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Diffstat (limited to 'libbcache/journal.h')
| -rw-r--r-- | libbcache/journal.h | 387 |
1 files changed, 387 insertions, 0 deletions
diff --git a/libbcache/journal.h b/libbcache/journal.h new file mode 100644 index 0000000..759ed60 --- /dev/null +++ b/libbcache/journal.h @@ -0,0 +1,387 @@ +#ifndef _BCACHE_JOURNAL_H +#define _BCACHE_JOURNAL_H + +/* + * THE JOURNAL: + * + * The primary purpose of the journal is to log updates (insertions) to the + * b-tree, to avoid having to do synchronous updates to the b-tree on disk. + * + * Without the journal, the b-tree is always internally consistent on + * disk - and in fact, in the earliest incarnations bcache didn't have a journal + * but did handle unclean shutdowns by doing all index updates synchronously + * (with coalescing). + * + * Updates to interior nodes still happen synchronously and without the journal + * (for simplicity) - this may change eventually but updates to interior nodes + * are rare enough it's not a huge priority. + * + * This means the journal is relatively separate from the b-tree; it consists of + * just a list of keys and journal replay consists of just redoing those + * insertions in same order that they appear in the journal. + * + * PERSISTENCE: + * + * For synchronous updates (where we're waiting on the index update to hit + * disk), the journal entry will be written out immediately (or as soon as + * possible, if the write for the previous journal entry was still in flight). + * + * Synchronous updates are specified by passing a closure (@flush_cl) to + * bch_btree_insert() or bch_btree_insert_node(), which then pass that parameter + * down to the journalling code. That closure will will wait on the journal + * write to complete (via closure_wait()). + * + * If the index update wasn't synchronous, the journal entry will be + * written out after 10 ms have elapsed, by default (the delay_ms field + * in struct journal). + * + * JOURNAL ENTRIES: + * + * A journal entry is variable size (struct jset), it's got a fixed length + * header and then a variable number of struct jset_entry entries. + * + * Journal entries are identified by monotonically increasing 64 bit sequence + * numbers - jset->seq; other places in the code refer to this sequence number. + * + * A jset_entry entry contains one or more bkeys (which is what gets inserted + * into the b-tree). We need a container to indicate which b-tree the key is + * for; also, the roots of the various b-trees are stored in jset_entry entries + * (one for each b-tree) - this lets us add new b-tree types without changing + * the on disk format. + * + * We also keep some things in the journal header that are logically part of the + * superblock - all the things that are frequently updated. This is for future + * bcache on raw flash support; the superblock (which will become another + * journal) can't be moved or wear leveled, so it contains just enough + * information to find the main journal, and the superblock only has to be + * rewritten when we want to move/wear level the main journal. + * + * JOURNAL LAYOUT ON DISK: + * + * The journal is written to a ringbuffer of buckets (which is kept in the + * superblock); the individual buckets are not necessarily contiguous on disk + * which means that journal entries are not allowed to span buckets, but also + * that we can resize the journal at runtime if desired (unimplemented). + * + * The journal buckets exist in the same pool as all the other buckets that are + * managed by the allocator and garbage collection - garbage collection marks + * the journal buckets as metadata buckets. + * + * OPEN/DIRTY JOURNAL ENTRIES: + * + * Open/dirty journal entries are journal entries that contain b-tree updates + * that have not yet been written out to the b-tree on disk. We have to track + * which journal entries are dirty, and we also have to avoid wrapping around + * the journal and overwriting old but still dirty journal entries with new + * journal entries. + * + * On disk, this is represented with the "last_seq" field of struct jset; + * last_seq is the first sequence number that journal replay has to replay. + * + * To avoid overwriting dirty journal entries on disk, we keep a mapping (in + * journal_device->seq) of for each journal bucket, the highest sequence number + * any journal