1// SPDX-License-Identifier: GPL-2.0
2/*
3 * Copyright (c) 2000-2003,2005 Silicon Graphics, Inc.
4 * All Rights Reserved.
5 */
6#ifndef __XFS_LOG_PRIV_H__
7#define __XFS_LOG_PRIV_H__
8
9#include "xfs_extent_busy.h" /* for struct xfs_busy_extents */
10
11struct xfs_buf;
12struct xlog;
13struct xlog_ticket;
14struct xfs_mount;
15
16/*
17 * get client id from packed copy.
18 *
19 * this hack is here because the xlog_pack code copies four bytes
20 * of xlog_op_header containing the fields oh_clientid, oh_flags
21 * and oh_res2 into the packed copy.
22 *
23 * later on this four byte chunk is treated as an int and the
24 * client id is pulled out.
25 *
26 * this has endian issues, of course.
27 */
28static inline uint xlog_get_client_id(__be32 i)
29{
30 return be32_to_cpu(i) >> 24;
31}
32
33/*
34 * In core log state
35 */
36enum xlog_iclog_state {
37 XLOG_STATE_ACTIVE, /* Current IC log being written to */
38 XLOG_STATE_WANT_SYNC, /* Want to sync this iclog; no more writes */
39 XLOG_STATE_SYNCING, /* This IC log is syncing */
40 XLOG_STATE_DONE_SYNC, /* Done syncing to disk */
41 XLOG_STATE_CALLBACK, /* Callback functions now */
42 XLOG_STATE_DIRTY, /* Dirty IC log, not ready for ACTIVE status */
43};
44
45#define XLOG_STATE_STRINGS \
46 { XLOG_STATE_ACTIVE, "XLOG_STATE_ACTIVE" }, \
47 { XLOG_STATE_WANT_SYNC, "XLOG_STATE_WANT_SYNC" }, \
48 { XLOG_STATE_SYNCING, "XLOG_STATE_SYNCING" }, \
49 { XLOG_STATE_DONE_SYNC, "XLOG_STATE_DONE_SYNC" }, \
50 { XLOG_STATE_CALLBACK, "XLOG_STATE_CALLBACK" }, \
51 { XLOG_STATE_DIRTY, "XLOG_STATE_DIRTY" }
52
53/*
54 * In core log flags
55 */
56#define XLOG_ICL_NEED_FLUSH (1u << 0) /* iclog needs REQ_PREFLUSH */
57#define XLOG_ICL_NEED_FUA (1u << 1) /* iclog needs REQ_FUA */
58
59#define XLOG_ICL_STRINGS \
60 { XLOG_ICL_NEED_FLUSH, "XLOG_ICL_NEED_FLUSH" }, \
61 { XLOG_ICL_NEED_FUA, "XLOG_ICL_NEED_FUA" }
62
63
64/*
65 * Log ticket flags
66 */
67#define XLOG_TIC_PERM_RESERV (1u << 0) /* permanent reservation */
68
69#define XLOG_TIC_FLAGS \
70 { XLOG_TIC_PERM_RESERV, "XLOG_TIC_PERM_RESERV" }
71
72/*
73 * Below are states for covering allocation transactions.
74 * By covering, we mean changing the h_tail_lsn in the last on-disk
75 * log write such that no allocation transactions will be re-done during
76 * recovery after a system crash. Recovery starts at the last on-disk
77 * log write.
78 *
79 * These states are used to insert dummy log entries to cover
80 * space allocation transactions which can undo non-transactional changes
81 * after a crash. Writes to a file with space
82 * already allocated do not result in any transactions. Allocations
83 * might include space beyond the EOF. So if we just push the EOF a
84 * little, the last transaction for the file could contain the wrong
85 * size. If there is no file system activity, after an allocation
86 * transaction, and the system crashes, the allocation transaction
87 * will get replayed and the file will be truncated. This could
88 * be hours/days/... after the allocation occurred.
