/* SPDX-License-Identifier: GPL-2.0 */ #ifndef _BCACHEFS_JOURNAL_H #define _BCACHEFS_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 * bch2_btree_insert() or bch_btree_insert_node(), which then pass that parameter * down to the journalling code. That closure 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" struct bch_fs; static inline void journal_wake(struct journal *j) { … } static inline struct journal_buf *journal_cur_buf(struct journal *j) { … } /* Sequence number of oldest dirty journal entry */ static inline u64 journal_last_seq(struct journal *j) { … } static inline u64 journal_cur_seq(struct journal *j) { … } static inline u64 journal_last_unwritten_seq(struct journal *j) { … } static inline int journal_state_count(union journal_res_state s, int idx) { … } static inline void journal_state_inc(union journal_res_state *s) { … } /* * 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) { … } static inline int journal_entry_overhead(struct journal *j) { … } static inline struct jset_entry * bch2_journal_add_entry_noreservation(struct journal_buf *buf, size_t u64s) { … } static inline struct jset_entry * journal_res_entry(struct journal *j, struct journal_res *res) { … } static inline unsigned journal_entry_init(struct jset_entry *entry, unsigned type, enum btree_id id, unsigned level, unsigned u64s) { … } static inline unsigned journal_entry_set(struct jset_entry *entry, unsigned type, enum btree_id id, unsigned level, const void *data, unsigned u64s) { … } static inline struct jset_entry * bch2_journal_add_entry(struct journal *j, struct journal_res *res, unsigned type, enum btree_id id, unsigned level, unsigned u64s) { … } static inline bool journal_entry_empty(struct jset *j) { … } /* * Drop reference on a buffer index and return true if the count has hit zero. */ static inline union journal_res_state journal_state_buf_put(struct journal *j, unsigned idx) { … } bool bch2_journal_entry_close(struct journal *); void bch2_journal_do_writes(struct journal *); void bch2_journal_buf_put_final(struct journal *, u64); static inline void __bch2_journal_buf_put(struct journal *j, unsigned idx, u64 seq) { … } static inline void bch2_journal_buf_put(struct journal *j, unsigned idx, u64 seq) { … } /* * This function releases the journal write structure so other threads can * then proceed to add their keys as well. */ static inline void bch2_journal_res_put(struct journal *j, struct journal_res *res) { … } int bch2_journal_res_get_slowpath(struct journal *, struct journal_res *, unsigned); /* First bits for BCH_WATERMARK: */ enum journal_res_flags { … }; #define JOURNAL_RES_GET_NONBLOCK … #define JOURNAL_RES_GET_CHECK … static inline int journal_res_get_fast(struct journal *j, struct journal_res *res, unsigned flags) { … } static inline int bch2_journal_res_get(struct journal *j, struct journal_res *res, unsigned u64s, unsigned flags) { … } /* journal_entry_res: */ void bch2_journal_entry_res_resize(struct journal *, struct journal_entry_res *, unsigned); int bch2_journal_flush_seq_async(struct journal *, u64, struct closure *); void bch2_journal_flush_async(struct journal *, struct closure *); int bch2_journal_flush_seq(struct journal *, u64); int bch2_journal_flush(struct journal *); bool bch2_journal_noflush_seq(struct journal *, u64); int bch2_journal_meta(struct journal *); void bch2_journal_halt(struct journal *); static inline int bch2_journal_error(struct journal *j) { … } struct bch_dev; static inline void bch2_journal_set_replay_done(struct journal *j) { … } void bch2_journal_unblock(struct journal *); void bch2_journal_block(struct journal *); struct journal_buf *bch2_next_write_buffer_flush_journal_buf(struct journal *j, u64 max_seq); void __bch2_journal_debug_to_text(struct printbuf *, struct journal *); void bch2_journal_debug_to_text(struct printbuf *, struct journal *); void bch2_journal_pins_to_text(struct printbuf *, struct journal *); bool bch2_journal_seq_pins_to_text(struct printbuf *, struct journal *, u64 *); int bch2_set_nr_journal_buckets(struct bch_fs *, struct bch_dev *, unsigned nr); int bch2_dev_journal_alloc(struct bch_dev *, bool); int bch2_fs_journal_alloc(struct bch_fs *); void bch2_dev_journal_stop(struct journal *, struct bch_dev *); void bch2_fs_journal_stop(struct journal *); int bch2_fs_journal_start(struct journal *, u64); void bch2_dev_journal_exit(struct bch_dev *); int bch2_dev_journal_init(struct bch_dev *, struct bch_sb *); void bch2_fs_journal_exit(struct journal *); int bch2_fs_journal_init(struct journal *); #endif /* _BCACHEFS_JOURNAL_H */
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