--- /dev/null
+/* 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)
+{
+ wake_up(&j->wait);
+ closure_wake_up(&j->async_wait);
+}
+
+static inline struct journal_buf *journal_cur_buf(struct journal *j)
+{
+ return j->buf + j->reservations.idx;
+}
+
+/* Sequence number of oldest dirty journal entry */
+
+static inline u64 journal_last_seq(struct journal *j)
+{
+ return j->pin.front;
+}
+
+static inline u64 journal_cur_seq(struct journal *j)
+{
+ return atomic64_read(&j->seq);
+}
+
+static inline u64 journal_last_unwritten_seq(struct journal *j)
+{
+ return j->seq_ondisk + 1;
+}
+
+static inline int journal_state_count(union journal_res_state s, int idx)
+{
+ switch (idx) {
+ case 0: return s.buf0_count;
+ case 1: return s.buf1_count;
+ case 2: return s.buf2_count;
+ case 3: return s.buf3_count;
+ }
+ BUG();
+}
+
+static inline void journal_state_inc(union journal_res_state *s)
+{
+ s->buf0_count += s->idx == 0;
+ s->buf1_count += s->idx == 1;
+ s->buf2_count += s->idx == 2;
+ s->buf3_count += s->idx == 3;
+}
+
+/*
+ * 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 int journal_entry_overhead(struct journal *j)
+{
+ return sizeof(struct jset) / sizeof(u64) + j->entry_u64s_reserved;
+}
+
+static inline struct jset_entry *
+bch2_journal_add_entry_noreservation(struct journal_buf *buf, size_t u64s)
+{
+ struct jset *jset = buf->data;
+ struct jset_entry *entry = vstruct_idx(jset, le32_to_cpu(jset->u64s));
+
+ memset(entry, 0, sizeof(*entry));
+ entry->u64s = cpu_to_le16(u64s);
+
+ le32_add_cpu(&jset->u64s, jset_u64s(u64s));
+
+ return entry;
+}
+
+static inline struct jset_entry *
+journal_res_entry(struct journal *j, struct journal_res *res)
+{
+ return vstruct_idx(j->buf[res->idx].data, res->offset);
+}
+
+static inline unsigned journal_entry_init(struct jset_entry *entry, unsigned type,
+ enum btree_id id, unsigned level,
+ unsigned u64s)
+{
+ entry->u64s = cpu_to_le16(u64s);
+ entry->btree_id = id;
+ entry->level = level;
+ entry->type = type;
+ entry->pad[0] = 0;
+ entry->pad[1] = 0;
+ entry->pad[2] = 0;
+ return jset_u64s(u64s);
+}
+
+static inline unsigned journal_entry_set(struct jset_entry *entry, unsigned type,
+ enum btree_id id, unsigned level,
+ const void *data, unsigned u64s)
+{
+ unsigned ret = journal_entry_init(entry, type, id, level, u64s);
+
+ memcpy_u64s_small(entry->_data, data, u64s);
+ return ret;
+}
+
+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)
+{
+ struct jset_entry *entry = journal_res_entry(j, res);
+ unsigned actual = journal_entry_init(entry, type, id, level, u64s);
+
+ EBUG_ON(!res->ref);
+ EBUG_ON(actual > res->u64s);
+
+ res->offset += actual;
+ res->u64s -= actual;
+ return entry;
+}
+
+static inline bool journal_entry_empty(struct jset *j)
+{
+ if (j->seq != j->last_seq)
+ return false;
+
+ vstruct_for_each(j, i)
+ if (i->type == BCH_JSET_ENTRY_btree_keys && i->u64s)
+ return false;
+ return true;
+}
+
+/*
+ * 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)
+{
+ union journal_res_state s;
+
+ s.v = atomic64_sub_return(((union journal_res_state) {
+ .buf0_count = idx == 0,
+ .buf1_count = idx == 1,
+ .buf2_count = idx == 2,
+ .buf3_count = idx == 3,
+ }).v, &j->reservations.counter);
+ return s;
+}
+
