1 | /*
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2 | * fileio.c --- Simple file I/O routines
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3 | *
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4 | * Copyright (C) 1997 Theodore Ts'o.
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5 | *
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6 | * %Begin-Header%
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7 | * This file may be redistributed under the terms of the GNU Public
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8 | * License.
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9 | * %End-Header%
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10 | */
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11 |
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12 | #include <stdio.h>
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13 | #include <string.h>
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14 | #if HAVE_UNISTD_H
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15 | #include <unistd.h>
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16 | #endif
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17 |
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18 | #include "ext2_fs.h"
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19 | #include "ext2fs.h"
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20 |
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21 | struct ext2_file {
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22 | errcode_t magic;
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23 | ext2_filsys fs;
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24 | ext2_ino_t ino;
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25 | struct ext2_inode inode;
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26 | int flags;
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27 | __u64 pos;
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28 | blk_t blockno;
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29 | blk_t physblock;
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30 | char *buf;
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31 | };
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32 |
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33 | #define BMAP_BUFFER (file->buf + fs->blocksize)
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34 |
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35 | errcode_t ext2fs_file_open2(ext2_filsys fs, ext2_ino_t ino,
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36 | struct ext2_inode *inode,
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37 | int flags, ext2_file_t *ret)
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38 | {
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39 | ext2_file_t file;
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40 | errcode_t retval;
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41 |
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42 | /*
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43 | * Don't let caller create or open a file for writing if the
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44 | * filesystem is read-only.
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45 | */
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46 | if ((flags & (EXT2_FILE_WRITE | EXT2_FILE_CREATE)) &&
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47 | !(fs->flags & EXT2_FLAG_RW))
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48 | return EXT2_ET_RO_FILSYS;
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49 |
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50 | retval = ext2fs_get_mem(sizeof(struct ext2_file), &file);
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51 | if (retval)
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52 | return retval;
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53 |
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54 | memset(file, 0, sizeof(struct ext2_file));
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55 | file->magic = EXT2_ET_MAGIC_EXT2_FILE;
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56 | file->fs = fs;
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57 | file->ino = ino;
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58 | file->flags = flags & EXT2_FILE_MASK;
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59 |
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60 | if (inode) {
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61 | memcpy(&file->inode, inode, sizeof(struct ext2_inode));
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62 | } else {
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63 | retval = ext2fs_read_inode(fs, ino, &file->inode);
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64 | if (retval)
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65 | goto fail;
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66 | }
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67 |
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68 | retval = ext2fs_get_mem(fs->blocksize * 3, &file->buf);
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69 | if (retval)
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70 | goto fail;
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71 |
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72 | *ret = file;
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73 | return 0;
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74 |
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75 | fail:
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76 | ext2fs_free_mem(&file->buf);
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77 | ext2fs_free_mem(&file);
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78 | return retval;
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79 | }
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80 |
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81 | errcode_t ext2fs_file_open(ext2_filsys fs, ext2_ino_t ino,
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82 | int flags, ext2_file_t *ret)
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83 | {
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84 | return ext2fs_file_open2(fs, ino, NULL, flags, ret);
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85 | }
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86 |
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87 | /*
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88 | * This function returns the filesystem handle of a file from the structure
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89 | */
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90 | ext2_filsys ext2fs_file_get_fs(ext2_file_t file)
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91 | {
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92 | if (file->magic != EXT2_ET_MAGIC_EXT2_FILE)
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93 | return 0;
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94 | return file->fs;
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95 | }
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96 |
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97 | /*
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98 | * This function flushes the dirty block buffer out to disk if
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99 | * necessary.
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100 | */
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101 | errcode_t ext2fs_file_flush(ext2_file_t file)
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102 | {
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103 | errcode_t retval;
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104 | ext2_filsys fs;
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105 |
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106 | EXT2_CHECK_MAGIC(file, EXT2_ET_MAGIC_EXT2_FILE);
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107 | fs = file->fs;
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108 |
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109 | if (!(file->flags & EXT2_FILE_BUF_VALID) ||
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110 | !(file->flags & EXT2_FILE_BUF_DIRTY))
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111 | return 0;
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112 |
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113 | /*
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114 | * OK, the physical block hasn't been allocated yet.
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115 | * Allocate it.
