lib/ext2fs/unix_io.c

   1 /*
   2  * unix_io.c --- This is the Unix I/O interface to the I/O manager.
   3  *
   4  * Implements a one-block write-through cache.
   5  *
   6  * Copyright (C) 1993, 1994, 1995 Theodore Ts'o.
   7  *
   8  * %Begin-Header%
   9  * This file may be redistributed under the terms of the GNU Public
  10  * License.
  11  * %End-Header%
  12  */
  13
  14 #define _LARGEFILE_SOURCE
  15 #define _LARGEFILE64_SOURCE
  16
  17 #include <stdio.h>
  18 #include <string.h>
  19 #if HAVE_UNISTD_H
  20 #include <unistd.h>
  21 #endif
  22 #if HAVE_ERRNO_H
  23 #include <errno.h>
  24 #endif
  25 #include <fcntl.h>
  26 #include <time.h>
  27 #if HAVE_SYS_STAT_H
  28 #include <sys/stat.h>
  29 #endif
  30 #if HAVE_SYS_TYPES_H
  31 #include <sys/types.h>
  32 #endif
  33 #include <sys/resource.h>
  34
  35 #include "ext2_fs.h"
  36 #include "ext2fs.h"
  37
  38 /*
  39  * For checking structure magic numbers...
  40  */
  41
  42 #define EXT2_CHECK_MAGIC(struct, code) \
  43           if ((struct)->magic != (code)) return (code)
  44
  45 struct unix_cache {
  46         char            *buf;
  47         unsigned long   block;
  48         int             access_time;
  49         int             dirty:1;
  50         int             in_use:1;
  51 };
  52
  53 #define CACHE_SIZE 8
  54 #define WRITE_VIA_CACHE_SIZE 4  /* Must be smaller than CACHE_SIZE */
  55
  56 struct unix_private_data {
  57         int     magic;
  58         int     dev;
  59         int     flags;
  60         int     access_time;
  61         struct unix_cache cache[CACHE_SIZE];
  62 };
  63
  64 static errcode_t unix_open(const char *name, int flags, io_channel *channel);
  65 static errcode_t unix_close(io_channel channel);
  66 static errcode_t unix_set_blksize(io_channel channel, int blksize);
  67 static errcode_t unix_read_blk(io_channel channel, unsigned long block,
  68                                int count, void *data);
  69 static errcode_t unix_write_blk(io_channel channel, unsigned long block,
  70                                 int count, const void *data);
  71 static errcode_t unix_flush(io_channel channel);
  72 static errcode_t unix_write_byte(io_channel channel, unsigned long offset,
  73                                 int size, const void *data);
  74
  75 static struct struct_io_manager struct_unix_manager = {
  76         EXT2_ET_MAGIC_IO_MANAGER,
  77         "Unix I/O Manager",
  78         unix_open,
  79         unix_close,
  80         unix_set_blksize,
  81         unix_read_blk,
  82         unix_write_blk,
  83         unix_flush,
  84         unix_write_byte
  85 };
  86
  87 io_manager unix_io_manager = &struct_unix_manager;
  88
  89 /*
  90  * Here are the raw I/O functions
  91  */
  92 static errcode_t raw_read_blk(io_channel channel,
  93                               struct unix_private_data *data,
  94                               unsigned long block,
  95                               int count, void *buf)
  96 {
  97         errcode_t       retval;
  98         size_t          size;
  99         ext2_loff_t     location;
 100         int             actual = 0;
 101
 102         size = (count < 0) ? -count : count * channel->block_size;
 103         location = (ext2_loff_t) block * channel->block_size;
 104         if (ext2fs_llseek(data->dev, location, SEEK_SET) != location) {
 105                 retval = errno ? errno : EXT2_ET_LLSEEK_FAILED;
 106                 goto error_out;
 107         }
 108         actual = read(data->dev, buf, size);
 109         if (actual != size) {
 110                 if (actual < 0)
 111                         actual = 0;
 112                 retval = EXT2_ET_SHORT_READ;
 113                 goto error_out;
 114         }
 115         return 0;
 116
 117 error_out:
 118         memset((char *) buf+actual, 0, size-actual);
 119         if (channel->read_error)
 120                 retval = (channel->read_error)(channel, block, count, buf,
 121                                                size, actual, retval);
 122         return retval;
 123 }
 124
 125 static errcode_t raw_write_blk(io_channel channel,
 126                                struct unix_private_data *data,
 127                                unsigned long block,
