/*
* Primary bucket allocation code
*
* Copyright 2012 Google, Inc.
*
* Allocation in bcache is done in terms of buckets:
*
* Each bucket has associated an 8 bit gen; this gen corresponds to the gen in
* btree pointers - they must match for the pointer to be considered valid.
*
* Thus (assuming a bucket has no dirty data or metadata in it) we can reuse a
* bucket simply by incrementing its gen.
*
* The gens (along with the priorities; it's really the gens are important but
* the code is named as if it's the priorities) are written in an arbitrary list
* of buckets on disk, with a pointer to them in the journal header.
*
* When we invalidate a bucket, we have to write its new gen to disk and wait
* for that write to complete before we use it - otherwise after a crash we
* could have pointers that appeared to be good but pointed to data that had
* been overwritten.
*
* Since the gens and priorities are all stored contiguously on disk, we can
* batch this up: We fill up the free_inc list with freshly invalidated buckets,
* call prio_write(), and when prio_write() finishes we pull buckets off the
* free_inc list and optionally discard them.
*
* free_inc isn't the only freelist - if it was, we'd often to sleep while
* priorities and gens were being written before we could allocate. c->free is a
* smaller freelist, and buckets on that list are always ready to be used.
*
* If we've got discards enabled, that happens when a bucket moves from the
* free_inc list to the free list.
*
* There is another freelist, because sometimes we have buckets that we know
* have nothing pointing into them - these we can reuse without waiting for
* priorities to be rewritten. These come from freed btree nodes and buckets
* that garbage collection discovered no longer had valid keys pointing into
* them (because they were overwritten). That's the unused list - buckets on the
* unused list move to the free list, optionally being discarded in the process.
*
* It's also important to ensure that gens don't wrap around - with respect to
* either the oldest gen in the btree or the gen on disk. This is quite
* difficult to do in practice, but we explicitly guard against it anyways - if
* a bucket is in danger of wrapping around we simply skip invalidating it that
* time around, and we garbage collect or rewrite the priorities sooner than we
* would have otherwise.
*
* bch_bucket_alloc() allocates a single bucket from a specific cache.
*
* bch_bucket_alloc_set() allocates one or more buckets from different caches
* out of a cache set.
*
* free_some_buckets() drives all the processes described above. It's called
* from bch_bucket_alloc() and a few other places that need to make sure free
* buckets are ready.
*
* invalidate_buckets_(lru|fifo)() find buckets that are available to be
* invalidated, and then invalidate them and stick them on the free_inc list -
* in either lru or fifo order.
*/
#include "bcache.h"
#include "btree.h"
#include <linux/random.h>
#define MAX_IN_FLIGHT_DISCARDS 8U
/* Bucket heap / gen */
uint8_t bch_inc_gen(struct cache *ca, struct bucket *b)
{
uint8_t ret = ++b->gen;
ca->set->need_gc = max(ca->set->need_gc, bucket_gc_gen(b));
WARN_ON_ONCE(ca->set->need_gc > BUCKET_GC_GEN_MAX);
if (CACHE_SYNC(&ca->set->sb)) {
ca->need_save_prio = max(ca->need_save_prio,
