From 2531d9ee61fa08a5a9ab8f002c50779888d232c7 Mon Sep 17 00:00:00 2001 From: Kent Overstreet Date: Mon, 17 Mar 2014 16:55:55 -0700 Subject: [PATCH] bcache: Kill unused freelist This was originally added as at optimization that for various reasons isn't needed anymore, but it does add a lot of nasty corner cases (and it was responsible for some recently fixed bugs). Just get rid of it now. Signed-off-by: Kent Overstreet --- drivers/md/bcache/alloc.c | 140 ++++++++++++++-------------------- drivers/md/bcache/bcache.h | 28 ++----- drivers/md/bcache/btree.c | 41 +++++++++- drivers/md/bcache/btree.h | 2 +- drivers/md/bcache/super.c | 24 +++--- include/trace/events/bcache.h | 6 +- 6 files changed, 112 insertions(+), 129 deletions(-) diff --git a/drivers/md/bcache/alloc.c b/drivers/md/bcache/alloc.c index a59ef6147fc7..443d03fbac47 100644 --- a/drivers/md/bcache/alloc.c +++ b/drivers/md/bcache/alloc.c @@ -78,12 +78,6 @@ uint8_t bch_inc_gen(struct cache *ca, struct bucket *b) 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; } @@ -120,58 +114,46 @@ void bch_rescale_priorities(struct cache_set *c, int sectors) mutex_unlock(&c->bucket_lock); } -/* Allocation */ +/* + * Background allocation thread: scans for buckets to be invalidated, + * invalidates them, rewrites prios/gens (marking them as invalidated on disk), + * then optionally issues discard commands to the newly free buckets, then puts + * them on the various freelists. + */ 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; + return bucket_gc_gen(b) < BUCKET_GC_GEN_MAX; } -bool bch_bucket_add_unused(struct cache *ca, struct bucket *b) +bool bch_can_invalidate_bucket(struct cache *ca, struct bucket *b) { - BUG_ON(GC_MARK(b) || GC_SECTORS_USED(b)); + BUG_ON(!ca->set->gc_mark_valid); - if (CACHE_REPLACEMENT(&ca->sb) == CACHE_REPLACEMENT_FIFO) { - unsigned i; - - for (i = 0; i < RESERVE_NONE; i++) - if (!fifo_full(&ca->free[i])) - goto add; - - return false; - } -add: - 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(b) == GC_MARK_RECLAIMABLE) && !atomic_read(&b->pin) && can_inc_bucket_gen(b); } -static void invalidate_one_bucket(struct cache *ca, struct bucket *b) +void __bch_invalidate_one_bucket(struct cache *ca, struct bucket *b) { - size_t bucket = b - ca->buckets; + lockdep_assert_held(&ca->set->bucket_lock); + BUG_ON(GC_MARK(b) && GC_MARK(b) != GC_MARK_RECLAIMABLE); if (GC_SECTORS_USED(b)) - trace_bcache_invalidate(ca, bucket); + trace_bcache_invalidate(ca, b - ca->buckets); bch_inc_gen(ca, b); b->prio = INITIAL_PRIO; atomic_inc(&b->pin); - fifo_push(&ca->free_inc, bucket); +} + +static void bch_invalidate_one_bucket(struct cache *ca, struct bucket *b) +{ + __bch_invalidate_one_bucket(ca, b); + + fifo_push(&ca->free_inc, b - ca->buckets); } /* @@ -201,20 +183,7 @@ static void invalidate_buckets_lru(struct cache *ca) ca->heap.used = 0; for_each_bucket(b, ca) { - /* - * If we fill up the unused list, if we then return before - * adding anything to the free_inc list we'll skip writing - * prios/gens and just go back to allocating from the unused - * list: - */ - if (fifo_full(&ca->unused)) - return; - - if (!can_invalidate_bucket(ca, b)) - continue; - - if (!GC_SECTORS_USED(b) && - bch_bucket_add_unused(ca, b)) + if (!bch_can_invalidate_bucket(ca, b)) continue; if (!heap_full(&ca->heap)) @@ -239,7 +208,7 @@ static void invalidate_buckets_lru(struct cache *ca) return; } - invalidate_one_bucket(ca, b); + bch_invalidate_one_bucket(ca, b); } } @@ -255,8 +224,8 @@ static void invalidate_buckets_fifo(struct cache *ca) b = ca->buckets + ca->fifo_last_bucket++; - if (can_invalidate_bucket(ca, b)) - invalidate_one_bucket(ca, b); + if (bch_can_invalidate_bucket(ca, b)) + bch_invalidate_one_bucket(ca, b); if (++checked >= ca->sb.nbuckets) { ca->invalidate_needs_gc = 1; @@ -280,8 +249,8 @@ static void invalidate_buckets_random(struct cache *ca) b = ca->buckets + n; - if (can_invalidate_bucket(ca, b)) - invalidate_one_bucket(ca, b); + if (bch_can_invalidate_bucket(ca, b)) + bch_invalidate_one_bucket(ca, b); if (++checked >= ca->sb.nbuckets / 2) { ca->invalidate_needs_gc = 1; @@ -293,8 +262,7 @@ static void invalidate_buckets_random(struct cache *ca) static void invalidate_buckets(struct cache *ca) { - if (ca->invalidate_needs_gc) - return; + BUG_ON(ca->invalidate_needs_gc); switch (CACHE_REPLACEMENT(&ca->sb)) { case CACHE_REPLACEMENT_LRU: @@ -354,17 +322,10 @@ static int bch_allocator_thread(void *arg) * possibly issue discards to them, then we add the bucket to * the free list: */ - while (1) { + while (!fifo_empty(&ca->free_inc)) { 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; + fifo_pop(&ca->free_inc, bucket); if (ca->discard) { mutex_unlock(&ca->set->bucket_lock); @@ -385,9 +346,9 @@ static int bch_allocator_thread(void *arg) * them to the free_inc list: */ +retry_invalidate: allocator_wait(ca, ca->set->gc_mark_valid && - (ca->need_save_prio > 64 || - !ca->invalidate_needs_gc)); + !ca->invalidate_needs_gc); invalidate_buckets(ca); /* @@ -395,13 +356,28 @@ static int bch_allocator_thread(void *arg) * new stuff to them: */ allocator_wait(ca, !atomic_read(&ca->set->prio_blocked)); - if (CACHE_SYNC(&ca->set->sb) && - (!fifo_empty(&ca->free_inc) || - ca->need_save_prio > 64)) + if (CACHE_SYNC(&ca->set->sb)) { + /* + * This could deadlock if an allocation with a btree + * node locked ever blocked - having the btree node + * locked would block garbage collection, but here we're + * waiting on garbage collection before we invalidate + * and free anything. + * + * But this should be safe since the btree code always + * uses btree_check_reserve() before allocating now, and + * if it fails it blocks without btree nodes locked. + */ + if (!fifo_full(&ca->free_inc)) + goto retry_invalidate; + bch_prio_write(ca); + } } } +/* Allocation */ + long bch_bucket_alloc(struct cache *ca, unsigned reserve, bool wait) { DEFINE_WAIT(w); @@ -447,8 +423,6 @@ long bch_bucket_alloc(struct cache *ca, unsigned reserve, bool wait) 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); } b = ca->buckets + r; @@ -470,17 +444,19 @@ long bch_bucket_alloc(struct cache *ca, unsigned reserve, bool wait) return r; } +void __bch_bucket_free(struct cache *ca, struct bucket *b) +{ + SET_GC_MARK(b, 0); + SET_GC_SECTORS_USED(b, 0); +} + 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); - } + for (i = 0; i < KEY_PTRS(k); i++) + __bch_bucket_free(PTR_CACHE(c, k, i), + PTR_BUCKET(c, k, i)); } int __bch_bucket_alloc_set(struct cache_set *c, unsigned reserve, diff --git a/drivers/md/bcache/bcache.h b/drivers/md/bcache/bcache.h index 171cda89cb6b..200efc1b5cf8 100644 --- a/drivers/md/bcache/bcache.h +++ b/drivers/md/bcache/bcache.h @@ -195,7 +195,6 @@ struct bucket { atomic_t pin; uint16_t prio; uint8_t gen; - uint8_t disk_gen; uint8_t last_gc; /* Most out of date gen in the btree */ uint8_t gc_gen; uint16_t gc_mark; /* Bitfield used by GC. See below for field */ @@ -426,14 +425,9 @@ struct cache { * their new gen to disk. After prio_write() finishes writing the new * gens/prios, they'll be moved to the free list (and possibly discarded * in the process) - * - * unused: GC found nothing pointing into these buckets (possibly - * because all the data they contained was overwritten), so we only - * need to discard them before they can be moved to the free list. */ DECLARE_FIFO(long, free)[RESERVE_NR]; DECLARE_FIFO(long, free_inc); - DECLARE_FIFO(long, unused); size_t fifo_last_bucket; @@ -442,12 +436,6 @@ struct cache { DECLARE_HEAP(struct bucket *, heap); - /* - * max(gen - disk_gen) for all buckets. When it gets too big we have to - * call prio_write() to keep gens from wrapping. - */ - uint8_t need_save_prio; - /* * If nonzero, we know we aren't going to find any buckets to invalidate * until a gc finishes - otherwise we could pointlessly burn a ton of @@ -848,9 +836,6 @@ static inline bool cached_dev_get(struct cached_dev *dc) /* * bucket_gc_gen() returns the difference between the bucket's current gen and * the oldest gen of any pointer into that bucket in the btree (last_gc). - * - * bucket_disk_gen() returns the difference between the current gen and the gen - * on disk; they're both used to make sure gens don't wrap around. */ static inline uint8_t bucket_gc_gen(struct bucket *b) @@ -858,13 +843,7 @@ static inline uint8_t bucket_gc_gen(struct bucket *b) return b->gen - b->last_gc; } -static inline uint8_t bucket_disk_gen(struct bucket *b) -{ - return b->gen - b->disk_gen; -} - #define BUCKET_GC_GEN_MAX 96U -#define BUCKET_DISK_GEN_MAX 64U #define kobj_attribute_write(n, fn) \ static struct kobj_attribute ksysfs_##n = __ATTR(n, S_IWUSR, NULL, fn) @@ -897,11 +876,14 @@ void bch_submit_bbio(struct bio *, struct cache_set *, struct bkey *, unsigned); uint8_t bch_inc_gen(struct cache *, struct bucket *); void bch_rescale_priorities(struct cache_set *, int); -bool bch_bucket_add_unused(struct cache *, struct bucket *); -long bch_bucket_alloc(struct cache *, unsigned, bool); +bool bch_can_invalidate_bucket(struct cache *, struct bucket *); +void __bch_invalidate_one_bucket(struct cache *, struct bucket *); + +void __bch_bucket_free(struct cache *, struct bucket *); void bch_bucket_free(struct cache_set *, struct bkey *); +long bch_bucket_alloc(struct cache *, unsigned, bool); int __bch_bucket_alloc_set(struct cache_set *, unsigned, struct bkey *, int, bool); int bch_bucket_alloc_set(struct cache_set *, unsigned, diff --git a/drivers/md/bcache/btree.c b/drivers/md/bcache/btree.c index be90596a9e2a..4c340c85b122 100644 --- a/drivers/md/bcache/btree.c +++ b/drivers/md/bcache/btree.c @@ -1641,7 +1641,7 @@ static void btree_gc_start(struct cache_set *c) mutex_unlock(&c->bucket_lock); } -size_t bch_btree_gc_finish(struct cache_set *c) +static size_t bch_btree_gc_finish(struct cache_set *c) { size_t available = 0; struct bucket *b; @@ -1703,9 +1703,6 @@ size_t bch_btree_gc_finish(struct cache_set *c) if (!GC_MARK(b) || GC_MARK(b) == GC_MARK_RECLAIMABLE) available++; - - if (!GC_MARK(b)) - bch_bucket_add_unused(ca, b); } } @@ -1836,6 +1833,42 @@ int bch_btree_check(struct cache_set *c) return btree_root(check_recurse, c, &op); } +void bch_initial_gc_finish(struct cache_set *c) +{ + struct cache *ca; + struct bucket *b; + unsigned i; + + bch_btree_gc_finish(c); + + mutex_lock(&c->bucket_lock); + + /* + * We need to put some unused buckets directly on the prio freelist in + * order to get the allocator thread started - it needs freed buckets in + * order to rewrite the prios and gens, and it needs to rewrite prios + * and gens in order to free buckets. + * + * This is only safe for buckets that have no live data in them, which + * there should always be some of. + */ + for_each_cache(ca, c, i) { + for_each_bucket(b, ca) { + if (fifo_full(&ca->free[RESERVE_PRIO])) + break; + + if (bch_can_invalidate_bucket(ca, b) && + !GC_MARK(b)) { + __bch_invalidate_one_bucket(ca, b); + fifo_push(&ca->free[RESERVE_PRIO], + b - ca->buckets); + } + } + } + + mutex_unlock(&c->bucket_lock); +} + /* Btree insertion */ static bool btree_insert_key(struct btree *b, struct bkey *k, diff --git a/drivers/md/bcache/btree.h b/drivers/md/bcache/btree.h index 3ce371fa7f98..91dfa5e69685 100644 --- a/drivers/md/bcache/btree.h +++ b/drivers/md/bcache/btree.h @@ -252,7 +252,7 @@ int bch_btree_insert(struct cache_set *, struct keylist *, atomic_t *, struct bkey *); int bch_gc_thread_start(struct