// SPDX-License-Identifier: GPL-2.0
/*
* 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/swap.h>
#include "blk-stat.h"
#include "blk-wbt.h"
#include "blk-rq-qos.h"
#include "elevator.h"
#include "blk.h"
#define CREATE_TRACE_POINTS
#include <trace/events/wbt.h>
enum wbt_flags {
WBT_TRACKED = 1, /* write, tracked for throttling */
WBT_READ = 2, /* read */
WBT_SWAP = 4, /* write, from swap_writepage() */
WBT_DISCARD = 8, /* discard */
WBT_NR_BITS = 4, /* number of bits */
};
enum {
WBT_RWQ_BG = 0,
WBT_RWQ_SWAP,
WBT_RWQ_DISCARD,
WBT_NUM_RWQ,
};
/*
* If current state is WBT_STATE_ON/OFF_DEFAULT, it can be covered to any other
* state, if current state is WBT_STATE_ON/OFF_MANUAL, it can only be covered
* to WBT_STATE_OFF/ON_MANUAL.
*/
enum {
WBT_STATE_ON_DEFAULT = 1, /* on by default */
WBT_STATE_ON_MANUAL = 2, /* on manually by sysfs */
WBT_STATE_OFF_DEFAULT = 3, /* off by default */
WBT_STATE_OFF_MANUAL = 4, /* off manually by sysfs */
};
struct rq_wb {
/*
* Settings that govern how we throttle
*/
unsigned int wb_background; /* background writeback */
unsigned int wb_normal; /* normal writeback */
short enable_state; /* WBT_STATE_* */
/*
* 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 blk_stat_callback *cb;
u64 sync_issue;
void *sync_cookie;
unsigned long last_issue; /* last non-throttled issue */
unsigned long last_comp; /* last non-throttled comp */
unsigned long min_lat_nsec;
struct rq_qos rqos;
struct rq_wait rq_wait[WBT_NUM_RWQ];
struct rq_depth rq_depth;
};
static inline struct rq_wb *RQWB(struct rq_qos *rqos)
{
return container_of(rqos, struct rq_wb, rqos);
}
static inline void wbt_clear_state(struct request *rq)
{
rq->wbt_flags = 0;
}
static inline enum wbt_flags wbt_flags(struct request *rq)
{
return rq->wbt_flags;
}
static inline bool wbt_is_tracked(struct request *rq)
{
return rq->wbt_flags & WBT_TRACKED;
}
static inline bool wbt_is_read(struct request *rq)
{
return rq->wbt_flags & WBT_READ;
}
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->enable_state != WBT_STATE_OFF_DEFAULT &&
rwb->enable_state != WBT_STATE_OFF_MANUAL;
}
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 backing_dev_info *bdi = rwb->rqos.disk->bdi;
return time_before(jiffies, bdi->last_bdp_sleep + HZ);
}
static inline struct rq_wait *get_rq_wait(struct rq_wb *rwb,
enum wbt_flags wb_acct)
{
if (wb_acct & WBT_SWAP)
return &rwb->rq_wait[WBT_RWQ_SWAP];
else if (wb_acct & WBT_DISCARD)
return &rwb->rq_wait[WBT_RWQ_DISCARD];
return &rwb->rq_wait[WBT_RWQ_BG];
}
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 (wq_has_sleeper(&rqw->wait))
wake_up_all(&rqw->wait);
}
}
static void wbt_rqw_done(struct rq_wb *rwb, struct rq_wait *rqw,
enum wbt_flags wb_acct)
{
int inflight, limit;
inflight = atomic_dec_return(&rqw->inflight);
/*
* For discards, our limit is always the background. For writes, if
* the device does write back caching, drop further down before we
* wake people up.
*/
if (wb_acct & WBT_DISCARD)
limit = rwb->wb_background;
else if (blk_queue_write_cache(rwb->rqos.disk->queue) &&
!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 (wq_has_sleeper(&rqw->wait)) {
int diff = limit - inflight;
if (!inflight || diff >= rwb->wb_background / 2)
wake_up_all(&rqw->wait);
}
}
static void __wbt_done(struct rq_qos *rqos, enum wbt_flags wb_acct)
{
struct rq_wb *rwb = RQWB(rqos);
struct rq_wait *rqw;
if (!(wb_acct & WBT_TRACKED))
return;
rqw = get_rq_wait(rwb, wb_acct);
wbt_rqw_done(rwb, rqw, wb_acct);
}
/*
* Called on completion of a request. Note that it's also called when
* a request is merged, when the request gets freed.
