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// SPDX-License-Identifier: GPL-2.0
/*
* Moving/copying garbage collector
*
* Copyright 2012 Google, Inc.
*/
#include "bcachefs.h"
#include "alloc_foreground.h"
#include "btree_iter.h"
#include "btree_update.h"
#include "buckets.h"
#include "clock.h"
#include "disk_groups.h"
#include "extents.h"
#include "eytzinger.h"
#include "io.h"
#include "keylist.h"
#include "move.h"
#include "movinggc.h"
#include "super-io.h"
#include "trace.h"
#include <linux/freezer.h>
#include <linux/kthread.h>
#include <linux/math64.h>
#include <linux/sched/task.h>
#include <linux/sort.h>
#include <linux/wait.h>
/*
* We can't use the entire copygc reserve in one iteration of copygc: we may
* need the buckets we're freeing up to go back into the copygc reserve to make
* forward progress, but if the copygc reserve is full they'll be available for
* any allocation - and it's possible that in a given iteration, we free up most
* of the buckets we're going to free before we allocate most of the buckets
* we're going to allocate.
*
* If we only use half of the reserve per iteration, then in steady state we'll
* always have room in the reserve for the buckets we're going to need in the
* next iteration:
*/
#define COPYGC_BUCKETS_PER_ITER(ca) \
((ca)->free[RESERVE_MOVINGGC].size / 2)
/*
* Max sectors to move per iteration: Have to take into account internal
* fragmentation from the multiple write points for each generation:
*/
#define COPYGC_SECTORS_PER_ITER(ca) \
((ca)->mi.bucket_size * COPYGC_BUCKETS_PER_ITER(ca))
static inline int sectors_used_cmp(copygc_heap *heap,
struct copygc_heap_entry l,
struct copygc_heap_entry r)
{
return cmp_int(l.sectors, r.sectors);
}
static int bucket_offset_cmp(const void *_l, const void *_r, size_t size)
{
const struct copygc_heap_entry *l = _l;
const struct copygc_heap_entry *r = _r;
return cmp_int(l->offset, r->offset);
}
static bool __copygc_pred(struct bch_dev *ca,
struct bkey_s_c k)
{
copygc_heap *h = &ca->copygc_heap;
const struct bch_extent_ptr *ptr =
bch2_bkey_has_device(k, ca->dev_idx);
if (ptr) {
struct copygc_heap_entry search = { .offset = ptr->offset };
ssize_t i = eytzinger0_find_le(h->data, h->used,
sizeof(h->data[0]),
bucket_offset_cmp, &search);
#if 0
/* eytzinger search verify code: */
ssize_t j = -1, k;
for (k = 0; k < h->used; k++)
if (h->data[k].offset <= ptr->offset &&
(j < 0 || h->data[k].offset > h->data[j].offset))
j = k;
BUG_ON(i != j);
#endif
return (i >= 0 &&
ptr->offset < h->data[i].offset + ca->mi.bucket_size &&
ptr->gen == h->data[i].gen);
}
return false;
}
static enum data_cmd copygc_pred(struct bch_fs *c, void *arg,
struct bkey_s_c k,
struct bch_io_opts *io_opts,
struct data_opts *data_opts)
{
struct bch_dev *ca = arg;
if (!__copygc_pred(ca, k))
return DATA_SKIP;
data_opts->target = dev_to_target(ca->dev_idx);
data_opts->btree_insert_flags = BTREE_INSERT_USE_RESERVE;
data_opts->rewrite_dev = ca->dev_idx;
return DATA_REWRITE;
}
static bool have_copygc_reserve(struct bch_dev *ca)
{
bool ret;
spin_lock(&ca->fs->freelist_lock);
ret = fifo_full(&ca->free[RESERVE_MOVINGGC]) ||
ca->allocator_state != ALLOCATOR_RUNNING;
spin_unlock(&ca->fs->freelist_lock);
return ret;
}
static void bch2_copygc(struct bch_fs *c, struct bch_dev *ca)
{
copygc_heap *h = &ca->copygc_heap;
struct copygc_heap_entry e, *i;
struct bucket_array *buckets;
struct bch_move_stats move_stats;
u64 sectors_to_move = 0, sectors_not_moved = 0;
u64 buckets_to_move, buckets_not_moved = 0;
size_t b;
int ret;
memset(&move_stats, 0, sizeof(move_stats));
closure_wait_event(&c->freelist_wait, have_copygc_reserve(ca));
/*
* Find buckets with lowest sector counts, skipping completely
* empty buckets, by building a maxheap sorted by sector count,
* and repeatedly replacing the maximum element until all
* buckets have been visited.
