summaryrefslogtreecommitdiff
path: root/fs/xfs/xfs_log_priv.h
blob: b8778a4fd6b64e3a2ab9a09f2ab0dd916f2c6487 (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
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
// SPDX-License-Identifier: GPL-2.0
/*
 * Copyright (c) 2000-2003,2005 Silicon Graphics, Inc.
 * All Rights Reserved.
 */
#ifndef	__XFS_LOG_PRIV_H__
#define __XFS_LOG_PRIV_H__

#include "xfs_extent_busy.h"	/* for struct xfs_busy_extents */

struct xfs_buf;
struct xlog;
struct xlog_ticket;
struct xfs_mount;

/*
 * get client id from packed copy.
 *
 * this hack is here because the xlog_pack code copies four bytes
 * of xlog_op_header containing the fields oh_clientid, oh_flags
 * and oh_res2 into the packed copy.
 *
 * later on this four byte chunk is treated as an int and the
 * client id is pulled out.
 *
 * this has endian issues, of course.
 */
static inline uint xlog_get_client_id(__be32 i)
{
	return be32_to_cpu(i) >> 24;
}

/*
 * In core log state
 */
enum xlog_iclog_state {
	XLOG_STATE_ACTIVE,	/* Current IC log being written to */
	XLOG_STATE_WANT_SYNC,	/* Want to sync this iclog; no more writes */
	XLOG_STATE_SYNCING,	/* This IC log is syncing */
	XLOG_STATE_DONE_SYNC,	/* Done syncing to disk */
	XLOG_STATE_CALLBACK,	/* Callback functions now */
	XLOG_STATE_DIRTY,	/* Dirty IC log, not ready for ACTIVE status */
};

#define XLOG_STATE_STRINGS \
	{ XLOG_STATE_ACTIVE,	"XLOG_STATE_ACTIVE" }, \
	{ XLOG_STATE_WANT_SYNC,	"XLOG_STATE_WANT_SYNC" }, \
	{ XLOG_STATE_SYNCING,	"XLOG_STATE_SYNCING" }, \
	{ XLOG_STATE_DONE_SYNC,	"XLOG_STATE_DONE_SYNC" }, \
	{ XLOG_STATE_CALLBACK,	"XLOG_STATE_CALLBACK" }, \
	{ XLOG_STATE_DIRTY,	"XLOG_STATE_DIRTY" }

/*
 * In core log flags
 */
#define XLOG_ICL_NEED_FLUSH	(1u << 0)	/* iclog needs REQ_PREFLUSH */
#define XLOG_ICL_NEED_FUA	(1u << 1)	/* iclog needs REQ_FUA */

#define XLOG_ICL_STRINGS \
	{ XLOG_ICL_NEED_FLUSH,	"XLOG_ICL_NEED_FLUSH" }, \
	{ XLOG_ICL_NEED_FUA,	"XLOG_ICL_NEED_FUA" }


/*
 * Log ticket flags
 */
#define XLOG_TIC_PERM_RESERV	(1u << 0)	/* permanent reservation */