*/
static void wbt_done(struct rq_qos *rqos, struct request *rq)
{
struct rq_wb *rwb = RQWB(rqos);
if (!wbt_is_tracked(rq)) {
if (rwb->sync_cookie == rq) {
rwb->sync_issue = 0;
rwb->sync_cookie = NULL;
}
if (wbt_is_read(rq))
wb_timestamp(rwb, &rwb->last_comp);
} else {
WARN_ON_ONCE(rq == rwb->sync_cookie);
__wbt_done(rqos, wbt_flags(rq));
}
wbt_clear_state(rq);
}
static inline bool 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[READ].nr_samples >= 1 &&
stat[WRITE].nr_samples >= RWB_MIN_WRITE_SAMPLES);
}
static u64 rwb_sync_issue_lat(struct rq_wb *rwb)
{
u64 issue = READ_ONCE(rwb->sync_issue);
if (!issue || !rwb->sync_cookie)
return 0;
return blk_time_get_ns() - issue;
}
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;
}
enum {
LAT_OK = 1,
LAT_UNKNOWN,
LAT_UNKNOWN_WRITES,
LAT_EXCEEDED,
};
static int latency_exceeded(struct rq_wb *rwb, struct blk_rq_stat *stat)
{
struct backing_dev_info *bdi = rwb->rqos.disk->bdi;
struct rq_depth *rqd = &rwb->rq_depth;
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[READ].nr_samples)) {
trace_wbt_lat(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[WRITE].nr_samples || 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[READ].min > rwb->min_lat_nsec) {
trace_wbt_lat(bdi, stat[READ].min);
trace_wbt_stat(bdi, stat);
return LAT_EXCEEDED;
}
if (rqd->scale_step)
trace_wbt_stat(bdi, stat);
return LAT_OK;
}
static void rwb_trace_step(struct rq_wb *rwb, const char *msg)
{
struct backing_dev_info *bdi = rwb->rqos.disk->bdi;
struct rq_depth *rqd = &rwb->rq_depth;
trace_wbt_step(bdi, msg, rqd->scale_step, rwb->cur_win_nsec,
rwb->wb_background, rwb->wb_normal, rqd->max_depth);
}
static void calc_wb_limits(struct rq_wb *rwb)
{
if (rwb->min_lat_nsec == 0) {
rwb->wb_normal = rwb->wb_background = 0;
} else if (rwb->rq_depth.max_depth <= 2) {
rwb->wb_normal = rwb->rq_depth.max_depth;
rwb->wb_background = 1;
} else {
rwb->wb_normal = (rwb->rq_depth.max_depth + 1) / 2;
rwb->wb_background = (rwb->rq_depth.max_depth + 3) / 4;
}
}
static void scale_up(struct rq_wb *rwb)
{
if (!rq_depth_scale_up(&rwb->rq_depth))
return;
calc_wb_limits(rwb);
rwb->unknown_cnt = 0;
rwb_wake_all(rwb);
rwb_trace_step(rwb, tracepoint_string("scale up"));
}
static void scale_down(struct rq_wb *rwb, bool hard_throttle)
{
if (!rq_depth_scale_down(&rwb->rq_depth, hard_throttle))
return;
calc_wb_limits(rwb);
rwb->unknown_cnt = 0;
rwb_trace_step(rwb, tracepoint_string("scale down"));
}
static void rwb_arm_timer(struct rq_wb *rwb)
{
struct rq_depth *rqd = &rwb->rq_depth;
if (rqd->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((rqd->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;
}
blk_stat_activate_nsecs(rwb->cb, rwb->cur_win_nsec);
}
static void wb_timer_fn(struct blk_stat_callback *cb)
{
struct rq_wb *rwb = cb->data;
struct rq_depth *rqd = &rwb->rq_depth;
unsigned int inflight = wbt_inflight(rwb);
int status;
if (!rwb->rqos.disk)
return;
status = latency_exceeded(rwb, cb->stat);
trace_wbt_timer(rwb->rqos.disk->bdi, status, rqd->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:
/*
* 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.
*/
scale_up(rwb);
break;
case LAT_UNKNOWN:
if (++rwb->unknown_cnt < RWB_UNKNOWN_BUMP)
break;
/*
* We get here when 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).
