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 struct xfs_buf; 10 struct xlog; 11 struct xlog_ticket; 12 struct xfs_mount; 13 14 /* 15 * Flags for log structure 16 */ 17 #define XLOG_ACTIVE_RECOVERY 0x2 /* in the middle of recovery */ 18 #define XLOG_RECOVERY_NEEDED 0x4 /* log was recovered */ 19 #define XLOG_IO_ERROR 0x8 /* log hit an I/O error, and being 20 shutdown */ 21 #define XLOG_TAIL_WARN 0x10 /* log tail verify warning issued */ 22 23 /* 24 * get client id from packed copy. 25 * 26 * this hack is here because the xlog_pack code copies four bytes 27 * of xlog_op_header containing the fields oh_clientid, oh_flags 28 * and oh_res2 into the packed copy. 29 * 30 * later on this four byte chunk is treated as an int and the 31 * client id is pulled out. 32 * 33 * this has endian issues, of course. 34 */ 35 static inline uint xlog_get_client_id(__be32 i) 36 { 37 return be32_to_cpu(i) >> 24; 38 } 39 40 /* 41 * In core log state 42 */ 43 enum xlog_iclog_state { 44 XLOG_STATE_ACTIVE, /* Current IC log being written to */ 45 XLOG_STATE_WANT_SYNC, /* Want to sync this iclog; no more writes */ 46 XLOG_STATE_SYNCING, /* This IC log is syncing */ 47 XLOG_STATE_DONE_SYNC, /* Done syncing to disk */ 48 XLOG_STATE_CALLBACK, /* Callback functions now */ 49 XLOG_STATE_DIRTY, /* Dirty IC log, not ready for ACTIVE status */ 50 XLOG_STATE_IOERROR, /* IO error happened in sync'ing log */ 51 }; 52 53 /* 54 * Log ticket flags 55 */ 56 #define XLOG_TIC_PERM_RESERV 0x1 /* permanent reservation */ 57 58 #define XLOG_TIC_FLAGS \ 59 { XLOG_TIC_PERM_RESERV, "XLOG_TIC_PERM_RESERV" } 60 61 /* 62 * Below are states for covering allocation transactions. 63 * By covering, we mean changing the h_tail_lsn in the last on-disk 64 * log write such that no allocation transactions will be re-done during 65 * recovery after a system crash. Recovery starts at the last on-disk 66 * log write. 67 * 68 * These states are used to insert dummy log entries to cover 69 * space allocation transactions which can undo non-transactional changes 70 * after a crash. Writes to a file with space 71 * already allocated do not result in any transactions. Allocations 72 * might include space beyond the EOF. So if we just push the EOF a 73 * little, the last transaction for the file could contain the wrong 74 * size. If there is no file system activity, after an allocation 75 * transaction, and the system crashes, the allocation transaction 76 * will get replayed and the file will be truncated. This could 77 * be hours/days/... after the allocation occurred. 78 * 79 * The fix for this is to do two dummy transactions when the 80 * system is idle. We need two dummy transaction because the h_tail_lsn 81 * in the log record header needs to point beyond the last possible 82 * non-dummy transaction. The first dummy changes the h_tail_lsn to 83 * the first transaction before the dummy. The second dummy causes 84 * h_tail_lsn to point to the first dummy. Recovery starts at h_tail_lsn. 85 * 86 * These dummy transactions get committed when everything 87 * is idle (after there has been some activity). 88 * 89 * There are 5 states used to control this. 90 * 91 * IDLE -- no logging has been done on the file system or 92 * we are done covering previous transactions. 93 * NEED -- logging has occurred and we need a dummy transaction 94 * when the log becomes idle. 95 * DONE -- we were in the NEED state and have committed a dummy 96 * transaction. 97 * NEED2 -- we detected that a dummy transaction has gone to the 98 * on disk log with no other transactions. 99 * DONE2 -- we committed a dummy transaction when in the NEED2 state. 