e2fsck/ea_refcount.c

   1 /*
   2  * ea_refcount.c
   3  *
   4  * Copyright (C) 2001 Theodore Ts'o.  This file may be
   5  * redistributed under the terms of the GNU Public License.
   6  */
   7
   8 #if HAVE_UNISTD_H
   9 #include <unistd.h>
  10 #endif
  11 #include <string.h>
  12 #include <stdio.h>
  13
  14 #ifdef TEST_PROGRAM
  15 #undef ENABLE_NLS
  16 #endif
  17 #include "e2fsck.h"
  18
  19 /*
  20  * The strategy we use for keeping track of EA refcounts is as
  21  * follows.  We keep a sorted array of first EA blocks and its
  22  * reference counts.  Once the refcount has dropped to zero, it is
  23  * removed from the array to save memory space.  Once the EA block is
  24  * checked, its bit is set in the block_ea_map bitmap.
  25  */
  26 struct ea_refcount_el {
  27         blk_t   ea_blk;
  28         int     ea_count;
  29 };
  30
  31 struct ea_refcount {
  32         blk_t           count;
  33         blk_t           size;
  34         blk_t           cursor;
  35         struct ea_refcount_el   *list;
  36 };
  37
  38 void ea_refcount_free(ext2_refcount_t refcount)
  39 {
  40         if (!refcount)
  41                 return;
  42
  43         if (refcount->list)
  44                 ext2fs_free_mem(&refcount->list);
  45         ext2fs_free_mem(&refcount);
  46 }
  47
  48 errcode_t ea_refcount_create(int size, ext2_refcount_t *ret)
  49 {
  50         ext2_refcount_t refcount;
  51         errcode_t       retval;
  52         size_t          bytes;
  53
  54         retval = ext2fs_get_mem(sizeof(struct ea_refcount), &refcount);
  55         if (retval)
  56                 return retval;
  57         memset(refcount, 0, sizeof(struct ea_refcount));
  58
  59         if (!size)
  60                 size = 500;
  61         refcount->size = size;
  62         bytes = (size_t) (size * sizeof(struct ea_refcount_el));
  63 #ifdef DEBUG
  64         printf("Refcount allocated %d entries, %d bytes.\n",
  65                refcount->size, bytes);
  66 #endif
  67         retval = ext2fs_get_mem(bytes, &refcount->list);
  68         if (retval)
  69                 goto errout;
  70         memset(refcount->list, 0, bytes);
  71
  72         refcount->count = 0;
  73         refcount->cursor = 0;
  74
  75         *ret = refcount;
  76         return 0;
  77
  78 errout:
  79         ea_refcount_free(refcount);
  80         return(retval);
  81 }
  82
  83 /*
  84  * collapse_refcount() --- go through the refcount array, and get rid
  85  * of any count == zero entries
  86  */
  87 static void refcount_collapse(ext2_refcount_t refcount)
  88 {
  89         unsigned int    i, j;
  90         struct ea_refcount_el   *list;
  91
  92         list = refcount->list;
  93         for (i = 0, j = 0; i < refcount->count; i++) {
  94                 if (list[i].ea_count) {
  95                         if (i != j)
  96                                 list[j] = list[i];
  97                         j++;
  98                 }
  99         }
 100 #if defined(DEBUG) || defined(TEST_PROGRAM)
 101         printf("Refcount_collapse: size was %d, now %d\n",
 102                refcount->count, j);
 103 #endif
 104         refcount->count = j;
 105 }
 106
 107
 108 /*
 109  * insert_refcount_el() --- Insert a new entry into the sorted list at a
 110  *      specified position.
