1 files changed, 0 insertions, 703 deletions

diff --git a/lib/wbt.c b/lib/wbt.c
deleted file mode 100644
index 257c7b099..000000000
--- a/lib/wbt.c
+++ /dev/null
@@ -1,703 +0,0 @@
-/*
- * buffered writeback throttling. loosely based on CoDel. We can't drop
- * packets for IO scheduling, so the logic is something like this:
- *
- * - Monitor latencies in a defined window of time.
- * - If the minimum latency in the above window exceeds some target, increment
- *   scaling step and scale down queue depth by a factor of 2x. The monitoring
- *   window is then shrunk to 100 / sqrt(scaling step + 1).
- * - For any window where we don't have solid data on what the latencies
- *   look like, retain status quo.
- * - If latencies look good, decrement scaling step.
- * - If we're only doing writes, allow the scaling step to go negative. This
- *   will temporarily boost write performance, snapping back to a stable
- *   scaling step of 0 if reads show up or the heavy writers finish. Unlike
- *   positive scaling steps where we shrink the monitoring window, a negative
- *   scaling step retains the default step==0 window size.
- *
- * Copyright (C) 2016 Jens Axboe
- *
- */
-#include <linux/kernel.h>
-#include <linux/blk_types.h>
-#include <linux/slab.h>
-#include <linux/backing-dev.h>
-#include <linux/wbt.h>
-#include <linux/swap.h>
-
-#define CREATE_TRACE_POINTS
-#include <trace/events/wbt.h>
-
-enum {
-	/*
-	 * Default setting, we'll scale up (to 75% of QD max) or down (min 1)
-	 * from here depending on device stats
-	 */
-	RWB_DEF_DEPTH	= 16,
-
-	/*
-	 * 100msec window
-	 */
-	RWB_WINDOW_NSEC		= 100 * 1000 * 1000ULL,
-
-	/*
-	 * Disregard stats, if we don't meet this minimum
-	 */
-	RWB_MIN_WRITE_SAMPLES	= 3,
-
-	/*
-	 * If we have this number of consecutive windows with not enough
-	 * information to scale up or down, scale up.
-	 */
-	RWB_UNKNOWN_BUMP	= 5,
-};
-
-static inline bool rwb_enabled(struct rq_wb *rwb)
-{
-	return rwb && rwb->wb_normal != 0;
-}
-
-/*
- * 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, int below)
-{
-	int cur = atomic_read(v);
-
-	for (;;) {
-		int old;
-
-		if (cur >= below)
-			return false;
-		old = atomic_cmpxchg(v, cur, cur + 1);
-		if (old == cur)
-			break;
-		cur = old;
-	}
-
-	return true;
-}
-
-static void wb_timestamp(struct rq_wb *rwb, unsigned long *var)
-{
-	if (rwb_enabled(rwb)) {
-		const unsigned long cur = jiffies;
-
-		if (cur != *var)
-			*var = cur;
-	}
-}
-
-/*
- * If a task was rate throttled in balance_dirty_pages() within the last
- * second or so, use that to indicate a higher cleaning rate.
- */
-static bool wb_recent_wait(struct rq_wb *rwb)
-{
-	struct bdi_writeback *wb = &rwb->bdi->wb;
-
-	return time_before(jiffies, wb->dirty_sleep + HZ);
-}
-
-static inline struct rq_wait *get_rq_wait(struct rq_wb *rwb, bool is_kswapd)
-{
-	return &rwb->rq_wait[is_kswapd];
-}
-
-static void rwb_wake_all(struct rq_wb *rwb)
-{
-	int i;
-
-	for (i = 0; i < WBT_NUM_RWQ; i++) {
-		struct rq_wait *rqw = &rwb->rq_wait[i];
-
-		if (waitqueue_active(&rqw->wait))
-			wake_up_all(&rqw->wait);
-	}
-}
-
-void __wbt_done(struct rq_wb *rwb, enum wbt_flags wb_acct)
-{
-	struct rq_wait *rqw;
-	int inflight, limit;
-
-	if (!(wb_acct & WBT_TRACKED))
-		return;
-
-	rqw = get_rq_wait(rwb, wb_acct & WBT_KSWAPD);
-	inflight = atomic_dec_return(&rqw->inflight);
-
-	/*
-	 * wbt got disabled with IO in flight. Wake up any potential
-	 * waiters, we don't have to do more than that.
-	 */
-	if (unlikely(!rwb_enabled(rwb))) {
-		rwb_wake_all(rwb);
-		return;
-	}
-
-	/*
-	 * If the device does write back caching, drop further down
-	 * before we wake people up.
