lib/tdb/common/io.c

   1  /*
   2    Unix SMB/CIFS implementation.
   3
   4    trivial database library
   5
   6    Copyright (C) Andrew Tridgell              1999-2005
   7    Copyright (C) Paul `Rusty' Russell              2000
   8    Copyright (C) Jeremy Allison                    2000-2003
   9
  10      ** NOTE! The following LGPL license applies to the tdb
  11      ** library. This does NOT imply that all of Samba is released
  12      ** under the LGPL
  13
  14    This library is free software; you can redistribute it and/or
  15    modify it under the terms of the GNU Lesser General Public
  16    License as published by the Free Software Foundation; either
  17    version 3 of the License, or (at your option) any later version.
  18
  19    This library is distributed in the hope that it will be useful,
  20    but WITHOUT ANY WARRANTY; without even the implied warranty of
  21    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  22    Lesser General Public License for more details.
  23
  24    You should have received a copy of the GNU Lesser General Public
  25    License along with this library; if not, see <http://www.gnu.org/licenses/>.
  26 */
  27
  28
  29 #include "tdb_private.h"
  30
  31 /* check for an out of bounds access - if it is out of bounds then
  32    see if the database has been expanded by someone else and expand
  33    if necessary
  34 */
  35 static int tdb_oob(struct tdb_context *tdb, tdb_off_t off, tdb_len_t len,
  36                    int probe)
  37 {
  38         struct stat st;
  39         if (len + off < len) {
  40                 if (!probe) {
  41                         /* Ensure ecode is set for log fn. */
  42                         tdb->ecode = TDB_ERR_IO;
  43                         TDB_LOG((tdb, TDB_DEBUG_FATAL,"tdb_oob off %u len %u wrap\n",
  44                                  off, len));
  45                 }
  46                 return -1;
  47         }
  48
  49         if (off + len <= tdb->map_size)
  50                 return 0;
  51         if (tdb->flags & TDB_INTERNAL) {
  52                 if (!probe) {
  53                         /* Ensure ecode is set for log fn. */
  54                         tdb->ecode = TDB_ERR_IO;
  55                         TDB_LOG((tdb, TDB_DEBUG_FATAL,"tdb_oob len %u beyond internal malloc size %u\n",
  56                                  (int)(off + len), (int)tdb->map_size));
  57                 }
  58                 return -1;
  59         }
  60
  61         if (fstat(tdb->fd, &st) == -1) {
  62                 tdb->ecode = TDB_ERR_IO;
  63                 return -1;
  64         }
  65
  66         /* Beware >4G files! */
  67         if ((tdb_off_t)st.st_size != st.st_size) {
  68                 /* Ensure ecode is set for log fn. */
  69                 tdb->ecode = TDB_ERR_IO;
  70                 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_oob len %llu too large!\n",
  71                          (long long)st.st_size));
  72                 return -1;
  73         }
  74
  75         /* Unmap, update size, remap.  We do this unconditionally, to handle
  76          * the unusual case where the db is truncated.
