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1// SPDX-License-Identifier: GPL-2.02/*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 bytes20 * of xlog_op_header containing the fields oh_clientid, oh_flags21 * and oh_res2 into the packed copy.22 *23 * later on this four byte chunk is treated as an int and the24 * 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 state35 */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 flags55 */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 flags66 */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-disk75 * log write such that no allocation transactions will be re-done during76 * recovery after a system crash. Recovery starts at the last on-disk77 * log write.78 *79 * These states are used to insert dummy log entries to cover80 * space allocation transactions which can undo non-transactional changes81 * after a crash. Writes to a file with space82 * already allocated do not result in any transactions. Allocations83 * might include space beyond the EOF. So if we just push the EOF a84 * little, the last transaction for the file could contain the wrong85 * size. If there is no file system activity, after an allocation86 * transaction, and the system crashes, the allocation transaction87 * will get replayed and the file will be truncated. This could88 * be hours/days/... after the allocation occurred.89 *90 * The fix for this is to do two dummy transactions when the91 * system is idle. We need two dummy transaction because the h_tail_lsn92 * in the log record header needs to point beyond the last possible93 * non-dummy transaction. The first dummy changes the h_tail_lsn to94 * the first transaction before the dummy. The second dummy causes95 * h_tail_lsn to point to the first dummy. Recovery starts at h_tail_lsn.96 *97 * These dummy transactions get committed when everything98 * 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 or103 * we are done covering previous transactions.104 * NEED -- logging has occurred and we need a dummy transaction105 * when the log becomes idle.106 * DONE -- we were in the NEED state and have committed a dummy107 * transaction.108 * NEED2 -- we detected that a dummy transaction has gone to the109 * 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 dummy121 * transaction going out, the next state is NEED.122 * So, if we aren't in the DONE or DONE2 states, the next state123 * is NEED. We can't be finishing a write of the dummy record124 * 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 the127 * dummy transaction, we move to NEED2.128 *129 * If we are in the DONE2 state and this was a write of the130 * dummy transaction, we move to IDLE.131 *132 *133 * Writing only one dummy transaction can get appended to134 * one file space allocation. When this happens, the log recovery135 * 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 0140#define XLOG_STATE_COVER_NEED 1141#define XLOG_STATE_COVER_DONE 2142#define XLOG_STATE_COVER_NEED2 3143#define XLOG_STATE_COVER_DONE2 4144 145#define XLOG_COVER_OPS 5146 147typedef struct 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} xlog_ticket_t;159 160/*161 * - A log record header is 512 bytes. There is plenty of room to grow the162 * xlog_rec_header_t into the reserved space.163 * - ic_data follows, so a write to disk can start at the beginning of164 * the iclog.165 * - ic_forcewait is used to implement synchronous forcing of the iclog to disk.166 * - ic_next is the pointer to the next iclog in the ring.167 * - ic_log is a pointer back to the global log structure.168 * - ic_size is the full size of the log buffer, minus the cycle headers.169 * - ic_offset is the current number of bytes written to in this iclog.170 * - ic_refcnt is bumped when someone is writing to the log.171 * - ic_state is the state of the iclog.172 *173 * Because of cacheline contention on large machines, we need to separate174 * various resources onto different cachelines. To start with, make the175 * structure cacheline aligned. The following fields can be