100 * 101 * There are two places where we switch states: 102 * 103 * 1.) In xfs_sync, when we detect an idle log and are in NEED or NEED2. 104 * We commit the dummy transaction and switch to DONE or DONE2, 105 * respectively. In all other states, we don't do anything. 106 * 107 * 2.) When we finish writing the on-disk log (xlog_state_clean_log). 108 * 109 * No matter what state we are in, if this isn't the dummy 110 * transaction going out, the next state is NEED. 111 * So, if we aren't in the DONE or DONE2 states, the next state 112 * is NEED. We can't be finishing a write of the dummy record 113 * unless it was committed and the state switched to DONE or DONE2. 114 * 115 * If we are in the DONE state and this was a write of the 116 * dummy transaction, we move to NEED2. 117 * 118 * If we are in the DONE2 state and this was a write of the 119 * dummy transaction, we move to IDLE. 120 * 121 * 122 * Writing only one dummy transaction can get appended to 123 * one file space allocation. When this happens, the log recovery 124 * code replays the space allocation and a file could be truncated. 125 * This is why we have the NEED2 and DONE2 states before going idle. 126 */ 127 128 #define XLOG_STATE_COVER_IDLE 0 129 #define XLOG_STATE_COVER_NEED 1 130 #define XLOG_STATE_COVER_DONE 2 131 #define XLOG_STATE_COVER_NEED2 3 132 #define XLOG_STATE_COVER_DONE2 4 133 134 #define XLOG_COVER_OPS 5 135 136 /* Ticket reservation region accounting */ 137 #define XLOG_TIC_LEN_MAX 15 138 139 /* 140 * Reservation region 141 * As would be stored in xfs_log_iovec but without the i_addr which 142 * we don't care about. 143 */ 144 typedef struct xlog_res { 145 uint r_len; /* region length :4 */ 146 uint r_type; /* region's transaction type :4 */ 147 } xlog_res_t; 148 149 typedef struct xlog_ticket { 150 struct list_head t_queue; /* reserve/write queue */ 151 struct task_struct *t_task; /* task that owns this ticket */ 152 xlog_tid_t t_tid; /* transaction identifier : 4 */ 153 atomic_t t_ref; /* ticket reference count : 4 */ 154 int t_curr_res; /* current reservation in bytes : 4 */ 155 int t_unit_res; /* unit reservation in bytes : 4 */ 156 char t_ocnt; /* original count : 1 */ 157 char t_cnt; /* current count : 1 */ 158 char t_clientid; /* who does this belong to; : 1 */ 159 char t_flags; /* properties of reservation : 1 */ 160 161 /* reservation array fields */ 162 uint t_res_num; /* num in array : 4 */ 163 uint t_res_num_ophdrs; /* num op hdrs : 4 */ 164 uint t_res_arr_sum; /* array sum : 4 */ 165 uint t_res_o_flow; /* sum overflow : 4 */ 166 xlog_res_t t_res_arr[XLOG_TIC_LEN_MAX]; /* array of res : 8 * 15 */ 167 } xlog_ticket_t; 168 169 /* 170 * - A log record header is 512 bytes. There is plenty of room to grow the 171 * xlog_rec_header_t into the reserved space. 172 * - ic_data follows, so a write to disk can start at the beginning of 173 * the iclog. 174 * - ic_forcewait is used to implement synchronous forcing of the iclog to disk. 175 * - ic_next is the pointer to the next iclog in the ring. 176 * - ic_log is a pointer back to the global log structure. 177 * - ic_size is the full size of the log buffer, minus the cycle headers. 178 * - ic_offset is the current number of bytes written to in this iclog. 179 * - ic_refcnt is bumped when someone is writing to the log. 180 * - ic_state is the state of the iclog. 181 * 182 * Because of cacheline contention on large machines, we need to separate 183 * various resources onto different cachelines. To start with, make the 184 * structure cacheline aligned. The following fields can be contended on 185 * by independent processes: 186 * 187 * - ic_callbacks 188 * - ic_refcnt 189 * - fields protected by the global l_icloglock 190 * 191 * so we need to ensure that these fields are located in separate cachelines. 