include/linux/raid/md_p.h

   1 /*
   2    md_p.h : physical layout of Linux RAID devices
   3           Copyright (C) 1996-98 Ingo Molnar, Gadi Oxman
   4
   5    This program is free software; you can redistribute it and/or modify
   6    it under the terms of the GNU General Public License as published by
   7    the Free Software Foundation; either version 2, or (at your option)
   8    any later version.
   9
  10    You should have received a copy of the GNU General Public License
  11    (for example /usr/src/linux/COPYING); if not, write to the Free
  12    Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  13 */
  14
  15 #ifndef _MD_P_H
  16 #define _MD_P_H
  17
  18 /*
  19  * RAID superblock.
  20  *
  21  * The RAID superblock maintains some statistics on each RAID configuration.
  22  * Each real device in the RAID set contains it near the end of the device.
  23  * Some of the ideas are copied from the ext2fs implementation.
  24  *
  25  * We currently use 4096 bytes as follows:
  26  *
  27  *      word offset     function
  28  *
  29  *         0  -    31   Constant generic RAID device information.
  30  *        32  -    63   Generic state information.
  31  *        64  -   127   Personality specific information.
  32  *       128  -   511   12 32-words descriptors of the disks in the raid set.
  33  *       512  -   911   Reserved.
  34  *       912  -  1023   Disk specific descriptor.
  35  */
  36
  37 /*
  38  * If x is the real device size in bytes, we return an apparent size of:
  39  *
  40  *      y = (x & ~(MD_RESERVED_BYTES - 1)) - MD_RESERVED_BYTES
  41  *
  42  * and place the 4kB superblock at offset y.
  43  */
  44 #define MD_RESERVED_BYTES               (64 * 1024)
  45 #define MD_RESERVED_SECTORS             (MD_RESERVED_BYTES / 512)
  46
  47 #define MD_NEW_SIZE_SECTORS(x)          ((x & ~(MD_RESERVED_SECTORS - 1)) - MD_RESERVED_SECTORS)
  48
  49 #define MD_SB_BYTES                     4096
  50 #define MD_SB_WORDS                     (MD_SB_BYTES / 4)
  51 #define MD_SB_SECTORS                   (MD_SB_BYTES / 512)
  52
  53 /*
  54  * The following are counted in 32-bit words
  55  */
  56 #define MD_SB_GENERIC_OFFSET            0
  57 #define MD_SB_PERSONALITY_OFFSET        64
  58 #define MD_SB_DISKS_OFFSET              128
  59 #define MD_SB_DESCRIPTOR_OFFSET         992
  60
  61 #define MD_SB_GENERIC_CONSTANT_WORDS    32
  62 #define MD_SB_GENERIC_STATE_WORDS       32
  63 #define MD_SB_GENERIC_WORDS             (MD_SB_GENERIC_CONSTANT_WORDS + MD_SB_GENERIC_STATE_WORDS)
  64 #define MD_SB_PERSONALITY_WORDS         64
  65 #define MD_SB_DESCRIPTOR_WORDS          32
  66 #define MD_SB_DISKS                     27
  67 #define MD_SB_DISKS_WORDS               (MD_SB_DISKS*MD_SB_DESCRIPTOR_WORDS)
  68 #define MD_SB_RESERVED_WORDS            (1024 - MD_SB_GENERIC_WORDS - MD_SB_PERSONALITY_WORDS - MD_SB_DISKS_WORDS - MD_SB_DESCRIPTOR_WORDS)
  69 #define MD_SB_EQUAL_WORDS               (MD_SB_GENERIC_WORDS + MD_SB_PERSONALITY_WORDS + MD_SB_DISKS_WORDS)
  70
  71 /*
  72  * Device "operational" state bits
  73  */
  74 #define MD_DISK_FAULTY          0 /* disk is faulty / operational */
  75 #define MD_DISK_ACTIVE          1 /* disk is running or spare disk */
  76 #define MD_DISK_SYNC            2 /* disk is in sync with the raid set */
  77 #define MD_DISK_REMOVED         3 /* disk is in sync with the raid set */
  78
  79 #define MD_DISK_WRITEMOSTLY     9 /* disk is "write-mostly" is RAID1 config.
