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 closure_wake_up(&j->preres_wait); 123 } 124 125 static inline struct journal_buf *journal_cur_buf(struct journal *j) 126 { 127 return j->buf + j->reservations.idx; 128 } 129 130 /* Sequence number of oldest dirty journal entry */ 131 132 static inline u64 journal_last_seq(struct journal *j) 133 { 134 return j->pin.front; 135 } 136 137 static inline u64 journal_cur_seq(struct journal *j) 138 { 139 return atomic64_read(&j->seq); 140 } 141 142 static inline u64 journal_last_unwritten_seq(struct journal *j) 143 { 144 return j->seq_ondisk + 1; 145 } 146 147 static inline int journal_state_count(union journal_res_state s, int idx) 148 { 149 switch (idx) { 150 case 0: return s.buf0_count; 151 case 1: return s.buf1_count; 152 case 2: return s.buf2_count; 153 case 3: return s.buf3_count; 154 } 155 BUG(); 156 } 157 158 static inline void journal_state_inc(union journal_res_state *s) 159 { 160 s->buf0_count += s->idx == 0; 161 s->buf1_count += s->idx == 1; 162 s->buf2_count += s->idx == 2; 163 s->buf3_count += s->idx == 3; 164 } 165 166 /* 167 * Amount of space that will be taken up by some keys in the journal (i.e. 168 * including the jset header) 169 */ 170 static inline unsigned jset_u64s(unsigned u64s) 171 { 172 return u64s + sizeof(struct jset_entry) / sizeof(u64); 173 } 174 175 static inline int journal_entry_overhead(struct journal *j) 176 { 177 return sizeof(struct jset) / sizeof(u64) + j->entry_u64s_reserved; 178 } 179 180 static inline struct jset_entry * 181 bch2_journal_add_entry_noreservation(struct journal_buf *buf, size_t u64s) 182 { 183 struct jset *jset = buf->data; 184 struct jset_entry *entry = vstruct_idx(jset, le32_to_cpu(jset->u64s)); 185 186 memset(entry, 0, sizeof(*entry)); 187 entry->u64s = cpu_to_le16(u64s); 188 189 le32_add_cpu(&jset->u64s, jset_u64s(u64s)); 190 191 return entry; 192 } 193 194 static inline struct jset_entry * 195 journal_res_entry(struct journal *j, struct journal_res *res) 196 { 197 return vstruct_idx(j->buf[res->idx].data, res->offset); 198 } 199 200 static inline unsigned journal_entry_init(struct jset_entry *entry, unsigned type, 201 enum btree_id id, unsigned level, 202 unsigned u64s) 203 { 204 entry->u64s = cpu_to_le16(u64s); 205 entry->btree_id = id; 206 entry->level = level; 207 entry->type = type; 208 entry->pad[0] = 0; 209 entry->pad[1] = 0; 210 entry->pad[2] = 0; 211 return jset_u64s(u64s); 212 } 213 214 static inline unsigned journal_entry_set(struct jset_entry *entry, unsigned type, 215 enum btree_id id, unsigned level, 216 const void *data, unsigned u64s) 217 { 218 unsigned ret = journal_entry_init(entry, type, id, level, u64s); 219 220 memcpy_u64s_small(entry->_data, data, u64s); 221 return ret; 222 } 223 224 static inline struct jset_entry * 225 bch2_journal_add_entry(struct journal *j, struct journal_res *res, 226 unsigned type, enum btree_id id, 227 unsigned level, unsigned u64s) 228 { 229 struct jset_entry *entry = journal_res_entry(j, res); 230 unsigned actual = journal_entry_init(entry, type, id, level, u64s); 231 232 EBUG_ON(!res->ref); 233 EBUG_ON(actual > res->u64s); 234 235 res->offset += actual; 236 res->u64s -= actual; 237 return entry; 238 } 239 240 static inline bool journal_entry_empty(struct jset *j) 241 { 242 struct jset_entry *i; 243 244 if (j->seq != j->last_seq) 245 return false; 246 247 vstruct_for_each(j, i) 248 if (i->type == BCH_JSET_ENTRY_btree_keys && i->u64s) 249 return false; 250 return true; 251 } 252 253 /* 254 * Drop reference on a buffer index and return true if the count has hit zero. 255 */ 256 static inline union journal_res_state journal_state_buf_put(struct journal *j, unsigned idx) 257 { 258 union journal_res_state s; 259 260 s.v = atomic64_sub_return(((union journal_res_state) { 261 .buf0_count = idx == 0, 262 .buf1_count = idx == 1, 263 .buf2_count = idx == 2, 264 .buf3_count = idx == 3, 265 }).v, &j->reservations.counter); 266 return s; 267 } 268 269 void bch2_journal_buf_put_final(struct journal *, u64, bool); 270 271 static inline void __bch2_journal_buf_put(struct journal *j, unsigned idx, u64 seq) 272 { 273 union journal_res_state s; 274 275 s = journal_state_buf_put(j, idx); 