  77          *
  78          * This can happen to a child using tdb_reopen_all(true) on a
  79          * TDB_CLEAR_IF_FIRST tdb whose parent crashes: the next
  80          * opener will truncate the database. */
  81         if (tdb_munmap(tdb) == -1) {
  82                 tdb->ecode = TDB_ERR_IO;
  83                 return -1;
  84         }
  85         tdb->map_size = st.st_size;
  86         if (tdb_mmap(tdb) != 0) {
  87                 return -1;
  88         }
  89
  90         if (st.st_size < (size_t)off + len) {
  91                 if (!probe) {
  92                         /* Ensure ecode is set for log fn. */
  93                         tdb->ecode = TDB_ERR_IO;
  94                         TDB_LOG((tdb, TDB_DEBUG_FATAL,"tdb_oob len %u beyond eof at %u\n",
  95                                  (int)(off + len), (int)st.st_size));
  96                 }
  97                 return -1;
  98         }
  99         return 0;
 100 }
 101
 102 /* write a lump of data at a specified offset */
 103 static int tdb_write(struct tdb_context *tdb, tdb_off_t off,
 104                      const void *buf, tdb_len_t len)
 105 {
 106         if (len == 0) {
 107                 return 0;
 108         }
 109
 110         if (tdb->read_only || tdb->traverse_read) {
 111                 tdb->ecode = TDB_ERR_RDONLY;
 112                 return -1;
 113         }
 114
 115         if (tdb->methods->tdb_oob(tdb, off, len, 0) != 0)
 116                 return -1;
 117
 118         if (tdb->map_ptr) {
 119                 memcpy(off + (char *)tdb->map_ptr, buf, len);
 120         } else {
 121 #ifdef HAVE_INCOHERENT_MMAP
 122                 tdb->ecode = TDB_ERR_IO;
 123                 return -1;
 124 #else
 125                 ssize_t written = pwrite(tdb->fd, buf, len, off);
 126                 if ((written != (ssize_t)len) && (written != -1)) {
 127                         /* try once more */
 128                         tdb->ecode = TDB_ERR_IO;
 129                         TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_write: wrote only "
 130                                  "%zi of %u bytes at %u, trying once more\n",
 131                                  written, len, off));
 132                         written = pwrite(tdb->fd, (const char *)buf+written,
 133                                          len-written,
 134                                          off+written);
 135                 }
 136                 if (written == -1) {
 137                         /* Ensure ecode is set for log fn. */
 138                         tdb->ecode = TDB_ERR_IO;
 139                         TDB_LOG((tdb, TDB_DEBUG_FATAL,"tdb_write failed at %u "
 140                                  "len=%u (%s)\n", off, len, strerror(errno)));
 141                         return -1;
 142                 } else if (written != (ssize_t)len) {
 143                         tdb->ecode = TDB_ERR_IO;
 144                         TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_write: failed to "
 145                                  "write %u bytes at %u in two attempts\n",
 146                                  len, off));
 147                         return -1;
 148                 }
 149 #endif
 150         }
 151         return 0;
 152 }
 153
 154 /* Endian conversion: we only ever deal with 4 byte quantities */
 155 void *tdb_convert(void *buf, uint32_t size)
 156 {
 157         uint32_t i, *p = (uint32_t *)buf;
 158         for (i = 0; i < size / 4; i++)
 159                 p[i] = TDB_BYTEREV(p[i]);
 160         return buf;
 161 }
 162
 163
 164 /* read a lump of data at a specified offset, maybe convert */
 165 static int tdb_read(struct tdb_context *tdb, tdb_off_t off, void *buf,
 166                     tdb_len_t len, int cv)
 167 {
 168         if (tdb->methods->tdb_oob(tdb, off, len, 0) != 0) {
 169                 return -1;
 170         }
 171
 172         if (tdb->map_ptr) {
