summaryrefslogtreecommitdiff
path: root/libbcache/journal.h
blob: 9274831acae3f24f752b631e51db0098154bf4ce (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
#ifndef _BCACHE_JOURNAL_H
#define _BCACHE_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
 * bch_btree_insert() or bch_btree_insert_node(), which then pass that parameter
 * down to the journalling code. That closure will 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"
//#include "super-io.h"

/*
 * Only used for holding the journal entries we read in btree_journal_read()
 * during cache_registration
 */
struct journal_replay {
	struct list_head	list;
	struct jset		j;
};

#define JOURNAL_PIN	((32 * 1024) - 1)

static inline bool journal_pin_active(struct journal_entry_pin *pin)
{
	return pin->pin_list != NULL;
}

void bch_journal_pin_add(struct journal *, struct journal_entry_pin *,
			 journal_pin_flush_fn);
void bch_journal_pin_drop(struct journal *, struct journal_entry_pin *);
void bch_journal_pin_add_if_older(struct journal *,
				  struct journal_entry_pin *,
				  struct journal_entry_pin *,
				  journal_pin_flush_fn);

struct closure;
struct cache_set;
struct keylist;

struct bkey_i *bch_journal_find_btree_root(struct cache_set *, struct jset *,
					   enum btree_id, unsigned *);

int bch_journal_seq_should_ignore(struct cache_set *, u64, struct btree *);

u64 bch_inode_journal_seq(struct journal *, u64);

static inline int journal_state_count(union journal_res_state s, int idx)
{
	return idx == 0 ? s.buf0_count : s.buf1_count;
}

static inline void journal_state_inc(union journal_res_state *s)
{
	s->buf0_count += s->idx == 0;
	s->buf1_count += s->idx == 1;
}

static inline void bch_journal_set_has_inode(struct journal_buf *buf, u64 inum)
{
	set_bit(hash_64(inum, ilog2(sizeof(buf->has_inode) * 8)), buf->has_inode);
}

/*
 * 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 void bch_journal_add_entry_at(struct journal_buf *buf,
					    const void *data, size_t u64s,
					    unsigned type, enum btree_id id,
					    unsigned level, unsigned offset)
{
	struct jset_entry *entry = vstruct_idx(buf->data, offset);

	entry->u64s = cpu_to_le16(u64s);
	entry->btree_id = id;
	entry->level = level;
	entry->flags = 0;
	SET_JOURNAL_ENTRY_TYPE(entry, type);

	memcpy_u64s(entry->_data, data, u64s);
}

static inline void bch_journal_add_keys(struct journal *j, struct journal_res *res,
					enum btree_id id, const struct bkey_i *k)
{
	struct journal_buf *buf = &j->buf[res->idx];
	unsigned actual = jset_u64s(k->k.u64s);

	EBUG_ON(!res->ref);
	BUG_ON(actual > res->u64s);

	bch_journal_set_has_inode(buf, k->k.p.inode);

	bch_journal_add_entry_at(buf, k, k->k.u64s,
				 JOURNAL_ENTRY_BTREE_KEYS, id,
				 0, res->offset);

	res->offset	+= actual;
	res->u64s	-= actual;
}

void bch_journal_buf_put_slowpath(struct journal *, bool);

static inline void bch_journal_buf_put(struct journal *j, unsigned idx,
				       bool need_write_just_set)
{
	union journal_res_state s;

	s.v = atomic64_sub_return(((union journal_res_state) {
				    .buf0_count = idx == 0,
				    .buf1_count = idx == 1,
				    }).v, &j->reservations.counter);

	EBUG_ON(s.idx != idx && !s.prev_buf_unwritten);

	/*
	 * Do not initiate a journal write if the journal is in an error state
	 * (previous journal entry write may have failed)
	 */
	if (s.idx != idx &&
	    !journal_state_count(s, idx) &&
	    s.cur_entry_offset != JOURNAL_ENTRY_ERROR_VAL)
		bch_journal_buf_put_slowpath(j, need_write_just_set);
}