bucket_disk_gen(b));
WARN_ON_ONCE(ca->need_save_prio > BUCKET_DISK_GEN_MAX);
}
return ret;
}
void bch_rescale_priorities(struct cache_set *c, int sectors)
{
struct cache *ca;
struct bucket *b;
unsigned next = c->nbuckets * c->sb.bucket_size / 1024;
unsigned i;
int r;
atomic_sub(sectors, &c->rescale);
do {
r = atomic_read(&c->rescale);
if (r >= 0)
return;
} while (atomic_cmpxchg(&c->rescale, r, r + next) != r);
mutex_lock(&c->bucket_lock);
c->min_prio = USHRT_MAX;
for_each_cache(ca, c, i)
for_each_bucket(b, ca)
if (b->prio &&
b->prio != BTREE_PRIO &&
!atomic_read(&b->pin)) {
b->prio--;
c->min_prio = min(c->min_prio, b->prio);
}
mutex_unlock(&c->bucket_lock);
}
/* Discard/TRIM */
struct discard {
struct list_head list;
struct work_struct work;
struct cache *ca;
long bucket;
struct bio bio;
struct bio_vec bv;
};
static void discard_finish(struct work_struct *w)
{
struct discard *d = container_of(w, struct discard, work);
struct cache *ca = d->ca;
char buf[BDEVNAME_SIZE];
if (!test_bit(BIO_UPTODATE, &d->bio.bi_flags)) {
pr_notice("discard error on %s, disabling",
bdevname(ca->bdev, buf));
d->ca->discard = 0;
}
mutex_lock(&ca->set->bucket_lock);
fifo_push(&ca->free, d->bucket);
list_add(&d->list, &ca->discards);
atomic_dec(&ca->discards_in_flight);
mutex_unlock(&ca->set->bucket_lock);
closure_wake_up(&ca->set->bucket_wait);
wake_up(&ca->set->alloc_wait);
closure_put(&ca->set->cl);
}
static void discard_endio(struct bio *bio, int error)
{
struct discard *d = container_of(bio, struct discard, bio);
schedule_work(&d->work);
}
static void do_discard(struct cache *ca, long bucket)
{
struct discard *d = list_first_entry(&ca->discards,
struct discard, list);
list_del(&d->list);
d->bucket = bucket;
atomic_inc(&ca->discards_in_flight);
closure_get(&ca->set->cl);
bio_init(&d->bio);
d->bio.bi_sector = bucket_to_sector(ca->set, d->bucket);
d->bio.bi_bdev = ca->bdev;
d->bio.bi_rw = REQ_WRITE|REQ_DISCARD;
d->bio.bi_max_vecs = 1;
d->bio.bi_io_vec = d->bio.bi_inline_vecs;
d->bio.bi_size = bucket_bytes(ca);
d->bio.bi_end_io = discard_endio;
bio_set_prio(&d->bio, IOPRIO_PRIO_VALUE(IOPRIO_CLASS_IDLE, 0));
submit_bio(0, &d->bio);
}
/* Allocation */
static inline bool can_inc_bucket_gen(struct bucket *b)
{
return bucket_gc_gen(b) < BUCKET_GC_GEN_MAX &&
bucket_disk_gen(b) < BUCKET_DISK_GEN_MAX;
}
bool bch_bucket_add_unused(struct cache *ca, struct bucket *b)
{
BUG_ON(GC_MARK(b) || GC_SECTORS_USED(b));
if (fifo_used(&ca->free) > ca->watermark[WATERMARK_MOVINGGC] &&
CACHE_REPLACEMENT(&ca->sb) == CACHE_REPLACEMENT_FIFO)
return false;
b->prio = 0;
if (can_inc_bucket_gen(b) &&
fifo_push(&ca->unused, b - ca->buckets)) {
atomic_inc(&b->pin);
return true;
}
return false;
}
static bool can_invalidate_bucket(struct cache *ca, struct bucket *b)
{
return GC_MARK(b) == GC_MARK_RECLAIMABLE &&
!atomic_read(&b->pin) &&
can_inc_bucket_gen(b);
}
static void invalidate_one_bucket(struct cache *ca, struct bucket *b)
{
bch_inc_gen(ca, b);
b->prio = INITIAL_PRIO;
atomic_inc(&b->pin);
fifo_push(&ca->free_inc, b - ca->buckets);
}
#define bucket_prio(b) \
(((unsigned) (b->prio - ca->set->min_prio)) * GC_SECTORS_USED(b))
#define bucket_max_cmp(l, r) (bucket_prio(l) < bucket_prio(r))
#define bucket_min_cmp(l, r) (bucket_prio(l) > bucket_prio(r))
static void invalidate_buckets_lru(struct cache *ca)
{
struct bucket *b;