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116 | */
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117 | if (!file->physblock) {
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118 | retval = ext2fs_bmap(fs, file->ino, &file->inode,
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119 | BMAP_BUFFER, file->ino ? BMAP_ALLOC : 0,
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120 | file->blockno, &file->physblock);
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121 | if (retval)
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122 | return retval;
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123 | }
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124 |
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125 | retval = io_channel_write_blk(fs->io, file->physblock,
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126 | 1, file->buf);
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127 | if (retval)
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128 | return retval;
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129 |
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130 | file->flags &= ~EXT2_FILE_BUF_DIRTY;
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131 |
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132 | return retval;
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133 | }
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134 |
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135 | /*
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136 | * This function synchronizes the file's block buffer and the current
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137 | * file position, possibly invalidating block buffer if necessary
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138 | */
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139 | static errcode_t sync_buffer_position(ext2_file_t file)
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140 | {
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141 | blk_t b;
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142 | errcode_t retval;
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143 |
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144 | b = file->pos / file->fs->blocksize;
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145 | if (b != file->blockno) {
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146 | retval = ext2fs_file_flush(file);
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147 | if (retval)
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148 | return retval;
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149 | file->flags &= ~EXT2_FILE_BUF_VALID;
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150 | }
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151 | file->blockno = b;
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152 | return 0;
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153 | }
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154 |
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155 | /*
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156 | * This function loads the file's block buffer with valid data from
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157 | * the disk as necessary.
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158 | *
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159 | * If dontfill is true, then skip initializing the buffer since we're
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160 | * going to be replacing its entire contents anyway. If set, then the
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161 | * function basically only sets file->physblock and EXT2_FILE_BUF_VALID
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162 | */
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163 | #define DONTFILL 1
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164 | static errcode_t load_buffer(ext2_file_t file, int dontfill)
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165 | {
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166 | ext2_filsys fs = file->fs;
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167 | errcode_t retval;
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168 |
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169 | if (!(file->flags & EXT2_FILE_BUF_VALID)) {
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170 | retval = ext2fs_bmap(fs, file->ino, &file->inode,
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171 | BMAP_BUFFER, 0, file->blockno,
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172 | &file->physblock);
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173 | if (retval)
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174 | return retval;
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175 | if (!dontfill) {
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176 | if (file->physblock) {
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177 | retval = io_channel_read_blk(fs->io,
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178 | file->physblock,
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179 | 1, file->buf);
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180 | if (retval)
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181 | return retval;
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182 | } else
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183 | memset(file->buf, 0, fs->blocksize);
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184 | }
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185 | file->flags |= EXT2_FILE_BUF_VALID;
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186 | }
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187 | return 0;
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188 | }
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189 |
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190 |
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191 | errcode_t ext2fs_file_close(ext2_file_t file)
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192 | {
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193 | errcode_t retval;
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194 |
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195 | EXT2_CHECK_MAGIC(file, EXT2_ET_MAGIC_EXT2_FILE);
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196 |
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197 | retval = ext2fs_file_flush(file);
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198 |
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199 | ext2fs_free_mem(&file->buf);
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200 | ext2fs_free_mem(&file);
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201 |
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202 | return retval;
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203 | }
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204 |
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205 |
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206 | errcode_t ext2fs_file_read(ext2_file_t file, void *buf,
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207 | unsigned int wanted, unsigned int *got)
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208 | {
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209 | ext2_filsys fs;
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210 | errcode_t retval = 0;
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211 | unsigned int start, c, count = 0;
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212 | __u64 left;
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213 | char *ptr = (char *) buf;
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214 |
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215 | EXT2_CHECK_MAGIC(file, EXT2_ET_MAGIC_EXT2_FILE);
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216 | fs = file->fs;
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217 |
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218 | while ((file->pos < EXT2_I_SIZE(&file->inode)) && (wanted > 0)) {
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219 | retval = sync_buffer_position(file);
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220 | if (retval)
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221 | goto fail;
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222 | retval = load_buffer(file, 0);
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223 | if (retval)
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224 | goto fail;
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225 |
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226 | start = file->pos % fs->blocksize;
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227 | c = fs->blocksize - start;
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228 | if (c > wanted)
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229 | c = wanted;
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230 | left = EXT2_I_SIZE(&file->inode) - file->pos ;
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231 | if (c > left)
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232 | c = left;
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233 |
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234 | memcpy(ptr, file->buf+start, c);
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235 | file->pos += c;
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236 | ptr += c;
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237 | count += c;
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238 | wanted -= c;
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239 | }
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240 |
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241 | fail:
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242 | if (got)
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243 | *got = count;
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244 | return retval;
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245 | }
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246 |
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247 |
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248 | errcode_t ext2fs_file_write(ext2_file_t file, const void *buf,
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249 | unsigned int nbytes, unsigned int *written)
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250 | {
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251 | ext2_filsys fs;
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252 | errcode_t retval = 0;
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253 | unsigned int start, c, count = 0;
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254 | const char *ptr = (const char *) buf;
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255 |
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256 | EXT2_CHECK_MAGIC(file, EXT2_ET_MAGIC_EXT2_FILE);
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257 | fs = file->fs;
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258 |
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259 | if (!(file->flags & EXT2_FILE_WRITE))
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260 | return EXT2_ET_FILE_RO;
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261 |
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262 | while (nbytes > 0) {
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263 | retval = sync_buffer_position(file);
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264 | if (retval)
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265 | goto fail;
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266 |
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267 | start = file->pos % fs->blocksize;
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268 | c = fs->blocksize - start;
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269 | if (c > nbytes)
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270 | c = nbytes;
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271 |
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272 | /*
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273 | * We only need to do a read-modify-update cycle if
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274 | * we're doing a partial write.