192 * We'll put all the read-only and l_icloglock fields in the first cacheline, 193 * and move everything else out to subsequent cachelines. 194 */ 195 typedef struct xlog_in_core { 196 wait_queue_head_t ic_force_wait; 197 wait_queue_head_t ic_write_wait; 198 struct xlog_in_core *ic_next; 199 struct xlog_in_core *ic_prev; 200 struct xlog *ic_log; 201 u32 ic_size; 202 u32 ic_offset; 203 enum xlog_iclog_state ic_state; 204 char *ic_datap; /* pointer to iclog data */ 205 206 /* Callback structures need their own cacheline */ 207 spinlock_t ic_callback_lock ____cacheline_aligned_in_smp; 208 struct list_head ic_callbacks; 209 210 /* reference counts need their own cacheline */ 211 atomic_t ic_refcnt ____cacheline_aligned_in_smp; 212 xlog_in_core_2_t *ic_data; 213 #define ic_header ic_data->hic_header 214 #ifdef DEBUG 215 bool ic_fail_crc : 1; 216 #endif 217 struct semaphore ic_sema; 218 struct work_struct ic_end_io_work; 219 struct bio ic_bio; 220 struct bio_vec ic_bvec[]; 221 } xlog_in_core_t; 222 223 /* 224 * The CIL context is used to aggregate per-transaction details as well be 225 * passed to the iclog for checkpoint post-commit processing. After being 226 * passed to the iclog, another context needs to be allocated for tracking the 227 * next set of transactions to be aggregated into a checkpoint. 228 */ 229 struct xfs_cil; 230 231 struct xfs_cil_ctx { 232 struct xfs_cil *cil; 233 xfs_lsn_t sequence; /* chkpt sequence # */ 234 xfs_lsn_t start_lsn; /* first LSN of chkpt commit */ 235 xfs_lsn_t commit_lsn; /* chkpt commit record lsn */ 236 struct xlog_ticket *ticket; /* chkpt ticket */ 237 int nvecs; /* number of regions */ 238 int space_used; /* aggregate size of regions */ 239 struct list_head busy_extents; /* busy extents in chkpt */ 240 struct xfs_log_vec *lv_chain; /* logvecs being pushed */ 241 struct list_head iclog_entry; 242 struct list_head committing; /* ctx committing list */ 243 struct work_struct discard_endio_work; 244 }; 245 246 /* 247 * Committed Item List structure 248 * 249 * This structure is used to track log items that have been committed but not 250 * yet written into the log. It is used only when the delayed logging mount 251 * option is enabled. 252 * 253 * This structure tracks the list of committing checkpoint contexts so 254 * we can avoid the problem of having to hold out new transactions during a 255 * flush until we have a the commit record LSN of the checkpoint. We can 256 * traverse the list of committing contexts in xlog_cil_push_lsn() to find a 257 * sequence match and extract the commit LSN directly from there. If the 258 * checkpoint is still in the process of committing, we can block waiting for 259 * the commit LSN to be determined as well. This should make synchronous 260 * operations almost as efficient as the old logging methods. 261 */ 262 struct xfs_cil { 263 struct xlog *xc_log; 264 struct list_head xc_cil; 265 spinlock_t xc_cil_lock; 266 267 struct rw_semaphore xc_ctx_lock ____cacheline_aligned_in_smp; 268 struct xfs_cil_ctx *xc_ctx; 269 270 spinlock_t xc_push_lock ____cacheline_aligned_in_smp; 271 xfs_lsn_t xc_push_seq; 272 struct list_head xc_committing; 273 wait_queue_head_t xc_commit_wait; 274 xfs_lsn_t xc_current_sequence; 275 struct work_struct xc_push_work; 276 wait_queue_head_t xc_push_wait; /* background push throttle */ 277 } ____cacheline_aligned_in_smp; 278 279 /* 280 * The amount of log space we allow the CIL to aggregate is difficult to size. 281 * Whatever we choose, we have to make sure we can get a reservation for the 282 * log space effectively, that it is large enough to capture sufficient 283 * relogging to reduce log buffer IO significantly, but it is not too large for 284 * the log or induces too much latency when writing out through the iclogs. We 285 * track both space consumed and the number of vectors in the checkpoint 286 * context, so we need to decide which to use for limiting. 