89 *
90 * The fix for this is to do two dummy transactions when the
91 * system is idle. We need two dummy transaction because the h_tail_lsn
92 * in the log record header needs to point beyond the last possible
93 * non-dummy transaction. The first dummy changes the h_tail_lsn to
94 * the first transaction before the dummy. The second dummy causes
95 * h_tail_lsn to point to the first dummy. Recovery starts at h_tail_lsn.
96 *
97 * These dummy transactions get committed when everything
98 * is idle (after there has been some activity).
99 *
100 * There are 5 states used to control this.
101 *
102 * IDLE -- no logging has been done on the file system or
103 * we are done covering previous transactions.
104 * NEED -- logging has occurred and we need a dummy transaction
105 * when the log becomes idle.
106 * DONE -- we were in the NEED state and have committed a dummy
107 * transaction.
108 * NEED2 -- we detected that a dummy transaction has gone to the
109 * on disk log with no other transactions.
110 * DONE2 -- we committed a dummy transaction when in the NEED2 state.
111 *
112 * There are two places where we switch states:
113 *
114 * 1.) In xfs_sync, when we detect an idle log and are in NEED or NEED2.
115 * We commit the dummy transaction and switch to DONE or DONE2,
116 * respectively. In all other states, we don't do anything.
117 *
118 * 2.) When we finish writing the on-disk log (xlog_state_clean_log).
119 *
120 * No matter what state we are in, if this isn't the dummy
121 * transaction going out, the next state is NEED.
122 * So, if we aren't in the DONE or DONE2 states, the next state
123 * is NEED. We can't be finishing a write of the dummy record
124 * unless it was committed and the state switched to DONE or DONE2.
125 *
126 * If we are in the DONE state and this was a write of the
127 * dummy transaction, we move to NEED2.
128 *
129 * If we are in the DONE2 state and this was a write of the
130 * dummy transaction, we move to IDLE.
131 *
132 *
133 * Writing only one dummy transaction can get appended to
134 * one file space allocation. When this happens, the log recovery
135 * code replays the space allocation and a file could be truncated.
136 * This is why we have the NEED2 and DONE2 states before going idle.
137 */
138
139#define XLOG_STATE_COVER_IDLE 0
140#define XLOG_STATE_COVER_NEED 1
141#define XLOG_STATE_COVER_DONE 2
142#define XLOG_STATE_COVER_NEED2 3
143#define XLOG_STATE_COVER_DONE2 4
144
145#define XLOG_COVER_OPS 5
146
147struct xlog_ticket {
148 struct list_head t_queue; /* reserve/write queue */
149 struct task_struct *t_task; /* task that owns this ticket */
150 xlog_tid_t t_tid; /* transaction identifier */
151 atomic_t t_ref; /* ticket reference count */
152 int t_curr_res; /* current reservation */
153 int t_unit_res; /* unit reservation */
154 char t_ocnt; /* original unit count */
155 char t_cnt; /* current unit count */
156 uint8_t t_flags; /* properties of reservation */
157 int t_iclog_hdrs; /* iclog hdrs in t_curr_res */
158};
159
160/*
161 * In-core log structure.
162 *
163 * - ic_forcewait is used to implement synchronous forcing of the iclog to disk.
164 * - ic_next is the pointer to the next iclog in the ring.
165 * - ic_log is a pointer back to the global log structure.
166 * - ic_size is the full size of the log buffer, minus the cycle headers.
167 * - ic_offset is the current number of bytes written to in this iclog.
168 * - ic_refcnt is bumped when someone is writing to the log.
169 * - ic_state is the state of the iclog.
170 *
171 * Because of cacheline contention on large machines, we need to separate
172 * various resources onto different cachelines. To start with, make the
173 * structure cacheline aligned. The following fields can be contended on
174 * by independent processes:
175 *
176 * - ic_callbacks
177 * - ic_refcnt
178 * - fields protected by the global l_icloglock
179 *
180 * so we need to ensure that these fields are located in separate cachelines.
