FreeBSD/Linux Kernel Cross Reference
sys/ufs/ffs/fs.h

     /*-
      * SPDX-License-Identifier: BSD-3-Clause
      *
      * Copyright (c) 1982, 1986, 1993
      *      The Regents of the University of California.  All rights reserved.
      *
      * 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 University 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 REGENTS 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 REGENTS 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.
     *
     *      @(#)fs.h        8.13 (Berkeley) 3/21/95
     * $FreeBSD: releng/12.0/sys/ufs/ffs/fs.h 329051 2018-02-08 23:06:58Z mckusick $
     */
    
    #ifndef _UFS_FFS_FS_H_
    #define _UFS_FFS_FS_H_
    
    #include <sys/mount.h>
    #include <ufs/ufs/dinode.h>
    
    /*
     * Each disk drive contains some number of filesystems.
     * A filesystem consists of a number of cylinder groups.
     * Each cylinder group has inodes and data.
     *
     * A filesystem is described by its super-block, which in turn
     * describes the cylinder groups.  The super-block is critical
     * data and is replicated in each cylinder group to protect against
     * catastrophic loss.  This is done at `newfs' time and the critical
     * super-block data does not change, so the copies need not be
     * referenced further unless disaster strikes.
     *
     * For filesystem fs, the offsets of the various blocks of interest
     * are given in the super block as:
     *      [fs->fs_sblkno]         Super-block
     *      [fs->fs_cblkno]         Cylinder group block
     *      [fs->fs_iblkno]         Inode blocks
     *      [fs->fs_dblkno]         Data blocks
     * The beginning of cylinder group cg in fs, is given by
     * the ``cgbase(fs, cg)'' macro.
     *
     * Depending on the architecture and the media, the superblock may
     * reside in any one of four places. For tiny media where every block 
     * counts, it is placed at the very front of the partition. Historically,
     * UFS1 placed it 8K from the front to leave room for the disk label and
     * a small bootstrap. For UFS2 it got moved to 64K from the front to leave
     * room for the disk label and a bigger bootstrap, and for really piggy
     * systems we check at 256K from the front if the first three fail. In
     * all cases the size of the superblock will be SBLOCKSIZE. All values are
     * given in byte-offset form, so they do not imply a sector size. The
     * SBLOCKSEARCH specifies the order in which the locations should be searched.
     */
    #define SBLOCK_FLOPPY        0
    #define SBLOCK_UFS1       8192
    #define SBLOCK_UFS2      65536
    #define SBLOCK_PIGGY    262144
    #define SBLOCKSIZE        8192
    #define SBLOCKSEARCH \
            { SBLOCK_UFS2, SBLOCK_UFS1, SBLOCK_FLOPPY, SBLOCK_PIGGY, -1 }
    
    /*
     * Max number of fragments per block. This value is NOT tweakable.
     */
    #define MAXFRAG         8
    
    /*
     * Addresses stored in inodes are capable of addressing fragments
     * of `blocks'. File system blocks of at most size MAXBSIZE can
     * be optionally broken into 2, 4, or 8 pieces, each of which is
     * addressable; these pieces may be DEV_BSIZE, or some multiple of
     * a DEV_BSIZE unit.
     *
     * Large files consist of exclusively large data blocks.  To avoid
     * undue wasted disk space, the last data block of a small file may be
     * allocated as only as many fragments of a large block as are
     * necessary.  The filesystem format retains only a single pointer
     * to such a fragment, which is a piece of a single large block that
     * has been divided.  The size of such a fragment is determinable from
     * information in the inode, using the ``blksize(fs, ip, lbn)'' macro.
    *
    * The filesystem records space availability at the fragment level;
    * to determine block availability, aligned fragments are examined.
    */
   
   /*
    * MINBSIZE is the smallest allowable block size.
    * In order to insure that it is possible to create files of size
    * 2^32 with only two levels of indirection, MINBSIZE is set to 4096.
    * MINBSIZE must be big enough to hold a cylinder group block,
    * thus changes to (struct cg) must keep its size within MINBSIZE.
    * Note that super blocks are always of size SBLOCKSIZE,
    * and that both SBLOCKSIZE and MAXBSIZE must be >= MINBSIZE.
    */
   #define MINBSIZE        4096
   
   /*
    * The path name on which the filesystem is mounted is maintained
    * in fs_fsmnt. MAXMNTLEN defines the amount of space allocated in
    * the super block for this name.
    */
   #define MAXMNTLEN       468
   
   /*
    * The volume name for this filesystem is maintained in fs_volname.
    * MAXVOLLEN defines the length of the buffer allocated.
    */
   #define MAXVOLLEN       32
   
   /*
    * There is a 128-byte region in the superblock reserved for in-core
    * pointers to summary information. Originally this included an array
    * of pointers to blocks of struct csum; now there are just a few
    * pointers and the remaining space is padded with fs_ocsp[].
    *
    * NOCSPTRS determines the size of this padding. One pointer (fs_csp)
    * is taken away to point to a contiguous array of struct csum for
    * all cylinder groups; a second (fs_maxcluster) points to an array
    * of cluster sizes that is computed as cylinder groups are inspected,
    * and the third points to an array that tracks the creation of new
    * directories. A fourth pointer, fs_active, is used when creating
    * snapshots; it points to a bitmap of cylinder groups for which the
    * free-block bitmap has changed since the snapshot operation began.
    */
   #define NOCSPTRS        ((128 / sizeof(void *)) - 4)
   
