1 /* SPDX-License-Identifier: GPL-2.0 */
2 #ifndef _BCACHEFS_JOURNAL_H
3 #define _BCACHEFS_JOURNAL_H
4
5 /*
6 * THE JOURNAL:
7 *
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.
10 *
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
14 * (with coalescing).
15 *
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.
19 *
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.
23 *
24 * PERSISTENCE:
25 *
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).
29 *
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()).
34 *
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
37 * in struct journal).
38 *
39 * JOURNAL ENTRIES:
40 *
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.
43 *
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.
46 *
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
51 * the on disk format.
52 *
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.
59 *
60 * JOURNAL LAYOUT ON DISK:
61 *
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).
66 *
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.
70 *
71 * OPEN/DIRTY JOURNAL ENTRIES:
72 *
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
77 * journal entries.
78 *
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.
81 *
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
86 * not.
87 *
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.
91 *
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).
98 *
99 * JOURNAL FILLING UP:
100 *
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
105 * same way.
106 *
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.
110 */
111
112 #include <linux/hash.h>
113
114 #include "journal_types.h"
115
116 struct bch_fs;
117
118 static inline void journal_wake(struct journal *j)
119 {
120 wake_up(&j->wait);
121 closure_wake_up(&j->async_wait);
122 }
123
124 static inline struct journal_buf *journal_cur_buf(struct journal *j)
125 {
126 return j->buf + j->reservations.idx;
127 }
128
129 /* Sequence number of oldest dirty journal entry */
130
131 static inline u64 journal_last_seq(struct journal *j)
132 {
133 return j->pin.front;
134 }
135
136 static inline u64 journal_cur_seq(struct journal *j)
137 {
138 return atomic64_read(&j->seq);
139 }
140
141 static inline u64 journal_last_unwritten_seq(struct journal *j)
142 {
143 return j->seq_ondisk + 1;
144 }
145
146 static inline int journal_state_count(union journal_res_state s, int idx)
147 {
148 switch (idx) {
149 case 0: return s.buf0_count;
150 case 1: return s.buf1_count;
151 case 2: return s.buf2_count;
152 case 3: return s.buf3_count;
153 }
154 BUG();
155 }
156
157 static inline void journal_state_inc(union journal_res_state *s)
158 {
159 s->buf0_count += s->idx == 0;
160 s->buf1_count += s->idx == 1;
161 s->buf2_count += s->idx == 2;
162 s->buf3_count += s->idx == 3;
163 }
164
165 /*
166 * Amount of space that will be taken up by some keys in the journal (i.e.
167 * including the jset header)
168 */
169 static inline unsigned jset_u64s(unsigned u64s)
170 {
171 return u64s + sizeof(struct jset_entry) / sizeof(u64);
172 }
173
174 static inline int journal_entry_overhead(struct journal *j)
175 {
176 return sizeof(struct jset) / sizeof(u64) + j->entry_u64s_reserved;
177 }
178
179 static inline struct jset_entry *
180 bch2_journal_add_entry_noreservation(struct journal_buf *buf, size_t u64s)
181 {
182 struct jset *jset = buf->data;
183 struct jset_entry *entry = vstruct_idx(jset, le32_to_cpu(jset->u64s));
184
185 memset(entry, 0, sizeof(*entry));
186 entry->u64s = cpu_to_le16(u64s);
187
188 le32_add_cpu(&jset->u64s, jset_u64s(u64s));
189
190 return entry;
191 }
192
193 static inline struct jset_entry *
194 journal_res_entry(struct journal *j, struct journal_res *res)
195 {
196 return vstruct_idx(j->buf[res->idx].data, res->offset);
197 }
198
199 static inline unsigned journal_entry_init(struct jset_entry *entry, unsigned type,
200 enum btree_id id, unsigned level,
201 unsigned u64s)
202 {
203 entry->u64s = cpu_to_le16(u64s);
204 entry->btree_id = id;
205 entry->level = level;
206 entry->type = type;
207 entry->pad[0] = 0;
208 entry->pad[1] = 0;
209 entry->pad[2] = 0;
210 return jset_u64s(u64s);
211 }
212
213 static inline unsigned journal_entry_set(struct jset_entry *entry, unsigned type,
214 enum btree_id id, unsigned level,
215 const void *data, unsigned u64s)
216 {
217 unsigned ret = journal_entry_init(entry, type, id, level, u64s);
218
219 memcpy_u64s_small(entry->_data, data, u64s);
220 return ret;
221 }
222
223 static inline struct jset_entry *
224 bch2_journal_add_entry(struct journal *j, struct journal_res *res,
225 unsigned type, enum btree_id id,
226 unsigned level, unsigned u64s)
227 {
228 struct jset_entry *entry = journal_res_entry(j, res);
229 unsigned actual = journal_entry_init(entry, type, id, level, u64s);
230
231 EBUG_ON(!res->ref);
232 EBUG_ON(actual > res->u64s);
233
234 res->offset += actual;
235 res->u64s -= actual;
236 return entry;
237 }
238
239 static inline bool journal_entry_empty(struct jset *j)
240 {
241 if (j->seq != j->last_seq)
242 return false;
243
244 vstruct_for_each(j, i)
245 if (i->type == BCH_JSET_ENTRY_btree_keys && i->u64s)
246 return false;
247 return true;
248 }
249
250 /*
251 * Drop reference on a buffer index and return true if the count has hit zero.