181 * We'll put all the read-only and l_icloglock fields in the first cacheline,
182 * and move everything else out to subsequent cachelines.
183 */
184struct xlog_in_core {
185 wait_queue_head_t ic_force_wait;
186 wait_queue_head_t ic_write_wait;
187 struct xlog_in_core *ic_next;
188 struct xlog_in_core *ic_prev;
189 struct xlog *ic_log;
190 u32 ic_size;
191 u32 ic_offset;
192 enum xlog_iclog_state ic_state;
193 unsigned int ic_flags;
194 void *ic_datap; /* pointer to iclog data */
195 struct list_head ic_callbacks;
196
197 /* reference counts need their own cacheline */
198 atomic_t ic_refcnt ____cacheline_aligned_in_smp;
199 struct xlog_rec_header *ic_header;
200#ifdef DEBUG
201 bool ic_fail_crc : 1;
202#endif
203 struct semaphore ic_sema;
204 struct work_struct ic_end_io_work;
205 struct bio ic_bio;
206 struct bio_vec ic_bvec[];
207};
208
209/*
210 * The CIL context is used to aggregate per-transaction details as well be
211 * passed to the iclog for checkpoint post-commit processing. After being
212 * passed to the iclog, another context needs to be allocated for tracking the
213 * next set of transactions to be aggregated into a checkpoint.
214 */
215struct xfs_cil;
216
217struct xfs_cil_ctx {
218 struct xfs_cil *cil;
219 xfs_csn_t sequence; /* chkpt sequence # */
220 xfs_lsn_t start_lsn; /* first LSN of chkpt commit */
221 xfs_lsn_t commit_lsn; /* chkpt commit record lsn */
222 struct xlog_in_core *commit_iclog;
223 struct xlog_ticket *ticket; /* chkpt ticket */
224 atomic_t space_used; /* aggregate size of regions */
225 struct xfs_busy_extents busy_extents;
226 struct list_head log_items; /* log items in chkpt */
227 struct list_head lv_chain; /* logvecs being pushed */
228 struct list_head iclog_entry;
229 struct list_head committing; /* ctx committing list */
230 struct work_struct push_work;
231 atomic_t order_id;
232
233 /*
234 * CPUs that could have added items to the percpu CIL data. Access is
235 * coordinated with xc_ctx_lock.
236 */
237 struct cpumask cil_pcpmask;
238};
239
240/*
241 * Per-cpu CIL tracking items
242 */
243struct xlog_cil_pcp {
244 int32_t space_used;
245 uint32_t space_reserved;
246 struct list_head busy_extents;
247 struct list_head log_items;
248};
249
250/*
251 * Committed Item List structure
252 *
253 * This structure is used to track log items that have been committed but not
254 * yet written into the log. It is used only when the delayed logging mount
255 * option is enabled.
256 *
257 * This structure tracks the list of committing checkpoint contexts so
258 * we can avoid the problem of having to hold out new transactions during a
259 * flush until we have a the commit record LSN of the checkpoint. We can
260 * traverse the list of committing contexts in xlog_cil_push_lsn() to find a
261 * sequence match and extract the commit LSN directly from there. If the
262 * checkpoint is still in the process of committing, we can block waiting for
263 * the commit LSN to be determined as well. This should make synchronous
264 * operations almost as efficient as the old logging methods.
265 */
266struct xfs_cil {
267 struct xlog *xc_log;
268 unsigned long xc_flags;
269 atomic_t xc_iclog_hdrs;
270 struct workqueue_struct *xc_push_wq;
271
272 struct rw_semaphore xc_ctx_lock ____cacheline_aligned_in_smp;
273 struct xfs_cil_ctx *xc_ctx;
274
275 spinlock_t xc_push_lock ____cacheline_aligned_in_smp;
276 xfs_csn_t xc_push_seq;
277 bool xc_push_commit_stable;
278 struct list_head xc_committing;
279 wait_queue_head_t xc_commit_wait;
280 wait_queue_head_t xc_start_wait;
281 xfs_csn_t xc_current_sequence;
282 wait_queue_head_t xc_push_wait; /* background push throttle */
283
284 void __percpu *xc_pcp; /* percpu CIL structures */
285} ____cacheline_aligned_in_smp;
286
287/* xc_flags bit values */
288#define XLOG_CIL_EMPTY 1
289#define XLOG_CIL_PCP_SPACE 2
290
291/*
292 * The amount of log space we allow the CIL to aggregate is difficult to size.