ssize_t i;
ca->heap.used = 0;
for_each_bucket(b, ca) {
if (!can_invalidate_bucket(ca, b))
continue;
if (!GC_SECTORS_USED(b)) {
if (!bch_bucket_add_unused(ca, b))
return;
} else {
if (!heap_full(&ca->heap))
heap_add(&ca->heap, b, bucket_max_cmp);
else if (bucket_max_cmp(b, heap_peek(&ca->heap))) {
ca->heap.data[0] = b;
heap_sift(&ca->heap, 0, bucket_max_cmp);
}
}
}
if (ca->heap.used * 2 < ca->heap.size)
bch_queue_gc(ca->set);
for (i = ca->heap.used / 2 - 1; i >= 0; --i)
heap_sift(&ca->heap, i, bucket_min_cmp);
while (!fifo_full(&ca->free_inc)) {
if (!heap_pop(&ca->heap, b, bucket_min_cmp)) {
/* We don't want to be calling invalidate_buckets()
* multiple times when it can't do anything
*/
ca->invalidate_needs_gc = 1;
bch_queue_gc(ca->set);
return;
}
invalidate_one_bucket(ca, b);
}
}
static void invalidate_buckets_fifo(struct cache *ca)
{
struct bucket *b;
size_t checked = 0;
while (!fifo_full(&ca->free_inc)) {
if (ca->fifo_last_bucket < ca->sb.first_bucket ||
ca->fifo_last_bucket >= ca->sb.nbuckets)
ca->fifo_last_bucket = ca->sb.first_bucket;
b = ca->buckets + ca->fifo_last_bucket++;
if (can_invalidate_bucket(ca, b))
invalidate_one_bucket(ca, b);
if (++checked >= ca->sb.nbuckets) {
ca->invalidate_needs_gc = 1;
bch_queue_gc(ca->set);
return;
}
}
}
static void invalidate_buckets_random(struct cache *ca)
{
struct bucket *b;
size_t checked = 0;
while (!fifo_full(&ca->free_inc)) {
size_t n;
get_random_bytes(&n, sizeof(n));
n %= (size_t) (ca->sb.nbuckets - ca->sb.first_bucket);
n += ca->sb.first_bucket;
b = ca->buckets + n;
if (can_invalidate_bucket(ca, b))
invalidate_one_bucket(ca, b);
if (++checked >= ca->sb.nbuckets / 2) {
ca->invalidate_needs_gc = 1;
bch_queue_gc(ca->set);
return;
}
}
}
static void invalidate_buckets(struct cache *ca)
{
if (ca->invalidate_needs_gc)
return;
switch (CACHE_REPLACEMENT(&ca->sb)) {
case CACHE_REPLACEMENT_LRU:
invalidate_buckets_lru(ca);
break;
case CACHE_REPLACEMENT_FIFO:
invalidate_buckets_fifo(ca);
break;
case CACHE_REPLACEMENT_RANDOM:
invalidate_buckets_random(ca);
break;
}
}
#define allocator_wait(ca, cond) \
do { \
DEFINE_WAIT(__wait); \
\
while (!(cond)) { \
prepare_to_wait(&ca->set->alloc_wait, \
&__wait, TASK_INTERRUPTIBLE); \
\
mutex_unlock(&(ca)->set->bucket_lock); \
if (test_bit(CACHE_SET_STOPPING_2, &ca->set->flags)) { \
finish_wait(&ca->set->alloc_wait, &__wait); \
closure_return(cl); \
} \
\
schedule(); \
__set_current_state(TASK_RUNNING); \
mutex_lock(&(ca)->set->bucket_lock); \
} \
\
finish_wait(&ca->set->alloc_wait, &__wait); \
} while (0)
void bch_allocator_thread(struct closure *cl)
{
struct cache *ca = container_of(cl, struct cache, alloc);
mutex_lock(&ca->set->bucket_lock);
while (1) {
while (1) {
long bucket;
if ((!atomic_read(&ca->set->prio_blocked) ||
!CACHE_SYNC(&ca->set->sb)) &&
!fifo_empty(&ca->unused))
fifo_pop(&ca->unused, bucket);
else if (!fifo_empty(&ca->free_inc))
fifo_pop(&ca->free_inc, bucket);
else
break;
allocator_wait(ca, (int) fifo_free(&ca->free) >
atomic_read(&ca->discards_in_flight));
if (ca->discard) {
allocator_wait(ca, !list_empty(&ca->discards));
do_discard(ca, bucket);
} else {
fifo_push(&ca->free, bucket);
closure_wake_up(&ca->set->bucket_wait);
}
}
allocator_wait(ca, ca->set->gc_mark_valid);
invalidate_buckets(ca);
allocator_wait(ca, !atomic_read(&ca->set->prio_blocked) ||
