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root/include/linux/raid/md_p.h

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INCLUDED FROM


DEFINITIONS

This source file includes following definitions.
  1. md_event

/*
   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

/*
 * 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;
}

/*
 * 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 (bytes)                       */
        __u8    pad1[128-124];  /* set to 0 when written */

        /* 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 */
        __u8    pad2[64-57];    /* set to 0 when writing */

        /* array state information - 64 bytes */
        __le64  utime;          /* 40 bits second, 24 btes 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 upto 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_ALL                  (1|2|4)

#endif 


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