276 if (!journal_state_count(s, idx)) 277 bch2_journal_buf_put_final(j, seq, idx == s.unwritten_idx); 278 } 279 280 static inline void bch2_journal_buf_put(struct journal *j, unsigned idx, u64 seq) 281 { 282 union journal_res_state s; 283 284 s = journal_state_buf_put(j, idx); 285 if (!journal_state_count(s, idx)) { 286 spin_lock(&j->lock); 287 bch2_journal_buf_put_final(j, seq, idx == s.unwritten_idx); 288 spin_unlock(&j->lock); 289 } 290 } 291 292 /* 293 * This function releases the journal write structure so other threads can 294 * then proceed to add their keys as well. 295 */ 296 static inline void bch2_journal_res_put(struct journal *j, 297 struct journal_res *res) 298 { 299 if (!res->ref) 300 return; 301 302 lock_release(&j->res_map, _THIS_IP_); 303 304 while (res->u64s) 305 bch2_journal_add_entry(j, res, 306 BCH_JSET_ENTRY_btree_keys, 307 0, 0, 0); 308 309 bch2_journal_buf_put(j, res->idx, res->seq); 310 311 res->ref = 0; 312 } 313 314 int bch2_journal_res_get_slowpath(struct journal *, struct journal_res *, 315 unsigned); 316 317 /* First bits for BCH_WATERMARK: */ 318 enum journal_res_flags { 319 __JOURNAL_RES_GET_NONBLOCK = BCH_WATERMARK_BITS, 320 __JOURNAL_RES_GET_CHECK, 321 }; 322 323 #define JOURNAL_RES_GET_NONBLOCK (1 << __JOURNAL_RES_GET_NONBLOCK) 324 #define JOURNAL_RES_GET_CHECK (1 << __JOURNAL_RES_GET_CHECK) 325 326 static inline int journal_res_get_fast(struct journal *j, 327 struct journal_res *res, 328 unsigned flags) 329 { 330 union journal_res_state old, new; 331 u64 v = atomic64_read(&j->reservations.counter); 332 333 do { 334 old.v = new.v = v; 335 336 /* 337 * Check if there is still room in the current journal 338 * entry: 339 */ 340 if (new.cur_entry_offset + res->u64s > j->cur_entry_u64s) 341 return 0; 342 343 EBUG_ON(!journal_state_count(new, new.idx)); 344 345 if ((flags & BCH_WATERMARK_MASK) < j->watermark) 346 return 0; 347 348 new.cur_entry_offset += res->u64s; 349 journal_state_inc(&new); 350 351 /* 352 * If the refcount would overflow, we have to wait: 353 * XXX - tracepoint this: 354 */ 355 if (!journal_state_count(new, new.idx)) 356 return 0; 357 358 if (flags & JOURNAL_RES_GET_CHECK) 359 return 1; 360 } while ((v = atomic64_cmpxchg(&j->reservations.counter, 361 old.v, new.v)) != old.v); 362 363 res->ref = true; 364 res->idx = old.idx; 365 res->offset = old.cur_entry_offset; 366 res->seq = le64_to_cpu(j->buf[old.idx].data->seq); 367 return 1; 368 } 369 370 static inline int bch2_journal_res_get(struct journal *j, struct journal_res *res, 371 unsigned u64s, unsigned flags) 372 { 373 int ret; 374 375 EBUG_ON(res->ref); 376 EBUG_ON(!test_bit(JOURNAL_STARTED, &j->flags)); 377 378 res->u64s = u64s; 379 380 if (journal_res_get_fast(j, res, flags)) 381 goto out; 382 383 ret = bch2_journal_res_get_slowpath(j, res, flags); 384 if (ret) 385 return ret; 386 out: 387 if (!(flags & JOURNAL_RES_GET_CHECK)) { 388 lock_acquire_shared(&j->res_map, 0, 389 (flags & JOURNAL_RES_GET_NONBLOCK) != 0, 390 NULL, _THIS_IP_); 391 EBUG_ON(!res->ref); 392 } 393 return 0; 394 } 395 396 /* journal_entry_res: */ 397 398 void bch2_journal_entry_res_resize(struct journal *, 399 struct journal_entry_res *, 400 unsigned); 401 402 int bch2_journal_flush_seq_async(struct journal *, u64, struct closure *); 403 void bch2_journal_flush_async(struct journal *, struct closure *); 404 405 int bch2_journal_flush_seq(struct journal *, u64); 406 int bch2_journal_flush(struct journal *); 407 bool bch2_journal_noflush_seq(struct journal *, u64); 408 int bch2_journal_meta(struct journal *); 409 410 void bch2_journal_halt(struct journal *); 411 412 static inline int bch2_journal_error(struct journal *j) 413 { 414 return j->reservations.cur_entry_offset == JOURNAL_ENTRY_ERROR_VAL 415 ? -EIO : 0; 416 } 417 418 struct bch_dev; 419 420 static inline void bch2_journal_set_replay_done(struct journal *j) 421 { 422 BUG_ON(!test_bit(JOURNAL_STARTED, &j->flags)); 423 set_bit(JOURNAL_REPLAY_DONE, &j->flags); 424 } 425 426 void bch2_journal_unblock(struct journal *); 427 void bch2_journal_block(struct journal *); 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 *); 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