#define XLOG_TIC_FLAGS \
	{ XLOG_TIC_PERM_RESERV,	"XLOG_TIC_PERM_RESERV" }

/*
 * Below are states for covering allocation transactions.
 * By covering, we mean changing the h_tail_lsn in the last on-disk
 * log write such that no allocation transactions will be re-done during
 * recovery after a system crash. Recovery starts at the last on-disk
 * log write.
 *
 * These states are used to insert dummy log entries to cover
 * space allocation transactions which can undo non-transactional changes
 * after a crash. Writes to a file with space
 * already allocated do not result in any transactions. Allocations
 * might include space beyond the EOF. So if we just push the EOF a
 * little, the last transaction for the file could contain the wrong
 * size. If there is no file system activity, after an allocation
 * transaction, and the system crashes, the allocation transaction
 * will get replayed and the file will be truncated. This could
 * be hours/days/... after the allocation occurred.
 *
 * The fix for this is to do two dummy transactions when the
 * system is idle. We need two dummy transaction because the h_tail_lsn
 * in the log record header needs to point beyond the last possible
 * non-dummy transaction. The first dummy changes the h_tail_lsn to
 * the first transaction before the dummy. The second dummy causes
 * h_tail_lsn to point to the first dummy. Recovery starts at h_tail_lsn.
 *
 * These dummy transactions get committed when everything
 * is idle (after there has been some activity).
 *
 * There are 5 states used to control this.
 *
 *  IDLE -- no logging has been done on the file system or
 *		we are done covering previous transactions.
 *  NEED -- logging has occurred and we need a dummy transaction
 *		when the log becomes idle.
 *  DONE -- we were in the NEED state and have committed a dummy
 *		transaction.
 *  NEED2 -- we detected that a dummy transaction has gone to the
 *		on disk log with no other transactions.
 *  DONE2 -- we committed a dummy transaction when in the NEED2 state.
 *
 * There are two places where we switch states:
 *
 * 1.) In xfs_sync, when we detect an idle log and are in NEED or NEED2.
 *	We commit the dummy transaction and switch to DONE or DONE2,
 *	respectively. In all other states, we don't do anything.
 *
 * 2.) When we finish writing the on-disk log (xlog_state_clean_log).
 *
 *	No matter what state we are in, if this isn't the dummy
 *	transaction going out, the next state is NEED.
 *	So, if we aren't in the DONE or DONE2 states, the next state
 *	is NEED. We can't be finishing a write of the dummy record
 *	unless it was committed and the state switched to DONE or DONE2.
 *
 *	If we are in the DONE state and this was a write of the
 *		dummy transaction, we move to NEED2.
 *
 *	If we are in the DONE2 state and this was a write of the
 *		dummy transaction, we move to IDLE.
 *
 *
 * Writing only one dummy transaction can get appended to
 * one file space allocation. When this happens, the log recovery
 * code replays the space allocation and a file could be truncated.
 * This is why we have the NEED2 and DONE2 states before going idle.
 */

#define XLOG_STATE_COVER_IDLE	0
#define XLOG_STATE_COVER_NEED	1
#define XLOG_STATE_COVER_DONE	2
#define XLOG_STATE_COVER_NEED2	3
#define XLOG_STATE_COVER_DONE2	4

#define XLOG_COVER_OPS		5

typedef struct xlog_ticket {
	struct list_head	t_queue;	/* reserve/write queue */
	struct task_struct	*t_task;	/* task that owns this ticket */
	xlog_tid_t		t_tid;		/* transaction identifier */
	atomic_t		t_ref;		/* ticket reference count */
	int			t_curr_res;	/* current reservation */
	int			t_unit_res;	/* unit reservation */
	char			t_ocnt;		/* original unit count */
	char			t_cnt;		/* current unit count */
	uint8_t			t_flags;	/* properties of reservation */
	int			t_iclog_hdrs;	/* iclog hdrs in t_curr_res */
} xlog_ticket_t;

/*
 * - A log record header is 512 bytes.  There is plenty of room to grow the
 *	xlog_rec_header_t into the reserved space.
 * - ic_data follows, so a write to disk can start at the beginning of
 *	the iclog.
 * - ic_forcewait is used to implement synchronous forcing of the iclog to disk.
 * - ic_next is the pointer to the next iclog in the ring.
 * - ic_log is a pointer back to the global log structure.
 * - ic_size is the full size of the log buffer, minus the cycle headers.
 * - ic_offset is the current number of bytes written to in this iclog.
 * - ic_refcnt is bumped when someone is writing to the log.
 * - ic_state is the state of the iclog.
 *
 * Because of cacheline contention on large machines, we need to separate
 * various resources onto different cachelines. To start with, make the
 * structure cacheline aligned. The following fields can be contended on
 * by independent processes:
 *
 *	- ic_callbacks
 *	- ic_refcnt
 *	- fields protected by the global l_icloglock
 *
 * so we need to ensure that these fields are located in separate cachelines.
 * We'll put all the read-only and l_icloglock fields in the first cacheline,
 * and move everything else out to subsequent cachelines.
 */
typedef struct xlog_in_core {
	wait_queue_head_t	ic_force_wait;
	wait_queue_head_t	ic_write_wait;
	struct xlog_in_core	*ic_next;
	struct xlog_in_core	*ic_prev;
	struct xlog		*ic_log;
	u32			ic_size;
	u32			ic_offset;
	enum xlog_iclog_state	ic_state;
	unsigned int		ic_flags;
	void			*ic_datap;	/* pointer to iclog data */
	struct list_head	ic_callbacks;