 111  */
 112 static struct ea_refcount_el *insert_refcount_el(ext2_refcount_t refcount,
 113                                                  blk_t blk, int pos)
 114 {
 115         struct ea_refcount_el   *el;
 116         errcode_t               retval;
 117         blk_t                   new_size = 0;
 118         int                     num;
 119
 120         if (refcount->count >= refcount->size) {
 121                 new_size = refcount->size + 100;
 122 #ifdef DEBUG
 123                 printf("Reallocating refcount %d entries...\n", new_size);
 124 #endif
 125                 retval = ext2fs_resize_mem((size_t) refcount->size *
 126                                            sizeof(struct ea_refcount_el),
 127                                            (size_t) new_size *
 128                                            sizeof(struct ea_refcount_el),
 129                                            &refcount->list);
 130                 if (retval)
 131                         return 0;
 132                 refcount->size = new_size;
 133         }
 134         num = (int) refcount->count - pos;
 135         if (num < 0)
 136                 return 0;       /* should never happen */
 137         if (num) {
 138                 memmove(&refcount->list[pos+1], &refcount->list[pos],
 139                         sizeof(struct ea_refcount_el) * num);
 140         }
 141         refcount->count++;
 142         el = &refcount->list[pos];
 143         el->ea_count = 0;
 144         el->ea_blk = blk;
 145         return el;
 146 }
 147
 148
 149 /*
 150  * get_refcount_el() --- given an block number, try to find refcount
 151  *      information in the sorted list.  If the create flag is set,
 152  *      and we can't find an entry, create one in the sorted list.
 153  */
 154 static struct ea_refcount_el *get_refcount_el(ext2_refcount_t refcount,
 155                                               blk_t blk, int create)
 156 {
 157         float   range;
 158         int     low, high, mid;
 159         blk_t   lowval, highval;
 160
 161         if (!refcount || !refcount->list)
 162                 return 0;
 163 retry:
 164         low = 0;
 165         high = (int) refcount->count-1;
 166         if (create && ((refcount->count == 0) ||
 167                        (blk > refcount->list[high].ea_blk))) {
 168                 if (refcount->count >= refcount->size)
 169                         refcount_collapse(refcount);
 170
 171                 return insert_refcount_el(refcount, blk,
 172                                           (unsigned) refcount->count);
 173         }
 174         if (refcount->count == 0)
 175                 return 0;
 176
 177         if (refcount->cursor >= refcount->count)
 178                 refcount->cursor = 0;
 179         if (blk == refcount->list[refcount->cursor].ea_blk)
 180                 return &refcount->list[refcount->cursor++];
 181 #ifdef DEBUG
 182         printf("Non-cursor get_refcount_el: %u\n", blk);
 183 #endif
 184         while (low <= high) {
 185 #if 0
 186                 mid = (low+high)/2;
 187 #else
 188                 if (low == high)
 189                         mid = low;
 190                 else {
 191                         /* Interpolate for efficiency */
 192                         lowval = refcount->list[low].ea_blk;
 193                         highval = refcount->list[high].ea_blk;
 194
 195                         if (blk < lowval)
 196                                 range = 0;
 197                         else if (blk > highval)
 198                                 range = 1;
 199                         else {
 200                                 range = ((float) (blk - lowval)) /
 201                                         (highval - lowval);
 202                                 if (range > 0.9)
 203                                         range = 0.9;
 204                                 if (range < 0.1)
 205                                         range = 0.1;
 206                         }
 207                         mid = low + ((int) (range * (high-low)));
 208                 }
 209 #endif
 210                 if (blk == refcount->list[mid].ea_blk) {
 211                         refcount->cursor = mid+1;
 212                         return &refcount->list[mid];
 213                 }
 214                 if (blk < refcount->list[mid].ea_blk)
 215                         high = mid-1;
 216                 else
 217                         low = mid+1;
 218         }
 219         /*
 220          * If we need to create a new entry, it should be right at
 221          * low (where high will be left at low-1).
