xfs_dir2_format.h

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/*
 * Copyright (c) 2000-2001,2005 Silicon Graphics, Inc.
 * All Rights Reserved.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License as
 * published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it would be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write the Free Software Foundation,
 * Inc.,  51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 */
#ifndef __XFS_DIR2_FORMAT_H__
#define __XFS_DIR2_FORMAT_H__

/*
 * Directory version 2.
 *
 * There are 4 possible formats:
 *  - shortform - embedded into the inode
 *  - single block - data with embedded leaf at the end
 *  - multiple data blocks, single leaf+freeindex block
 *  - data blocks, node and leaf blocks (btree), freeindex blocks
 *
 * Note: many node blocks structures and constants are shared with the attr
 * code and defined in xfs_da_btree.h.
 */

#define XFS_DIR2_BLOCK_MAGIC    0x58443242  /* XD2B: single block dirs */
#define XFS_DIR2_DATA_MAGIC 0x58443244  /* XD2D: multiblock dirs */
#define XFS_DIR2_FREE_MAGIC 0x58443246  /* XD2F: free index blocks */

/*
 * Byte offset in data block and shortform entry.
 */
typedef __uint16_t  xfs_dir2_data_off_t;
#define NULLDATAOFF 0xffffU
typedef uint        xfs_dir2_data_aoff_t;   /* argument form */

/*
 * Normalized offset (in a data block) of the entry, really xfs_dir2_data_off_t.
 * Only need 16 bits, this is the byte offset into the single block form.
 */
typedef struct { __uint8_t i[2]; } __arch_pack xfs_dir2_sf_off_t;

/*
 * Offset in data space of a data entry.
 */
typedef __uint32_t  xfs_dir2_dataptr_t;
#define XFS_DIR2_MAX_DATAPTR    ((xfs_dir2_dataptr_t)0xffffffff)
#define XFS_DIR2_NULL_DATAPTR   ((xfs_dir2_dataptr_t)0)

/*
 * Byte offset in a directory.
 */
typedef xfs_off_t   xfs_dir2_off_t;

/*
 * Directory block number (logical dirblk in file)
 */
typedef __uint32_t  xfs_dir2_db_t;

/*
 * Inode number stored as 8 8-bit values.
 */
typedef struct { __uint8_t i[8]; } xfs_dir2_ino8_t;

/*
 * Inode number stored as 4 8-bit values.
 * Works a lot of the time, when all the inode numbers in a directory
 * fit in 32 bits.
 */
typedef struct { __uint8_t i[4]; } xfs_dir2_ino4_t;

typedef union {
    xfs_dir2_ino8_t i8;
    xfs_dir2_ino4_t i4;
} xfs_dir2_inou_t;
#define XFS_DIR2_MAX_SHORT_INUM ((xfs_ino_t)0xffffffffULL)

/*
 * Directory layout when stored internal to an inode.
 *
 * Small directories are packed as tightly as possible so as to fit into the
 * literal area of the inode.  These "shortform" directories consist of a
 * single xfs_dir2_sf_hdr header followed by zero or more xfs_dir2_sf_entry
 * structures.  Due the different inode number storage size and the variable
 * length name field in the xfs_dir2_sf_entry all these structure are
 * variable length, and the accessors in this file should be used to iterate
 * over them.
 */
typedef struct xfs_dir2_sf_hdr {
    __uint8_t       count;      /* count of entries */
    __uint8_t       i8count;    /* count of 8-byte inode #s */
    xfs_dir2_inou_t     parent;     /* parent dir inode number */
} __arch_pack xfs_dir2_sf_hdr_t;

typedef struct xfs_dir2_sf_entry {
    __u8            namelen;    /* actual name length */
    xfs_dir2_sf_off_t   offset;     /* saved offset */
    __u8            name[];     /* name, variable size */
    /*
     * A xfs_dir2_ino8_t or xfs_dir2_ino4_t follows here, at a
     * variable offset after the name.
     */
} __arch_pack xfs_dir2_sf_entry_t;

static inline int xfs_dir2_sf_hdr_size(int i8count)
{
    return sizeof(struct xfs_dir2_sf_hdr) -
        (i8count == 0) *
        (sizeof(xfs_dir2_ino8_t) - sizeof(xfs_dir2_ino4_t));
}

static inline xfs_dir2_data_aoff_t
xfs_dir2_sf_get_offset(xfs_dir2_sf_entry_t *sfep)
{
    return get_unaligned_be16(&sfep->offset.i);
}