287 * 288 * Every log buffer we write out during a push needs a header reserved, which 289 * is at least one sector and more for v2 logs. Hence we need a reservation of 290 * at least 512 bytes per 32k of log space just for the LR headers. That means 291 * 16KB of reservation per megabyte of delayed logging space we will consume, 292 * plus various headers. The number of headers will vary based on the num of 293 * io vectors, so limiting on a specific number of vectors is going to result 294 * in transactions of varying size. IOWs, it is more consistent to track and 295 * limit space consumed in the log rather than by the number of objects being 296 * logged in order to prevent checkpoint ticket overruns. 297 * 298 * Further, use of static reservations through the log grant mechanism is 299 * problematic. It introduces a lot of complexity (e.g. reserve grant vs write 300 * grant) and a significant deadlock potential because regranting write space 301 * can block on log pushes. Hence if we have to regrant log space during a log 302 * push, we can deadlock. 303 * 304 * However, we can avoid this by use of a dynamic "reservation stealing" 305 * technique during transaction commit whereby unused reservation space in the 306 * transaction ticket is transferred to the CIL ctx commit ticket to cover the 307 * space needed by the checkpoint transaction. This means that we never need to 308 * specifically reserve space for the CIL checkpoint transaction, nor do we 309 * need to regrant space once the checkpoint completes. This also means the 310 * checkpoint transaction ticket is specific to the checkpoint context, rather 311 * than the CIL itself. 312 * 313 * With dynamic reservations, we can effectively make up arbitrary limits for 314 * the checkpoint size so long as they don't violate any other size rules. 315 * Recovery imposes a rule that no transaction exceed half the log, so we are 316 * limited by that. Furthermore, the log transaction reservation subsystem 317 * tries to keep 25% of the log free, so we need to keep below that limit or we 318 * risk running out of free log space to start any new transactions. 319 * 320 * In order to keep background CIL push efficient, we only need to ensure the 321 * CIL is large enough to maintain sufficient in-memory relogging to avoid 322 * repeated physical writes of frequently modified metadata. If we allow the CIL 323 * to grow to a substantial fraction of the log, then we may be pinning hundreds 324 * of megabytes of metadata in memory until the CIL flushes. This can cause 325 * issues when we are running low on memory - pinned memory cannot be reclaimed, 326 * and the CIL consumes a lot of memory. Hence we need to set an upper physical 327 * size limit for the CIL that limits the maximum amount of memory pinned by the 328 * CIL but does not limit performance by reducing relogging efficiency 329 * significantly. 