contended on176 * by independent processes:177 *178 * - ic_callbacks179 * - ic_refcnt180 * - fields protected by the global l_icloglock181 *182 * so we need to ensure that these fields are located in separate cachelines.183 * We'll put all the read-only and l_icloglock fields in the first cacheline,184 * and move everything else out to subsequent cachelines.185 */186typedef struct xlog_in_core {187 wait_queue_head_t ic_force_wait;188 wait_queue_head_t ic_write_wait;189 struct xlog_in_core *ic_next;190 struct xlog_in_core *ic_prev;191 struct xlog *ic_log;192 u32 ic_size;193 u32 ic_offset;194 enum xlog_iclog_state ic_state;195 unsigned int ic_flags;196 void *ic_datap; /* pointer to iclog data */197 struct list_head ic_callbacks;198 199 /* reference counts need their own cacheline */200 atomic_t ic_refcnt ____cacheline_aligned_in_smp;201 xlog_in_core_2_t *ic_data;202#define ic_header ic_data->hic_header203#ifdef DEBUG204 bool ic_fail_crc : 1;205#endif206 struct semaphore ic_sema;207 struct work_struct ic_end_io_work;208 struct bio ic_bio;209 struct bio_vec ic_bvec[];210} xlog_in_core_t;211 212/*213 * The CIL context is used to aggregate per-transaction details as well be214 * passed to the iclog for checkpoint post-commit processing. After being215 * passed to the iclog, another context needs to be allocated for tracking the216 * next set of transactions to be aggregated into a checkpoint.217 */218struct xfs_cil;219 220struct xfs_cil_ctx {221 struct xfs_cil *cil;222 xfs_csn_t sequence; /* chkpt sequence # */223 xfs_lsn_t start_lsn; /* first LSN of chkpt commit */224 xfs_lsn_t commit_lsn; /* chkpt commit record lsn */225 struct xlog_in_core *commit_iclog;226 struct xlog_ticket *ticket; /* chkpt ticket */227 atomic_t space_used; /* aggregate size of regions */228 struct xfs_busy_extents busy_extents;229 struct list_head log_items; /* log items in chkpt */230 struct list_head lv_chain; /* logvecs being pushed */231 struct list_head iclog_entry;232 struct list_head committing; /* ctx committing list */233 struct work_struct push_work;234 atomic_t order_id;235 236 /*237 * CPUs that could have added items to the percpu CIL data. Access is238 * coordinated with xc_ctx_lock.239 */240 struct cpumask cil_pcpmask;241};242 243/*244 * Per-cpu CIL tracking items245 */246struct xlog_cil_pcp {247 int32_t space_used;248 uint32_t space_reserved;249 struct list_head busy_extents;250 struct list_head log_items;251};252 253/*254 * Committed Item List structure255 *256 * This structure is used to track log items that have been committed but not257 * yet written into the log. It is used only when the delayed logging mount258 * option is enabled.259 *260 * This structure tracks the list of committing checkpoint contexts so261 * we can avoid the problem of having to hold out new transactions during a262 * flush until we have a the commit record LSN of the checkpoint. We can263 * traverse the list of committing contexts in xlog_cil_push_lsn() to find a264 * sequence match and extract the commit LSN directly from there. If the265 * checkpoint is still in the process of committing, we can block waiting for266 * the commit LSN to be determined as well. This should make synchronous267 * operations almost as efficient as the old logging methods.268 */269struct xfs_cil {270 struct xlog *xc_log;271 unsigned long xc_flags;272 atomic_t xc_iclog_hdrs;273 struct workqueue_struct *xc_push_wq;274 275 struct rw_semaphore xc_ctx_lock ____cacheline_aligned_in_smp;276 struct xfs_cil_ctx *xc_ctx;277 278 spinlock_t xc_push_lock ____cacheline_aligned_in_smp;279 xfs_csn_t xc_push_seq;280 bool xc_push_commit_stable;281 struct list_head xc_committing;282 wait_queue_head_t xc_commit_wait;283 wait_queue_head_t xc_start_wait;284 xfs_csn_t xc_current_sequence;285 wait_queue_head_t xc_push_wait; /* background push throttle */286 287 void __percpu *xc_pcp; /* percpu CIL structures */288} ____cacheline_aligned_in_smp;289 290/* xc_flags bit values */291#define XLOG_CIL_EMPTY 1292#define XLOG_CIL_PCP_SPACE 2293 294/*295 * The amount of