// SPDX-License-Identifier: GPL-2.0
/*
* background writeback - scan btree for dirty data and write it to the backing
* device
*
* Copyright 2010, 2011 Kent Overstreet <[email protected]>
* Copyright 2012 Google, Inc.
*/
#include "bcache.h"
#include "btree.h"
#include "debug.h"
#include "writeback.h"
#include <linux/delay.h>
#include <linux/kthread.h>
#include <linux/sched/clock.h>
#include <trace/events/bcache.h>
static void update_gc_after_writeback(struct cache_set *c)
{
if (c->gc_after_writeback != (BCH_ENABLE_AUTO_GC) ||
c->gc_stats.in_use < BCH_AUTO_GC_DIRTY_THRESHOLD)
return;
c->gc_after_writeback |= BCH_DO_AUTO_GC;
}
/* Rate limiting */
static uint64_t __calc_target_rate(struct cached_dev *dc)
{
struct cache_set *c = dc->disk.c;
/*
* This is the size of the cache, minus the amount used for
* flash-only devices
*/
uint64_t cache_sectors = c->nbuckets * c->cache->sb.bucket_size -
atomic_long_read(&c->flash_dev_dirty_sectors);
/*
* Unfortunately there is no control of global dirty data. If the
* user states that they want 10% dirty data in the cache, and has,
* e.g., 5 backing volumes of equal size, we try and ensure each
* backing volume uses about 2% of the cache for dirty data.
*/
uint32_t bdev_share =
div64_u64(bdev_nr_sectors(dc->bdev) << WRITEBACK_SHARE_SHIFT,
c->cached_dev_sectors);
uint64_t cache_dirty_target =
div_u64(cache_sectors * dc->writeback_percent, 100);
/* Ensure each backing dev gets at least one dirty share */
if (bdev_share < 1)
bdev_share = 1;
return (cache_dirty_target * bdev_share) >> WRITEBACK_SHARE_SHIFT;
}
static void __update_writeback_rate(struct cached_dev *dc)
{
/*
* PI controller:
* Figures out the amount that should be written per second.
*
* First, the error (number of sectors that are dirty beyond our
* target) is calculated. The error is accumulated (numerically
* integrated).
*
* Then, the proportional value and integral value are scaled
* based on configured values. These are stored as inverses to
* avoid fixed point math and to make configuration easy-- e.g.
* the default value of 40 for writeback_rate_p_term_inverse
* attempts to write at a rate that would retire all the dirty
* blocks in 40 seconds.
*
* The writeback_rate_i_inverse value of 10000 means that 1/10000th
* of the error is accumulated in the integral term per second.
* This acts as a slow, long-term average that is not subject to
* variations in usage like the p term.
*/
int64_t target = __calc_target_rate(dc);
int64_t dirty = bcache_dev_sectors_dirty(&dc->disk);
int64_t error = dirty - target;
int64_t proportional_scaled =
div_s64(error, dc->writeback_rate_p_term_inverse);
int64_t integral_scaled;
uint32_t new_rate;
/*
* We need to consider the number of dirty buckets as well
* when calculating the proportional_scaled, Otherwise we might
* have an unreasonable small writeback rate at a highly fragmented situation
* when very few dirty sectors consumed a lot dirty buckets, the
* worst case is when dirty buckets reached cutoff_writeback_sync and
* dirty data is still not even reached to writeback percent, so the rate
* still will be at the minimum value, which will cause the write
* stuck at a non-writeback mode.