	/* reference counts need their own cacheline */
	atomic_t		ic_refcnt ____cacheline_aligned_in_smp;
	xlog_in_core_2_t	*ic_data;
#define ic_header	ic_data->hic_header
#ifdef DEBUG
	bool			ic_fail_crc : 1;
#endif
	struct semaphore	ic_sema;
	struct work_struct	ic_end_io_work;
	struct bio		ic_bio;
	struct bio_vec		ic_bvec[];
} xlog_in_core_t;

/*
 * The CIL context is used to aggregate per-transaction details as well be
 * passed to the iclog for checkpoint post-commit processing.  After being
 * passed to the iclog, another context needs to be allocated for tracking the
 * next set of transactions to be aggregated into a checkpoint.
 */
struct xfs_cil;

struct xfs_cil_ctx {
	struct xfs_cil		*cil;
	xfs_csn_t		sequence;	/* chkpt sequence # */
	xfs_lsn_t		start_lsn;	/* first LSN of chkpt commit */
	xfs_lsn_t		commit_lsn;	/* chkpt commit record lsn */
	struct xlog_in_core	*commit_iclog;
	struct xlog_ticket	*ticket;	/* chkpt ticket */
	atomic_t		space_used;	/* aggregate size of regions */
	struct xfs_busy_extents	busy_extents;
	struct list_head	log_items;	/* log items in chkpt */
	struct list_head	lv_chain;	/* logvecs being pushed */
	struct list_head	iclog_entry;
	struct list_head	committing;	/* ctx committing list */
	struct work_struct	push_work;
	atomic_t		order_id;

	/*
	 * CPUs that could have added items to the percpu CIL data.  Access is
	 * coordinated with xc_ctx_lock.
	 */
	struct cpumask		cil_pcpmask;
};

/*
 * Per-cpu CIL tracking items
 */
struct xlog_cil_pcp {
	int32_t			space_used;
	uint32_t		space_reserved;
	struct list_head	busy_extents;
	struct list_head	log_items;
};

/*
 * Committed Item List structure
 *
 * This structure is used to track log items that have been committed but not
 * yet written into the log. It is used only when the delayed logging mount
 * option is enabled.
 *
 * This structure tracks the list of committing checkpoint contexts so
 * we can avoid the problem of having to hold out new transactions during a
 * flush until we have a the commit record LSN of the checkpoint. We can
 * traverse the list of committing contexts in xlog_cil_push_lsn() to find a
 * sequence match and extract the commit LSN directly from there. If the
 * checkpoint is still in the process of committing, we can block waiting for
 * the commit LSN to be determined as well. This should make synchronous
 * operations almost as efficient as the old logging methods.
 */
struct xfs_cil {
	struct xlog		*xc_log;
	unsigned long		xc_flags;
	atomic_t		xc_iclog_hdrs;
	struct workqueue_struct	*xc_push_wq;

	struct rw_semaphore	xc_ctx_lock ____cacheline_aligned_in_smp;
	struct xfs_cil_ctx	*xc_ctx;

	spinlock_t		xc_push_lock ____cacheline_aligned_in_smp;
	xfs_csn_t		xc_push_seq;
	bool			xc_push_commit_stable;
	struct list_head	xc_committing;
	wait_queue_head_t	xc_commit_wait;
	wait_queue_head_t	xc_start_wait;
	xfs_csn_t		xc_current_sequence;
	wait_queue_head_t	xc_push_wait;	/* background push throttle */

	void __percpu		*xc_pcp;	/* percpu CIL structures */
} ____cacheline_aligned_in_smp;

