[safe/jmp/linux-2.6] / fs / logfs / logfs_abi.h

/*
 * fs/logfs/logfs_abi.h
 *
 * As should be obvious for Linux kernel code, license is GPLv2
 *
 * Copyright (c) 2005-2008 Joern Engel <joern@logfs.org>
 *
 * Public header for logfs.
 */
#ifndef FS_LOGFS_LOGFS_ABI_H
#define FS_LOGFS_LOGFS_ABI_H

/* For out-of-kernel compiles */
#ifndef BUILD_BUG_ON
#define BUILD_BUG_ON(condition) /**/
#endif

#define SIZE_CHECK(type, size)                                  \
static inline void check_##type(void)                           \
{                                                               \
        BUILD_BUG_ON(sizeof(struct type) != (size));            \
}

/*
 * Throughout the logfs code, we're constantly dealing with blocks at
 * various positions or offsets.  To remove confusion, we stricly
 * distinguish between a "position" - the logical position within a
 * file and an "offset" - the physical location within the device.
 *
 * Any usage of the term offset for a logical location or position for
 * a physical one is a bug and should get fixed.
 */

/*
 * Block are allocated in one of several segments depending on their
 * level.  The following levels are used:
 *  0   - regular data block
 *  1   - i1 indirect blocks
 *  2   - i2 indirect blocks
 *  3   - i3 indirect blocks
 *  4   - i4 indirect blocks
 *  5   - i5 indirect blocks
 *  6   - ifile data blocks
 *  7   - ifile i1 indirect blocks
 *  8   - ifile i2 indirect blocks
 *  9   - ifile i3 indirect blocks
 * 10   - ifile i4 indirect blocks
 * 11   - ifile i5 indirect blocks
 * Potential levels to be used in the future:
 * 12   - gc recycled blocks, long-lived data
 * 13   - replacement blocks, short-lived data
 *
 * Levels 1-11 are necessary for robust gc operations and help seperate
 * short-lived metadata from longer-lived file data.  In the future,
 * file data should get seperated into several segments based on simple
 * heuristics.  Old data recycled during gc operation is expected to be
 * long-lived.  New data is of uncertain life expectancy.  New data
 * used to replace older blocks in existing files is expected to be
 * short-lived.
 */


/* Magic numbers.  64bit for superblock, 32bit for statfs f_type */
#define LOGFS_MAGIC             0xb21f205ac97e8168ull
#define LOGFS_MAGIC_U32         0xc97e8168u

/*
 * Various blocksize related macros.  Blocksize is currently fixed at 4KiB.
 * Sooner or later that should become configurable and the macros replaced
 * by something superblock-dependent.  Pointers in indirect blocks are and
 * will remain 64bit.
 *
 * LOGFS_BLOCKSIZE      - self-explaining
 * LOGFS_BLOCK_FACTOR   - number of pointers per indirect block
 * LOGFS_BLOCK_BITS     - log2 of LOGFS_BLOCK_FACTOR, used for shifts
 */
#define LOGFS_BLOCKSIZE         (4096ull)
#define LOGFS_BLOCK_FACTOR      (LOGFS_BLOCKSIZE / sizeof(u64))
#define LOGFS_BLOCK_BITS        (9)

/*
 * Number of blocks at various levels of indirection.  There are 16 direct
 * block pointers plus a single indirect pointer.
 */
#define I0_BLOCKS               (16)
#define I1_BLOCKS               LOGFS_BLOCK_FACTOR
#define I2_BLOCKS               (LOGFS_BLOCK_FACTOR * I1_BLOCKS)
#define I3_BLOCKS               (LOGFS_BLOCK_FACTOR * I2_BLOCKS)
#define I4_BLOCKS               (LOGFS_BLOCK_FACTOR * I3_BLOCKS)
#define I5_BLOCKS               (LOGFS_BLOCK_FACTOR * I4_BLOCKS)

#define INDIRECT_INDEX          I0_BLOCKS
#define LOGFS_EMBEDDED_FIELDS   (I0_BLOCKS + 1)

