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1 //
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2 // File descriptors
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3 //
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4
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5 #include "types.h"
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6 #include "defs.h"
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7 #include "param.h"
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8 #include "fs.h"
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9 #include "file.h"
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10 #include "spinlock.h"
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11
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12 struct devsw devsw[NDEV];
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13 struct {
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14 struct spinlock lock;
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15 struct file file[NFILE];
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16 } ftable;
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17
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18 void fileinit (void)
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19 {
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20 initlock(&ftable.lock, "ftable");
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21 }
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22
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23 // Allocate a file structure.
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24 struct file* filealloc (void)
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25 {
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26 struct file *f;
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27
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28 acquire(&ftable.lock);
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29
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30 for (f = ftable.file; f < ftable.file + NFILE; f++) {
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31 if (f->ref == 0) {
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32 f->ref = 1;
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33 release(&ftable.lock);
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34 return f;
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35 }
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36 }
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37
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38 release(&ftable.lock);
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39 return 0;
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40 }
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41
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42 // Increment ref count for file f.
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43 struct file* filedup (struct file *f)
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44 {
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45 acquire(&ftable.lock);
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46
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47 if (f->ref < 1) {
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48 panic("filedup");
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49 }
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50
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51 f->ref++;
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52 release(&ftable.lock);
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53 return f;
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54 }
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55
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56 // Close file f. (Decrement ref count, close when reaches 0.)
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57 void fileclose (struct file *f)
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58 {
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59 struct file ff;
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60
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61 acquire(&ftable.lock);
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62
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63 if (f->ref < 1) {
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64 panic("fileclose");
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65 }
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66
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67 if (--f->ref > 0) {
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68 release(&ftable.lock);
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69 return;
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70 }
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71
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72 ff = *f;
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73 f->ref = 0;
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74 f->type = FD_NONE;
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75 release(&ftable.lock);
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76
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77 if (ff.type == FD_PIPE) {
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78 pipeclose(ff.pipe, ff.writable);
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79
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80 } else if (ff.type == FD_INODE) {
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81 begin_trans();
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82 iput(ff.ip);
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83 commit_trans();
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84 }
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85 }
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86
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87 // Get metadata about file f.
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88 int filestat (struct file *f, struct stat *st)
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89 {
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90 if (f->type == FD_INODE) {
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91 ilock(f->ip);
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92 stati(f->ip, st);
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93 iunlock(f->ip);
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94
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95 return 0;
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96 }
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97
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98 return -1;
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99 }
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100
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101 // Read from file f.
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102 int fileread (struct file *f, char *addr, int n)
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103 {
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104 int r;
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105
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106 if (f->readable == 0) {
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107 return -1;
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108 }
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109
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110 if (f->type == FD_PIPE) {
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111 return piperead(f->pipe, addr, n);
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112 }
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113
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114 if (f->type == FD_INODE) {
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115 ilock(f->ip);
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116
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117 if ((r = readi(f->ip, addr, f->off, n)) > 0) {
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118 f->off += r;
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119 }
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120
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121 iunlock(f->ip);
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122
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123 return r;
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124 }
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125
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126 panic("fileread");
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127 }
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128
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129 //PAGEBREAK!
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130 // Write to file f.
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131 int filewrite (struct file *f, char *addr, int n)
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132 {
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133 int r;
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134 int i;
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135 int max;
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136 int n1;
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137
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138 if (f->writable == 0) {
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139 return -1;
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140 }
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141
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142 if (f->type == FD_PIPE) {
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143 return pipewrite(f->pipe, addr, n);
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144 }
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145
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146 if (f->type == FD_INODE) {
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147 // write a few blocks at a time to avoid exceeding
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148 // the maximum log transaction size, including
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149 // i-node, indirect block, allocation blocks,
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150 // and 2 blocks of slop for non-aligned writes.
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151 // this really belongs lower down, since writei()
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152 // might be writing a device like the console.
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153 max = ((LOGSIZE - 1 - 1 - 2) / 2) * 512;
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154 i = 0;
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155
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156 while (i < n) {
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157 n1 = n - i;
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158
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159 if (n1 > max) {
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160 n1 = max;
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161 }
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162
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163 begin_trans();
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164 ilock(f->ip);
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165
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166 if ((r = writei(f->ip, addr + i, f->off, n1)) > 0) {
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167 f->off += r;
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168 }
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169
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170 iunlock(f->ip);
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171 commit_trans();
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172
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173 if (r < 0) {
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174 break;
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175 }
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176
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177 if (r != n1) {
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178 panic("short filewrite");
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179 }
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180
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181 i += r;
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182 }
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183
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184 return i == n ? n : -1;
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185 }
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186
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187 panic("filewrite");
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188 }
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189
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