252 */
253 static inline union journal_res_state journal_state_buf_put(struct journal *j, unsigned idx)
254 {
255 union journal_res_state s;
256
257 s.v = atomic64_sub_return(((union journal_res_state) {
258 .buf0_count = idx == 0,
259 .buf1_count = idx == 1,
260 .buf2_count = idx == 2,
261 .buf3_count = idx == 3,
262 }).v, &j->reservations.counter);
263 return s;
264 }
265
266 bool bch2_journal_entry_close(struct journal *);
267 void bch2_journal_do_writes(struct journal *);
268 void bch2_journal_buf_put_final(struct journal *, u64);
269
270 static inline void __bch2_journal_buf_put(struct journal *j, unsigned idx, u64 seq)
271 {
272 union journal_res_state s;
273
274 s = journal_state_buf_put(j, idx);
275 if (!journal_state_count(s, idx))
276 bch2_journal_buf_put_final(j, seq);
277 }
278
279 static inline void bch2_journal_buf_put(struct journal *j, unsigned idx, u64 seq)
280 {
281 union journal_res_state s;
282
283 s = journal_state_buf_put(j, idx);
284 if (!journal_state_count(s, idx)) {
285 spin_lock(&j->lock);
286 bch2_journal_buf_put_final(j, seq);
287 spin_unlock(&j->lock);
288 }
289 }
290
291 /*
292 * This function releases the journal write structure so other threads can
293 * then proceed to add their keys as well.
294 */
295 static inline void bch2_journal_res_put(struct journal *j,
296 struct journal_res *res)
297 {
298 if (!res->ref)
299 return;
300
301 lock_release(&j->res_map, _THIS_IP_);
302
303 while (res->u64s)
304 bch2_journal_add_entry(j, res,
305 BCH_JSET_ENTRY_btree_keys,
306 0, 0, 0);
307
308 bch2_journal_buf_put(j, res->idx, res->seq);
309
310 res->ref = 0;
311 }
312
313 int bch2_journal_res_get_slowpath(struct journal *, struct journal_res *,
314 unsigned);
315
316 /* First bits for BCH_WATERMARK: */
317 enum journal_res_flags {
318 __JOURNAL_RES_GET_NONBLOCK = BCH_WATERMARK_BITS,
319 __JOURNAL_RES_GET_CHECK,
320 };
321
322 #define JOURNAL_RES_GET_NONBLOCK (1 << __JOURNAL_RES_GET_NONBLOCK)
323 #define JOURNAL_RES_GET_CHECK (1 << __JOURNAL_RES_GET_CHECK)
324
325 static inline int journal_res_get_fast(struct journal *j,
326 struct journal_res *res,
327 unsigned flags)
328 {
329 union journal_res_state old, new;
330
331 old.v = atomic64_read(&j->reservations.counter);
332 do {
333 new.v = old.v;
334
335 /*
336 * Check if there is still room in the current journal
337 * entry:
338 */
339 if (new.cur_entry_offset + res->u64s > j->cur_entry_u64s)
340 return 0;
341
342 EBUG_ON(!journal_state_count(new, new.idx));
343
344 if ((flags & BCH_WATERMARK_MASK) < j->watermark)
345 return 0;
346
347 new.cur_entry_offset += res->u64s;
348 journal_state_inc(&new);
349
350 /*
351 * If the refcount would overflow, we have to wait:
352 * XXX - tracepoint this:
353 */
354 if (!journal_state_count(new, new.idx))
355 return 0;
356
357 if (flags & JOURNAL_RES_GET_CHECK)
358 return 1;
359 } while (!atomic64_try_cmpxchg(&j->reservations.counter,
360 &old.v, new.v));
