| /* |
| * Copyright (c) 2000-2003,2005 Silicon Graphics, Inc. |
| * All Rights Reserved. |
| * |
| * This program is free software; you can redistribute it and/or |
| * modify it under the terms of the GNU General Public License as |
| * published by the Free Software Foundation. |
| * |
| * This program is distributed in the hope that it would be useful, |
| * but WITHOUT ANY WARRANTY; without even the implied warranty of |
| * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| * GNU General Public License for more details. |
| * |
| * You should have received a copy of the GNU General Public License |
| * along with this program; if not, write the Free Software Foundation, |
| * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA |
| */ |
| #ifndef __XFS_LOG_PRIV_H__ |
| #define __XFS_LOG_PRIV_H__ |
| |
| struct xfs_buf; |
| struct xlog; |
| struct xlog_ticket; |
| struct xfs_mount; |
| struct xfs_log_callback; |
| |
| /* |
| * Flags for log structure |
| */ |
| #define XLOG_ACTIVE_RECOVERY 0x2 /* in the middle of recovery */ |
| #define XLOG_RECOVERY_NEEDED 0x4 /* log was recovered */ |
| #define XLOG_IO_ERROR 0x8 /* log hit an I/O error, and being |
| shutdown */ |
| #define XLOG_TAIL_WARN 0x10 /* log tail verify warning issued */ |
| |
| /* |
| * 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 |
| */ |
| #define XLOG_STATE_ACTIVE 0x0001 /* Current IC log being written to */ |
| #define XLOG_STATE_WANT_SYNC 0x0002 /* Want to sync this iclog; no more writes */ |
| #define XLOG_STATE_SYNCING 0x0004 /* This IC log is syncing */ |
| #define XLOG_STATE_DONE_SYNC 0x0008 /* Done syncing to disk */ |
| #define XLOG_STATE_DO_CALLBACK \ |
| 0x0010 /* Process callback functions */ |
| #define XLOG_STATE_CALLBACK 0x0020 /* Callback functions now */ |
| #define XLOG_STATE_DIRTY 0x0040 /* Dirty IC log, not ready for ACTIVE status*/ |
| #define XLOG_STATE_IOERROR 0x0080 /* IO error happened in sync'ing log */ |
| #define XLOG_STATE_IOABORT 0x0100 /* force abort on I/O completion (debug) */ |
| #define XLOG_STATE_ALL 0x7FFF /* All possible valid flags */ |
| #define XLOG_STATE_NOTUSED 0x8000 /* This IC log not being used */ |
| |
| /* |
| * Flags to log ticket |
| */ |
| #define XLOG_TIC_INITED 0x1 /* has been initialized */ |
| #define XLOG_TIC_PERM_RESERV 0x2 /* permanent reservation */ |
| |
| #define XLOG_TIC_FLAGS \ |
| { XLOG_TIC_INITED, "XLOG_TIC_INITED" }, \ |
| { 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 |
| |
| /* Ticket reservation region accounting */ |
| #define XLOG_TIC_LEN_MAX 15 |
| |
| /* |
| * Reservation region |
| * As would be stored in xfs_log_iovec but without the i_addr which |
| * we don't care about. |
| */ |
| typedef struct xlog_res { |
| uint r_len; /* region length :4 */ |
| uint r_type; /* region's transaction type :4 */ |
| } xlog_res_t; |
| |
| 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 : 4 */ |
| atomic_t t_ref; /* ticket reference count : 4 */ |
| int t_curr_res; /* current reservation in bytes : 4 */ |
| int t_unit_res; /* unit reservation in bytes : 4 */ |
| char t_ocnt; /* original count : 1 */ |
| char t_cnt; /* current count : 1 */ |
| char t_clientid; /* who does this belong to; : 1 */ |
| char t_flags; /* properties of reservation : 1 */ |
| |
| /* reservation array fields */ |
| uint t_res_num; /* num in array : 4 */ |
| uint t_res_num_ophdrs; /* num op hdrs : 4 */ |
| uint t_res_arr_sum; /* array sum : 4 */ |
| uint t_res_o_flow; /* sum overflow : 4 */ |
| xlog_res_t t_res_arr[XLOG_TIC_LEN_MAX]; /* array of res : 8 * 15 */ |
| } 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_bp is a pointer to the buffer used to write this incore log to disk. |
| * - ic_log is a pointer back to the global log structure. |
| * - ic_callback is a linked list of callback function/argument pairs to be |
| * called after an iclog finishes writing. |
| * - ic_size is the full size of the header plus data. |
| * - 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_callback_* |
| * - 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 xfs_buf *ic_bp; |
| struct xlog *ic_log; |
| int ic_size; |
| int ic_offset; |
| int ic_bwritecnt; |
| unsigned short ic_state; |
| char *ic_datap; /* pointer to iclog data */ |
| |
| /* Callback structures need their own cacheline */ |
| spinlock_t ic_callback_lock ____cacheline_aligned_in_smp; |
| struct xfs_log_callback *ic_callback; |
| struct xfs_log_callback **ic_callback_tail; |
| |
| /* 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 |
| } 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_lsn_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_ticket *ticket; /* chkpt ticket */ |
| int nvecs; /* number of regions */ |
| int space_used; /* aggregate size of regions */ |
| struct list_head busy_extents; /* busy extents in chkpt */ |
| struct xfs_log_vec *lv_chain; /* logvecs being pushed */ |
| struct xfs_log_callback log_cb; /* completion callback hook. */ |
| struct list_head committing; /* ctx committing list */ |
| }; |
| |
| /* |
