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authorDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-11 08:27:49 +0000
committerDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-11 08:27:49 +0000
commitace9429bb58fd418f0c81d4c2835699bddf6bde6 (patch)
treeb2d64bc10158fdd5497876388cd68142ca374ed3 /fs/xfs/xfs_log_priv.h
parentInitial commit. (diff)
downloadlinux-ace9429bb58fd418f0c81d4c2835699bddf6bde6.tar.xz
linux-ace9429bb58fd418f0c81d4c2835699bddf6bde6.zip
Adding upstream version 6.6.15.upstream/6.6.15
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'fs/xfs/xfs_log_priv.h')
-rw-r--r--fs/xfs/xfs_log_priv.h712
1 files changed, 712 insertions, 0 deletions
diff --git a/fs/xfs/xfs_log_priv.h b/fs/xfs/xfs_log_priv.h
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+++ b/fs/xfs/xfs_log_priv.h
@@ -0,0 +1,712 @@
+// 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__
+
+#include "xfs_extent_busy.h" /* for struct xfs_busy_extents */
+
+struct xfs_buf;
+struct xlog;
+struct xlog_ticket;
+struct xfs_mount;
+
+/*
+ * 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 */
+};
+
+#define XLOG_STATE_STRINGS \
+ { XLOG_STATE_ACTIVE, "XLOG_STATE_ACTIVE" }, \
+ { XLOG_STATE_WANT_SYNC, "XLOG_STATE_WANT_SYNC" }, \
+ { XLOG_STATE_SYNCING, "XLOG_STATE_SYNCING" }, \
+ { XLOG_STATE_DONE_SYNC, "XLOG_STATE_DONE_SYNC" }, \
+ { XLOG_STATE_CALLBACK, "XLOG_STATE_CALLBACK" }, \
+ { XLOG_STATE_DIRTY, "XLOG_STATE_DIRTY" }
+
+/*
+ * In core log flags
+ */
+#define XLOG_ICL_NEED_FLUSH (1u << 0) /* iclog needs REQ_PREFLUSH */
+#define XLOG_ICL_NEED_FUA (1u << 1) /* iclog needs REQ_FUA */
+
+#define XLOG_ICL_STRINGS \
+ { XLOG_ICL_NEED_FLUSH, "XLOG_ICL_NEED_FLUSH" }, \
+ { XLOG_ICL_NEED_FUA, "XLOG_ICL_NEED_FUA" }
+
+
+/*
+ * Log ticket flags
+ */
+#define XLOG_TIC_PERM_RESERV (1u << 0) /* permanent reservation */
+
+#define XLOG_TIC_FLAGS \
+ { 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
+
+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 */
+ atomic_t t_ref; /* ticket reference count */
+ int t_curr_res; /* current reservation */
+ int t_unit_res; /* unit reservation */
+ char t_ocnt; /* original unit count */
+ char t_cnt; /* current unit count */
+ uint8_t t_flags; /* properties of reservation */
+ int t_iclog_hdrs; /* iclog hdrs in t_curr_res */
+} 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;
+ unsigned int ic_flags;
+ void *ic_datap; /* pointer to iclog data */
+ 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;
+#endif
+ 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_csn_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_in_core *commit_iclog;
+ struct xlog_ticket *ticket; /* chkpt ticket */
+ atomic_t space_used; /* aggregate size of regions */
+ struct xfs_busy_extents busy_extents;
+ struct list_head log_items; /* log items in chkpt */
+ struct list_head lv_chain; /* logvecs being pushed */
+ struct list_head iclog_entry;
+ struct list_head committing; /* ctx committing list */
+ struct work_struct push_work;
+ atomic_t order_id;
+
+ /*
+ * CPUs that could have added items to the percpu CIL data. Access is
+ * coordinated with xc_ctx_lock.