*/
if (rqd->scale_step > 0)
scale_up(rwb);
else if (rqd->scale_step < 0)
scale_down(rwb, false);
break;
default:
break;
}
/*
* Re-arm timer, if we have IO in flight
*/
if (rqd->scale_step || inflight)
rwb_arm_timer(rwb);
}
static void wbt_update_limits(struct rq_wb *rwb)
{
struct rq_depth *rqd = &rwb->rq_depth;
rqd->scale_step = 0;
rqd->scaled_max = false;
rq_depth_calc_max_depth(rqd);
calc_wb_limits(rwb);
rwb_wake_all(rwb);
}
bool wbt_disabled(struct request_queue *q)
{
struct rq_qos *rqos = wbt_rq_qos(q);
return !rqos || !rwb_enabled(RQWB(rqos));
}
u64 wbt_get_min_lat(struct request_queue *q)
{
struct rq_qos *rqos = wbt_rq_qos(q);
if (!rqos)
return 0;
return RQWB(rqos)->min_lat_nsec;
}
void wbt_set_min_lat(struct request_queue *q, u64 val)
{
struct rq_qos *rqos = wbt_rq_qos(q);
if (!rqos)
return;
RQWB(rqos)->min_lat_nsec = val;
if (val)
RQWB(rqos)->enable_state = WBT_STATE_ON_MANUAL;
else
RQWB(rqos)->enable_state = WBT_STATE_OFF_MANUAL;
wbt_update_limits(RQWB(rqos));
}
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 | REQ_SWAP)
static inline unsigned int get_limit(struct rq_wb *rwb, blk_opf_t opf)
{
unsigned int limit;
if ((opf & REQ_OP_MASK) == REQ_OP_DISCARD)
return rwb->wb_background;
/*
* At this point we know it's a buffered write. If this is
* swap trying to free memory, or REQ_SYNC is 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 ((opf & REQ_HIPRIO) || wb_recent_wait(rwb))
limit = rwb->rq_depth.max_depth;
else if ((opf & REQ_BACKGROUND) || 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;
}
struct wbt_wait_data {
struct rq_wb *rwb;
enum wbt_flags wb_acct;
blk_opf_t opf;
};
static bool wbt_inflight_cb(struct rq_wait *rqw, void *private_data)
{
struct wbt_wait_data *data = private_data;
return rq_wait_inc_below(rqw, get_limit(data->rwb, data->opf));
}
static void wbt_cleanup_cb(struct rq_wait *rqw, void *private_data)
{
struct wbt_wait_data *data = private_data;
wbt_rqw_done(data->rwb, rqw, data->wb_acct);
}
/*
* 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, enum wbt_flags wb_acct,
blk_opf_t opf)
{
struct rq_wait *rqw = get_rq_wait(rwb, wb_acct);
struct wbt_wait_data data = {
.rwb = rwb,
.wb_acct = wb_acct,
.opf = opf,
};
rq_qos_wait(rqw, &data, wbt_inflight_cb, wbt_cleanup_cb);
}
static inline bool wbt_should_throttle(struct bio *bio)
{
switch (bio_op(bio)) {
case REQ_OP_WRITE:
/*
* Don't throttle WRITE_ODIRECT
*/
if ((bio->bi_opf & (REQ_SYNC | REQ_IDLE)) ==
(REQ_SYNC | REQ_IDLE))
return false;
fallthrough;
case REQ_OP_DISCARD:
return true;
default:
return false;
}
}
static enum wbt_flags bio_to_wbt_flags(struct rq_wb *rwb, struct bio *bio)
{
enum wbt_flags flags = 0;
if (!rwb_enabled(rwb))
return 0;
if (bio_op(bio) == REQ_OP_READ) {
flags = WBT_READ;
} else if (wbt_should_throttle(bio)) {
if (bio->bi_opf & REQ_SWAP)
flags |= WBT_SWAP;
if (bio_op(bio) == REQ_OP_DISCARD)
flags |= WBT_DISCARD;
flags |= WBT_TRACKED;
}
return flags;
}
static void wbt_cleanup(struct rq_qos *rqos, struct bio *bio)
{
struct rq_wb *rwb = RQWB(rqos);
enum wbt_flags flags = bio_to_wbt_flags(rwb, bio);
__wbt_done(rqos, flags);
}
/*
* 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.
