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