cregit-Linux how code gets into the kernel

Release 4.11 fs/xfs/xfs_log_priv.h

Directory: fs/xfs
/*
 * 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; }

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Christoph Hellwig18100.00%3100.00%
Total18100.00%3100.00%

/* * 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 */ 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_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; }

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Christoph Hellwig38100.00%1100.00%
Total38100.00%1100.00%

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); }

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Dave Chinner43100.00%1100.00%
Total43100.00%1100.00%

/* * 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)); }

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Dave Chinner29100.00%1100.00%
Total29100.00%1100.00%

/* * 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; }

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Dave Chinner32100.00%2100.00%
Total32100.00%2100.00%


static inline void xlog_crack_grant_head(atomic64_t *head, int *cycle, int *space) { xlog_crack_grant_head_val(atomic64_read(head), cycle, space); }

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Dave Chinner31100.00%3100.00%
Total31100.00%3100.00%


static inline int64_t xlog_assign_grant_head_val(int cycle, int space) { return ((int64_t)cycle << 32) | space; }

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Dave Chinner25100.00%2100.00%
Total25100.00%2100.00%


static inline void xlog_assign_grant_head(atomic64_t *head, int cycle, int space) { atomic64_set(head, xlog_assign_grant_head_val(cycle, space)); }

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Dave Chinner29100.00%3100.00%
Total29100.00%3100.00%

/* * 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); }

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Dave Chinner2295.65%266.67%
Mark Tinguely14.35%133.33%
Total23100.00%3100.00%

/* * 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); }

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Dave Chinner51100.00%1100.00%
Total51100.00%1100.00%

/* * 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; }

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Brian Foster140100.00%1100.00%
Total140100.00%1100.00%

#endif /* __XFS_LOG_PRIV_H__ */

Overall Contributors

PersonTokensPropCommitsCommitProp
Dave Chinner54341.93%1727.87%
Christoph Hellwig37328.80%1422.95%
Brian Foster16712.90%58.20%
David Chinner997.64%711.48%
Timothy Shimmin634.86%46.56%
Mark Tinguely211.62%23.28%
Nathan Scott171.31%58.20%
Stephen Lord60.46%23.28%
Alex Elder20.15%23.28%
Matthew Wilcox20.15%11.64%
Lucas De Marchi10.08%11.64%
Al Viro10.08%11.64%
Total1295100.00%61100.00%
Directory: fs/xfs
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