+ */
+ struct cpumask cil_pcpmask;
+};
+
+/*
+ * Per-cpu CIL tracking items
+ */
+struct xlog_cil_pcp {
+ int32_t space_used;
+ uint32_t space_reserved;
+ struct list_head busy_extents;
+ struct list_head log_items;
+};
+
+/*
+ * 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;
+ unsigned long xc_flags;
+ atomic_t xc_iclog_hdrs;
+ struct workqueue_struct *xc_push_wq;
+
+ 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_csn_t xc_push_seq;
+ bool xc_push_commit_stable;
+ struct list_head xc_committing;
+ wait_queue_head_t xc_commit_wait;
+ wait_queue_head_t xc_start_wait;
+ xfs_csn_t xc_current_sequence;
+ wait_queue_head_t xc_push_wait; /* background push throttle */
+
+ void __percpu *xc_pcp; /* percpu CIL structures */
+} ____cacheline_aligned_in_smp;
+
+/* xc_flags bit values */
+#define XLOG_CIL_EMPTY 1
+#define XLOG_CIL_PCP_SPACE 2
+
+/*
+ * 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 only need to ensure the
+ * CIL is large enough to maintain sufficient in-memory relogging to avoid
+ * repeated physical writes of frequently modified metadata. If we allow the CIL
+ * to grow to a substantial fraction of the log, then we may be pinning hundreds
+ * of megabytes of metadata in memory until the CIL flushes. This can cause
+ * issues when we are running low on memory - pinned memory cannot be reclaimed,
+ * and the CIL consumes a lot of memory. Hence we need to set an upper physical
+ * size limit for the CIL that limits the maximum amount of memory pinned by the
+ * CIL but does not limit performance by reducing relogging efficiency
+ * significantly.
+ *
+ * As such, the CIL push threshold ends up being the smaller of two thresholds:
+ * - a threshold large enough that it allows CIL to be pushed and progress to be
+ * made without excessive blocking of incoming transaction commits. This is
+ * defined to be 12.5% of the log space - half the 25% push threshold of the
+ * AIL.
+ * - small enough that it doesn't pin excessive amounts of memory but maintains
+ * close to peak relogging efficiency. This is defined to be 16x the iclog
+ * buffer window (32MB) as measurements have shown this to be roughly the
+ * point of diminishing performance increases under highly concurrent
+ * modification workloads.
+ *
+ * To prevent the CIL from overflowing upper commit size bounds, we introduce a
+ * new threshold at which we block committing transactions until the background
+ * CIL commit commences and switches to a new context. While this is not a hard
+ * limit, it forces the process committing a transaction to the CIL to block and
+ * yeild the CPU, giving the CIL push work a chance to be scheduled and start
+ * work. This prevents a process running lots of transactions from overfilling
+ * the CIL because it is not yielding the CPU. We set the blocking limit at
+ * twice the background push space threshold so we keep in line with the AIL
+ * push thresholds.
+ *
+ * Note: this is not a -hard- limit as blocking is applied after the transaction
+ * is inserted into the CIL and the push has been triggered. It is largely a
+ * throttling mechanism that allows the CIL push to be scheduled and run. A hard
+ * limit will be difficult to implement without introducing global serialisation
+ * in the CIL commit fast path, and it's not at all clear that we actually need
+ * such hard limits given the ~7 years we've run without a hard limit before
+ * finding the first situation where a checkpoint size overflow actually
+ * occurred. Hence the simple throttle, and an ASSERT check to tell us that
+ * we've overrun the max size.
+ */
+#define XLOG_CIL_SPACE_LIMIT(log) \
+ min_t(int, (log)->l_logsize >> 3, BBTOB(XLOG_TOTAL_REC_SHIFT(log)) << 4)
+
+#define XLOG_CIL_BLOCKING_SPACE_LIMIT(log) \
+ (XLOG_CIL_SPACE_LIMIT(log) * 2)
+
+/*
+ * 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 */
+ long l_opstate; /* operational state */
+ 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;
+
+ /* log recovery lsn tracking (for buffer submission */
+ xfs_lsn_t l_recovery_lsn;
+
+ uint32_t l_iclog_roundoff;/* padding roundoff */
+
+ /* Users of log incompat features should take a read lock. */
+ struct rw_semaphore l_incompat_users;
+};
+
+/*
+ * Bits for operational state
+ */
+#define XLOG_ACTIVE_RECOVERY 0 /* in the middle of recovery */
+#define XLOG_RECOVERY_NEEDED 1 /* log was recovered */
+#define XLOG_IO_ERROR 2 /* log hit an I/O error, and being
+ shutdown */
+#define XLOG_TAIL_WARN 3 /* log tail verify warning issued */
+
+static inline bool
+xlog_recovery_needed(struct xlog *log)
+{
+ return test_bit(XLOG_RECOVERY_NEEDED, &log->l_opstate);
+}
+
+static inline bool
+xlog_in_recovery(struct xlog *log)
+{
+ return test_bit(XLOG_ACTIVE_RECOVERY, &log->l_opstate);
+}
+
+static inline bool
+xlog_is_shutdown(struct xlog *log)
+{
+ return test_bit(XLOG_IO_ERROR, &log->l_opstate);
+}
+
+/*
+ * Wait until the xlog_force_shutdown() has marked the log as shut down
+ * so xlog_is_shutdown() will always return true.
