HAMMER 28/many: Implement zoned blockmap

[dragonfly.git] / sys / vfs / hammer / hammer_disk.h

/*
 * Copyright (c) 2007 The DragonFly Project.  All rights reserved.
 * 
 * This code is derived from software contributed to The DragonFly Project
 * by Matthew Dillon <dillon@backplane.com>
 * 
 * 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.
 * 3. Neither the name of The DragonFly Project nor the names of its
 *    contributors may be used to endorse or promote products derived
 *    from this software without specific, prior written permission.
 * 
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS 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
 * COPYRIGHT HOLDERS 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.
 * 
 * $DragonFly: src/sys/vfs/hammer/hammer_disk.h,v 1.23 2008/02/10 09:51:01 dillon Exp $
 */

#ifndef VFS_HAMMER_DISK_H_
#define VFS_HAMMER_DISK_H_

#ifndef _SYS_UUID_H_
#include <sys/uuid.h>
#endif

/*
 * The structures below represent the on-disk format for a HAMMER
 * filesystem.  Note that all fields for on-disk structures are naturally
 * aligned.  The host endian format is used - compatibility is possible
 * if the implementation detects reversed endian and adjusts data accordingly.
 *
 * Most of HAMMER revolves around the concept of an object identifier.  An
 * obj_id is a 64 bit quantity which uniquely identifies a filesystem object
 * FOR THE ENTIRE LIFE OF THE FILESYSTEM.  This uniqueness allows backups
 * and mirrors to retain varying amounts of filesystem history by removing
 * any possibility of conflict through identifier reuse.
 *
 * A HAMMER filesystem may spam multiple volumes.
 *
 * A HAMMER filesystem uses a 16K filesystem buffer size.  All filesystem
 * I/O is done in multiples of 16K.  Most buffer-sized headers such as those
 * used by volumes, super-clusters, clusters, and basic filesystem buffers
 * use fixed-sized A-lists which are heavily dependant on HAMMER_BUFSIZE.
 *
 * Per-volume storage limit: 52 bits            4096 TB
 * Per-Zone storage limit: 59 bits              512 KTB (due to blockmap)
 * Per-filesystem storage limit: 60 bits        1 MTB
 */
#define HAMMER_BUFSIZE          16384
#define HAMMER_BUFMASK          (HAMMER_BUFSIZE - 1)
#define HAMMER_MAXDATA          (256*1024)
#define HAMMER_BUFFER_BITS      14

#if (1 << HAMMER_BUFFER_BITS) != HAMMER_BUFSIZE
#error "HAMMER_BUFFER_BITS BROKEN"
#endif

#define HAMMER_BUFSIZE64        ((u_int64_t)HAMMER_BUFSIZE)
#define HAMMER_BUFMASK64        ((u_int64_t)HAMMER_BUFMASK)

#define HAMMER_OFF_ZONE_MASK    0xF000000000000000ULL /* zone portion */
#define HAMMER_OFF_VOL_MASK     0x0FF0000000000000ULL /* volume portion */
#define HAMMER_OFF_SHORT_MASK   0x000FFFFFFFFFFFFFULL /* offset portion */
#define HAMMER_OFF_LONG_MASK    0x0FFFFFFFFFFFFFFFULL /* offset portion */
#define HAMMER_OFF_SHORT_REC_MASK 0x000FFFFFFF000000ULL /* recovery boundary */
#define HAMMER_OFF_LONG_REC_MASK 0x0FFFFFFFFF000000ULL /* recovery boundary */
#define HAMMER_RECOVERY_BND     0x0000000001000000ULL

/*
 * Hammer transction ids are 64 bit unsigned integers and are usually
 * synchronized with the time of day in nanoseconds.
 *
 * Hammer offsets are used for FIFO indexing and embed a cycle counter
 * and volume number in addition to the offset.  Most offsets are required
 * to be 64-byte aligned.
 */
typedef u_int64_t hammer_tid_t;
typedef u_int64_t hammer_off_t;