   /*
    * A summary of contiguous blocks of various sizes is maintained
    * in each cylinder group. Normally this is set by the initial
    * value of fs_maxcontig. To conserve space, a maximum summary size
    * is set by FS_MAXCONTIG.
    */
   #define FS_MAXCONTIG    16
   
   /*
    * MINFREE gives the minimum acceptable percentage of filesystem
    * blocks which may be free. If the freelist drops below this level
    * only the superuser may continue to allocate blocks. This may
    * be set to 0 if no reserve of free blocks is deemed necessary,
    * however throughput drops by fifty percent if the filesystem
    * is run at between 95% and 100% full; thus the minimum default
    * value of fs_minfree is 5%. However, to get good clustering
    * performance, 10% is a better choice. hence we use 10% as our
    * default value. With 10% free space, fragmentation is not a
    * problem, so we choose to optimize for time.
    */
   #define MINFREE         8
   #define DEFAULTOPT      FS_OPTTIME
   
   /*
    * Grigoriy Orlov <gluk@ptci.ru> has done some extensive work to fine
    * tune the layout preferences for directories within a filesystem.
    * His algorithm can be tuned by adjusting the following parameters
    * which tell the system the average file size and the average number
    * of files per directory. These defaults are well selected for typical
    * filesystems, but may need to be tuned for odd cases like filesystems
    * being used for squid caches or news spools.
    */
   #define AVFILESIZ       16384   /* expected average file size */
   #define AFPDIR          64      /* expected number of files per directory */
   
   /*
    * The maximum number of snapshot nodes that can be associated
    * with each filesystem. This limit affects only the number of
    * snapshot files that can be recorded within the superblock so
    * that they can be found when the filesystem is mounted. However,
    * maintaining too many will slow the filesystem performance, so
    * having this limit is a good idea.
    */
   #define FSMAXSNAP 20
   
   /*
    * Used to identify special blocks in snapshots:
    *
    * BLK_NOCOPY - A block that was unallocated at the time the snapshot
    *      was taken, hence does not need to be copied when written.
    * BLK_SNAP - A block held by another snapshot that is not needed by this
    *      snapshot. When the other snapshot is freed, the BLK_SNAP entries
    *      are converted to BLK_NOCOPY. These are needed to allow fsck to
    *      identify blocks that are in use by other snapshots (which are
    *      expunged from this snapshot).
    */
   #define BLK_NOCOPY ((ufs2_daddr_t)(1))
   #define BLK_SNAP ((ufs2_daddr_t)(2))
   
   /*
    * Sysctl values for the fast filesystem.
    */
   #define FFS_ADJ_REFCNT           1      /* adjust inode reference count */
   #define FFS_ADJ_BLKCNT           2      /* adjust inode used block count */
   #define FFS_BLK_FREE             3      /* free range of blocks in map */
   #define FFS_DIR_FREE             4      /* free specified dir inodes in map */
   #define FFS_FILE_FREE            5      /* free specified file inodes in map */
   #define FFS_SET_FLAGS            6      /* set filesystem flags */
   #define FFS_ADJ_NDIR             7      /* adjust number of directories */
   #define FFS_ADJ_NBFREE           8      /* adjust number of free blocks */
   #define FFS_ADJ_NIFREE           9      /* adjust number of free inodes */
   #define FFS_ADJ_NFFREE          10      /* adjust number of free frags */
   #define FFS_ADJ_NUMCLUSTERS     11      /* adjust number of free clusters */
   #define FFS_SET_CWD             12      /* set current directory */
   #define FFS_SET_DOTDOT          13      /* set inode number for ".." */
   #define FFS_UNLINK              14      /* remove a name in the filesystem */
   #define FFS_SET_INODE           15      /* update an on-disk inode */
   #define FFS_SET_BUFOUTPUT       16      /* set buffered writing on descriptor */
   #define FFS_MAXID               16      /* number of valid ffs ids */
   
   /*
    * Command structure passed in to the filesystem to adjust filesystem values.
    */
   #define FFS_CMD_VERSION         0x19790518      /* version ID */
   struct fsck_cmd {
           int32_t version;        /* version of command structure */
           int32_t handle;         /* reference to filesystem to be changed */
           int64_t value;          /* inode or block number to be affected */
           int64_t size;           /* amount or range to be adjusted */
           int64_t spare;          /* reserved for future use */
   };
   
   /*
    * A recovery structure placed at the end of the boot block area by newfs
    * that can be used by fsck to search for alternate superblocks.
    */
   struct fsrecovery {
           int32_t fsr_magic;      /* magic number */
           int32_t fsr_fsbtodb;    /* fsbtodb and dbtofsb shift constant */
           int32_t fsr_sblkno;     /* offset of super-block in filesys */
           int32_t fsr_fpg;        /* blocks per group * fs_frag */
           u_int32_t fsr_ncg;      /* number of cylinder groups */
   };
   