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275 | */
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276 | retval = load_buffer(file, (c == fs->blocksize));
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277 | if (retval)
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278 | goto fail;
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279 |
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280 | file->flags |= EXT2_FILE_BUF_DIRTY;
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281 | memcpy(file->buf+start, ptr, c);
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282 | file->pos += c;
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283 | ptr += c;
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284 | count += c;
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285 | nbytes -= c;
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286 | }
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287 |
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288 | fail:
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289 | if (written)
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290 | *written = count;
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291 | return retval;
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292 | }
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293 |
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294 | errcode_t ext2fs_file_llseek(ext2_file_t file, __u64 offset,
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295 | int whence, __u64 *ret_pos)
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296 | {
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297 | EXT2_CHECK_MAGIC(file, EXT2_ET_MAGIC_EXT2_FILE);
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298 |
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299 | if (whence == EXT2_SEEK_SET)
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300 | file->pos = offset;
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301 | else if (whence == EXT2_SEEK_CUR)
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302 | file->pos += offset;
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303 | else if (whence == EXT2_SEEK_END)
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304 | file->pos = EXT2_I_SIZE(&file->inode) + offset;
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305 | else
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306 | return EXT2_ET_INVALID_ARGUMENT;
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307 |
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308 | if (ret_pos)
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309 | *ret_pos = file->pos;
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310 |
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311 | return 0;
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312 | }
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313 |
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314 | errcode_t ext2fs_file_lseek(ext2_file_t file, ext2_off_t offset,
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315 | int whence, ext2_off_t *ret_pos)
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316 | {
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317 | __u64 loffset, ret_loffset;
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318 | errcode_t retval;
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319 |
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320 | loffset = offset;
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321 | retval = ext2fs_file_llseek(file, loffset, whence, &ret_loffset);
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322 | if (ret_pos)
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323 | *ret_pos = (ext2_off_t) ret_loffset;
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324 | return retval;
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325 | }
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326 |
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327 |
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328 | /*
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329 | * This function returns the size of the file, according to the inode
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330 | */
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331 | errcode_t ext2fs_file_get_lsize(ext2_file_t file, __u64 *ret_size)
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332 | {
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333 | if (file->magic != EXT2_ET_MAGIC_EXT2_FILE)
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334 | return EXT2_ET_MAGIC_EXT2_FILE;
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335 | *ret_size = EXT2_I_SIZE(&file->inode);
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336 | return 0;
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337 | }
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338 |
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339 | /*
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340 | * This function returns the size of the file, according to the inode
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341 | */
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342 | ext2_off_t ext2fs_file_get_size(ext2_file_t file)
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343 | {
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344 | __u64 size;
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345 |
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346 | if (ext2fs_file_get_lsize(file, &size))
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347 | return 0;
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348 | if ((size >> 32) != 0)
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349 | return 0;
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350 | return size;
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351 | }
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352 |
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353 | /*
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354 | * This function sets the size of the file, truncating it if necessary
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355 | *
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356 | * XXX still need to call truncate
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357 | */
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358 | errcode_t ext2fs_file_set_size(ext2_file_t file, ext2_off_t size)
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359 | {
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360 | errcode_t retval;
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361 | EXT2_CHECK_MAGIC(file, EXT2_ET_MAGIC_EXT2_FILE);
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362 |
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363 | file->inode.i_size = size;
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364 | file->inode.i_size_high = 0;
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365 | if (file->ino) {
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366 | retval = ext2fs_write_inode(file->fs, file->ino, &file->inode);
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367 | if (retval)
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368 | return retval;
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369 | }
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370 |
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371 | /*
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372 | * XXX truncate inode if necessary
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373 | */
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374 |
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375 | return 0;
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376 | }
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