#define HAMMER_MIN_TID          0ULL                    /* unsigned */
#define HAMMER_MAX_TID          0xFFFFFFFFFFFFFFFFULL   /* unsigned */
#define HAMMER_MIN_KEY          -0x8000000000000000LL   /* signed */
#define HAMMER_MAX_KEY          0x7FFFFFFFFFFFFFFFLL    /* signed */
#define HAMMER_MIN_OBJID        HAMMER_MIN_KEY          /* signed */
#define HAMMER_MAX_OBJID        HAMMER_MAX_KEY          /* signed */
#define HAMMER_MIN_RECTYPE      0x0U                    /* unsigned */
#define HAMMER_MAX_RECTYPE      0xFFFFU                 /* unsigned */
#define HAMMER_MIN_OFFSET       0ULL                    /* unsigned */
#define HAMMER_MAX_OFFSET       0xFFFFFFFFFFFFFFFFULL   /* unsigned */

/*
 * hammer_off_t has several different encodings.  Note that not all zones
 * encode a vol_no.
 *
 * zone 0 (z,v,o):      reserved (for sanity)
 * zone 1 (z,v,o):      raw volume relative (offset 0 is the volume header)
 * zone 2 (z,v,o):      raw buffer relative (offset 0 is the first buffer)
 * zone 3 (z,o):        undo fifo       - blockmap backed
 *
 * zone 8 (z,o):        B-Tree          - blkmap-backed
 * zone 9 (z,o):        Record          - blkmap-backed
 * zone 10 (z,o):       Large-data      - blkmap-backed
 */

#define HAMMER_ZONE_RAW_VOLUME          0x1000000000000000ULL
#define HAMMER_ZONE_RAW_BUFFER          0x2000000000000000ULL
#define HAMMER_ZONE_UNDO                0x3000000000000000ULL
#define HAMMER_ZONE_RESERVED04          0x4000000000000000ULL
#define HAMMER_ZONE_RESERVED05          0x5000000000000000ULL
#define HAMMER_ZONE_RESERVED06          0x6000000000000000ULL
#define HAMMER_ZONE_RESERVED07          0x7000000000000000ULL
#define HAMMER_ZONE_BTREE               0x8000000000000000ULL
#define HAMMER_ZONE_RECORD              0x9000000000000000ULL
#define HAMMER_ZONE_LARGE_DATA          0xA000000000000000ULL
#define HAMMER_ZONE_SMALL_DATA          0xB000000000000000ULL
#define HAMMER_ZONE_RESERVED0C          0xC000000000000000ULL
#define HAMMER_ZONE_RESERVED0D          0xD000000000000000ULL
#define HAMMER_ZONE_RESERVED0E          0xE000000000000000ULL
#define HAMMER_ZONE_RESERVED0F          0xF000000000000000ULL

#define HAMMER_ZONE_RAW_VOLUME_INDEX    1
#define HAMMER_ZONE_RAW_BUFFER_INDEX    2
#define HAMMER_ZONE_UNDO_INDEX          3
#define HAMMER_ZONE_BTREE_INDEX         8
#define HAMMER_ZONE_RECORD_INDEX        9
#define HAMMER_ZONE_LARGE_DATA_INDEX    10
#define HAMMER_ZONE_SMALL_DATA_INDEX    11

#define HAMMER_MAX_ZONES                16

#define HAMMER_VOL_ENCODE(vol_no)                       \
        ((hammer_off_t)((vol_no) & 255) << 52)
#define HAMMER_VOL_DECODE(ham_off)                      \
        (int32_t)(((hammer_off_t)(ham_off) >> 52) & 255)
#define HAMMER_ZONE_DECODE(ham_off)                     \
        (int32_t)(((hammer_off_t)(ham_off) >> 60))
#define HAMMER_SHORT_OFF_ENCODE(offset)                 \
        ((hammer_off_t)(offset) & HAMMER_OFF_SHORT_MASK)
#define HAMMER_LONG_OFF_ENCODE(offset)                  \
        ((hammer_off_t)(offset) & HAMMER_OFF_LONG_MASK)