 222          */
 223         if (create) {
 224                 if (refcount->count >= refcount->size) {
 225                         refcount_collapse(refcount);
 226                         if (refcount->count < refcount->size)
 227                                 goto retry;
 228                 }
 229                 return insert_refcount_el(refcount, blk, low);
 230         }
 231         return 0;
 232 }
 233
 234 errcode_t ea_refcount_fetch(ext2_refcount_t refcount, blk_t blk,
 235                                 int *ret)
 236 {
 237         struct ea_refcount_el   *el;
 238
 239         el = get_refcount_el(refcount, blk, 0);
 240         if (!el) {
 241                 *ret = 0;
 242                 return 0;
 243         }
 244         *ret = el->ea_count;
 245         return 0;
 246 }
 247
 248 errcode_t ea_refcount_increment(ext2_refcount_t refcount, blk_t blk, int *ret)
 249 {
 250         struct ea_refcount_el   *el;
 251
 252         el = get_refcount_el(refcount, blk, 1);
 253         if (!el)
 254                 return EXT2_ET_NO_MEMORY;
 255         el->ea_count++;
 256
 257         if (ret)
 258                 *ret = el->ea_count;
 259         return 0;
 260 }
 261
 262 errcode_t ea_refcount_decrement(ext2_refcount_t refcount, blk_t blk, int *ret)
 263 {
 264         struct ea_refcount_el   *el;
 265
 266         el = get_refcount_el(refcount, blk, 0);
 267         if (!el || el->ea_count == 0)
 268                 return EXT2_ET_INVALID_ARGUMENT;
 269
 270         el->ea_count--;
 271
 272         if (ret)
 273                 *ret = el->ea_count;
 274         return 0;
 275 }
 276
 277 errcode_t ea_refcount_store(ext2_refcount_t refcount, blk_t blk, int count)
 278 {
 279         struct ea_refcount_el   *el;
 280
 281         /*
 282          * Get the refcount element
 283          */
 284         el = get_refcount_el(refcount, blk, count ? 1 : 0);
 285         if (!el)
 286                 return count ? EXT2_ET_NO_MEMORY : 0;
 287         el->ea_count = count;
 288         return 0;
 289 }
 290
 291 blk_t ext2fs_get_refcount_size(ext2_refcount_t refcount)
 292 {
 293         if (!refcount)
 294                 return 0;
 295
 296         return refcount->size;
 297 }
 298
 299 void ea_refcount_intr_begin(ext2_refcount_t refcount)
 300 {
 301         refcount->cursor = 0;
 302 }
 303
 304
 305 blk_t ea_refcount_intr_next(ext2_refcount_t refcount,
 306                                 int *ret)
 307 {
 308         struct ea_refcount_el   *list;
 309
 310         while (1) {
 311                 if (refcount->cursor >= refcount->count)
 312                         return 0;
 313                 list = refcount->list;
 314                 if (list[refcount->cursor].ea_count) {
 315                         if (ret)
 316                                 *ret = list[refcount->cursor].ea_count;
 317                         return list[refcount->cursor++].ea_blk;
 318                 }
 319                 refcount->cursor++;
 320         }
 321 }
 322
 323
 324 #ifdef TEST_PROGRAM
 325
 326 errcode_t ea_refcount_validate(ext2_refcount_t refcount, FILE *out)
 327 {
 328         errcode_t       ret = 0;
 329         int             i;
 330         const char *bad = "bad refcount";
 331
 332         if (refcount->count > refcount->size) {
 333                 fprintf(out, "%s: count > size\n", bad);
 334                 return EXT2_ET_INVALID_ARGUMENT;
 335         }
 336         for (i=1; i < refcount->count; i++) {
 337                 if (refcount->list[i-1].ea_blk >= refcount->list[i].ea_blk) {
 338                         fprintf(out, "%s: list[%d].blk=%u, list[%d].blk=%u\n",
 339                                 bad, i-1, refcount->list[i-1].ea_blk,
 340                                 i, refcount->list[i].ea_blk);
 341                         ret = EXT2_ET_INVALID_ARGUMENT;
 342                 }
 343         }
 344         return ret;
 345 }
 346
 347 #define BCODE_END       0
 348 #define BCODE_CREATE    1
 349 #define BCODE_FREE      2
 350 #define BCODE_STORE     3
 351 #define BCODE_INCR      4
 352 #define BCODE_DECR      5
 353 #define BCODE_FETCH     6
 354 #define BCODE_VALIDATE  7
 355 #define BCODE_LIST      8
 356 #define BCODE_COLLAPSE 9
 357
 358 int bcode_program[] = {
 359         BCODE_CREATE, 5,
 360         BCODE_STORE, 3, 3,
 361         BCODE_STORE, 4, 4,
 362         BCODE_STORE, 1, 1,
 363         BCODE_STORE, 8, 8,
 364         BCODE_STORE, 2, 2,
 365         BCODE_STORE, 4, 0,
 366         BCODE_STORE, 2, 0,
 367         BCODE_STORE, 6, 6,
 368         BCODE_VALIDATE,
 369         BCODE_STORE, 4, 4,
 370         BCODE_STORE, 2, 2,
 371         BCODE_FETCH, 1,
 372         BCODE_FETCH, 2,
 373         BCODE_INCR, 3,
 374         BCODE_INCR, 3,
 375         BCODE_DECR, 4,
 376         BCODE_STORE, 4, 4,
 377         BCODE_VALIDATE,
 378         BCODE_STORE, 20, 20,
 379         BCODE_STORE, 40, 40,
 380         BCODE_STORE, 30, 30,
