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* If applicable, add the following below this CDDL HEADER, with the
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* Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
* Copyright (c) 2012, 2017 by Delphix. All rights reserved.
* Copyright (c) 2014 Integros []
/* Portions Copyright 2010 Robert Milkowski */
#ifndef _SYS_ZIL_IMPL_H
#define _SYS_ZIL_IMPL_H
#include <sys/zil.h>
#include <sys/dmu_objset.h>
#ifdef __cplusplus
extern "C" {
* Possbile states for a given lwb structure.
* An lwb will start out in the "closed" state, and then transition to
* the "opened" state via a call to zil_lwb_write_open(). When
* transitioning from "closed" to "opened" the zilog's "zl_issuer_lock"
* must be held.
* After the lwb is "opened", it can transition into the "issued" state
* via zil_lwb_write_issue(). Again, the zilog's "zl_issuer_lock" must
* be held when making this transition.
* After the lwb's write zio completes, it transitions into the "write
* done" state via zil_lwb_write_done(); and then into the "flush done"
* state via zil_lwb_flush_vdevs_done(). When transitioning from
* "issued" to "write done", and then from "write done" to "flush done",
* the zilog's "zl_lock" must be held, *not* the "zl_issuer_lock".
* The zilog's "zl_issuer_lock" can become heavily contended in certain
* workloads, so we specifically avoid acquiring that lock when
* transitioning an lwb from "issued" to "done". This allows us to avoid
* having to acquire the "zl_issuer_lock" for each lwb ZIO completion,
* which would have added more lock contention on an already heavily
* contended lock.
* Additionally, correctness when reading an lwb's state is often
* acheived by exploiting the fact that these state transitions occur in
* this specific order; i.e. "closed" to "opened" to "issued" to "done".
* Thus, if an lwb is in the "closed" or "opened" state, holding the
* "zl_issuer_lock" will prevent a concurrent thread from transitioning
* that lwb to the "issued" state. Likewise, if an lwb is already in the
* "issued" state, holding the "zl_lock" will prevent a concurrent
* thread from transitioning that lwb to the "write done" state.
typedef enum {
} lwb_state_t;
* Log write block (lwb)
* Prior to an lwb being issued to disk via zil_lwb_write_issue(), it
* will be protected by the zilog's "zl_issuer_lock". Basically, prior
* to it being issued, it will only be accessed by the thread that's
* holding the "zl_issuer_lock". After the lwb is issued, the zilog's
* "zl_lock" is used to protect the lwb against concurrent access.
typedef struct lwb {
zilog_t *lwb_zilog; /* back pointer to log struct */
blkptr_t lwb_blk; /* on disk address of this log blk */
boolean_t lwb_slog; /* lwb_blk is on SLOG device */
int lwb_nused; /* # used bytes in buffer */
int lwb_sz; /* size of block and buffer */
lwb_state_t lwb_state; /* the state of this lwb */
char *lwb_buf; /* log write buffer */
zio_t *lwb_write_zio; /* zio for the lwb buffer */
zio_t *lwb_root_zio; /* root zio for lwb write and flushes */
dmu_tx_t *lwb_tx; /* tx for log block allocation */
uint64_t lwb_max_txg; /* highest txg in this lwb */
list_node_t lwb_node; /* zilog->zl_lwb_list linkage */
list_t lwb_waiters; /* list of zil_commit_waiter's */
avl_tree_t lwb_vdev_tree; /* vdevs to flush after lwb write */
kmutex_t lwb_vdev_lock; /* protects lwb_vdev_tree */
hrtime_t lwb_issued_timestamp; /* when was the lwb issued? */
} lwb_t;
* ZIL commit waiter.
* This structure is allocated each time zil_commit() is called, and is
* used by zil_commit() to communicate with other parts of the ZIL, such
* that zil_commit() can know when it safe for it return. For more
* details, see the comment above zil_commit().
* The "zcw_lock" field is used to protect the commit waiter against
* concurrent access. This lock is often acquired while already holding
* the zilog's "zl_issuer_lock" or "zl_lock"; see the functions
* zil_process_commit_list() and zil_lwb_flush_vdevs_done() as examples
* of this. Thus, one must be careful not to acquire the
* "zl_issuer_lock" or "zl_lock" when already holding the "zcw_lock";
* e.g. see the zil_commit_waiter_timeout() function.