#define HAMMER_ENCODE_RAW_VOLUME(vol_no, offset)        \
        (HAMMER_ZONE_RAW_VOLUME |                       \
        HAMMER_VOL_ENCODE(vol_no) |                     \
        HAMMER_SHORT_OFF_ENCODE(offset))

#define HAMMER_ENCODE_RAW_BUFFER(vol_no, offset)        \
        (HAMMER_ZONE_RAW_BUFFER |                       \
        HAMMER_VOL_ENCODE(vol_no) |                     \
        HAMMER_SHORT_OFF_ENCODE(offset))

/*
 * Large-Block backing store
 *
 * A blockmap is a two-level map which translates a blockmap-backed zone
 * offset into a raw zone 2 offset.  Each layer handles 18 bits.  The 8M
 * large-block size is 23 bits so two layers gives us 23+18+18 = 59 bits
 * of address space.
 */
#define HAMMER_LARGEBLOCK_SIZE          (8192 * 1024)
#define HAMMER_LARGEBLOCK_MASK          (HAMMER_LARGEBLOCK_SIZE - 1)
#define HAMMER_LARGEBLOCK_MASK64        ((u_int64_t)HAMMER_LARGEBLOCK_SIZE - 1)
#define HAMMER_LARGEBLOCK_BITS          23
#if (1 << HAMMER_LARGEBLOCK_BITS) != HAMMER_LARGEBLOCK_SIZE
#error "HAMMER_LARGEBLOCK_BITS BROKEN"
#endif

#define HAMMER_BUFFERS_PER_LARGEBLOCK                   \
        (HAMMER_LARGEBLOCK_SIZE / HAMMER_BUFSIZE)
#define HAMMER_BUFFERS_PER_LARGEBLOCK_MASK              \
        (HAMMER_BUFFERS_PER_LARGEBLOCK - 1)
#define HAMMER_BUFFERS_PER_LARGEBLOCK_MASK64            \
        ((hammer_off_t)HAMMER_BUFFERS_PER_LARGEBLOCK_MASK)

#define HAMMER_BLOCKMAP_RADIX                           \
        (HAMMER_LARGEBLOCK_SIZE / sizeof(struct hammer_blockmap_entry))
#define HAMMER_BLOCKMAP_RADIX_MASK                      \
        (HAMMER_BLOCKMAP_RADIX - 1)
#define HAMMER_BLOCKMAP_BITS            18
#if (1 << HAMMER_BLOCKMAP_BITS) != (HAMMER_LARGEBLOCK_SIZE / 32)
#error "HAMMER_BLOCKMAP_BITS BROKEN"
#endif

#define HAMMER_LARGEBLOCK_LAYER1                        \
        ((hammer_off_t)HAMMER_LARGEBLOCK_SIZE * HAMMER_BLOCKMAP_RADIX)
#define HAMMER_LARGEBLOCK_LAYER2                        \
        (HAMMER_LARGEBLOCK_LAYER1 * HAMMER_BLOCKMAP_RADIX)

#define HAMMER_LARGEBLOCK_LAYER1_MASK   (HAMMER_LARGEBLOCK_LAYER1 - 1)
#define HAMMER_LARGEBLOCK_LAYER2_MASK   (HAMMER_LARGEBLOCK_LAYER2 - 1)

struct hammer_blockmap_entry {
        hammer_off_t    phys_offset;    /* zone-2 physical offset */
        int32_t         bytes_free;     /* bytes free within the big-block */
        u_int32_t       entry_crc;
        u_int32_t       reserved01;
        u_int32_t       reserved02;
        hammer_off_t    alloc_offset;   /* zone-X logical offset */
};

typedef struct hammer_blockmap_entry *hammer_blockmap_entry_t;