293 * Whatever we choose, we have to make sure we can get a reservation for the
294 * log space effectively, that it is large enough to capture sufficient
295 * relogging to reduce log buffer IO significantly, but it is not too large for
296 * the log or induces too much latency when writing out through the iclogs. We
297 * track both space consumed and the number of vectors in the checkpoint
298 * context, so we need to decide which to use for limiting.
299 *
300 * Every log buffer we write out during a push needs a header reserved, which
301 * is at least one sector and more for v2 logs. Hence we need a reservation of
302 * at least 512 bytes per 32k of log space just for the LR headers. That means
303 * 16KB of reservation per megabyte of delayed logging space we will consume,
304 * plus various headers. The number of headers will vary based on the num of
305 * io vectors, so limiting on a specific number of vectors is going to result
306 * in transactions of varying size. IOWs, it is more consistent to track and
307 * limit space consumed in the log rather than by the number of objects being
308 * logged in order to prevent checkpoint ticket overruns.
309 *
310 * Further, use of static reservations through the log grant mechanism is
311 * problematic. It introduces a lot of complexity (e.g. reserve grant vs write
312 * grant) and a significant deadlock potential because regranting write space
313 * can block on log pushes. Hence if we have to regrant log space during a log
314 * push, we can deadlock.
315 *
316 * However, we can avoid this by use of a dynamic "reservation stealing"
317 * technique during transaction commit whereby unused reservation space in the
318 * transaction ticket is transferred to the CIL ctx commit ticket to cover the
319 * space needed by the checkpoint transaction. This means that we never need to
320 * specifically reserve space for the CIL checkpoint transaction, nor do we
321 * need to regrant space once the checkpoint completes. This also means the
322 * checkpoint transaction ticket is specific to the checkpoint context, rather
323 * than the CIL itself.
324 *
325 * With dynamic reservations, we can effectively make up arbitrary limits for
326 * the checkpoint size so long as they don't violate any other size rules.
327 * Recovery imposes a rule that no transaction exceed half the log, so we are
328 * limited by that. Furthermore, the log transaction reservation subsystem
329 * tries to keep 25% of the log free, so we need to keep below that limit or we
330 * risk running out of free log space to start any new transactions.
331 *
332 * In order to keep background CIL push efficient, we only need to ensure the
333 * CIL is large enough to maintain sufficient in-memory relogging to avoid
334 * repeated physical writes of frequently modified metadata. If we allow the CIL
335 * to grow to a substantial fraction of the log, then we may be pinning hundreds
336 * of megabytes of metadata in memory until the CIL flushes. This can cause
337 * issues when we are running low on memory - pinned memory cannot be reclaimed,
338 * and the CIL consumes a lot of memory. Hence we need to set an upper physical
339 * size limit for the CIL that limits the maximum amount of memory pinned by the
340 * CIL but does not limit performance by reducing relogging efficiency
341 * significantly.
342 *
343 * As such, the CIL push threshold ends up being the smaller of two thresholds:
344 * - a threshold large enough that it allows CIL to be pushed and progress to be
345 * made without excessive blocking of incoming transaction commits. This is
346 * defined to be 12.5% of the log space - half the 25% push threshold of the
347 * AIL.
348 * - small enough that it doesn't pin excessive amounts of memory but maintains
349 * close to peak relogging efficiency. This is defined to be 16x the iclog
350 * buffer window (32MB) as measurements have shown this to be roughly the
351 * point of diminishing performance increases under highly concurrent
352 * modification workloads.