   /*
    * Per cylinder group information; summarized in blocks allocated
    * from first cylinder group data blocks.  These blocks have to be
    * read in from fs_csaddr (size fs_cssize) in addition to the
    * super block.
    */
   struct csum {
           int32_t cs_ndir;                /* number of directories */
           int32_t cs_nbfree;              /* number of free blocks */
           int32_t cs_nifree;              /* number of free inodes */
           int32_t cs_nffree;              /* number of free frags */
   };
   struct csum_total {
           int64_t cs_ndir;                /* number of directories */
           int64_t cs_nbfree;              /* number of free blocks */
           int64_t cs_nifree;              /* number of free inodes */
           int64_t cs_nffree;              /* number of free frags */
           int64_t cs_numclusters;         /* number of free clusters */
           int64_t cs_spare[3];            /* future expansion */
   };
   
   /*
    * Super block for an FFS filesystem.
    */
   struct fs {
           int32_t  fs_firstfield;         /* historic filesystem linked list, */
           int32_t  fs_unused_1;           /*     used for incore super blocks */
           int32_t  fs_sblkno;             /* offset of super-block in filesys */
           int32_t  fs_cblkno;             /* offset of cyl-block in filesys */
           int32_t  fs_iblkno;             /* offset of inode-blocks in filesys */
           int32_t  fs_dblkno;             /* offset of first data after cg */
           int32_t  fs_old_cgoffset;       /* cylinder group offset in cylinder */
           int32_t  fs_old_cgmask;         /* used to calc mod fs_ntrak */
           int32_t  fs_old_time;           /* last time written */
           int32_t  fs_old_size;           /* number of blocks in fs */
           int32_t  fs_old_dsize;          /* number of data blocks in fs */
           u_int32_t fs_ncg;               /* number of cylinder groups */
           int32_t  fs_bsize;              /* size of basic blocks in fs */
           int32_t  fs_fsize;              /* size of frag blocks in fs */
           int32_t  fs_frag;               /* number of frags in a block in fs */
   /* these are configuration parameters */
           int32_t  fs_minfree;            /* minimum percentage of free blocks */
           int32_t  fs_old_rotdelay;       /* num of ms for optimal next block */
           int32_t  fs_old_rps;            /* disk revolutions per second */
   /* these fields can be computed from the others */
           int32_t  fs_bmask;              /* ``blkoff'' calc of blk offsets */
           int32_t  fs_fmask;              /* ``fragoff'' calc of frag offsets */
           int32_t  fs_bshift;             /* ``lblkno'' calc of logical blkno */
           int32_t  fs_fshift;             /* ``numfrags'' calc number of frags */
   /* these are configuration parameters */
           int32_t  fs_maxcontig;          /* max number of contiguous blks */
           int32_t  fs_maxbpg;             /* max number of blks per cyl group */
   /* these fields can be computed from the others */
           int32_t  fs_fragshift;          /* block to frag shift */
           int32_t  fs_fsbtodb;            /* fsbtodb and dbtofsb shift constant */
           int32_t  fs_sbsize;             /* actual size of super block */
           int32_t  fs_spare1[2];          /* old fs_csmask */
                                           /* old fs_csshift */
           int32_t  fs_nindir;             /* value of NINDIR */
           u_int32_t fs_inopb;             /* value of INOPB */
           int32_t  fs_old_nspf;           /* value of NSPF */
   /* yet another configuration parameter */
           int32_t  fs_optim;              /* optimization preference, see below */
           int32_t  fs_old_npsect;         /* # sectors/track including spares */
           int32_t  fs_old_interleave;     /* hardware sector interleave */
           int32_t  fs_old_trackskew;      /* sector 0 skew, per track */
           int32_t  fs_id[2];              /* unique filesystem id */
   /* sizes determined by number of cylinder groups and their sizes */
           int32_t  fs_old_csaddr;         /* blk addr of cyl grp summary area */
           int32_t  fs_cssize;             /* size of cyl grp summary area */
           int32_t  fs_cgsize;             /* cylinder group size */
           int32_t  fs_spare2;             /* old fs_ntrak */