 173                 memcpy(buf, off + (char *)tdb->map_ptr, len);
 174         } else {
 175 #ifdef HAVE_INCOHERENT_MMAP
 176                 tdb->ecode = TDB_ERR_IO;
 177                 return -1;
 178 #else
 179                 ssize_t ret = pread(tdb->fd, buf, len, off);
 180                 if (ret != (ssize_t)len) {
 181                         /* Ensure ecode is set for log fn. */
 182                         tdb->ecode = TDB_ERR_IO;
 183                         TDB_LOG((tdb, TDB_DEBUG_FATAL,"tdb_read failed at %u "
 184                                  "len=%u ret=%zi (%s) map_size=%u\n",
 185                                  off, len, ret, strerror(errno),
 186                                  tdb->map_size));
 187                         return -1;
 188                 }
 189 #endif
 190         }
 191         if (cv) {
 192                 tdb_convert(buf, len);
 193         }
 194         return 0;
 195 }
 196
 197
 198
 199 /*
 200   do an unlocked scan of the hash table heads to find the next non-zero head. The value
 201   will then be confirmed with the lock held
 202 */
 203 static void tdb_next_hash_chain(struct tdb_context *tdb, uint32_t *chain)
 204 {
 205         uint32_t h = *chain;
 206         if (tdb->map_ptr) {
 207                 for (;h < tdb->hash_size;h++) {
 208                         if (0 != *(uint32_t *)(TDB_HASH_TOP(h) + (unsigned char *)tdb->map_ptr)) {
 209                                 break;
 210                         }
 211                 }
 212         } else {
 213                 uint32_t off=0;
 214                 for (;h < tdb->hash_size;h++) {
 215                         if (tdb_ofs_read(tdb, TDB_HASH_TOP(h), &off) != 0 || off != 0) {
 216                                 break;
 217                         }
 218                 }
 219         }
 220         (*chain) = h;
 221 }
 222
 223
 224 int tdb_munmap(struct tdb_context *tdb)
 225 {
 226         if (tdb->flags & TDB_INTERNAL)
 227                 return 0;
 228
 229 #ifdef HAVE_MMAP
 230         if (tdb->map_ptr) {
 231                 int ret;
 232
 233                 ret = munmap(tdb->map_ptr, tdb->map_size);
 234                 if (ret != 0)
 235                         return ret;
 236         }
 237 #endif
 238         tdb->map_ptr = NULL;
 239         return 0;
 240 }
 241
 242 /* If mmap isn't coherent, *everyone* must always mmap. */
 243 static bool should_mmap(const struct tdb_context *tdb)
 244 {
 245 #ifdef HAVE_INCOHERENT_MMAP
 246         return true;
 247 #else
 248         return !(tdb->flags & TDB_NOMMAP);
 249 #endif
 250 }
 251
 252 int tdb_mmap(struct tdb_context *tdb)
 253 {
 254         if (tdb->flags & TDB_INTERNAL)
 255                 return 0;
 256
 257 #ifdef HAVE_MMAP
 258         if (should_mmap(tdb)) {
 259                 tdb->map_ptr = mmap(NULL, tdb->map_size,
 260                                     PROT_READ|(tdb->read_only? 0:PROT_WRITE),
 261                                     MAP_SHARED|MAP_FILE, tdb->fd, 0);
 262
 263                 /*
 264                  * NB. When mmap fails it returns MAP_FAILED *NOT* NULL !!!!
 265                  */
 266
 267                 if (tdb->map_ptr == MAP_FAILED) {
 268                         tdb->map_ptr = NULL;
 269                         TDB_LOG((tdb, TDB_DEBUG_WARNING, "tdb_mmap failed for size %u (%s)\n",
 270                                  tdb->map_size, strerror(errno)));
 271 #ifdef HAVE_INCOHERENT_MMAP
 272                         tdb->ecode = TDB_ERR_IO;
 273                         return -1;
 274 #endif
 275                 }
 276         } else {
 277                 tdb->map_ptr = NULL;
 278         }
 279 #else
 280         tdb->map_ptr = NULL;
 281 #endif
 282         return 0;
 283 }
 284
 285 /* expand a file.  we prefer to use ftruncate, as that is what posix
 286   says to use for mmap expansion */
 287 static int tdb_expand_file(struct tdb_context *tdb, tdb_off_t size, tdb_off_t addition)
 288 {