-	 */
-	if (rwb->wc && !wb_recent_wait(rwb))
-		limit = 0;
-	else
-		limit = rwb->wb_normal;
-
-	/*
-	 * Don't wake anyone up if we are above the normal limit.
-	 */
-	if (inflight && inflight >= limit)
-		return;
-
-	if (waitqueue_active(&rqw->wait)) {
-		int diff = limit - inflight;
-
-		if (!inflight || diff >= rwb->wb_background / 2)
-			wake_up(&rqw->wait);
-	}
-}
-
-/*
- * Called on completion of a request. Note that it's also called when
- * a request is merged, when the request gets freed.
- */
-void wbt_done(struct rq_wb *rwb, struct wb_issue_stat *stat)
-{
-	if (!rwb)
-		return;
-
-	if (!wbt_is_tracked(stat)) {
-		if (rwb->sync_cookie == stat) {
-			rwb->sync_issue = 0;
-			rwb->sync_cookie = NULL;
-		}
-
-		if (wbt_is_read(stat))
-			wb_timestamp(rwb, &rwb->last_comp);
-		wbt_clear_state(stat);
-	} else {
-		WARN_ON_ONCE(stat == rwb->sync_cookie);
-		__wbt_done(rwb, wbt_stat_to_mask(stat));
-		wbt_clear_state(stat);
-	}
-}
-
-/*
- * Return true, if we can't increase the depth further by scaling
- */
-static bool calc_wb_limits(struct rq_wb *rwb)
-{
-	unsigned int depth;
-	bool ret = false;
-
-	if (!rwb->min_lat_nsec) {
-		rwb->wb_max = rwb->wb_normal = rwb->wb_background = 0;
-		return 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 (rwb->queue_depth == 1) {
-		if (rwb->scale_step > 0)
-			rwb->wb_max = rwb->wb_normal = 1;
-		else {
-			rwb->wb_max = rwb->wb_normal = 2;
-			ret = true;
-		}
-		rwb->wb_background = 1;
-	} 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, RWB_DEF_DEPTH, rwb->queue_depth);
-		if (rwb->scale_step > 0)
-			depth = 1 + ((depth - 1) >> min(31, rwb->scale_step));
-		else if (rwb->scale_step < 0) {
-			unsigned int maxd = 3 * rwb->queue_depth / 4;
-
-			depth = 1 + ((depth - 1) << -rwb->scale_step);
-			if (depth > maxd) {
-				depth = maxd;
-				ret = true;
-			}
-		}
-
-		/*
-		 * Set our max/normal/bg queue depths based on how far
-		 * we have scaled down (->scale_step).
-		 */
-		rwb->wb_max = depth;
-		rwb->wb_normal = (rwb->wb_max + 1) / 2;
-		rwb->wb_background = (rwb->wb_max + 3) / 4;
-	}
-
-	return ret;
-}
-
-static bool inline stat_sample_valid(struct blk_rq_stat *stat)
-{
-	/*
-	 * We need at least one read sample, and a minimum of
-	 * RWB_MIN_WRITE_SAMPLES. We require some write samples to know
-	 * that it's writes impacting us, and not just some sole read on
-	 * a device that is in a lower power state.
-	 */
-	return stat[0].nr_samples >= 1 &&
-		stat[1].nr_samples >= RWB_MIN_WRITE_SAMPLES;
-}
-
-static u64 rwb_sync_issue_lat(struct rq_wb *rwb)
-{
-	u64 now, issue = ACCESS_ONCE(rwb->sync_issue);
-
-	if (!issue || !rwb->sync_cookie)
-		return 0;
-
-	now = ktime_to_ns(ktime_get());
-	return now - issue;
-}
-
-enum {
-	LAT_OK = 1,
-	LAT_UNKNOWN,
-	LAT_UNKNOWN_WRITES,
-	LAT_EXCEEDED,
-};
-
-static int __latency_exceeded(struct rq_wb *rwb, struct blk_rq_stat *stat)
-{
-	u64 thislat;
-
-	/*
-	 * If our stored sync issue exceeds the window size, or it
-	 * exceeds our min target AND we haven't logged any entries,
-	 * flag the latency as exceeded. wbt works off completion latencies,
-	 * but for a flooded device, a single sync IO can take a long time
-	 * to complete after being issued. If this time exceeds our
-	 * monitoring window AND we didn't see any other completions in that
-	 * window, then count that sync IO as a violation of the latency.
