1 // On-disk file system format.
2 // Both the kernel and user programs use this header file.
3
4 #define ROOTINO 1 // root i-number
5 #define BSIZE 1024 // block size
6
7 // Disk layout:
8 // [ boot block | super block | log | inode blocks |
9 // free bit map | data blocks]
10 //
11 // mkfs computes the super block and builds an initial file system. The
12 // super block describes the disk layout:
13 struct superblock {
14 uint magic; // Must be FSMAGIC
15 uint size; // Size of file system image (blocks)
16 uint nblocks; // Number of data blocks
17 uint ninodes; // Number of inodes.
18 uint nlog; // Number of log blocks
19 uint logstart; // Block number of first log block
20 uint inodestart; // Block number of first inode block
21 uint bmapstart; // Block number of first free map block
22 };
23
24 #define FSMAGIC 0x10203040
25
26 #define NDIRECT 12
27 #define NINDIRECT (BSIZE / sizeof(uint))
28 #define MAXFILE (NDIRECT + NINDIRECT)
29 #define NLINK_MAX 32767 // nlink is a short; refuse links past its maximum
30
31 // On-disk inode structure
32 struct dinode {
33 short type; // File type
34 short major; // Major device number (T_DEVICE only)
35 short minor; // Minor device number (T_DEVICE only)
36 short nlink; // Number of links to inode in file system
37 uint size; // Size of file (bytes)
38 uint addrs[NDIRECT + 1]; // Data block addresses
39 };
40
41 // Inodes per block.
42 #define IPB (BSIZE / sizeof(struct dinode))
43
44 // Block containing inode i
45 #define IBLOCK(i, sb) ((i) / IPB + sb.inodestart)
46
47 // Bitmap bits per block
48 #define BPB (BSIZE * 8)
49
50 // Block of free map containing bit for block b
51 #define BBLOCK(b, sb) ((b) / BPB + sb.bmapstart)
52
53 // Directory is a file containing a sequence of dirent structures.
54 #define DIRSIZ 14
55
56 // The name field may have DIRSIZ characters and not end in a NUL
57 // character.
58 struct dirent {
59 ushort inum;
60 char name[DIRSIZ] __attribute__((nonstring));
61 };