 289         char buf[8192];
 290         tdb_off_t new_size;
 291
 292         if (tdb->read_only || tdb->traverse_read) {
 293                 tdb->ecode = TDB_ERR_RDONLY;
 294                 return -1;
 295         }
 296
 297         if (!tdb_add_off_t(size, addition, &new_size)) {
 298                 tdb->ecode = TDB_ERR_OOM;
 299                 TDB_LOG((tdb, TDB_DEBUG_FATAL, "expand_file write "
 300                         "overflow detected current size[%u] addition[%u]!\n",
 301                         (unsigned)size, (unsigned)addition));
 302                 errno = ENOSPC;
 303                 return -1;
 304         }
 305
 306         if (ftruncate(tdb->fd, new_size) == -1) {
 307                 char b = 0;
 308                 ssize_t written = pwrite(tdb->fd,  &b, 1, new_size - 1);
 309                 if (written == 0) {
 310                         /* try once more, potentially revealing errno */
 311                         written = pwrite(tdb->fd,  &b, 1, new_size - 1);
 312                 }
 313                 if (written == 0) {
 314                         /* again - give up, guessing errno */
 315                         errno = ENOSPC;
 316                 }
 317                 if (written != 1) {
 318                         tdb->ecode = TDB_ERR_OOM;
 319                         TDB_LOG((tdb, TDB_DEBUG_FATAL, "expand_file to %u failed (%s)\n",
 320                                  (unsigned)new_size, strerror(errno)));
 321                         return -1;
 322                 }
 323         }
 324
 325         /* now fill the file with something. This ensures that the
 326            file isn't sparse, which would be very bad if we ran out of
 327            disk. This must be done with write, not via mmap */
 328         memset(buf, TDB_PAD_BYTE, sizeof(buf));
 329         while (addition) {
 330                 size_t n = addition>sizeof(buf)?sizeof(buf):addition;
 331                 ssize_t written = pwrite(tdb->fd, buf, n, size);
 332                 if (written == 0) {
 333                         /* prevent infinite loops: try _once_ more */
 334                         written = pwrite(tdb->fd, buf, n, size);
 335                 }
 336                 if (written == 0) {
 337                         /* give up, trying to provide a useful errno */
 338                         tdb->ecode = TDB_ERR_OOM;
 339                         TDB_LOG((tdb, TDB_DEBUG_FATAL, "expand_file write "
 340                                 "returned 0 twice: giving up!\n"));
 341                         errno = ENOSPC;
 342                         return -1;
 343                 }
 344                 if (written == -1) {
 345                         tdb->ecode = TDB_ERR_OOM;
 346                         TDB_LOG((tdb, TDB_DEBUG_FATAL, "expand_file write of "
 347                                  "%u bytes failed (%s)\n", (int)n,
 348                                  strerror(errno)));
 349                         return -1;
 350                 }
 351                 if (written != n) {
 352                         TDB_LOG((tdb, TDB_DEBUG_WARNING, "expand_file: wrote "
 353                                  "only %zu of %zi bytes - retrying\n", written,
 354                                  n));
 355                 }
 356                 addition -= written;
 357                 size += written;
 358         }
 359         return 0;
 360 }
 361
 362
 363 /* You need 'size', this tells you how much you should expand by. */
 364 tdb_off_t tdb_expand_adjust(tdb_off_t map_size, tdb_off_t size, int page_size)
 365 {
 366         tdb_off_t new_size, top_size, increment;
 367         tdb_off_t max_size = UINT32_MAX - map_size;
 368
 369         if (size > max_size) {
 370                 /*
 371                  * We can't round up anymore, just give back
 372                  * what we're asked for.
 373                  *
 374                  * The caller has to take care of the ENOSPC handling.
