FreeBSD/Linux Kernel Cross Reference
sys/contrib/openzfs/include/sys/zil_impl.h

     /*
      * CDDL HEADER START
      *
      * The contents of this file are subject to the terms of the
      * Common Development and Distribution License (the "License").
      * You may not use this file except in compliance with the License.
      *
      * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
      * or https://opensource.org/licenses/CDDL-1.0.
     * See the License for the specific language governing permissions
     * and limitations under the License.
     *
     * When distributing Covered Code, include this CDDL HEADER in each
     * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
     * If applicable, add the following below this CDDL HEADER, with the
     * fields enclosed by brackets "[]" replaced with your own identifying
     * information: Portions Copyright [yyyy] [name of copyright owner]
     *
     * CDDL HEADER END
     */
    /*
     * Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
     * Copyright (c) 2012, 2018 by Delphix. All rights reserved.
     */
    
    /* 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" {
    #endif
    
    /*
     * Possible 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
     * achieved 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_CLOSED,
        LWB_STATE_OPENED,
        LWB_STATE_ISSUED,
        LWB_STATE_WRITE_DONE,
        LWB_STATE_FLUSH_DONE,
        LWB_NUM_STATES
    } 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_fastwrite;  /* is blk marked for fastwrite? */
            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 */
           uint64_t        lwb_issued_txg; /* the txg when the write is issued */
           uint64_t        lwb_max_txg;    /* highest txg in this lwb */
           list_node_t     lwb_node;       /* zilog->zl_lwb_list linkage */
           list_t          lwb_itxs;       /* list of itx's */
           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 */
   
           kmutex_t        zl_lwb_io_lock; /* protect following members */
           uint64_t        zl_lwb_inflight[TXG_SIZE]; /* io issued, but not done */
           kcondvar_t      zl_lwb_io_cv;   /* signal when the flush is done */
           uint64_t        zl_lwb_max_issued_txg; /* max txg when lwb io issued */
   
           /*
            * Max block size for this ZIL.  Note that this can not be changed
            * while the ZIL is in use because consumers (ZPL/zvol) need to take
            * this into account when deciding between WR_COPIED and WR_NEED_COPY
            * (see zil_max_copied_data()).
            */
           uint64_t        zl_max_block_size;
   
           /* Pointer for per dataset zil sums */
           zil_sums_t *zl_sums;
   };
   
   typedef struct zil_bp_node {
           dva_t           zn_dva;
           avl_node_t      zn_node;
   } zil_bp_node_t;
   
   #ifdef  __cplusplus
   }
   #endif
   
   #endif  /* _SYS_ZIL_IMPL_H */

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