353 *
354 * To prevent the CIL from overflowing upper commit size bounds, we introduce a
355 * new threshold at which we block committing transactions until the background
356 * CIL commit commences and switches to a new context. While this is not a hard
357 * limit, it forces the process committing a transaction to the CIL to block and
358 * yeild the CPU, giving the CIL push work a chance to be scheduled and start
359 * work. This prevents a process running lots of transactions from overfilling
360 * the CIL because it is not yielding the CPU. We set the blocking limit at
361 * twice the background push space threshold so we keep in line with the AIL
362 * push thresholds.
363 *
364 * Note: this is not a -hard- limit as blocking is applied after the transaction
365 * is inserted into the CIL and the push has been triggered. It is largely a
366 * throttling mechanism that allows the CIL push to be scheduled and run. A hard
367 * limit will be difficult to implement without introducing global serialisation
368 * in the CIL commit fast path, and it's not at all clear that we actually need
369 * such hard limits given the ~7 years we've run without a hard limit before
370 * finding the first situation where a checkpoint size overflow actually
371 * occurred. Hence the simple throttle, and an ASSERT check to tell us that
372 * we've overrun the max size.
373 */
374#define XLOG_CIL_SPACE_LIMIT(log) \
375 min_t(int, (log)->l_logsize >> 3, BBTOB(XLOG_TOTAL_REC_SHIFT(log)) << 4)
376
377#define XLOG_CIL_BLOCKING_SPACE_LIMIT(log) \
378 (XLOG_CIL_SPACE_LIMIT(log) * 2)
379
380/*
381 * ticket grant locks, queues and accounting have their own cachlines
382 * as these are quite hot and can be operated on concurrently.
383 */
384struct xlog_grant_head {
385 spinlock_t lock ____cacheline_aligned_in_smp;
386 struct list_head waiters;
387 atomic64_t grant;
388};
389
390/*
391 * The reservation head lsn is not made up of a cycle number and block number.
392 * Instead, it uses a cycle number and byte number. Logs don't expect to
393 * overflow 31 bits worth of byte offset, so using a byte number will mean
394 * that round off problems won't occur when releasing partial reservations.
395 */
396struct xlog {
397 /* The following fields don't need locking */
398 struct xfs_mount *l_mp; /* mount point */
399 struct xfs_ail *l_ailp; /* AIL log is working with */
400 struct xfs_cil *l_cilp; /* CIL log is working with */
401 struct xfs_buftarg *l_targ; /* buftarg of log */
402 struct workqueue_struct *l_ioend_workqueue; /* for I/O completions */
403 struct delayed_work l_work; /* background flush work */
404 long l_opstate; /* operational state */
405 uint l_quotaoffs_flag; /* XFS_DQ_*, for QUOTAOFFs */
406 struct list_head *l_buf_cancel_table;
407 struct list_head r_dfops; /* recovered log intent items */
408 int l_iclog_hsize; /* size of iclog header */
409 uint l_sectBBsize; /* sector size in BBs (2^n) */
410 int l_iclog_size; /* size of log in bytes */
411 int l_iclog_bufs; /* number of iclog buffers */
412 xfs_daddr_t l_logBBstart; /* start block of log */
413 int l_logsize; /* size of log in bytes */
414 int l_logBBsize; /* size of log in BB chunks */
415
416 /* The following block of fields are changed while holding icloglock */
417 wait_queue_head_t l_flush_wait ____cacheline_aligned_in_smp;
418 /* waiting for iclog flush */
419 int l_covered_state;/* state of "covering disk
420 * log entries" */
421 struct xlog_in_core *l_iclog; /* head log queue */
422 spinlock_t l_icloglock; /* grab to change iclog state */
423 int l_curr_cycle; /* Cycle number of log writes */
424 int l_prev_cycle; /* Cycle number before last
425 * block increment */
426 int l_curr_block; /* current logical log block */
427 int l_prev_block; /* previous logical log block */
428
429 /*
430 * l_tail_lsn is atomic so it can be set and read without needing to
431 * hold specific locks. To avoid operations contending with other hot
432 * objects, it on a separate cacheline.
