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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
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19 fileinit(void)
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20 {
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21 memset(&ftable, 0, sizeof(ftable));
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22 initlock(&ftable.lock, "ftable");
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23 }
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24
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25 // Allocate a file structure.
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26 struct file*
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27 filealloc(void)
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28 {
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29 struct file *f;
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30
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31 acquire(&ftable.lock);
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32 for(f = ftable.file; f < ftable.file + NFILE; f++){
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33 if(f->ref == 0){
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34 f->ref = 1;
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35 release(&ftable.lock);
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36 return f;
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37 }
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38 }
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39 release(&ftable.lock);
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40 return 0;
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41 }
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42
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43 // Increment ref count for file f.
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44 struct file*
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45 filedup(struct file *f)
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46 {
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47 acquire(&ftable.lock);
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48 if(f->ref < 1)
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49 panic("filedup");
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50 f->ref++;
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51 release(&ftable.lock);
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52 return f;
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53 }
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54
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55 // Close file f. (Decrement ref count, close when reaches 0.)
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56 void
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57 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 if(f->ref < 1)
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63 panic("fileclose");
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64 if(--f->ref > 0){
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65 release(&ftable.lock);
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66 return;
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67 }
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68 ff = *f;
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69 f->ref = 0;
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70 f->type = FD_NONE;
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71 release(&ftable.lock);
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72
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73 if(ff.type == FD_PIPE)
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74 pipeclose(ff.pipe, ff.writable);
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75 else if(ff.type == FD_INODE){
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76 begin_trans();
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77 iput(ff.ip);
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78 commit_trans();
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79 }
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80 }
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81
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82 // Get metadata about file f.
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83 int
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84 filestat(struct file *f, struct stat *st)
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85 {
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86 if(f->type == FD_INODE){
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87 ilock(f->ip);
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88 stati(f->ip, st);
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89 iunlock(f->ip);
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90 return 0;
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91 }
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92 return -1;
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93 }
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94
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95 // Read from file f.
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96 int
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97 fileread(struct file *f, char *addr, int n)
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98 {
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99 int r;
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100
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101 if(f->readable == 0)
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102 return -1;
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103 if(f->type == FD_PIPE)
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104 return piperead(f->pipe, addr, n);
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105 if(f->type == FD_INODE){
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106 ilock(f->ip);
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107 //cprintf("inside fileread\n");
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108 if((r = readi(f->ip, addr, f->off, n)) > 0)
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109 f->off += r;
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110 //cprintf("inside fileread: after readi rv=%x\n", r);
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111 iunlock(f->ip);
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112 return r;
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113 }
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114 panic("fileread");
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115 return -1;
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116 }
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117
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118 //PAGEBREAK!
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119 // Write to file f.
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120 int
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121 filewrite(struct file *f, char *addr, int n)
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122 {
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123 int r;
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124
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125 if(f->writable == 0)
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126 return -1;
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127 //cprintf("inside filewrite\n");
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128 if(f->type == FD_PIPE)
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129 return pipewrite(f->pipe, addr, n);
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130 if(f->type == FD_INODE){
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131 // write a few blocks at a time to avoid exceeding
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132 // the maximum log transaction size, including
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133 // i-node, indirect block, allocation blocks,
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134 // and 2 blocks of slop for non-aligned writes.
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135 // this really belongs lower down, since writei()
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136 // might be writing a device like the console.
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137 int max = ((LOGSIZE-1-1-2) / 2) * 512;
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138 int i = 0;
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139 while(i < n){
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140 int n1 = n - i;
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141 if(n1 > max)
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142 n1 = max;
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143
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144 begin_trans();
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145 ilock(f->ip);
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146 if ((r = writei(f->ip, addr + i, f->off, n1)) > 0)
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147 f->off += r;
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148 iunlock(f->ip);
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149 commit_trans();
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150
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151 if(r < 0)
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152 break;
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153 if(r != n1)
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154 panic("short filewrite");
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155 i += r;
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156 }
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157 return i == n ? n : -1;
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158 }
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159 panic("filewrite");
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160 return -1;
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161 }
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162
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