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