/* * 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 #include #include #include #include #include #define CREATE_TRACE_POINTS #include #include "blk.h" #include "blk-mq.h" #include "blk-mq-sched.h" #include "blk-pm.h" #include "blk-rq-qos.h" #ifdef CONFIG_DEBUG_FS struct dentry *blk_debugfs_root; #endif 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_split); EXPORT_TRACEPOINT_SYMBOL_GPL(block_unplug); DEFINE_IDA(blk_queue_ida); /* * For queue allocation */ struct kmem_cache *blk_requestq_cachep; /* * Controlling structure to kblockd */ static struct workqueue_struct *kblockd_workqueue; /** * blk_queue_flag_set - atomically set a queue flag * @flag: flag to be set * @q: request queue */ void blk_queue_flag_set(unsigned int flag, struct request_queue *q) { set_bit(flag, &q->queue_flags); } EXPORT_SYMBOL(blk_queue_flag_set); /** * blk_queue_flag_clear - atomically clear a queue flag * @flag: flag to be cleared * @q: request queue */ void blk_queue_flag_clear(unsigned int flag, struct request_queue *q) { clear_bit(flag, &q->queue_flags); } EXPORT_SYMBOL(blk_queue_flag_clear); /** * blk_queue_flag_test_and_set - atomically test and set a queue flag * @flag: flag to be set * @q: request queue * * Returns the previous value of @flag - 0 if the flag was not set and 1 if * the flag was already set. */ bool blk_queue_flag_test_and_set(unsigned int flag, struct request_queue *q) { return test_and_set_bit(flag, &q->queue_flags); } EXPORT_SYMBOL_GPL(blk_queue_flag_test_and_set); void blk_rq_init(struct request_queue *q, struct request *rq) { memset(rq, 0, sizeof(*rq)); INIT_LIST_HEAD(&rq->queuelist); rq->q = q; rq->__sector = (sector_t) -1; INIT_HLIST_NODE(&rq->hash); RB_CLEAR_NODE(&rq->rb_node); rq->tag = -1; rq->internal_tag = -1; rq->start_time_ns = ktime_get_ns(); rq->part = NULL; } EXPORT_SYMBOL(blk_rq_init); static const struct { int errno; const char *name; } blk_errors[] = { [BLK_STS_OK] = { 0, "" }, [BLK_STS_NOTSUPP] = { -EOPNOTSUPP, "operation not supported" }, [BLK_STS_TIMEOUT] = { -ETIMEDOUT, "timeout" }, [BLK_STS_NOSPC] = { -ENOSPC, "critical space allocation" }, [BLK_STS_TRANSPORT] = { -ENOLINK, "recoverable transport" }, [BLK_STS_TARGET] = { -EREMOTEIO, "critical target" }, [BLK_STS_NEXUS] = { -EBADE, "critical nexus" }, [BLK_STS_MEDIUM] = { -ENODATA, "critical medium" }, [BLK_STS_PROTECTION] = { -EILSEQ, "protection" }, [BLK_STS_RESOURCE] = { -ENOMEM, "kernel resource" }, [BLK_STS_DEV_RESOURCE] = { -EBUSY, "device resource" }, [BLK_STS_AGAIN] = { -EAGAIN, "nonblocking retry" }, /* device mapper special case, should not leak out: */ [BLK_STS_DM_REQUEUE] = { -EREMCHG, "dm internal retry" }, /* everything else not covered above: */ [BLK_STS_IOERR] = { -EIO, "I/O" }, }; blk_status_t errno_to_blk_status(int errno) { int i; for (i = 0; i < ARRAY_SIZE(blk_errors); i++) { if (blk_errors[i].errno == errno) return (__force blk_status_t)i; } return BLK_STS_IOERR; } EXPORT_SYMBOL_GPL(errno_to_blk_status); int blk_status_to_errno(blk_status_t status) { int idx = (__force int)status; if (WARN_ON_ONCE(idx >= ARRAY_SIZE(blk_errors))) return -EIO; return blk_errors[idx].errno; } EXPORT_SYMBOL_GPL(blk_status_to_errno); static void print_req_error(struct request *req, blk_status_t status) { int idx = (__force int)status; if (WARN_ON_ONCE(idx >= ARRAY_SIZE(blk_errors))) return; printk_ratelimited(KERN_ERR "%s: %s error, dev %s, sector %llu\n", __func__, blk_errors[idx].name, req->rq_disk ? req->rq_disk->disk_name : "?", (unsigned long long)blk_rq_pos(req)); } static void req_bio_endio(struct request *rq, struct bio *bio, unsigned int nbytes, blk_status_t error) { if (error) bio->bi_status = error; if (unlikely(rq->rq_flags & RQF_QUIET)) bio_set_flag(bio, BIO_QUIET); bio_advance(bio, nbytes); /* don't actually finish bio if it's part of flush sequence */ if (bio->bi_iter.bi_size == 0 && !(rq->rq_flags & RQF_FLUSH_SEQ)) bio_endio(bio); } void blk_dump_rq_flags(struct request *rq, char *msg) { printk(KERN_INFO "%s: dev %s: flags=%llx\n", msg, rq->rq_disk ? rq->rq_disk->disk_name : "?", (unsigned long long) 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, len %u\n", rq->bio, rq->biotail, blk_rq_bytes(rq)); } EXPORT_SYMBOL(blk_dump_rq_flags); /** * 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 elevator_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_work_sync(&q->timeout_work); if (queue_is_mq(q)) { struct blk_mq_hw_ctx *hctx; int i; cancel_delayed_work_sync(&q->requeue_work); queue_for_each_hw_ctx(q, hctx, i) cancel_delayed_work_sync(&hctx->run_work); } } EXPORT_SYMBOL(blk_sync_queue); /** * blk_set_pm_only - increment pm_only counter * @q: request queue pointer */ void blk_set_pm_only(struct request_queue *q) { atomic_inc(&q->pm_only); } EXPORT_SYMBOL_GPL(blk_set_pm_only); void