-	 */
-	thislat = rwb_sync_issue_lat(rwb);
-	if (thislat > rwb->cur_win_nsec ||
-	    (thislat > rwb->min_lat_nsec && !stat[0].nr_samples)) {
-		trace_wbt_lat(rwb->bdi, thislat);
-		return LAT_EXCEEDED;
-	}
-
-	/*
-	 * No read/write mix, if stat isn't valid
-	 */
-	if (!stat_sample_valid(stat)) {
-		/*
-		 * If we had writes in this stat window and the window is
-		 * current, we're only doing writes. If a task recently
-		 * waited or still has writes in flights, consider us doing
-		 * just writes as well.
-		 */
-		if ((stat[1].nr_samples && rwb->stat_ops->is_current(stat)) ||
-		    wb_recent_wait(rwb) || wbt_inflight(rwb))
-			return LAT_UNKNOWN_WRITES;
-		return LAT_UNKNOWN;
-	}
-
-	/*
-	 * If the 'min' latency exceeds our target, step down.
-	 */
-	if (stat[0].min > rwb->min_lat_nsec) {
-		trace_wbt_lat(rwb->bdi, stat[0].min);
-		trace_wbt_stat(rwb->bdi, stat);
-		return LAT_EXCEEDED;
-	}
-
-	if (rwb->scale_step)
-		trace_wbt_stat(rwb->bdi, stat);
-
-	return LAT_OK;
-}
-
-static int latency_exceeded(struct rq_wb *rwb)
-{
-	struct blk_rq_stat stat[2];
-
-	rwb->stat_ops->get(rwb->ops_data, stat);
-	return __latency_exceeded(rwb, stat);
-}
-
-static void rwb_trace_step(struct rq_wb *rwb, const char *msg)
-{
-	trace_wbt_step(rwb->bdi, msg, rwb->scale_step, rwb->cur_win_nsec,
-			rwb->wb_background, rwb->wb_normal, rwb->wb_max);
-}
-
-static void scale_up(struct rq_wb *rwb)
-{
-	/*
-	 * Hit max in previous round, stop here
-	 */
-	if (rwb->scaled_max)
-		return;
-
-	rwb->scale_step--;
-	rwb->unknown_cnt = 0;
-	rwb->stat_ops->clear(rwb->ops_data);
-
-	rwb->scaled_max = calc_wb_limits(rwb);
-
-	rwb_wake_all(rwb);
-
-	rwb_trace_step(rwb, "step up");
-}
-
-/*
- * Scale rwb down. If 'hard_throttle' is set, do it quicker, since we
- * had a latency violation.
- */
-static void scale_down(struct rq_wb *rwb, 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 (rwb->wb_max == 1)
-		return;
-
-	if (rwb->scale_step < 0 && hard_throttle)
-		rwb->scale_step = 0;
-	else
-		rwb->scale_step++;
-
-	rwb->scaled_max = false;
-	rwb->unknown_cnt = 0;
-	rwb->stat_ops->clear(rwb->ops_data);
-	calc_wb_limits(rwb);
-	rwb_trace_step(rwb, "step down");
-}
-
-static void rwb_arm_timer(struct rq_wb *rwb)
-{
-	unsigned long expires;
-
-	if (rwb->scale_step > 0) {
-		/*
-		 * We should speed this up, using some variant of a fast
-		 * integer inverse square root calculation. Since we only do
-		 * this for every window expiration, it's not a huge deal,
-		 * though.
-		 */
-		rwb->cur_win_nsec = div_u64(rwb->win_nsec << 4,
-					int_sqrt((rwb->scale_step + 1) << 8));
-	} else {
-		/*
-		 * For step < 0, we don't want to increase/decrease the
-		 * window size.
-		 */
-		rwb->cur_win_nsec = rwb->win_nsec;
-	}
-
-	expires = jiffies + nsecs_to_jiffies(rwb->cur_win_nsec);
-	mod_timer(&rwb->window_timer, expires);
-}
-
-static void wb_timer_fn(unsigned long data)
-{
-	struct rq_wb *rwb = (struct rq_wb *) data;
-	unsigned int inflight = wbt_inflight(rwb);
-	int status;
-
-	status = latency_exceeded(rwb);
-
-	trace_wbt_timer(rwb->bdi, status, rwb->scale_step, inflight);
-
-	/*
-	 * If we exceeded the latency target, step down. If we did not,
-	 * step one level up. If we don't know enough to say either exceeded
-	 * or ok, then don't do anything.
