1 files changed, 141 insertions, 0 deletions
diff --git a/include/linux/wbt.h b/include/linux/wbt.h
new file mode 100644
index 000000000..68ba75e3a
--- /dev/null
+++ b/include/linux/wbt.h
@@ -0,0 +1,141 @@
+#ifndef WB_THROTTLE_H
+#define WB_THROTTLE_H
+
+#include <linux/atomic.h>
+#include <linux/wait.h>
+#include <linux/timer.h>
+#include <linux/ktime.h>
+
+enum wbt_flags {
+	WBT_TRACKED		= 1,	/* write, tracked for throttling */
+	WBT_READ		= 2,	/* read */
+	WBT_KSWAPD		= 4,	/* write, from kswapd */
+
+	WBT_NR_BITS		= 3,	/* number of bits */
+};
+
+enum {
+	/*
+	 * Set aside 3 bits for state, rest is a time stamp
+	 */
+	ISSUE_STAT_SHIFT	= 64 - WBT_NR_BITS,
+	ISSUE_STAT_MASK 	= ~((1ULL << ISSUE_STAT_SHIFT) - 1),
+	ISSUE_STAT_TIME_MASK	= ~ISSUE_STAT_MASK,
+
+	WBT_NUM_RWQ		= 2,
+};
+
+struct wb_issue_stat {
+	u64 time;
+};
+
+static inline void wbt_issue_stat_set_time(struct wb_issue_stat *stat)
+{
+	stat->time = (stat->time & ISSUE_STAT_MASK) |
+			(ktime_to_ns(ktime_get()) & ISSUE_STAT_TIME_MASK);
+}
+
+static inline u64 wbt_issue_stat_get_time(struct wb_issue_stat *stat)
+{
+	return stat->time & ISSUE_STAT_TIME_MASK;
+}
+
+static inline void wbt_clear_state(struct wb_issue_stat *stat)
+{
+	stat->time &= ISSUE_STAT_TIME_MASK;
+}
+
+static inline enum wbt_flags wbt_stat_to_mask(struct wb_issue_stat *stat)
+{
+	return (stat->time & ISSUE_STAT_MASK) >> ISSUE_STAT_SHIFT;
+}
+
+static inline void wbt_track(struct wb_issue_stat *stat, enum wbt_flags wb_acct)
+{
+	stat->time |= ((u64) wb_acct) << ISSUE_STAT_SHIFT;
+}
+
+static inline bool wbt_is_tracked(struct wb_issue_stat *stat)
+{
+	return (stat->time >> ISSUE_STAT_SHIFT) & WBT_TRACKED;
+}
+
+static inline bool wbt_is_read(struct wb_issue_stat *stat)
+{
+	return (stat->time >> ISSUE_STAT_SHIFT) & WBT_READ;
+}
+
+struct wb_stat_ops {
+	void (*get)(void *, struct blk_rq_stat *);
+	bool (*is_current)(struct blk_rq_stat *);
+	void (*clear)(void *);
+};
+
+struct rq_wait {
+	wait_queue_head_t wait;
+	atomic_t inflight;
+};
+
+struct rq_wb {
+	/*
+	 * Settings that govern how we throttle
+	 */
+	unsigned int wb_background;		/* background writeback */
+	unsigned int wb_normal;			/* normal writeback */
+	unsigned int wb_max;			/* max throughput writeback */
+	int scale_step;
+	bool scaled_max;
+
+	/*
+	 * Number of consecutive periods where we don't have enough
+	 * information to make a firm scale up/down decision.
+	 */
+	unsigned int unknown_cnt;
+
+	u64 win_nsec;				/* default window size */
+	u64 cur_win_nsec;			/* current window size */
+
+	struct timer_list window_timer;
+
+	s64 sync_issue;
+	void *sync_cookie;
+
+	unsigned int wc;
+	unsigned int queue_depth;
+
+	unsigned long last_issue;		/* last non-throttled issue */
+	unsigned long last_comp;		/* last non-throttled comp */
+	unsigned long min_lat_nsec;
+	struct backing_dev_info *bdi;
+	struct rq_wait rq_wait[WBT_NUM_RWQ];
+
+	struct wb_stat_ops *stat_ops;
+	void *ops_data;
+};
+
+static inline unsigned int wbt_inflight(struct rq_wb *rwb)
+{
+	unsigned int i, ret = 0;
+
+	for (i = 0; i < WBT_NUM_RWQ; i++)
+		ret += atomic_read(&rwb->rq_wait[i].inflight);
+
+	return ret;
+}
+
+struct backing_dev_info;
+
+void __wbt_done(struct rq_wb *, enum wbt_flags);
+void wbt_done(struct rq_wb *, struct wb_issue_stat *);
+enum wbt_flags wbt_wait(struct rq_wb *, unsigned int, spinlock_t *);
+struct rq_wb *wbt_init(struct backing_dev_info *, struct wb_stat_ops *, void *);
+void wbt_exit(struct rq_wb *);
+void wbt_update_limits(struct rq_wb *);
+void wbt_requeue(struct rq_wb *, struct wb_issue_stat *);
+void wbt_issue(struct rq_wb *, struct wb_issue_stat *);
+void wbt_disable(struct rq_wb *);
+
+void wbt_set_queue_depth(struct rq_wb *, unsigned int);
+void wbt_set_write_cache(struct rq_wb *, bool);
+
+#endif