static inline void
xfs_dir2_sf_put_offset(xfs_dir2_sf_entry_t *sfep, xfs_dir2_data_aoff_t off)
{
    put_unaligned_be16(off, &sfep->offset.i);
}

static inline int
xfs_dir2_sf_entsize(struct xfs_dir2_sf_hdr *hdr, int len)
{
    return sizeof(struct xfs_dir2_sf_entry) +   /* namelen + offset */
        len +                   /* name */
        (hdr->i8count ?             /* ino */
         sizeof(xfs_dir2_ino8_t) :
         sizeof(xfs_dir2_ino4_t));
}

static inline struct xfs_dir2_sf_entry *
xfs_dir2_sf_firstentry(struct xfs_dir2_sf_hdr *hdr)
{
    return (struct xfs_dir2_sf_entry *)
        ((char *)hdr + xfs_dir2_sf_hdr_size(hdr->i8count));
}

static inline struct xfs_dir2_sf_entry *
xfs_dir2_sf_nextentry(struct xfs_dir2_sf_hdr *hdr,
        struct xfs_dir2_sf_entry *sfep)
{
    return (struct xfs_dir2_sf_entry *)
        ((char *)sfep + xfs_dir2_sf_entsize(hdr, sfep->namelen));
}


/*
 * Data block structures.
 *
 * A pure data block looks like the following drawing on disk:
 *
 *    +-------------------------------------------------+
 *    | xfs_dir2_data_hdr_t                             |
 *    +-------------------------------------------------+
 *    | xfs_dir2_data_entry_t OR xfs_dir2_data_unused_t |
 *    | xfs_dir2_data_entry_t OR xfs_dir2_data_unused_t |
 *    | xfs_dir2_data_entry_t OR xfs_dir2_data_unused_t |
 *    | ...                                             |
 *    +-------------------------------------------------+
 *    | unused space                                    |
 *    +-------------------------------------------------+
 *
 * As all the entries are variable size structures the accessors below should
 * be used to iterate over them.
 *
 * In addition to the pure data blocks for the data and node formats,
 * most structures are also used for the combined data/freespace "block"
 * format below.
 */

#define XFS_DIR2_DATA_ALIGN_LOG 3       /* i.e., 8 bytes */
#define XFS_DIR2_DATA_ALIGN (1 << XFS_DIR2_DATA_ALIGN_LOG)
#define XFS_DIR2_DATA_FREE_TAG  0xffff
#define XFS_DIR2_DATA_FD_COUNT  3

/*
 * Directory address space divided into sections,
 * spaces separated by 32GB.
 */
#define XFS_DIR2_SPACE_SIZE (1ULL << (32 + XFS_DIR2_DATA_ALIGN_LOG))
#define XFS_DIR2_DATA_SPACE 0
#define XFS_DIR2_DATA_OFFSET    (XFS_DIR2_DATA_SPACE * XFS_DIR2_SPACE_SIZE)
#define XFS_DIR2_DATA_FIRSTDB(mp)   \
    xfs_dir2_byte_to_db(mp, XFS_DIR2_DATA_OFFSET)

/*
 * Offsets of . and .. in data space (always block 0)
 */
#define XFS_DIR2_DATA_DOT_OFFSET    \
    ((xfs_dir2_data_aoff_t)sizeof(struct xfs_dir2_data_hdr))
#define XFS_DIR2_DATA_DOTDOT_OFFSET \
    (XFS_DIR2_DATA_DOT_OFFSET + xfs_dir2_data_entsize(1))
#define XFS_DIR2_DATA_FIRST_OFFSET      \
    (XFS_DIR2_DATA_DOTDOT_OFFSET + xfs_dir2_data_entsize(2))

/*
 * Describe a free area in the data block.
 *
 * The freespace will be formatted as a xfs_dir2_data_unused_t.
 */
typedef struct xfs_dir2_data_free {
    __be16          offset;     /* start of freespace */
    __be16          length;     /* length of freespace */
} xfs_dir2_data_free_t;

/*
 * Header for the data blocks.
 *
 * The code knows that XFS_DIR2_DATA_FD_COUNT is 3.
 */
typedef struct xfs_dir2_data_hdr {
    __be32          magic;      /* XFS_DIR2_DATA_MAGIC or */
                        /* XFS_DIR2_BLOCK_MAGIC */
    xfs_dir2_data_free_t    bestfree[XFS_DIR2_DATA_FD_COUNT];
} xfs_dir2_data_hdr_t;