 375                  */
 376                 return size;
 377         }
 378
 379         /* limit size in order to avoid using up huge amounts of memory for
 380          * in memory tdbs if an oddball huge record creeps in */
 381         if (size > 100 * 1024) {
 382                 increment = size * 2;
 383         } else {
 384                 increment = size * 100;
 385         }
 386         if (increment < size) {
 387                 goto overflow;
 388         }
 389
 390         if (!tdb_add_off_t(map_size, increment, &top_size)) {
 391                 goto overflow;
 392         }
 393
 394         /* always make room for at least top_size more records, and at
 395            least 25% more space. if the DB is smaller than 100MiB,
 396            otherwise grow it by 10% only. */
 397         if (map_size > 100 * 1024 * 1024) {
 398                 new_size = map_size * 1.10;
 399         } else {
 400                 new_size = map_size * 1.25;
 401         }
 402         if (new_size < map_size) {
 403                 goto overflow;
 404         }
 405
 406         /* Round the database up to a multiple of the page size */
 407         new_size = MAX(top_size, new_size);
 408
 409         if (new_size + page_size < new_size) {
 410                 /* There's a "+" in TDB_ALIGN that might overflow... */
 411                 goto overflow;
 412         }
 413
 414         return TDB_ALIGN(new_size, page_size) - map_size;
 415
 416 overflow:
 417         /*
 418          * Somewhere in between we went over 4GB. Make one big jump to
 419          * exactly 4GB database size.
 420          */
 421         return max_size;
 422 }
 423
 424 /* expand the database at least size bytes by expanding the underlying
 425    file and doing the mmap again if necessary */
 426 int tdb_expand(struct tdb_context *tdb, tdb_off_t size)
 427 {
 428         struct tdb_record rec;
 429         tdb_off_t offset;
 430         tdb_off_t new_size;
 431
 432         if (tdb_lock(tdb, -1, F_WRLCK) == -1) {
 433                 TDB_LOG((tdb, TDB_DEBUG_ERROR, "lock failed in tdb_expand\n"));
 434                 return -1;
 435         }
 436
 437         /* must know about any previous expansions by another process */
 438         tdb->methods->tdb_oob(tdb, tdb->map_size, 1, 1);
 439
 440         size = tdb_expand_adjust(tdb->map_size, size, tdb->page_size);
 441
 442         if (!tdb_add_off_t(tdb->map_size, size, &new_size)) {
 443                 tdb->ecode = TDB_ERR_OOM;
 444                 TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_expand "
 445                         "overflow detected current map_size[%u] size[%u]!\n",
 446                         (unsigned)tdb->map_size, (unsigned)size));
 447                 goto fail;
 448         }
 449
 450         /* form a new freelist record */
 451         offset = tdb->map_size;
 452         memset(&rec,'\0',sizeof(rec));
 453         rec.rec_len = size - sizeof(rec);
 454
 455         if (tdb->flags & TDB_INTERNAL) {
 456                 char *new_map_ptr;
 457
 458                 new_map_ptr = (char *)realloc(tdb->map_ptr, new_size);
 459                 if (!new_map_ptr) {
 460                         tdb->ecode = TDB_ERR_OOM;
 461                         goto fail;
 462                 }
 463                 tdb->map_ptr = new_map_ptr;
 464                 tdb->map_size = new_size;
 465         } else {
 466                 int ret;
 467
 468                 /*
 469                  * expand the file itself
 470                  */
 471                 ret = tdb->methods->tdb_expand_file(tdb, tdb->map_size, size);
 472                 if (ret != 0) {
 473                         goto fail;
 474                 }
 475
 476                 /* Explicitly remap: if we're in a transaction, this won't
 477                  * happen automatically! */
 478                 tdb_munmap(tdb);
 479                 tdb->map_size = new_size;
 480                 if (tdb_mmap(tdb) != 0) {
 481                         goto fail;
 482                 }
