1 files changed, 355 insertions, 0 deletions
diff --git a/block/blk-rq-qos.c b/block/blk-rq-qos.c
new file mode 100644
index 000000000..dd7310c94
--- /dev/null
+++ b/block/blk-rq-qos.c
@@ -0,0 +1,355 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include "blk-rq-qos.h"
+
+/*
+ * Increment 'v', if 'v' is below 'below'. Returns true if we succeeded,
+ * false if 'v' + 1 would be bigger than 'below'.
+ */
+static bool atomic_inc_below(atomic_t *v, unsigned int below)
+{
+	unsigned int cur = atomic_read(v);
+
+	do {
+		if (cur >= below)
+			return false;
+	} while (!atomic_try_cmpxchg(v, &cur, cur + 1));
+
+	return true;
+}
+
+bool rq_wait_inc_below(struct rq_wait *rq_wait, unsigned int limit)
+{
+	return atomic_inc_below(&rq_wait->inflight, limit);
+}
+
+void __rq_qos_cleanup(struct rq_qos *rqos, struct bio *bio)
+{
+	do {
+		if (rqos->ops->cleanup)
+			rqos->ops->cleanup(rqos, bio);
+		rqos = rqos->next;
+	} while (rqos);
+}
+
+void __rq_qos_done(struct rq_qos *rqos, struct request *rq)
+{
+	do {
+		if (rqos->ops->done)
+			rqos->ops->done(rqos, rq);
+		rqos = rqos->next;
+	} while (rqos);
+}
+
+void __rq_qos_issue(struct rq_qos *rqos, struct request *rq)
+{
+	do {
+		if (rqos->ops->issue)
+			rqos->ops->issue(rqos, rq);
+		rqos = rqos->next;
+	} while (rqos);
+}
+
+void __rq_qos_requeue(struct rq_qos *rqos, struct request *rq)
+{
+	do {
+		if (rqos->ops->requeue)
+			rqos->ops->requeue(rqos, rq);
+		rqos = rqos->next;
+	} while (rqos);
+}
+
+void __rq_qos_throttle(struct rq_qos *rqos, struct bio *bio)
+{
+	do {
+		if (rqos->ops->throttle)
+			rqos->ops->throttle(rqos, bio);
+		rqos = rqos->next;
+	} while (rqos);
+}
+
+void __rq_qos_track(struct rq_qos *rqos, struct request *rq, struct bio *bio)
+{
+	do {
+		if (rqos->ops->track)
+			rqos->ops->track(rqos, rq, bio);
+		rqos = rqos->next;
+	} while (rqos);
+}
+
+void __rq_qos_merge(struct rq_qos *rqos, struct request *rq, struct bio *bio)
+{
+	do {
+		if (rqos->ops->merge)
+			rqos->ops->merge(rqos, rq, bio);
+		rqos = rqos->next;
+	} while (rqos);
+}
+
+void __rq_qos_done_bio(struct rq_qos *rqos, struct bio *bio)
+{
+	do {
+		if (rqos->ops->done_bio)
+			rqos->ops->done_bio(rqos, bio);
+		rqos = rqos->next;
+	} while (rqos);
+}
+
+void __rq_qos_queue_depth_changed(struct rq_qos *rqos)
+{
+	do {
+		if (rqos->ops->queue_depth_changed)
+			rqos->ops->queue_depth_changed(rqos);
+		rqos = rqos->next;
+	} while (rqos);
+}
+
+/*
+ * Return true, if we can't increase the depth further by scaling
+ */
+bool rq_depth_calc_max_depth(struct rq_depth *rqd)
+{
+	unsigned int depth;
+	bool ret = false;
+
+	/*
+	 * For QD=1 devices, this is a special case. It's important for those
+	 * to have one request ready when one completes, so force a depth of
+	 * 2 for those devices. On the backend, it'll be a depth of 1 anyway,
+	 * since the device can't have more than that in flight. If we're
+	 * scaling down, then keep a setting of 1/1/1.
