1 /* SPDX-License-Identifier: GPL-2.0 */
2 #ifndef _BCACHEFS_JOURNAL_H
3 #define _BCACHEFS_JOURNAL_H
8 * The primary purpose of the journal is to log updates (insertions) to the
9 * b-tree, to avoid having to do synchronous updates to the b-tree on disk.
11 * Without the journal, the b-tree is always internally consistent on
12 * disk - and in fact, in the earliest incarnations bcache didn't have a journal
13 * but did handle unclean shutdowns by doing all index updates synchronously
16 * Updates to interior nodes still happen synchronously and without the journal
17 * (for simplicity) - this may change eventually but updates to interior nodes
18 * are rare enough it's not a huge priority.
20 * This means the journal is relatively separate from the b-tree; it consists of
21 * just a list of keys and journal replay consists of just redoing those
22 * insertions in same order that they appear in the journal.
26 * For synchronous updates (where we're waiting on the index update to hit
27 * disk), the journal entry will be written out immediately (or as soon as
28 * possible, if the write for the previous journal entry was still in flight).
30 * Synchronous updates are specified by passing a closure (@flush_cl) to
31 * bch2_btree_insert() or bch_btree_insert_node(), which then pass that parameter
32 * down to the journalling code. That closure will wait on the journal write to
33 * complete (via closure_wait()).
35 * If the index update wasn't synchronous, the journal entry will be
36 * written out after 10 ms have elapsed, by default (the delay_ms field
41 * A journal entry is variable size (struct jset), it's got a fixed length
42 * header and then a variable number of struct jset_entry entries.
44 * Journal entries are identified by monotonically increasing 64 bit sequence
45 * numbers - jset->seq; other places in the code refer to this sequence number.
47 * A jset_entry entry contains one or more bkeys (which is what gets inserted
48 * into the b-tree). We need a container to indicate which b-tree the key is
49 * for; also, the roots of the various b-trees are stored in jset_entry entries
50 * (one for each b-tree) - this lets us add new b-tree types without changing
53 * We also keep some things in the journal header that are logically part of the
54 * superblock - all the things that are frequently updated. This is for future
55 * bcache on raw flash support; the superblock (which will become another
56 * journal) can't be moved or wear leveled, so it contains just enough
57 * information to find the main journal, and the superblock only has to be
58 * rewritten when we want to move/wear level the main journal.
60 * JOURNAL LAYOUT ON DISK:
62 * The journal is written to a ringbuffer of buckets (which is kept in the
63 * superblock); the individual buckets are not necessarily contiguous on disk
64 * which means that journal entries are not allowed to span buckets, but also
65 * that we can resize the journal at runtime if desired (unimplemented).
67 * The journal buckets exist in the same pool as all the other buckets that are
68 * managed by the allocator and garbage collection - garbage collection marks
69 * the journal buckets as metadata buckets.
71 * OPEN/DIRTY JOURNAL ENTRIES:
73 * Open/dirty journal entries are journal entries that contain b-tree updates
74 * that have not yet been written out to the b-tree on disk. We have to track
75 * which journal entries are dirty, and we also have to avoid wrapping around
76 * the journal and overwriting old but still dirty journal entries with new
79 * On disk, this is represented with the "last_seq" field of struct jset;
80 * last_seq is the first sequence number that journal replay has to replay.
82 * To avoid overwriting dirty journal entries on disk, we keep a mapping (in
83 * journal_device->seq) of for each journal bucket, the highest sequence number
84 * any journal entry it contains. Then, by comparing that against last_seq we
85 * can determine whether that journal bucket contains dirty journal entries or
88 * To track which journal entries are dirty, we maintain a fifo of refcounts
89 * (where each entry corresponds to a specific sequence number) - when a ref
90 * goes to 0, that journal entry is no longer dirty.
92 * Journalling of index updates is done at the same time as the b-tree itself is
93 * being modified (see btree_insert_key()); when we add the key to the journal
94 * the pending b-tree write takes a ref on the journal entry the key was added
95 * to. If a pending b-tree write would need to take refs on multiple dirty
96 * journal entries, it only keeps the ref on the oldest one (since a newer
97 * journal entry will still be replayed if an older entry was dirty).
101 * There are two ways the journal could fill up; either we could run out of
102 * space to write to, or we could have too many open journal entries and run out
103 * of room in the fifo of refcounts. Since those refcounts are decremented
104 * without any locking we can't safely resize that fifo, so we handle it the
107 * If the journal fills up, we start flushing dirty btree nodes until we can
108 * allocate space for a journal write again - preferentially flushing btree
109 * nodes that are pinning the oldest journal entries first.