           int32_t  fs_old_nsect;          /* sectors per track */
           int32_t  fs_old_spc;            /* sectors per cylinder */
           int32_t  fs_old_ncyl;           /* cylinders in filesystem */
           int32_t  fs_old_cpg;            /* cylinders per group */
           u_int32_t fs_ipg;               /* inodes per group */
           int32_t  fs_fpg;                /* blocks per group * fs_frag */
   /* this data must be re-computed after crashes */
           struct  csum fs_old_cstotal;    /* cylinder summary information */
   /* these fields are cleared at mount time */
           int8_t   fs_fmod;               /* super block modified flag */
           int8_t   fs_clean;              /* filesystem is clean flag */
           int8_t   fs_ronly;              /* mounted read-only flag */
           int8_t   fs_old_flags;          /* old FS_ flags */
           u_char   fs_fsmnt[MAXMNTLEN];   /* name mounted on */
           u_char   fs_volname[MAXVOLLEN]; /* volume name */
           u_int64_t fs_swuid;             /* system-wide uid */
           int32_t  fs_pad;                /* due to alignment of fs_swuid */
   /* these fields retain the current block allocation info */
           int32_t  fs_cgrotor;            /* last cg searched */
           void    *fs_ocsp[NOCSPTRS];     /* padding; was list of fs_cs buffers */
           u_int8_t *fs_contigdirs;        /* (u) # of contig. allocated dirs */
           struct  csum *fs_csp;           /* (u) cg summary info buffer */
           int32_t *fs_maxcluster;         /* (u) max cluster in each cyl group */
           u_int   *fs_active;             /* (u) used by snapshots to track fs */
           int32_t  fs_old_cpc;            /* cyl per cycle in postbl */
           int32_t  fs_maxbsize;           /* maximum blocking factor permitted */
           int64_t  fs_unrefs;             /* number of unreferenced inodes */
           int64_t  fs_providersize;       /* size of underlying GEOM provider */
           int64_t  fs_metaspace;          /* size of area reserved for metadata */
           int64_t  fs_sparecon64[13];     /* old rotation block list head */
           int64_t  fs_sblockactualloc;    /* byte offset of this superblock */
           int64_t  fs_sblockloc;          /* byte offset of standard superblock */
           struct  csum_total fs_cstotal;  /* (u) cylinder summary information */
           ufs_time_t fs_time;             /* last time written */
           int64_t  fs_size;               /* number of blocks in fs */
           int64_t  fs_dsize;              /* number of data blocks in fs */
           ufs2_daddr_t fs_csaddr;         /* blk addr of cyl grp summary area */
           int64_t  fs_pendingblocks;      /* (u) blocks being freed */
           u_int32_t fs_pendinginodes;     /* (u) inodes being freed */
           uint32_t fs_snapinum[FSMAXSNAP];/* list of snapshot inode numbers */
           u_int32_t fs_avgfilesize;       /* expected average file size */
           u_int32_t fs_avgfpdir;          /* expected # of files per directory */
           int32_t  fs_save_cgsize;        /* save real cg size to use fs_bsize */
           ufs_time_t fs_mtime;            /* Last mount or fsck time. */
           int32_t  fs_sujfree;            /* SUJ free list */
           int32_t  fs_sparecon32[22];     /* reserved for future constants */
           u_int32_t fs_metackhash;        /* metadata check-hash, see CK_ below */
           int32_t  fs_flags;              /* see FS_ flags below */
           int32_t  fs_contigsumsize;      /* size of cluster summary array */ 
           int32_t  fs_maxsymlinklen;      /* max length of an internal symlink */
           int32_t  fs_old_inodefmt;       /* format of on-disk inodes */
           u_int64_t fs_maxfilesize;       /* maximum representable file size */
           int64_t  fs_qbmask;             /* ~fs_bmask for use with 64-bit size */
           int64_t  fs_qfmask;             /* ~fs_fmask for use with 64-bit size */
           int32_t  fs_state;              /* validate fs_clean field */
           int32_t  fs_old_postblformat;   /* format of positional layout tables */
           int32_t  fs_old_nrpos;          /* number of rotational positions */
           int32_t  fs_spare5[2];          /* old fs_postbloff */
                                           /* old fs_rotbloff */
           int32_t  fs_magic;              /* magic number */
   };
   