433 */
434 /* lsn of 1st LR with unflushed * buffers */
435 atomic64_t l_tail_lsn ____cacheline_aligned_in_smp;
436
437 struct xlog_grant_head l_reserve_head;
438 struct xlog_grant_head l_write_head;
439 uint64_t l_tail_space;
440
441 struct xfs_kobj l_kobj;
442
443 /* log recovery lsn tracking (for buffer submission */
444 xfs_lsn_t l_recovery_lsn;
445
446 uint32_t l_iclog_roundoff;/* padding roundoff */
447};
448
449/*
450 * Bits for operational state
451 */
452#define XLOG_ACTIVE_RECOVERY 0 /* in the middle of recovery */
453#define XLOG_RECOVERY_NEEDED 1 /* log was recovered */
454#define XLOG_IO_ERROR 2 /* log hit an I/O error, and being
455 shutdown */
456#define XLOG_TAIL_WARN 3 /* log tail verify warning issued */
457#define XLOG_SHUTDOWN_STARTED 4 /* xlog_force_shutdown() exclusion */
458
459static inline bool
460xlog_recovery_needed(struct xlog *log)
461{
462 return test_bit(XLOG_RECOVERY_NEEDED, &log->l_opstate);
463}
464
465static inline bool
466xlog_in_recovery(struct xlog *log)
467{
468 return test_bit(XLOG_ACTIVE_RECOVERY, &log->l_opstate);
469}
470
471static inline bool
472xlog_is_shutdown(struct xlog *log)
473{
474 return test_bit(XLOG_IO_ERROR, &log->l_opstate);
475}
476
477/*
478 * Wait until the xlog_force_shutdown() has marked the log as shut down
479 * so xlog_is_shutdown() will always return true.
480 */
481static inline void
482xlog_shutdown_wait(
483 struct xlog *log)
484{
485 wait_var_event(&log->l_opstate, xlog_is_shutdown(log));
486}
487
488/* common routines */
489extern int
490xlog_recover(
491 struct xlog *log);
492extern int
493xlog_recover_finish(
494 struct xlog *log);
495extern void
496xlog_recover_cancel(struct xlog *);
497
498__le32 xlog_cksum(struct xlog *log, struct xlog_rec_header *rhead,
499 char *dp, unsigned int hdrsize, unsigned int size);
500
501extern struct kmem_cache *xfs_log_ticket_cache;
502struct xlog_ticket *xlog_ticket_alloc(struct xlog *log, int unit_bytes,
503 int count, bool permanent);
504
505void xlog_print_tic_res(struct xfs_mount *mp, struct xlog_ticket *ticket);
506void xlog_print_trans(struct xfs_trans *);
507int xlog_write(struct xlog *log, struct xfs_cil_ctx *ctx,
508 struct list_head *lv_chain, struct xlog_ticket *tic,
509 uint32_t len);
510void xfs_log_ticket_ungrant(struct xlog *log, struct xlog_ticket *ticket);
511void xfs_log_ticket_regrant(struct xlog *log, struct xlog_ticket *ticket);
512
513void xlog_state_switch_iclogs(struct xlog *log, struct xlog_in_core *iclog,
514 int eventual_size);
515int xlog_state_release_iclog(struct xlog *log, struct xlog_in_core *iclog,
516 struct xlog_ticket *ticket);
517
518/*
519 * When we crack an atomic LSN, we sample it first so that the value will not
520 * change while we are cracking it into the component values. This means we
521 * will always get consistent component values to work from. This should always
522 * be used to sample and crack LSNs that are stored and updated in atomic
523 * variables.
