include/zfs/uberblock_impl.h

   1 /*
   2  *  GRUB  --  GRand Unified Bootloader
   3  *  Copyright (C) 1999,2000,2001,2002,2003,2004  Free Software Foundation, Inc.
   4  *
   5  * SPDX-License-Identifier:     GPL-2.0+
   6  */
   7 /*
   8  * Copyright 2007 Sun Microsystems, Inc.  All rights reserved.
   9  * Use is subject to license terms.
  10  */
  11
  12 #ifndef _SYS_UBERBLOCK_IMPL_H
  13 #define _SYS_UBERBLOCK_IMPL_H
  14
  15 #define UBMAX(a, b) ((a) > (b) ? (a) : (b))
  16
  17 /*
  18  * The uberblock version is incremented whenever an incompatible on-disk
  19  * format change is made to the SPA, DMU, or ZAP.
  20  *
  21  * Note: the first two fields should never be moved.  When a storage pool
  22  * is opened, the uberblock must be read off the disk before the version
  23  * can be checked.      If the ub_version field is moved, we may not detect
  24  * version mismatch.  If the ub_magic field is moved, applications that
  25  * expect the magic number in the first word won't work.
  26  */
  27 #define UBERBLOCK_MAGIC         0x00bab10c              /* oo-ba-bloc!  */
  28 #define UBERBLOCK_SHIFT         10                      /* up to 1K     */
  29
  30 typedef struct uberblock {
  31         uint64_t        ub_magic;       /* UBERBLOCK_MAGIC              */
  32         uint64_t        ub_version;     /* ZFS_VERSION                  */
  33         uint64_t        ub_txg;         /* txg of last sync             */
  34         uint64_t        ub_guid_sum;    /* sum of all vdev guids        */
  35         uint64_t        ub_timestamp;   /* UTC time of last sync        */
  36         blkptr_t        ub_rootbp;      /* MOS objset_phys_t            */
  37 } uberblock_t;
  38
  39 #define VDEV_UBERBLOCK_SHIFT(as)        UBMAX(as, UBERBLOCK_SHIFT)
  40 #define UBERBLOCK_SIZE(as)              (1ULL << VDEV_UBERBLOCK_SHIFT(as))
  41
  42 /* Number of uberblocks that can fit in the ring at a given ashift */
  43 #define UBERBLOCK_COUNT(as) (VDEV_UBERBLOCK_RING >> VDEV_UBERBLOCK_SHIFT(as))
  44
  45 #endif  /* _SYS_UBERBLOCK_IMPL_H */