blk_clear_pm_only(struct request_queue *q) { int pm_only; pm_only = atomic_dec_return(&q->pm_only); WARN_ON_ONCE(pm_only < 0); if (pm_only == 0) wake_up_all(&q->mq_freeze_wq); } EXPORT_SYMBOL_GPL(blk_clear_pm_only); void blk_put_queue(struct request_queue *q) { kobject_put(&q->kobj); } EXPORT_SYMBOL(blk_put_queue); void blk_set_queue_dying(struct request_queue *q) { blk_queue_flag_set(QUEUE_FLAG_DYING, q); /* * When queue DYING flag is set, we need to block new req * entering queue, so we call blk_freeze_queue_start() to * prevent I/O from crossing blk_queue_enter(). */ blk_freeze_queue_start(q); if (queue_is_mq(q)) blk_mq_wake_waiters(q); /* Make blk_queue_enter() reexamine the DYING flag. */ wake_up_all(&q->mq_freeze_wq); } EXPORT_SYMBOL_GPL(blk_set_queue_dying); /* Unconfigure the I/O scheduler and dissociate from the cgroup controller. */ void blk_exit_queue(struct request_queue *q) { /* * Since the I/O scheduler exit code may access cgroup information, * perform I/O scheduler exit before disassociating from the block * cgroup controller. */ if (q->elevator) { ioc_clear_queue(q); elevator_exit(q, q->elevator); q->elevator = NULL; } /* * Remove all references to @q from the block cgroup controller before * restoring @q->queue_lock to avoid that restoring this pointer causes * e.g. blkcg_print_blkgs() to crash. */ blkcg_exit_queue(q); /* * Since the cgroup code may dereference the @q->backing_dev_info * pointer, only decrease its reference count after having removed the * association with the block cgroup controller. */ bdi_put(q->backing_dev_info); } /** * 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) { /* mark @q DYING, no new request or merges will be allowed afterwards */ mutex_lock(&q->sysfs_lock); blk_set_queue_dying(q); blk_queue_flag_set(QUEUE_FLAG_NOMERGES, q); blk_queue_flag_set(QUEUE_FLAG_NOXMERGES, q); blk_queue_flag_set(QUEUE_FLAG_DYING, q); 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. */ blk_freeze_queue(q); rq_qos_exit(q); blk_queue_flag_set(QUEUE_FLAG_DEAD, q); /* * make sure all in-progress dispatch are completed because * blk_freeze_queue() can only complete all requests, and * dispatch may still be in-progress since we dispatch requests * from more than one contexts. * * We rely on driver to deal with the race in case that queue * initialization isn't done. */ if (queue_is_mq(q) && blk_queue_init_done(q)) blk_mq_quiesce_queue(q); /* for synchronous bio-based driver finish in-flight integrity i/o */ blk_flush_integrity(); /* @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); /* * I/O scheduler exit is only safe after the sysfs scheduler attribute * has been removed. */ WARN_ON_ONCE(q->kobj.state_in_sysfs); blk_exit_queue(q); if (queue_is_mq(q)) blk_mq_free_queue(q); percpu_ref_exit(&q->q_usage_counter); /* @q is and will stay empty, shutdown and put */ blk_put_queue(q); } EXPORT_SYMBOL(blk_cleanup_queue); 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); /** * blk_queue_enter() - try to increase q->q_usage_counter * @q: request queue pointer * @flags: BLK_MQ_REQ_NOWAIT and/or BLK_MQ_REQ_PREEMPT */ int blk_queue_enter(struct request_queue *q, blk_mq_req_flags_t flags) { const bool pm = flags & BLK_MQ_REQ_PREEMPT; while (true) { bool success = false; rcu_read_lock(); if (percpu_ref_tryget_live(&q->q_usage_counter)) { /* * The code that increments the pm_only counter is * responsible for ensuring that that counter is * globally visible before the queue is unfrozen. */ if (pm || !blk_queue_pm_only(q)) { success = true; } else { percpu_ref_put(&q->q_usage_counter); } } rcu_read_unlock(); if (success) return 0; if (flags & BLK_MQ_REQ_NOWAIT) return -EBUSY; /* * read pair of barrier in blk_freeze_queue_start(), * we need to order reading __PERCPU_REF_DEAD flag of * .q_usage_counter and reading .mq_freeze_depth or * queue dying flag, otherwise the following wait may * never return if the two reads are reordered. */ smp_rmb(); wait_event(q->mq_freeze_wq, (atomic_read(&q->mq_freeze_depth) == 0 && (pm || (blk_pm_request_resume(q), !blk_queue_pm_only(q)))) || blk_queue_dying(q)); if (blk_queue_dying(q)) return -ENODEV; } } void blk_queue_exit(struct request_queue *q) { percpu_ref_put(&q->q_usage_counter); } static void blk_queue_usage_counter_release(struct percpu_ref *ref) { struct request_queue *q = container_of(ref, struct request_queue, q_usage_counter); wake_up_all(&q->mq_freeze_wq); } static void blk_rq_timed_out_timer(struct timer_list *t) { struct request_queue *q = from_timer(q, t, timeout); kblockd_schedule_work(&q->timeout_work); } /** * blk_alloc_queue_node - allocate a request queue * @gfp_mask: memory allocation flags * @node_id: NUMA node to allocate memory from */ struct request_queue *blk_alloc_queue_node(gfp_t