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-rw-r--r--block/blk-rq-qos.c304
1 files changed, 304 insertions, 0 deletions
diff --git a/block/blk-rq-qos.c b/block/blk-rq-qos.c
new file mode 100644
index 000000000..e83af7bc7
--- /dev/null
+++ b/block/blk-rq-qos.c
@@ -0,0 +1,304 @@
+// 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);
+
+ for (;;) {
+ unsigned int old;
+
+ if (cur >= below)
+ return false;
+ old = atomic_cmpxchg(v, cur, cur + 1);
+ if (old == cur)
+ break;
+ cur = old;
+ }
+
+ 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 wbt_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)
+{
+ blk_mq_debugfs_unregister_queue_rqos(q);
+
+ while (q->rq_qos) {
+ struct rq_qos *rqos = q->rq_qos;
+ q->rq_qos = rqos->next;
+ rqos->ops->exit(rqos);
+ }
+}