-	 */
-	switch (status) {
-	case LAT_EXCEEDED:
-		scale_down(rwb, true);
-		break;
-	case LAT_OK:
-		scale_up(rwb);
-		break;
-	case LAT_UNKNOWN_WRITES:
-		scale_up(rwb);
-		break;
-	case LAT_UNKNOWN:
-		if (++rwb->unknown_cnt < RWB_UNKNOWN_BUMP)
-			break;
-		/*
-		 * We get here for two reasons:
-		 *
-		 * 1) We previously scaled reduced depth, and we currently
-		 *    don't have a valid read/write sample. For that case,
-		 *    slowly return to center state (step == 0).
-		 * 2) We started a the center step, but don't have a valid
-		 *    read/write sample, but we do have writes going on.
-		 *    Allow step to go negative, to increase write perf.
-		 */
-		if (rwb->scale_step > 0)
-			scale_up(rwb);
-		else if (rwb->scale_step < 0)
-			scale_down(rwb, false);
-		break;
-	default:
-		break;
-	}
-
-	/*
-	 * Re-arm timer, if we have IO in flight
-	 */
-	if (rwb->scale_step || inflight)
-		rwb_arm_timer(rwb);
-}
-
-void wbt_update_limits(struct rq_wb *rwb)
-{
-	rwb->scale_step = 0;
-	rwb->scaled_max = false;
-	calc_wb_limits(rwb);
-
-	rwb_wake_all(rwb);
-}
-
-static bool close_io(struct rq_wb *rwb)
-{
-	const unsigned long now = jiffies;
-
-	return time_before(now, rwb->last_issue + HZ / 10) ||
-		time_before(now, rwb->last_comp + HZ / 10);
-}
-
-#define REQ_HIPRIO	(REQ_SYNC | REQ_META | REQ_PRIO)
-
-static inline unsigned int get_limit(struct rq_wb *rwb, unsigned long rw)
-{
-	unsigned int limit;
-
-	/*
-	 * At this point we know it's a buffered write. If this is
-	 * kswapd trying to free memory, or REQ_SYNC is set, set, then
-	 * it's WB_SYNC_ALL writeback, and we'll use the max limit for
-	 * that. If the write is marked as a background write, then use
-	 * the idle limit, or go to normal if we haven't had competing
-	 * IO for a bit.
-	 */
-	if ((rw & REQ_HIPRIO) || wb_recent_wait(rwb) || current_is_kswapd())
-		limit = rwb->wb_max;
-	else if ((rw & REQ_BG) || close_io(rwb)) {
-		/*
-		 * If less than 100ms since we completed unrelated IO,
-		 * limit us to half the depth for background writeback.
-		 */
-		limit = rwb->wb_background;
-	} else
-		limit = rwb->wb_normal;
-
-	return limit;
-}
-
-static inline bool may_queue(struct rq_wb *rwb, struct rq_wait *rqw,
-			     unsigned long rw)
-{
-	/*
-	 * inc it here even if disabled, since we'll dec it at completion.
-	 * this only happens if the task was sleeping in __wbt_wait(),
-	 * and someone turned it off at the same time.
-	 */
-	if (!rwb_enabled(rwb)) {
-		atomic_inc(&rqw->inflight);
-		return true;
-	}
-
-	return atomic_inc_below(&rqw->inflight, get_limit(rwb, rw));
-}
-
-/*
- * Block if we will exceed our limit, or if we are currently waiting for
- * the timer to kick off queuing again.
- */
-static void __wbt_wait(struct rq_wb *rwb, unsigned long rw, spinlock_t *lock)
-{
-	struct rq_wait *rqw = get_rq_wait(rwb, current_is_kswapd());
-	DEFINE_WAIT(wait);
-
-	if (may_queue(rwb, rqw, rw))
-		return;
-
-	do {
-		prepare_to_wait_exclusive(&rqw->wait, &wait,
-						TASK_UNINTERRUPTIBLE);
-
-		if (may_queue(rwb, rqw, rw))
-			break;
-
-		if (lock)
-			spin_unlock_irq(lock);
-
-		io_schedule();
-
-		if (lock)
-			spin_lock_irq(lock);
-	} while (1);
-
-	finish_wait(&rqw->wait, &wait);
-}
-
-static inline bool wbt_should_throttle(struct rq_wb *rwb, unsigned int rw)
-{
-	const int op = rw >> BIO_OP_SHIFT;
-
-	/*
-	 * If not a WRITE (or a discard), do nothing
-	 */
-	if (!(op == REQ_OP_WRITE || op == REQ_OP_DISCARD))
-		return false;
-
-	/*
-	 * Don't throttle WRITE_ODIRECT
-	 */
-	if ((rw & (REQ_SYNC | REQ_NOIDLE)) == REQ_SYNC)
-		return false;
-
-	return true;
-}
-
-/*
- * Returns true if the IO request should be accounted, false if not.