*/
struct cache_set *c = dc->disk.c;
int64_t dirty_buckets = c->nbuckets - c->avail_nbuckets;
if (dc->writeback_consider_fragment &&
c->gc_stats.in_use > BCH_WRITEBACK_FRAGMENT_THRESHOLD_LOW && dirty > 0) {
int64_t fragment =
div_s64((dirty_buckets * c->cache->sb.bucket_size), dirty);
int64_t fp_term;
int64_t fps;
if (c->gc_stats.in_use <= BCH_WRITEBACK_FRAGMENT_THRESHOLD_MID) {
fp_term = (int64_t)dc->writeback_rate_fp_term_low *
(c->gc_stats.in_use - BCH_WRITEBACK_FRAGMENT_THRESHOLD_LOW);
} else if (c->gc_stats.in_use <= BCH_WRITEBACK_FRAGMENT_THRESHOLD_HIGH) {
fp_term = (int64_t)dc->writeback_rate_fp_term_mid *
(c->gc_stats.in_use - BCH_WRITEBACK_FRAGMENT_THRESHOLD_MID);
} else {
fp_term = (int64_t)dc->writeback_rate_fp_term_high *
(c->gc_stats.in_use - BCH_WRITEBACK_FRAGMENT_THRESHOLD_HIGH);
}
fps = div_s64(dirty, dirty_buckets) * fp_term;
if (fragment > 3 && fps > proportional_scaled) {
/* Only overrite the p when fragment > 3 */
proportional_scaled = fps;
}
}
if ((error < 0 && dc->writeback_rate_integral > 0) ||
(error > 0 && time_before64(local_clock(),
dc->writeback_rate.next + NSEC_PER_MSEC))) {
/*
* Only decrease the integral term if it's more than
* zero. Only increase the integral term if the device
* is keeping up. (Don't wind up the integral
* ineffectively in either case).
*
* It's necessary to scale this by
* writeback_rate_update_seconds to keep the integral
* term dimensioned properly.
*/
dc->writeback_rate_integral += error *
dc->writeback_rate_update_seconds;
}
integral_scaled = div_s64(dc->writeback_rate_integral,
dc->writeback_rate_i_term_inverse);
new_rate = clamp_t(int32_t, (proportional_scaled + integral_scaled),
dc->writeback_rate_minimum, NSEC_PER_SEC);
dc->writeback_rate_proportional = proportional_scaled;
dc->writeback_rate_integral_scaled = integral_scaled;
dc->writeback_rate_change = new_rate -
atomic_long_read(&dc->writeback_rate.rate);
atomic_long_set(&dc->writeback_rate.rate, new_rate);
dc->writeback_rate_target = target;
}
static bool idle_counter_exceeded(struct cache_set *c)
{
int counter, dev_nr;
/*
* If c->idle_counter is overflow (idel for really long time),
* reset as 0 and not set maximum rate this time for code
* simplicity.
*/
counter = atomic_inc_return(&c->idle_counter);
if (counter <= 0) {
atomic_set(&c->idle_counter, 0);
return false;
}
dev_nr = atomic_read(&c->attached_dev_nr);
if (dev_nr == 0)
return false;
/*
* c->idle_counter is increased by writeback thread of all
* attached backing devices, in order to represent a rough
* time period, counter should be divided by dev_nr.
* Otherwise the idle time cannot be larger with more backing
* device attached.
* The following calculation equals to checking
* (counter / dev_nr) < (dev_nr * 6)
*/
if (counter < (dev_nr * dev_nr * 6))
return false;
return true;
}
/*
* Idle_counter is increased every time when update_writeback_rate() is
* called. If all backing devices attached to the same cache set have
* identical dc->writeback_rate_update_seconds values, it is about 6
* rounds of update_writeback_rate() on each backing device before
* c->at_max_writeback_rate is set to 1, and then max wrteback rate set
* to each dc->writeback_rate.rate.
* In order to avoid extra locking cost for counting exact dirty cached
* devices number, c->attached_dev_nr is used to calculate the idle
* throushold. It might be bigger if not all cached device are in write-
* back mode, but it still works well with limited extra rounds of
* update_writeback_rate().
*/
static bool set_at_max_writeback_rate(struct cache_set *c,
struct cached_dev *dc)
{
/* Don't sst max writeback rate if it is disabled */
if (!c->idle_max_writeback_rate_enabled)
return false;
/* Don't set max writeback rate if gc is running */
if (!c->gc_mark_valid)
return false;
if (!idle_counter_exceeded(c))
return false;
if (atomic_read(&c->at_max_writeback_rate) != 1)
atomic_set(&c->at_max_writeback_rate, 1);
atomic_long_set(&dc->writeback_rate.rate, INT_MAX);
/* keep writeback_rate_target as existing value */
dc->writeback_rate_proportional = 0;
dc->writeback_rate_integral_scaled = 0;
dc->writeback_rate_change = 0;
/*
* In case new I/O arrives during before
* set_at_max_writeback_rate() returns.