*/
static void wbt_wait(struct rq_qos *rqos, struct bio *bio)
{
struct rq_wb *rwb = RQWB(rqos);
enum wbt_flags flags;
flags = bio_to_wbt_flags(rwb, bio);
if (!(flags & WBT_TRACKED)) {
if (flags & WBT_READ)
wb_timestamp(rwb, &rwb->last_issue);
return;
}
__wbt_wait(rwb, flags, bio->bi_opf);
if (!blk_stat_is_active(rwb->cb))
rwb_arm_timer(rwb);
}
static void wbt_track(struct rq_qos *rqos, struct request *rq, struct bio *bio)
{
struct rq_wb *rwb = RQWB(rqos);
rq->wbt_flags |= bio_to_wbt_flags(rwb, bio);
}
static void wbt_issue(struct rq_qos *rqos, struct request *rq)
{
struct rq_wb *rwb = RQWB(rqos);
if (!rwb_enabled(rwb))
return;
/*
* 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. The request can go away when it 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(rq) && !rwb->sync_issue) {
rwb->sync_cookie = rq;
rwb->sync_issue = rq->io_start_time_ns;
}
}
static void wbt_requeue(struct rq_qos *rqos, struct request *rq)
{
struct rq_wb *rwb = RQWB(rqos);
if (!rwb_enabled(rwb))
return;
if (rq == rwb->sync_cookie) {
rwb->sync_issue = 0;
rwb->sync_cookie = NULL;
}
}
/*
* Enable wbt if defaults are configured that way
*/
void wbt_enable_default(struct gendisk *disk)
{
struct request_queue *q = disk->queue;
struct rq_qos *rqos;
bool enable = IS_ENABLED(CONFIG_BLK_WBT_MQ);
if (q->elevator &&
test_bit(ELEVATOR_FLAG_DISABLE_WBT, &q->elevator->flags))
enable = false;
/* Throttling already enabled? */
rqos = wbt_rq_qos(q);
if (rqos) {
if (enable && RQWB(rqos)->enable_state == WBT_STATE_OFF_DEFAULT)
RQWB(rqos)->enable_state = WBT_STATE_ON_DEFAULT;
return;
}
/* Queue not registered? Maybe shutting down... */
if (!blk_queue_registered(q))
return;
if (queue_is_mq(q) && enable)
wbt_init(disk);
}
EXPORT_SYMBOL_GPL(wbt_enable_default);
u64 wbt_default_latency_nsec(struct request_queue *q)
{
/*
* We default to 2msec for non-rotational storage, and 75msec
* for rotational storage.
*/
if (blk_queue_nonrot(q))
return 2000000ULL;
else
return 75000000ULL;
}
static int wbt_data_dir(const struct request *rq)
{
const enum req_op op = req_op(rq);
if (op == REQ_OP_READ)
return READ;
else if (op_is_write(op))
return WRITE;
/* don't account */
return -1;
}
static void wbt_queue_depth_changed(struct rq_qos *rqos)
{
RQWB(rqos)->rq_depth.queue_depth = blk_queue_depth(rqos->disk->queue);
wbt_update_limits(RQWB(rqos));
}
static void wbt_exit(struct rq_qos *rqos)
{
struct rq_wb *rwb = RQWB(rqos);
blk_stat_remove_callback(rqos->disk->queue, rwb->cb);
blk_stat_free_callback(rwb->cb);
kfree(rwb);
}
/*
* Disable wbt, if enabled by default.