log space we allow the CIL to aggregate is difficult to size.296 * Whatever we choose, we have to make sure we can get a reservation for the297 * log space effectively, that it is large enough to capture sufficient298 * relogging to reduce log buffer IO significantly, but it is not too large for299 * the log or induces too much latency when writing out through the iclogs. We300 * track both space consumed and the number of vectors in the checkpoint301 * context, so we need to decide which to use for limiting.302 *303 * Every log buffer we write out during a push needs a header reserved, which304 * is at least one sector and more for v2 logs. Hence we need a reservation of305 * at least 512 bytes per 32k of log space just for the LR headers. That means306 * 16KB of reservation per megabyte of delayed logging space we will consume,307 * plus various headers. The number of headers will vary based on the num of308 * io vectors, so limiting on a specific number of vectors is going to result309 * in transactions of varying size. IOWs, it is more consistent to track and310 * limit space consumed in the log rather than by the number of objects being311 * logged in order to prevent checkpoint ticket overruns.312 *313 * Further, use of static reservations through the log grant mechanism is314 * problematic. It introduces a lot of complexity (e.g. reserve grant vs write315 * grant) and a significant deadlock potential because regranting write space316 * can block on log pushes. Hence if we have to regrant log space during a log317 * push, we can deadlock.318 *319 * However, we can avoid this by use of a dynamic "reservation stealing"320 * technique during transaction commit whereby unused reservation space in the321 * transaction ticket is transferred to the CIL ctx commit ticket to cover the322 * space needed by the checkpoint transaction. This means that we never need to323 * specifically reserve space for the CIL checkpoint transaction, nor do we324 * need to regrant space once the checkpoint completes. This also means the325 * checkpoint transaction ticket is specific to the checkpoint context, rather326 * than the CIL itself.327 *328 * With dynamic reservations, we can effectively make up arbitrary limits for329 * the checkpoint size so long as they don't violate any other size rules.330 * Recovery imposes a rule that no transaction exceed half the log, so we are331 * limited by that. Furthermore, the log transaction reservation subsystem332 * tries to keep 25% of the log free, so we need to keep below that limit or we333 * risk running out of free log space to start any new transactions.334 *335 * In order to keep background CIL push efficient, we only need to ensure the336 * CIL is large enough to maintain sufficient in-memory relogging to avoid337 * repeated physical writes of frequently modified metadata. If we allow the CIL338 * to grow to a substantial fraction of the log, then we may be pinning hundreds339 * of megabytes of metadata in memory until the CIL flushes. This can cause340 * issues when we are running low on memory - pinned memory cannot be reclaimed,341 * and the CIL consumes a lot of memory. Hence we need to set an upper physical342 * size limit for the CIL that limits the maximum amount of memory pinned by the343 * CIL but does not limit performance by reducing relogging efficiency344 * significantly.345 *346 * As such, the CIL push threshold ends up being the smaller of two thresholds:347 * - a threshold large enough that it allows CIL to be pushed and progress to be348 * made without excessive blocking of incoming transaction commits. This is349 * defined to be 12.5% of the log space - half the 25% push threshold of the350 * AIL.351 * - small enough that it doesn't pin excessive amounts of memory but maintains352 * close to peak relogging efficiency. This is defined to be 16x the iclog353 * buffer window (32MB) as measurements have shown this to be roughly the354 * point of diminishing performance increases under highly concurrent355 * modification workloads.356 *357 * To prevent the CIL from overflowing upper commit size bounds, we introduce a358 * new threshold at which we block committing transactions until the background359 * CIL commit commences and switches to a new context. While this is not a hard360 * limit, it forces the process committing a transaction to the CIL to block and361 * yeild the CPU, giving the CIL push work a chance to be scheduled and start362 * work. This prevents a process running lots of transactions from overfilling363 * the CIL because it is not yielding the CPU. We set the blocking limit at364 * twice the background push space threshold so we keep in line with the AIL365 * push thresholds.366 *367 * Note: this is not a -hard- limit as blocking is applied after the transaction368 * is inserted into the CIL and the push has been triggered. It is largely a369 * throttling mechanism that allows the CIL push to be scheduled and run. A hard370 * limit will be difficult to implement without introducing global serialisation371 * in the CIL commit fast path, and it's not at all clear that we actually need372 * such hard limits given the ~7 years we've run without a hard limit before373 * finding the first situation where a checkpoint size overflow actually374 * occurred. Hence the simple throttle, and an ASSERT check to tell us that375 * we've overrun the max size.376 */377#define XLOG_CIL_SPACE_LIMIT(log) \378 min_t(int, (log)->l_logsize >> 3, BBTOB(XLOG_TOTAL_REC_SHIFT(log)) << 4)379 380#define XLOG_CIL_BLOCKING_SPACE_LIMIT(log) \381 (XLOG_CIL_SPACE_LIMIT(log) * 2)382 383/*384 * ticket grant locks, queues and accounting have their own cachlines385 * as these are quite hot and can be operated on concurrently.386 */387struct xlog_grant_head {388 spinlock_t lock ____cacheline_aligned_in_smp;389 struct list_head waiters;390 atomic64_t grant;391};392 393/*394 * The reservation head lsn is not made up of a cycle number and block number.395 * Instead, it uses a cycle number and byte number. Logs don't expect to396 * overflow 31 bits worth of byte offset, so using a byte number will mean397 * that round off problems won't occur when releasing partial reservations.398 */399struct xlog {400 /* The following fields don't need locking */401 struct xfs_mount *l_mp; /* mount point */402 struct xfs_ail *l_ailp; /* AIL log is working with */403 struct xfs_cil *l_cilp; /* CIL log is working with */404 struct xfs_buftarg *l_targ; /* buftarg of log */405 struct workqueue_struct *l_ioend_workqueue; /* for I/O completions */406 struct delayed_work l_work; /* background flush work */407 long l_opstate; /* operational state */408 uint l_quotaoffs_flag; /* XFS_DQ_*, for QUOTAOFFs */409 struct list_head *l_buf_cancel_table;410 struct list_head r_dfops; /* recovered log intent items */411 int l_iclog_hsize; /* size of iclog header */412 int l_iclog_heads; /* # of iclog header sectors */413 uint l_sectBBsize; /* sector size in BBs (2^n) */414 int l_iclog_size; /* size of log in bytes */415 int l_iclog_bufs; /* number of iclog buffers */416 xfs_daddr_t l_logBBstart; /* start block of log */417 int l_logsize; /* size of log in bytes */418 int l_logBBsize; /* size of log in BB chunks */419 420 /* The following block of fields are changed while holding icloglock */421 wait_queue_head_t l_flush_wait ____cacheline_aligned_in_smp;422 /* waiting for iclog flush */423 int l_covered_state;/* state of "covering disk424 * log entries" */425 xlog_in_core_t *l_iclog; /* head log queue */426 spinlock_t l_icloglock; /* grab to change iclog state */427 int l_curr_cycle; /* Cycle number of log writes */428 int l_prev_cycle; /* Cycle number before last429 * block increment */430 int l_curr_block; /* current logical log block */431 int l_prev_block; /* previous logical log block */432 433 /*434 * l_tail_lsn is atomic so it can be set and read without needing to435 * hold specific locks. To avoid operations contending with other hot436 * objects, it on a separate cacheline.437 */438 /* lsn of 1st LR with unflushed * buffers */439 atomic64_t l_tail_lsn ____cacheline_aligned_in_smp;440 441 struct xlog_grant_head l_reserve_head;442 struct xlog_grant_head l_write_head;443 uint64_t l_tail_space;444 445 struct xfs_kobj l_kobj;446 447 /* log recovery lsn tracking (for buffer submission */448 xfs_lsn_t l_recovery_lsn;449 450 uint32_t l_iclog_roundoff;/* padding roundoff */451};452 453/*454 * Bits for operational state455 */456#define XLOG_ACTIVE_RECOVERY 0 /* in the middle of recovery */457#define XLOG_RECOVERY_NEEDED 1 /* log was recovered */458#define XLOG_IO_ERROR 2 /* log hit an I/O error, and being459 shutdown */460#define XLOG_TAIL_WARN 3 /* log tail verify warning issued */461 462static inline bool463xlog_recovery_needed(struct xlog *log)464{465 return test_bit(XLOG_RECOVERY_NEEDED, &log->l_opstate);466}467 468static inline bool469xlog_in_recovery(struct xlog *log)470{471 return test_bit(XLOG_ACTIVE_RECOVERY, &log->l_opstate);472}473 474static inline bool475xlog_is_shutdown(struct xlog *log)476{477 return test_bit(XLOG_IO_ERROR, &log->l_opstate);478}479 480/*481 * Wait until the xlog_force_shutdown() has marked the log as shut down482 * so xlog_is_shutdown() will always return true.483 */484static inline void485xlog_shutdown_wait(486 struct xlog *log)487{488 wait_var_event(&log->l_opstate, xlog_is_shutdown(log));489}490 491/* common routines */492extern int493xlog_recover(494 struct xlog *log);495extern int496xlog_recover_finish(497 struct xlog *log);498extern void499xlog_recover_cancel(struct xlog *);500 501extern __le32 xlog_cksum(struct xlog *log, struct xlog_rec_header *rhead,502 char *dp, int size);503 504extern struct kmem_cache *xfs_log_ticket_cache;505struct xlog_ticket *xlog_ticket_alloc(struct xlog *log, int unit_bytes,506 int count, bool permanent);507 508void xlog_print_tic_res(struct xfs_mount *mp, struct xlog_ticket *ticket);509void xlog_print_trans(struct xfs_trans *);510int xlog_write(struct xlog *log, struct xfs_cil_ctx *ctx,511 struct list_head *lv_chain, struct xlog_ticket *tic,512 uint32_t len);513void xfs_log_ticket_ungrant(struct xlog *log, struct xlog_ticket *ticket);514void xfs_log_ticket_regrant(struct xlog *log, struct xlog_ticket *ticket);515 516void xlog_state_switch_iclogs(struct xlog *log, struct xlog_in_core *iclog,517 int eventual_size);518int xlog_state_release_iclog(struct xlog *log, struct xlog_in_core *iclog,519 struct xlog_ticket *ticket);520 521/*522 * When we crack an atomic LSN, we sample it first so that the value will not523 * change while we are cracking it into the component values. This means we524 * will always get consistent component values to work from. This should always525 * be used to sample and crack LSNs that are stored and updated in atomic526 * variables.527 */528static inline void529xlog_crack_atomic_lsn(atomic64_t *lsn, uint *cycle, uint *block)530{531 xfs_lsn_t val = atomic64_read(lsn);532 533 *cycle = CYCLE_LSN(val);534 *block = BLOCK_LSN(val);535}536 537/*538 * Calculate and assign a value to an atomic LSN variable from component pieces.539 */540static inline void541xlog_assign_atomic_lsn(atomic64_t *lsn, uint cycle, uint block)542{543 atomic64_set(lsn, xlog_assign_lsn(cycle, block));544}545 546/*547 * Committed Item List interfaces548 */549int xlog_cil_init(struct xlog *log);550void xlog_cil_init_post_recovery(struct xlog *log);551void xlog_cil_destroy(struct xlog *log);552bool xlog_cil_empty(struct xlog *log);553void xlog_cil_commit(struct xlog *log, struct xfs_trans *tp,554 xfs_csn_t *commit_seq, bool regrant);555void xlog_cil_set_ctx_write_state(struct xfs_cil_ctx *ctx,556 struct xlog_in_core *iclog);557 558 559/*560 * CIL force routines561 */562void xlog_cil_flush(struct xlog *log);563xfs_lsn_t xlog_cil_force_seq(struct xlog *log, xfs_csn_t sequence);564 565static inline void566xlog_cil_force(struct xlog *log)567{568 xlog_cil_force_seq(log, log->l_cilp->xc_current_sequence);569}570 571/*572 * Wrapper function for waiting on a wait queue serialised against wakeups573 * by a spinlock. This matches the semantics of all the wait queues used in the574 * log code.575 */576static inline void577xlog_wait(578 struct wait_queue_head *wq,579 struct spinlock *lock)580 __releases(lock)581{582 DECLARE_WAITQUEUE(wait, current);583 584 add_wait_queue_exclusive(wq, &wait);585 __set_current_state(TASK_UNINTERRUPTIBLE);586 spin_unlock(lock);587 schedule();588 remove_wait_queue(wq, &wait);589}590 591int xlog_wait_on_iclog(struct xlog_in_core *iclog)592 __releases(iclog->ic_log->l_icloglock);593 594/* Calculate the distance between two LSNs in bytes */595static inline uint64_t596xlog_lsn_sub(597 struct xlog *log,598 xfs_lsn_t high,599 xfs_lsn_t low)600{601 uint32_t hi_cycle = CYCLE_LSN(high);602 uint32_t hi_block = BLOCK_LSN(high);603 uint32_t lo_cycle = CYCLE_LSN(low);604 uint32_t lo_block = BLOCK_LSN(low);605 606 if (hi_cycle == lo_cycle)607 return BBTOB(hi_block - lo_block);608 ASSERT((hi_cycle == lo_cycle + 1) || xlog_is_shutdown(log));609 return (uint64_t)log->l_logsize - BBTOB(lo_block - hi_block);610}611 612void xlog_grant_return_space(struct xlog *log, xfs_lsn_t old_head,613 xfs_lsn_t new_head);614 615/*616 * The LSN is valid so long as it is behind the current LSN. If it isn't, this617 * means that the next log record that includes this metadata could have a618 * smaller LSN. In turn, this means that the modification in the log would not619 * replay.620 */621static inline bool622xlog_valid_lsn(623 struct xlog *log,624 xfs_lsn_t lsn)625{626 int cur_cycle;627 int cur_block;628 bool valid = true;629 630 /*631 * First, sample the current lsn without locking to avoid added632 * contention from metadata I/O. The current cycle and block are updated633 * (in xlog_state_switch_iclogs()) and read here in a particular order634 * to avoid false negatives (e.g., thinking the metadata LSN is valid635 * when it is not).636 *637 * The current block is always rewound before the cycle is bumped in638 * xlog_state_switch_iclogs() to ensure the current LSN is never seen in639 * a transiently forward state. Instead, we can see the LSN in a640 * transiently behind state if we happen to race with a cycle wrap.641 */642 cur_cycle = READ_ONCE(log->l_curr_cycle);643 smp_rmb();644 cur_block = READ_ONCE(log->l_curr_block);645 646 if ((CYCLE_LSN(lsn) > cur_cycle) ||647 (CYCLE_LSN(lsn) == cur_cycle && BLOCK_LSN(lsn) > cur_block)) {648 /*649 * If the metadata LSN appears invalid, it's possible the check650 * above raced with a wrap to the next log cycle. Grab the lock651 * to check for sure.652 */653 spin_lock(&log->l_icloglock);654 cur_cycle = log->l_curr_cycle;655 cur_block = log->l_curr_block;656 spin_unlock(&log->l_icloglock);657 658 if ((CYCLE_LSN(lsn) > cur_cycle) ||659 (CYCLE_LSN(lsn) == cur_cycle && BLOCK_LSN(lsn) > cur_block))660 valid = false;661 }662 663 return valid;664}665 666/*667 * Log vector and shadow buffers can be large, so we need to use kvmalloc() here668 * to ensure success. Unfortunately, kvmalloc() only allows GFP_KERNEL contexts669 * to fall back to vmalloc, so we can't actually do anything useful with gfp670 * flags to control the kmalloc() behaviour within kvmalloc(). Hence kmalloc()671 * will do direct reclaim and compaction in the slow path, both of which are672 * horrendously expensive. We just want kmalloc to fail fast and fall back to673 * vmalloc if it can't get something straight away from the free lists or674 * buddy allocator. Hence we have to open code kvmalloc outselves here.675 *676 * This assumes that the caller uses memalloc_nofs_save task context here, so677 * despite the use of GFP_KERNEL here, we are going to be doing GFP_NOFS678 * allocations. This is actually the only way to make vmalloc() do GFP_NOFS679 * allocations, so lets just all pretend this is a GFP_KERNEL context680 * operation....681 */682static inline void *683xlog_kvmalloc(684 size_t buf_size)685{686 gfp_t flags = GFP_KERNEL;687 void *p;688 689 flags &= ~__GFP_DIRECT_RECLAIM;690 flags |= __GFP_NOWARN | __GFP_NORETRY;691 do {692 p = kmalloc(buf_size, flags);693 if (!p)694 p = vmalloc(buf_size);695 } while (!p);696 697 return p;698}699 700#endif /* __XFS_LOG_PRIV_H__ */701