gfp_mask, int node_id) { struct request_queue *q; int ret; q = kmem_cache_alloc_node(blk_requestq_cachep, gfp_mask | __GFP_ZERO, node_id); if (!q) return NULL; INIT_LIST_HEAD(&q->queue_head); q->last_merge = NULL; q->id = ida_simple_get(&blk_queue_ida, 0, 0, gfp_mask); if (q->id < 0) goto fail_q; ret = bioset_init(&q->bio_split, BIO_POOL_SIZE, 0, BIOSET_NEED_BVECS); if (ret) goto fail_id; q->backing_dev_info = bdi_alloc_node(gfp_mask, node_id); if (!q->backing_dev_info) goto fail_split; q->stats = blk_alloc_queue_stats(); if (!q->stats) goto fail_stats; q->backing_dev_info->ra_pages = (VM_MAX_READAHEAD * 1024) / PAGE_SIZE; q->backing_dev_info->capabilities = BDI_CAP_CGROUP_WRITEBACK; q->backing_dev_info->name = "block"; q->node = node_id; timer_setup(&q->backing_dev_info->laptop_mode_wb_timer, laptop_mode_timer_fn, 0); timer_setup(&q->timeout, blk_rq_timed_out_timer, 0); INIT_WORK(&q->timeout_work, NULL); INIT_LIST_HEAD(&q->icq_list); #ifdef CONFIG_BLK_CGROUP INIT_LIST_HEAD(&q->blkg_list); #endif kobject_init(&q->kobj, &blk_queue_ktype); #ifdef CONFIG_BLK_DEV_IO_TRACE mutex_init(&q->blk_trace_mutex); #endif mutex_init(&q->sysfs_lock); spin_lock_init(&q->queue_lock); init_waitqueue_head(&q->mq_freeze_wq); /* * Init percpu_ref in atomic mode so that it's faster to shutdown. * See blk_register_queue() for details. */ if (percpu_ref_init(&q->q_usage_counter, blk_queue_usage_counter_release, PERCPU_REF_INIT_ATOMIC, GFP_KERNEL)) goto fail_bdi; if (blkcg_init_queue(q)) goto fail_ref; return q; fail_ref: percpu_ref_exit(&q->q_usage_counter); fail_bdi: blk_free_queue_stats(q->stats); fail_stats: bdi_put(q->backing_dev_info); fail_split: bioset_exit(&q->bio_split); 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); 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); /** * blk_get_request - allocate a request * @q: request queue to allocate a request for * @op: operation (REQ_OP_*) and REQ_* flags, e.g. REQ_SYNC. * @flags: BLK_MQ_REQ_* flags, e.g. BLK_MQ_REQ_NOWAIT. */ struct request *blk_get_request(struct request_queue *q, unsigned int op, blk_mq_req_flags_t flags) { struct request *req; WARN_ON_ONCE(op & REQ_NOWAIT); WARN_ON_ONCE(flags & ~(BLK_MQ_REQ_NOWAIT | BLK_MQ_REQ_PREEMPT)); req = blk_mq_alloc_request(q, op, flags); if (!IS_ERR(req) && q->mq_ops->initialize_rq_fn) q->mq_ops->initialize_rq_fn(req); return req; } EXPORT_SYMBOL(blk_get_request); static void part_round_stats_single(struct request_queue *q, int cpu, struct hd_struct *part, unsigned long now, unsigned int inflight) { if (inflight) { __part_stat_add(cpu, part, time_in_queue, inflight * (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. * @q: target block queue * @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(struct request_queue *q, int cpu, struct hd_struct *part) { struct hd_struct *part2 = NULL; unsigned long now = jiffies; unsigned int inflight[2]; int stats = 0; if (part->stamp != now) stats |= 1; if (part->partno) { part2 = &part_to_disk(part)->part0; if (part2->stamp != now) stats |= 2; } if (!stats) return; part_in_flight(q, part, inflight); if (stats & 2) part_round_stats_single(q, cpu, part2, now, inflight[1]); if (stats & 1) part_round_stats_single(q, cpu, part, now, inflight[0]); } EXPORT_SYMBOL_GPL(part_round_stats); void blk_put_request(struct request *req) { blk_mq_free_request(req); } EXPORT_SYMBOL(blk_put_request); bool bio_attempt_back_merge(struct request_queue *q, struct request *req, struct bio *bio) { const int ff = bio->bi_opf & REQ_FAILFAST_MASK; if (!ll_back_merge_fn(q, req, bio)) return false; trace_block_bio_backmerge(q, req, 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_iter.bi_size; blk_account_io_start(req, false); return true; } bool bio_attempt_front_merge(struct request_queue *q, struct request *req, struct bio *bio) { const int ff = bio->bi_opf & REQ_FAILFAST_MASK; if (!ll_front_merge_fn(q, req, bio)) return false; trace_block_bio_frontmerge(q, req, bio); if ((req->cmd_flags & REQ_FAILFAST_MASK) != ff) blk_rq_set_mixed_merge(req); bio->bi_next = req->bio; req->bio = bio; req->__sector = bio->bi_iter.bi_sector; req->__data_len += bio->bi_iter.bi_size; blk_account_io_start(req, false); return true; } bool bio_attempt_discard_merge(struct request_queue *q, struct request *req, struct bio *bio) { unsigned short segments = blk_rq_nr_discard_segments(req); if (segments >= queue_max_discard_segments(q)) goto no_merge; if (blk_rq_sectors(req) + bio_sectors(bio) > blk_rq_get_max_sectors(req, blk_rq_pos(req))) goto no_merge; req->biotail->bi_next = bio; req->biotail = bio; req->__data_len += bio->bi_iter.bi_size; req->nr_phys_segments = segments + 1; blk_account_io_start(req, false); return true; no_merge: req_set_nomerge(q, req); return false; } /** * blk_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 * @same_queue_rq: pointer to &struct request that gets filled in when * another request associated with @q is found on the plug list * (optional, may be %NULL) * * 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. * * Caller must ensure !blk_queue_nomerges(q) beforehand. */ bool blk_attempt_plug_merge(struct request_queue *q, struct bio *bio, struct request **same_queue_rq) { struct blk_plug *plug; struct request *rq; struct list_head *plug_list; plug = current->plug; if (!plug) return false; plug_list = &plug->mq_list; list_for_each_entry_reverse(rq, plug_list, queuelist) { bool merged = false; if (rq->q == q && same_queue_rq) { /* * Only blk-mq multiple hardware queues case checks the * rq in the same queue, there should be only one such * rq in a queue **/ *same_queue_rq = rq; } if (rq->q != q || !blk_rq_merge_ok(rq, bio)) continue; switch (blk_try_merge(rq, bio)) { case ELEVATOR_BACK_MERGE: merged = bio_attempt_back_merge(q, rq, bio); break; case ELEVATOR_FRONT_MERGE: merged = bio_attempt_front_merge(q, rq, bio); break; case ELEVATOR_DISCARD_MERGE: merged = bio_attempt_discard_merge(q, rq, bio); break; default: break; } if (merged) return true; } return false; } void blk_init_request_from_bio(struct request *req, struct bio *bio) { if (bio->bi_opf & REQ_RAHEAD) req->cmd_flags |= REQ_FAILFAST_MASK; req->__sector = bio->bi_iter.bi_sector; req->ioprio = bio_prio(bio); req->write_hint = bio->bi_write_hint; blk_rq_bio_prep(req->q, req, bio); } EXPORT_SYMBOL_GPL(blk_init_request_from_bio); static void handle_bad_sector(struct bio *bio, sector_t maxsector) { char b[BDEVNAME_SIZE]; printk(KERN_INFO "attempt to access beyond end of device\n"); printk(KERN_INFO "%s: rw=%d, want=%Lu, limit=%Lu\n", bio_devname(bio, b), bio->bi_opf, (unsigned long long)bio_end_sector(bio), (long long)maxsector); } #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 PTR_ERR_OR_ZERO(dir); } 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 */ static inline bool bio_check_ro(struct bio *bio, struct hd_struct *part) { const int op = bio_op(bio); if (part->policy && op_is_write(op)) { char b[BDEVNAME_SIZE]; if (op_is_flush(bio->bi_opf) && !bio_sectors(bio)) return false; WARN_ONCE(1, "generic_make_request: Trying to write " "to read-only block-device %s (partno %d)\n", bio_devname(bio, b), part->partno); /* Older lvm-tools actually trigger this */ return false; } return false; } static noinline int should_fail_bio(struct bio *bio) { if (should_fail_request(&bio->bi_disk->part0, bio->bi_iter.bi_size)) return -EIO; return 0; } ALLOW_ERROR_INJECTION(should_fail_bio, ERRNO); /* * Check whether this bio extends beyond the end of the device or partition. * This may well happen - the kernel calls bread() without checking the size of * the device, e.g., when mounting a file system. */ static inline int bio_check_eod(struct bio *bio, sector_t maxsector) { unsigned int nr_sectors = bio_sectors(bio); if (nr_sectors && maxsector && (nr_sectors > maxsector || bio->bi_iter.bi_sector > maxsector - nr_sectors)) { handle_bad_sector(bio, maxsector); return -EIO; } return 0; } /* * Remap block n of partition p to block n+start(p) of the disk. */ static inline int blk_partition_remap(struct bio *bio) { struct hd_struct *p; int ret = -EIO; rcu_read_lock(); p = __disk_get_part(bio->bi_disk, bio->bi_partno); if (unlikely(!p)) goto out; if (unlikely(should_fail_request(p, bio->bi_iter.bi_size))) goto out; if (unlikely(bio_check_ro(bio, p))) goto out; /* * Zone reset does not include bi_size so bio_sectors() is always 0. * Include a test for the reset op code and perform the remap if needed. */ if (bio_sectors(bio) || bio_op(bio) == REQ_OP_ZONE_RESET) { if (bio_check_eod(bio, part_nr_sects_read(p))) goto out; bio->bi_iter.bi_sector += p->start_sect; trace_block_bio_remap(bio->bi_disk->queue, bio, part_devt(p), bio->bi_iter.bi_sector - p->start_sect); } bio->bi_partno = 0; ret = 0; out: rcu_read_unlock(); return ret; } static noinline_for_stack bool generic_make_request_checks(struct bio *bio) { struct request_queue *q; int nr_sectors = bio_sectors(bio); blk_status_t status = BLK_STS_IOERR; char b[BDEVNAME_SIZE]; might_sleep(); q = bio->bi_disk->queue; if (unlikely(!q)) { printk(KERN_ERR "generic_make_request: Trying to access " "nonexistent block-device %s (%Lu)\n", bio_devname(bio, b), (long long)bio->bi_iter.bi_sector); goto end_io; } /* * For a REQ_NOWAIT based request, return -EOPNOTSUPP * if queue is not a request based queue. */ if ((bio->bi_opf & REQ_NOWAIT) && !queue_is_mq(q)) goto not_supported; if (should_fail_bio(bio)) goto end_io; if (bio->bi_partno) { if (unlikely(blk_partition_remap(bio))) goto end_io; } else { if (unlikely(bio_check_ro(bio, &bio->bi_disk->part0))) goto end_io; if (unlikely(bio_check_eod(bio, get_capacity(bio->bi_disk)))) 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 (op_is_flush(bio->bi_opf) && !test_bit(QUEUE_FLAG_WC, &q->queue_flags)) { bio->bi_opf &= ~(REQ_PREFLUSH | REQ_FUA); if (!nr_sectors) { status = BLK_STS_OK; goto end_io; } } switch (bio_op(bio)) { case REQ_OP_DISCARD: if (!blk_queue_discard(q)) goto not_supported; break; case REQ_OP_SECURE_ERASE: if (!blk_queue_secure_erase(q)) goto not_supported; break; case REQ_OP_WRITE_SAME: if (!q->limits.max_write_same_sectors) goto not_supported; break; case REQ_OP_ZONE_RESET: if (!blk_queue_is_zoned(q)) goto not_supported; break; case REQ_OP_WRITE_ZEROES: if (!q->limits.max_write_zeroes_sectors) goto not_supported; break; default: break; } /* * 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 (!blkcg_bio_issue_check(q, bio)) return false; if (!bio_flagged(bio, BIO_TRACE_COMPLETION)) { trace_block_bio_queue(q, bio); /* Now that enqueuing has been traced, we need to trace * completion as well. */ bio_set_flag(bio, BIO_TRACE_COMPLETION); } return true; not_supported: status = BLK_STS_NOTSUPP; end_io: bio->bi_status = status; bio_endio(bio); 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. */ blk_qc_t generic_make_request(struct bio *bio) { /* * bio_list_on_stack[0] contains bios submitted by the current * make_request_fn. * bio_list_on_stack[1] contains bios that were submitted before * the current make_request_fn, but that haven't been processed * yet. */ struct bio_list bio_list_on_stack[2]; blk_mq_req_flags_t flags = 0; struct request_queue *q = bio->bi_disk->queue; blk_qc_t ret = BLK_QC_T_NONE; if (bio->bi_opf & REQ_NOWAIT) flags = BLK_MQ_REQ_NOWAIT; if (bio_flagged(bio, BIO_QUEUE_ENTERED)) blk_queue_enter_live(q); else if (blk_queue_enter(q, flags) < 0) { if (!blk_queue_dying(q) && (bio->bi_opf & REQ_NOWAIT)) bio_wouldblock_error(bio); else bio_io_error(bio); return ret; } if (!generic_make_request_checks(bio)) goto out; /* * 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(¤t->bio_list[0], bio); goto out; } /* 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[0]); current->bio_list = bio_list_on_stack; do { bool enter_succeeded = true; if (unlikely(q != bio->bi_disk->queue)) { if (q) blk_queue_exit(q); q = bio->bi_disk->queue; flags = 0; if (bio->bi_opf & REQ_NOWAIT) flags = BLK_MQ_REQ_NOWAIT; if (blk_queue_enter(q, flags) < 0) { enter_succeeded = false; q = NULL; } } if (enter_succeeded) { struct bio_list lower, same; /* Create a fresh bio_list for all subordinate requests */ bio_list_on_stack[1] = bio_list_on_stack[0]; bio_list_init(&bio_list_on_stack[0]); ret = q->make_request_fn(q, bio); /* sort new bios into those for a lower level * and those for the same level */ bio_list_init(&lower); bio_list_init(&same); while ((bio = bio_list_pop(&bio_list_on_stack[0])) != NULL) if (q == bio->bi_disk->queue) bio_list_add(&same, bio); else bio_list_add(&lower, bio); /* now assemble so we handle the lowest level first */ bio_list_merge(&bio_list_on_stack[0], &lower); bio_list_merge(&bio_list_on_stack[0], &same); bio_list_merge(&bio_list_on_stack[0], &bio_list_on_stack[1]); } else { if (unlikely(!blk_queue_dying(q) && (bio->bi_opf & REQ_NOWAIT))) bio_wouldblock_error(bio); else bio_io_error(bio); } bio = bio_list_pop(&bio_list_on_stack[0]); } while (bio); current->bio_list = NULL; /* deactivate */ out: if (q) blk_queue_exit(q); return ret; } EXPORT_SYMBOL(generic_make_request); /** * direct_make_request - hand a buffer directly to its device driver for I/O * @bio: The bio describing the location in memory and on the device. * * This function behaves like generic_make_request(), but does not protect * against recursion. Must only be used if the called driver is known * to not call generic_make_request (or direct_make_request) again from * its make_request function. (Calling direct_make_request again from * a workqueue is perfectly fine as that doesn't recurse). */ blk_qc_t direct_make_request(struct bio *bio) { struct request_queue *q = bio->bi_disk->queue; bool nowait = bio->bi_opf & REQ_NOWAIT; blk_qc_t ret; if (!generic_make_request_checks(bio)) return BLK_QC_T_NONE; if (unlikely(blk_queue_enter(q, nowait ? BLK_MQ_REQ_NOWAIT : 0))) { if (nowait && !blk_queue_dying(q)) bio->bi_status = BLK_STS_AGAIN; else bio->bi_status = BLK_STS_IOERR; bio_endio(bio); return BLK_QC_T_NONE; } ret = q->make_request_fn(q, bio); blk_queue_exit(q); return ret; } EXPORT_SYMBOL_GPL(direct_make_request); /** * submit_bio - submit a bio to the block device layer for I/O * @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. * */ blk_qc_t submit_bio(struct bio *bio) { /* * 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(bio_op(bio) == REQ_OP_WRITE_SAME)) count = queue_logical_block_size(bio->bi_disk->queue) >> 9; else count = bio_sectors(bio); if (op_is_write(bio_op(bio))) { count_vm_events(PGPGOUT, count); } else { task_io_account_read(bio->bi_iter.