/*
 * Active entry in a data block.
 *
 * Aligned to 8 bytes.  After the variable length name field there is a
 * 2 byte tag field, which can be accessed using xfs_dir2_data_entry_tag_p.
 */
typedef struct xfs_dir2_data_entry {
    __be64          inumber;    /* inode number */
    __u8            namelen;    /* name length */
    __u8            name[];     /* name bytes, no null */
     /* __be16                  tag; */     /* starting offset of us */
} xfs_dir2_data_entry_t;

/*
 * Unused entry in a data block.
 *
 * Aligned to 8 bytes.  Tag appears as the last 2 bytes and must be accessed
 * using xfs_dir2_data_unused_tag_p.
 */
typedef struct xfs_dir2_data_unused {
    __be16          freetag;    /* XFS_DIR2_DATA_FREE_TAG */
    __be16          length;     /* total free length */
                        /* variable offset */
    __be16          tag;        /* starting offset of us */
} xfs_dir2_data_unused_t;

/*
 * Size of a data entry.
 */
static inline int xfs_dir2_data_entsize(int n)
{
    return (int)roundup(offsetof(struct xfs_dir2_data_entry, name[0]) + n +
         (uint)sizeof(xfs_dir2_data_off_t), XFS_DIR2_DATA_ALIGN);
}

/*
 * Pointer to an entry's tag word.
 */
static inline __be16 *
xfs_dir2_data_entry_tag_p(struct xfs_dir2_data_entry *dep)
{
    return (__be16 *)((char *)dep +
        xfs_dir2_data_entsize(dep->namelen) - sizeof(__be16));
}

/*
 * Pointer to a freespace's tag word.
 */
static inline __be16 *
xfs_dir2_data_unused_tag_p(struct xfs_dir2_data_unused *dup)
{
    return (__be16 *)((char *)dup +
            be16_to_cpu(dup->length) - sizeof(__be16));
}

/*
 * Leaf block structures.
 *
 * A pure leaf block looks like the following drawing on disk:
 *
 *    +---------------------------+
 *    | xfs_dir2_leaf_hdr_t       |
 *    +---------------------------+
 *    | xfs_dir2_leaf_entry_t     |
 *    | xfs_dir2_leaf_entry_t     |
 *    | xfs_dir2_leaf_entry_t     |
 *    | xfs_dir2_leaf_entry_t     |
 *    | ...                       |
 *    +---------------------------+
 *    | xfs_dir2_data_off_t       |
 *    | xfs_dir2_data_off_t       |
 *    | xfs_dir2_data_off_t       |
 *    | ...                       |
 *    +---------------------------+
 *    | xfs_dir2_leaf_tail_t      |
 *    +---------------------------+
 *
 * The xfs_dir2_data_off_t members (bests) and tail are at the end of the block
 * for single-leaf (magic = XFS_DIR2_LEAF1_MAGIC) blocks only, but not present
 * for directories with separate leaf nodes and free space blocks
 * (magic = XFS_DIR2_LEAFN_MAGIC).
 *
 * As all the entries are variable size structures the accessors below should
 * be used to iterate over them.
 */

/*
 * Offset of the leaf/node space.  First block in this space
 * is the btree root.
 */
#define XFS_DIR2_LEAF_SPACE 1
#define XFS_DIR2_LEAF_OFFSET    (XFS_DIR2_LEAF_SPACE * XFS_DIR2_SPACE_SIZE)
#define XFS_DIR2_LEAF_FIRSTDB(mp)   \
    xfs_dir2_byte_to_db(mp, XFS_DIR2_LEAF_OFFSET)

/*
 * Leaf block header.
 */
typedef struct xfs_dir2_leaf_hdr {
    xfs_da_blkinfo_t    info;       /* header for da routines */
    __be16          count;      /* count of entries */
    __be16          stale;      /* count of stale entries */
} xfs_dir2_leaf_hdr_t;

/*
 * Leaf block entry.
 */
typedef struct xfs_dir2_leaf_entry {
    __be32          hashval;    /* hash value of name */
    __be32          address;    /* address of data entry */
} xfs_dir2_leaf_entry_t;

/*
 * Leaf block tail.
 */
typedef struct xfs_dir2_leaf_tail {
    __be32          bestcount;
} xfs_dir2_leaf_tail_t;

/*
 * Leaf block.
 */
typedef struct xfs_dir2_leaf {
    xfs_dir2_leaf_hdr_t hdr;        /* leaf header */
    xfs_dir2_leaf_entry_t   ents[];     /* entries */
} xfs_dir2_leaf_t;