   /* Sanity checking. */
   #ifdef CTASSERT
   CTASSERT(sizeof(struct fs) == 1376);
   #endif
   
   /*
    * Filesystem identification
    */
   #define FS_UFS1_MAGIC   0x011954        /* UFS1 fast filesystem magic number */
   #define FS_UFS2_MAGIC   0x19540119      /* UFS2 fast filesystem magic number */
   #define FS_BAD_MAGIC    0x19960408      /* UFS incomplete newfs magic number */
   #define FS_42INODEFMT   -1              /* 4.2BSD inode format */
   #define FS_44INODEFMT   2               /* 4.4BSD inode format */
   
   /*
    * Preference for optimization.
    */
   #define FS_OPTTIME      0       /* minimize allocation time */
   #define FS_OPTSPACE     1       /* minimize disk fragmentation */
   
   /*
    * Filesystem flags.
    *
    * The FS_UNCLEAN flag is set by the kernel when the filesystem was
    * mounted with fs_clean set to zero. The FS_DOSOFTDEP flag indicates
    * that the filesystem should be managed by the soft updates code.
    * Note that the FS_NEEDSFSCK flag is set and cleared only by the
    * fsck utility. It is set when background fsck finds an unexpected
    * inconsistency which requires a traditional foreground fsck to be
    * run. Such inconsistencies should only be found after an uncorrectable
    * disk error. A foreground fsck will clear the FS_NEEDSFSCK flag when
    * it has successfully cleaned up the filesystem. The kernel uses this
    * flag to enforce that inconsistent filesystems be mounted read-only.
    * The FS_INDEXDIRS flag when set indicates that the kernel maintains
    * on-disk auxiliary indexes (such as B-trees) for speeding directory
    * accesses. Kernels that do not support auxiliary indices clear the
    * flag to indicate that the indices need to be rebuilt (by fsck) before
    * they can be used. When a filesystem is mounted, any flags not
    * included in FS_SUPPORTED are cleared. This lets newer features
    * know that the filesystem has been run on an older version of the
    * filesystem and thus that data structures associated with those
    * features are out-of-date and need to be rebuilt.
    *
    * FS_ACLS indicates that POSIX.1e ACLs are administratively enabled
    * for the file system, so they should be loaded from extended attributes,
    * observed for access control purposes, and be administered by object
    * owners.  FS_NFS4ACLS indicates that NFSv4 ACLs are administratively
    * enabled.  This flag is mutually exclusive with FS_ACLS.  FS_MULTILABEL
    * indicates that the TrustedBSD MAC Framework should attempt to back MAC
    * labels into extended attributes on the file system rather than maintain
    * a single mount label for all objects.
    */
   #define FS_UNCLEAN      0x00000001 /* filesystem not clean at mount */
   #define FS_DOSOFTDEP    0x00000002 /* filesystem using soft dependencies */
   #define FS_NEEDSFSCK    0x00000004 /* filesystem needs sync fsck before mount */
   #define FS_SUJ          0x00000008 /* Filesystem using softupdate journal */
   #define FS_ACLS         0x00000010 /* file system has POSIX.1e ACLs enabled */
   #define FS_MULTILABEL   0x00000020 /* file system is MAC multi-label */
   #define FS_GJOURNAL     0x00000040 /* gjournaled file system */
   #define FS_FLAGS_UPDATED 0x0000080 /* flags have been moved to new location */
   #define FS_NFS4ACLS     0x00000100 /* file system has NFSv4 ACLs enabled */
   #define FS_METACKHASH   0x00000200 /* kernel supports metadata check hashes */
   #define FS_TRIM         0x00000400 /* issue BIO_DELETE for deleted blocks */
   #define FS_SUPPORTED    0x00FFFFFF /* supported flags, others cleared at mount*/
   /*
    * Things that we may someday support, but currently do not.
    * These flags are all cleared so we know if we ran on a kernel
    * that does not support them.
    */
   #define FS_INDEXDIRS    0x01000000 /* kernel supports indexed directories */
   #define FS_VARBLKSIZE   0x02000000 /* kernel supports variable block sizes */
   #define FS_COOLOPT1     0x04000000 /* kernel supports cool option 1 */
   #define FS_COOLOPT2     0x08000000 /* kernel supports cool option 2 */
   #define FS_COOLOPT3     0x10000000 /* kernel supports cool option 3 */
   #define FS_COOLOPT4     0x20000000 /* kernel supports cool option 4 */
   #define FS_COOLOPT5     0x40000000 /* kernel supports cool option 5 */
   #define FS_COOLOPT6     0x80000000 /* kernel supports cool option 6 */
   
   /*
    * The fs_metackhash field indicates the types of metadata check-hash
    * that are maintained for a filesystem. Not all filesystems check-hash
    * all metadata.
    */
   #define CK_SUPERBLOCK   0x0001  /* the superblock */
   #define CK_CYLGRP       0x0002  /* the cylinder groups */
   #define CK_INODE        0x0004  /* inodes */
   #define CK_INDIR        0x0008  /* indirect blocks */
   #define CK_DIR          0x0010  /* directory contents */
   /*
    * The BX_FSPRIV buffer b_xflags are used to track types of data in buffers.
    */
   #define BX_SUPERBLOCK   0x00010000      /* superblock */
   #define BX_CYLGRP       0x00020000      /* cylinder groups */
   #define BX_INODE        0x00040000      /* inodes */
   #define BX_INDIR        0x00080000      /* indirect blocks */
   #define BX_DIR          0x00100000      /* directory contents */
   
   #define PRINT_UFS_BUF_XFLAGS "\2\25dir\24indir\23inode\22cylgrp\21superblock"
   
   /*
    * Macros to access bits in the fs_active array.
    */
   #define ACTIVECGNUM(fs, cg)     ((fs)->fs_active[(cg) / (NBBY * sizeof(int))])
   #define ACTIVECGOFF(cg)         (1 << ((cg) % (NBBY * sizeof(int))))
   #define ACTIVESET(fs, cg)       do {                                    \
           if ((fs)->fs_active)                                            \
                   ACTIVECGNUM((fs), (cg)) |= ACTIVECGOFF((cg));           \
   } while (0)
   #define ACTIVECLEAR(fs, cg)     do {                                    \
           if ((fs)->fs_active)                                            \
                   ACTIVECGNUM((fs), (cg)) &= ~ACTIVECGOFF((cg));          \
   } while (0)
   