/*
 * Sizes at which files require another level of indirection.  Files smaller
 * than LOGFS_EMBEDDED_SIZE can be completely stored in the inode itself,
 * similar like ext2 fast symlinks.
 *
 * Data at a position smaller than LOGFS_I0_SIZE is accessed through the
 * direct pointers, else through the 1x indirect pointer and so forth.
 */
#define LOGFS_EMBEDDED_SIZE     (LOGFS_EMBEDDED_FIELDS * sizeof(u64))
#define LOGFS_I0_SIZE           (I0_BLOCKS * LOGFS_BLOCKSIZE)
#define LOGFS_I1_SIZE           (I1_BLOCKS * LOGFS_BLOCKSIZE)
#define LOGFS_I2_SIZE           (I2_BLOCKS * LOGFS_BLOCKSIZE)
#define LOGFS_I3_SIZE           (I3_BLOCKS * LOGFS_BLOCKSIZE)
#define LOGFS_I4_SIZE           (I4_BLOCKS * LOGFS_BLOCKSIZE)
#define LOGFS_I5_SIZE           (I5_BLOCKS * LOGFS_BLOCKSIZE)

/*
 * Each indirect block pointer must have this flag set, if all block pointers
 * behind it are set, i.e. there is no hole hidden in the shadow of this
 * indirect block pointer.
 */
#define LOGFS_FULLY_POPULATED (1ULL << 63)
#define pure_ofs(ofs) (ofs & ~LOGFS_FULLY_POPULATED)

/*
 * LogFS needs to seperate data into levels.  Each level is defined as the
 * maximal possible distance from the master inode (inode of the inode file).
 * Data blocks reside on level 0, 1x indirect block on level 1, etc.
 * Inodes reside on level 6, indirect blocks for the inode file on levels 7-11.
 * This effort is necessary to guarantee garbage collection to always make
 * progress.
 *
 * LOGFS_MAX_INDIRECT is the maximal indirection through indirect blocks,
 * LOGFS_MAX_LEVELS is one more for the actual data level of a file.  It is
 * the maximal number of levels for one file.
 * LOGFS_NO_AREAS is twice that, as the inode file and regular files are
 * effectively stacked on top of each other.
 */
#define LOGFS_MAX_INDIRECT      (5)
#define LOGFS_MAX_LEVELS        (LOGFS_MAX_INDIRECT + 1)
#define LOGFS_NO_AREAS          (2 * LOGFS_MAX_LEVELS)

/* Maximum size of filenames */
#define LOGFS_MAX_NAMELEN       (255)

/* Number of segments in the primary journal. */
#define LOGFS_JOURNAL_SEGS      (16)

/* Maximum number of free/erased/etc. segments in journal entries */
#define MAX_CACHED_SEGS         (64)


/*
 * LOGFS_OBJECT_HEADERSIZE is the size of a single header in the object store,
 * LOGFS_MAX_OBJECTSIZE the size of the largest possible object, including
 * its header,
 * LOGFS_SEGMENT_RESERVE is the amount of space reserved for each segment for
 * its segment header and the padded space at the end when no further objects
 * fit.
 */
#define LOGFS_OBJECT_HEADERSIZE (0x1c)
#define LOGFS_SEGMENT_HEADERSIZE (0x18)
#define LOGFS_MAX_OBJECTSIZE    (LOGFS_OBJECT_HEADERSIZE + LOGFS_BLOCKSIZE)
#define LOGFS_SEGMENT_RESERVE   \
        (LOGFS_SEGMENT_HEADERSIZE + LOGFS_MAX_OBJECTSIZE - 1)

/*
 * Segment types:
 * SEG_SUPER    - Data or indirect block
 * SEG_JOURNAL  - Inode
 * SEG_OSTORE   - Dentry
 */
enum {
        SEG_SUPER       = 0x01,
        SEG_JOURNAL     = 0x02,
        SEG_OSTORE      = 0x03,
};

/**
 * struct logfs_segment_header - per-segment header in the ostore
 *
 * @crc:                        crc32 of header (there is no data)
 * @pad:                        unused, must be 0
 * @type:                       segment type, see above
 * @level:                      GC level for all objects in this segment
 * @segno:                      segment number
 * @ec:                         erase count for this segment
 * @gec:                        global erase count at time of writing
 */
struct logfs_segment_header {
        __be32  crc;
        __be16  pad;
        __u8    type;
        __u8    level;
        __be32  segno;
        __be32  ec;
        __be64  gec;
};

SIZE_CHECK(logfs_segment_header, LOGFS_SEGMENT_HEADERSIZE);