/* xc_flags bit values */
#define	XLOG_CIL_EMPTY		1
#define XLOG_CIL_PCP_SPACE	2

/*
 * The amount of log space we allow the CIL to aggregate is difficult to size.
 * Whatever we choose, we have to make sure we can get a reservation for the
 * log space effectively, that it is large enough to capture sufficient
 * relogging to reduce log buffer IO significantly, but it is not too large for
 * the log or induces too much latency when writing out through the iclogs. We
 * track both space consumed and the number of vectors in the checkpoint
 * context, so we need to decide which to use for limiting.
 *
 * Every log buffer we write out during a push needs a header reserved, which
 * is at least one sector and more for v2 logs. Hence we need a reservation of
 * at least 512 bytes per 32k of log space just for the LR headers. That means
 * 16KB of reservation per megabyte of delayed logging space we will consume,
 * plus various headers.  The number of headers will vary based on the num of
 * io vectors, so limiting on a specific number of vectors is going to result
 * in transactions of varying size. IOWs, it is more consistent to track and
 * limit space consumed in the log rather than by the number of objects being
 * logged in order to prevent checkpoint ticket overruns.
 *
 * Further, use of static reservations through the log grant mechanism is
 * problematic. It introduces a lot of complexity (e.g. reserve grant vs write
 * grant) and a significant deadlock potential because regranting write space
 * can block on log pushes. Hence if we have to regrant log space during a log
 * push, we can deadlock.
 *
 * However, we can avoid this by use of a dynamic "reservation stealing"
 * technique during transaction commit whereby unused reservation space in the
 * transaction ticket is transferred to the CIL ctx commit ticket to cover the
 * space needed by the checkpoint transaction. This means that we never need to
 * specifically reserve space for the CIL checkpoint transaction, nor do we
 * need to regrant space once the checkpoint completes. This also means the
 * checkpoint transaction ticket is specific to the checkpoint context, rather
 * than the CIL itself.
 *
 * With dynamic reservations, we can effectively make up arbitrary limits for
 * the checkpoint size so long as they don't violate any other size rules.
 * Recovery imposes a rule that no transaction exceed half the log, so we are
 * limited by that.  Furthermore, the log transaction reservation subsystem
 * tries to keep 25% of the log free, so we need to keep below that limit or we
 * risk running out of free log space to start any new transactions.
 *
 * In order to keep background CIL push efficient, we only need to ensure the
 * CIL is large enough to maintain sufficient in-memory relogging to avoid
 * repeated physical writes of frequently modified metadata. If we allow the CIL
 * to grow to a substantial fraction of the log, then we may be pinning hundreds
 * of megabytes of metadata in memory until the CIL flushes. This can cause
 * issues when we are running low on memory - pinned memory cannot be reclaimed,
 * and the CIL consumes a lot of memory. Hence we need to set an upper physical
 * size limit for the CIL that limits the maximum amount of memory pinned by the
 * CIL but does not limit performance by reducing relogging efficiency
 * significantly.
 *
 * As such, the CIL push threshold ends up being the smaller of two thresholds:
 * - a threshold large enough that it allows CIL to be pushed and progress to be
 *   made without excessive blocking of incoming transaction commits. This is
 *   defined to be 12.5% of the log space - half the 25% push threshold of the
 *   AIL.
 * - small enough that it doesn't pin excessive amounts of memory but maintains
 *   close to peak relogging efficiency. This is defined to be 16x the iclog
 *   buffer window (32MB) as measurements have shown this to be roughly the
 *   point of diminishing performance increases under highly concurrent
 *   modification workloads.
 *
 * To prevent the CIL from overflowing upper commit size bounds, we introduce a
 * new threshold at which we block committing transactions until the background
 * CIL commit commences and switches to a new context. While this is not a hard
 * limit, it forces the process committing a transaction to the CIL to block and
 * yeild the CPU, giving the CIL push work a chance to be scheduled and start
 * work. This prevents a process running lots of transactions from overfilling
 * the CIL because it is not yielding the CPU. We set the blocking limit at
 * twice the background push space threshold so we keep in line with the AIL
 * push thresholds.
 *
 * Note: this is not a -hard- limit as blocking is applied after the transaction
 * is inserted into the CIL and the push has been triggered. It is largely a
 * throttling mechanism that allows the CIL push to be scheduled and run. A hard
 * limit will be difficult to implement without introducing global serialisation
 * in the CIL commit fast path, and it's not at all clear that we actually need
 * such hard limits given the ~7 years we've run without a hard limit before
 * finding the first situation where a checkpoint size overflow actually
 * occurred. Hence the simple throttle, and an ASSERT check to tell us that
 * we've overrun the max size.
 */
#define XLOG_CIL_SPACE_LIMIT(log)	\
	min_t(int, (log)->l_logsize >> 3, BBTOB(XLOG_TOTAL_REC_SHIFT(log)) << 4)