*/
if (!idle_counter_exceeded(c) ||
!atomic_read(&c->at_max_writeback_rate))
return false;
return true;
}
static void update_writeback_rate(struct work_struct *work)
{
struct cached_dev *dc = container_of(to_delayed_work(work),
struct cached_dev,
writeback_rate_update);
struct cache_set *c = dc->disk.c;
/*
* should check BCACHE_DEV_RATE_DW_RUNNING before calling
* cancel_delayed_work_sync().
*/
set_bit(BCACHE_DEV_RATE_DW_RUNNING, &dc->disk.flags);
/* paired with where BCACHE_DEV_RATE_DW_RUNNING is tested */
smp_mb__after_atomic();
/*
* CACHE_SET_IO_DISABLE might be set via sysfs interface,
* check it here too.
*/
if (!test_bit(BCACHE_DEV_WB_RUNNING, &dc->disk.flags) ||
test_bit(CACHE_SET_IO_DISABLE, &c->flags)) {
clear_bit(BCACHE_DEV_RATE_DW_RUNNING, &dc->disk.flags);
/* paired with where BCACHE_DEV_RATE_DW_RUNNING is tested */
smp_mb__after_atomic();
return;
}
/*
* If the whole cache set is idle, set_at_max_writeback_rate()
* will set writeback rate to a max number. Then it is
* unncessary to update writeback rate for an idle cache set
* in maximum writeback rate number(s).
*/
if (atomic_read(&dc->has_dirty) && dc->writeback_percent &&
!set_at_max_writeback_rate(c, dc)) {
do {
if (!down_read_trylock((&dc->writeback_lock))) {
dc->rate_update_retry++;
if (dc->rate_update_retry <=
BCH_WBRATE_UPDATE_MAX_SKIPS)
break;
down_read(&dc->writeback_lock);
dc->rate_update_retry = 0;
}
__update_writeback_rate(dc);
update_gc_after_writeback(c);
up_read(&dc->writeback_lock);
} while (0);
}
/*
* CACHE_SET_IO_DISABLE might be set via sysfs interface,
* check it here too.
*/
if (test_bit(BCACHE_DEV_WB_RUNNING, &dc->disk.flags) &&
!test_bit(CACHE_SET_IO_DISABLE, &c->flags)) {
schedule_delayed_work(&dc->writeback_rate_update,
dc->writeback_rate_update_seconds * HZ);
}
/*
* should check BCACHE_DEV_RATE_DW_RUNNING before calling
* cancel_delayed_work_sync().
*/
clear_bit(BCACHE_DEV_RATE_DW_RUNNING, &dc->disk.flags);
/* paired with where BCACHE_DEV_RATE_DW_RUNNING is tested */
smp_mb__after_atomic();
}
static unsigned int writeback_delay(struct cached_dev *dc,
unsigned int sectors)
{
if (test_bit(BCACHE_DEV_DETACHING, &dc->disk.flags) ||
!dc->writeback_percent)
return 0;
return bch_next_delay(&dc->writeback_rate, sectors);
}
struct dirty_io {
struct closure cl;
struct cached_dev *dc;
uint16_t sequence;
struct bio bio;
};
static void dirty_init(struct keybuf_key *w)
{
struct dirty_io *io = w->private;
struct bio *bio = &io->bio;
bio_init(bio, NULL, bio->bi_inline_vecs,
DIV_ROUND_UP(KEY_SIZE(&w->key), PAGE_SECTORS), 0);
if (!io->dc->writeback_percent)
bio_set_prio(bio, IOPRIO_PRIO_VALUE(IOPRIO_CLASS_IDLE, 0));
bio->bi_iter.bi_size = KEY_SIZE(&w->key) << 9;
bio->bi_private = w;
bch_bio_map(bio, NULL);
}
static CLOSURE_CALLBACK(dirty_io_destructor)
{
closure_type(io, struct dirty_io, cl);
kfree(io);
}
static CLOSURE_CALLBACK(write_dirty_finish)
{
closure_type(io, struct dirty_io, cl);
struct keybuf_key *w = io->bio.bi_private;
struct cached_dev *dc = io->dc;
bio_free_pages(&io->bio);
/* This is kind of a dumb way of signalling errors. */
if (KEY_DIRTY(&w->key)) {
int ret;
unsigned int i;
struct keylist keys;
bch_keylist_init(&keys);
bkey_copy(keys.top, &w->key);
SET_KEY_DIRTY(keys.top, false);
bch_keylist_push(&keys);
for (i = 0; i < KEY_PTRS(&w->key); i++)
atomic_inc(&PTR_BUCKET(dc->disk.c, &w->key, i)->pin);