112 #include <linux/hash.h>
114 #include "journal_types.h"
118 static inline void journal_wake(struct journal *j)
121 closure_wake_up(&j->async_wait);
122 closure_wake_up(&j->preres_wait);
125 static inline struct journal_buf *journal_cur_buf(struct journal *j)
127 return j->buf + j->reservations.idx;
130 /* Sequence number of oldest dirty journal entry */
132 static inline u64 journal_last_seq(struct journal *j)
137 static inline u64 journal_cur_seq(struct journal *j)
139 EBUG_ON(j->pin.back - 1 != atomic64_read(&j->seq));
141 return j->pin.back - 1;
144 static inline u64 journal_last_unwritten_seq(struct journal *j)
146 return j->seq_ondisk + 1;
149 static inline int journal_state_count(union journal_res_state s, int idx)
152 case 0: return s.buf0_count;
153 case 1: return s.buf1_count;
154 case 2: return s.buf2_count;
155 case 3: return s.buf3_count;
160 static inline void journal_state_inc(union journal_res_state *s)
162 s->buf0_count += s->idx == 0;
163 s->buf1_count += s->idx == 1;
164 s->buf2_count += s->idx == 2;
165 s->buf3_count += s->idx == 3;
169 * Amount of space that will be taken up by some keys in the journal (i.e.
170 * including the jset header)
172 static inline unsigned jset_u64s(unsigned u64s)
174 return u64s + sizeof(struct jset_entry) / sizeof(u64);
177 static inline int journal_entry_overhead(struct journal *j)
179 return sizeof(struct jset) / sizeof(u64) + j->entry_u64s_reserved;
182 static inline struct jset_entry *
183 bch2_journal_add_entry_noreservation(struct journal_buf *buf, size_t u64s)
185 struct jset *jset = buf->data;
186 struct jset_entry *entry = vstruct_idx(jset, le32_to_cpu(jset->u64s));
188 memset(entry, 0, sizeof(*entry));
189 entry->u64s = cpu_to_le16(u64s);
191 le32_add_cpu(&jset->u64s, jset_u64s(u64s));
196 static inline struct jset_entry *
197 journal_res_entry(struct journal *j, struct journal_res *res)
199 return vstruct_idx(j->buf[res->idx].data, res->offset);
202 static inline unsigned journal_entry_init(struct jset_entry *entry, unsigned type,
203 enum btree_id id, unsigned level,
206 entry->u64s = cpu_to_le16(u64s);
207 entry->btree_id = id;
208 entry->level = level;
213 return jset_u64s(u64s);
216 static inline unsigned journal_entry_set(struct jset_entry *entry, unsigned type,
217 enum btree_id id, unsigned level,
218 const void *data, unsigned u64s)
220 unsigned ret = journal_entry_init(entry, type, id, level, u64s);
222 memcpy_u64s_small(entry->_data, data, u64s);
226 static inline struct jset_entry *
227 bch2_journal_add_entry(struct journal *j, struct journal_res *res,
228 unsigned type, enum btree_id id,
229 unsigned level, unsigned u64s)
231 struct jset_entry *entry = journal_res_entry(j, res);
232 unsigned actual = journal_entry_init(entry, type, id, level, u64s);
235 EBUG_ON(actual > res->u64s);
237 res->offset += actual;
242 static inline bool journal_entry_empty(struct jset *j)
244 struct jset_entry *i;
246 if (j->seq != j->last_seq)
249 vstruct_for_each(j, i)
250 if (i->type == BCH_JSET_ENTRY_btree_keys && i->u64s)
256 * Drop reference on a buffer index and return true if the count has hit zero.
258 static inline union journal_res_state journal_state_buf_put(struct journal *j, unsigned idx)
260 union journal_res_state s;
262 s.v = atomic64_sub_return(((union journal_res_state) {
263 .buf0_count = idx == 0,
264 .buf1_count = idx == 1,
265 .buf2_count = idx == 2,
266 .buf3_count = idx == 3,
267 }).v, &j->reservations.counter);
271 void bch2_journal_buf_put_final(struct journal *, u64, bool);
273 static inline void __bch2_journal_buf_put(struct journal *j, unsigned idx, u64 seq)
275 union journal_res_state s;
277 s = journal_state_buf_put(j, idx);
278 if (!journal_state_count(s, idx))
279 bch2_journal_buf_put_final(j, seq, idx == s.unwritten_idx);
282 static inline void bch2_journal_buf_put(struct journal *j, unsigned idx, u64 seq)
284 union journal_res_state s;
286 s = journal_state_buf_put(j, idx);
287 if (!journal_state_count(s, idx)) {
289 bch2_journal_buf_put_final(j, seq, idx == s.unwritten_idx);
290 spin_unlock(&j->lock);
295 * This function releases the journal write structure so other threads can
296 * then proceed to add their keys as well.
