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2593 | jermar | 1 | /* |
2 | * Copyright (c) 2007 Jakub Jermar |
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3 | * All rights reserved. |
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4 | * |
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5 | * Redistribution and use in source and binary forms, with or without |
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6 | * modification, are permitted provided that the following conditions |
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7 | * are met: |
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8 | * |
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9 | * - Redistributions of source code must retain the above copyright |
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10 | * notice, this list of conditions and the following disclaimer. |
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11 | * - Redistributions in binary form must reproduce the above copyright |
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12 | * notice, this list of conditions and the following disclaimer in the |
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13 | * documentation and/or other materials provided with the distribution. |
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14 | * - The name of the author may not be used to endorse or promote products |
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15 | * derived from this software without specific prior written permission. |
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16 | * |
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17 | * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR |
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18 | * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES |
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19 | * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. |
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20 | * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, |
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21 | * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT |
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22 | * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, |
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23 | * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY |
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24 | * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT |
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25 | * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF |
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26 | * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
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27 | */ |
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28 | |||
29 | /** @addtogroup fs |
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30 | * @{ |
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31 | */ |
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32 | |||
33 | /** |
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34 | * @file vfs_file.c |
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35 | * @brief Various operations on files have their home in this file. |
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36 | */ |
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37 | |||
38 | #include <errno.h> |
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39 | #include <stdlib.h> |
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40 | #include <string.h> |
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41 | #include <assert.h> |
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42 | #include <bool.h> |
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43 | #include "vfs.h" |
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44 | |||
45 | /** |
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46 | * This is a per-connection table of open files. |
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47 | * Our assumption is that each client opens only one connection and therefore |
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48 | * there is one table of open files per task. However, this may not be the case |
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49 | * and the client can open more connections to VFS. In that case, there will be |
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50 | * several tables and several file handle name spaces per task. Besides of this, |
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51 | * the functionality will stay unchanged. So unless the client knows what it is |
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52 | * doing, it should open one connection to VFS only. |
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53 | * |
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54 | * Allocation of the open files table is deferred until the client makes the |
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55 | * first VFS_OPEN operation. |
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56 | * |
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57 | * This resource being per-connection and, in the first place, per-fibril, we |
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58 | * don't need to protect it by a futex. |
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59 | */ |
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60 | __thread vfs_file_t **files = NULL; |
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61 | |||
62 | /** Initialize the table of open files. */ |
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63 | bool vfs_files_init(void) |
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64 | { |
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65 | if (!files) { |
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66 | files = malloc(MAX_OPEN_FILES * sizeof(vfs_file_t *)); |
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67 | if (!files) |
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68 | return false; |
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69 | memset(files, 0, MAX_OPEN_FILES * sizeof(vfs_file_t *)); |
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70 | } |
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71 | return true; |
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72 | } |
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73 | |||
74 | /** Allocate a file descriptor. |
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75 | * |
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76 | * @return First available file descriptor or a negative error |
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77 | * code. |
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78 | */ |
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79 | int vfs_fd_alloc(void) |
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80 | { |
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81 | int i; |
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82 | |||
83 | for (i = 0; i < MAX_OPEN_FILES; i++) { |
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84 | if (!files[i]) { |
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85 | files[i] = (vfs_file_t *) malloc(sizeof(vfs_file_t)); |
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86 | if (!files[i]) |
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87 | return ENOMEM; |
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88 | memset(files[i], 0, sizeof(vfs_file_t)); |
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2683 | jermar | 89 | futex_initialize(&files[i]->lock, 1); |
2593 | jermar | 90 | vfs_file_addref(files[i]); |
91 | return i; |
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92 | } |
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93 | } |
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94 | return EMFILE; |
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95 | } |
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96 | |||
97 | /** Release file descriptor. |
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98 | * |
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99 | * @param fd File descriptor being released. |
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3215 | jermar | 100 | * |
101 | * @return EOK on success or EBADF if fd is an invalid file |
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102 | * descriptor. |
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2593 | jermar | 103 | */ |
3215 | jermar | 104 | int vfs_fd_free(int fd) |
2593 | jermar | 105 | { |
3215 | jermar | 106 | if ((fd >= MAX_OPEN_FILES) || (files[fd] == NULL)) |
107 | return EBADF; |
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2593 | jermar | 108 | vfs_file_delref(files[fd]); |
109 | files[fd] = NULL; |
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3215 | jermar | 110 | return EOK; |
2593 | jermar | 111 | } |
112 | |||
113 | /** Increment reference count of VFS file structure. |
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114 | * |
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115 | * @param file File structure that will have reference count |
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116 | * incremented. |
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117 | */ |
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118 | void vfs_file_addref(vfs_file_t *file) |
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119 | { |
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120 | /* |
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121 | * File structures are per-connection, so no-one, except the current |
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122 | * fibril, should have a reference to them. This is the reason we don't |
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123 | * do any synchronization here. |
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124 | */ |
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125 | file->refcnt++; |
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126 | } |
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127 | |||
128 | /** Decrement reference count of VFS file structure. |
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129 | * |
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130 | * @param file File structure that will have reference count |
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131 | * decremented. |
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132 | */ |
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133 | void vfs_file_delref(vfs_file_t *file) |
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134 | { |
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135 | if (file->refcnt-- == 1) { |
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136 | /* |
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2731 | jermar | 137 | * Lost the last reference to a file, need to drop our reference |
2593 | jermar | 138 | * to the underlying VFS node. |
139 | */ |
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140 | vfs_node_delref(file->node); |
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141 | free(file); |
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142 | } |
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143 | } |
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144 | |||
145 | /** Find VFS file structure for a given file descriptor. |
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146 | * |
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147 | * @param fd File descriptor. |
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148 | * |
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149 | * @return VFS file structure corresponding to fd. |
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150 | */ |
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151 | vfs_file_t *vfs_file_get(int fd) |
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152 | { |
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2624 | jermar | 153 | if (fd < MAX_OPEN_FILES) |
154 | return files[fd]; |
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155 | return NULL; |
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2593 | jermar | 156 | } |
157 | |||
158 | /** |
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159 | * @} |
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160 | */ |