#define XLOG_CIL_BLOCKING_SPACE_LIMIT(log)	\
	(XLOG_CIL_SPACE_LIMIT(log) * 2)

/*
 * ticket grant locks, queues and accounting have their own cachlines
 * as these are quite hot and can be operated on concurrently.
 */
struct xlog_grant_head {
	spinlock_t		lock ____cacheline_aligned_in_smp;
	struct list_head	waiters;
	atomic64_t		grant;
};

/*
 * The reservation head lsn is not made up of a cycle number and block number.
 * Instead, it uses a cycle number and byte number.  Logs don't expect to
 * overflow 31 bits worth of byte offset, so using a byte number will mean
 * that round off problems won't occur when releasing partial reservations.
 */
struct xlog {
	/* The following fields don't need locking */
	struct xfs_mount	*l_mp;	        /* mount point */
	struct xfs_ail		*l_ailp;	/* AIL log is working with */
	struct xfs_cil		*l_cilp;	/* CIL log is working with */
	struct xfs_buftarg	*l_targ;        /* buftarg of log */
	struct workqueue_struct	*l_ioend_workqueue; /* for I/O completions */
	struct delayed_work	l_work;		/* background flush work */
	long			l_opstate;	/* operational state */
	uint			l_quotaoffs_flag; /* XFS_DQ_*, for QUOTAOFFs */
	struct list_head	*l_buf_cancel_table;
	struct list_head	r_dfops;	/* recovered log intent items */
	int			l_iclog_hsize;  /* size of iclog header */
	int			l_iclog_heads;  /* # of iclog header sectors */
	uint			l_sectBBsize;   /* sector size in BBs (2^n) */
	int			l_iclog_size;	/* size of log in bytes */
	int			l_iclog_bufs;	/* number of iclog buffers */
	xfs_daddr_t		l_logBBstart;   /* start block of log */
	int			l_logsize;      /* size of log in bytes */
	int			l_logBBsize;    /* size of log in BB chunks */

	/* The following block of fields are changed while holding icloglock */
	wait_queue_head_t	l_flush_wait ____cacheline_aligned_in_smp;
						/* waiting for iclog flush */
	int			l_covered_state;/* state of "covering disk
						 * log entries" */
	xlog_in_core_t		*l_iclog;       /* head log queue	*/
	spinlock_t		l_icloglock;    /* grab to change iclog state */
	int			l_curr_cycle;   /* Cycle number of log writes */
	int			l_prev_cycle;   /* Cycle number before last
						 * block increment */
	int			l_curr_block;   /* current logical log block */
	int			l_prev_block;   /* previous logical log block */

	/*
	 * l_tail_lsn is atomic so it can be set and read without needing to
	 * hold specific locks. To avoid operations contending with other hot
	 * objects, it on a separate cacheline.
	 */
	/* lsn of 1st LR with unflushed * buffers */
	atomic64_t		l_tail_lsn ____cacheline_aligned_in_smp;

	struct xlog_grant_head	l_reserve_head;
	struct xlog_grant_head	l_write_head;
	uint64_t		l_tail_space;

	struct xfs_kobj		l_kobj;

	/* log recovery lsn tracking (for buffer submission */
	xfs_lsn_t		l_recovery_lsn;

	uint32_t		l_iclog_roundoff;/* padding roundoff */
};

/*
 * Bits for operational state
 */
#define XLOG_ACTIVE_RECOVERY	0	/* in the middle of recovery */
#define XLOG_RECOVERY_NEEDED	1	/* log was recovered */
#define XLOG_IO_ERROR		2	/* log hit an I/O error, and being
				   shutdown */
#define XLOG_TAIL_WARN		3	/* log tail verify warning issued */

static inline bool
xlog_recovery_needed(struct xlog *log)
{
	return test_bit(XLOG_RECOVERY_NEEDED, &log->l_opstate);
}

static inline bool
xlog_in_recovery(struct xlog *log)
{
	return test_bit(XLOG_ACTIVE_RECOVERY, &log->l_opstate);
}

static inline bool
xlog_is_shutdown(struct xlog *log)
{
	return test_bit(XLOG_IO_ERROR, &log->l_opstate);
}

