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