diff --git a/drivers/md/dm-delay.c b/drivers/md/dm-delay.c index 7433525e598560..efd510984e2593 100644 --- a/drivers/md/dm-delay.c +++ b/drivers/md/dm-delay.c @@ -13,6 +13,7 @@ #include #include #include +#include #include @@ -31,6 +32,7 @@ struct delay_c { struct workqueue_struct *kdelayd_wq; struct work_struct flush_expired_bios; struct list_head delayed_bios; + struct task_struct *worker; atomic_t may_delay; struct delay_class read; @@ -66,6 +68,44 @@ static void queue_timeout(struct delay_c *dc, unsigned long expires) mutex_unlock(&dc->timer_lock); } +static inline bool delay_is_fast(struct delay_c *dc) +{ + return !!dc->worker; +} + +static void flush_delayed_bios_fast(struct delay_c *dc, bool flush_all) +{ + struct dm_delay_info *delayed, *next; + + mutex_lock(&delayed_bios_lock); + list_for_each_entry_safe(delayed, next, &dc->delayed_bios, list) { + if (flush_all || time_after_eq(jiffies, delayed->expires)) { + struct bio *bio = dm_bio_from_per_bio_data(delayed, + sizeof(struct dm_delay_info)); + list_del(&delayed->list); + dm_submit_bio_remap(bio, NULL); + delayed->class->ops--; + } + } + mutex_unlock(&delayed_bios_lock); +} + +static int flush_worker_fn(void *data) +{ + struct delay_c *dc = data; + + while (1) { + flush_delayed_bios_fast(dc, false); + if (unlikely(list_empty(&dc->delayed_bios))) { + set_current_state(TASK_INTERRUPTIBLE); + schedule(); + } else + cond_resched(); + } + + return 0; +} + static void flush_bios(struct bio *bio) { struct bio *n; @@ -78,7 +118,7 @@ static void flush_bios(struct bio *bio) } } -static struct bio *flush_delayed_bios(struct delay_c *dc, int flush_all) +static struct bio *flush_delayed_bios(struct delay_c *dc, bool flush_all) { struct dm_delay_info *delayed, *next; unsigned long next_expires = 0; @@ -115,7 +155,10 @@ static void flush_expired_bios(struct work_struct *work) struct delay_c *dc; dc = container_of(work, struct delay_c, flush_expired_bios); - flush_bios(flush_delayed_bios(dc, 0)); + if (delay_is_fast(dc)) + flush_delayed_bios_fast(dc, false); + else + flush_bios(flush_delayed_bios(dc, false)); } static void delay_dtr(struct dm_target *ti) @@ -131,8 +174,11 @@ static void delay_dtr(struct dm_target *ti) dm_put_device(ti, dc->write.dev); if (dc->flush.dev) dm_put_device(ti, dc->flush.dev); + if (dc->worker) + kthread_stop(dc->worker); - mutex_destroy(&dc->timer_lock); + if (!delay_is_fast(dc)) + mutex_destroy(&dc->timer_lock); kfree(dc); } @@ -175,6 +221,7 @@ static int delay_ctr(struct dm_target *ti, unsigned int argc, char **argv) { struct delay_c *dc; int ret; + unsigned int max_delay; if (argc != 3 && argc != 6 && argc != 9) { ti->error = "Requires exactly 3, 6 or 9 arguments"; @@ -188,16 +235,14 @@ static int delay_ctr(struct dm_target *ti, unsigned int argc, char **argv) } ti->private = dc; - timer_setup(&dc->delay_timer, handle_delayed_timer, 0); - INIT_WORK(&dc->flush_expired_bios, flush_expired_bios); INIT_LIST_HEAD(&dc->delayed_bios); - mutex_init(&dc->timer_lock); atomic_set(&dc->may_delay, 1); dc->argc = argc; ret = delay_class_ctr(ti, &dc->read, argv); if (ret) goto bad; + max_delay = dc->read.delay; if (argc == 3) { ret = delay_class_ctr(ti, &dc->write, argv); @@ -206,6 +251,8 @@ static int delay_ctr(struct dm_target *ti, unsigned int argc, char **argv) ret = delay_class_ctr(ti, &dc->flush, argv); if (ret) goto bad; + max_delay = max(max_delay, dc->write.delay); + max_delay = max(max_delay, dc->flush.delay); goto out; } @@ -216,19 +263,37 @@ static int delay_ctr(struct dm_target *ti, unsigned int argc, char **argv) ret = delay_class_ctr(ti, &dc->flush, argv + 3); if (ret) goto bad; + max_delay = max(max_delay, dc->flush.delay); goto out; } ret = delay_class_ctr(ti, &dc->flush, argv + 6); if (ret) goto bad; + max_delay = max(max_delay, dc->flush.delay); out: - dc->kdelayd_wq = alloc_workqueue("kdelayd", WQ_MEM_RECLAIM, 0); - if (!dc->kdelayd_wq) { - ret = -EINVAL; - DMERR("Couldn't start kdelayd"); - goto bad; + if (max_delay < 50) { + /* + * In case of small requested delays, use kthread instead of + * timers and workqueue to achieve better latency. + */ + dc->worker = kthread_create(&flush_worker_fn, dc, + "dm-delay-flush-worker"); + if (IS_ERR(dc->worker)) { + ret = PTR_ERR(dc->worker); + goto bad; + } + } else { + timer_setup(&dc->delay_timer, handle_delayed_timer, 0); + INIT_WORK(&dc->flush_expired_bios, flush_expired_bios); + mutex_init(&dc->timer_lock); + dc->kdelayd_wq = alloc_workqueue("kdelayd", WQ_MEM_RECLAIM, 0); + if (!dc->kdelayd_wq) { + ret = -EINVAL; + DMERR("Couldn't start kdelayd"); + goto bad; + } } ti->num_flush_bios = 1; @@ -260,7 +325,10 @@ static int delay_bio(struct delay_c *dc, struct delay_class *c, struct bio *bio) list_add_tail(&delayed->list, &dc->delayed_bios); mutex_unlock(&delayed_bios_lock); - queue_timeout(dc, expires); + if (delay_is_fast(dc)) + wake_up_process(dc->worker); + else + queue_timeout(dc, expires); return DM_MAPIO_SUBMITTED; } @@ -270,8 +338,13 @@ static void delay_presuspend(struct dm_target *ti) struct delay_c *dc = ti->private; atomic_set(&dc->may_delay, 0); - del_timer_sync(&dc->delay_timer); - flush_bios(flush_delayed_bios(dc, 1)); + + if (delay_is_fast(dc)) + flush_delayed_bios_fast(dc, true); + else { + del_timer_sync(&dc->delay_timer); + flush_bios(flush_delayed_bios(dc, true)); + } } static void delay_resume(struct dm_target *ti) @@ -356,7 +429,7 @@ static int delay_iterate_devices(struct dm_target *ti, static struct target_type delay_target = { .name = "delay", - .version = {1, 3, 0}, + .version = {1, 4, 0}, .features = DM_TARGET_PASSES_INTEGRITY, .module = THIS_MODULE, .ctr = delay_ctr,