typedef struct zil_commit_waiter {
kcondvar_t zcw_cv; /* signalled when "done" */
kmutex_t zcw_lock; /* protects fields of this struct */
list_node_t zcw_node; /* linkage in lwb_t:lwb_waiter list */
lwb_t *zcw_lwb; /* back pointer to lwb when linked */
boolean_t zcw_done; /* B_TRUE when "done", else B_FALSE */
int zcw_zio_error; /* contains the zio io_error value */
} zil_commit_waiter_t;
* Intent log transaction lists
typedef struct itxs {
list_t i_sync_list; /* list of synchronous itxs */
avl_tree_t i_async_tree; /* tree of foids for async itxs */
} itxs_t;
typedef struct itxg {
kmutex_t itxg_lock; /* lock for this structure */
uint64_t itxg_txg; /* txg for this chain */
itxs_t *itxg_itxs; /* sync and async itxs */
} itxg_t;
/* for async nodes we build up an AVL tree of lists of async itxs per file */
typedef struct itx_async_node {
uint64_t ia_foid; /* file object id */
list_t ia_list; /* list of async itxs for this foid */
avl_node_t ia_node; /* AVL tree linkage */
} itx_async_node_t;
* Vdev flushing: during a zil_commit(), we build up an AVL tree of the vdevs
* we've touched so we know which ones need a write cache flush at the end.
typedef struct zil_vdev_node {
uint64_t zv_vdev; /* vdev to be flushed */
avl_node_t zv_node; /* AVL tree linkage */
} zil_vdev_node_t;
#define ZIL_PREV_BLKS 16
* Stable storage intent log management structure. One per dataset.
struct zilog {
kmutex_t zl_lock; /* protects most zilog_t fields */
struct dsl_pool *zl_dmu_pool; /* DSL pool */
spa_t *zl_spa; /* handle for read/write log */
const zil_header_t *zl_header; /* log header buffer */
objset_t *zl_os; /* object set we're logging */
zil_get_data_t *zl_get_data; /* callback to get object content */
lwb_t *zl_last_lwb_opened; /* most recent lwb opened */
hrtime_t zl_last_lwb_latency; /* zio latency of last lwb done */
uint64_t zl_lr_seq; /* on-disk log record sequence number */
uint64_t zl_commit_lr_seq; /* last committed on-disk lr seq */
uint64_t zl_destroy_txg; /* txg of last zil_destroy() */
uint64_t zl_replayed_seq[TXG_SIZE]; /* last replayed rec seq */
uint64_t zl_replaying_seq; /* current replay seq number */
uint32_t zl_suspend; /* log suspend count */
kcondvar_t zl_cv_suspend; /* log suspend completion */
uint8_t zl_suspending; /* log is currently suspending */
uint8_t zl_keep_first; /* keep first log block in destroy */
uint8_t zl_replay; /* replaying records while set */
uint8_t zl_stop_sync; /* for debugging */
kmutex_t zl_issuer_lock; /* single writer, per ZIL, at a time */
uint8_t zl_logbias; /* latency or throughput */
uint8_t zl_sync; /* synchronous or asynchronous */
int zl_parse_error; /* last zil_parse() error */
uint64_t zl_parse_blk_seq; /* highest blk seq on last parse */
uint64_t zl_parse_lr_seq; /* highest lr seq on last parse */
uint64_t zl_parse_blk_count; /* number of blocks parsed */
uint64_t zl_parse_lr_count; /* number of log records parsed */
itxg_t zl_itxg[TXG_SIZE]; /* intent log txg chains */
list_t zl_itx_commit_list; /* itx list to be committed */
uint64_t zl_cur_used; /* current commit log size used */
list_t zl_lwb_list; /* in-flight log write list */
avl_tree_t zl_bp_tree; /* track bps during log parse */
clock_t zl_replay_time; /* lbolt of when replay started */
uint64_t zl_replay_blks; /* number of log blocks replayed */
zil_header_t zl_old_header; /* debugging aid */
uint_t zl_prev_blks[ZIL_PREV_BLKS]; /* size - sector rounded */
uint_t zl_prev_rotor; /* rotor for zl_prev[] */
txg_node_t zl_dirty_link; /* protected by dp_dirty_zilogs list */
uint64_t zl_dirty_max_txg; /* highest txg used to dirty zilog */
typedef struct zil_bp_node {
dva_t zn_dva;
avl_node_t zn_node;
} zil_bp_node_t;
* Maximum amount of write data that can be put into single log block.
#define ZIL_MAX_LOG_DATA (SPA_OLD_MAXBLOCKSIZE - sizeof (zil_chain_t) - \
sizeof (lr_write_t))
* Maximum amount of log space we agree to waste to reduce number of
* WR_NEED_COPY chunks to reduce zl_get_data() overhead (~12%).
* Maximum amount of write data for WR_COPIED. Fall back to WR_NEED_COPY
* as more space efficient if we can't fit at least two log records into
* maximum sized log block.
sizeof (zil_chain_t)) / 2 - sizeof (lr_write_t))
#ifdef __cplusplus
#endif /* _SYS_ZIL_IMPL_H */