| * 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; |
| struct list_head xc_cil; |
| spinlock_t xc_cil_lock; |
| |
| 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_lsn_t xc_push_seq; |
| struct list_head xc_committing; |
| wait_queue_head_t xc_commit_wait; |
| xfs_lsn_t xc_current_sequence; |
| struct work_struct xc_push_work; |
| } ____cacheline_aligned_in_smp; |
| |
| /* |
| * 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 will set a lower |
| * threshold at which background pushing is attempted without blocking current |
| * transaction commits. A separate, higher bound defines when CIL pushes are |
| * enforced to ensure we stay within our maximum checkpoint size bounds. |
| * threshold, yet give us plenty of space for aggregation on large logs. |
| */ |
| #define XLOG_CIL_SPACE_LIMIT(log) (log->l_logsize >> 3) |
| |
| /* |
| * 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_buf *l_xbuf; /* extra buffer for log |
| * wrapping */ |
| struct xfs_buftarg *l_targ; /* buftarg of log */ |
| struct delayed_work l_work; /* background flush work */ |
| uint l_flags; |
| uint l_quotaoffs_flag; /* XFS_DQ_*, for QUOTAOFFs */ |
| struct list_head *l_buf_cancel_table; |
| 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_size_log; /* log power size of log */ |
| 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_last_sync_lsn and l_tail_lsn are atomics so they can be set and |
| * read without needing to hold specific locks. To avoid operations |
| * contending with other hot objects, place each of them on a separate |
| * cacheline. |
| */ |
| /* lsn of last LR on disk */ |
| atomic64_t l_last_sync_lsn ____cacheline_aligned_in_smp; |
| /* 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; |
| |
| struct xfs_kobj l_kobj; |
| |
| /* The following field are used for debugging; need to hold icloglock */ |
| #ifdef DEBUG |
| void *l_iclog_bak[XLOG_MAX_ICLOGS]; |
| /* log record crc error injection factor */ |
| uint32_t l_badcrc_factor; |
| #endif |
| /* log recovery lsn tracking (for buffer submission */ |
| xfs_lsn_t l_recovery_lsn; |
| }; |
| |
| #define XLOG_BUF_CANCEL_BUCKET(log, blkno) \ |
| ((log)->l_buf_cancel_table + ((__uint64_t)blkno % XLOG_BC_TABLE_SIZE)) |
| |
| #define XLOG_FORCED_SHUTDOWN(log) ((log)->l_flags & XLOG_IO_ERROR) |
| |
| /* common routines */ |
| extern int |
| xlog_recover( |
| struct xlog *log); |
| extern int |
| xlog_recover_finish( |
| struct xlog *log); |
| extern int |
| xlog_recover_cancel(struct xlog *); |
| |
| extern __le32 xlog_cksum(struct xlog *log, struct xlog_rec_header *rhead, |
| char *dp, int size); |
| |
| extern kmem_zone_t *xfs_log_ticket_zone; |
| struct xlog_ticket * |
| xlog_ticket_alloc( |
| struct xlog *log, |
| int unit_bytes, |
| int count, |
| char client, |
| bool permanent, |
| xfs_km_flags_t alloc_flags); |
| |
| |
| static inline void |
| xlog_write_adv_cnt(void **ptr, int *len, int *off, size_t bytes) |
| { |
| *ptr += bytes; |
| *len -= bytes; |
| *off += bytes; |
| } |
| |
| void xlog_print_tic_res(struct xfs_mount *mp, struct xlog_ticket *ticket); |
| int |
| xlog_write( |
| struct xlog *log, |
| struct xfs_log_vec *log_vector, |
| struct xlog_ticket *tic, |
| xfs_lsn_t *start_lsn, |
| struct xlog_in_core **commit_iclog, |
| uint flags); |
| |
| /* |
| * 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)); |
| } |
| |
| /* |
| * When we crack the grant head, 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. |
| */ |
| static inline void |
| xlog_crack_grant_head_val(int64_t val, int *cycle, int *space) |
| { |
| *cycle = val >> 32; |
| *space = val & 0xffffffff; |
| } |
| |
| static inline void |
| xlog_crack_grant_head(atomic64_t *head, int *cycle, int *space) |
| { |
| xlog_crack_grant_head_val(atomic64_read(head), cycle, space); |
| } |
| |
| static inline int64_t |
| xlog_assign_grant_head_val(int cycle, int space) |
| { |
| return ((int64_t)cycle << 32) | space; |
| } |
| |
| static inline void |
| xlog_assign_grant_head(atomic64_t *head, int cycle, int space) |
| { |
| atomic64_set(head, xlog_assign_grant_head_val(cycle, space)); |
| } |
| |
| /* |
| * 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); |
| |
| /* |
| * CIL force routines |
| */ |
| xfs_lsn_t |
| xlog_cil_force_lsn( |
| struct xlog *log, |
| xfs_lsn_t sequence); |
| |
| static inline void |
| xlog_cil_force(struct xlog *log) |
| { |
| xlog_cil_force_lsn(log, log->l_cilp->xc_current_sequence); |
| } |
| |
| /* |
| * Unmount record type is used as a pseudo transaction type for the ticket. |
| * It's value must be outside the range of XFS_TRANS_* values. |
| */ |
| #define XLOG_UNMOUNT_REC_TYPE (-1U) |
| |
| /* |
| * 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(wait_queue_head_t *wq, spinlock_t *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); |
| } |
| |
| /* |
| * 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 = ACCESS_ONCE(log->l_curr_cycle); |
| smp_rmb(); |
| cur_block = ACCESS_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; |
| } |
| |
| #endif /* __XFS_LOG_PRIV_H__ */ |