 128                                int count, const void *buf)
 129 {
 130         size_t          size;
 131         ext2_loff_t     location;
 132         int             actual = 0;
 133         errcode_t       retval;
 134
 135         if (count == 1)
 136                 size = channel->block_size;
 137         else {
 138                 if (count < 0)
 139                         size = -count;
 140                 else
 141                         size = count * channel->block_size;
 142         }
 143
 144         location = (ext2_loff_t) block * channel->block_size;
 145         if (ext2fs_llseek(data->dev, location, SEEK_SET) != location) {
 146                 retval = errno ? errno : EXT2_ET_LLSEEK_FAILED;
 147                 goto error_out;
 148         }
 149
 150         actual = write(data->dev, buf, size);
 151         if (actual != size) {
 152                 retval = EXT2_ET_SHORT_WRITE;
 153                 goto error_out;
 154         }
 155         return 0;
 156
 157 error_out:
 158         if (channel->write_error)
 159                 retval = (channel->write_error)(channel, block, count, buf,
 160                                                 size, actual, retval);
 161         return retval;
 162 }
 163
 164
 165 /*
 166  * Here we implement the cache functions
 167  */
 168
 169 /* Allocate the cache buffers */
 170 static errcode_t alloc_cache(io_channel channel,
 171                              struct unix_private_data *data)
 172 {
 173         errcode_t               retval;
 174         struct unix_cache       *cache;
 175         int                     i;
 176
 177         data->access_time = 0;
 178         for (i=0, cache = data->cache; i < CACHE_SIZE; i++, cache++) {
 179                 cache->block = 0;
 180                 cache->access_time = 0;
 181                 cache->dirty = 0;
 182                 cache->in_use = 0;
 183                 if ((retval = ext2fs_get_mem(channel->block_size,
 184                                              (void **) &cache->buf)))
 185                         return retval;
 186         }
 187         return 0;
 188 }
 189
 190 /* Free the cache buffers */
 191 static void free_cache(io_channel channel,
 192                        struct unix_private_data *data)
 193 {
 194         struct unix_cache       *cache;
 195         int                     i;
 196
 197         data->access_time = 0;
 198         for (i=0, cache = data->cache; i < CACHE_SIZE; i++, cache++) {
 199                 cache->block = 0;
 200                 cache->access_time = 0;
 201                 cache->dirty = 0;
 202                 cache->in_use = 0;
 203                 if (cache->buf)
 204                         ext2fs_free_mem((void **) &cache->buf);
 205                 cache->buf = 0;
 206         }
 207 }
 208
 209 /*
 210  * Try to find a block in the cache.  If get_cache is non-zero, then
 211  * if the block isn't in the cache, evict the oldest block in the
 212  * cache and create a new cache entry for the requested block.
 213  */
 214 static struct unix_cache *find_cached_block(io_channel channel,
 215                                             struct unix_private_data *data,
 216                                             unsigned long block,
 217                                             int get_cache)
 218 {
 219         struct unix_cache       *cache, *unused_cache, *oldest_cache;
 220         int                     i;
 221
 222         unused_cache = oldest_cache = 0;
 223         for (i=0, cache = data->cache; i < CACHE_SIZE; i++, cache++) {
 224                 if (!cache->in_use) {
 225                         unused_cache = cache;
 226                         continue;
 227                 }
 228                 if (cache->block == block) {
 229                         cache->access_time = ++data->access_time;
 230                         return cache;
 231                 }
 232                 if (!oldest_cache ||
 233                     (cache->access_time < oldest_cache->access_time))
 234                         oldest_cache = cache;
 235         }
 236         if (!get_cache)
 237                 return 0;
 238
 239         /*
 240          * Try to allocate cache slot.
