk_get_queue(struct request_queue *q) { if (likely(!blk_queue_dying(q))) { __blk_get_queue(q); return true; } return false; } EXPORT_SYMBOL(blk_get_queue); static inline void blk_free_request(struct request_list *rl, struct request *rq) { if (rq->cmd_flags & REQ_ELVPRIV) { elv_put_request(rl->q, rq); if (rq->elv.icq) put_io_context(rq->elv.icq->ioc); } mempool_free(rq, rl->rq_pool); } /* * 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_list *rl, int sync) { struct request_queue *q = rl->q; /* * bdi isn't aware of blkcg yet. As all async IOs end up root * blkcg anyway, just use root blkcg state. */ if (rl == &q->root_rl && 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_rl_full(rl, 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_list *rl, unsigned int flags) { struct request_queue *q = rl->q; int sync = rw_is_sync(flags); q->nr_rqs[sync]--; rl->count[sync]--; if (flags & REQ_ELVPRIV) q->nr_rqs_elvpriv--; __freed_request(rl, sync); if (unlikely(rl->starved[sync ^ 1])) __freed_request(rl, 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; } /** * rq_ioc - determine io_context for request allocation * @bio: request being allocated is for this bio (can be %NULL) * * Determine io_context to use for request allocation for @bio. May return * %NULL if %current->io_context doesn't exist. */ static struct io_context *rq_ioc(struct bio *bio) { #ifdef CONFIG_BLK_CGROUP if (bio && bio->bi_ioc) return bio->bi_ioc; #endif return current->io_context; } /** * __get_request - get a free request * @rl: request list to allocate from * @rw_flags: RW and SYNC flags * @bio: bio to allocate request for (can be %NULL) * @gfp_mask: allocation mask * * Get a free request from @q. This function may fail under memory * pressure or if @q is dead. * * Must be callled with @q->queue_lock held and, * Returns %NULL on failure, with @q->queue_lock held. * Returns !%NULL on success, with @q->queue_lock *not held*. */ static struct request *__get_request(struct request_list *rl, int rw_flags, struct bio *bio, gfp_t gfp_mask) { struct request_queue *q = rl->q; struct request *rq; struct elevator_type *et = q->elevator->type; struct io_context *ioc = rq_ioc(bio); struct io_cq *icq = NULL; const bool is_sync = rw_is_sync(rw_flags) != 0; int may_queue; if (unlikely(blk_queue_dying(q))) return NULL; 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) { /* * 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_rl_full(rl, is_sync)) { ioc_set_batching(q, ioc); blk_set_rl_full(rl, 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 */ return NULL; } } } /* * bdi isn't aware of blkcg yet. As all async IOs end up * root blkcg anyway, just use root blkcg state. */ if (rl == &q->root_rl) 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)) return NULL; q->nr_rqs[is_sync]++; rl->count[is_sync]++; rl->starved[is_sync] = 0; /* * Decide whether the new request will be managed by elevator. If * so, mark @rw_flags and increment elvpriv. Non-zero elvpriv will * prevent the current elevator from being destroyed until the new * request is freed. This guarantees icq's won't be destroyed and * makes creating new ones safe. * * Also, lookup icq while holding queue_lock. If it doesn't exist, * it will be created after releasing queue_lock. */ if (blk_rq_should_init_elevator(bio) && !blk_queue_bypass(q)) { rw_flags |= REQ_ELVPRIV; q->nr_rqs_elvpriv++; if (et->icq_cache && ioc) icq = ioc_lookup_icq(ioc, q); } if (blk_queue_io_stat(q)) rw_flags |= REQ_IO_STAT; spin_unlock_irq(q->queue_lock); /* allocate and init request */ rq = mempool_alloc(rl->rq_pool, gfp_mask); if (!rq) goto fail_alloc; blk_rq_init(q, rq); blk_rq_set_rl(rq, rl); rq->cmd_flags = rw_flags | REQ_ALLOCED; /* init elvpriv */ if (rw_flags & REQ_ELVPRIV) { if (unlikely(et->icq_cache && !icq)) { if (ioc) icq = ioc_create_icq(ioc, q, gfp_mask); if (!icq) goto fail_elvpriv; } rq->elv.icq = icq; if (unlikely(elv_set_request(q, rq, bio, gfp_mask))) goto fail_elvpriv; /* @rq->elv.icq holds io_context until @rq is freed */ if (icq) get_io_context(icq->ioc); } 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); return rq; fail_elvpriv: /* * elvpriv init failed. ioc, icq and elvpriv aren't mempool backed * and may fail indefinitely under memory pressure and thus * shouldn't stall IO. Treat this request as !elvpriv. This