+	 */
+	if (rqd->queue_depth == 1) {
+		if (rqd->scale_step > 0)
+			rqd->max_depth = 1;
+		else {
+			rqd->max_depth = 2;
+			ret = true;
+		}
+	} else {
+		/*
+		 * scale_step == 0 is our default state. If we have suffered
+		 * latency spikes, step will be > 0, and we shrink the
+		 * allowed write depths. If step is < 0, we're only doing
+		 * writes, and we allow a temporarily higher depth to
+		 * increase performance.
+		 */
+		depth = min_t(unsigned int, rqd->default_depth,
+			      rqd->queue_depth);
+		if (rqd->scale_step > 0)
+			depth = 1 + ((depth - 1) >> min(31, rqd->scale_step));
+		else if (rqd->scale_step < 0) {
+			unsigned int maxd = 3 * rqd->queue_depth / 4;
+
+			depth = 1 + ((depth - 1) << -rqd->scale_step);
+			if (depth > maxd) {
+				depth = maxd;
+				ret = true;
+			}
+		}
+
+		rqd->max_depth = depth;
+	}
+
+	return ret;
+}
+
+/* Returns true on success and false if scaling up wasn't possible */
+bool rq_depth_scale_up(struct rq_depth *rqd)
+{
+	/*
+	 * Hit max in previous round, stop here
+	 */
+	if (rqd->scaled_max)
+		return false;
+
+	rqd->scale_step--;
+
+	rqd->scaled_max = rq_depth_calc_max_depth(rqd);
+	return true;
+}
+
+/*
+ * Scale rwb down. If 'hard_throttle' is set, do it quicker, since we
+ * had a latency violation. Returns true on success and returns false if
+ * scaling down wasn't possible.
+ */
+bool rq_depth_scale_down(struct rq_depth *rqd, bool hard_throttle)
+{
+	/*
+	 * Stop scaling down when we've hit the limit. This also prevents
+	 * ->scale_step from going to crazy values, if the device can't
+	 * keep up.
+	 */
+	if (rqd->max_depth == 1)
+		return false;
+
+	if (rqd->scale_step < 0 && hard_throttle)
+		rqd->scale_step = 0;
+	else
+		rqd->scale_step++;
+
+	rqd->scaled_max = false;
+	rq_depth_calc_max_depth(rqd);
+	return true;
+}
+
+struct rq_qos_wait_data {
+	struct wait_queue_entry wq;
+	struct task_struct *task;
+	struct rq_wait *rqw;
+	acquire_inflight_cb_t *cb;
+	void *private_data;
+	bool got_token;
+};
+
+static int rq_qos_wake_function(struct wait_queue_entry *curr,
+				unsigned int mode, int wake_flags, void *key)
+{
+	struct rq_qos_wait_data *data = container_of(curr,
+						     struct rq_qos_wait_data,
+						     wq);
+
+	/*
+	 * If we fail to get a budget, return -1 to interrupt the wake up loop
+	 * in __wake_up_common.
+	 */
+	if (!data->cb(data->rqw, data->private_data))
+		return -1;
+
+	data->got_token = true;
+	smp_wmb();
+	list_del_init(&curr->entry);
+	wake_up_process(data->task);
+	return 1;
+}
+
+/**
+ * rq_qos_wait - throttle on a rqw if we need to
+ * @rqw: rqw to throttle on
+ * @private_data: caller provided specific data
+ * @acquire_inflight_cb: inc the rqw->inflight counter if we can
+ * @cleanup_cb: the callback to cleanup in case we race with a waker
+ *
+ * This provides a uniform place for the rq_qos users to do their throttling.
+ * Since you can end up with a lot of things sleeping at once, this manages the
+ * waking up based on the resources available.  The acquire_inflight_cb should
+ * inc the rqw->inflight if we have the ability to do so, or return false if not
+ * and then we will sleep until the room becomes available.
+ *
+ * cleanup_cb is in case that we race with a waker and need to cleanup the
+ * inflight count accordingly.