524 */
525static inline void
526xlog_crack_atomic_lsn(atomic64_t *lsn, uint *cycle, uint *block)
527{
528 xfs_lsn_t val = atomic64_read(lsn);
529
530 *cycle = CYCLE_LSN(val);
531 *block = BLOCK_LSN(val);
532}
533
534/*
535 * Calculate and assign a value to an atomic LSN variable from component pieces.
536 */
537static inline void
538xlog_assign_atomic_lsn(atomic64_t *lsn, uint cycle, uint block)
539{
540 atomic64_set(v: lsn, i: xlog_assign_lsn(cycle, block));
541}
542
543/*
544 * Committed Item List interfaces
545 */
546int xlog_cil_init(struct xlog *log);
547void xlog_cil_init_post_recovery(struct xlog *log);
548void xlog_cil_destroy(struct xlog *log);
549bool xlog_cil_empty(struct xlog *log);
550void xlog_cil_commit(struct xlog *log, struct xfs_trans *tp,
551 xfs_csn_t *commit_seq, bool regrant);
552void xlog_cil_set_ctx_write_state(struct xfs_cil_ctx *ctx,
553 struct xlog_in_core *iclog);
554
555
556/*
557 * CIL force routines
558 */
559void xlog_cil_flush(struct xlog *log);
560xfs_lsn_t xlog_cil_force_seq(struct xlog *log, xfs_csn_t sequence);
561
562static inline void
563xlog_cil_force(struct xlog *log)
564{
565 xlog_cil_force_seq(log, log->l_cilp->xc_current_sequence);
566}
567
568/*
569 * Wrapper function for waiting on a wait queue serialised against wakeups
570 * by a spinlock. This matches the semantics of all the wait queues used in the
571 * log code.
572 */
573static inline void
574xlog_wait(
575 struct wait_queue_head *wq,
576 struct spinlock *lock)
577 __releases(lock)
578{
579 DECLARE_WAITQUEUE(wait, current);
580
581 add_wait_queue_exclusive(wq_head: wq, wq_entry: &wait);
582 __set_current_state(TASK_UNINTERRUPTIBLE);
583 spin_unlock(lock);
584 schedule();
585 remove_wait_queue(wq_head: wq, wq_entry: &wait);
586}
587
588int xlog_wait_on_iclog(struct xlog_in_core *iclog)
589 __releases(iclog->ic_log->l_icloglock);
590
591/* Calculate the distance between two LSNs in bytes */
592static inline uint64_t
593xlog_lsn_sub(
594 struct xlog *log,
595 xfs_lsn_t high,
596 xfs_lsn_t low)
597{
598 uint32_t hi_cycle = CYCLE_LSN(high);
599 uint32_t hi_block = BLOCK_LSN(high);
600 uint32_t lo_cycle = CYCLE_LSN(low);
601 uint32_t lo_block = BLOCK_LSN(low);
602
603 if (hi_cycle == lo_cycle)
604 return BBTOB(hi_block - lo_block);
605 ASSERT((hi_cycle == lo_cycle + 1) || xlog_is_shutdown(log));
606 return (uint64_t)log->l_logsize - BBTOB(lo_block - hi_block);
607}
608
609void xlog_grant_return_space(struct xlog *log, xfs_lsn_t old_head,
610 xfs_lsn_t new_head);
611
612/*
613 * The LSN is valid so long as it is behind the current LSN. If it isn't, this
614 * means that the next log record that includes this metadata could have a
615 * smaller LSN. In turn, this means that the modification in the log would not
616 * replay.
617 */
618static inline bool
619xlog_valid_lsn(
620 struct xlog *log,
621 xfs_lsn_t lsn)
622{
623 int cur_cycle;
624 int cur_block;
625 bool valid = true;
626
627 /*
628 * First, sample the current lsn without locking to avoid added
629 * contention from metadata I/O. The current cycle and block are updated
630 * (in xlog_state_switch_iclogs()) and read here in a particular order
631 * to avoid false negatives (e.g., thinking the metadata LSN is valid
632 * when it is not).
