1 // On-disk file system format. 2 // This header is shared between kernel and user space. 3 4 // Block 0 is unused. 5 // Block 1 is super block. 6 // Inodes start at block 2. 7 8 #define BSIZE 512 // block size 9 10 // File system super block 11 struct superblock { 12 uint size; // Size of file system image (blocks) 13 uint nblocks; // Number of data blocks 14 uint ninodes; // Number of inodes. 15 }; 16 17 #define NADDRS (NDIRECT+1) 18 #define NDIRECT 12 19 #define INDIRECT 12 20 #define NINDIRECT (BSIZE / sizeof(uint)) 21 #define MAXFILE (NDIRECT + NINDIRECT) 22 23 // On-disk inode structure 24 struct dinode { 25 short type; // File type 26 short major; // Major device number (T_DEV only) 27 short minor; // Minor device number (T_DEV only) 28 short nlink; // Number of links to inode in file system 29 uint size; // Size of file (bytes) 30 uint addrs[NADDRS]; // Data block addresses 31 }; 32 33 #define T_DIR 1 // Directory 34 #define T_FILE 2 // File 35 #define T_DEV 3 // Special device 36 37 // Inodes per block. 38 #define IPB (BSIZE / sizeof(struct dinode)) 39 40 // Block containing inode i 41 #define IBLOCK(i) ((i) / IPB + 2) 42 43 // Bitmap bits per block 44 #define BPB (BSIZE*8) 45 46 // Block containing bit for block b 47 #define BBLOCK(b, ninodes) (b/BPB + (ninodes)/IPB + 3) 48 49 // PAGEBREAK: 10 50 // Directory is a file containing a sequence of dirent structures. 51 #define DIRSIZ 14 52 53 struct dirent { 54 ushort inum; 55 char name[DIRSIZ]; 56 }; 57 58 extern uint rootdev; // Device number of root file system 59 60