/**
 * struct logfs_disk_super - on-medium superblock
 *
 * @ds_magic:                   magic number, must equal LOGFS_MAGIC
 * @ds_crc:                     crc32 of structure starting with the next field
 * @ds_ifile_levels:            maximum number of levels for ifile
 * @ds_iblock_levels:           maximum number of levels for regular files
 * @ds_data_levels:             number of seperate levels for data
 * @pad0:                       reserved, must be 0
 * @ds_feature_incompat:        incompatible filesystem features
 * @ds_feature_ro_compat:       read-only compatible filesystem features
 * @ds_feature_compat:          compatible filesystem features
 * @ds_flags:                   flags
 * @ds_segment_shift:           log2 of segment size
 * @ds_block_shift:             log2 of block size
 * @ds_write_shift:             log2 of write size
 * @pad1:                       reserved, must be 0
 * @ds_journal_seg:             segments used by primary journal
 * @ds_root_reserve:            bytes reserved for the superuser
 * @ds_speed_reserve:           bytes reserved to speed up GC
 * @ds_bad_seg_reserve:         number of segments reserved to handle bad blocks
 * @pad2:                       reserved, must be 0
 * @pad3:                       reserved, must be 0
 *
 * Contains only read-only fields.  Read-write fields like the amount of used
 * space is tracked in the dynamic superblock, which is stored in the journal.
 */
struct logfs_disk_super {
        struct logfs_segment_header ds_sh;
        __be64  ds_magic;

        __be32  ds_crc;
        __u8    ds_ifile_levels;
        __u8    ds_iblock_levels;
        __u8    ds_data_levels;
        __u8    ds_segment_shift;
        __u8    ds_block_shift;
        __u8    ds_write_shift;
        __u8    pad0[6];

        __be64  ds_filesystem_size;
        __be32  ds_segment_size;
        __be32  ds_bad_seg_reserve;

        __be64  ds_feature_incompat;
        __be64  ds_feature_ro_compat;

        __be64  ds_feature_compat;
        __be64  ds_feature_flags;

        __be64  ds_root_reserve;
        __be64  ds_speed_reserve;

        __be32  ds_journal_seg[LOGFS_JOURNAL_SEGS];

        __be64  ds_super_ofs[2];
        __be64  pad3[8];
};

SIZE_CHECK(logfs_disk_super, 256);

/*
 * Object types:
 * OBJ_BLOCK    - Data or indirect block
 * OBJ_INODE    - Inode
 * OBJ_DENTRY   - Dentry
 */
enum {
        OBJ_BLOCK       = 0x04,
        OBJ_INODE       = 0x05,
        OBJ_DENTRY      = 0x06,
};

/**
 * struct logfs_object_header - per-object header in the ostore
 *
 * @crc:                        crc32 of header, excluding data_crc
 * @len:                        length of data
 * @type:                       object type, see above
 * @compr:                      compression type
 * @ino:                        inode number
 * @bix:                        block index
 * @data_crc:                   crc32 of payload
 */
struct logfs_object_header {
        __be32  crc;
        __be16  len;
        __u8    type;
        __u8    compr;
        __be64  ino;
        __be64  bix;
        __be32  data_crc;
} __attribute__((packed));

SIZE_CHECK(logfs_object_header, LOGFS_OBJECT_HEADERSIZE);

/*
 * Reserved inode numbers:
 * LOGFS_INO_MASTER     - master inode (for inode file)
 * LOGFS_INO_ROOT       - root directory
 * LOGFS_INO_SEGFILE    - per-segment used bytes and erase count
 */
enum {
        LOGFS_INO_MAPPING       = 0x00,
        LOGFS_INO_MASTER        = 0x01,
        LOGFS_INO_ROOT          = 0x02,
        LOGFS_INO_SEGFILE       = 0x03,
        LOGFS_RESERVED_INOS     = 0x10,
};

/*
 * Inode flags.  High bits should never be written to the medium.  They are
 * reserved for in-memory usage.
 * Low bits should either remain in sync with the corresponding FS_*_FL or
 * reuse slots that obviously don't make sense for logfs.
 *
 * LOGFS_IF_DIRTY       Inode must be written back
 * LOGFS_IF_ZOMBIE      Inode has been deleted
 * LOGFS_IF_STILLBORN   -ENOSPC happened when creating inode
 */
#define LOGFS_IF_COMPRESSED     0x00000004 /* == FS_COMPR_FL */
#define LOGFS_IF_DIRTY          0x20000000
#define LOGFS_IF_ZOMBIE         0x40000000
#define LOGFS_IF_STILLBORN      0x80000000

/* Flags available to chattr */
#define LOGFS_FL_USER_VISIBLE   (LOGFS_IF_COMPRESSED)
#define LOGFS_FL_USER_MODIFIABLE (LOGFS_IF_COMPRESSED)
/* Flags inherited from parent directory on file/directory creation */
#define LOGFS_FL_INHERITED      (LOGFS_IF_COMPRESSED)