298 static inline void bch2_journal_res_put(struct journal *j,
299 struct journal_res *res)
304 lock_release(&j->res_map, _THIS_IP_);
307 bch2_journal_add_entry(j, res,
308 BCH_JSET_ENTRY_btree_keys,
311 bch2_journal_buf_put(j, res->idx, res->seq);
316 int bch2_journal_res_get_slowpath(struct journal *, struct journal_res *,
319 /* First bits for BCH_WATERMARK: */
320 enum journal_res_flags {
321 __JOURNAL_RES_GET_NONBLOCK = BCH_WATERMARK_BITS,
322 __JOURNAL_RES_GET_CHECK,
325 #define JOURNAL_RES_GET_NONBLOCK (1 << __JOURNAL_RES_GET_NONBLOCK)
326 #define JOURNAL_RES_GET_CHECK (1 << __JOURNAL_RES_GET_CHECK)
328 static inline int journal_res_get_fast(struct journal *j,
329 struct journal_res *res,
332 union journal_res_state old, new;
333 u64 v = atomic64_read(&j->reservations.counter);
339 * Check if there is still room in the current journal
342 if (new.cur_entry_offset + res->u64s > j->cur_entry_u64s)
345 EBUG_ON(!journal_state_count(new, new.idx));
347 if ((flags & BCH_WATERMARK_MASK) < j->watermark)
350 new.cur_entry_offset += res->u64s;
351 journal_state_inc(&new);
354 * If the refcount would overflow, we have to wait:
355 * XXX - tracepoint this:
357 if (!journal_state_count(new, new.idx))
360 if (flags & JOURNAL_RES_GET_CHECK)
362 } while ((v = atomic64_cmpxchg(&j->reservations.counter,
363 old.v, new.v)) != old.v);
367 res->offset = old.cur_entry_offset;
368 res->seq = le64_to_cpu(j->buf[old.idx].data->seq);
372 static inline int bch2_journal_res_get(struct journal *j, struct journal_res *res,
373 unsigned u64s, unsigned flags)
378 EBUG_ON(!test_bit(JOURNAL_STARTED, &j->flags));
382 if (journal_res_get_fast(j, res, flags))
385 ret = bch2_journal_res_get_slowpath(j, res, flags);
389 if (!(flags & JOURNAL_RES_GET_CHECK)) {
390 lock_acquire_shared(&j->res_map, 0,
391 (flags & JOURNAL_RES_GET_NONBLOCK) != 0,
398 /* journal_entry_res: */
400 void bch2_journal_entry_res_resize(struct journal *,
401 struct journal_entry_res *,
404 int bch2_journal_flush_seq_async(struct journal *, u64, struct closure *);
405 void bch2_journal_flush_async(struct journal *, struct closure *);
407 int bch2_journal_flush_seq(struct journal *, u64);
408 int bch2_journal_flush(struct journal *);
409 bool bch2_journal_noflush_seq(struct journal *, u64);
410 int bch2_journal_meta(struct journal *);
412 void bch2_journal_halt(struct journal *);
414 static inline int bch2_journal_error(struct journal *j)
416 return j->reservations.cur_entry_offset == JOURNAL_ENTRY_ERROR_VAL
422 static inline void bch2_journal_set_replay_done(struct journal *j)
424 BUG_ON(!test_bit(JOURNAL_STARTED, &j->flags));
425 set_bit(JOURNAL_REPLAY_DONE, &j->flags);
428 void bch2_journal_unblock(struct journal *);
429 void bch2_journal_block(struct journal *);
431 void __bch2_journal_debug_to_text(struct printbuf *, struct journal *);
432 void bch2_journal_debug_to_text(struct printbuf *, struct journal *);
433 void bch2_journal_pins_to_text(struct printbuf *, struct journal *);
434 bool bch2_journal_seq_pins_to_text(struct printbuf *, struct journal *, u64 *);
436 int bch2_set_nr_journal_buckets(struct bch_fs *, struct bch_dev *,
438 int bch2_dev_journal_alloc(struct bch_dev *);
439 int bch2_fs_journal_alloc(struct bch_fs *);
441 void bch2_dev_journal_stop(struct journal *, struct bch_dev *);
443 void bch2_fs_journal_stop(struct journal *);
444 int bch2_fs_journal_start(struct journal *, u64);
446 void bch2_dev_journal_exit(struct bch_dev *);
447 int bch2_dev_journal_init(struct bch_dev *, struct bch_sb *);
448 void bch2_fs_journal_exit(struct journal *);
449 int bch2_fs_journal_init(struct journal *);
451 #endif /* _BCACHEFS_JOURNAL_H */