/*
 * Wait until the xlog_force_shutdown() has marked the log as shut down
 * so xlog_is_shutdown() will always return true.
 */
static inline void
xlog_shutdown_wait(
	struct xlog	*log)
{
	wait_var_event(&log->l_opstate, xlog_is_shutdown(log));
}

/* common routines */
extern int
xlog_recover(
	struct xlog		*log);
extern int
xlog_recover_finish(
	struct xlog		*log);
extern void
xlog_recover_cancel(struct xlog *);

extern __le32	 xlog_cksum(struct xlog *log, struct xlog_rec_header *rhead,
			    char *dp, int size);

extern struct kmem_cache *xfs_log_ticket_cache;
struct xlog_ticket *xlog_ticket_alloc(struct xlog *log, int unit_bytes,
		int count, bool permanent);

void	xlog_print_tic_res(struct xfs_mount *mp, struct xlog_ticket *ticket);
void	xlog_print_trans(struct xfs_trans *);
int	xlog_write(struct xlog *log, struct xfs_cil_ctx *ctx,
		struct list_head *lv_chain, struct xlog_ticket *tic,
		uint32_t len);
void	xfs_log_ticket_ungrant(struct xlog *log, struct xlog_ticket *ticket);
void	xfs_log_ticket_regrant(struct xlog *log, struct xlog_ticket *ticket);

void xlog_state_switch_iclogs(struct xlog *log, struct xlog_in_core *iclog,
		int eventual_size);
int xlog_state_release_iclog(struct xlog *log, struct xlog_in_core *iclog,
		struct xlog_ticket *ticket);

/*
 * When we crack an atomic LSN, we sample it first so that the value will not
 * change while we are cracking it into the component values. This means we
 * will always get consistent component values to work from. This should always
 * be used to sample and crack LSNs that are stored and updated in atomic
 * variables.
 */
static inline void
xlog_crack_atomic_lsn(atomic64_t *lsn, uint *cycle, uint *block)
{
	xfs_lsn_t val = atomic64_read(lsn);

	*cycle = CYCLE_LSN(val);
	*block = BLOCK_LSN(val);
}

/*
 * Calculate and assign a value to an atomic LSN variable from component pieces.
 */
static inline void
xlog_assign_atomic_lsn(atomic64_t *lsn, uint cycle, uint block)
{
	atomic64_set(lsn, xlog_assign_lsn(cycle, block));
}

/*
 * Committed Item List interfaces
 */
int	xlog_cil_init(struct xlog *log);
void	xlog_cil_init_post_recovery(struct xlog *log);
void	xlog_cil_destroy(struct xlog *log);
bool	xlog_cil_empty(struct xlog *log);
void	xlog_cil_commit(struct xlog *log, struct xfs_trans *tp,
			xfs_csn_t *commit_seq, bool regrant);
void	xlog_cil_set_ctx_write_state(struct xfs_cil_ctx *ctx,
			struct xlog_in_core *iclog);


/*
 * CIL force routines
 */
void xlog_cil_flush(struct xlog *log);
xfs_lsn_t xlog_cil_force_seq(struct xlog *log, xfs_csn_t sequence);

static inline void
xlog_cil_force(struct xlog *log)
{
	xlog_cil_force_seq(log, log->l_cilp->xc_current_sequence);
}

/*
 * Wrapper function for waiting on a wait queue serialised against wakeups
 * by a spinlock. This matches the semantics of all the wait queues used in the
 * log code.
 */
static inline void
xlog_wait(
	struct wait_queue_head	*wq,
	struct spinlock		*lock)
		__releases(lock)
{
	DECLARE_WAITQUEUE(wait, current);

	add_wait_queue_exclusive(wq, &wait);
	__set_current_state(TASK_UNINTERRUPTIBLE);
	spin_unlock(lock);
	schedule();
	remove_wait_queue(wq, &wait);
}

int xlog_wait_on_iclog(struct xlog_in_core *iclog)
		__releases(iclog->ic_log->l_icloglock);