*/
void wbt_disable_default(struct gendisk *disk)
{
struct rq_qos *rqos = wbt_rq_qos(disk->queue);
struct rq_wb *rwb;
if (!rqos)
return;
rwb = RQWB(rqos);
if (rwb->enable_state == WBT_STATE_ON_DEFAULT) {
blk_stat_deactivate(rwb->cb);
rwb->enable_state = WBT_STATE_OFF_DEFAULT;
}
}
EXPORT_SYMBOL_GPL(wbt_disable_default);
#ifdef CONFIG_BLK_DEBUG_FS
static int wbt_curr_win_nsec_show(void *data, struct seq_file *m)
{
struct rq_qos *rqos = data;
struct rq_wb *rwb = RQWB(rqos);
seq_printf(m, "%llu\n", rwb->cur_win_nsec);
return 0;
}
static int wbt_enabled_show(void *data, struct seq_file *m)
{
struct rq_qos *rqos = data;
struct rq_wb *rwb = RQWB(rqos);
seq_printf(m, "%d\n", rwb->enable_state);
return 0;
}
static int wbt_id_show(void *data, struct seq_file *m)
{
struct rq_qos *rqos = data;
seq_printf(m, "%u\n", rqos->id);
return 0;
}
static int wbt_inflight_show(void *data, struct seq_file *m)
{
struct rq_qos *rqos = data;
struct rq_wb *rwb = RQWB(rqos);
int i;
for (i = 0; i < WBT_NUM_RWQ; i++)
seq_printf(m, "%d: inflight %d\n", i,
atomic_read(&rwb->rq_wait[i].inflight));
return 0;
}
static int wbt_min_lat_nsec_show(void *data, struct seq_file *m)
{
struct rq_qos *rqos = data;
struct rq_wb *rwb = RQWB(rqos);
seq_printf(m, "%lu\n", rwb->min_lat_nsec);
return 0;
}
static int wbt_unknown_cnt_show(void *data, struct seq_file *m)
{
struct rq_qos *rqos = data;
struct rq_wb *rwb = RQWB(rqos);
seq_printf(m, "%u\n", rwb->unknown_cnt);
return 0;
}
static int wbt_normal_show(void *data, struct seq_file *m)
{
struct rq_qos *rqos = data;
struct rq_wb *rwb = RQWB(rqos);
seq_printf(m, "%u\n", rwb->wb_normal);
return 0;
}
static int wbt_background_show(void *data, struct seq_file *m)
{
struct rq_qos *rqos = data;
struct rq_wb *rwb = RQWB(rqos);
seq_printf(m, "%u\n", rwb->wb_background);
return 0;
}
static const struct blk_mq_debugfs_attr wbt_debugfs_attrs[] = {
{"curr_win_nsec", 0400, wbt_curr_win_nsec_show},
{"enabled", 0400, wbt_enabled_show},
{"id", 0400, wbt_id_show},
{"inflight", 0400, wbt_inflight_show},
{"min_lat_nsec", 0400, wbt_min_lat_nsec_show},
{"unknown_cnt", 0400, wbt_unknown_cnt_show},
{"wb_normal", 0400, wbt_normal_show},
{"wb_background", 0400, wbt_background_show},
{},
};
#endif
static const struct rq_qos_ops wbt_rqos_ops = {
.throttle = wbt_wait,
.issue = wbt_issue,
.track = wbt_track,
.requeue = wbt_requeue,
.done = wbt_done,
.cleanup = wbt_cleanup,
.queue_depth_changed = wbt_queue_depth_changed,
.exit = wbt_exit,
#ifdef CONFIG_BLK_DEBUG_FS
.debugfs_attrs = wbt_debugfs_attrs,
#endif
};
int wbt_init(struct gendisk *disk)
{
struct request_queue *q = disk->queue;
struct rq_wb *rwb;
int i;
int ret;
rwb = kzalloc(sizeof(*rwb), GFP_KERNEL);
if (!rwb)
return -ENOMEM;
rwb->cb = blk_stat_alloc_callback(wb_timer_fn, wbt_data_dir, 2, rwb);
if (!rwb->cb) {
kfree(rwb);
return -ENOMEM;
}
for (i = 0; i < WBT_NUM_RWQ; i++)
rq_wait_init(&rwb->rq_wait[i]);
rwb->last_comp = rwb->last_issue = jiffies;
rwb->win_nsec = RWB_WINDOW_NSEC;
rwb->enable_state = WBT_STATE_ON_DEFAULT;
rwb->rq_depth.default_depth = RWB_DEF_DEPTH;
rwb->min_lat_nsec = wbt_default_latency_nsec(q);
rwb->rq_depth.queue_depth = blk_queue_depth(q);
wbt_update_limits(rwb);
/*
* Assign rwb and add the stats callback.
*/
mutex_lock(&q->rq_qos_mutex);
ret = rq_qos_add(&rwb->rqos, disk, RQ_QOS_WBT, &wbt_rqos_ops);
mutex_unlock(&q->rq_qos_mutex);
if (ret)
goto err_free;
blk_stat_add_callback(q, rwb->cb);
return 0;
err_free:
blk_stat_free_callback(rwb->cb);
kfree(rwb);
return ret;
}
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