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authorAndré Fabian Silva Delgado <emulatorman@parabola.nu>2016-11-23 01:35:55 -0300
committerAndré Fabian Silva Delgado <emulatorman@parabola.nu>2016-11-23 01:35:55 -0300
commitd26f4ddb48463e2ff798859505af1cc520e75685 (patch)
treea1268534c14d9a7db61b4758ac72c33a3c7712bb /lib
parent3326a1803802aa4730d32304b003f50720996b31 (diff)
Linux-libre 4.8.10-gnupck-4.8.10-gnu
Diffstat (limited to 'lib')
-rw-r--r--lib/Kconfig3
-rw-r--r--lib/Makefile1
-rw-r--r--lib/genalloc.c3
-rw-r--r--lib/wbt.c703
4 files changed, 709 insertions, 1 deletions
diff --git a/lib/Kconfig b/lib/Kconfig
index d79909dc0..c585e4c40 100644
--- a/lib/Kconfig
+++ b/lib/Kconfig
@@ -550,4 +550,7 @@ config STACKDEPOT
bool
select STACKTRACE
+config WBT
+ bool
+
endmenu
diff --git a/lib/Makefile b/lib/Makefile
index b63a82375..5bd016bd3 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -177,6 +177,7 @@ obj-$(CONFIG_SG_SPLIT) += sg_split.o
obj-$(CONFIG_SG_POOL) += sg_pool.o
obj-$(CONFIG_STMP_DEVICE) += stmp_device.o
obj-$(CONFIG_IRQ_POLL) += irq_poll.o
+obj-$(CONFIG_WBT) += wbt.o
obj-$(CONFIG_STACKDEPOT) += stackdepot.o
KASAN_SANITIZE_stackdepot.o := n
diff --git a/lib/genalloc.c b/lib/genalloc.c
index 0a1139644..144fe6b1a 100644
--- a/lib/genalloc.c
+++ b/lib/genalloc.c
@@ -292,7 +292,7 @@ unsigned long gen_pool_alloc_algo(struct gen_pool *pool, size_t size,
struct gen_pool_chunk *chunk;
unsigned long addr = 0;
int order = pool->min_alloc_order;
- int nbits, start_bit = 0, end_bit, remain;
+ int nbits, start_bit, end_bit, remain;
#ifndef CONFIG_ARCH_HAVE_NMI_SAFE_CMPXCHG
BUG_ON(in_nmi());
@@ -307,6 +307,7 @@ unsigned long gen_pool_alloc_algo(struct gen_pool *pool, size_t size,
if (size > atomic_read(&chunk->avail))
continue;
+ start_bit = 0;
end_bit = chunk_size(chunk) >> order;
retry:
start_bit = algo(chunk->bits, end_bit, start_bit,
diff --git a/lib/wbt.c b/lib/wbt.c
new file mode 100644
index 000000000..257c7b099
--- /dev/null
+++ b/lib/wbt.c
@@ -0,0 +1,703 @@
+/*
+ * 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);
+ }
+}