FreeBSD/Linux Kernel Cross Reference
sys/sys/wapbl_replay.h

     /*      $NetBSD: wapbl_replay.h,v 1.1 2008/11/24 16:05:21 joerg Exp $   */
     
     /*-
      * Copyright (c) 2003,2008 The NetBSD Foundation, Inc.
      * All rights reserved.
      *
      * This code is derived from software contributed to The NetBSD Foundation
      * by Wasabi Systems, Inc.
      *
     * Redistribution and use in source and binary forms, with or without
     * modification, are permitted provided that the following conditions
     * are met:
     * 1. Redistributions of source code must retain the above copyright
     *    notice, this list of conditions and the following disclaimer.
     * 2. Redistributions in binary form must reproduce the above copyright
     *    notice, this list of conditions and the following disclaimer in the
     *    documentation and/or other materials provided with the distribution.
     *
     * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
     * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
     * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
     * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
     * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
     * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
     * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
     * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
     * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
     * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
     * POSSIBILITY OF SUCH DAMAGE.
     */
    
    #ifndef _SYS_WAPBL_REPLAY_H
    #define _SYS_WAPBL_REPLAY_H
    
    #include <sys/types.h>
    
    /* The WAPBL journal layout.
     * 
     * The journal consists of a header followed by a circular buffer
     * region.  The circular data area is described by the header
     * wc_circ_off, wc_circ_size, wc_head and wc_tail fields as bytes
     * from the start of the journal header.  New records are inserted
     * at wc_head and the oldest valid record can be found at wc_tail.
     * When ((wc_head == wc_tail) && (wc_head == 0)), the journal is empty.
     * The condition of ((wc_head == wc_tail) && (wc_head != 0))
     * indicates a full journal, although this condition is rare.
     *
     * The journal header as well as its records are marked by a 32bit
     * type tag and length for ease of parsing.  Journal records are
     * padded so as to fall on journal device block boundaries.
     */
    
    /*
     * The following are the 4 record types used by the journal:
     * Each tag indicates journal data organized by one of the
     * structures used below.
     */
    enum {
            WAPBL_WC_HEADER = 0x5741424c,   /* "WABL", struct wapbl_wc_header */
            WAPBL_WC_INODES,                /* struct wapbl_wc_inodelist */
            WAPBL_WC_REVOCATIONS,           /* struct wapbl_wc_blocklist */
            WAPBL_WC_BLOCKS,                /* struct wapbl_wc_blocklist */
    };
    
    /* null entry (on disk) */
    /* This structure isn't used directly, but shares its header
     * layout with all the other log structures for the purpose
     * of reading a log structure and determining its type
     */
    struct wapbl_wc_null {
            uint32_t        wc_type;        /* WAPBL_WC_* */
            int32_t         wc_len;
            uint8_t         wc_spare[0];    /* actually longer */
    };
    
    /* journal header (on-disk)
     * This record is found at the start of the
     * journal, but not within the circular buffer region.  As well as
     * describing the journal parameters and matching filesystem, it
     * additionally serves as the atomic update record for journal
     * updates.
     */
    struct wapbl_wc_header {
            uint32_t        wc_type;        /* WAPBL_WC_HEADER log magic number */
            int32_t         wc_len;         /* length of this journal entry */
            uint32_t        wc_checksum;
            uint32_t        wc_generation;
            int32_t         wc_fsid[2];
            uint64_t        wc_time;
            uint32_t        wc_timensec;
            uint32_t        wc_version;
            uint32_t        wc_log_dev_bshift;
            uint32_t        wc_fs_dev_bshift;
            int64_t         wc_head;
            int64_t         wc_tail;
            int64_t         wc_circ_off;    /* offset of of circ buffer region */
            int64_t         wc_circ_size;   /* size of circular buffer region */
            uint8_t         wc_spare[0];    /* actually longer */
    };
   
   /* list of blocks (on disk)
    * This record is used to describe a set of filesystem blocks,
    * and is used with two type tags, WAPBL_WC_BLOCKS and
    * WAPBL_WC_REVOCATIONS.
    * 
    * For WAPBL_WC_BLOCKS, a copy of each listed block can be found
    * starting at the next log device blocksize boundary.  starting at
    * one log device block since the start of the record.  This contains
    * the bulk of the filesystem journal data which is written using
    * these records before being written into the filesystem.
    *
    * The WAPBL_WC_REVOCATIONS record is used to indicate that any
    * previously listed blocks should not be written into the filesystem.
    * This is important so that deallocated and reallocated data blocks
    * do not get overwritten with stale data from the journal.  The
    * revocation records do not contain a copy of any actual block data.
    */
   struct wapbl_wc_blocklist {
           uint32_t        wc_type; /* WAPBL_WC_{REVOCATIONS,BLOCKS} */
           int32_t         wc_len;
           int32_t         wc_blkcount;
           int32_t         wc_unused;
           struct {
                   int64_t wc_daddr;
                   int32_t wc_unused;
                   int32_t wc_dlen;
           } wc_blocks[0];                 /* actually longer */
   };
   
   /* list of inodes (on disk)
    * This record is used to describe the set of inodes which
    * may be allocated but are unlinked.  Inodes end up listed here
    * while they are in the process of being initialized and
    * deinitialized.  Inodes unlinked while in use by a process
    * will be listed here and the actual deletion must be completed
    * on journal replay.
    */
   struct wapbl_wc_inodelist {
           uint32_t        wc_type; /* WAPBL_WC_INODES */
           int32_t         wc_len;
           int32_t         wc_inocnt;
           int32_t         wc_clear;       /* set if previously listed inodes 
                                              hould be ignored */
           struct {
                   uint32_t wc_inumber;
                   uint32_t wc_imode;
           } wc_inodes[0];         /* actually longer */
   };
   
   #endif /* _SYS_WAPBL_REPLAY_H */

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