361
362 res->ref = true;
363 res->idx = old.idx;
364 res->offset = old.cur_entry_offset;
365 res->seq = le64_to_cpu(j->buf[old.idx].data->seq);
366 return 1;
367 }
368
369 static inline int bch2_journal_res_get(struct journal *j, struct journal_res *res,
370 unsigned u64s, unsigned flags)
371 {
372 int ret;
373
374 EBUG_ON(res->ref);
375 EBUG_ON(!test_bit(JOURNAL_running, &j->flags));
376
377 res->u64s = u64s;
378
379 if (journal_res_get_fast(j, res, flags))
380 goto out;
381
382 ret = bch2_journal_res_get_slowpath(j, res, flags);
383 if (ret)
384 return ret;
385 out:
386 if (!(flags & JOURNAL_RES_GET_CHECK)) {
387 lock_acquire_shared(&j->res_map, 0,
388 (flags & JOURNAL_RES_GET_NONBLOCK) != 0,
389 NULL, _THIS_IP_);
390 EBUG_ON(!res->ref);
391 }
392 return 0;
393 }
394
395 /* journal_entry_res: */
396
397 void bch2_journal_entry_res_resize(struct journal *,
398 struct journal_entry_res *,
399 unsigned);
400
401 int bch2_journal_flush_seq_async(struct journal *, u64, struct closure *);
402 void bch2_journal_flush_async(struct journal *, struct closure *);
403
404 int bch2_journal_flush_seq(struct journal *, u64);
405 int bch2_journal_flush(struct journal *);
406 bool bch2_journal_noflush_seq(struct journal *, u64);
407 int bch2_journal_meta(struct journal *);
408
409 void bch2_journal_halt(struct journal *);
410
411 static inline int bch2_journal_error(struct journal *j)
412 {
413 return j->reservations.cur_entry_offset == JOURNAL_ENTRY_ERROR_VAL
414 ? -EIO : 0;
415 }
416
417 struct bch_dev;
418
419 static inline void bch2_journal_set_replay_done(struct journal *j)
420 {
421 BUG_ON(!test_bit(JOURNAL_running, &j->flags));
422 set_bit(JOURNAL_replay_done, &j->flags);
423 }
424
425 void bch2_journal_unblock(struct journal *);
426 void bch2_journal_block(struct journal *);
427 struct journal_buf *bch2_next_write_buffer_flush_journal_buf(struct journal *j, u64 max_seq);
428
429 void __bch2_journal_debug_to_text(struct printbuf *, struct journal *);
430 void bch2_journal_debug_to_text(struct printbuf *, struct journal *);
431 void bch2_journal_pins_to_text(struct printbuf *, struct journal *);
432 bool bch2_journal_seq_pins_to_text(struct printbuf *, struct journal *, u64 *);
433
434 int bch2_set_nr_journal_buckets(struct bch_fs *, struct bch_dev *,
435 unsigned nr);
436 int bch2_dev_journal_alloc(struct bch_dev *, bool);
437 int bch2_fs_journal_alloc(struct bch_fs *);
438
439 void bch2_dev_journal_stop(struct journal *, struct bch_dev *);
440
441 void bch2_fs_journal_stop(struct journal *);
442 int bch2_fs_journal_start(struct journal *, u64);
443
444 void bch2_dev_journal_exit(struct bch_dev *);
445 int bch2_dev_journal_init(struct bch_dev *, struct bch_sb *);
446 void bch2_fs_journal_exit(struct journal *);
447 int bch2_fs_journal_init(struct journal *);
448
449 #endif /* _BCACHEFS_JOURNAL_H */
450
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