/*
 * All on-disk HAMMER structures which make up elements of the FIFO contain
 * a hammer_fifo_head and hammer_fifo_tail structure.  This structure
 * contains all the information required to validate the fifo element
 * and to scan the fifo in either direction.  The head is typically embedded
 * in higher level hammer on-disk structures while the tail is typically
 * out-of-band.  hdr_size is the size of the whole mess, including the tail.
 *
 * Nearly all such structures are guaranteed to not cross a 16K filesystem
 * buffer boundary.  The one exception is a record, whos related data may
 * cross a buffer boundary.
 *
 * HAMMER guarantees alignment with a fifo head structure at 16MB intervals
 * (i.e. the base of the buffer will not be in the middle of a data record).
 * This is used to allow the recovery code to re-sync after hitting corrupted
 * data.
 *
 * PAD elements are allowed to take up only 8 bytes of space as a special
 * case, containing only hdr_signature, hdr_type, and hdr_size fields,
 * and with the tail overloaded onto the head structure for 8 bytes total.
 */
#define HAMMER_HEAD_ONDISK_SIZE         24
#define HAMMER_HEAD_RECOVERY_ALIGNMENT  (16 * 1024 * 1024)
#define HAMMER_HEAD_ALIGN               8
#define HAMMER_HEAD_ALIGN_MASK          (HAMMER_HEAD_ALIGN - 1)
#define HAMMER_TAIL_ONDISK_SIZE         8

struct hammer_fifo_head {
        u_int16_t hdr_signature;
        u_int16_t hdr_type;
        u_int32_t hdr_size;     /* aligned size of the whole mess */
        u_int32_t hdr_crc;
        u_int32_t hdr_reserved02;
        hammer_tid_t hdr_seq;   /* related sequence number */
};

struct hammer_fifo_tail {
        u_int16_t tail_signature;
        u_int16_t tail_type;
        u_int32_t tail_size;    /* aligned size of the whole mess */
};

typedef struct hammer_fifo_head *hammer_fifo_head_t;
typedef struct hammer_fifo_tail *hammer_fifo_tail_t;

/*
 * Fifo header types.
 */
#define HAMMER_HEAD_TYPE_PAD    (0x0040U|HAMMER_HEAD_FLAG_FREE)
#define HAMMER_HEAD_TYPE_VOL    0x0041U         /* Volume (dummy header) */
#define HAMMER_HEAD_TYPE_BTREE  0x0042U         /* B-Tree node */
#define HAMMER_HEAD_TYPE_UNDO   0x0043U         /* random UNDO information */
#define HAMMER_HEAD_TYPE_DELETE 0x0044U         /* record deletion */
#define HAMMER_HEAD_TYPE_RECORD 0x0045U         /* Filesystem record */

#define HAMMER_HEAD_FLAG_FREE   0x8000U         /* Indicates object freed */

#define HAMMER_HEAD_SIGNATURE   0xC84EU
#define HAMMER_TAIL_SIGNATURE   0xC74FU

/*
 * Misc FIFO structures (except for the B-Tree node and hammer record)
 */
struct hammer_fifo_undo {
        struct hammer_fifo_head head;
        hammer_off_t            undo_offset;
        /* followed by data */
};

typedef struct hammer_fifo_undo *hammer_fifo_undo_t;

/*
 * Volume header types
 */
#define HAMMER_FSBUF_VOLUME     0xC8414D4DC5523031ULL   /* HAMMER01 */
#define HAMMER_FSBUF_VOLUME_REV 0x313052C54D4D41C8ULL   /* (reverse endian) */

/*
 * The B-Tree structures need hammer_fsbuf_head.
 */
#include "hammer_btree.h"