+ */
+static inline void
+xlog_shutdown_wait(
+ struct xlog *log)
+{
+ wait_var_event(&log->l_opstate, xlog_is_shutdown(log));
+}
+
+/* common routines */
+extern int
+xlog_recover(
+ struct xlog *log);
+extern int
+xlog_recover_finish(
+ 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 struct kmem_cache *xfs_log_ticket_cache;
+struct xlog_ticket *xlog_ticket_alloc(struct xlog *log, int unit_bytes,
+ int count, bool permanent);
+
+void xlog_print_tic_res(struct xfs_mount *mp, struct xlog_ticket *ticket);
+void xlog_print_trans(struct xfs_trans *);
+int xlog_write(struct xlog *log, struct xfs_cil_ctx *ctx,
+ struct list_head *lv_chain, struct xlog_ticket *tic,
+ uint32_t len);
+void xfs_log_ticket_ungrant(struct xlog *log, struct xlog_ticket *ticket);
+void xfs_log_ticket_regrant(struct xlog *log, struct xlog_ticket *ticket);
+
+void xlog_state_switch_iclogs(struct xlog *log, struct xlog_in_core *iclog,
+ int eventual_size);
+int xlog_state_release_iclog(struct xlog *log, struct xlog_in_core *iclog,
+ struct xlog_ticket *ticket);
+
+/*
+ * 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);
+void xlog_cil_commit(struct xlog *log, struct xfs_trans *tp,
+ xfs_csn_t *commit_seq, bool regrant);
+void xlog_cil_set_ctx_write_state(struct xfs_cil_ctx *ctx,
+ struct xlog_in_core *iclog);
+
+
+/*
+ * CIL force routines
+ */
+void xlog_cil_flush(struct xlog *log);
+xfs_lsn_t xlog_cil_force_seq(struct xlog *log, xfs_csn_t sequence);
+
+static inline void
+xlog_cil_force(struct xlog *log)
+{
+ xlog_cil_force_seq(log, log->l_cilp->xc_current_sequence);
+}
+
+/*
+ * 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(
+ struct wait_queue_head *wq,
+ struct spinlock *lock)
+ __releases(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);
+}
+
+int xlog_wait_on_iclog(struct xlog_in_core *iclog);
+
+/*
+ * 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 = READ_ONCE(log->l_curr_cycle);
+ smp_rmb();
+ 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.
+ */
+ 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;
+}
+
+/*
+ * Log vector and shadow buffers can be large, so we need to use kvmalloc() here
+ * to ensure success. Unfortunately, kvmalloc() only allows GFP_KERNEL contexts
+ * to fall back to vmalloc, so we can't actually do anything useful with gfp
+ * flags to control the kmalloc() behaviour within kvmalloc(). Hence kmalloc()
+ * will do direct reclaim and compaction in the slow path, both of which are
+ * horrendously expensive. We just want kmalloc to fail fast and fall back to
+ * vmalloc if it can't get somethign straight away from the free lists or
+ * buddy allocator. Hence we have to open code kvmalloc outselves here.
+ *
+ * This assumes that the caller uses memalloc_nofs_save task context here, so
+ * despite the use of GFP_KERNEL here, we are going to be doing GFP_NOFS
+ * allocations. This is actually the only way to make vmalloc() do GFP_NOFS
+ * allocations, so lets just all pretend this is a GFP_KERNEL context
+ * operation....
+ */
+static inline void *
+xlog_kvmalloc(
+ size_t buf_size)
+{
+ gfp_t flags = GFP_KERNEL;
+ void *p;
+
+ flags &= ~__GFP_DIRECT_RECLAIM;
+ flags |= __GFP_NOWARN | __GFP_NORETRY;
+ do {
+ p = kmalloc(buf_size, flags);
+ if (!p)
+ p = vmalloc(buf_size);
+ } while (!p);
+
+ return p;
+}
+
+#endif /* __XFS_LOG_PRIV_H__ */