[821] | 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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