/**
 * struct logfs_disk_inode - on-medium inode
 *
 * @di_mode:                    file mode
 * @di_pad:                     reserved, must be 0
 * @di_flags:                   inode flags, see above
 * @di_uid:                     user id
 * @di_gid:                     group id
 * @di_ctime:                   change time
 * @di_mtime:                   modify time
 * @di_refcount:                reference count (aka nlink or link count)
 * @di_generation:              inode generation, for nfs
 * @di_used_bytes:              number of bytes used
 * @di_size:                    file size
 * @di_data:                    data pointers
 */
struct logfs_disk_inode {
        __be16  di_mode;
        __u8    di_height;
        __u8    di_pad;
        __be32  di_flags;
        __be32  di_uid;
        __be32  di_gid;

        __be64  di_ctime;
        __be64  di_mtime;

        __be64  di_atime;
        __be32  di_refcount;
        __be32  di_generation;

        __be64  di_used_bytes;
        __be64  di_size;

        __be64  di_data[LOGFS_EMBEDDED_FIELDS];
};

SIZE_CHECK(logfs_disk_inode, 200);

#define INODE_POINTER_OFS \
        (offsetof(struct logfs_disk_inode, di_data) / sizeof(__be64))
#define INODE_USED_OFS \
        (offsetof(struct logfs_disk_inode, di_used_bytes) / sizeof(__be64))
#define INODE_SIZE_OFS \
        (offsetof(struct logfs_disk_inode, di_size) / sizeof(__be64))
#define INODE_HEIGHT_OFS        (0)

/**
 * struct logfs_disk_dentry - on-medium dentry structure
 *
 * @ino:                        inode number
 * @namelen:                    length of file name
 * @type:                       file type, identical to bits 12..15 of mode
 * @name:                       file name
 */
/* FIXME: add 6 bytes of padding to remove the __packed */
struct logfs_disk_dentry {
        __be64  ino;
        __be16  namelen;
        __u8    type;
        __u8    name[LOGFS_MAX_NAMELEN];
} __attribute__((packed));

SIZE_CHECK(logfs_disk_dentry, 266);

#define RESERVED                0xffffffff
#define BADSEG                  0xffffffff
/**
 * struct logfs_segment_entry - segment file entry
 *
 * @ec_level:                   erase count and level
 * @valid:                      number of valid bytes
 *
 * Segment file contains one entry for every segment.  ec_level contains the
 * erasecount in the upper 28 bits and the level in the lower 4 bits.  An
 * ec_level of BADSEG (-1) identifies bad segments.  valid contains the number
 * of valid bytes or RESERVED (-1 again) if the segment is used for either the
 * superblock or the journal, or when the segment is bad.
 */
struct logfs_segment_entry {
        __be32  ec_level;
        __be32  valid;
};

SIZE_CHECK(logfs_segment_entry, 8);

/**
 * struct logfs_journal_header - header for journal entries (JEs)
 *
 * @h_crc:                      crc32 of journal entry
 * @h_len:                      length of compressed journal entry,
 *                              not including header
 * @h_datalen:                  length of uncompressed data
 * @h_type:                     JE type
 * @h_version:                  unnormalized version of journal entry
 * @h_compr:                    compression type
 * @h_pad:                      reserved
 */
struct logfs_journal_header {
        __be32  h_crc;
        __be16  h_len;
        __be16  h_datalen;
        __be16  h_type;
        __be16  h_version;
        __u8    h_compr;
        __u8    h_pad[3];
};

SIZE_CHECK(logfs_journal_header, 16);

/*
 * Life expectency of data.
 * VIM_DEFAULT          - default vim
 * VIM_SEGFILE          - for segment file only - very short-living
 * VIM_GC               - GC'd data - likely long-living
 */
enum logfs_vim {
        VIM_DEFAULT     = 0,
        VIM_SEGFILE     = 1,
};

/**
 * struct logfs_je_area - wbuf header
 *
 * @segno:                      segment number of area
 * @used_bytes:                 number of bytes already used
 * @gc_level:                   GC level
 * @vim:                        life expectancy of data
 *
 * "Areas" are segments currently being used for writing.  There is at least
 * one area per GC level.  Several may be used to seperate long-living from
 * short-living data.  If an area with unknown vim is encountered, it can
 * simply be closed.
 * The write buffer immediately follow this header.
 */
struct logfs_je_area {
        __be32  segno;
        __be32  used_bytes;
        __u8    gc_level;
        __u8    vim;
} __attribute__((packed));

SIZE_CHECK(logfs_je_area, 10);