 483         }
 484
 485         /* link it into the free list */
 486         if (tdb_free(tdb, offset, &rec) == -1)
 487                 goto fail;
 488
 489         tdb_unlock(tdb, -1, F_WRLCK);
 490         return 0;
 491  fail:
 492         tdb_unlock(tdb, -1, F_WRLCK);
 493         return -1;
 494 }
 495
 496 /* read/write a tdb_off_t */
 497 int tdb_ofs_read(struct tdb_context *tdb, tdb_off_t offset, tdb_off_t *d)
 498 {
 499         return tdb->methods->tdb_read(tdb, offset, (char*)d, sizeof(*d), DOCONV());
 500 }
 501
 502 int tdb_ofs_write(struct tdb_context *tdb, tdb_off_t offset, tdb_off_t *d)
 503 {
 504         tdb_off_t off = *d;
 505         return tdb->methods->tdb_write(tdb, offset, CONVERT(off), sizeof(*d));
 506 }
 507
 508
 509 /* read a lump of data, allocating the space for it */
 510 unsigned char *tdb_alloc_read(struct tdb_context *tdb, tdb_off_t offset, tdb_len_t len)
 511 {
 512         unsigned char *buf;
 513
 514         /* some systems don't like zero length malloc */
 515
 516         if (!(buf = (unsigned char *)malloc(len ? len : 1))) {
 517                 /* Ensure ecode is set for log fn. */
 518                 tdb->ecode = TDB_ERR_OOM;
 519                 TDB_LOG((tdb, TDB_DEBUG_ERROR,"tdb_alloc_read malloc failed len=%u (%s)\n",
 520                            len, strerror(errno)));
 521                 return NULL;
 522         }
 523         if (tdb->methods->tdb_read(tdb, offset, buf, len, 0) == -1) {
 524                 SAFE_FREE(buf);
 525                 return NULL;
 526         }
 527         return buf;
 528 }
 529
 530 /* Give a piece of tdb data to a parser */
 531
 532 int tdb_parse_data(struct tdb_context *tdb, TDB_DATA key,
 533                    tdb_off_t offset, tdb_len_t len,
 534                    int (*parser)(TDB_DATA key, TDB_DATA data,
 535                                  void *private_data),
 536                    void *private_data)
 537 {
 538         TDB_DATA data;
 539         int result;
 540
 541         data.dsize = len;
 542
 543         if ((tdb->transaction == NULL) && (tdb->map_ptr != NULL)) {
 544                 /*
 545                  * Optimize by avoiding the malloc/memcpy/free, point the
 546                  * parser directly at the mmap area.
 547                  */
 548                 if (tdb->methods->tdb_oob(tdb, offset, len, 0) != 0) {
 549                         return -1;
 550                 }
 551                 data.dptr = offset + (unsigned char *)tdb->map_ptr;
 552                 return parser(key, data, private_data);
 553         }
 554
 555         if (!(data.dptr = tdb_alloc_read(tdb, offset, len))) {
 556                 return -1;
 557         }
 558
 559         result = parser(key, data, private_data);
 560         free(data.dptr);
 561         return result;
 562 }
 563
 564 /* read/write a record */
 565 int tdb_rec_read(struct tdb_context *tdb, tdb_off_t offset, struct tdb_record *rec)
 566 {
 567         if (tdb->methods->tdb_read(tdb, offset, rec, sizeof(*rec),DOCONV()) == -1)
 568                 return -1;
 569         if (TDB_BAD_MAGIC(rec)) {
 570                 /* Ensure ecode is set for log fn. */
 571                 tdb->ecode = TDB_ERR_CORRUPT;
 572                 TDB_LOG((tdb, TDB_DEBUG_FATAL,"tdb_rec_read bad magic 0x%x at offset=%u\n", rec->magic, offset));
 573                 return -1;
 574         }
 575         return tdb->methods->tdb_oob(tdb, rec->next, sizeof(*rec), 0);
 576 }
 577
 578 int tdb_rec_write(struct tdb_context *tdb, tdb_off_t offset, struct tdb_record *rec)
 579 {
 580         struct tdb_record r = *rec;
 581         return tdb->methods->tdb_write(tdb, offset, CONVERT(r), sizeof(r));
 582 }
 583
 584 static const struct tdb_methods io_methods = {
 585         tdb_read,
 586         tdb_write,
 587         tdb_next_hash_chain,
 588         tdb_oob,
 589         tdb_expand_file,
 590 };
 591
 592 /*
 593   initialise the default methods table
 594 */
 595 void tdb_io_init(struct tdb_context *tdb)
 596 {
 597         tdb->methods = &io_methods;
 598 }