   /*
    * The size of a cylinder group is calculated by CGSIZE. The maximum size
    * is limited by the fact that cylinder groups are at most one block.
    * Its size is derived from the size of the maps maintained in the
    * cylinder group and the (struct cg) size.
    */
   #define CGSIZE(fs) \
       /* base cg */       (sizeof(struct cg) + sizeof(int32_t) + \
       /* old btotoff */   (fs)->fs_old_cpg * sizeof(int32_t) + \
       /* old boff */      (fs)->fs_old_cpg * sizeof(u_int16_t) + \
       /* inode map */     howmany((fs)->fs_ipg, NBBY) + \
       /* block map */     howmany((fs)->fs_fpg, NBBY) +\
       /* if present */    ((fs)->fs_contigsumsize <= 0 ? 0 : \
       /* cluster sum */   (fs)->fs_contigsumsize * sizeof(int32_t) + \
       /* cluster map */   howmany(fragstoblks(fs, (fs)->fs_fpg), NBBY)))
   
   /*
    * The minimal number of cylinder groups that should be created.
    */
   #define MINCYLGRPS      4
   
   /*
    * Convert cylinder group to base address of its global summary info.
    */
   #define fs_cs(fs, indx) fs_csp[indx]
   
   /*
    * Cylinder group block for a filesystem.
    */
   #define CG_MAGIC        0x090255
   struct cg {
           int32_t  cg_firstfield;         /* historic cyl groups linked list */
           int32_t  cg_magic;              /* magic number */
           int32_t  cg_old_time;           /* time last written */
           u_int32_t cg_cgx;               /* we are the cgx'th cylinder group */
           int16_t  cg_old_ncyl;           /* number of cyl's this cg */
           int16_t  cg_old_niblk;          /* number of inode blocks this cg */
           u_int32_t cg_ndblk;             /* number of data blocks this cg */
           struct   csum cg_cs;            /* cylinder summary information */
           u_int32_t cg_rotor;             /* position of last used block */
           u_int32_t cg_frotor;            /* position of last used frag */
           u_int32_t cg_irotor;            /* position of last used inode */
           u_int32_t cg_frsum[MAXFRAG];    /* counts of available frags */
           int32_t  cg_old_btotoff;        /* (int32) block totals per cylinder */
           int32_t  cg_old_boff;           /* (u_int16) free block positions */
           u_int32_t cg_iusedoff;          /* (u_int8) used inode map */
           u_int32_t cg_freeoff;           /* (u_int8) free block map */
           u_int32_t cg_nextfreeoff;       /* (u_int8) next available space */
           u_int32_t cg_clustersumoff;     /* (u_int32) counts of avail clusters */
           u_int32_t cg_clusteroff;                /* (u_int8) free cluster map */
           u_int32_t cg_nclusterblks;      /* number of clusters this cg */
           u_int32_t cg_niblk;             /* number of inode blocks this cg */
           u_int32_t cg_initediblk;                /* last initialized inode */
           u_int32_t cg_unrefs;            /* number of unreferenced inodes */
           int32_t  cg_sparecon32[1];      /* reserved for future use */
           u_int32_t cg_ckhash;            /* check-hash of this cg */
           ufs_time_t cg_time;             /* time last written */
           int64_t  cg_sparecon64[3];      /* reserved for future use */
           u_int8_t cg_space[1];           /* space for cylinder group maps */
   /* actually longer */
   };
   
   /*
    * Macros for access to cylinder group array structures
    */
   #define cg_chkmagic(cgp) ((cgp)->cg_magic == CG_MAGIC)
   #define cg_inosused(cgp) \
       ((u_int8_t *)((u_int8_t *)(cgp) + (cgp)->cg_iusedoff))
   #define cg_blksfree(cgp) \
       ((u_int8_t *)((u_int8_t *)(cgp) + (cgp)->cg_freeoff))
   #define cg_clustersfree(cgp) \
       ((u_int8_t *)((u_int8_t *)(cgp) + (cgp)->cg_clusteroff))
   #define cg_clustersum(cgp) \
       ((int32_t *)((uintptr_t)(cgp) + (cgp)->cg_clustersumoff))
   
   /*
    * Turn filesystem block numbers into disk block addresses.
    * This maps filesystem blocks to device size blocks.
    */
   #define fsbtodb(fs, b)  ((daddr_t)(b) << (fs)->fs_fsbtodb)
   #define dbtofsb(fs, b)  ((b) >> (fs)->fs_fsbtodb)
   
   /*
    * Cylinder group macros to locate things in cylinder groups.
    * They calc filesystem addresses of cylinder group data structures.
    */
   #define cgbase(fs, c)   (((ufs2_daddr_t)(fs)->fs_fpg) * (c))
   #define cgdata(fs, c)   (cgdmin(fs, c) + (fs)->fs_metaspace)    /* data zone */
   #define cgmeta(fs, c)   (cgdmin(fs, c))                         /* meta data */
   #define cgdmin(fs, c)   (cgstart(fs, c) + (fs)->fs_dblkno)      /* 1st data */
   #define cgimin(fs, c)   (cgstart(fs, c) + (fs)->fs_iblkno)      /* inode blk */
   #define cgsblock(fs, c) (cgstart(fs, c) + (fs)->fs_sblkno)      /* super blk */
   #define cgtod(fs, c)    (cgstart(fs, c) + (fs)->fs_cblkno)      /* cg block */
   #define cgstart(fs, c)                                                  \
          ((fs)->fs_magic == FS_UFS2_MAGIC ? cgbase(fs, c) :               \
          (cgbase(fs, c) + (fs)->fs_old_cgoffset * ((c) & ~((fs)->fs_old_cgmask))))
   
