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path: root/drivers/md/dm-delay.c
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Diffstat (limited to 'drivers/md/dm-delay.c')
-rw-r--r--drivers/md/dm-delay.c102
1 files changed, 80 insertions, 22 deletions
diff --git a/drivers/md/dm-delay.c b/drivers/md/dm-delay.c
index 3726fae300..5eabdb06c6 100644
--- a/drivers/md/dm-delay.c
+++ b/drivers/md/dm-delay.c
@@ -13,6 +13,7 @@
#include <linux/blkdev.h>
#include <linux/bio.h>
#include <linux/slab.h>
+#include <linux/kthread.h>
#include <linux/device-mapper.h>
@@ -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;
bool may_delay;
struct delay_class read;
@@ -66,6 +68,11 @@ 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_bios(struct bio *bio)
{
struct bio *n;
@@ -78,36 +85,61 @@ static void flush_bios(struct bio *bio)
}
}
-static struct bio *flush_delayed_bios(struct delay_c *dc, int flush_all)
+static void flush_delayed_bios(struct delay_c *dc, bool flush_all)
{
struct dm_delay_info *delayed, *next;
+ struct bio_list flush_bio_list;
unsigned long next_expires = 0;
- unsigned long start_timer = 0;
- struct bio_list flush_bios = { };
+ bool start_timer = false;
+ bio_list_init(&flush_bio_list);
mutex_lock(&delayed_bios_lock);
list_for_each_entry_safe(delayed, next, &dc->delayed_bios, list) {
+ cond_resched();
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);
- bio_list_add(&flush_bios, bio);
+ bio_list_add(&flush_bio_list, bio);
delayed->class->ops--;
continue;
}
- if (!start_timer) {
- start_timer = 1;
- next_expires = delayed->expires;
- } else
- next_expires = min(next_expires, delayed->expires);
+ if (!delay_is_fast(dc)) {
+ if (!start_timer) {
+ start_timer = true;
+ next_expires = delayed->expires;
+ } else {
+ next_expires = min(next_expires, delayed->expires);
+ }
+ }
}
mutex_unlock(&delayed_bios_lock);
if (start_timer)
queue_timeout(dc, next_expires);
- return bio_list_get(&flush_bios);
+ flush_bios(bio_list_get(&flush_bio_list));
+}
+
+static int flush_worker_fn(void *data)
+{
+ struct delay_c *dc = data;
+
+ while (!kthread_should_stop()) {
+ flush_delayed_bios(dc, false);
+ mutex_lock(&delayed_bios_lock);
+ if (unlikely(list_empty(&dc->delayed_bios))) {
+ set_current_state(TASK_INTERRUPTIBLE);
+ mutex_unlock(&delayed_bios_lock);
+ schedule();
+ } else {
+ mutex_unlock(&delayed_bios_lock);
+ cond_resched();
+ }
+ }
+
+ return 0;
}
static void flush_expired_bios(struct work_struct *work)
@@ -115,7 +147,7 @@ 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));
+ flush_delayed_bios(dc, false);
}
static void delay_dtr(struct dm_target *ti)
@@ -131,6 +163,8 @@ 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);
@@ -175,6 +209,7 @@ 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";
@@ -188,8 +223,6 @@ 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);
dc->may_delay = true;
@@ -198,6 +231,7 @@ static int delay_ctr(struct dm_target *ti, unsigned int argc, char **argv)
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 +240,8 @@ 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 +252,37 @@ 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);
+ dc->worker = NULL;
+ goto bad;
+ }
+ } else {
+ timer_setup(&dc->delay_timer, handle_delayed_timer, 0);
+ INIT_WORK(&dc->flush_expired_bios, flush_expired_bios);
+ 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;
@@ -264,7 +318,10 @@ 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;
}
@@ -277,8 +334,9 @@ static void delay_presuspend(struct dm_target *ti)
dc->may_delay = false;
mutex_unlock(&delayed_bios_lock);
- del_timer_sync(&dc->delay_timer);
- flush_bios(flush_delayed_bios(dc, 1));
+ if (!delay_is_fast(dc))
+ del_timer_sync(&dc->delay_timer);
+ flush_delayed_bios(dc, true);
}
static void delay_resume(struct dm_target *ti)
@@ -363,7 +421,7 @@ out:
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,
generated by cgit v1.2.3 (git 2.39.1) at 2024-11-16 18:51:49 +0000