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), op_is_write(bio_op(bio)) ? "WRITE" : "READ", (unsigned long long)bio->bi_iter.bi_sector, bio_devname(bio, b), count); } } return generic_make_request(bio); } EXPORT_SYMBOL(submit_bio); /** * blk_poll - poll for IO completions * @q: the queue * @cookie: cookie passed back at IO submission time * @spin: whether to spin for completions * * Description: * Poll for completions on the passed in queue. Returns number of * completed entries found. If @spin is true, then blk_poll will continue * looping until at least one completion is found, unless the task is * otherwise marked running (or we need to reschedule). */ int blk_poll(struct request_queue *q, blk_qc_t cookie, bool spin) { if (!q->poll_fn || !blk_qc_t_valid(cookie)) return 0; if (current->plug) blk_flush_plug_list(current->plug, false); return q->poll_fn(q, cookie, spin); } EXPORT_SYMBOL_GPL(blk_poll); /** * blk_cloned_rq_check_limits - Helper function to check a cloned request * for new the queue limits * @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. * * Request stacking drivers like request-based dm may change the queue * limits when retrying requests on other queues. Those requests need * to be checked against the new queue limits again during dispatch. */ static int blk_cloned_rq_check_limits(struct request_queue *q, struct request *rq) { if (blk_rq_sectors(rq) > blk_queue_get_max_sectors(q, req_op(rq))) { 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; } /** * blk_insert_cloned_request - Helper for stacking drivers to submit a request * @q: the queue to submit the request * @rq: the request being queued */ blk_status_t blk_insert_cloned_request(struct request_queue *q, struct request *rq) { if (blk_cloned_rq_check_limits(q, rq)) return BLK_STS_IOERR; if (rq->rq_disk && should_fail_request(&rq->rq_disk->part0, blk_rq_bytes(rq))) return BLK_STS_IOERR; if (blk_queue_io_stat(q)) blk_account_io_start(rq, true); /* * Since we have a scheduler attached on the top device, * bypass a potential scheduler on the bottom device for * insert. */ return blk_mq_request_issue_directly(rq); } 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. */ 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->rq_flags & RQF_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_opf & ff) != ff) break; bytes += bio->bi_iter.bi_size; } /* this could lead to infinite loop */ BUG_ON(blk_rq_bytes(rq) && !bytes); return bytes; } EXPORT_SYMBOL_GPL(blk_rq_err_bytes); void blk_account_io_completion(struct request *req, unsigned int bytes) { if (blk_do_io_stat(req)) { const int sgrp = op_stat_group(req_op(req)); struct hd_struct *part; int cpu; cpu = part_stat_lock(); part = req->part; part_stat_add(cpu, part, sectors[sgrp], bytes >> 9); part_stat_unlock(); } } void blk_account_io_done(struct request *req, u64 now) { /* * 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->rq_flags & RQF_FLUSH_SEQ)) { const int sgrp = op_stat_group(req_op(req)); struct hd_struct *part; int cpu; cpu = part_stat_lock(); part = req->part; part_stat_inc(cpu, part, ios[sgrp]); part_stat_add(cpu, part, nsecs[sgrp], now - req->start_time_ns); part_round_stats(req->q, cpu, part); part_dec_in_flight(req->q, part, rq_data_dir(req)); hd_struct_put(part); part_stat_unlock(); } } void blk_account_io_start(struct request *rq, bool 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(rq->q, cpu, part); part_inc_in_flight(rq->q, part, rw); rq->part = part; } part_stat_unlock(); } /* * Steal bios from a request and add them to a bio list. * The request must not have been partially completed before. */ void blk_steal_bios(struct bio_list *list, struct request *rq) { if (rq->bio) { if (list->tail) list->tail->bi_next = rq->bio; else list->head = rq->bio; list->tail = rq->biotail; rq->bio = NULL; rq->biotail = NULL; } rq->__data_len = 0; } EXPORT_SYMBOL_GPL(blk_steal_bios); /** * blk_update_request - Special helper function for request stacking drivers * @req: the request being processed * @error: block status code * @nr_bytes: number of bytes to complete @req * * Description: * Ends I/O on a number of bytes attached to @req, but doesn't complete * the request structure even if @req doesn't have leftover. * If @req has leftover, sets it up for the next range of segments. * * This special helper function is only for request stacking drivers * (e.g. request-based dm) so that they can handle partial completion. * Actual device drivers should use blk_end_request instead. * * Passing the result of blk_rq_bytes() as @nr_bytes guarantees * %false return from this function. * * Note: * The RQF_SPECIAL_PAYLOAD flag is ignored on purpose in both * blk_rq_bytes() and in blk_update_request(). * * Return: * %false - this request doesn't have any more data * %true - this request has more data **/ bool blk_update_request(struct request *req, blk_status_t error, unsigned int nr_bytes) { int total_bytes; trace_block_rq_complete(req, blk_status_to_errno(error), nr_bytes); if (!req->bio) return false; if (unlikely(error && !blk_rq_is_passthrough(req) && !