ret = bch_btree_insert(dc->disk.c, &keys, NULL, &w->key);
if (ret)
trace_bcache_writeback_collision(&w->key);
atomic_long_inc(ret
? &dc->disk.c->writeback_keys_failed
: &dc->disk.c->writeback_keys_done);
}
bch_keybuf_del(&dc->writeback_keys, w);
up(&dc->in_flight);
closure_return_with_destructor(cl, dirty_io_destructor);
}
static void dirty_endio(struct bio *bio)
{
struct keybuf_key *w = bio->bi_private;
struct dirty_io *io = w->private;
if (bio->bi_status) {
SET_KEY_DIRTY(&w->key, false);
bch_count_backing_io_errors(io->dc, bio);
}
closure_put(&io->cl);
}
static CLOSURE_CALLBACK(write_dirty)
{
closure_type(io, struct dirty_io, cl);
struct keybuf_key *w = io->bio.bi_private;
struct cached_dev *dc = io->dc;
uint16_t next_sequence;
if (atomic_read(&dc->writeback_sequence_next) != io->sequence) {
/* Not our turn to write; wait for a write to complete */
closure_wait(&dc->writeback_ordering_wait, cl);
if (atomic_read(&dc->writeback_sequence_next) == io->sequence) {
/*
* Edge case-- it happened in indeterminate order
* relative to when we were added to wait list..
*/
closure_wake_up(&dc->writeback_ordering_wait);
}
continue_at(cl, write_dirty, io->dc->writeback_write_wq);
return;
}
next_sequence = io->sequence + 1;
/*
* IO errors are signalled using the dirty bit on the key.
* If we failed to read, we should not attempt to write to the
* backing device. Instead, immediately go to write_dirty_finish
* to clean up.
*/
if (KEY_DIRTY(&w->key)) {
dirty_init(w);
io->bio.bi_opf = REQ_OP_WRITE;
io->bio.bi_iter.bi_sector = KEY_START(&w->key);
bio_set_dev(&io->bio, io->dc->bdev);
io->bio.bi_end_io = dirty_endio;
/* I/O request sent to backing device */
closure_bio_submit(io->dc->disk.c, &io->bio, cl);
}
atomic_set(&dc->writeback_sequence_next, next_sequence);
closure_wake_up(&dc->writeback_ordering_wait);
continue_at(cl, write_dirty_finish, io->dc->writeback_write_wq);
}
static void read_dirty_endio(struct bio *bio)
{
struct keybuf_key *w = bio->bi_private;
struct dirty_io *io = w->private;
/* is_read = 1 */
bch_count_io_errors(io->dc->disk.c->cache,
bio->bi_status, 1,
"reading dirty data from cache");
dirty_endio(bio);
}
static CLOSURE_CALLBACK(read_dirty_submit)
{
closure_type(io, struct dirty_io, cl);
closure_bio_submit(io->dc->disk.c, &io->bio, cl);
continue_at(cl, write_dirty, io->dc->writeback_write_wq);
}
static void read_dirty(struct cached_dev *dc)
{
unsigned int delay = 0;
struct keybuf_key *next, *keys[MAX_WRITEBACKS_IN_PASS], *w;
size_t size;
int nk, i;
struct dirty_io *io;
struct closure cl;
uint16_t sequence = 0;
BUG_ON(!llist_empty(&dc->writeback_ordering_wait.list));
atomic_set(&dc->writeback_sequence_next, sequence);
closure_init_stack(&cl);
/*
* XXX: if we error, background writeback just spins. Should use some
* mempools.
*/
next = bch_keybuf_next(&dc->writeback_keys);
while (!kthread_should_stop() &&
!test_bit(CACHE_SET_IO_DISABLE, &dc->disk.c->flags) &&
next) {
size = 0;
nk = 0;
do {
BUG_ON(ptr_stale(dc->disk.c, &next->key, 0));
/*
* Don't combine too many operations, even if they
* are all small.
*/
if (nk >= MAX_WRITEBACKS_IN_PASS)
break;
/*
* If the current operation is very large, don't
* further combine operations.
*/
if (size >= MAX_WRITESIZE_IN_PASS)
break;
/*
* Operations are only eligible to be combined
* if they are contiguous.
