fileio.c revision 4605a35d1ef573dc166a73ed910d0ee7b02489cb
1/* 2 * fileio.c --- Simple file I/O routines 3 * 4 * Copyright (C) 1997 Theodore Ts'o. 5 * 6 * %Begin-Header% 7 * This file may be redistributed under the terms of the GNU Library 8 * General Public License, version 2. 9 * %End-Header% 10 */ 11 12#include "config.h" 13#include <stdio.h> 14#include <string.h> 15#if HAVE_UNISTD_H 16#include <unistd.h> 17#endif 18 19#include "ext2_fs.h" 20#include "ext2fs.h" 21 22struct ext2_file { 23 errcode_t magic; 24 ext2_filsys fs; 25 ext2_ino_t ino; 26 struct ext2_inode inode; 27 int flags; 28 __u64 pos; 29 blk64_t blockno; 30 blk64_t physblock; 31 char *buf; 32}; 33 34#define BMAP_BUFFER (file->buf + fs->blocksize) 35 36errcode_t ext2fs_file_open2(ext2_filsys fs, ext2_ino_t ino, 37 struct ext2_inode *inode, 38 int flags, ext2_file_t *ret) 39{ 40 ext2_file_t file; 41 errcode_t retval; 42 43 /* 44 * Don't let caller create or open a file for writing if the 45 * filesystem is read-only. 46 */ 47 if ((flags & (EXT2_FILE_WRITE | EXT2_FILE_CREATE)) && 48 !(fs->flags & EXT2_FLAG_RW)) 49 return EXT2_ET_RO_FILSYS; 50 51 retval = ext2fs_get_mem(sizeof(struct ext2_file), &file); 52 if (retval) 53 return retval; 54 55 memset(file, 0, sizeof(struct ext2_file)); 56 file->magic = EXT2_ET_MAGIC_EXT2_FILE; 57 file->fs = fs; 58 file->ino = ino; 59 file->flags = flags & EXT2_FILE_MASK; 60 61 if (inode) { 62 memcpy(&file->inode, inode, sizeof(struct ext2_inode)); 63 } else { 64 retval = ext2fs_read_inode(fs, ino, &file->inode); 65 if (retval) 66 goto fail; 67 } 68 69 retval = ext2fs_get_array(3, fs->blocksize, &file->buf); 70 if (retval) 71 goto fail; 72 73 *ret = file; 74 return 0; 75 76fail: 77 if (file->buf) 78 ext2fs_free_mem(&file->buf); 79 ext2fs_free_mem(&file); 80 return retval; 81} 82 83errcode_t ext2fs_file_open(ext2_filsys fs, ext2_ino_t ino, 84 int flags, ext2_file_t *ret) 85{ 86 return ext2fs_file_open2(fs, ino, NULL, flags, ret); 87} 88 89/* 90 * This function returns the filesystem handle of a file from the structure 91 */ 92ext2_filsys ext2fs_file_get_fs(ext2_file_t file) 93{ 94 if (file->magic != EXT2_ET_MAGIC_EXT2_FILE) 95 return 0; 96 return file->fs; 97} 98 99/* 100 * This function returns the pointer to the inode of a file from the structure 101 */ 102struct ext2_inode *ext2fs_file_get_inode(ext2_file_t file) 103{ 104 if (file->magic != EXT2_ET_MAGIC_EXT2_FILE) 105 return NULL; 106 return &file->inode; 107} 108 109/* This function returns the inode number from the structure */ 110ext2_ino_t ext2fs_file_get_inode_num(ext2_file_t file) 111{ 112 if (file->magic != EXT2_ET_MAGIC_EXT2_FILE) 113 return 0; 114 return file->ino; 115} 116 117/* 118 * This function flushes the dirty block buffer out to disk if 119 * necessary. 120 */ 121errcode_t ext2fs_file_flush(ext2_file_t file) 122{ 123 errcode_t retval; 124 ext2_filsys fs; 125 126 EXT2_CHECK_MAGIC(file, EXT2_ET_MAGIC_EXT2_FILE); 127 fs = file->fs; 128 129 if (!(file->flags & EXT2_FILE_BUF_VALID) || 130 !