+ */
+void rq_qos_wait(struct rq_wait *rqw, void *private_data,
+		 acquire_inflight_cb_t *acquire_inflight_cb,
+		 cleanup_cb_t *cleanup_cb)
+{
+	struct rq_qos_wait_data data = {
+		.wq = {
+			.func	= rq_qos_wake_function,
+			.entry	= LIST_HEAD_INIT(data.wq.entry),
+		},
+		.task = current,
+		.rqw = rqw,
+		.cb = acquire_inflight_cb,
+		.private_data = private_data,
+	};
+	bool has_sleeper;
+
+	has_sleeper = wq_has_sleeper(&rqw->wait);
+	if (!has_sleeper && acquire_inflight_cb(rqw, private_data))
+		return;
+
+	has_sleeper = !prepare_to_wait_exclusive(&rqw->wait, &data.wq,
+						 TASK_UNINTERRUPTIBLE);
+	do {
+		/* The memory barrier in set_task_state saves us here. */
+		if (data.got_token)
+			break;
+		if (!has_sleeper && acquire_inflight_cb(rqw, private_data)) {
+			finish_wait(&rqw->wait, &data.wq);
+
+			/*
+			 * We raced with rq_qos_wake_function() getting a token,
+			 * which means we now have two. Put our local token
+			 * and wake anyone else potentially waiting for one.
+			 */
+			smp_rmb();
+			if (data.got_token)
+				cleanup_cb(rqw, private_data);
+			break;
+		}
+		io_schedule();
+		has_sleeper = true;
+		set_current_state(TASK_UNINTERRUPTIBLE);
+	} while (1);
+	finish_wait(&rqw->wait, &data.wq);
+}
+
+void rq_qos_exit(struct request_queue *q)
+{
+	mutex_lock(&q->rq_qos_mutex);
+	while (q->rq_qos) {
+		struct rq_qos *rqos = q->rq_qos;
+		q->rq_qos = rqos->next;
+		rqos->ops->exit(rqos);
+	}
+	mutex_unlock(&q->rq_qos_mutex);
+}
+
+int rq_qos_add(struct rq_qos *rqos, struct gendisk *disk, enum rq_qos_id id,
+		const struct rq_qos_ops *ops)
+{
+	struct request_queue *q = disk->queue;
+
+	lockdep_assert_held(&q->rq_qos_mutex);
+
+	rqos->disk = disk;
+	rqos->id = id;
+	rqos->ops = ops;
+
+	/*
+	 * No IO can be in-flight when adding rqos, so freeze queue, which
+	 * is fine since we only support rq_qos for blk-mq queue.
+	 */
+	blk_mq_freeze_queue(q);
+
+	if (rq_qos_id(q, rqos->id))
+		goto ebusy;
+	rqos->next = q->rq_qos;
+	q->rq_qos = rqos;
+
+	blk_mq_unfreeze_queue(q);
+
+	if (rqos->ops->debugfs_attrs) {
+		mutex_lock(&q->debugfs_mutex);
+		blk_mq_debugfs_register_rqos(rqos);
+		mutex_unlock(&q->debugfs_mutex);
+	}
+
+	return 0;
+ebusy:
+	blk_mq_unfreeze_queue(q);
+	return -EBUSY;
+}
+
+void rq_qos_del(struct rq_qos *rqos)
+{
+	struct request_queue *q = rqos->disk->queue;
+	struct rq_qos **cur;
+
+	lockdep_assert_held(&q->rq_qos_mutex);
+
+	blk_mq_freeze_queue(q);
+	for (cur = &q->rq_qos; *cur; cur = &(*cur)->next) {
+		if (*cur == rqos) {
+			*cur = rqos->next;
+			break;
+		}
+	}
+	blk_mq_unfreeze_queue(q);
+
+	mutex_lock(&q->debugfs_mutex);
+	blk_mq_debugfs_unregister_rqos(rqos);
+	mutex_unlock(&q->debugfs_mutex);
+}