*/
h->used = 0;
/*
* We need bucket marks to be up to date - gc can't be recalculating
* them:
*/
down_read(&c->gc_lock);
down_read(&ca->bucket_lock);
buckets = bucket_array(ca);
for (b = buckets->first_bucket; b < buckets->nbuckets; b++) {
struct bucket_mark m = READ_ONCE(buckets->b[b].mark);
struct copygc_heap_entry e;
if (m.owned_by_allocator ||
m.data_type != BCH_DATA_USER ||
!bucket_sectors_used(m) ||
bucket_sectors_used(m) >= ca->mi.bucket_size)
continue;
e = (struct copygc_heap_entry) {
.gen = m.gen,
.sectors = bucket_sectors_used(m),
.offset = bucket_to_sector(ca, b),
};
heap_add_or_replace(h, e, -sectors_used_cmp, NULL);
}
up_read(&ca->bucket_lock);
up_read(&c->gc_lock);
for (i = h->data; i < h->data + h->used; i++)
sectors_to_move += i->sectors;
while (sectors_to_move > COPYGC_SECTORS_PER_ITER(ca)) {
BUG_ON(!heap_pop(h, e, -sectors_used_cmp, NULL));
sectors_to_move -= e.sectors;
}
buckets_to_move = h->used;
if (!buckets_to_move)
return;
eytzinger0_sort(h->data, h->used,
sizeof(h->data[0]),
bucket_offset_cmp, NULL);
ret = bch2_move_data(c, &ca->copygc_pd.rate,
writepoint_ptr(&ca->copygc_write_point),
POS_MIN, POS_MAX,
copygc_pred, ca,
&move_stats);
down_read(&ca->bucket_lock);
buckets = bucket_array(ca);
for (i = h->data; i < h->data + h->used; i++) {
size_t b = sector_to_bucket(ca, i->offset);
struct bucket_mark m = READ_ONCE(buckets->b[b].mark);
if (i->gen == m.gen && bucket_sectors_used(m)) {
sectors_not_moved += bucket_sectors_used(m);
buckets_not_moved++;
}
}
up_read(&ca->bucket_lock);
if (sectors_not_moved && !ret)
bch_warn_ratelimited(c,
"copygc finished but %llu/%llu sectors, %llu/%llu buckets not moved (move stats: moved %llu sectors, raced %llu keys, %llu sectors)",
sectors_not_moved, sectors_to_move,
buckets_not_moved, buckets_to_move,
atomic64_read(&move_stats.sectors_moved),
atomic64_read(&move_stats.keys_raced),
atomic64_read(&move_stats.sectors_raced));
trace_copygc(ca,
atomic64_read(&move_stats.sectors_moved), sectors_not_moved,
buckets_to_move, buckets_not_moved);
}
/*
* Copygc runs when the amount of fragmented data is above some arbitrary
* threshold:
*
* The threshold at the limit - when the device is full - is the amount of space
* we reserved in bch2_recalc_capacity; we can't have more than that amount of
* disk space stranded due to fragmentation and store everything we have
* promised to store.
*
* But we don't want to be running copygc unnecessarily when the device still
* has plenty of free space - rather, we want copygc to smoothly run every so
* often and continually reduce the amount of fragmented space as the device
* fills up. So, we increase the threshold by half the current free space.
*/
unsigned long bch2_copygc_wait_amount(struct bch_dev *ca)
{
struct bch_fs *c = ca->fs;
struct bch_dev_usage usage = bch2_dev_usage_read(c, ca);
u64 fragmented_allowed = ca->copygc_threshold +
((__dev_buckets_available(ca, usage) * ca->mi.bucket_size) >> 1);
return max_t(s64, 0, fragmented_allowed - usage.sectors_fragmented);
}
static int bch2_copygc_thread(void *arg)
{
struct bch_dev *ca = arg;
struct bch_fs *c = ca->fs;
struct io_clock *clock = &c->io_clock[WRITE];
unsigned long last, wait;
set_freezable();
while (!kthread_should_stop()) {
if (kthread_wait_freezable(c->copy_gc_enabled))
break;
last = atomic_long_read(&clock->now);
wait = bch2_copygc_wait_amount(ca);
if (wait > clock->max_slop) {
bch2_kthread_io_clock_wait(clock, last + wait,
MAX_SCHEDULE_TIMEOUT);
continue;
}
bch2_copygc(c, ca);
}
return 0;
}
void bch2_copygc_stop(struct bch_dev *ca)
{
ca->copygc_pd.rate.rate = UINT_MAX;
bch2_ratelimit_reset(&ca->copygc_pd.rate);
if (ca->copygc_thread) {
kthread_stop(ca->copygc_thread);
put_task_struct(ca->copygc_thread);
}
ca->copygc_thread = NULL;
}
int bch2_copygc_start(struct bch_fs *c, struct bch_dev *ca)
{
struct task_struct *t;
if (ca->copygc_thread)
return 0;
if (c->opts.nochanges)
return 0;
if (bch2_fs_init_fault("copygc_start"))
return -ENOMEM;
t = kthread_create(bch2_copygc_thread, ca,
"bch_copygc[%s]", ca->name);
if (IS_ERR(t))
return PTR_ERR(t);
get_task_struct(t);
ca->copygc_thread = t;
wake_up_process(ca->copygc_thread);
return 0;
}
void bch2_dev_copygc_init(struct bch_dev *ca)
{
bch2_pd_controller_init(&ca->copygc_pd);
ca->copygc_pd.d_term = 0;
}
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