/*
 * HAMMER Volume header
 *
 * A HAMMER filesystem is built from any number of block devices,  Each block
 * device contains a volume header followed by however many buffers fit
 * into the volume.
 *
 * One of the volumes making up a HAMMER filesystem is the master, the
 * rest are slaves.  It does not have to be volume #0.
 *
 * The volume header takes up an entire 16K filesystem buffer and may
 * represent up to 64KTB (65536 TB) of space.
 *
 * Special field notes:
 *
 *      vol_bot_beg - offset of boot area (mem_beg - bot_beg bytes)
 *      vol_mem_beg - offset of memory log (clu_beg - mem_beg bytes)
 *      vol_buf_beg - offset of the first buffer.
 *
 *      The memory log area allows a kernel to cache new records and data
 *      in memory without allocating space in the actual filesystem to hold
 *      the records and data.  In the event that a filesystem becomes full,
 *      any records remaining in memory can be flushed to the memory log
 *      area.  This allows the kernel to immediately return success.
 */

#define HAMMER_BOOT_MINBYTES            (32*1024)
#define HAMMER_BOOT_NOMBYTES            (64LL*1024*1024)
#define HAMMER_BOOT_MAXBYTES            (256LL*1024*1024)

#define HAMMER_MEM_MINBYTES             (256*1024)
#define HAMMER_MEM_NOMBYTES             (1LL*1024*1024*1024)
#define HAMMER_MEM_MAXBYTES             (64LL*1024*1024*1024)

struct hammer_volume_ondisk {
        u_int64_t vol_signature;/* Signature */

        int64_t vol_bot_beg;    /* byte offset of boot area or 0 */
        int64_t vol_mem_beg;    /* byte offset of memory log or 0 */
        int64_t vol_buf_beg;    /* byte offset of first buffer in volume */
        int64_t vol_buf_end;    /* byte offset of volume EOF (on buf bndry) */
        int64_t vol_locked;     /* reserved clusters are >= this offset */

        uuid_t    vol_fsid;     /* identify filesystem */
        uuid_t    vol_fstype;   /* identify filesystem type */
        char      vol_name[64]; /* Name of volume */

        int32_t vol_no;         /* volume number within filesystem */
        int32_t vol_count;      /* number of volumes making up FS */

        u_int32_t vol_version;  /* version control information */
        u_int32_t vol_reserved01;
        u_int32_t vol_flags;    /* volume flags */
        u_int32_t vol_rootvol;  /* which volume is the root volume? */

        int32_t vol_reserved04;
        int32_t vol_reserved05;
        u_int32_t vol_reserved06;
        u_int32_t vol_reserved07;

        int32_t vol_blocksize;          /* for statfs only */
        int32_t vol_reserved08;
        int64_t vol_nblocks;            /* total allocatable hammer bufs */

        /*
         * bigblock freemap. 
         *
         * XXX not implemented yet, just use a sequential index at
         * the moment.
         */
        hammer_off_t vol0_free_off;

        /*
         * These fields are initialized and space is reserved in every
         * volume making up a HAMMER filesytem, but only the master volume
         * contains valid data.
         */
        int64_t vol0_stat_bytes;        /* for statfs only */
        int64_t vol0_stat_inodes;       /* for statfs only */
        int64_t vol0_stat_records;      /* total records in filesystem */
        hammer_off_t vol0_btree_root;   /* B-Tree root */
        hammer_tid_t vol0_next_tid;     /* highest synchronized TID */
        hammer_tid_t vol0_next_seq;     /* next SEQ no for undo */

        /*
         * Blockmaps for zones.  Not all zones use a blockmap.
         */
        struct hammer_blockmap_entry vol0_blockmap[HAMMER_MAX_ZONES];

};

typedef struct hammer_volume_ondisk *hammer_volume_ondisk_t;

#define HAMMER_VOLF_VALID               0x0001  /* valid entry */
#define HAMMER_VOLF_OPEN                0x0002  /* volume is open */

/*
 * All HAMMER records have a common 64-byte base and a 32 byte extension,
 * plus a possible data reference.  The data reference can be in-band or
 * out-of-band.
 */

#define HAMMER_RECORD_SIZE              (64+32)

struct hammer_base_record {
        u_int32_t       signature;      /* record signature */
        u_int32_t       data_crc;       /* data crc */
        struct hammer_base_elm base;    /* 40 byte base element */
        hammer_off_t    data_off;       /* in-band or out-of-band */
        int32_t         data_len;       /* size of data in bytes */
        u_int32_t       reserved02;
};