/*
 * DB blocks here are logical directory block numbers, not filesystem blocks.
 */

static inline int xfs_dir2_max_leaf_ents(struct xfs_mount *mp)
{
    return (mp->m_dirblksize - (uint)sizeof(struct xfs_dir2_leaf_hdr)) /
        (uint)sizeof(struct xfs_dir2_leaf_entry);
}

/*
 * Get address of the bestcount field in the single-leaf block.
 */
static inline struct xfs_dir2_leaf_tail *
xfs_dir2_leaf_tail_p(struct xfs_mount *mp, struct xfs_dir2_leaf *lp)
{
    return (struct xfs_dir2_leaf_tail *)
        ((char *)lp + mp->m_dirblksize -
          sizeof(struct xfs_dir2_leaf_tail));
}

/*
 * Get address of the bests array in the single-leaf block.
 */
static inline __be16 *
xfs_dir2_leaf_bests_p(struct xfs_dir2_leaf_tail *ltp)
{
    return (__be16 *)ltp - be32_to_cpu(ltp->bestcount);
}

/*
 * Convert dataptr to byte in file space
 */
static inline xfs_dir2_off_t
xfs_dir2_dataptr_to_byte(struct xfs_mount *mp, xfs_dir2_dataptr_t dp)
{
    return (xfs_dir2_off_t)dp << XFS_DIR2_DATA_ALIGN_LOG;
}

/*
 * Convert byte in file space to dataptr.  It had better be aligned.
 */
static inline xfs_dir2_dataptr_t
xfs_dir2_byte_to_dataptr(struct xfs_mount *mp, xfs_dir2_off_t by)
{
    return (xfs_dir2_dataptr_t)(by >> XFS_DIR2_DATA_ALIGN_LOG);
}

/*
 * Convert byte in space to (DB) block
 */
static inline xfs_dir2_db_t
xfs_dir2_byte_to_db(struct xfs_mount *mp, xfs_dir2_off_t by)
{
    return (xfs_dir2_db_t)
        (by >> (mp->m_sb.sb_blocklog + mp->m_sb.sb_dirblklog));
}

/*
 * Convert dataptr to a block number
 */
static inline xfs_dir2_db_t
xfs_dir2_dataptr_to_db(struct xfs_mount *mp, xfs_dir2_dataptr_t dp)
{
    return xfs_dir2_byte_to_db(mp, xfs_dir2_dataptr_to_byte(mp, dp));
}

/*
 * Convert byte in space to offset in a block
 */
static inline xfs_dir2_data_aoff_t
xfs_dir2_byte_to_off(struct xfs_mount *mp, xfs_dir2_off_t by)
{
    return (xfs_dir2_data_aoff_t)(by &
        ((1 << (mp->m_sb.sb_blocklog + mp->m_sb.sb_dirblklog)) - 1));
}

/*
 * Convert dataptr to a byte offset in a block
 */
static inline xfs_dir2_data_aoff_t
xfs_dir2_dataptr_to_off(struct xfs_mount *mp, xfs_dir2_dataptr_t dp)
{
    return xfs_dir2_byte_to_off(mp, xfs_dir2_dataptr_to_byte(mp, dp));
}

/*
 * Convert block and offset to byte in space
 */
static inline xfs_dir2_off_t
xfs_dir2_db_off_to_byte(struct xfs_mount *mp, xfs_dir2_db_t db,
            xfs_dir2_data_aoff_t o)
{
    return ((xfs_dir2_off_t)db <<
        (mp->m_sb.sb_blocklog + mp->m_sb.sb_dirblklog)) + o;
}

/*
 * Convert block (DB) to block (dablk)
 */
static inline xfs_dablk_t
xfs_dir2_db_to_da(struct xfs_mount *mp, xfs_dir2_db_t db)
{
    return (xfs_dablk_t)(db << mp->m_sb.sb_dirblklog);
}

/*
 * Convert byte in space to (DA) block
 */
static inline xfs_dablk_t
xfs_dir2_byte_to_da(struct xfs_mount *mp, xfs_dir2_off_t by)
{
    return xfs_dir2_db_to_da(mp, xfs_dir2_byte_to_db(mp, by));
}

/*
 * Convert block and offset to dataptr
 */
static inline xfs_dir2_dataptr_t
xfs_dir2_db_off_to_dataptr(struct xfs_mount *mp, xfs_dir2_db_t db,
               xfs_dir2_data_aoff_t o)
{
    return xfs_dir2_byte_to_dataptr(mp, xfs_dir2_db_off_to_byte(mp, db, o));
}