633 *
634 * The current block is always rewound before the cycle is bumped in
635 * xlog_state_switch_iclogs() to ensure the current LSN is never seen in
636 * a transiently forward state. Instead, we can see the LSN in a
637 * transiently behind state if we happen to race with a cycle wrap.
638 */
639 cur_cycle = READ_ONCE(log->l_curr_cycle);
640 smp_rmb();
641 cur_block = READ_ONCE(log->l_curr_block);
642
643 if ((CYCLE_LSN(lsn) > cur_cycle) ||
644 (CYCLE_LSN(lsn) == cur_cycle && BLOCK_LSN(lsn) > cur_block)) {
645 /*
646 * If the metadata LSN appears invalid, it's possible the check
647 * above raced with a wrap to the next log cycle. Grab the lock
648 * to check for sure.
649 */
650 spin_lock(lock: &log->l_icloglock);
651 cur_cycle = log->l_curr_cycle;
652 cur_block = log->l_curr_block;
653 spin_unlock(lock: &log->l_icloglock);
654
655 if ((CYCLE_LSN(lsn) > cur_cycle) ||
656 (CYCLE_LSN(lsn) == cur_cycle && BLOCK_LSN(lsn) > cur_block))
657 valid = false;
658 }
659
660 return valid;
661}
662
663/*
664 * Log vector and shadow buffers can be large, so we need to use kvmalloc() here
665 * to ensure success. Unfortunately, kvmalloc() only allows GFP_KERNEL contexts
666 * to fall back to vmalloc, so we can't actually do anything useful with gfp
667 * flags to control the kmalloc() behaviour within kvmalloc(). Hence kmalloc()
668 * will do direct reclaim and compaction in the slow path, both of which are
669 * horrendously expensive. We just want kmalloc to fail fast and fall back to
670 * vmalloc if it can't get something straight away from the free lists or
671 * buddy allocator. Hence we have to open code kvmalloc outselves here.
672 *
673 * This assumes that the caller uses memalloc_nofs_save task context here, so
674 * despite the use of GFP_KERNEL here, we are going to be doing GFP_NOFS
675 * allocations. This is actually the only way to make vmalloc() do GFP_NOFS
676 * allocations, so lets just all pretend this is a GFP_KERNEL context
677 * operation....
678 */
679static inline void *
680xlog_kvmalloc(
681 size_t buf_size)
682{
683 gfp_t flags = GFP_KERNEL;
684 void *p;
685
686 flags &= ~__GFP_DIRECT_RECLAIM;
687 flags |= __GFP_NOWARN | __GFP_NORETRY;
688 do {
689 p = kmalloc(buf_size, flags);
690 if (!p)
691 p = vmalloc(buf_size);
692 } while (!p);
693
694 return p;
695}
696
697/*
698 * Given a count of iovecs and space for a log item, compute the space we need
699 * in the log to store that data plus the log headers.
700 */
701static inline unsigned int
702xlog_item_space(
703 unsigned int niovecs,
704 unsigned int nbytes)
705{
706 nbytes += niovecs * (sizeof(uint64_t) + sizeof(struct xlog_op_header));
707 return round_up(nbytes, sizeof(uint64_t));
708}
709
710/*
711 * Cycles over XLOG_CYCLE_DATA_SIZE overflow into the extended header that was
712 * added for v2 logs. Addressing for the cycles array there is off by one,
713 * because the first batch of cycles is in the original header.
714 */
715static inline __be32 *xlog_cycle_data(struct xlog_rec_header *rhead, unsigned i)
716{
717 if (i >= XLOG_CYCLE_DATA_SIZE) {
718 unsigned j = i / XLOG_CYCLE_DATA_SIZE;
719 unsigned k = i % XLOG_CYCLE_DATA_SIZE;
720
721 return &rhead->h_ext[j - 1].xh_cycle_data[k];
722 }
723
724 return &rhead->h_cycle_data[i];
725}
726
727#endif /* __XFS_LOG_PRIV_H__ */
728

source code of linux/fs/xfs/xfs_log_priv.h