*
* TODO: add a heuristic willing to fire a
* certain amount of non-contiguous IO per pass,
* so that we can benefit from backing device
* command queueing.
*/
if ((nk != 0) && bkey_cmp(&keys[nk-1]->key,
&START_KEY(&next->key)))
break;
size += KEY_SIZE(&next->key);
keys[nk++] = next;
} while ((next = bch_keybuf_next(&dc->writeback_keys)));
/* Now we have gathered a set of 1..5 keys to write back. */
for (i = 0; i < nk; i++) {
w = keys[i];
io = kzalloc(struct_size(io, bio.bi_inline_vecs,
DIV_ROUND_UP(KEY_SIZE(&w->key), PAGE_SECTORS)),
GFP_KERNEL);
if (!io)
goto err;
w->private = io;
io->dc = dc;
io->sequence = sequence++;
dirty_init(w);
io->bio.bi_opf = REQ_OP_READ;
io->bio.bi_iter.bi_sector = PTR_OFFSET(&w->key, 0);
bio_set_dev(&io->bio, dc->disk.c->cache->bdev);
io->bio.bi_end_io = read_dirty_endio;
if (bch_bio_alloc_pages(&io->bio, GFP_KERNEL))
goto err_free;
trace_bcache_writeback(&w->key);
down(&dc->in_flight);
/*
* We've acquired a semaphore for the maximum
* simultaneous number of writebacks; from here
* everything happens asynchronously.
*/
closure_call(&io->cl, read_dirty_submit, NULL, &cl);
}
delay = writeback_delay(dc, size);
while (!kthread_should_stop() &&
!test_bit(CACHE_SET_IO_DISABLE, &dc->disk.c->flags) &&
delay) {
schedule_timeout_interruptible(delay);
delay = writeback_delay(dc, 0);
}
}
if (0) {
err_free:
kfree(w->private);
err:
bch_keybuf_del(&dc->writeback_keys, w);
}
/*
* Wait for outstanding writeback IOs to finish (and keybuf slots to be
* freed) before refilling again
*/
closure_sync(&cl);
}
/* Scan for dirty data */
void bcache_dev_sectors_dirty_add(struct cache_set *c, unsigned int inode,
uint64_t offset, int nr_sectors)
{
struct bcache_device *d = c->devices[inode];
unsigned int stripe_offset, sectors_dirty;
int stripe;
if (!d)
return;
stripe = offset_to_stripe(d, offset);
if (stripe < 0)
return;
if (UUID_FLASH_ONLY(&c->uuids[inode]))
atomic_long_add(nr_sectors, &c->flash_dev_dirty_sectors);
stripe_offset = offset & (d->stripe_size - 1);
while (nr_sectors) {
int s = min_t(unsigned int, abs(nr_sectors),
d->stripe_size - stripe_offset);
if (nr_sectors < 0)
s = -s;
if (stripe >= d->nr_stripes)
return;
sectors_dirty = atomic_add_return(s,
d->stripe_sectors_dirty + stripe);
if (sectors_dirty == d->stripe_size) {
if (!test_bit(stripe, d->full_dirty_stripes))
set_bit(stripe, d->full_dirty_stripes);
} else {
if (test_bit(stripe, d->full_dirty_stripes))
clear_bit(stripe, d->full_dirty_stripes);
}
nr_sectors -= s;
stripe_offset = 0;
stripe++;
}
}
static bool dirty_pred(struct keybuf *buf, struct bkey *k)
{
struct cached_dev *dc = container_of(buf,
struct cached_dev,
writeback_keys);
BUG_ON(KEY_INODE(k) != dc->disk.id);
return KEY_DIRTY(k);
}
static void refill_full_stripes(struct cached_dev *dc)
{
struct keybuf *buf = &dc->writeback_keys;
unsigned int start_stripe, next_stripe;
int stripe;
bool wrapped = false;
stripe = offset_to_stripe(&dc->disk, KEY_OFFSET(&buf->last_scanned));
if (stripe < 0)
stripe = 0;
start_stripe = stripe;
while (1) {
stripe = find_next_bit(dc->disk.full_dirty_stripes,
dc->disk.nr_stripes, stripe);
if (stripe == dc->disk.nr_stripes)
goto next;
next_stripe = find_next_zero_bit(dc->disk.full_dirty_stripes,
dc->disk.nr_stripes, stripe);
buf->last_scanned = KEY(dc->disk.id,
stripe * dc->disk.stripe_size, 0);
bch_refill_keybuf(dc->disk.c, buf,
&KEY(dc->disk.id,