 241          */
 242         if (unused_cache)
 243                 cache = unused_cache;
 244         else {
 245                 cache = oldest_cache;
 246                 if (cache->dirty)
 247                         raw_write_blk(channel, data,
 248                                       cache->block, 1, cache->buf);
 249         }
 250         cache->in_use = 1;
 251         cache->block = block;
 252         cache->access_time = ++data->access_time;
 253         return cache;
 254 }
 255
 256 /*
 257  * Flush all of the blocks in the cache
 258  */
 259 static errcode_t flush_cached_blocks(io_channel channel,
 260                                      struct unix_private_data *data,
 261                                      int invalidate)
 262
 263 {
 264         struct unix_cache       *cache;
 265         errcode_t               retval, retval2;
 266         int                     i;
 267
 268         retval2 = 0;
 269         for (i=0, cache = data->cache; i < CACHE_SIZE; i++, cache++) {
 270                 if (!cache->in_use)
 271                         continue;
 272
 273                 if (invalidate)
 274                         cache->in_use = 0;
 275
 276                 if (!cache->dirty)
 277                         continue;
 278
 279                 retval = raw_write_blk(channel, data,
 280                                        cache->block, 1, cache->buf);
 281                 if (retval)
 282                         retval2 = retval;
 283                 else
 284                         cache->dirty = 0;
 285         }
 286         return retval2;
 287 }
 288
 289
 290
 291 static errcode_t unix_open(const char *name, int flags, io_channel *channel)
 292 {
 293         io_channel      io = NULL;
 294         struct unix_private_data *data = NULL;
 295         errcode_t       retval;
 296         int             open_flags;
 297         struct stat     st;
 298
 299         if (name == 0)
 300                 return EXT2_ET_BAD_DEVICE_NAME;
 301         retval = ext2fs_get_mem(sizeof(struct struct_io_channel),
 302                                 (void **) &io);
 303         if (retval)
 304                 return retval;
 305         memset(io, 0, sizeof(struct struct_io_channel));
 306         io->magic = EXT2_ET_MAGIC_IO_CHANNEL;
 307         retval = ext2fs_get_mem(sizeof(struct unix_private_data),
 308                                 (void **) &data);
 309         if (retval)
 310                 goto cleanup;
 311
 312         io->manager = unix_io_manager;
 313         retval = ext2fs_get_mem(strlen(name)+1, (void **) &io->name);
 314         if (retval)
 315                 goto cleanup;
 316
 317         strcpy(io->name, name);
 318         io->private_data = data;
 319         io->block_size = 1024;
 320         io->read_error = 0;
 321         io->write_error = 0;
 322         io->refcount = 1;
 323
 324         memset(data, 0, sizeof(struct unix_private_data));
 325         data->magic = EXT2_ET_MAGIC_UNIX_IO_CHANNEL;
 326
 327         if ((retval = alloc_cache(io, data)))
 328                 goto cleanup;
 329
 330         open_flags = (flags & IO_FLAG_RW) ? O_RDWR : O_RDONLY;
 331 #ifdef HAVE_OPEN64
 332         data->dev = open64(name, open_flags);
 333 #else
 334         data->dev = open(name, open_flags);
 335 #endif
 336         if (data->dev < 0) {
 337                 retval = errno;
 338                 goto cleanup;
 339         }
 340         /*
 341          * Work around a bug in 2.4.10+ kernels where writes to block
 342          * devices are wrongly getting hit by the filesize limit.
