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