next_stripe * dc->disk.stripe_size, 0),
dirty_pred);
if (array_freelist_empty(&buf->freelist))
return;
stripe = next_stripe;
next:
if (wrapped && stripe > start_stripe)
return;
if (stripe == dc->disk.nr_stripes) {
stripe = 0;
wrapped = true;
}
}
}
/*
* Returns true if we scanned the entire disk
*/
static bool refill_dirty(struct cached_dev *dc)
{
struct keybuf *buf = &dc->writeback_keys;
struct bkey start = KEY(dc->disk.id, 0, 0);
struct bkey end = KEY(dc->disk.id, MAX_KEY_OFFSET, 0);
struct bkey start_pos;
/*
* make sure keybuf pos is inside the range for this disk - at bringup
* we might not be attached yet so this disk's inode nr isn't
* initialized then
*/
if (bkey_cmp(&buf->last_scanned, &start) < 0 ||
bkey_cmp(&buf->last_scanned, &end) > 0)
buf->last_scanned = start;
if (dc->partial_stripes_expensive) {
refill_full_stripes(dc);
if (array_freelist_empty(&buf->freelist))
return false;
}
start_pos = buf->last_scanned;
bch_refill_keybuf(dc->disk.c, buf, &end, dirty_pred);
if (bkey_cmp(&buf->last_scanned, &end) < 0)
return false;
/*
* If we get to the end start scanning again from the beginning, and
* only scan up to where we initially started scanning from:
*/
buf->last_scanned = start;
bch_refill_keybuf(dc->disk.c, buf, &start_pos, dirty_pred);
return bkey_cmp(&buf->last_scanned, &start_pos) >= 0;
}
static int bch_writeback_thread(void *arg)
{
struct cached_dev *dc = arg;
struct cache_set *c = dc->disk.c;
bool searched_full_index;
bch_ratelimit_reset(&dc->writeback_rate);
while (!kthread_should_stop() &&
!test_bit(CACHE_SET_IO_DISABLE, &c->flags)) {
down_write(&dc->writeback_lock);
set_current_state(TASK_INTERRUPTIBLE);
/*
* If the bache device is detaching, skip here and continue
* to perform writeback. Otherwise, if no dirty data on cache,
* or there is dirty data on cache but writeback is disabled,
* the writeback thread should sleep here and wait for others
* to wake up it.
*/
if (!test_bit(BCACHE_DEV_DETACHING, &dc->disk.flags) &&
(!atomic_read(&dc->has_dirty) || !dc->writeback_running)) {
up_write(&dc->writeback_lock);
if (kthread_should_stop() ||
test_bit(CACHE_SET_IO_DISABLE, &c->flags)) {
set_current_state(TASK_RUNNING);
break;
}
schedule();
continue;
}
set_current_state(TASK_RUNNING);
searched_full_index = refill_dirty(dc);
if (searched_full_index &&
RB_EMPTY_ROOT(&dc->writeback_keys.keys)) {
atomic_set(&dc->has_dirty, 0);
SET_BDEV_STATE(&dc->sb, BDEV_STATE_CLEAN);
bch_write_bdev_super(dc, NULL);
/*
* If bcache device is detaching via sysfs interface,
* writeback thread should stop after there is no dirty
* data on cache. BCACHE_DEV_DETACHING flag is set in
* bch_cached_dev_detach().
*/
if (test_bit(BCACHE_DEV_DETACHING, &dc->disk.flags)) {
struct closure cl;
closure_init_stack(&cl);
memset(&dc->sb.set_uuid, 0, 16);
SET_BDEV_STATE(&dc->sb, BDEV_STATE_NONE);
bch_write_bdev_super(dc, &cl);
closure_sync(&cl);
up_write(&dc->writeback_lock);
break;
}
/*
* When dirty data rate is high (e.g. 50%+), there might
* be heavy buckets fragmentation after writeback
* finished, which hurts following write performance.
* If users really care about write performance they
* may set BCH_ENABLE_AUTO_GC via sysfs, then when
* BCH_DO_AUTO_GC is set, garbage collection thread
* will be wake up here. After moving gc, the shrunk
* btree and discarded free buckets SSD space may be
* helpful for following write requests.
