dm cache: add io_tracker
A little class that keeps track of the volume of io that is in flight,
and the length of time that a device has been idle for.
FIXME: rather than jiffes, may be best to use ktime_t (to support faster
devices).
Signed-off-by: Joe Thornber <ejt@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
diff --git a/drivers/md/dm-cache-target.c b/drivers/md/dm-cache-target.c
index d598248..6f9bdd1 100644
--- a/drivers/md/dm-cache-target.c
+++ b/drivers/md/dm-cache-target.c
@@ -25,6 +25,79 @@
/*----------------------------------------------------------------*/
+#define IOT_RESOLUTION 4
+
+struct io_tracker {
+ spinlock_t lock;
+
+ /*
+ * Sectors of in-flight IO.
+ */
+ sector_t in_flight;
+
+ /*
+ * The time, in jiffies, when this device became idle (if it is
+ * indeed idle).
+ */
+ unsigned long idle_time;
+ unsigned long last_update_time;
+};
+
+static void iot_init(struct io_tracker *iot)
+{
+ spin_lock_init(&iot->lock);
+ iot->in_flight = 0ul;
+ iot->idle_time = 0ul;
+ iot->last_update_time = jiffies;
+}
+
+static bool __iot_idle_for(struct io_tracker *iot, unsigned long jifs)
+{
+ if (iot->in_flight)
+ return false;
+
+ return time_after(jiffies, iot->idle_time + jifs);
+}
+
+static bool iot_idle_for(struct io_tracker *iot, unsigned long jifs)
+{
+ bool r;
+ unsigned long flags;
+
+ spin_lock_irqsave(&iot->lock, flags);
+ r = __iot_idle_for(iot, jifs);
+ spin_unlock_irqrestore(&iot->lock, flags);
+
+ return r;
+}
+
+static void iot_io_begin(struct io_tracker *iot, sector_t len)
+{
+ unsigned long flags;
+
+ spin_lock_irqsave(&iot->lock, flags);
+ iot->in_flight += len;
+ spin_unlock_irqrestore(&iot->lock, flags);
+}
+
+static void __iot_io_end(struct io_tracker *iot, sector_t len)
+{
+ iot->in_flight -= len;
+ if (!iot->in_flight)
+ iot->idle_time = jiffies;
+}
+
+static void iot_io_end(struct io_tracker *iot, sector_t len)
+{
+ unsigned long flags;
+
+ spin_lock_irqsave(&iot->lock, flags);
+ __iot_io_end(iot, len);
+ spin_unlock_irqrestore(&iot->lock, flags);
+}
+
+/*----------------------------------------------------------------*/
+
/*
* Glossary:
*