1 | /* |
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2 | * sparse.c --- find the groups in an ext2 filesystem with metadata backups |
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3 | * |
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4 | * Copyright (C) 1993, 1994, 1995, 1996 Theodore Ts'o. |
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5 | * Copyright (C) 2002 Andreas Dilger. |
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6 | * |
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7 | * %Begin-Header% |
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8 | * This file may be redistributed under the terms of the GNU Public |
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9 | * License. |
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10 | * %End-Header% |
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11 | */ |
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12 | |
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13 | #include <stdio.h> |
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14 | |
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15 | #include "ext2_fs.h" |
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16 | #include "ext2fsP.h" |
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17 | |
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18 | static int test_root(int a, int b) |
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19 | { |
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20 | if (a == 0) |
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21 | return 1; |
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22 | while (1) { |
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23 | if (a == 1) |
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24 | return 1; |
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25 | if (a % b) |
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26 | return 0; |
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27 | a = a / b; |
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28 | } |
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29 | } |
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30 | |
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31 | int ext2fs_bg_has_super(ext2_filsys fs, int group_block) |
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32 | { |
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33 | if (!(fs->super->s_feature_ro_compat & |
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34 | EXT2_FEATURE_RO_COMPAT_SPARSE_SUPER)) |
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35 | return 1; |
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36 | |
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37 | if (test_root(group_block, 3) || (test_root(group_block, 5)) || |
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38 | test_root(group_block, 7)) |
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39 | return 1; |
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40 | |
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41 | return 0; |
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42 | } |
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43 | |
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44 | /* |
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45 | * Iterate through the groups which hold BACKUP superblock/GDT copies in an |
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46 | * ext3 filesystem. The counters should be initialized to 1, 5, and 7 before |
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47 | * calling this for the first time. In a sparse filesystem it will be the |
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48 | * sequence of powers of 3, 5, and 7: 1, 3, 5, 7, 9, 25, 27, 49, 81, ... |
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49 | * For a non-sparse filesystem it will be every group: 1, 2, 3, 4, ... |
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50 | */ |
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51 | unsigned int ext2fs_list_backups(ext2_filsys fs, unsigned int *three, |
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52 | unsigned int *five, unsigned int *seven) |
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53 | { |
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54 | unsigned int *min = three; |
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55 | int mult = 3; |
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56 | unsigned int ret; |
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57 | |
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58 | if (!(fs->super->s_feature_ro_compat & |
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59 | EXT2_FEATURE_RO_COMPAT_SPARSE_SUPER)) { |
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60 | ret = *min; |
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61 | *min += 1; |
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62 | return ret; |
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63 | } |
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64 | |
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65 | if (*five < *min) { |
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66 | min = five; |
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67 | mult = 5; |
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68 | } |
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69 | if (*seven < *min) { |
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70 | min = seven; |
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71 | mult = 7; |
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72 | } |
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73 | |
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74 | ret = *min; |
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75 | *min *= mult; |
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76 | |
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77 | return ret; |
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78 | } |
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