*/
if (c->gc_after_writeback ==
(BCH_ENABLE_AUTO_GC|BCH_DO_AUTO_GC)) {
c->gc_after_writeback &= ~BCH_DO_AUTO_GC;
force_wake_up_gc(c);
}
}
up_write(&dc->writeback_lock);
read_dirty(dc);
if (searched_full_index) {
unsigned int delay = dc->writeback_delay * HZ;
while (delay &&
!kthread_should_stop() &&
!test_bit(CACHE_SET_IO_DISABLE, &c->flags) &&
!test_bit(BCACHE_DEV_DETACHING, &dc->disk.flags))
delay = schedule_timeout_interruptible(delay);
bch_ratelimit_reset(&dc->writeback_rate);
}
}
if (dc->writeback_write_wq)
destroy_workqueue(dc->writeback_write_wq);
cached_dev_put(dc);
wait_for_kthread_stop();
return 0;
}
/* Init */
#define INIT_KEYS_EACH_TIME 500000
struct sectors_dirty_init {
struct btree_op op;
unsigned int inode;
size_t count;
};
static int sectors_dirty_init_fn(struct btree_op *_op, struct btree *b,
struct bkey *k)
{
struct sectors_dirty_init *op = container_of(_op,
struct sectors_dirty_init, op);
if (KEY_INODE(k) > op->inode)
return MAP_DONE;
if (KEY_DIRTY(k))
bcache_dev_sectors_dirty_add(b->c, KEY_INODE(k),
KEY_START(k), KEY_SIZE(k));
op->count++;
if (!(op->count % INIT_KEYS_EACH_TIME))
cond_resched();
return MAP_CONTINUE;
}
static int bch_root_node_dirty_init(struct cache_set *c,
struct bcache_device *d,
struct bkey *k)
{
struct sectors_dirty_init op;
int ret;
bch_btree_op_init(&op.op, -1);
op.inode = d->id;
op.count = 0;
ret = bcache_btree(map_keys_recurse,
k,
c->root,
&op.op,
&KEY(op.inode, 0, 0),
sectors_dirty_init_fn,
0);
if (ret < 0)
pr_warn("sectors dirty init failed, ret=%d!\n", ret);
/*
* The op may be added to cache_set's btree_cache_wait
* in mca_cannibalize(), must ensure it is removed from
* the list and release btree_cache_alloc_lock before
* free op memory.
* Otherwise, the btree_cache_wait will be damaged.
*/
bch_cannibalize_unlock(c);
finish_wait(&c->btree_cache_wait, &(&op.op)->wait);
return ret;
}
static int bch_dirty_init_thread(void *arg)
{
struct dirty_init_thrd_info *info = arg;
struct bch_dirty_init_state *state = info->state;
struct cache_set *c = state->c;
struct btree_iter iter;
struct bkey *k, *p;
int cur_idx, prev_idx, skip_nr;
k = p = NULL;
prev_idx = 0;
min_heap_init(&iter.heap, NULL, MAX_BSETS);
bch_btree_iter_init(&c->root->keys, &iter, NULL);
k = bch_btree_iter_next_filter(&iter, &c->root->keys, bch_ptr_bad);
BUG_ON(!k);
p = k;
while (k) {
spin_lock(&state->idx_lock);
cur_idx = state->key_idx;
state->key_idx++;
spin_unlock(&state->idx_lock);
skip_nr = cur_idx - prev_idx;
while (skip_nr) {
k = bch_btree_iter_next_filter(&iter,
&c->root->keys,
bch_ptr_bad);
if (k)
p = k;
else {
atomic_set(&state->enough, 1);
/* Update state->enough earlier */
smp_mb__after_atomic();
goto out;
}
skip_nr--;
}
if (p) {
if (bch_root_node_dirty_init(c, state->d, p) < 0)
goto out;
}
p = NULL;
prev_idx = cur_idx;
}
out:
/* In order to wake up state->wait in time */
smp_mb__before_atomic();
if (atomic_dec_and_test(&state->started))
wake_up(&state->wait);
return 0;
}
static int bch_btre_dirty_init_thread_nr(void)
{
int n = num_online_cpus()/2;
if (n == 0)
n = 1;
else if (n > BCH_DIRTY_INIT_THRD_MAX)
n = BCH_DIRTY_INIT_THRD_MAX;
return n;
}
void bch_sectors_dirty_init(struct bcache_device *d)