  80                                    * read requests will only be sent here in
  81                                    * dire need
  82                                    */
  83
  84 typedef struct mdp_device_descriptor_s {
  85         __u32 number;           /* 0 Device number in the entire set          */
  86         __u32 major;            /* 1 Device major number                      */
  87         __u32 minor;            /* 2 Device minor number                      */
  88         __u32 raid_disk;        /* 3 The role of the device in the raid set   */
  89         __u32 state;            /* 4 Operational state                        */
  90         __u32 reserved[MD_SB_DESCRIPTOR_WORDS - 5];
  91 } mdp_disk_t;
  92
  93 #define MD_SB_MAGIC             0xa92b4efc
  94
  95 /*
  96  * Superblock state bits
  97  */
  98 #define MD_SB_CLEAN             0
  99 #define MD_SB_ERRORS            1
 100
 101 #define MD_SB_BITMAP_PRESENT    8 /* bitmap may be present nearby */
 102
 103 /*
 104  * Notes:
 105  * - if an array is being reshaped (restriped) in order to change the
 106  *   the number of active devices in the array, 'raid_disks' will be
 107  *   the larger of the old and new numbers.  'delta_disks' will
 108  *   be the "new - old".  So if +ve, raid_disks is the new value, and
 109  *   "raid_disks-delta_disks" is the old.  If -ve, raid_disks is the
 110  *   old value and "raid_disks+delta_disks" is the new (smaller) value.
 111  */
 112
 113
 114 typedef struct mdp_superblock_s {
 115         /*
 116          * Constant generic information
 117          */
 118         __u32 md_magic;         /*  0 MD identifier                           */
 119         __u32 major_version;    /*  1 major version to which the set conforms */
 120         __u32 minor_version;    /*  2 minor version ...                       */
 121         __u32 patch_version;    /*  3 patchlevel version ...                  */
 122         __u32 gvalid_words;     /*  4 Number of used words in this section    */
 123         __u32 set_uuid0;        /*  5 Raid set identifier                     */
 124         __u32 ctime;            /*  6 Creation time                           */
 125         __u32 level;            /*  7 Raid personality                        */
 126         __u32 size;             /*  8 Apparent size of each individual disk   */
 127         __u32 nr_disks;         /*  9 total disks in the raid set             */
 128         __u32 raid_disks;       /* 10 disks in a fully functional raid set    */
 129         __u32 md_minor;         /* 11 preferred MD minor device number        */
 130         __u32 not_persistent;   /* 12 does it have a persistent superblock    */
 131         __u32 set_uuid1;        /* 13 Raid set identifier #2                  */
 132         __u32 set_uuid2;        /* 14 Raid set identifier #3                  */
 133         __u32 set_uuid3;        /* 15 Raid set identifier #4                  */
 134         __u32 gstate_creserved[MD_SB_GENERIC_CONSTANT_WORDS - 16];
 135
 136         /*
 137          * Generic state information
 138          */
 139         __u32 utime;            /*  0 Superblock update time                  */
 140         __u32 state;            /*  1 State bits (clean, ...)                 */
 141         __u32 active_disks;     /*  2 Number of currently active disks        */
 142         __u32 working_disks;    /*  3 Number of working disks                 */
 143         __u32 failed_disks;     /*  4 Number of failed disks                  */
 144         __u32 spare_disks;      /*  5 Number of spare disks                   */
 145         __u32 sb_csum;          /*  6 checksum of the whole superblock        */
 146 #ifdef __BIG_ENDIAN
 147         __u32 events_hi;        /*  7 high-order of superblock update count   */
 148         __u32 events_lo;        /*  8 low-order of superblock update count    */
 149         __u32 cp_events_hi;     /*  9 high-order of checkpoint update count   */
 150         __u32 cp_events_lo;     /* 10 low-order of checkpoint update count    */
 151 #else
 152         __u32 events_lo;        /*  7 low-order of superblock update count    */
 153         __u32 events_hi;        /*  8 high-order of superblock update count   */
 154         __u32 cp_events_lo;     /*  9 low-order of checkpoint update count    */
 155         __u32 cp_events_hi;     /* 10 high-order of checkpoint update count   */
 156 #endif
 157         __u32 recovery_cp;      /* 11 recovery checkpoint sector count        */
 158         /* There are only valid for minor_version > 90 */
 159         __u64 reshape_position; /* 12,13 next address in array-space for reshape */
 160         __u32 new_level;        /* 14 new level we are reshaping to           */
 161         __u32 delta_disks;      /* 15 change in number of raid_disks          */
 162         __u32 new_layout;       /* 16 new layout                              */
 163         __u32 new_chunk;        /* 17 new chunk size (bytes)                  */
 164         __u32 gstate_sreserved[MD_SB_GENERIC_STATE_WORDS - 18];
 165
 166         /*
 167          * Personality information
 168          */
 169         __u32 layout;           /*  0 the array's physical layout             */
 170         __u32 chunk_size;       /*  1 chunk size in bytes                     */
 171         __u32 root_pv;          /*  2 LV root PV */
 172         __u32 root_block;       /*  3 LV root block */
 173         __u32 pstate_reserved[MD_SB_PERSONALITY_WORDS - 4];
 174
 175         /*
 176          * Disks information
 177          */
 178         mdp_disk_t disks[MD_SB_DISKS];
 179
 180         /*
 181          * Reserved
 182          */
 183         __u32 reserved[MD_SB_RESERVED_WORDS];
 184
 185         /*
 186          * Active descriptor
 187          */
 188         mdp_disk_t this_disk;
 189
 190 } mdp_super_t;
 191
 192 static inline __u64 md_event(mdp_super_t *sb) {
 193         __u64 ev = sb->events_hi;
 194         return (ev<<32)| sb->events_lo;
 195 }
 196
 197 /*
 198  * The version-1 superblock :
 199  * All numeric fields are little-endian.