 343          */
 344         if ((flags & IO_FLAG_RW) &&
 345             (fstat(data->dev, &st) == 0) &&
 346             (S_ISBLK(st.st_mode))) {
 347                 struct rlimit   rlim;
 348
 349                 rlim.rlim_cur = rlim.rlim_max = ((unsigned long)(~0UL));
 350                 setrlimit(RLIMIT_FSIZE, &rlim);
 351                 getrlimit(RLIMIT_FSIZE, &rlim);
 352                 if (((unsigned long) rlim.rlim_cur) <
 353                     ((unsigned long) rlim.rlim_max)) {
 354                         rlim.rlim_cur = rlim.rlim_max;
 355                         setrlimit(RLIMIT_FSIZE, &rlim);
 356                 }
 357         }
 358         *channel = io;
 359         return 0;
 360
 361 cleanup:
 362         if (data) {
 363                 free_cache(io, data);
 364                 ext2fs_free_mem((void **) &data);
 365         }
 366         if (io)
 367                 ext2fs_free_mem((void **) &io);
 368         return retval;
 369 }
 370
 371 static errcode_t unix_close(io_channel channel)
 372 {
 373         struct unix_private_data *data;
 374         errcode_t       retval = 0;
 375
 376         EXT2_CHECK_MAGIC(channel, EXT2_ET_MAGIC_IO_CHANNEL);
 377         data = (struct unix_private_data *) channel->private_data;
 378         EXT2_CHECK_MAGIC(data, EXT2_ET_MAGIC_UNIX_IO_CHANNEL);
 379
 380         if (--channel->refcount > 0)
 381                 return 0;
 382
 383         retval = flush_cached_blocks(channel, data, 0);
 384
 385         if (close(data->dev) < 0)
 386                 retval = errno;
 387         free_cache(channel, data);
 388         if (channel->private_data)
 389                 ext2fs_free_mem((void **) &channel->private_data);
 390         if (channel->name)
 391                 ext2fs_free_mem((void **) &channel->name);
 392         ext2fs_free_mem((void **) &channel);
 393         return retval;
 394 }
 395
 396 static errcode_t unix_set_blksize(io_channel channel, int blksize)
 397 {
 398         struct unix_private_data *data;
 399         errcode_t               retval;
 400
 401         EXT2_CHECK_MAGIC(channel, EXT2_ET_MAGIC_IO_CHANNEL);
 402         data = (struct unix_private_data *) channel->private_data;
 403         EXT2_CHECK_MAGIC(data, EXT2_ET_MAGIC_UNIX_IO_CHANNEL);
 404
 405         if (channel->block_size != blksize) {
 406                 if ((retval = flush_cached_blocks(channel, data, 0)))
 407                         return retval;
 408
 409                 channel->block_size = blksize;
 410                 free_cache(channel, data);
 411                 if ((retval = alloc_cache(channel, data)))
 412                         return retval;
 413         }
 414         return 0;
 415 }
 416
 417
 418 static errcode_t unix_read_blk(io_channel channel, unsigned long block,
 419                                int count, void *buf)
 420 {
 421         struct unix_private_data *data;
 422         struct unix_cache *cache;
 423         errcode_t       retval;
 424         char            *cp;
 425         int             i, j;
 426
 427         EXT2_CHECK_MAGIC(channel, EXT2_ET_MAGIC_IO_CHANNEL);
 428         data = (struct unix_private_data *) channel->private_data;
 429         EXT2_CHECK_MAGIC(data, EXT2_ET_MAGIC_UNIX_IO_CHANNEL);
 430
 431         /*
 432          * If we're doing an odd-sized read, flush out the cache and
 433          * then do a direct read.
 434          */
 435         if (count < 0) {
 436                 if ((retval = flush_cached_blocks(channel, data, 0)))
 437                         return retval;
 438                 return raw_read_blk(channel, data, block, count, buf);
 439         }
 440
 441         cp = buf;
 442         while (count > 0) {
 443                 /* If it's in the cache, use it! */
 444                 if ((cache = find_cached_block(channel, data, block, 0))) {
 445 #ifdef DEBUG
 446                         printf("Using cached block %d\n", block);
 447 #endif
 448                         memcpy(cp, cache->buf, channel->block_size);
 449                         count--;
 450                         block++;
 451                         cp += channel->block_size;
 452                         continue;
 453                 }
 454                 /*
 455                  * Find the number of uncached blocks so we can do a
 456                  * single read request
 457                  */
 458                 for (i=1; i < count; i++)
 459                         if (find_cached_block(channel, data, block+i, 0))
 460                                 break;
 461 #ifdef DEBUG
 462                 printf("Reading %d blocks starting at %d\n", i, block);
 463 #endif
 464                 if ((retval = raw_read_blk(channel, data, block, i, cp)))
 465                         return retval;
 466
 467                 /* Save the results in the cache */
 468                 for (j=0; j < i; j++) {
 469                         count--;
 470                         cache = find_cached_block(channel, data, block++, 1);
 471                         if (cache)
 472                                 memcpy(cache->buf, cp, channel->block_size);
 473                         cp += channel->block_size;
 474                 }
 475         }
 476         return 0;
 477 }
 478
 479 static errcode_t unix_write_blk(io_channel channel, unsigned long block,
 480                                 int count, const void *buf)
 481 {
 482         struct unix_private_data *data;
 483         struct unix_cache *cache;
 484         errcode_t       retval = 0, retval2;
 485         const char      *cp;
 486         int             writethrough;
 487
 488         EXT2_CHECK_MAGIC(channel, EXT2_ET_MAGIC_IO_CHANNEL);
 489         data = (struct unix_private_data *) channel->private_data;
 490         EXT2_CHECK_MAGIC(data, EXT2_ET_MAGIC_UNIX_IO_CHANNEL);
 491
 492         /*
 493          * If we're doing an odd-sized write or a very large write,
 494          * flush out the cache completely and then do a direct write.