330 * 331 * As such, the CIL push threshold ends up being the smaller of two thresholds: 332 * - a threshold large enough that it allows CIL to be pushed and progress to be 333 * made without excessive blocking of incoming transaction commits. This is 334 * defined to be 12.5% of the log space - half the 25% push threshold of the 335 * AIL. 336 * - small enough that it doesn't pin excessive amounts of memory but maintains 337 * close to peak relogging efficiency. This is defined to be 16x the iclog 338 * buffer window (32MB) as measurements have shown this to be roughly the 339 * point of diminishing performance increases under highly concurrent 340 * modification workloads. 341 * 342 * To prevent the CIL from overflowing upper commit size bounds, we introduce a 343 * new threshold at which we block committing transactions until the background 344 * CIL commit commences and switches to a new context. While this is not a hard 345 * limit, it forces the process committing a transaction to the CIL to block and 346 * yeild the CPU, giving the CIL push work a chance to be scheduled and start 347 * work. This prevents a process running lots of transactions from overfilling 348 * the CIL because it is not yielding the CPU. We set the blocking limit at 349 * twice the background push space threshold so we keep in line with the AIL 350 * push thresholds. 351 * 352 * Note: this is not a -hard- limit as blocking is applied after the transaction 353 * is inserted into the CIL and the push has been triggered. It is largely a 354 * throttling mechanism that allows the CIL push to be scheduled and run. A hard 355 * limit will be difficult to implement without introducing global serialisation 356 * in the CIL commit fast path, and it's not at all clear that we actually need 357 * such hard limits given the ~7 years we've run without a hard limit before 358 * finding the first situation where a checkpoint size overflow actually 359 * occurred. Hence the simple throttle, and an ASSERT check to tell us that 360 * we've overrun the max size. 361 */ 362 #define XLOG_CIL_SPACE_LIMIT(log) \ 363 min_t(int, (log)->l_logsize >> 3, BBTOB(XLOG_TOTAL_REC_SHIFT(log)) << 4) 364 365 #define XLOG_CIL_BLOCKING_SPACE_LIMIT(log) \ 366 (XLOG_CIL_SPACE_LIMIT(log) * 2) 367 368 /* 369 * ticket grant locks, queues and accounting have their own cachlines 370 * as these are quite hot and can be operated on concurrently. 371 */ 372 struct xlog_grant_head { 373 spinlock_t lock ____cacheline_aligned_in_smp; 374 struct list_head waiters; 375 atomic64_t grant; 376 }; 377 378 /* 379 * The reservation head lsn is not made up of a cycle number and block number. 380 * Instead, it uses a cycle number and byte number. Logs don't expect to 381 * overflow 31 bits worth of byte offset, so using a byte number will mean 382 * that round off problems won't occur when releasing partial reservations. 383 */ 384 struct xlog { 385 /* The following fields don't need locking */ 386 struct xfs_mount *l_mp; /* mount point */ 387 struct xfs_ail *l_ailp; /* AIL log is working with */ 388 struct xfs_cil *l_cilp; /* CIL log is working with */ 389 struct xfs_buftarg *l_targ; /* buftarg of log */ 390 struct workqueue_struct *l_ioend_workqueue; /* for I/O completions */ 391 struct delayed_work l_work; /* background flush work */ 392 uint l_flags; 393 uint l_quotaoffs_flag; /* XFS_DQ_*, for QUOTAOFFs */ 394 struct list_head *l_buf_cancel_table; 395 int l_iclog_hsize; /* size of iclog header */ 396 int l_iclog_heads; /* # of iclog header sectors */ 397 uint l_sectBBsize; /* sector size in BBs (2^n) */ 398 int l_iclog_size; /* size of log in bytes */ 399 int l_iclog_bufs; /* number of iclog buffers */ 400 xfs_daddr_t l_logBBstart; /* start block of log */ 401 int l_logsize; /* size of log in bytes */ 402 int l_logBBsize; /* size of log in BB chunks */ 403 404 /* The following block of fields are changed while holding icloglock */ 405 wait_queue_head_t l_flush_wait ____cacheline_aligned_in_smp; 