1 #ifndef _MKFS_MFS_SUPER_H__ 2 #define _MKFS_MFS_SUPER_H__ 3 4 /* Super block table. The entry holds information about the sizes of the bit 5 * maps and inodes. The s_ninodes field gives the number of inodes available 6 * for files and directories, including the root directory. Inode 0 is 7 * on the disk, but not used. Thus s_ninodes = 4 means that 5 bits will be 8 * used in the bit map, bit 0, which is always 1 and not used, and bits 1-4 9 * for files and directories. The disk layout is: 10 * 11 * Item # blocks 12 * boot block 1 13 * super block 1 (offset 1kB) 14 * inode map s_imap_blocks 15 * zone map s_zmap_blocks 16 * inodes (s_ninodes + 'inodes per block' - 1)/'inodes per block' 17 * unused whatever is needed to fill out the current zone 18 * data zones (s_zones - s_firstdatazone) << s_log_zone_size 19 */ 20 21 struct super_block { 22 uint32_t s_ninodes; /* # usable inodes on the minor device */ 23 uint16_t s_nzones; /* total device size, including bit maps etc */ 24 int16_t s_imap_blocks; /* # of blocks used by inode bit map */ 25 int16_t s_zmap_blocks; /* # of blocks used by zone bit map */ 26 uint16_t s_firstdatazone_old; /* number of first data zone (small) */ 27 uint16_t s_log_zone_size; /* log2 of blocks/zone */ 28 uint16_t s_flags; /* FS state flags */ 29 int32_t s_max_size; /* maximum file size on this device */ 30 uint32_t s_zones; /* number of zones (replaces s_nzones in V2) */ 31 int16_t s_magic; /* magic number to recognize super-blocks */ 32 33 /* The following items are valid on disk only for V3 and above */ 34 35 int16_t s_pad2; /* try to avoid compiler-dependent padding */ 36 /* The block size in bytes. Minimum MIN_BLOCK SIZE. SECTOR_SIZE multiple.*/ 37 uint16_t s_block_size; /* block size in bytes. */ 38 int8_t s_disk_version; /* filesystem format sub-version */ 39 40 /* The following items are only used when the super_block is in memory. 41 * If this ever changes, i.e. more fields after s_disk_version has to go to 42 * disk, update LAST_ONDISK_FIELD in servers/mfs/super.c as that controls 43 * which part of the struct is copied to and from disk. 44 */ 45 /* XXX padding inserted here... */ 46 47 unsigned s_inodes_per_block; /* precalculated from magic number */ 48 uint32_t s_firstdatazone; /* number of first data zone (big) */ 49 } superblock; 50 51 /* s_flags contents; undefined flags are guaranteed to be zero on disk 52 * (not counting future versions of mfs setting them!) 53 */ 54 #define MFSFLAG_CLEAN (1L << 0) /* 0: dirty; 1: FS was unmounted cleanly */ 55 56 /* Future compatability (or at least, graceful failure): 57 * if any of these bits are on, and the MFS or fsck 58 * implementation doesn't understand them, do not mount/fsck 59 * the FS. 60 */ 61 #define MFSFLAG_MANDATORY_MASK 0xff00 62 63 /* The block size should be registered on disk, even 64 * multiple. If V1 or V2 filesystem, this should be 65 * initialised to STATIC_BLOCK_SIZE. 66 */ 67 #define MFS_SUPER_BLOCK_SIZE s_block_size 68 69 /* To keep the super block on disk clean, the MFS server only read/write up to 70 * and including this field: 71 */ 72 #define LAST_ONDISK_FIELD s_disk_version 73 74 #endif 75