/*
 * Record types are fairly straightforward.  The B-Tree includes the record
 * type in its index sort.
 *
 * In particular please note that it is possible to create a pseudo-
 * filesystem within a HAMMER filesystem by creating a special object
 * type within a directory.  Pseudo-filesystems are used as replication
 * targets and even though they are built within a HAMMER filesystem they
 * get their own obj_id space (and thus can serve as a replication target)
 * and look like a mount point to the system.
 *
 * Inter-cluster records are special-cased in the B-Tree.  These records
 * are referenced from a B-Tree INTERNAL node, NOT A LEAF.  This means
 * that the element in the B-Tree node is actually a boundary element whos
 * base element fields, including rec_type, reflect the boundary, NOT
 * the inter-cluster record type.
 *
 * HAMMER_RECTYPE_CLUSTER - only set in the actual inter-cluster record,
 * not set in the left or right boundary elements around the inter-cluster
 * reference of an internal node in the B-Tree (because doing so would
 * interfere with the boundary tests).
 *
 * NOTE: hammer_ip_delete_range_all() deletes all record types greater
 * then HAMMER_RECTYPE_INODE.
 */
#define HAMMER_RECTYPE_UNKNOWN          0
#define HAMMER_RECTYPE_LOWEST           1       /* lowest record type avail */
#define HAMMER_RECTYPE_INODE            1       /* inode in obj_id space */
#define HAMMER_RECTYPE_PSEUDO_INODE     2       /* pseudo filesysem */
#define HAMMER_RECTYPE_CLUSTER          3       /* inter-cluster reference */
#define HAMMER_RECTYPE_DATA             0x10
#define HAMMER_RECTYPE_DIRENTRY         0x11
#define HAMMER_RECTYPE_DB               0x12
#define HAMMER_RECTYPE_EXT              0x13    /* ext attributes */
#define HAMMER_RECTYPE_FIX              0x14    /* fixed attribute */

#define HAMMER_FIXKEY_SYMLINK           1

#define HAMMER_OBJTYPE_UNKNOWN          0       /* (never exists on-disk) */
#define HAMMER_OBJTYPE_DIRECTORY        1
#define HAMMER_OBJTYPE_REGFILE          2
#define HAMMER_OBJTYPE_DBFILE           3
#define HAMMER_OBJTYPE_FIFO             4
#define HAMMER_OBJTYPE_CDEV             5
#define HAMMER_OBJTYPE_BDEV             6
#define HAMMER_OBJTYPE_SOFTLINK         7
#define HAMMER_OBJTYPE_PSEUDOFS         8       /* pseudo filesystem obj */

/*
 * A HAMMER inode record.
 *
 * This forms the basis for a filesystem object.  obj_id is the inode number,
 * key1 represents the pseudo filesystem id for security partitioning
 * (preventing cross-links and/or restricting a NFS export and specifying the
 * security policy), and key2 represents the data retention policy id.
 *
 * Inode numbers are 64 bit quantities which uniquely identify a filesystem
 * object for the ENTIRE life of the filesystem, even after the object has
 * been deleted.  For all intents and purposes inode numbers are simply 
 * allocated by incrementing a sequence space.
 *
 * There is an important distinction between the data stored in the inode
 * record and the record's data reference.  The record references a
 * hammer_inode_data structure but the filesystem object size and hard link
 * count is stored in the inode record itself.  This allows multiple inodes
 * to share the same hammer_inode_data structure.  This is possible because
 * any modifications will lay out new data.  The HAMMER implementation need
 * not use the data-sharing ability when laying down new records.
 *
 * A HAMMER inode is subject to the same historical storage requirements
 * as any other record.  In particular any change in filesystem or hard link
 * count will lay down a new inode record when the filesystem is synced to
 * disk.  This can lead to a lot of junk records which get cleaned up by
 * the data retention policy.
 *
 * The ino_atime and ino_mtime fields are a special case.  Modifications to
 * these fields do NOT lay down a new record by default, though the values
 * are effectively frozen for snapshots which access historical versions
 * of the inode record due to other operations.  This means that atime will
 * not necessarily be accurate in snapshots, backups, or mirrors.  mtime
 * will be accurate in backups and mirrors since it can be regenerated from
 * the mirroring stream.
 *
 * Because nlinks is historically retained the hardlink count will be
 * accurate when accessing a HAMMER filesystem snapshot.
 */
struct hammer_inode_record {
        struct hammer_base_record base;
        u_int64_t ino_atime;    /* last access time (not historical) */
        u_int64_t ino_mtime;    /* last modified time (not historical) */
        u_int64_t ino_size;     /* filesystem object size */
        u_int64_t ino_nlinks;   /* hard links */
};