/*
 * This function releases the journal write structure so other threads can
 * then proceed to add their keys as well.
 */
static inline void bch_journal_res_put(struct journal *j,
				       struct journal_res *res)
{
	if (!res->ref)
		return;

	lock_release(&j->res_map, 0, _RET_IP_);

	while (res->u64s) {
		bch_journal_add_entry_at(&j->buf[res->idx], NULL, 0,
					 JOURNAL_ENTRY_BTREE_KEYS,
					 0, 0, res->offset);
		res->offset	+= jset_u64s(0);
		res->u64s	-= jset_u64s(0);
	}

	bch_journal_buf_put(j, res->idx, false);

	res->ref = 0;
}

int bch_journal_res_get_slowpath(struct journal *, struct journal_res *,
				 unsigned, unsigned);

static inline int journal_res_get_fast(struct journal *j,
				       struct journal_res *res,
				       unsigned u64s_min,
				       unsigned u64s_max)
{
	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 (old.cur_entry_offset + u64s_min > j->cur_entry_u64s)
			return 0;

		res->offset	= old.cur_entry_offset;
		res->u64s	= min(u64s_max, j->cur_entry_u64s -
				      old.cur_entry_offset);

		journal_state_inc(&new);
		new.cur_entry_offset += res->u64s;
	} while ((v = atomic64_cmpxchg(&j->reservations.counter,
				       old.v, new.v)) != old.v);

	res->ref = true;
	res->idx = new.idx;
	res->seq = le64_to_cpu(j->buf[res->idx].data->seq);
	return 1;
}

static inline int bch_journal_res_get(struct journal *j, struct journal_res *res,
				      unsigned u64s_min, unsigned u64s_max)
{
	int ret;

	EBUG_ON(res->ref);
	EBUG_ON(u64s_max < u64s_min);

	if (journal_res_get_fast(j, res, u64s_min, u64s_max))
		goto out;

	ret = bch_journal_res_get_slowpath(j, res, u64s_min, u64s_max);
	if (ret)
		return ret;
out:
	lock_acquire_shared(&j->res_map, 0, 0, NULL, _THIS_IP_);
	EBUG_ON(!res->ref);
	return 0;
}

void bch_journal_wait_on_seq(struct journal *, u64, struct closure *);
void bch_journal_flush_seq_async(struct journal *, u64, struct closure *);
void bch_journal_flush_async(struct journal *, struct closure *);
void bch_journal_meta_async(struct journal *, struct closure *);

int bch_journal_flush_seq(struct journal *, u64);
int bch_journal_flush(struct journal *);
int bch_journal_meta(struct journal *);

void bch_journal_halt(struct journal *);

static inline int bch_journal_error(struct journal *j)
{
	return j->reservations.cur_entry_offset == JOURNAL_ENTRY_ERROR_VAL
		? -EIO : 0;
}

static inline bool is_journal_device(struct cache *ca)
{
	return ca->mi.state == BCH_MEMBER_STATE_ACTIVE && ca->mi.tier == 0;
}

static inline bool journal_flushes_device(struct cache *ca)
{
	return true;
}

void bch_journal_start(struct cache_set *);
void bch_journal_mark(struct cache_set *, struct list_head *);
void bch_journal_entries_free(struct list_head *);
int bch_journal_read(struct cache_set *, struct list_head *);
int bch_journal_replay(struct cache_set *, struct list_head *);

static inline void bch_journal_set_replay_done(struct journal *j)
{
	spin_lock(&j->lock);
	BUG_ON(!test_bit(JOURNAL_STARTED, &j->flags));

	set_bit(JOURNAL_REPLAY_DONE, &j->flags);
	j->cur_pin_list = &fifo_peek_back(&j->pin);
	spin_unlock(&j->lock);
}

void bch_journal_free(struct journal *);
int bch_journal_alloc(struct journal *, unsigned);

ssize_t bch_journal_print_debug(struct journal *, char *);

int bch_cache_journal_alloc(struct cache *);

static inline unsigned bch_nr_journal_buckets(struct bch_sb_field_journal *j)
{
	return j
		? (__le64 *) vstruct_end(&j->field) - j->buckets
		: 0;
}

int bch_journal_move(struct cache *);

void bch_journal_free_cache(struct cache *);
int bch_journal_init_cache(struct cache *);

#endif /* _BCACHE_JOURNAL_H */