cache_set *); -size_t bch_btree_gc_finish(struct cache_set *); +void bch_initial_gc_finish(struct cache_set *); void bch_moving_gc(struct cache_set *); int bch_btree_check(struct cache_set *); void bch_initial_mark_key(struct cache_set *, int, struct bkey *); diff --git a/drivers/md/bcache/super.c b/drivers/md/bcache/super.c index 2d4a56219ec7..a8c57d59a726 100644 --- a/drivers/md/bcache/super.c +++ b/drivers/md/bcache/super.c @@ -541,9 +541,6 @@ static void prio_io(struct cache *ca, uint64_t bucket, unsigned long rw) closure_sync(cl); } -#define buckets_free(c) "free %zu, free_inc %zu, unused %zu", \ - fifo_used(&c->free), fifo_used(&c->free_inc), fifo_used(&c->unused) - void bch_prio_write(struct cache *ca) { int i; @@ -554,10 +551,6 @@ void bch_prio_write(struct cache *ca) lockdep_assert_held(&ca->set->bucket_lock); - for (b = ca->buckets; - b < ca->buckets + ca->sb.nbuckets; b++) - b->disk_gen = b->gen; - ca->disk_buckets->seq++; atomic_long_add(ca->sb.bucket_size * prio_buckets(ca), @@ -601,14 +594,17 @@ void bch_prio_write(struct cache *ca) mutex_lock(&ca->set->bucket_lock); - ca->need_save_prio = 0; - /* * Don't want the old priorities to get garbage collected until after we * finish writing the new ones, and they're journalled */ - for (i = 0; i < prio_buckets(ca); i++) + for (i = 0; i < prio_buckets(ca); i++) { + if (ca->prio_last_buckets[i]) + __bch_bucket_free(ca, + &ca->buckets[ca->prio_last_buckets[i]]); + ca->prio_last_buckets[i] = ca->prio_buckets[i]; + } } static void prio_read(struct cache *ca, uint64_t bucket) @@ -639,7 +635,7 @@ static void prio_read(struct cache *ca, uint64_t bucket) } b->prio = le16_to_cpu(d->prio); - b->gen = b->disk_gen = b->last_gc = b->gc_gen = d->gen; + b->gen = b->last_gc = b->gc_gen = d->gen; } } @@ -1606,7 +1602,7 @@ static void run_cache_set(struct cache_set *c) goto err; bch_journal_mark(c, &journal); - bch_btree_gc_finish(c); + bch_initial_gc_finish(c); pr_debug("btree_check() done"); /* @@ -1648,7 +1644,7 @@ static void run_cache_set(struct cache_set *c) ca->sb.d[j] = ca->sb.first_bucket + j; } - bch_btree_gc_finish(c); + bch_initial_gc_finish(c); err = "error starting allocator thread"; for_each_cache(ca, c, i) @@ -1794,7 +1790,6 @@ void bch_cache_release(struct kobject *kobj) vfree(ca->buckets); free_heap(&ca->heap); - free_fifo(&ca->unused); free_fifo(&ca->free_inc); for (i = 0; i < RESERVE_NR; i++) @@ -1831,7 +1826,6 @@ static int cache_alloc(struct cache_sb *sb, struct cache *ca) !init_fifo(&ca->free[RESERVE_MOVINGGC], free, GFP_KERNEL) || !init_fifo(&ca->free[RESERVE_NONE], free, GFP_KERNEL) || !init_fifo(&ca->free_inc, free << 2, GFP_KERNEL) || - !init_fifo(&ca->unused, free << 2, GFP_KERNEL) || !init_heap(&ca->heap, free << 3, GFP_KERNEL) || !(ca->buckets = vzalloc(sizeof(struct bucket) * ca->sb.nbuckets)) || diff --git a/include/trace/events/bcache.h b/include/trace/events/bcache.h index 8fc2a7134d3c..c9c3c044b32f 100644 --- a/include/trace/events/bcache.h +++ b/include/trace/events/bcache.h @@ -446,7 +446,6 @@ TRACE_EVENT(bcache_alloc_fail, __field(dev_t, dev ) __field(unsigned, free ) __field(unsigned, free_inc ) - __field(unsigned, unused ) __field(unsigned, blocked ) ), @@ -454,13 +453,12 @@ TRACE_EVENT(bcache_alloc_fail, __entry->dev = ca->bdev->bd_dev; __entry->free = fifo_used(&ca->free[reserve]); __entry->free_inc = fifo_used(&ca->free_inc); - __entry->unused = fifo_used(&ca->unused); __entry->blocked = atomic_read(&ca->set->prio_blocked); ), - TP_printk("alloc fail %d,%d free %u free_inc %u unused %u blocked %u", + TP_printk("alloc fail %d,%d free %u free_inc %u blocked %u", MAJOR(__entry->dev), MINOR(__entry->dev), __entry->free, - __entry->free_inc, __entry->unused, __entry->blocked) + __entry->free_inc, __entry->blocked) ); /* Background writeback */ -- GitLab