+bool bch2_journal_entry_close(struct journal *);
+void bch2_journal_buf_put_final(struct journal *, u64, bool);
+
+static inline void __bch2_journal_buf_put(struct journal *j, unsigned idx, u64 seq)
+{
+ union journal_res_state s;
+
+ s = journal_state_buf_put(j, idx);
+ if (!journal_state_count(s, idx))
+ bch2_journal_buf_put_final(j, seq, idx == s.unwritten_idx);
+}
+
+static inline void bch2_journal_buf_put(struct journal *j, unsigned idx, u64 seq)
+{
+ union journal_res_state s;
+
+ s = journal_state_buf_put(j, idx);
+ if (!journal_state_count(s, idx)) {
+ spin_lock(&j->lock);
+ bch2_journal_buf_put_final(j, seq, idx == s.unwritten_idx);
+ spin_unlock(&j->lock);
+ }
+}
+
+/*
+ * 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)
+{
+ if (!res->ref)
+ return;
+
+ lock_release(&j->res_map, _THIS_IP_);
+
+ while (res->u64s)
+ bch2_journal_add_entry(j, res,
+ BCH_JSET_ENTRY_btree_keys,
+ 0, 0, 0);
+
+ bch2_journal_buf_put(j, res->idx, res->seq);
+
+ res->ref = 0;
+}
+
+int bch2_journal_res_get_slowpath(struct journal *, struct journal_res *,
+ unsigned);
+
+/* First bits for BCH_WATERMARK: */
+enum journal_res_flags {
+ __JOURNAL_RES_GET_NONBLOCK = BCH_WATERMARK_BITS,
+ __JOURNAL_RES_GET_CHECK,
+};
+
+#define JOURNAL_RES_GET_NONBLOCK (1 << __JOURNAL_RES_GET_NONBLOCK)
+#define JOURNAL_RES_GET_CHECK (1 << __JOURNAL_RES_GET_CHECK)
+
+static inline int journal_res_get_fast(struct journal *j,
+ struct journal_res *res,
+ unsigned flags)
+{
+ 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 (new.cur_entry_offset + res->u64s > j->cur_entry_u64s)
+ return 0;
+
+ EBUG_ON(!journal_state_count(new, new.idx));
+
+ if ((flags & BCH_WATERMARK_MASK) < j->watermark)
+ return 0;
+
+ new.cur_entry_offset += res->u64s;
+ journal_state_inc(&new);
+
+ /*
+ * If the refcount would overflow, we have to wait:
+ * XXX - tracepoint this:
+ */
+ if (!journal_state_count(new, new.idx))
+ return 0;
+
+ if (flags & JOURNAL_RES_GET_CHECK)
+ return 1;
+ } while ((v = atomic64_cmpxchg(&j->reservations.counter,
+ old.v, new.v)) != old.v);
+
+ res->ref = true;
+ res->idx = old.idx;
+ res->offset = old.cur_entry_offset;
+ res->seq = le64_to_cpu(j->buf[old.idx].data->seq);
+ return 1;
+}
+
+static inline int bch2_journal_res_get(struct journal *j, struct journal_res *res,
+ unsigned u64s, unsigned flags)
+{
+ int ret;
+
+ EBUG_ON(res->ref);
+ EBUG_ON(!test_bit(JOURNAL_STARTED, &j->flags));
+
+ res->u64s = u64s;
+
+ if (journal_res_get_fast(j, res, flags))
+ goto out;
+
+ ret = bch2_journal_res_get_slowpath(j, res, flags);
+ if (ret)
+ return ret;
+out:
+ if (!(flags & JOURNAL_RES_GET_CHECK)) {
+ lock_acquire_shared(&j->res_map, 0,
+ (flags & JOURNAL_RES_GET_NONBLOCK) != 0,
+ NULL, _THIS_IP_);
+ EBUG_ON(!res->ref);
+ }
+ return 0;
+}
+
+/* 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)
+{
+ return j->reservations.cur_entry_offset == JOURNAL_ENTRY_ERROR_VAL
+ ? -EIO : 0;
+}
+
+struct bch_dev;
+
+static inline void bch2_journal_set_replay_done(struct journal *j)
+{
+ BUG_ON(!test_bit(JOURNAL_STARTED, &j->flags));
+ set_bit(JOURNAL_REPLAY_DONE, &j->flags);
+}
+
+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 *);
+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 */
projects / bcachefs-tools-debian / blobdiff