md_p.h

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/*
   md_p.h : physical layout of Linux RAID devices
          Copyright (C) 1996-98 Ingo Molnar, Gadi Oxman
      
   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; either version 2, or (at your option)
   any later version.
   
   You should have received a copy of the GNU General Public License
   (for example /usr/src/linux/COPYING); if not, write to the Free
   Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.  
*/

#ifndef _MD_P_H
#define _MD_P_H

#include <linux/types.h>

/*
 * RAID superblock.
 *
 * The RAID superblock maintains some statistics on each RAID configuration.
 * Each real device in the RAID set contains it near the end of the device.
 * Some of the ideas are copied from the ext2fs implementation.
 *
 * We currently use 4096 bytes as follows:
 *
 *  word offset function
 *
 *     0  -    31   Constant generic RAID device information.
 *        32  -    63   Generic state information.
 *    64  -   127   Personality specific information.
 *   128  -   511   12 32-words descriptors of the disks in the raid set.
 *   512  -   911   Reserved.
 *   912  -  1023   Disk specific descriptor.
 */

/*
 * If x is the real device size in bytes, we return an apparent size of:
 *
 *  y = (x & ~(MD_RESERVED_BYTES - 1)) - MD_RESERVED_BYTES
 *
 * and place the 4kB superblock at offset y.
 */
#define MD_RESERVED_BYTES       (64 * 1024)
#define MD_RESERVED_SECTORS     (MD_RESERVED_BYTES / 512)

#define MD_NEW_SIZE_SECTORS(x)      ((x & ~(MD_RESERVED_SECTORS - 1)) - MD_RESERVED_SECTORS)

#define MD_SB_BYTES         4096
#define MD_SB_WORDS         (MD_SB_BYTES / 4)
#define MD_SB_SECTORS           (MD_SB_BYTES / 512)

/*
 * The following are counted in 32-bit words
 */
#define MD_SB_GENERIC_OFFSET        0
#define MD_SB_PERSONALITY_OFFSET    64
#define MD_SB_DISKS_OFFSET      128
#define MD_SB_DESCRIPTOR_OFFSET     992

#define MD_SB_GENERIC_CONSTANT_WORDS    32
#define MD_SB_GENERIC_STATE_WORDS   32
#define MD_SB_GENERIC_WORDS     (MD_SB_GENERIC_CONSTANT_WORDS + MD_SB_GENERIC_STATE_WORDS)
#define MD_SB_PERSONALITY_WORDS     64
#define MD_SB_DESCRIPTOR_WORDS      32
#define MD_SB_DISKS         27
#define MD_SB_DISKS_WORDS       (MD_SB_DISKS*MD_SB_DESCRIPTOR_WORDS)
#define MD_SB_RESERVED_WORDS        (1024 - MD_SB_GENERIC_WORDS - MD_SB_PERSONALITY_WORDS - MD_SB_DISKS_WORDS - MD_SB_DESCRIPTOR_WORDS)
#define MD_SB_EQUAL_WORDS       (MD_SB_GENERIC_WORDS + MD_SB_PERSONALITY_WORDS + MD_SB_DISKS_WORDS)

/*
 * Device "operational" state bits
 */
#define MD_DISK_FAULTY      0 /* disk is faulty / operational */
#define MD_DISK_ACTIVE      1 /* disk is running or spare disk */
#define MD_DISK_SYNC        2 /* disk is in sync with the raid set */
#define MD_DISK_REMOVED     3 /* disk is in sync with the raid set */

#define MD_DISK_WRITEMOSTLY 9 /* disk is "write-mostly" is RAID1 config.
                   * read requests will only be sent here in
                   * dire need
                   */

typedef struct mdp_device_descriptor_s {
    __u32 number;       /* 0 Device number in the entire set          */
    __u32 major;        /* 1 Device major number              */
    __u32 minor;        /* 2 Device minor number              */
    __u32 raid_disk;    /* 3 The role of the device in the raid set   */
    __u32 state;        /* 4 Operational state                */
    __u32 reserved[MD_SB_DESCRIPTOR_WORDS - 5];
} mdp_disk_t;

#define MD_SB_MAGIC     0xa92b4efc

/*
 * Superblock state bits
 */
#define MD_SB_CLEAN     0
#define MD_SB_ERRORS        1