   /*
    * Macros for handling inode numbers:
    *     inode number to filesystem block offset.
    *     inode number to cylinder group number.
    *     inode number to filesystem block address.
    */
   #define ino_to_cg(fs, x)        (((ino_t)(x)) / (fs)->fs_ipg)
   #define ino_to_fsba(fs, x)                                              \
           ((ufs2_daddr_t)(cgimin(fs, ino_to_cg(fs, (ino_t)(x))) +         \
               (blkstofrags((fs), ((((ino_t)(x)) % (fs)->fs_ipg) / INOPB(fs))))))
   #define ino_to_fsbo(fs, x)      (((ino_t)(x)) % INOPB(fs))
   
   /*
    * Give cylinder group number for a filesystem block.
    * Give cylinder group block number for a filesystem block.
    */
   #define dtog(fs, d)     ((d) / (fs)->fs_fpg)
   #define dtogd(fs, d)    ((d) % (fs)->fs_fpg)
   
   /*
    * Extract the bits for a block from a map.
    * Compute the cylinder and rotational position of a cyl block addr.
    */
   #define blkmap(fs, map, loc) \
       (((map)[(loc) / NBBY] >> ((loc) % NBBY)) & (0xff >> (NBBY - (fs)->fs_frag)))
   
   /*
    * The following macros optimize certain frequently calculated
    * quantities by using shifts and masks in place of divisions
    * modulos and multiplications.
    */
   #define blkoff(fs, loc)         /* calculates (loc % fs->fs_bsize) */ \
           ((loc) & (fs)->fs_qbmask)
   #define fragoff(fs, loc)        /* calculates (loc % fs->fs_fsize) */ \
           ((loc) & (fs)->fs_qfmask)
   #define lfragtosize(fs, frag)   /* calculates ((off_t)frag * fs->fs_fsize) */ \
           (((off_t)(frag)) << (fs)->fs_fshift)
   #define lblktosize(fs, blk)     /* calculates ((off_t)blk * fs->fs_bsize) */ \
           (((off_t)(blk)) << (fs)->fs_bshift)
   /* Use this only when `blk' is known to be small, e.g., < UFS_NDADDR. */
   #define smalllblktosize(fs, blk)    /* calculates (blk * fs->fs_bsize) */ \
           ((blk) << (fs)->fs_bshift)
   #define lblkno(fs, loc)         /* calculates (loc / fs->fs_bsize) */ \
           ((loc) >> (fs)->fs_bshift)
   #define numfrags(fs, loc)       /* calculates (loc / fs->fs_fsize) */ \
           ((loc) >> (fs)->fs_fshift)
   #define blkroundup(fs, size)    /* calculates roundup(size, fs->fs_bsize) */ \
           (((size) + (fs)->fs_qbmask) & (fs)->fs_bmask)
   #define fragroundup(fs, size)   /* calculates roundup(size, fs->fs_fsize) */ \
           (((size) + (fs)->fs_qfmask) & (fs)->fs_fmask)
   #define fragstoblks(fs, frags)  /* calculates (frags / fs->fs_frag) */ \
           ((frags) >> (fs)->fs_fragshift)
   #define blkstofrags(fs, blks)   /* calculates (blks * fs->fs_frag) */ \
           ((blks) << (fs)->fs_fragshift)
   #define fragnum(fs, fsb)        /* calculates (fsb % fs->fs_frag) */ \
           ((fsb) & ((fs)->fs_frag - 1))
   #define blknum(fs, fsb)         /* calculates rounddown(fsb, fs->fs_frag) */ \
           ((fsb) &~ ((fs)->fs_frag - 1))
   
   /*
    * Determine the number of available frags given a
    * percentage to hold in reserve.
    */
   #define freespace(fs, percentreserved) \
           (blkstofrags((fs), (fs)->fs_cstotal.cs_nbfree) + \
           (fs)->fs_cstotal.cs_nffree - \
           (((off_t)((fs)->fs_dsize)) * (percentreserved) / 100))
   
   /*
    * Determining the size of a file block in the filesystem.
    */
   #define blksize(fs, ip, lbn) \
           (((lbn) >= UFS_NDADDR || (ip)->i_size >= \
               (uint64_t)smalllblktosize(fs, (lbn) + 1)) \
               ? (fs)->fs_bsize \
               : (fragroundup(fs, blkoff(fs, (ip)->i_size))))
   #define sblksize(fs, size, lbn) \
           (((lbn) >= UFS_NDADDR || (size) >= ((lbn) + 1) << (fs)->fs_bshift) \
             ? (fs)->fs_bsize \
             : (fragroundup(fs, blkoff(fs, (size)))))
   
   /*
    * Number of indirects in a filesystem block.
    */
   #define NINDIR(fs)      ((fs)->fs_nindir)
   