 381         BCODE_STORE, 10, 10,
 382         BCODE_DECR, 30,
 383         BCODE_FETCH, 30,
 384         BCODE_DECR, 2,
 385         BCODE_DECR, 2,
 386         BCODE_COLLAPSE,
 387         BCODE_LIST,
 388         BCODE_VALIDATE,
 389         BCODE_FREE,
 390         BCODE_END
 391 };
 392
 393 int main(int argc, char **argv)
 394 {
 395         int     i = 0;
 396         ext2_refcount_t refcount;
 397         int             size, arg;
 398         blk_t           blk;
 399         errcode_t       retval;
 400
 401         while (1) {
 402                 switch (bcode_program[i++]) {
 403                 case BCODE_END:
 404                         exit(0);
 405                 case BCODE_CREATE:
 406                         size = bcode_program[i++];
 407                         retval = ea_refcount_create(size, &refcount);
 408                         if (retval) {
 409                                 com_err("ea_refcount_create",
 410                                         retval, "");
 411                                 exit(1);
 412                         } else
 413                                 printf("Creating refcount with size %d\n",
 414                                        size);
 415                         break;
 416                 case BCODE_FREE:
 417                         ea_refcount_free(refcount);
 418                         refcount = 0;
 419                         printf("Freeing refcount\n");
 420                         break;
 421                 case BCODE_STORE:
 422                         blk = (blk_t) bcode_program[i++];
 423                         arg = bcode_program[i++];
 424                         retval = ea_refcount_store(refcount, blk, arg);
 425                         printf("Storing blk %u with value %d\n", blk, arg);
 426                         if (retval)
 427                                 com_err("ea_refcount_store", retval, "");
 428                         break;
 429                 case BCODE_FETCH:
 430                         blk = (blk_t) bcode_program[i++];
 431                         retval = ea_refcount_fetch(refcount, blk, &arg);
 432                         if (retval)
 433                                 com_err("ea_refcount_fetch", retval, "");
 434                         else
 435                                 printf("bcode_fetch(%u) returns %d\n",
 436                                        blk, arg);
 437                         break;
 438                 case BCODE_INCR:
 439                         blk = (blk_t) bcode_program[i++];
 440                         retval = ea_refcount_increment(refcount, blk,
 441                                                            &arg);
 442                         if (retval)
 443                                 com_err("ea_refcount_increment", retval,
 444                                         "");
 445                         else
 446                                 printf("bcode_increment(%u) returns %d\n",
 447                                        blk, arg);
 448                         break;
 449                 case BCODE_DECR:
 450                         blk = (blk_t) bcode_program[i++];
 451                         retval = ea_refcount_decrement(refcount, blk,
 452                                                            &arg);
 453                         if (retval)
 454                                 com_err("ea_refcount_decrement", retval,
 455                                         "while decrementing blk %u", blk);
 456                         else
 457                                 printf("bcode_decrement(%u) returns %d\n",
 458                                        blk, arg);
 459                         break;
 460                 case BCODE_VALIDATE:
 461                         retval = ea_refcount_validate(refcount, stderr);
 462                         if (retval)
 463                                 com_err("ea_refcount_validate",
 464                                         retval, "");
 465                         else
 466                                 printf("Refcount validation OK.\n");
 467                         break;
 468                 case BCODE_LIST:
 469                         ea_refcount_intr_begin(refcount);
 470                         while (1) {
 471                                 blk = ea_refcount_intr_next(refcount,
 472                                                                 &arg);
 473                                 if (!blk)
 474                                         break;
 475                                 printf("\tblk=%u, count=%d\n", blk,
 476                                        arg);
 477                         }
 478                         break;
 479                 case BCODE_COLLAPSE:
 480                         refcount_collapse(refcount);
 481                         break;
 482                 }
 483
 484         }
 485 }
 486
 487 #endif