#define MD_SB_BITMAP_PRESENT    8 /* bitmap may be present nearby */

/*
 * Notes:
 * - if an array is being reshaped (restriped) in order to change the
 *   the number of active devices in the array, 'raid_disks' will be
 *   the larger of the old and new numbers.  'delta_disks' will
 *   be the "new - old".  So if +ve, raid_disks is the new value, and
 *   "raid_disks-delta_disks" is the old.  If -ve, raid_disks is the
 *   old value and "raid_disks+delta_disks" is the new (smaller) value.
 */


typedef struct mdp_superblock_s {
    /*
     * Constant generic information
     */
    __u32 md_magic;     /*  0 MD identifier                   */
    __u32 major_version;    /*  1 major version to which the set conforms */
    __u32 minor_version;    /*  2 minor version ...               */
    __u32 patch_version;    /*  3 patchlevel version ...              */
    __u32 gvalid_words; /*  4 Number of used words in this section    */
    __u32 set_uuid0;    /*  5 Raid set identifier             */
    __u32 ctime;        /*  6 Creation time               */
    __u32 level;        /*  7 Raid personality                */
    __u32 size;     /*  8 Apparent size of each individual disk   */
    __u32 nr_disks;     /*  9 total disks in the raid set         */
    __u32 raid_disks;   /* 10 disks in a fully functional raid set    */
    __u32 md_minor;     /* 11 preferred MD minor device number        */
    __u32 not_persistent;   /* 12 does it have a persistent superblock    */
    __u32 set_uuid1;    /* 13 Raid set identifier #2              */
    __u32 set_uuid2;    /* 14 Raid set identifier #3              */
    __u32 set_uuid3;    /* 15 Raid set identifier #4              */
    __u32 gstate_creserved[MD_SB_GENERIC_CONSTANT_WORDS - 16];

    /*
     * Generic state information
     */
    __u32 utime;        /*  0 Superblock update time              */
    __u32 state;        /*  1 State bits (clean, ...)             */
    __u32 active_disks; /*  2 Number of currently active disks        */
    __u32 working_disks;    /*  3 Number of working disks             */
    __u32 failed_disks; /*  4 Number of failed disks              */
    __u32 spare_disks;  /*  5 Number of spare disks           */
    __u32 sb_csum;      /*  6 checksum of the whole superblock        */
#ifdef __BIG_ENDIAN
    __u32 events_hi;    /*  7 high-order of superblock update count   */
    __u32 events_lo;    /*  8 low-order of superblock update count    */
    __u32 cp_events_hi; /*  9 high-order of checkpoint update count   */
    __u32 cp_events_lo; /* 10 low-order of checkpoint update count    */
#else
    __u32 events_lo;    /*  7 low-order of superblock update count    */
    __u32 events_hi;    /*  8 high-order of superblock update count   */
    __u32 cp_events_lo; /*  9 low-order of checkpoint update count    */
    __u32 cp_events_hi; /* 10 high-order of checkpoint update count   */
#endif
    __u32 recovery_cp;  /* 11 recovery checkpoint sector count        */
    /* There are only valid for minor_version > 90 */
    __u64 reshape_position; /* 12,13 next address in array-space for reshape */
    __u32 new_level;    /* 14 new level we are reshaping to       */
    __u32 delta_disks;  /* 15 change in number of raid_disks          */
    __u32 new_layout;   /* 16 new layout                  */
    __u32 new_chunk;    /* 17 new chunk size (bytes)              */
    __u32 gstate_sreserved[MD_SB_GENERIC_STATE_WORDS - 18];

    /*
     * Personality information
     */
    __u32 layout;       /*  0 the array's physical layout         */
    __u32 chunk_size;   /*  1 chunk size in bytes             */
    __u32 root_pv;      /*  2 LV root PV */
    __u32 root_block;   /*  3 LV root block */
    __u32 pstate_reserved[MD_SB_PERSONALITY_WORDS - 4];

    /*
     * Disks information
     */
    mdp_disk_t disks[MD_SB_DISKS];

    /*
     * Reserved
     */
    __u32 reserved[MD_SB_RESERVED_WORDS];

    /*
     * Active descriptor
     */
    mdp_disk_t this_disk;

} mdp_super_t;

static inline __u64 md_event(mdp_super_t *sb) {
    __u64 ev = sb->events_hi;
    return (ev<<32)| sb->events_lo;
}

#define MD_SUPERBLOCK_1_TIME_SEC_MASK ((1ULL<<40) - 1)

/*
 * The version-1 superblock :
 * All numeric fields are little-endian.
 *
 * total size: 256 bytes plus 2 per device.
 *  1K allows 384 devices.
 */
struct mdp_superblock_1 {
    /* constant array information - 128 bytes */
    __le32  magic;      /* MD_SB_MAGIC: 0xa92b4efc - little endian */
    __le32  major_version;  /* 1 */
    __le32  feature_map;    /* bit 0 set if 'bitmap_offset' is meaningful */
    __le32  pad0;       /* always set to 0 when writing */

