fileio.c revision 269da3b8068ecb0bdf8077b0f7b27f164203cb35
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#include "ext2fsP.h" 22 23struct ext2_file { 24 errcode_t magic; 25 ext2_filsys fs; 26 ext2_ino_t ino; 27 struct ext2_inode inode; 28 int flags; 29 __u64 pos; 30 blk64_t blockno; 31 blk64_t physblock; 32 char *buf; 33}; 34 35#define BMAP_BUFFER (file->buf + fs->blocksize) 36 37errcode_t ext2fs_file_open2(ext2_filsys fs, ext2_ino_t ino, 38 struct ext2_inode *inode, 39 int flags, ext2_file_t *ret) 40{ 41 ext2_file_t file; 42 errcode_t retval; 43 44 /* 45 * Don't let caller create or open a file for writing if the 46 * filesystem is read-only. 47 */ 48 if ((flags & (EXT2_FILE_WRITE | EXT2_FILE_CREATE)) && 49 !(fs->flags & EXT2_FLAG_RW)) 50 return EXT2_ET_RO_FILSYS; 51 52 retval = ext2fs_get_mem(sizeof(struct ext2_file), &file); 53 if (retval) 54 return retval; 55 56 memset(file, 0, sizeof(struct ext2_file)); 57 file->magic = EXT2_ET_MAGIC_EXT2_FILE; 58 file->fs = fs; 59 file->ino = ino; 60 file->flags = flags & EXT2_FILE_MASK; 61 62 if (inode) { 63 memcpy(&file->inode, inode, sizeof(struct ext2_inode)); 64 } else { 65 retval = ext2fs_read_inode(fs, ino, &file->inode); 66 if (retval) 67 goto fail; 68 } 69 70 retval = ext2fs_get_array(3, fs->blocksize, &file->buf); 71 if (retval) 72 goto fail; 73 74 *ret = file; 75 return 0; 76 77fail: 78 if (file->buf) 79 ext2fs_free_mem(&file->buf); 80 ext2fs_free_mem(&file); 81 return retval; 82} 83 84errcode_t ext2fs_file_open(ext2_filsys fs, ext2_ino_t ino, 85 int flags, ext2_file_t *ret) 86{ 87 return ext2fs_file_open2(fs, ino, NULL, flags, ret); 88} 89 90/* 91 * This function returns the filesystem handle of a file from the structure 92 */ 93ext2_filsys ext2fs_file_get_fs(ext2_file_t file) 94{ 95 if (file->magic != EXT2_ET_MAGIC_EXT2_FILE) 96 return 0; 97 return file->fs; 98} 99 100/* 101 * This function returns the pointer to the inode of a file from the structure 102 */ 103struct ext2_inode *ext2fs_file_get_inode(ext2_file_t file) 104{ 105 if (file->magic != EXT2_ET_MAGIC_EXT2_FILE) 106 return NULL; 107 return &file->inode; 108} 109 110/* This function returns the inode number from the structure */ 111ext2_ino_t ext2fs_file_get_inode_num(ext2_file_t file) 112{ 113 if (file->magic != EXT2_ET_MAGIC_EXT2_FILE) 114 return 0; 115 return file->ino; 116} 117 118/* 119 * This function flushes the dirty block buffer out to disk if 120 * necessary. 121 */ 122errcode_t ext2fs_file_flush(ext2_file_t file) 123{ 124 errcode_t retval; 125 ext2_filsys fs; 126 127 EXT2_CHECK_MAGIC(file, EXT2_ET_MAGIC_EXT2_FILE); 128 fs = file->fs; 129 130 if (!(file->flags & EXT2_FILE_BUF_VALID) || 131 !(file->flags & EXT2_FILE_BUF_DIRTY)) 132 return 0; 133 134 /* 135 * OK, the physical block hasn't been allocated yet. 136 * Allocate it. 137 */ 138 if (!file->physblock) { 139 retval = ext2fs_bmap2(fs, file->ino, &file->inode, 140 BMAP_BUFFER, file->ino ? BMAP_ALLOC : 0, 141 file->blockno, 0, &file->physblock); 142 if (retval) 143 return retval; 144 } 145 146 retval = io_channel_write_blk64(fs->io, file->physblock, 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_blk64(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 /* 302 * OK, the physical block hasn't been allocated yet. 303 * Allocate it. 304 */ 305 if (!file->physblock) { 306 retval = ext2fs_bmap2(fs, file->ino, &file->inode, 307 BMAP_BUFFER, 308 file->ino ? BMAP_ALLOC : 0, 309 file->blockno, 0, 310 &file->physblock); 311 if (retval) 312 goto fail; 313 } 314 315 file->flags |= EXT2_FILE_BUF_DIRTY; 316 memcpy(file->buf+start, ptr, c); 317 file->pos += c; 318 ptr += c; 319 count += c; 320 nbytes -= c; 321 } 322 323fail: 324 /* Update inode size */ 325 if (count != 0 && EXT2_I_SIZE(&file->inode) < file->pos) { 326 errcode_t rc; 327 328 rc = ext2fs_file_set_size2(file, file->pos); 329 if (retval == 0) 330 retval = rc; 331 } 332 333 if (written) 334 *written = count; 335 return retval; 336} 337 338errcode_t ext2fs_file_llseek(ext2_file_t file, __u64 offset, 339 int whence, __u64 *ret_pos) 340{ 341 EXT2_CHECK_MAGIC(file, EXT2_ET_MAGIC_EXT2_FILE); 342 343 if (whence == EXT2_SEEK_SET) 344 file->pos = offset; 345 else