(req->rq_flags & RQF_QUIET))) print_req_error(req, error); blk_account_io_completion(req, nr_bytes); total_bytes = 0; while (req->bio) { struct bio *bio = req->bio; unsigned bio_bytes = min(bio->bi_iter.bi_size, nr_bytes); if (bio_bytes == bio->bi_iter.bi_size) req->bio = bio->bi_next; /* Completion has already been traced */ bio_clear_flag(bio, BIO_TRACE_COMPLETION); req_bio_endio(req, bio, bio_bytes, error); total_bytes += bio_bytes; nr_bytes -= bio_bytes; if (!nr_bytes) break; } /* * completely done */ if (!req->bio) { /* * Reset counters so that the request stacking driver * can find how many bytes remain in the request * later. */ req->__data_len = 0; return false; } req->__data_len -= total_bytes; /* update sector only for requests with clear definition of sector */ if (!blk_rq_is_passthrough(req)) req->__sector += total_bytes >> 9; /* mixed attributes always follow the first bio */ if (req->rq_flags & RQF_MIXED_MERGE) { req->cmd_flags &= ~REQ_FAILFAST_MASK; req->cmd_flags |= req->bio->bi_opf & REQ_FAILFAST_MASK; } if (!(req->rq_flags & RQF_SPECIAL_PAYLOAD)) { /* * If total number of sectors is less than the first segment * size, something has gone terribly wrong. */ if (blk_rq_bytes(req) < blk_rq_cur_bytes(req)) { blk_dump_rq_flags(req, "request botched"); req->__data_len = blk_rq_cur_bytes(req); } /* recalculate the number of segments */ blk_recalc_rq_segments(req); } return true; } EXPORT_SYMBOL_GPL(blk_update_request); void blk_rq_bio_prep(struct request_queue *q, struct request *rq, struct bio *bio) { if (bio_has_data(bio)) rq->nr_phys_segments = bio_phys_segments(q, bio); else if (bio_op(bio) == REQ_OP_DISCARD) rq->nr_phys_segments = 1; rq->__data_len = bio->bi_iter.bi_size; rq->bio = rq->biotail = bio; if (bio->bi_disk) rq->rq_disk = bio->bi_disk; } #if ARCH_IMPLEMENTS_FLUSH_DCACHE_PAGE /** * rq_flush_dcache_pages - Helper function to flush all pages in a request * @rq: the request to be flushed * * Description: * Flush all pages in @rq. */ void rq_flush_dcache_pages(struct request *rq) { struct req_iterator iter; struct bio_vec bvec; rq_for_each_segment(bvec, rq, iter) flush_dcache_page(bvec.bv_page); } EXPORT_SYMBOL_GPL(rq_flush_dcache_pages); #endif /** * blk_lld_busy - Check if underlying low-level drivers of a device are busy * @q : the queue of the device being checked * * Description: * Check if underlying low-level drivers of a device are busy. * If the drivers want to export their busy state, they must set own * exporting function using blk_queue_lld_busy() first. * * Basically, this function is used only by request stacking drivers * to stop dispatching requests to underlying devices when underlying * devices are busy. This behavior helps more I/O merging on the queue * of the request stacking driver and prevents I/O throughput regression * on burst I/O load. * * Return: * 0 - Not busy (The request stacking driver should dispatch request) * 1 - Busy (The request stacking driver should stop dispatching request) */ int blk_lld_busy(struct request_queue *q) { if (queue_is_mq(q) && q->mq_ops->busy) return q->mq_ops->busy(q); return 0; } EXPORT_SYMBOL_GPL(blk_lld_busy); /** * blk_rq_unprep_clone - Helper function to free all bios in a cloned request * @rq: the clone request to be cleaned up * * Description: * Free all bios in @rq for a cloned request. */ void blk_rq_unprep_clone(struct request *rq) { struct bio *bio; while ((bio = rq->bio) != NULL) { rq->bio = bio->bi_next; bio_put(bio); } } EXPORT_SYMBOL_GPL(blk_rq_unprep_clone); /* * Copy attributes of the original request to the clone request. * The actual data parts (e.g. ->cmd, ->sense) are not copied. */ static void __blk_rq_prep_clone(struct request *dst, struct request *src) { dst->__sector = blk_rq_pos(src); dst->__data_len = blk_rq_bytes(src); if (src->rq_flags & RQF_SPECIAL_PAYLOAD) { dst->rq_flags |= RQF_SPECIAL_PAYLOAD; dst->special_vec = src->special_vec; } dst->nr_phys_segments = src->nr_phys_segments; dst->ioprio = src->ioprio; dst->extra_len = src->extra_len; } /** * blk_rq_prep_clone - Helper function to setup clone request * @rq: the request to be setup * @rq_src: original request to be cloned * @bs: bio_set that bios for clone are allocated from * @gfp_mask: memory allocation mask for bio * @bio_ctr: setup