dm raid1: use timer

This patch replaces the schedule() in the main kmirrord thread with a timer.
The schedule() could introduce an unwanted delay when work is ready to be
processed.

The code instead calls wake() when there's work to be done immediately, and
delayed_wake() after a failure to give a short delay before retrying.

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>

diff --git a/drivers/md/dm-raid1.c b/drivers/md/dm-raid1.c
index 6692e5a..3b9532f 100644 (file)
--- a/drivers/md/dm-raid1.c
+++ b/drivers/md/dm-raid1.c
@@ -154,6 +154,9 @@ struct mirror_set {
 
        struct workqueue_struct *kmirrord_wq;
        struct work_struct kmirrord_work;
+       struct timer_list timer;
+       unsigned long timer_pending;
+
        struct work_struct trigger_event;
 
        unsigned int nr_mirrors;
@@ -178,6 +181,25 @@ static void wake(struct mirror_set *ms)
        queue_work(ms->kmirrord_wq, &ms->kmirrord_work);
 }
 
+static void delayed_wake_fn(unsigned long data)
+{
+       struct mirror_set *ms = (struct mirror_set *) data;
+
+       clear_bit(0, &ms->timer_pending);
+       wake(ms);
+}
+
+static void delayed_wake(struct mirror_set *ms)
+{
+       if (test_and_set_bit(0, &ms->timer_pending))
+               return;
+
+       ms->timer.expires = jiffies + HZ / 5;
+       ms->timer.data = (unsigned long) ms;
+       ms->timer.function = delayed_wake_fn;
+       add_timer(&ms->timer);
+}
+
 /* FIXME move this */
 static void queue_bio(struct mirror_set *ms, struct bio *bio, int rw);
 
@@ -1180,6 +1202,7 @@ static void do_writes(struct mirror_set *ms, struct bio_list *writes)
                spin_lock_irq(&ms->lock);
                bio_list_merge(&ms->failures, &sync);
                spin_unlock_irq(&ms->lock);
+               wake(ms);
        } else
                while ((bio = bio_list_pop(&sync)))
                        do_write(ms, bio);
@@ -1239,7 +1262,7 @@ static void do_failures(struct mirror_set *ms, struct bio_list *failures)
        bio_list_merge(&ms->failures, failures);
        spin_unlock_irq(&ms->lock);
 
-       wake(ms);
+       delayed_wake(ms);
 }
 
 static void trigger_event(struct work_struct *work)
@@ -1253,7 +1276,7 @@ static void trigger_event(struct work_struct *work)
 /*-----------------------------------------------------------------
  * kmirrord
  *---------------------------------------------------------------*/
-static int _do_mirror(struct work_struct *work)
+static void do_mirror(struct work_struct *work)
 {
        struct mirror_set *ms =container_of(work, struct mirror_set,
                                            kmirrord_work);
@@ -1274,24 +1297,6 @@ static int _do_mirror(struct work_struct *work)
        do_reads(ms, &reads);
        do_writes(ms, &writes);
        do_failures(ms, &failures);
-
-       return (ms->failures.head) ? 1 : 0;
-}
-
-static void do_mirror(struct work_struct *work)
-{
-       /*
-        * If _do_mirror returns 1, we give it
-        * another shot.  This helps for cases like
-        * 'suspend' where we call flush_workqueue
-        * and expect all work to be finished.  If
-        * a failure happens during a suspend, we
-        * couldn't issue a 'wake' because it would
-        * not be honored.  Therefore, we return '1'
-        * from _do_mirror, and retry here.
-        */
-       while (_do_mirror(work))
-               schedule();
 }
 
 
@@ -1545,6 +1550,8 @@ static int mirror_ctr(struct dm_target *ti, unsigned int argc, char **argv)
                goto err_free_context;
        }
        INIT_WORK(&ms->kmirrord_work, do_mirror);
+       init_timer(&ms->timer);
+       ms->timer_pending = 0;
        INIT_WORK(&ms->trigger_event, trigger_event);
 
        r = parse_features(ms, argc, argv, &args_used);
@@ -1587,6 +1594,7 @@ static void mirror_dtr(struct dm_target *ti)
 {
        struct mirror_set *ms = (struct mirror_set *) ti->private;
 
+       del_timer_sync(&ms->timer);
        flush_workqueue(ms->kmirrord_wq);
        dm_kcopyd_client_destroy(ms->kcopyd_client);
        destroy_workqueue(ms->kmirrord_wq);