- * May sleep, if we have exceeded the writeback limits. Caller can pass
- * in an irq held spinlock, if it holds one when calling this function.
- * If we do sleep, we'll release and re-grab it.
- */
-unsigned int wbt_wait(struct rq_wb *rwb, unsigned int rw, spinlock_t *lock)
-{
-	unsigned int ret = 0;
-
-	if (!rwb_enabled(rwb))
-		return 0;
-
-	if ((rw >> BIO_OP_SHIFT) == REQ_OP_READ)
-		ret = WBT_READ;
-
-	if (!wbt_should_throttle(rwb, rw)) {
-		if (ret & WBT_READ)
-			wb_timestamp(rwb, &rwb->last_issue);
-		return ret;
-	}
-
-	__wbt_wait(rwb, rw, lock);
-
-	if (!timer_pending(&rwb->window_timer))
-		rwb_arm_timer(rwb);
-
-	if (current_is_kswapd())
-		ret |= WBT_KSWAPD;
-
-	return ret | WBT_TRACKED;
-}
-
-void wbt_issue(struct rq_wb *rwb, struct wb_issue_stat *stat)
-{
-	if (!rwb_enabled(rwb))
-		return;
-
-	wbt_issue_stat_set_time(stat);
-
-	/*
-	 * Track sync issue, in case it takes a long time to complete. Allows
-	 * us to react quicker, if a sync IO takes a long time to complete.
-	 * Note that this is just a hint. 'stat' can go away when the
-	 * request completes, so it's important we never dereference it. We
-	 * only use the address to compare with, which is why we store the
-	 * sync_issue time locally.
-	 */
-	if (wbt_is_read(stat) && !rwb->sync_issue) {
-		rwb->sync_cookie = stat;
-		rwb->sync_issue = wbt_issue_stat_get_time(stat);
-	}
-}
-
-void wbt_requeue(struct rq_wb *rwb, struct wb_issue_stat *stat)
-{
-	if (!rwb_enabled(rwb))
-		return;
-	if (stat == rwb->sync_cookie) {
-		rwb->sync_issue = 0;
-		rwb->sync_cookie = NULL;
-	}
-}
-
-void wbt_set_queue_depth(struct rq_wb *rwb, unsigned int depth)
-{
-	if (rwb) {
-		rwb->queue_depth = depth;
-		wbt_update_limits(rwb);
-	}
-}
-
-void wbt_set_write_cache(struct rq_wb *rwb, bool write_cache_on)
-{
-	if (rwb)
-		rwb->wc = write_cache_on;
-}
-
-void wbt_disable(struct rq_wb *rwb)
-{
-	if (rwb) {
-		del_timer_sync(&rwb->window_timer);
-		rwb->win_nsec = rwb->min_lat_nsec = 0;
-		wbt_update_limits(rwb);
-	}
-}
-EXPORT_SYMBOL_GPL(wbt_disable);
-
-struct rq_wb *wbt_init(struct backing_dev_info *bdi, struct wb_stat_ops *ops,
-		       void *ops_data)
-{
-	struct rq_wb *rwb;
-	int i;
-
-	if (!ops->get || !ops->is_current || !ops->clear)
-		return ERR_PTR(-EINVAL);
-
-	rwb = kzalloc(sizeof(*rwb), GFP_KERNEL);
-	if (!rwb)
-		return ERR_PTR(-ENOMEM);
-
-	for (i = 0; i < WBT_NUM_RWQ; i++) {
-		atomic_set(&rwb->rq_wait[i].inflight, 0);
-		init_waitqueue_head(&rwb->rq_wait[i].wait);
-	}
-
-	setup_timer(&rwb->window_timer, wb_timer_fn, (unsigned long) rwb);
-	rwb->wc = 1;
-	rwb->queue_depth = RWB_DEF_DEPTH;
-	rwb->last_comp = rwb->last_issue = jiffies;
-	rwb->bdi = bdi;
-	rwb->win_nsec = RWB_WINDOW_NSEC;
-	rwb->stat_ops = ops;
-	rwb->ops_data = ops_data;
-	wbt_update_limits(rwb);
-	return rwb;
-}
-
-void wbt_exit(struct rq_wb *rwb)
-{
-	if (rwb) {
-		del_timer_sync(&rwb->window_timer);
-		kfree(rwb);
-	}
-}