entry it contains. Then, by comparing that against last_seq we + * can determine whether that journal bucket contains dirty journal entries or + * not. + * + * To track which journal entries are dirty, we maintain a fifo of refcounts + * (where each entry corresponds to a specific sequence number) - when a ref + * goes to 0, that journal entry is no longer dirty. + * + * Journalling of index updates is done at the same time as the b-tree itself is + * being modified (see btree_insert_key()); when we add the key to the journal + * the pending b-tree write takes a ref on the journal entry the key was added + * to. If a pending b-tree write would need to take refs on multiple dirty + * journal entries, it only keeps the ref on the oldest one (since a newer + * journal entry will still be replayed if an older entry was dirty). + * + * JOURNAL FILLING UP: + * + * There are two ways the journal could fill up; either we could run out of + * space to write to, or we could have too many open journal entries and run out + * of room in the fifo of refcounts. Since those refcounts are decremented + * without any locking we can't safely resize that fifo, so we handle it the + * same way. + * + * If the journal fills up, we start flushing dirty btree nodes until we can + * allocate space for a journal write again - preferentially flushing btree + * nodes that are pinning the oldest journal entries first. + */ + +#include <linux/hash.h> + +#include "journal_types.h" + +static inline struct jset_entry *jset_keys_next(struct jset_entry *j) +{ + return (void *) __bkey_idx(j, le16_to_cpu(j->u64s)); +} + +/* + * Only used for holding the journal entries we read in btree_journal_read() + * during cache_registration + */ +struct journal_replay { + struct list_head list; + struct jset j; +}; + +#define JOURNAL_PIN ((32 * 1024) - 1) + +static inline bool journal_pin_active(struct journal_entry_pin *pin) +{ + return pin->pin_list != NULL; +} + +void bch_journal_pin_add(struct journal *, struct journal_entry_pin *, + journal_pin_flush_fn); +void bch_journal_pin_drop(struct journal *, struct journal_entry_pin *); +void bch_journal_pin_add_if_older(struct journal *, + struct journal_entry_pin *, + struct journal_entry_pin *, + journal_pin_flush_fn); + +struct closure; +struct cache_set; +struct keylist; + +struct bkey_i *bch_journal_find_btree_root(struct cache_set *, struct jset *, + enum btree_id, unsigned *); + +int bch_journal_seq_should_ignore(struct cache_set *, u64, struct btree *); + +u64 bch_inode_journal_seq(struct journal *, u64); + +static inline int journal_state_count(union journal_res_state s, int idx) +{ + return idx == 0 ? s.buf0_count : s.buf1_count; +} + +static inline void journal_state_inc(union journal_res_state *s) +{ + s->buf0_count += s->idx == 0; + s->buf1_count += s->idx == 1; +} + +static inline void bch_journal_set_has_inode(struct journal_buf *buf, u64 inum) +{ + set_bit(hash_64(inum, ilog2(sizeof(buf->has_inode) * 8)), buf->has_inode); +} + +/* + * Amount of space that will be taken up by some keys in the journal (i.e. + * including the jset header) + */ +static inline unsigned jset_u64s(unsigned u64s) +{ + return u64s + sizeof(struct jset_entry) / sizeof(u64); +} + +static inline void bch_journal_add_entry_at(struct journal_buf *buf, + const void *data, size_t u64s, + unsigned type, enum btree_id id, + unsigned level, unsigned offset) +{ + struct jset_entry *entry = bkey_idx(buf->data, offset); + + entry->u64s = cpu_to_le16(u64s); + entry->btree_id = id; + entry->level = level; + entry->flags = 0; + SET_JOURNAL_ENTRY_TYPE(entry, type); + + memcpy_u64s(entry->_data, data, u64s); +} + +static inline void bch_journal_add_keys(struct journal *j, struct journal_res *res, + enum btree_id id, const struct bkey_i *k) +{ + struct journal_buf *buf = &j->buf[res->idx]; + unsigned actual = jset_u64s(k->k.u64s); + + EBUG_ON(!res->ref); + BUG_ON(actual > res->u64s); + + bch_journal_set_has_inode(buf, k->k.p.inode); + + bch_journal_add_entry_at(buf, k, k->k.u64s, + JOURNAL_ENTRY_BTREE_KEYS, id, + 0, res->offset); + + res->offset += actual; + res->u64s -= actual; +} + +void bch_journal_buf_put_slowpath(struct journal *, bool); + +static inline void bch_journal_buf_put(struct journal *j, unsigned idx, + bool need_write_just_set) +{ + union journal_res_state s; + + s.v = atomic64_sub_return(((union