function to be called for each clone bio. * Returns %0 for success, non %0 for failure. * @data: private data to be passed to @bio_ctr * * Description: * Clones bios in @rq_src to @rq, and copies attributes of @rq_src to @rq. * The actual data parts of @rq_src (e.g. ->cmd, ->sense) * are not copied, and copying such parts is the caller's responsibility. * Also, pages which the original bios are pointing to are not copied * and the cloned bios just point same pages. * So cloned bios must be completed before original bios, which means * the caller must complete @rq before @rq_src. */ int blk_rq_prep_clone(struct request *rq, struct request *rq_src, struct bio_set *bs, gfp_t gfp_mask, int (*bio_ctr)(struct bio *, struct bio *, void *), void *data) { struct bio *bio, *bio_src; if (!bs) bs = &fs_bio_set; __rq_for_each_bio(bio_src, rq_src) { bio = bio_clone_fast(bio_src, gfp_mask, bs); if (!bio) goto free_and_out; if (bio_ctr && bio_ctr(bio, bio_src, data)) goto free_and_out; if (rq->bio) { rq->biotail->bi_next = bio; rq->biotail = bio; } else rq->bio = rq->biotail = bio; } __blk_rq_prep_clone(rq, rq_src); return 0; free_and_out: if (bio) bio_put(bio); blk_rq_unprep_clone(rq); return -ENOMEM; } EXPORT_SYMBOL_GPL(blk_rq_prep_clone); int kblockd_schedule_work(struct work_struct *work) { return queue_work(kblockd_workqueue, work); } EXPORT_SYMBOL(kblockd_schedule_work); int kblockd_schedule_work_on(int cpu, struct work_struct *work) { return queue_work_on(cpu, kblockd_workqueue, work); } EXPORT_SYMBOL(kblockd_schedule_work_on); int kblockd_mod_delayed_work_on(int cpu, struct delayed_work *dwork, unsigned long delay) { return mod_delayed_work_on(cpu, kblockd_workqueue, dwork, delay); } EXPORT_SYMBOL(kblockd_mod_delayed_work_on); /** * blk_start_plug - initialize blk_plug and track it inside the task_struct * @plug: The &struct blk_plug that needs to be initialized * * Description: * Tracking blk_plug inside the task_struct will help with auto-flushing the * pending I/O should the task end up blocking between blk_start_plug() and * blk_finish_plug(). This is important from a performance perspective, but * also ensures that we don't deadlock. For instance, if the task is blocking * for a memory allocation, memory reclaim could end up wanting to free a * page belonging to that request that is currently residing in our private * plug. By flushing the pending I/O when the process goes to sleep, we avoid * this kind of deadlock. */ void blk_start_plug(struct blk_plug *plug) { struct task_struct *tsk = current; /* * If this is a nested plug, don't actually assign it. */ if (tsk->plug) return; INIT_LIST_HEAD(&plug->mq_list); INIT_LIST_HEAD(&plug->cb_list); plug->rq_count = 0; /* * Store ordering should not be needed here, since a potential * preempt will imply a full memory barrier */ tsk->plug = plug; } EXPORT_SYMBOL(blk_start_plug); static void flush_plug_callbacks(struct blk_plug *plug, bool from_schedule) { LIST_HEAD(callbacks); while (!list_empty(&plug->cb_list)) { list_splice_init(&plug->cb_list, &callbacks); while (!list_empty(&callbacks)) { struct blk_plug_cb *cb = list_first_entry(&callbacks, struct blk_plug_cb, list); list_del(&cb->list); cb->callback(cb, from_schedule); } } } struct blk_plug_cb *blk_check_plugged(blk_plug_cb_fn unplug, void *data, int size) { struct blk_plug *plug = current->plug; struct blk_plug_cb *cb; if (!plug) return NULL; list_for_each_entry(cb, &plug->cb_list, list) if (cb->callback == unplug && cb->data == data) return cb; /* Not currently on the callback list */ BUG_ON(size < sizeof(*cb)); cb = kzalloc(size, GFP_ATOMIC); if (cb) { cb->data = data; cb->callback = unplug; list_add(&cb->list, &plug->cb_list); } return cb; } EXPORT_SYMBOL(blk_check_plugged); void blk_flush_plug_list(struct blk_plug *plug, bool from_schedule) { flush_plug_callbacks(plug, from_schedule); if (!list_empty(&plug->mq_list)) blk_mq_flush_plug_list(plug, from_schedule); } void blk_finish_plug(struct blk_plug *plug) { if (plug != current->plug) return; blk_flush_plug_list(plug, false); current->plug = NULL; } EXPORT_SYMBOL(blk_finish_plug); int __init blk_dev_init(void) { BUILD_BUG_ON(REQ_OP_LAST >= (1 << REQ_OP_BITS)); BUILD_BUG_ON(REQ_OP_BITS + REQ_FLAG_BITS > 8 * FIELD_SIZEOF(struct request, cmd_flags)); BUILD_BUG_ON(REQ_OP_BITS + REQ_FLAG_BITS > 8 * FIELD_SIZEOF(struct bio, bi_opf)); /* used for unplugging and affects IO latency/throughput - HIGHPRI */ kblockd_workqueue = alloc_workqueue("kblockd", WQ_MEM_RECLAIM | WQ_HIGHPRI, 0); if (!kblockd_workqueue) panic("Failed to create kblockd\n"); blk_requestq_cachep = kmem_cache_create("request_queue", sizeof(struct request_queue), 0, SLAB_PANIC, NULL); #ifdef CONFIG_DEBUG_FS blk_debugfs_root = debugfs_create_dir("block", NULL); #endif return 0; }