#define MAX_JOURNAL_HEADER \
        (sizeof(struct logfs_journal_header) + sizeof(struct logfs_je_area))

/**
 * struct logfs_je_dynsb - dynamic superblock
 *
 * @ds_gec:                     global erase count
 * @ds_sweeper:                 current position of GC "sweeper"
 * @ds_rename_dir:              source directory ino (see dir.c documentation)
 * @ds_rename_pos:              position of source dd (see dir.c documentation)
 * @ds_victim_ino:              victims of incomplete dir operation (see dir.c)
 * @ds_victim_ino:              parent inode of victim (see dir.c)
 * @ds_used_bytes:              number of used bytes
 */
struct logfs_je_dynsb {
        __be64  ds_gec;
        __be64  ds_sweeper;

        __be64  ds_rename_dir;
        __be64  ds_rename_pos;

        __be64  ds_victim_ino;
        __be64  ds_victim_parent; /* XXX */

        __be64  ds_used_bytes;
        __be32  ds_generation;
        __be32  pad;
};

SIZE_CHECK(logfs_je_dynsb, 64);

/**
 * struct logfs_je_anchor - anchor of filesystem tree, aka master inode
 *
 * @da_size:                    size of inode file
 * @da_last_ino:                last created inode
 * @da_used_bytes:              number of bytes used
 * @da_data:                    data pointers
 */
struct logfs_je_anchor {
        __be64  da_size;
        __be64  da_last_ino;

        __be64  da_used_bytes;
        u8      da_height;
        u8      pad[7];

        __be64  da_data[LOGFS_EMBEDDED_FIELDS];
};

SIZE_CHECK(logfs_je_anchor, 168);

/**
 * struct logfs_je_spillout - spillout entry (from 1st to 2nd journal)
 *
 * @so_segment:                 segments used for 2nd journal
 *
 * Length of the array is given by h_len field in the header.
 */
struct logfs_je_spillout {
        __be64  so_segment[0];
};

SIZE_CHECK(logfs_je_spillout, 0);

/**
 * struct logfs_je_journal_ec - erase counts for all journal segments
 *
 * @ec:                         erase count
 *
 * Length of the array is given by h_len field in the header.
 */
struct logfs_je_journal_ec {
        __be32  ec[0];
};

SIZE_CHECK(logfs_je_journal_ec, 0);

/**
 * struct logfs_je_free_segments - list of free segmetns with erase count
 */
struct logfs_je_free_segments {
        __be32  segno;
        __be32  ec;
};

SIZE_CHECK(logfs_je_free_segments, 8);

/**
 * struct logfs_seg_alias - list of segment aliases
 */
struct logfs_seg_alias {
        __be32  old_segno;
        __be32  new_segno;
};

SIZE_CHECK(logfs_seg_alias, 8);

/**
 * struct logfs_obj_alias - list of object aliases
 */
struct logfs_obj_alias {
        __be64  ino;
        __be64  bix;
        __be64  val;
        u8      level;
        u8      pad[5];
        __be16  child_no;
};

SIZE_CHECK(logfs_obj_alias, 32);

/**
 * Compression types.
 *
 * COMPR_NONE   - uncompressed
 * COMPR_ZLIB   - compressed with zlib
 */
enum {
        COMPR_NONE      = 0,
        COMPR_ZLIB      = 1,
};

/*
 * Journal entries come in groups of 16.  First group contains unique
 * entries, next groups contain one entry per level
 *
 * JE_FIRST     - smallest possible journal entry number
 *
 * JEG_BASE     - base group, containing unique entries
 * JE_COMMIT    - commit entry, validates all previous entries
 * JE_DYNSB     - dynamic superblock, anything that ought to be in the
 *                superblock but cannot because it is read-write data
 * JE_ANCHOR    - anchor aka master inode aka inode file's inode
 * JE_ERASECOUNT  erasecounts for all journal segments
 * JE_SPILLOUT  - unused
 * JE_SEG_ALIAS - aliases segments
 * JE_AREA      - area description
 *
 * JE_LAST      - largest possible journal entry number
 */
enum {
        JE_FIRST        = 0x01,

        JEG_BASE        = 0x00,
        JE_COMMIT       = 0x02,
        JE_DYNSB        = 0x03,
        JE_ANCHOR       = 0x04,
        JE_ERASECOUNT   = 0x05,
        JE_SPILLOUT     = 0x06,
        JE_OBJ_ALIAS    = 0x0d,
        JE_AREA         = 0x0e,

        JE_LAST         = 0x0e,
};

#endif