(file->flags & EXT2_FILE_BUF_DIRTY)) 131 return 0; 132 133 /* 134 * OK, the physical block hasn't been allocated yet. 135 * Allocate it. 136 */ 137 if (!file->physblock) { 138 retval = ext2fs_bmap2(fs, file->ino, &file->inode, 139 BMAP_BUFFER, file->ino ? BMAP_ALLOC : 0, 140 file->blockno, 0, &file->physblock); 141 if (retval) 142 return retval; 143 } 144 145 retval = io_channel_write_blk(fs->io, file->physblock, 146 1, file->buf); 147 if (retval) 148 return retval; 149 150 file->flags &= ~EXT2_FILE_BUF_DIRTY; 151 152 return retval; 153} 154 155/* 156 * This function synchronizes the file's block buffer and the current 157 * file position, possibly invalidating block buffer if necessary 158 */ 159static errcode_t sync_buffer_position(ext2_file_t file) 160{ 161 blk64_t b; 162 errcode_t retval; 163 164 b = file->pos / file->fs->blocksize; 165 if (b != file->blockno) { 166 retval = ext2fs_file_flush(file); 167 if (retval) 168 return retval; 169 file->flags &= ~EXT2_FILE_BUF_VALID; 170 } 171 file->blockno = b; 172 return 0; 173} 174 175/* 176 * This function loads the file's block buffer with valid data from 177 * the disk as necessary. 178 * 179 * If dontfill is true, then skip initializing the buffer since we're 180 * going to be replacing its entire contents anyway. If set, then the 181 * function basically only sets file->physblock and EXT2_FILE_BUF_VALID 182 */ 183#define DONTFILL 1 184static errcode_t load_buffer(ext2_file_t file, int dontfill) 185{ 186 ext2_filsys fs = file->fs; 187 errcode_t retval; 188 189 if (!(file->flags & EXT2_FILE_BUF_VALID)) { 190 retval = ext2fs_bmap2(fs, file->ino, &file->inode, 191 BMAP_BUFFER, 0, file->blockno, 0, 192 &file->physblock); 193 if (retval) 194 return retval; 195 if (!dontfill) { 196 if (file->physblock) { 197 retval = io_channel_read_blk(fs->io, 198 file->physblock, 199 1, file->buf); 200 if (retval) 201 return retval; 202 } else 203 memset(file->buf, 0, fs->blocksize); 204 } 205 file->flags |= EXT2_FILE_BUF_VALID; 206 } 207 return 0; 208} 209 210 211errcode_t ext2fs_file_close(ext2_file_t file) 212{ 213 errcode_t retval; 214 215 EXT2_CHECK_MAGIC(file, EXT2_ET_MAGIC_EXT2_FILE); 216 217 retval = ext2fs_file_flush(file); 218 219 if (file->buf) 220 ext2fs_free_mem(&file->buf); 221 ext2fs_free_mem(&file); 222 223 return retval; 224} 225 226 227errcode_t ext2fs_file_read(ext2_file_t file, void *buf, 228 unsigned int wanted, unsigned int *got) 229{ 230 ext2_filsys fs; 231 errcode_t retval = 0; 232 unsigned int start, c, count = 0; 233 __u64 left; 234 char *ptr = (char *) buf; 235 236 EXT2_CHECK_MAGIC(file, EXT2_ET_MAGIC_EXT2_FILE); 237 fs = file->fs; 238 239 while ((file->pos < EXT2_I_SIZE(&file->inode)) && (wanted > 0)) { 240 retval = sync_buffer_position(file); 241 if (retval) 242 goto fail; 243 retval = load_buffer(file, 0); 244 if (retval) 245 goto fail; 246 247 start = file->pos % fs->blocksize; 248 c = fs->blocksize - start; 249 if (c > wanted) 250 c = wanted; 251 left = EXT2_I_SIZE(&file->inode) - file->pos ; 252 if (c > left) 253 c = left; 254 255 memcpy(ptr, file->buf+start, c); 256 file->pos += c; 257 ptr += c; 258 count += c; 259 wanted -= c; 260 } 261 262fail: 263 if (got) 264 *got = count; 265 return retval; 266} 267 268 269errcode_t ext2fs_file_write(ext2_file_t file, const void *buf, 270 unsigned int nbytes, unsigned int *written) 271{ 272 ext2_filsys fs; 273 errcode_t retval = 0; 274 unsigned int start, c, count = 0; 275 const char *ptr = (const char *) buf; 276 277 EXT2_CHECK_MAGIC(file, EXT2_ET_MAGIC_EXT2_FILE); 278 fs = file->fs; 279 280 if (!(file->flags & EXT2_FILE_WRITE)) 281 return EXT2_ET_FILE_RO; 282 283 while (nbytes > 0) { 284 retval = sync_buffer_position(file); 285 if (retval) 286 goto fail; 287 288 start = file->pos % fs->blocksize; 289 c = fs->blocksize - start; 290 if (c > nbytes) 291 c = nbytes; 292 293 /* 294 * We only need to do a read-modify-update cycle if 295 * we're doing a partial write. 