/*
 * Data records specify the entire contents of a regular file object,
 * including attributes.  Small amounts of data can theoretically be
 * embedded in the record itself but the use of this ability verses using
 * an out-of-band data reference depends on the implementation.
 */
struct hammer_data_record {
        struct hammer_base_record base;
        char    data[32];
};

/*
 * A directory entry specifies the HAMMER filesystem object id, a copy of
 * the file type, and file name (either embedded or as out-of-band data).
 * If the file name is short enough to fit into den_name[] (including a
 * terminating nul) then it will be embedded in the record, otherwise it
 * is stored out-of-band.  The base record's data reference always points
 * to the nul-terminated filename regardless.
 *
 * Directory entries are indexed with a 128 bit namekey rather then an
 * offset.  A portion of the namekey is an iterator or randomizer to deal
 * with collisions.
 *
 * NOTE: base.base.obj_type holds the filesystem object type of obj_id,
 *       e.g. a den_type equivalent.
 *
 * NOTE: den_name / the filename data reference is NOT terminated with \0.
 *
 */
struct hammer_entry_record {
        struct hammer_base_record base;
        u_int64_t obj_id;               /* object being referenced */
        u_int64_t reserved01;
        char    name[16];
};

/*
 * Hammer rollup record
 */
union hammer_record_ondisk {
        struct hammer_base_record       base;
        struct hammer_inode_record      inode;
        struct hammer_data_record       data;
        struct hammer_entry_record      entry;
};

typedef union hammer_record_ondisk *hammer_record_ondisk_t;

/*
 * HAMMER UNIX Attribute data
 *
 * The data reference in a HAMMER inode record points to this structure.  Any
 * modifications to the contents of this structure will result in a record
 * replacement operation.
 *
 * short_data_off allows a small amount of data to be embedded in the
 * hammer_inode_data structure.  HAMMER typically uses this to represent
 * up to 64 bytes of data, or to hold symlinks.  Remember that allocations
 * are in powers of 2 so 64, 192, 448, or 960 bytes of embedded data is
 * support (64+64, 64+192, 64+448 64+960).
 *
 * parent_obj_id is only valid for directories (which cannot be hard-linked),
 * and specifies the parent directory obj_id.  This field will also be set
 * for non-directory inodes as a recovery aid, but can wind up specifying
 * stale information.  However, since object id's are not reused, the worse
 * that happens is that the recovery code is unable to use it.
 */
struct hammer_inode_data {
        u_int16_t version;      /* inode data version */
        u_int16_t mode;         /* basic unix permissions */
        u_int32_t uflags;       /* chflags */
        u_int32_t rmajor;       /* used by device nodes */
        u_int32_t rminor;       /* used by device nodes */
        u_int64_t ctime;
        u_int64_t parent_obj_id;/* parent directory obj_id */
        uuid_t  uid;
        uuid_t  gid;
        /* XXX device, softlink extension */
};

#define HAMMER_INODE_DATA_VERSION       1

#define HAMMER_OBJID_ROOT               1

/*
 * Rollup various structures embedded as record data
 */
union hammer_data_ondisk {
        struct hammer_inode_data inode;
};

#endif