{
int i;
struct btree *b = NULL;
struct bkey *k = NULL;
struct btree_iter iter;
struct sectors_dirty_init op;
struct cache_set *c = d->c;
struct bch_dirty_init_state state;
min_heap_init(&iter.heap, NULL, MAX_BSETS);
retry_lock:
b = c->root;
rw_lock(0, b, b->level);
if (b != c->root) {
rw_unlock(0, b);
goto retry_lock;
}
/* Just count root keys if no leaf node */
if (c->root->level == 0) {
bch_btree_op_init(&op.op, -1);
op.inode = d->id;
op.count = 0;
for_each_key_filter(&c->root->keys,
k, &iter, bch_ptr_invalid) {
if (KEY_INODE(k) != op.inode)
continue;
sectors_dirty_init_fn(&op.op, c->root, k);
}
rw_unlock(0, b);
return;
}
memset(&state, 0, sizeof(struct bch_dirty_init_state));
state.c = c;
state.d = d;
state.total_threads = bch_btre_dirty_init_thread_nr();
state.key_idx = 0;
spin_lock_init(&state.idx_lock);
atomic_set(&state.started, 0);
atomic_set(&state.enough, 0);
init_waitqueue_head(&state.wait);
for (i = 0; i < state.total_threads; i++) {
/* Fetch latest state.enough earlier */
smp_mb__before_atomic();
if (atomic_read(&state.enough))
break;
atomic_inc(&state.started);
state.infos[i].state = &state;
state.infos[i].thread =
kthread_run(bch_dirty_init_thread, &state.infos[i],
"bch_dirtcnt[%d]", i);
if (IS_ERR(state.infos[i].thread)) {
pr_err("fails to run thread bch_dirty_init[%d]\n", i);
atomic_dec(&state.started);
for (--i; i >= 0; i--)
kthread_stop(state.infos[i].thread);
goto out;
}
}
out:
/* Must wait for all threads to stop. */
wait_event(state.wait, atomic_read(&state.started) == 0);
rw_unlock(0, b);
}
void bch_cached_dev_writeback_init(struct cached_dev *dc)
{
sema_init(&dc->in_flight, 64);
init_rwsem(&dc->writeback_lock);
bch_keybuf_init(&dc->writeback_keys);
dc->writeback_metadata = true;
dc->writeback_running = false;
dc->writeback_consider_fragment = true;
dc->writeback_percent = 10;
dc->writeback_delay = 30;
atomic_long_set(&dc->writeback_rate.rate, 1024);
dc->writeback_rate_minimum = 8;
dc->writeback_rate_update_seconds = WRITEBACK_RATE_UPDATE_SECS_DEFAULT;
dc->writeback_rate_p_term_inverse = 40;
dc->writeback_rate_fp_term_low = 1;
dc->writeback_rate_fp_term_mid = 10;
dc->writeback_rate_fp_term_high = 1000;
dc->writeback_rate_i_term_inverse = 10000;
/* For dc->writeback_lock contention in update_writeback_rate() */
dc->rate_update_retry = 0;
WARN_ON(test_and_clear_bit(BCACHE_DEV_WB_RUNNING, &dc->disk.flags));
INIT_DELAYED_WORK(&dc->writeback_rate_update, update_writeback_rate);
}
int bch_cached_dev_writeback_start(struct cached_dev *dc)
{
dc->writeback_write_wq = alloc_workqueue("bcache_writeback_wq",
WQ_MEM_RECLAIM, 0);
if (!dc->writeback_write_wq)
return -ENOMEM;
cached_dev_get(dc);
dc->writeback_thread = kthread_create(bch_writeback_thread, dc,
"bcache_writeback");
if (IS_ERR(dc->writeback_thread)) {
cached_dev_put(dc);
destroy_workqueue(dc->writeback_write_wq);
return PTR_ERR(dc->writeback_thread);
}
dc->writeback_running = true;
WARN_ON(test_and_set_bit(BCACHE_DEV_WB_RUNNING, &dc->disk.flags));
schedule_delayed_work(&dc->writeback_rate_update,
dc->writeback_rate_update_seconds * HZ);
bch_writeback_queue(dc);
return 0;
}
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