 495          */
 496         if (count < 0 || count > WRITE_VIA_CACHE_SIZE) {
 497                 if ((retval = flush_cached_blocks(channel, data, 1)))
 498                         return retval;
 499                 return raw_write_blk(channel, data, block, count, buf);
 500         }
 501
 502         /*
 503          * For a moderate-sized multi-block write, first force a write
 504          * if we're in write-through cache mode, and then fill the
 505          * cache with the blocks.
 506          */
 507         writethrough = channel->flags & CHANNEL_FLAGS_WRITETHROUGH;
 508         if (writethrough)
 509                 retval = raw_write_blk(channel, data, block, count, buf);
 510
 511         cp = buf;
 512         while (count > 0) {
 513                 cache = find_cached_block(channel, data, block, 1);
 514                 if (!cache) {
 515                         /*
 516                          * Oh shit, we couldn't get cache descriptor.
 517                          * Force the write directly.
 518                          */
 519                         if ((retval2 = raw_write_blk(channel, data, block,
 520                                                 1, cp)))
 521                                 retval = retval2;
 522                 } else {
 523                         memcpy(cache->buf, cp, channel->block_size);
 524                         cache->dirty = !writethrough;
 525                 }
 526                 count--;
 527                 block++;
 528                 cp += channel->block_size;
 529         }
 530         return retval;
 531 }
 532
 533 static errcode_t unix_write_byte(io_channel channel, unsigned long offset,
 534                                  int size, const void *buf)
 535 {
 536         struct unix_private_data *data;
 537         errcode_t       retval = 0;
 538         size_t          actual;
 539
 540         EXT2_CHECK_MAGIC(channel, EXT2_ET_MAGIC_IO_CHANNEL);
 541         data = (struct unix_private_data *) channel->private_data;
 542         EXT2_CHECK_MAGIC(data, EXT2_ET_MAGIC_UNIX_IO_CHANNEL);
 543
 544         /*
 545          * Flush out the cache completely
 546          */
 547         if ((retval = flush_cached_blocks(channel, data, 1)))
 548                 return retval;
 549
 550         if (lseek(data->dev, offset, SEEK_SET) < 0)
 551                 return errno;
 552
 553         actual = write(data->dev, buf, size);
 554         if (actual != size)
 555                 return EXT2_ET_SHORT_WRITE;
 556
 557         return 0;
 558 }
 559
 560 /*
 561  * Flush data buffers to disk.
 562  */
 563 static errcode_t unix_flush(io_channel channel)
 564 {
 565         struct unix_private_data *data;
 566         errcode_t retval = 0;
 567
 568         EXT2_CHECK_MAGIC(channel, EXT2_ET_MAGIC_IO_CHANNEL);
 569         data = (struct unix_private_data *) channel->private_data;
 570         EXT2_CHECK_MAGIC(data, EXT2_ET_MAGIC_UNIX_IO_CHANNEL);
 571
 572         retval = flush_cached_blocks(channel, data, 0);
 573         fsync(data->dev);
 574         return retval;
 575 }
 576