journal_res_state) { + .buf0_count = idx == 0, + .buf1_count = idx == 1, + }).v, &j->reservations.counter); + + EBUG_ON(s.idx != idx && !s.prev_buf_unwritten); + + /* + * Do not initiate a journal write if the journal is in an error state + * (previous journal entry write may have failed) + */ + if (s.idx != idx && + !journal_state_count(s, idx) && + s.cur_entry_offset != JOURNAL_ENTRY_ERROR_VAL) + bch_journal_buf_put_slowpath(j, need_write_just_set); +} + +/* + * This function releases the journal write structure so other threads can + * then proceed to add their keys as well. + */ +static inline void bch_journal_res_put(struct journal *j, + struct journal_res *res) +{ + if (!res->ref) + return; + + lock_release(&j->res_map, 0, _RET_IP_); + + while (res->u64s) { + bch_journal_add_entry_at(&j->buf[res->idx], NULL, 0, + JOURNAL_ENTRY_BTREE_KEYS, + 0, 0, res->offset); + res->offset += jset_u64s(0); + res->u64s -= jset_u64s(0); + } + + bch_journal_buf_put(j, res->idx, false); + + res->ref = 0; +} + +int bch_journal_res_get_slowpath(struct journal *, struct journal_res *, + unsigned, unsigned); + +static inline int journal_res_get_fast(struct journal *j, + struct journal_res *res, + unsigned u64s_min, + unsigned u64s_max) +{ + union journal_res_state old, new; + u64 v = atomic64_read(&j->reservations.counter); + + do { + old.v = new.v = v; + + /* + * Check if there is still room in the current journal + * entry: + */ + if (old.cur_entry_offset + u64s_min > j->cur_entry_u64s) + return 0; + + res->offset = old.cur_entry_offset; + res->u64s = min(u64s_max, j->cur_entry_u64s - + old.cur_entry_offset); + + journal_state_inc(&new); + new.cur_entry_offset += res->u64s; + } while ((v = atomic64_cmpxchg(&j->reservations.counter, + old.v, new.v)) != old.v); + + res->ref = true; + res->idx = new.idx; + res->seq = le64_to_cpu(j->buf[res->idx].data->seq); + return 1; +} + +static inline int bch_journal_res_get(struct journal *j, struct journal_res *res, + unsigned u64s_min, unsigned u64s_max) +{ + int ret; + + EBUG_ON(res->ref); + EBUG_ON(u64s_max < u64s_min); + + if (journal_res_get_fast(j, res, u64s_min, u64s_max)) + goto out; + + ret = bch_journal_res_get_slowpath(j, res, u64s_min, u64s_max); + if (ret) + return ret; +out: + lock_acquire_shared(&j->res_map, 0, 0, NULL, _THIS_IP_); + EBUG_ON(!res->ref); + return 0; +} + +void bch_journal_wait_on_seq(struct journal *, u64, struct closure *); +void bch_journal_flush_seq_async(struct journal *, u64, struct closure *); +void bch_journal_flush_async(struct journal *, struct closure *); +void bch_journal_meta_async(struct journal *, struct closure *); + +int bch_journal_flush_seq(struct journal *, u64); +int bch_journal_flush(struct journal *); +int bch_journal_meta(struct journal *); + +void bch_journal_halt(struct journal *); + +static inline int bch_journal_error(struct journal *j) +{ + return j->reservations.cur_entry_offset == JOURNAL_ENTRY_ERROR_VAL + ? -EIO : 0; +} + +static inline bool is_journal_device(struct cache *ca) +{ + return ca->mi.state == CACHE_ACTIVE && ca->mi.tier == 0; +} + +static inline bool journal_flushes_device(struct cache *ca) +{ + return true; +} + +void bch_journal_start(struct cache_set *); +void bch_journal_mark(struct cache_set *, struct list_head *); +void bch_journal_entries_free(struct list_head *); +int bch_journal_read(struct cache_set *, struct list_head *); +int bch_journal_replay(struct cache_set *, struct list_head *); + +static inline void bch_journal_set_replay_done(struct journal *j) +{ + spin_lock(&j->lock); + BUG_ON(!test_bit(JOURNAL_STARTED, &j->flags)); + + set_bit(JOURNAL_REPLAY_DONE, &j->flags); + j->cur_pin_list = &fifo_peek_back(&j->pin); + spin_unlock(&j->lock); +} + +void bch_journal_free(struct journal *); +int bch_journal_alloc(struct journal *, unsigned); + +ssize_t bch_journal_print_debug(struct journal *, char *); + +int bch_cache_journal_alloc(struct cache *); + +static inline __le64 *__journal_buckets(struct cache_sb *sb) +{ + return sb->_data + bch_journal_buckets_offset(sb); +} + +static inline u64 journal_bucket(struct cache_sb *sb, unsigned nr) +{ + return le64_to_cpu(__journal_buckets(sb)[nr]); +} + +static inline void set_journal_bucket(struct cache_sb *sb, unsigned nr, u64 bucket) +{ + __journal_buckets(sb)[nr] = cpu_to_le64(bucket); +} + +int bch_journal_move(struct cache *); + +#endif /* _BCACHE_JOURNAL_H */ |