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// SPDX-License-Identifier: GPL-2.0
* Copyright (c) 2000-2003,2005 Silicon Graphics, Inc.
* All Rights Reserved.
#ifndef __XFS_LOG_PRIV_H__
#define __XFS_LOG_PRIV_H__
struct xfs_buf;
struct xlog;
struct xlog_ticket;
struct xfs_mount;
* 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
enum xlog_iclog_state {
XLOG_STATE_ACTIVE, /* Current IC log being written to */
XLOG_STATE_WANT_SYNC, /* Want to sync this iclog; no more writes */
XLOG_STATE_SYNCING, /* This IC log is syncing */
XLOG_STATE_DONE_SYNC, /* Done syncing to disk */
XLOG_STATE_CALLBACK, /* Callback functions now */
XLOG_STATE_DIRTY, /* Dirty IC log, not ready for ACTIVE status */
XLOG_STATE_IOERROR, /* IO error happened in sync'ing log */
* Flags to log ticket
#define XLOG_TIC_INITED 0x1 /* has been initialized */
#define XLOG_TIC_PERM_RESERV 0x2 /* permanent reservation */
#define XLOG_TIC_FLAGS \
* 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_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_log is a pointer back to the global log structure.
* - ic_size is the full size of the log buffer, minus the cycle headers.
* - ic_offset is the current number of bytes written to in this iclog.
* - ic_refcnt is bumped when someone is writing to the log.
* - ic_state is the state of the iclog.
* Because of cacheline contention on large machines, we need to separate
* various resources onto different cachelines. To start with, make the
* structure cacheline aligned. The following fields can be contended on
* by independent processes:
* - ic_callbacks
* - ic_refcnt
* - fields protected by the global l_icloglock
* so we need to ensure that these fields are located in separate cachelines.
* We'll put all the read-only and l_icloglock fields in the first cacheline,
* and move everything else out to subsequent cachelines.
typedef struct xlog_in_core {
wait_queue_head_t ic_force_wait;
wait_queue_head_t ic_write_wait;
struct xlog_in_core *ic_next;
struct xlog_in_core *ic_prev;
struct xlog *ic_log;
u32 ic_size;
u32 ic_offset;
enum xlog_iclog_state ic_state;
char *ic_datap; /* pointer to iclog data */
/* Callback structures need their own cacheline */
spinlock_t ic_callback_lock ____cacheline_aligned_in_smp;
struct list_head ic_callbacks;
/* reference counts need their own cacheline */
atomic_t ic_refcnt ____cacheline_aligned_in_smp;
xlog_in_core_2_t *ic_data;
#define ic_header ic_data->hic_header
#ifdef DEBUG
bool ic_fail_crc : 1;
struct semaphore ic_sema;
struct work_struct ic_end_io_work;
struct bio ic_bio;
struct bio_vec ic_bvec[];
} xlog_in_core_t;
* The CIL context is used to aggregate per-transaction details as well be
* passed to the iclog for checkpoint post-commit processing. After being
* passed to the iclog, another context needs to be allocated for tracking the
* next set of transactions to be aggregated into a checkpoint.
struct xfs_cil;
struct xfs_cil_ctx {
struct xfs_cil *cil;
xfs_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 list_head iclog_entry;
struct list_head committing; /* ctx committing list */
struct work_struct discard_endio_work;
* 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_buftarg *l_targ; /* buftarg of log */
struct workqueue_struct *l_ioend_workqueue; /* for I/O completions */
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_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 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
struct xlog *log);
extern int
struct xlog *log);
extern void
xlog_recover_cancel(struct xlog *);
extern __le32 xlog_cksum(struct xlog *log, struct xlog_rec_header *rhead,
char *dp, int size);
extern kmem_zone_t *xfs_log_ticket_zone;
struct xlog_ticket *
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);
void xlog_print_trans(struct xfs_trans *);
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
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.
* 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
struct wait_queue_head *wq,
struct spinlock *lock)
DECLARE_WAITQUEUE(wait, current);
add_wait_queue_exclusive(wq, &wait);
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
struct xlog *log,
xfs_lsn_t lsn)
int cur_cycle;
int cur_block;
bool valid = true;
* First, sample the current lsn without locking to avoid added
* contention from metadata I/O. The current cycle and block are updated
* (in xlog_state_switch_iclogs()) and read here in a particular order
* to avoid false negatives (e.g., thinking the metadata LSN is valid
* when it is not).
* The current block is always rewound before the cycle is bumped in
* xlog_state_switch_iclogs() to ensure the current LSN is never seen in
* a transiently forward state. Instead, we can see the LSN in a
* transiently behind state if we happen to race with a cycle wrap.
cur_cycle = READ_ONCE(log->l_curr_cycle);
cur_block = READ_ONCE(log->l_curr_block);
if ((CYCLE_LSN(lsn) > cur_cycle) ||
(CYCLE_LSN(lsn) == cur_cycle && BLOCK_LSN(lsn) > cur_block)) {
* If the metadata LSN appears invalid, it's possible the check
* above raced with a wrap to the next log cycle. Grab the lock
* to check for sure.
cur_cycle = log->l_curr_cycle;
cur_block = log->l_curr_block;
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__ */