 200  *
 201  * total size: 256 bytes plus 2 per device.
 202  *  1K allows 384 devices.
 203  */
 204 struct mdp_superblock_1 {
 205         /* constant array information - 128 bytes */
 206         __le32  magic;          /* MD_SB_MAGIC: 0xa92b4efc - little endian */
 207         __le32  major_version;  /* 1 */
 208         __le32  feature_map;    /* bit 0 set if 'bitmap_offset' is meaningful */
 209         __le32  pad0;           /* always set to 0 when writing */
 210
 211         __u8    set_uuid[16];   /* user-space generated. */
 212         char    set_name[32];   /* set and interpreted by user-space */
 213
 214         __le64  ctime;          /* lo 40 bits are seconds, top 24 are microseconds or 0*/
 215         __le32  level;          /* -4 (multipath), -1 (linear), 0,1,4,5 */
 216         __le32  layout;         /* only for raid5 and raid10 currently */
 217         __le64  size;           /* used size of component devices, in 512byte sectors */
 218
 219         __le32  chunksize;      /* in 512byte sectors */
 220         __le32  raid_disks;
 221         __le32  bitmap_offset;  /* sectors after start of superblock that bitmap starts
 222                                  * NOTE: signed, so bitmap can be before superblock
 223                                  * only meaningful of feature_map[0] is set.
 224                                  */
 225
 226         /* These are only valid with feature bit '4' */
 227         __le32  new_level;      /* new level we are reshaping to                */
 228         __le64  reshape_position;       /* next address in array-space for reshape */
 229         __le32  delta_disks;    /* change in number of raid_disks               */
 230         __le32  new_layout;     /* new layout                                   */
 231         __le32  new_chunk;      /* new chunk size (bytes)                       */
 232         __u8    pad1[128-124];  /* set to 0 when written */
 233
 234         /* constant this-device information - 64 bytes */
 235         __le64  data_offset;    /* sector start of data, often 0 */
 236         __le64  data_size;      /* sectors in this device that can be used for data */
 237         __le64  super_offset;   /* sector start of this superblock */
 238         __le64  recovery_offset;/* sectors before this offset (from data_offset) have been recovered */
 239         __le32  dev_number;     /* permanent identifier of this  device - not role in raid */
 240         __le32  cnt_corrected_read; /* number of read errors that were corrected by re-writing */
 241         __u8    device_uuid[16]; /* user-space setable, ignored by kernel */
 242         __u8    devflags;       /* per-device flags.  Only one defined...*/
 243 #define WriteMostly1    1       /* mask for writemostly flag in above */
 244         __u8    pad2[64-57];    /* set to 0 when writing */
 245
 246         /* array state information - 64 bytes */
 247         __le64  utime;          /* 40 bits second, 24 btes microseconds */
 248         __le64  events;         /* incremented when superblock updated */
 249         __le64  resync_offset;  /* data before this offset (from data_offset) known to be in sync */
 250         __le32  sb_csum;        /* checksum upto devs[max_dev] */
 251         __le32  max_dev;        /* size of devs[] array to consider */
 252         __u8    pad3[64-32];    /* set to 0 when writing */
 253
 254         /* device state information. Indexed by dev_number.
 255          * 2 bytes per device
 256          * Note there are no per-device state flags. State information is rolled
 257          * into the 'roles' value.  If a device is spare or faulty, then it doesn't
 258          * have a meaningful role.
 259          */
 260         __le16  dev_roles[0];   /* role in array, or 0xffff for a spare, or 0xfffe for faulty */
 261 };
 262
 263 /* feature_map bits */
 264 #define MD_FEATURE_BITMAP_OFFSET        1
 265 #define MD_FEATURE_RECOVERY_OFFSET      2 /* recovery_offset is present and
 266                                            * must be honoured
 267                                            */
 268 #define MD_FEATURE_RESHAPE_ACTIVE       4
 269
 270 #define MD_FEATURE_ALL                  (1|2|4)
 271
 272 #endif
 273