296 */ 297 retval = load_buffer(file, (c == fs->blocksize)); 298 if (retval) 299 goto fail; 300 301 file->flags |= EXT2_FILE_BUF_DIRTY; 302 memcpy(file->buf+start, ptr, c); 303 file->pos += c; 304 ptr += c; 305 count += c; 306 nbytes -= c; 307 } 308 309fail: 310 /* Update inode size */ 311 if (count != 0 && EXT2_I_SIZE(&file->inode) < file->pos) { 312 errcode_t rc; 313 314 rc = ext2fs_file_set_size2(file, file->pos); 315 if (retval == 0) 316 retval = rc; 317 } 318 319 if (written) 320 *written = count; 321 return retval; 322} 323 324errcode_t ext2fs_file_llseek(ext2_file_t file, __u64 offset, 325 int whence, __u64 *ret_pos) 326{ 327 EXT2_CHECK_MAGIC(file, EXT2_ET_MAGIC_EXT2_FILE); 328 329 if (whence == EXT2_SEEK_SET) 330 file->pos = offset; 331 else if (whence == EXT2_SEEK_CUR) 332 file->pos += offset; 333 else if (whence == EXT2_SEEK_END) 334 file->pos = EXT2_I_SIZE(&file->inode) + offset; 335 else 336 return EXT2_ET_INVALID_ARGUMENT; 337 338 if (ret_pos) 339 *ret_pos = file->pos; 340 341 return 0; 342} 343 344errcode_t ext2fs_file_lseek(ext2_file_t file, ext2_off_t offset, 345 int whence, ext2_off_t *ret_pos) 346{ 347 __u64 loffset, ret_loffset; 348 errcode_t retval; 349 350 loffset = offset; 351 retval = ext2fs_file_llseek(file, loffset, whence, &ret_loffset); 352 if (ret_pos) 353 *ret_pos = (ext2_off_t) ret_loffset; 354 return retval; 355} 356 357 358/* 359 * This function returns the size of the file, according to the inode 360 */ 361errcode_t ext2fs_file_get_lsize(ext2_file_t file, __u64 *ret_size) 362{ 363 if (file->magic != EXT2_ET_MAGIC_EXT2_FILE) 364 return EXT2_ET_MAGIC_EXT2_FILE; 365 *ret_size = EXT2_I_SIZE(&file->inode); 366 return 0; 367} 368 369/* 370 * This function returns the size of the file, according to the inode 371 */ 372ext2_off_t ext2fs_file_get_size(ext2_file_t file) 373{ 374 __u64 size; 375 376 if (ext2fs_file_get_lsize(file, &size)) 377 return 0; 378 if ((size >> 32) != 0) 379 return 0; 380 return size; 381} 382 383/* 384 * This function sets the size of the file, truncating it if necessary 385 * 386 */ 387errcode_t ext2fs_file_set_size2(ext2_file_t file, ext2_off64_t size) 388{ 389 ext2_off64_t old_size; 390 errcode_t retval; 391 blk64_t old_truncate, truncate_block; 392 393 EXT2_CHECK_MAGIC(file, EXT2_ET_MAGIC_EXT2_FILE); 394 395 truncate_block = ((size + file->fs->blocksize - 1) >> 396 EXT2_BLOCK_SIZE_BITS(file->fs->super)); 397 old_size = EXT2_I_SIZE(&file->inode); 398 old_truncate = ((old_size + file->fs->blocksize - 1) >> 399 EXT2_BLOCK_SIZE_BITS(file->fs->super)); 400 401 /* If we're writing a large file, set the large_file flag */ 402 if (LINUX_S_ISREG(file->inode.i_mode) && 403 EXT2_I_SIZE(&file->inode) > 0x7FFFFFFULL && 404 (!EXT2_HAS_RO_COMPAT_FEATURE(file->fs->super, 405 EXT2_FEATURE_RO_COMPAT_LARGE_FILE) || 406 file->fs->super->s_rev_level == EXT2_GOOD_OLD_REV)) { 407 file->fs->super->s_feature_ro_compat |= 408 EXT2_FEATURE_RO_COMPAT_LARGE_FILE; 409 ext2fs_update_dynamic_rev(file->fs); 410 ext2fs_mark_super_dirty(file->fs); 411 } 412 413 file->inode.i_size = size & 0xffffffff; 414 file->inode.i_size_high = (size >> 32); 415 if (file->ino) { 416 retval = ext2fs_write_inode(file->fs, file->ino, &file->inode); 417 if (retval) 418 return retval; 419 } 420 421 if (truncate_block >= old_truncate) 422 return 0; 423 424 return ext2fs_punch(file->fs, file->ino, &file->inode, 0, 425 truncate_block, ~0ULL); 426} 427 428errcode_t ext2fs_file_set_size(ext2_file_t file, ext2_off_t size) 429{ 430 return ext2fs_file_set_size2(file, size); 431} 432