    __u8    set_uuid[16];   /* user-space generated. */
    char    set_name[32];   /* set and interpreted by user-space */

    __le64  ctime;      /* lo 40 bits are seconds, top 24 are microseconds or 0*/
    __le32  level;      /* -4 (multipath), -1 (linear), 0,1,4,5 */
    __le32  layout;     /* only for raid5 and raid10 currently */
    __le64  size;       /* used size of component devices, in 512byte sectors */

    __le32  chunksize;  /* in 512byte sectors */
    __le32  raid_disks;
    __le32  bitmap_offset;  /* sectors after start of superblock that bitmap starts
                 * NOTE: signed, so bitmap can be before superblock
                 * only meaningful of feature_map[0] is set.
                 */

    /* These are only valid with feature bit '4' */
    __le32  new_level;  /* new level we are reshaping to        */
    __le64  reshape_position;   /* next address in array-space for reshape */
    __le32  delta_disks;    /* change in number of raid_disks       */
    __le32  new_layout; /* new layout                   */
    __le32  new_chunk;  /* new chunk size (512byte sectors)     */
    __le32  new_offset; /* signed number to add to data_offset in new
                 * layout.  0 == no-change.  This can be
                 * different on each device in the array.
                 */

    /* constant this-device information - 64 bytes */
    __le64  data_offset;    /* sector start of data, often 0 */
    __le64  data_size;  /* sectors in this device that can be used for data */
    __le64  super_offset;   /* sector start of this superblock */
    __le64  recovery_offset;/* sectors before this offset (from data_offset) have been recovered */
    __le32  dev_number; /* permanent identifier of this  device - not role in raid */
    __le32  cnt_corrected_read; /* number of read errors that were corrected by re-writing */
    __u8    device_uuid[16]; /* user-space setable, ignored by kernel */
    __u8    devflags;   /* per-device flags.  Only one defined...*/
#define WriteMostly1    1   /* mask for writemostly flag in above */
    /* Bad block log.  If there are any bad blocks the feature flag is set.
     * If offset and size are non-zero, that space is reserved and available
     */
    __u8    bblog_shift;    /* shift from sectors to block size */
    __le16  bblog_size; /* number of sectors reserved for list */
    __le32  bblog_offset;   /* sector offset from superblock to bblog,
                 * signed - not unsigned */

    /* array state information - 64 bytes */
    __le64  utime;      /* 40 bits second, 24 bits microseconds */
    __le64  events;     /* incremented when superblock updated */
    __le64  resync_offset;  /* data before this offset (from data_offset) known to be in sync */
    __le32  sb_csum;    /* checksum up to devs[max_dev] */
    __le32  max_dev;    /* size of devs[] array to consider */
    __u8    pad3[64-32];    /* set to 0 when writing */

    /* device state information. Indexed by dev_number.
     * 2 bytes per device
     * Note there are no per-device state flags. State information is rolled
     * into the 'roles' value.  If a device is spare or faulty, then it doesn't
     * have a meaningful role.
     */
    __le16  dev_roles[0];   /* role in array, or 0xffff for a spare, or 0xfffe for faulty */
};

/* feature_map bits */
#define MD_FEATURE_BITMAP_OFFSET    1
#define MD_FEATURE_RECOVERY_OFFSET  2 /* recovery_offset is present and
                       * must be honoured
                       */
#define MD_FEATURE_RESHAPE_ACTIVE   4
#define MD_FEATURE_BAD_BLOCKS       8 /* badblock list is not empty */
#define MD_FEATURE_REPLACEMENT      16 /* This device is replacing an
                        * active device with same 'role'.
                        * 'recovery_offset' is also set.
                        */
#define MD_FEATURE_RESHAPE_BACKWARDS    32 /* Reshape doesn't change number
                        * of devices, but is going
                        * backwards anyway.
                        */
#define MD_FEATURE_NEW_OFFSET       64 /* new_offset must be honoured */
#define MD_FEATURE_ALL          (MD_FEATURE_BITMAP_OFFSET   \
                    |MD_FEATURE_RECOVERY_OFFSET \
                    |MD_FEATURE_RESHAPE_ACTIVE  \
                    |MD_FEATURE_BAD_BLOCKS      \
                    |MD_FEATURE_REPLACEMENT     \
                    |MD_FEATURE_RESHAPE_BACKWARDS   \
                    |MD_FEATURE_NEW_OFFSET      \
                    )

#endif