!CACHE_SYNC(&ca->set->sb));
if (CACHE_SYNC(&ca->set->sb) &&
(!fifo_empty(&ca->free_inc) ||
ca->need_save_prio > 64)) {
bch_prio_write(ca);
}
}
}
long bch_bucket_alloc(struct cache *ca, unsigned watermark, struct closure *cl)
{
long r = -1;
again:
wake_up(&ca->set->alloc_wait);
if (fifo_used(&ca->free) > ca->watermark[watermark] &&
fifo_pop(&ca->free, r)) {
struct bucket *b = ca->buckets + r;
#ifdef CONFIG_BCACHE_EDEBUG
size_t iter;
long i;
for (iter = 0; iter < prio_buckets(ca) * 2; iter++)
BUG_ON(ca->prio_buckets[iter] == (uint64_t) r);
fifo_for_each(i, &ca->free, iter)
BUG_ON(i == r);
fifo_for_each(i, &ca->free_inc, iter)
BUG_ON(i == r);
fifo_for_each(i, &ca->unused, iter)
BUG_ON(i == r);
#endif
BUG_ON(atomic_read(&b->pin) != 1);
SET_GC_SECTORS_USED(b, ca->sb.bucket_size);
if (watermark <= WATERMARK_METADATA) {
SET_GC_MARK(b, GC_MARK_METADATA);
b->prio = BTREE_PRIO;
} else {
SET_GC_MARK(b, GC_MARK_RECLAIMABLE);
b->prio = INITIAL_PRIO;
}
return r;
}
pr_debug("alloc failure: blocked %i free %zu free_inc %zu unused %zu",
atomic_read(&ca->set->prio_blocked), fifo_used(&ca->free),
fifo_used(&ca->free_inc), fifo_used(&ca->unused));
if (cl) {
closure_wait(&ca->set->bucket_wait, cl);
if (closure_blocking(cl)) {
mutex_unlock(&ca->set->bucket_lock);
closure_sync(cl);
mutex_lock(&ca->set->bucket_lock);
goto again;
}
}
return -1;
}
void bch_bucket_free(struct cache_set *c, struct bkey *k)
{
unsigned i;
for (i = 0; i < KEY_PTRS(k); i++) {
struct bucket *b = PTR_BUCKET(c, k, i);
SET_GC_MARK(b, 0);
SET_GC_SECTORS_USED(b, 0);
bch_bucket_add_unused(PTR_CACHE(c, k, i), b);
}
}
int __bch_bucket_alloc_set(struct cache_set *c, unsigned watermark,
struct bkey *k, int n, struct closure *cl)
{
int i;
lockdep_assert_held(&c->bucket_lock);
BUG_ON(!n || n > c->caches_loaded || n > 8);
bkey_init(k);
/* sort by free space/prio of oldest data in caches */
for (i = 0; i < n; i++) {
struct cache *ca = c->cache_by_alloc[i];
long b = bch_bucket_alloc(ca, watermark, cl);
if (b == -1)
goto err;
k->ptr[i] = PTR(ca->buckets[b].gen,
bucket_to_sector(c, b),
ca->sb.nr_this_dev);
SET_KEY_PTRS(k, i + 1);
}
return 0;
err:
bch_bucket_free(c, k);
__bkey_put(c, k);
return -1;
}
int bch_bucket_alloc_set(struct cache_set *c, unsigned watermark,
struct bkey *k, int n, struct closure *cl)
{
int ret;
mutex_lock(&c->bucket_lock);
ret = __bch_bucket_alloc_set(c, watermark, k, n, cl);
mutex_unlock(&c->bucket_lock);
return ret;
}
/* Init */
void bch_cache_allocator_exit(struct cache *ca)
{
struct discard *d;
while (!list_empty(&ca->discards)) {
d = list_first_entry(&ca->discards, struct discard, list);
cancel_work_sync(&d->work);
list_del(&d->list);
kfree(d);
}
}
int bch_cache_allocator_init(struct cache *ca)
{
unsigned i;
/*
* Reserve:
* Prio/gen writes first
* Then 8 for btree allocations
* Then half for the moving garbage collector
*/
ca->watermark[WATERMARK_PRIO] = 0;
ca->watermark[WATERMARK_METADATA] = prio_buckets(ca);
ca->watermark[WATERMARK_MOVINGGC] = 8 +
ca->watermark[WATERMARK_METADATA];
ca->watermark[WATERMARK_NONE] = ca->free.size / 2 +
ca->watermark[WATERMARK_MOVINGGC];
for (i = 0; i < MAX_IN_FLIGHT_DISCARDS; i++) {
struct discard *d = kzalloc(sizeof(*d), GFP_KERNEL);
if (!d)
return -ENOMEM;
d->ca = ca;
INIT_WORK(&d->work, discard_finish);
list_add(&d->list, &ca->discards);
}
return 0;
}