will * disturb iosched and blkcg but weird is bettern than dead. */ printk_ratelimited(KERN_WARNING "%s: request aux data allocation failed, iosched may be disturbed\n", dev_name(q->backing_dev_info.dev)); rq->cmd_flags &= ~REQ_ELVPRIV; rq->elv.icq = NULL; spin_lock_irq(q->queue_lock); q->nr_rqs_elvpriv--; spin_unlock_irq(q->queue_lock); goto out; fail_alloc: /* * 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(rl, rw_flags); /* * 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; return NULL; } /** * get_request - get a free request * @q: request_queue to allocate request from * @rw_flags: RW and SYNC flags * @bio: bio to allocate request for (can be %NULL) * @gfp_mask: allocation mask * * Get a free request from @q. If %__GFP_WAIT is set in @gfp_mask, this * function keeps retrying under memory pressure and fails iff @q is dead. * * Must be callled with @q->queue_lock held and, * Returns %NULL on failure, with @q->queue_lock held. * Returns !%NULL on success, with @q->queue_lock *not held*. */ static struct request *get_request(struct request_queue *q, int rw_flags, struct bio *bio, gfp_t gfp_mask) { const bool is_sync = rw_is_sync(rw_flags) != 0; DEFINE_WAIT(wait); struct request_list *rl; struct request *rq; rl = blk_get_rl(q, bio); /* transferred to @rq on success */ retry: rq = __get_request(rl, rw_flags, bio, gfp_mask); if (rq) return rq; if (!(gfp_mask & __GFP_WAIT) || unlikely(blk_queue_dying(q))) { blk_put_rl(rl); return NULL; } /* wait on @rl and retry */ 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_set_batching(q, current->io_context); spin_lock_irq(q->queue_lock); finish_wait(&rl->wait[is_sync], &wait); goto retry; } struct request *blk_get_request(struct request_queue *q, int rw, gfp_t gfp_mask) { struct request *rq; BUG_ON(rw != READ && rw != WRITE); /* create ioc upfront */ create_io_context(gfp_mask, q->node); spin_lock_irq(q->queue_lock); 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); } 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) { unsigned int flags = req->cmd_flags; struct request_list *rl = blk_rq_rl(req); BUG_ON(!list_empty(&req->queuelist)); BUG_ON(!hlist_unhashed(&req->hash)); blk_free_request(rl, req); freed_request(rl, flags); blk_put_rl(rl); } } 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); /** * 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; 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; 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); 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; } /** * attempt_plug_merge - try to merge with %current's plugged list * @q: request_queue new bio is being queued at * @bio: new bio being queued * @request_count: out parameter for number of traversed plugged requests * * Determine whether @bio being queued on @q can be merged with a request * on %current's plugged list. Returns %true if merge was successful, * otherwise %false. * * Plugging coalesces IOs from the same issuer for the same purpose without * going through @q->queue_lock. As such it's more of an issuing mechanism * than scheduling, and the request, while may have elvpriv data, is not * added on the elevator at this point. In addition, we don't have * reliable access to the elevator outside queue lock. Only check basic * merging parameters without querying the elevator. */ static bool attempt_plug_merge(struct request_queue *q, struct bio *bio, unsigned int *request_count) { struct blk_plug *plug; struct request *rq; bool ret = false; plug = current->plug; if (!plug) goto out; *request_count = 0; list_for_each_entry_reverse(rq, &plug->list, queuelist) { int el_ret; if (rq->q == q) (*request_count)++; if (rq->q != q || !blk_rq_merge_ok(rq, bio)) continue; el_ret = blk_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->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); } void blk_queue_bio(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; unsigned int request_count = 0; /* * 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(q, bio, &request_count)) return; spin_lock_irq(q->queue_lock); el_ret = elv_merge(q, &req, bio); if (el_ret == ELEVATOR_BACK_MERGE) { if (bio_attempt_back_merge(q, req, bio)) { elv_bio_merged(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) { if (bio_attempt_front_merge(q, req, bio)) { elv_bio_merged(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(q, rw_flags, bio, GFP_NOIO); if (unlikely(!req)) { bio_endio(bio, -ENODEV); /* @q is dead */ goto out_unlock; } /* * 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)) req->cpu = raw_smp_processor_id(); 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; } if (request_count >= BLK_MAX_REQUEST_COUNT) { blk_flush_plug_list(plug, false); trace_block_plug(q); } } 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); } } EXPORT_SYMBOL_GPL(blk_queue_bio); /* for device mapper only */ /* * 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 bool should_fail_request(struct hd_struct *part, unsigned int bytes) { return part->make_it_fail && should_fail(&fail_make_request, bytes); } static int __init fail_make_request_debugfs(void) { struct dentry *dir = fault_create_debugfs_attr("fail_make_request", NULL, &fail_make_request); return IS_ERR(dir) ? PTR_ERR(dir) : 0; } late_initcall(fail_make_request_debugfs); #else /* CONFIG_FAIL_MAKE_REQUEST */ static inline bool should_fail_request(struct hd_struct *part, unsigned int bytes) { return false; } #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; } static noinline_for_stack bool generic_make_request_checks(struct bio *bio) { struct request_queue *q; int nr_sectors = bio_sectors(bio); int err = -EIO; char b[BDEVNAME_SIZE]; struct hd_struct *part; might_sleep(); if (bio_check_eod(bio, nr_sectors)) goto end_io; 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 (likely(bio_is_rw(bio) && 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; } part = bio->bi_bdev->bd_part; if (should_fail_request(part, bio->bi_size) || should_fail_request(&part_to_disk(part)->part0, bio->bi_size)) 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 (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; } if (bio->bi_rw & REQ_WRITE_SAME && !bdev_write_same(bio->bi_bdev)) { err = -EOPNOTSUPP; goto end_io; } /* * Various block parts want %current->io_context and lazy ioc * allocation ends up trading a lot of pain for a small amount of * memory. Just allocate it upfront. This may fail and block * layer knows how to live with it. */ create_io_context(GFP_ATOMIC, q->node); if (blk_throtl_bio(q, bio)) return false; /* throttled, will be resubmitted later */ trace_block_bio_queue(q, bio); return true; end_io: bio_endio(bio, err); return false; } /** * 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 resubmit the bio to * a lower device by calling into generic_make_request recursively, which * means the bio should NOT be touched after the call to ->make_request_fn. */ void generic_make_request(struct bio *bio) { struct bio_list bio_list_on_stack; if (!generic_make_request_checks(bio)) return; /* * 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 */ if (current->bio_list) { 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. ->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 ->make_request() again. */ BUG_ON(bio->bi_next); bio_list_init(&bio_list_on_stack); current->bio_list = &bio_list_on_stack; do { struct request_queue *q = bdev_get_queue(bio->bi_bdev); q->make_request_fn(q, 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) { 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)) { unsigned int count; if (unlikely(rw & REQ_WRITE_SAME)) count = bdev_logical_block_size(bio->bi_bdev) >> 9; else count = bio_sectors(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 (%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_mergeable(rq)) return 0; if (blk_rq_sectors(rq) > blk_queue_get_max_sectors(q, rq->cmd_flags)) { 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; int where = ELEVATOR_INSERT_BACK; if (blk_rq_check_limits(q, rq)) return -EIO; if (rq->rq_disk && should_fail_request(&rq->rq_disk->part0, blk_rq_bytes(rq))) return -EIO; spin_lock_irqsave(q->queue_lock, flags); if (unlikely(blk_queue_dying(q))) { spin_unlock_irqrestore(q->queue_lock, flags); return -ENODEV; } /* * Submitting request must be dequeued before calling this function * because it will be linked to another request_queue */ BUG_ON(blk_queued_rq(rq)); if (rq->cmd_flags & (REQ_FLUSH|REQ_FUA)) where = ELEVATOR_INSERT_FLUSH; add_acct_request(q, rq, where); if (where == ELEVATOR_INSERT_FLUSH) __blk_run_queue(q); 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;