406 /* waiting for iclog flush */ 407 int l_covered_state;/* state of "covering disk 408 * log entries" */ 409 xlog_in_core_t *l_iclog; /* head log queue */ 410 spinlock_t l_icloglock; /* grab to change iclog state */ 411 int l_curr_cycle; /* Cycle number of log writes */ 412 int l_prev_cycle; /* Cycle number before last 413 * block increment */ 414 int l_curr_block; /* current logical log block */ 415 int l_prev_block; /* previous logical log block */ 416 417 /* 418 * l_last_sync_lsn and l_tail_lsn are atomics so they can be set and 419 * read without needing to hold specific locks. To avoid operations 420 * contending with other hot objects, place each of them on a separate 421 * cacheline. 422 */ 423 /* lsn of last LR on disk */ 424 atomic64_t l_last_sync_lsn ____cacheline_aligned_in_smp; 425 /* lsn of 1st LR with unflushed * buffers */ 426 atomic64_t l_tail_lsn ____cacheline_aligned_in_smp; 427 428 struct xlog_grant_head l_reserve_head; 429 struct xlog_grant_head l_write_head; 430 431 struct xfs_kobj l_kobj; 432 433 /* The following field are used for debugging; need to hold icloglock */ 434 #ifdef DEBUG 435 void *l_iclog_bak[XLOG_MAX_ICLOGS]; 436 #endif 437 /* log recovery lsn tracking (for buffer submission */ 438 xfs_lsn_t l_recovery_lsn; 439 }; 440 441 #define XLOG_BUF_CANCEL_BUCKET(log, blkno) \ 442 ((log)->l_buf_cancel_table + ((uint64_t)blkno % XLOG_BC_TABLE_SIZE)) 443 444 #define XLOG_FORCED_SHUTDOWN(log) \ 445 (unlikely((log)->l_flags & XLOG_IO_ERROR)) 446 447 /* common routines */ 448 extern int 449 xlog_recover( 450 struct xlog *log); 451 extern int 452 xlog_recover_finish( 453 struct xlog *log); 454 extern void 455 xlog_recover_cancel(struct xlog *); 456 457 extern __le32 xlog_cksum(struct xlog *log, struct xlog_rec_header *rhead, 458 char *dp, int size); 459 460 extern kmem_zone_t *xfs_log_ticket_zone; 461 struct xlog_ticket * 462 xlog_ticket_alloc( 463 struct xlog *log, 464 int unit_bytes, 465 int count, 466 char client, 467 bool permanent); 468 469 static inline void 470 xlog_write_adv_cnt(void **ptr, int *len, int *off, size_t bytes) 471 { 472 *ptr += bytes; 473 *len -= bytes; 474 *off += bytes; 475 } 476 477 void xlog_print_tic_res(struct xfs_mount *mp, struct xlog_ticket *ticket); 478 void xlog_print_trans(struct xfs_trans *); 479 int xlog_write(struct xlog *log, struct xfs_log_vec *log_vector, 480 struct xlog_ticket *tic, xfs_lsn_t *start_lsn, 481 struct xlog_in_core **commit_iclog, uint flags, 482 bool need_start_rec); 483 int xlog_commit_record(struct xlog *log, struct xlog_ticket *ticket, 484 struct xlog_in_core **iclog, xfs_lsn_t *lsn); 485 void xfs_log_ticket_ungrant(struct xlog *log, struct xlog_ticket *ticket); 486 void xfs_log_ticket_regrant(struct xlog *log, struct xlog_ticket *ticket); 487 488 /* 489 * When we crack an atomic LSN, we sample it first so that the value will not 490 * change while we are cracking it into the component values. This means we 491 * will always get consistent component values to work from. This should always 492 * be used to sample and crack LSNs that are stored and updated in atomic 493 * variables. 494 */ 495 static inline void 496 xlog_crack_atomic_lsn(atomic64_t *lsn, uint *cycle, uint *block) 497 { 498 xfs_lsn_t val = atomic64_read(lsn); 499 500 *cycle = CYCLE_LSN(val); 501 *block = BLOCK_LSN(val); 502 } 503 504 /* 505 * Calculate and assign a value to an atomic LSN variable from component pieces. 