/* Calculate the distance between two LSNs in bytes */
static inline uint64_t
xlog_lsn_sub(
	struct xlog	*log,
	xfs_lsn_t	high,
	xfs_lsn_t	low)
{
	uint32_t	hi_cycle = CYCLE_LSN(high);
	uint32_t	hi_block = BLOCK_LSN(high);
	uint32_t	lo_cycle = CYCLE_LSN(low);
	uint32_t	lo_block = BLOCK_LSN(low);

	if (hi_cycle == lo_cycle)
		return BBTOB(hi_block - lo_block);
	ASSERT((hi_cycle == lo_cycle + 1) || xlog_is_shutdown(log));
	return (uint64_t)log->l_logsize - BBTOB(lo_block - hi_block);
}

void xlog_grant_return_space(struct xlog *log, xfs_lsn_t old_head,
		xfs_lsn_t new_head);

/*
 * The LSN is valid so long as it is behind the current LSN. If it isn't, this
 * means that the next log record that includes this metadata could have a
 * smaller LSN. In turn, this means that the modification in the log would not
 * replay.
 */
static inline bool
xlog_valid_lsn(
	struct xlog	*log,
	xfs_lsn_t	lsn)
{
	int		cur_cycle;
	int		cur_block;
	bool		valid = true;

	/*
	 * First, sample the current lsn without locking to avoid added
	 * contention from metadata I/O. The current cycle and block are updated
	 * (in xlog_state_switch_iclogs()) and read here in a particular order
	 * to avoid false negatives (e.g., thinking the metadata LSN is valid
	 * when it is not).
	 *
	 * The current block is always rewound before the cycle is bumped in
	 * xlog_state_switch_iclogs() to ensure the current LSN is never seen in
	 * a transiently forward state. Instead, we can see the LSN in a
	 * transiently behind state if we happen to race with a cycle wrap.
	 */
	cur_cycle = READ_ONCE(log->l_curr_cycle);
	smp_rmb();
	cur_block = READ_ONCE(log->l_curr_block);

	if ((CYCLE_LSN(lsn) > cur_cycle) ||
	    (CYCLE_LSN(lsn) == cur_cycle && BLOCK_LSN(lsn) > cur_block)) {
		/*
		 * If the metadata LSN appears invalid, it's possible the check
		 * above raced with a wrap to the next log cycle. Grab the lock
		 * to check for sure.
		 */
		spin_lock(&log->l_icloglock);
		cur_cycle = log->l_curr_cycle;
		cur_block = log->l_curr_block;
		spin_unlock(&log->l_icloglock);

		if ((CYCLE_LSN(lsn) > cur_cycle) ||
		    (CYCLE_LSN(lsn) == cur_cycle && BLOCK_LSN(lsn) > cur_block))
			valid = false;
	}

	return valid;
}

/*
 * Log vector and shadow buffers can be large, so we need to use kvmalloc() here
 * to ensure success. Unfortunately, kvmalloc() only allows GFP_KERNEL contexts
 * to fall back to vmalloc, so we can't actually do anything useful with gfp
 * flags to control the kmalloc() behaviour within kvmalloc(). Hence kmalloc()
 * will do direct reclaim and compaction in the slow path, both of which are
 * horrendously expensive. We just want kmalloc to fail fast and fall back to
 * vmalloc if it can't get something straight away from the free lists or
 * buddy allocator. Hence we have to open code kvmalloc outselves here.
 *
 * This assumes that the caller uses memalloc_nofs_save task context here, so
 * despite the use of GFP_KERNEL here, we are going to be doing GFP_NOFS
 * allocations. This is actually the only way to make vmalloc() do GFP_NOFS
 * allocations, so lets just all pretend this is a GFP_KERNEL context
 * operation....
 */
static inline void *
xlog_kvmalloc(
	size_t		buf_size)
{
	gfp_t		flags = GFP_KERNEL;
	void		*p;

	flags &= ~__GFP_DIRECT_RECLAIM;
	flags |= __GFP_NOWARN | __GFP_NORETRY;
	do {
		p = kmalloc(buf_size, flags);
		if (!p)
			p = vmalloc(buf_size);
	} while (!p);

	return p;
}

#endif	/* __XFS_LOG_PRIV_H__ */