   /*
    * Indirect lbns are aligned on UFS_NDADDR addresses where single indirects
    * are the negated address of the lowest lbn reachable, double indirects
    * are this lbn - 1 and triple indirects are this lbn - 2.  This yields
    * an unusual bit order to determine level.
    */
   static inline int
   lbn_level(ufs_lbn_t lbn)
   {
           if (lbn >= 0)
                   return 0;
           switch (lbn & 0x3) {
           case 0:
                   return (0);
           case 1:
                   break;
           case 2:
                   return (2);
           case 3:
                   return (1);
           default:
                   break;
           }
           return (-1);
   }
   
   static inline ufs_lbn_t
   lbn_offset(struct fs *fs, int level)
   {
           ufs_lbn_t res;
   
           for (res = 1; level > 0; level--)
                   res *= NINDIR(fs);
           return (res);
   }
   
   /*
    * Number of inodes in a secondary storage block/fragment.
    */
   #define INOPB(fs)       ((fs)->fs_inopb)
   #define INOPF(fs)       ((fs)->fs_inopb >> (fs)->fs_fragshift)
   
   /*
    * Softdep journal record format.
    */
   
   #define JOP_ADDREF      1       /* Add a reference to an inode. */
   #define JOP_REMREF      2       /* Remove a reference from an inode. */
   #define JOP_NEWBLK      3       /* Allocate a block. */
   #define JOP_FREEBLK     4       /* Free a block or a tree of blocks. */
   #define JOP_MVREF       5       /* Move a reference from one off to another. */
   #define JOP_TRUNC       6       /* Partial truncation record. */
   #define JOP_SYNC        7       /* fsync() complete record. */
   
   #define JREC_SIZE       32      /* Record and segment header size. */
   
   #define SUJ_MIN         (4 * 1024 * 1024)       /* Minimum journal size */
   #define SUJ_MAX         (32 * 1024 * 1024)      /* Maximum journal size */
   #define SUJ_FILE        ".sujournal"            /* Journal file name */
   
   /*
    * Size of the segment record header.  There is at most one for each disk
    * block in the journal.  The segment header is followed by an array of
    * records.  fsck depends on the first element in each record being 'op'
    * and the second being 'ino'.  Segments may span multiple disk blocks but
    * the header is present on each.
    */
   struct jsegrec {
           uint64_t        jsr_seq;        /* Our sequence number */
           uint64_t        jsr_oldest;     /* Oldest valid sequence number */
           uint16_t        jsr_cnt;        /* Count of valid records */
           uint16_t        jsr_blocks;     /* Count of device bsize blocks. */
           uint32_t        jsr_crc;        /* 32bit crc of the valid space */
           ufs_time_t      jsr_time;       /* timestamp for mount instance */
   };
   
   /*
    * Reference record.  Records a single link count modification.
    */
   struct jrefrec {
           uint32_t        jr_op;
           uint32_t        jr_ino;
           uint32_t        jr_parent;
           uint16_t        jr_nlink;
           uint16_t        jr_mode;
           int64_t         jr_diroff;
           uint64_t        jr_unused;
   };
   
   /*
    * Move record.  Records a reference moving within a directory block.  The
    * nlink is unchanged but we must search both locations.
    */
   struct jmvrec {
           uint32_t        jm_op;
           uint32_t        jm_ino;
           uint32_t        jm_parent;
           uint16_t        jm_unused;
           int64_t         jm_oldoff;
           int64_t         jm_newoff;
   };
   
   /*
    * Block record.  A set of frags or tree of blocks starting at an indirect are
    * freed or a set of frags are allocated.
    */
   struct jblkrec {
           uint32_t        jb_op;
           uint32_t        jb_ino;
           ufs2_daddr_t    jb_blkno;
           ufs_lbn_t       jb_lbn;
           uint16_t        jb_frags;
           uint16_t        jb_oldfrags;
           uint32_t        jb_unused;
   };
   
   /*
    * Truncation record.  Records a partial truncation so that it may be
    * completed at check time.  Also used for sync records.
    */
   struct jtrncrec {
           uint32_t        jt_op;
           uint32_t        jt_ino;
           int64_t         jt_size;
           uint32_t        jt_extsize;
           uint32_t        jt_pad[3];
   };
   
   union jrec {
           struct jsegrec  rec_jsegrec;
           struct jrefrec  rec_jrefrec;
           struct jmvrec   rec_jmvrec;
           struct jblkrec  rec_jblkrec;
           struct jtrncrec rec_jtrncrec;
   };
   
   #ifdef CTASSERT
   CTASSERT(sizeof(struct jsegrec) == JREC_SIZE);
   CTASSERT(sizeof(struct jrefrec) == JREC_SIZE);
   CTASSERT(sizeof(struct jmvrec) == JREC_SIZE);
   CTASSERT(sizeof(struct jblkrec) == JREC_SIZE);
   CTASSERT(sizeof(struct jtrncrec) == JREC_SIZE);
   CTASSERT(sizeof(union jrec) == JREC_SIZE);
   #endif
   
   extern int inside[], around[];
   extern u_char *fragtbl[];
   
   /*
    * IOCTLs used for filesystem write suspension.
    */
   #define UFSSUSPEND      _IOW('U', 1, fsid_t)
   #define UFSRESUME       _IO('U', 2)
   
   #endif

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