506 */ 507 static inline void 508 xlog_assign_atomic_lsn(atomic64_t *lsn, uint cycle, uint block) 509 { 510 atomic64_set(lsn, xlog_assign_lsn(cycle, block)); 511 } 512 513 /* 514 * When we crack the grant head, we sample it first so that the value will not 515 * change while we are cracking it into the component values. This means we 516 * will always get consistent component values to work from. 517 */ 518 static inline void 519 xlog_crack_grant_head_val(int64_t val, int *cycle, int *space) 520 { 521 *cycle = val >> 32; 522 *space = val & 0xffffffff; 523 } 524 525 static inline void 526 xlog_crack_grant_head(atomic64_t *head, int *cycle, int *space) 527 { 528 xlog_crack_grant_head_val(atomic64_read(head), cycle, space); 529 } 530 531 static inline int64_t 532 xlog_assign_grant_head_val(int cycle, int space) 533 { 534 return ((int64_t)cycle << 32) | space; 535 } 536 537 static inline void 538 xlog_assign_grant_head(atomic64_t *head, int cycle, int space) 539 { 540 atomic64_set(head, xlog_assign_grant_head_val(cycle, space)); 541 } 542 543 /* 544 * Committed Item List interfaces 545 */ 546 int xlog_cil_init(struct xlog *log); 547 void xlog_cil_init_post_recovery(struct xlog *log); 548 void xlog_cil_destroy(struct xlog *log); 549 bool xlog_cil_empty(struct xlog *log); 550 551 /* 552 * CIL force routines 553 */ 554 xfs_lsn_t 555 xlog_cil_force_lsn( 556 struct xlog *log, 557 xfs_lsn_t sequence); 558 559 static inline void 560 xlog_cil_force(struct xlog *log) 561 { 562 xlog_cil_force_lsn(log, log->l_cilp->xc_current_sequence); 563 } 564 565 /* 566 * Wrapper function for waiting on a wait queue serialised against wakeups 567 * by a spinlock. This matches the semantics of all the wait queues used in the 568 * log code. 569 */ 570 static inline void 571 xlog_wait( 572 struct wait_queue_head *wq, 573 struct spinlock *lock) 574 __releases(lock) 575 { 576 DECLARE_WAITQUEUE(wait, current); 577 578 add_wait_queue_exclusive(wq, &wait); 579 __set_current_state(TASK_UNINTERRUPTIBLE); 580 spin_unlock(lock); 581 schedule(); 582 remove_wait_queue(wq, &wait); 583 } 584 585 /* 586 * The LSN is valid so long as it is behind the current LSN. If it isn't, this 587 * means that the next log record that includes this metadata could have a 588 * smaller LSN. In turn, this means that the modification in the log would not 589 * replay. 590 */ 591 static inline bool 592 xlog_valid_lsn( 593 struct xlog *log, 594 xfs_lsn_t lsn) 595 { 596 int cur_cycle; 597 int cur_block; 598 bool valid = true; 599 600 /* 601 * First, sample the current lsn without locking to avoid added 602 * contention from metadata I/O. The current cycle and block are updated 603 * (in xlog_state_switch_iclogs()) and read here in a particular order 604 * to avoid false negatives (e.g., thinking the metadata LSN is valid 605 * when it is not). 606 * 607 * The current block is always rewound before the cycle is bumped in 608 * xlog_state_switch_iclogs() to ensure the current LSN is never seen in 609 * a transiently forward state. Instead, we can see the LSN in a 610 * transiently behind state if we happen to race with a cycle wrap. 611 */ 612 cur_cycle = READ_ONCE(log->l_curr_cycle); 613 smp_rmb(); 614 cur_block = READ_ONCE(log->l_curr_block); 615 616 if ((CYCLE_LSN(lsn) > cur_cycle) || 617 (CYCLE_LSN(lsn) == cur_cycle && BLOCK_LSN(lsn) > cur_block)) { 618 /* 619 * If the metadata LSN appears invalid, it's possible the check 620 * above raced with a wrap to the next log cycle. Grab the lock 621 * to check for sure. 622 */ 623 spin_lock(&log->l_icloglock); 624 cur_cycle = log->l_curr_cycle; 625 cur_block = log->l_curr_block; 626 spin_unlock(&log->l_icloglock); 627 628 if ((CYCLE_LSN(lsn) > cur_cycle) || 629 (CYCLE_LSN(lsn) == cur_cycle && BLOCK_LSN(lsn) > cur_block)) 630 valid = false; 631 } 632 633 return valid; 634 } 635 636 #endif /* __XFS_LOG_PRIV_H__ */ 637