if (whence == EXT2_SEEK_CUR) 346 file->pos += offset; 347 else if (whence == EXT2_SEEK_END) 348 file->pos = EXT2_I_SIZE(&file->inode) + offset; 349 else 350 return EXT2_ET_INVALID_ARGUMENT; 351 352 if (ret_pos) 353 *ret_pos = file->pos; 354 355 return 0; 356} 357 358errcode_t ext2fs_file_lseek(ext2_file_t file, ext2_off_t offset, 359 int whence, ext2_off_t *ret_pos) 360{ 361 __u64 loffset, ret_loffset; 362 errcode_t retval; 363 364 loffset = offset; 365 retval = ext2fs_file_llseek(file, loffset, whence, &ret_loffset); 366 if (ret_pos) 367 *ret_pos = (ext2_off_t) ret_loffset; 368 return retval; 369} 370 371 372/* 373 * This function returns the size of the file, according to the inode 374 */ 375errcode_t ext2fs_file_get_lsize(ext2_file_t file, __u64 *ret_size) 376{ 377 if (file->magic != EXT2_ET_MAGIC_EXT2_FILE) 378 return EXT2_ET_MAGIC_EXT2_FILE; 379 *ret_size = EXT2_I_SIZE(&file->inode); 380 return 0; 381} 382 383/* 384 * This function returns the size of the file, according to the inode 385 */ 386ext2_off_t ext2fs_file_get_size(ext2_file_t file) 387{ 388 __u64 size; 389 390 if (ext2fs_file_get_lsize(file, &size)) 391 return 0; 392 if ((size >> 32) != 0) 393 return 0; 394 return size; 395} 396 397/* Zero the parts of the last block that are past EOF. */ 398errcode_t ext2fs_file_zero_past_offset(ext2_file_t file, ext2_off64_t offset) 399{ 400 ext2_filsys fs = file->fs; 401 char *b = NULL; 402 ext2_off64_t off = offset % fs->blocksize; 403 blk64_t blk; 404 int ret_flags; 405 errcode_t retval; 406 407 if (off == 0) 408 return 0; 409 410 retval = sync_buffer_position(file); 411 if (retval) 412 return retval; 413 414 /* Is there an initialized block at the end? */ 415 retval = ext2fs_bmap2(fs, file->ino, NULL, NULL, 0, 416 offset / fs->blocksize, &ret_flags, &blk); 417 if (retval) 418 return retval; 419 if ((blk == 0) || (ret_flags & BMAP_RET_UNINIT)) 420 return 0; 421 422 /* Zero to the end of the block */ 423 retval = ext2fs_get_mem(fs->blocksize, &b); 424 if (retval) 425 return retval; 426 427 /* Read/zero/write block */ 428 retval = io_channel_read_blk64(fs->io, blk, 1, b); 429 if (retval) 430 goto out; 431 432 memset(b + off, 0, fs->blocksize - off); 433 434 retval = io_channel_write_blk64(fs->io, blk, 1, b); 435 if (retval) 436 goto out; 437 438out: 439 ext2fs_free_mem(&b); 440 return retval; 441} 442 443/* 444 * This function sets the size of the file, truncating it if necessary 445 * 446 */ 447errcode_t ext2fs_file_set_size2(ext2_file_t file, ext2_off64_t size) 448{ 449 ext2_off64_t old_size; 450 errcode_t retval; 451 blk64_t old_truncate, truncate_block; 452 453 EXT2_CHECK_MAGIC(file, EXT2_ET_MAGIC_EXT2_FILE); 454 455 if (size && ext2fs_file_block_offset_too_big(file->fs, &file->inode, 456 (size - 1) / file->fs->blocksize)) 457 return EXT2_ET_FILE_TOO_BIG; 458 truncate_block = ((size + file->fs->blocksize - 1) >> 459 EXT2_BLOCK_SIZE_BITS(file->fs->super)); 460 old_size = EXT2_I_SIZE(&file->inode); 461 old_truncate = ((old_size + file->fs->blocksize - 1) >> 462 EXT2_BLOCK_SIZE_BITS(file->fs->super)); 463 464 /* If we're writing a large file, set the large_file flag */ 465 if (LINUX_S_ISREG(file->inode.i_mode) && 466 ext2fs_needs_large_file_feature(EXT2_I_SIZE(&file->inode)) && 467 (!EXT2_HAS_RO_COMPAT_FEATURE(file->fs->super, 468 EXT2_FEATURE_RO_COMPAT_LARGE_FILE) || 469 file->fs->super->s_rev_level == EXT2_GOOD_OLD_REV)) { 470 file->fs->super->s_feature_ro_compat |= 471 EXT2_FEATURE_RO_COMPAT_LARGE_FILE; 472 ext2fs_update_dynamic_rev(file->fs); 473 ext2fs_mark_super_dirty(file->fs); 474 } 475 476 file->inode.i_size = size & 0xffffffff; 477 file->inode.i_size_high = (size >> 32); 478 if (file->ino) { 479 retval = ext2fs_write_inode(file->fs, file->ino, &file->inode); 480 if (retval) 481 return retval; 482 } 483 484 retval = ext2fs_file_zero_past_offset(file, size); 485 if (retval) 486 return retval; 487 488 if (truncate_block >= old_truncate) 489 return 0; 490 491 return ext2fs_punch(file->fs, file->ino, &file->inode, 0, 492 truncate_block, ~0ULL); 493} 494 495errcode_t ext2fs_file_set_size(ext2_file_t file, ext2_off_t size) 496{ 497 return ext2fs_file_set_size2(file, size); 498} 499