/*
 * Convert block (dablk) to block (DB)
 */
static inline xfs_dir2_db_t
xfs_dir2_da_to_db(struct xfs_mount *mp, xfs_dablk_t da)
{
    return (xfs_dir2_db_t)(da >> mp->m_sb.sb_dirblklog);
}

/*
 * Convert block (dablk) to byte offset in space
 */
static inline xfs_dir2_off_t
xfs_dir2_da_to_byte(struct xfs_mount *mp, xfs_dablk_t da)
{
    return xfs_dir2_db_off_to_byte(mp, xfs_dir2_da_to_db(mp, da), 0);
}

/*
 * Free space block defintions for the node format.
 */

/*
 * Offset of the freespace index.
 */
#define XFS_DIR2_FREE_SPACE 2
#define XFS_DIR2_FREE_OFFSET    (XFS_DIR2_FREE_SPACE * XFS_DIR2_SPACE_SIZE)
#define XFS_DIR2_FREE_FIRSTDB(mp)   \
    xfs_dir2_byte_to_db(mp, XFS_DIR2_FREE_OFFSET)

typedef struct xfs_dir2_free_hdr {
    __be32          magic;      /* XFS_DIR2_FREE_MAGIC */
    __be32          firstdb;    /* db of first entry */
    __be32          nvalid;     /* count of valid entries */
    __be32          nused;      /* count of used entries */
} xfs_dir2_free_hdr_t;

typedef struct xfs_dir2_free {
    xfs_dir2_free_hdr_t hdr;        /* block header */
    __be16          bests[];    /* best free counts */
                        /* unused entries are -1 */
} xfs_dir2_free_t;

static inline int xfs_dir2_free_max_bests(struct xfs_mount *mp)
{
    return (mp->m_dirblksize - sizeof(struct xfs_dir2_free_hdr)) /
        sizeof(xfs_dir2_data_off_t);
}

/*
 * Convert data space db to the corresponding free db.
 */
static inline xfs_dir2_db_t
xfs_dir2_db_to_fdb(struct xfs_mount *mp, xfs_dir2_db_t db)
{
    return XFS_DIR2_FREE_FIRSTDB(mp) + db / xfs_dir2_free_max_bests(mp);
}

/*
 * Convert data space db to the corresponding index in a free db.
 */
static inline int
xfs_dir2_db_to_fdindex(struct xfs_mount *mp, xfs_dir2_db_t db)
{
    return db % xfs_dir2_free_max_bests(mp);
}

/*
 * Single block format.
 *
 * The single block format looks like the following drawing on disk:
 *
 *    +-------------------------------------------------+
 *    | xfs_dir2_data_hdr_t                             |
 *    +-------------------------------------------------+
 *    | xfs_dir2_data_entry_t OR xfs_dir2_data_unused_t |
 *    | xfs_dir2_data_entry_t OR xfs_dir2_data_unused_t |
 *    | xfs_dir2_data_entry_t OR xfs_dir2_data_unused_t :
 *    | ...                                             |
 *    +-------------------------------------------------+
 *    | unused space                                    |
 *    +-------------------------------------------------+
 *    | ...                                             |
 *    | xfs_dir2_leaf_entry_t                           |
 *    | xfs_dir2_leaf_entry_t                           |
 *    +-------------------------------------------------+
 *    | xfs_dir2_block_tail_t                           |
 *    +-------------------------------------------------+
 *
 * As all the entries are variable size structures the accessors below should
 * be used to iterate over them.
 */

typedef struct xfs_dir2_block_tail {
    __be32      count;          /* count of leaf entries */
    __be32      stale;          /* count of stale lf entries */
} xfs_dir2_block_tail_t;

/*
 * Pointer to the leaf header embedded in a data block (1-block format)
 */
static inline struct xfs_dir2_block_tail *
xfs_dir2_block_tail_p(struct xfs_mount *mp, struct xfs_dir2_data_hdr *hdr)
{
    return ((struct xfs_dir2_block_tail *)
        ((char *)hdr + mp->m_dirblksize)) - 1;
}

/*
 * Pointer to the leaf entries embedded in a data block (1-block format)
 */
static inline struct xfs_dir2_leaf_entry *
xfs_dir2_block_leaf_p(struct xfs_dir2_block_tail *btp)
{
    return ((struct xfs_dir2_leaf_entry *)btp) - be32_to_cpu(btp->count);
}

#endif /* __XFS_DIR2_FORMAT_H__ */