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