diff options
Diffstat (limited to 'block/blk-softirq.c')
| -rw-r--r-- | block/blk-softirq.c | 182 |
1 files changed, 182 insertions, 0 deletions
diff --git a/block/blk-softirq.c b/block/blk-softirq.c new file mode 100644 index 000000000..15c1f5e12 --- /dev/null +++ b/block/blk-softirq.c @@ -0,0 +1,182 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Functions related to softirq rq completions + */ +#include <linux/kernel.h> +#include <linux/module.h> +#include <linux/init.h> +#include <linux/bio.h> +#include <linux/blkdev.h> +#include <linux/interrupt.h> +#include <linux/cpu.h> +#include <linux/sched.h> +#include <linux/sched/topology.h> + +#include "blk.h" + +static DEFINE_PER_CPU(struct list_head, blk_cpu_done); + +/* + * Softirq action handler - move entries to local list and loop over them + * while passing them to the queue registered handler. + */ +static __latent_entropy void blk_done_softirq(struct softirq_action *h) +{ + struct list_head *cpu_list, local_list; + + local_irq_disable(); + cpu_list = this_cpu_ptr(&blk_cpu_done); + list_replace_init(cpu_list, &local_list); + local_irq_enable(); + + while (!list_empty(&local_list)) { + struct request *rq; + + rq = list_entry(local_list.next, struct request, ipi_list); + list_del_init(&rq->ipi_list); + rq->q->softirq_done_fn(rq); + } +} + +#ifdef CONFIG_SMP +static void trigger_softirq(void *data) +{ + struct request *rq = data; + unsigned long flags; + struct list_head *list; + + local_irq_save(flags); + list = this_cpu_ptr(&blk_cpu_done); + list_add_tail(&rq->ipi_list, list); + + if (list->next == &rq->ipi_list) + raise_softirq_irqoff(BLOCK_SOFTIRQ); + + local_irq_restore(flags); +} + +/* + * Setup and invoke a run of 'trigger_softirq' on the given cpu. + */ +static int raise_blk_irq(int cpu, struct request *rq) +{ + if (cpu_online(cpu)) { + call_single_data_t *data = &rq->csd; + + data->func = trigger_softirq; + data->info = rq; + data->flags = 0; + + smp_call_function_single_async(cpu, data); + return 0; + } + + return 1; +} +#else /* CONFIG_SMP */ +static int raise_blk_irq(int cpu, struct request *rq) +{ + return 1; +} +#endif + +static int blk_softirq_cpu_dead(unsigned int cpu) +{ + /* + * If a CPU goes away, splice its entries to the current CPU + * and trigger a run of the softirq + */ + local_irq_disable(); + list_splice_init(&per_cpu(blk_cpu_done, cpu), + this_cpu_ptr(&blk_cpu_done)); + raise_softirq_irqoff(BLOCK_SOFTIRQ); + local_irq_enable(); + + return 0; +} + +void __blk_complete_request(struct request *req) +{ + int ccpu, cpu; + struct request_queue *q = req->q; + unsigned long flags; + bool shared = false; + + BUG_ON(!q->softirq_done_fn); + + local_irq_save(flags); + cpu = smp_processor_id(); + + /* + * Select completion CPU + */ + if (req->cpu != -1) { + ccpu = req->cpu; + if (!test_bit(QUEUE_FLAG_SAME_FORCE, &q->queue_flags)) + shared = cpus_share_cache(cpu, ccpu); + } else + ccpu = cpu; + + /* + * If current CPU and requested CPU share a cache, run the softirq on + * the current CPU. One might concern this is just like + * QUEUE_FLAG_SAME_FORCE, but actually not. blk_complete_request() is + * running in interrupt handler, and currently I/O controller doesn't + * support multiple interrupts, so current CPU is unique actually. This + * avoids IPI sending from current CPU to the first CPU of a group. + */ + if (ccpu == cpu || shared) { + struct list_head *list; +do_local: + list = this_cpu_ptr(&blk_cpu_done); + list_add_tail(&req->ipi_list, list); + + /* + * if the list only contains our just added request, + * signal a raise of the softirq. If there are already + * entries there, someone already raised the irq but it + * hasn't run yet. + */ + if (list->next == &req->ipi_list) + raise_softirq_irqoff(BLOCK_SOFTIRQ); + } else if (raise_blk_irq(ccpu, req)) + goto do_local; + + local_irq_restore(flags); +} +EXPORT_SYMBOL(__blk_complete_request); + +/** + * blk_complete_request - end I/O on a request + * @req: the request being processed + * + * Description: + * Ends all I/O on a request. It does not handle partial completions, + * unless the driver actually implements this in its completion callback + * through requeueing. The actual completion happens out-of-order, + * through a softirq handler. The user must have registered a completion + * callback through blk_queue_softirq_done(). + **/ +void blk_complete_request(struct request *req) +{ + if (unlikely(blk_should_fake_timeout(req->q))) + return; + if (!blk_mark_rq_complete(req)) + __blk_complete_request(req); +} +EXPORT_SYMBOL(blk_complete_request); + +static __init int blk_softirq_init(void) +{ + int i; + + for_each_possible_cpu(i) + INIT_LIST_HEAD(&per_cpu(blk_cpu_done, i)); + + open_softirq(BLOCK_SOFTIRQ, blk_done_softirq); + cpuhp_setup_state_nocalls(CPUHP_BLOCK_SOFTIRQ_DEAD, + "block/softirq:dead", NULL, + blk_softirq_cpu_dead); + return 0; +} +subsys_initcall(blk_softirq_init); |