fs/ubifs/find.c

   1 /*
   2  * This file is part of UBIFS.
   3  *
   4  * Copyright (C) 2006-2008 Nokia Corporation.
   5  *
   6  * This program is free software; you can redistribute it and/or modify it
   7  * under the terms of the GNU General Public License version 2 as published by
   8  * the Free Software Foundation.
   9  *
  10  * This program is distributed in the hope that it will be useful, but WITHOUT
  11  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  12  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
  13  * more details.
  14  *
  15  * You should have received a copy of the GNU General Public License along with
  16  * this program; if not, write to the Free Software Foundation, Inc., 51
  17  * Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
  18  *
  19  * Authors: Artem Bityutskiy (Битюцкий Артём)
  20  *          Adrian Hunter
  21  */
  22
  23 /*
  24  * This file contains functions for finding LEBs for various purposes e.g.
  25  * garbage collection. In general, lprops category heaps and lists are used
  26  * for fast access, falling back on scanning the LPT as a last resort.
  27  */
  28
  29 #include <linux/sort.h>
  30 #include "ubifs.h"
  31
  32 /**
  33  * struct scan_data - data provided to scan callback functions
  34  * @min_space: minimum number of bytes for which to scan
  35  * @pick_free: whether it is OK to scan for empty LEBs
  36  * @lnum: LEB number found is returned here
  37  * @exclude_index: whether to exclude index LEBs
  38  */
  39 struct scan_data {
  40         int min_space;
  41         int pick_free;
  42         int lnum;
  43         int exclude_index;
  44 };
  45
  46 /**
  47  * valuable - determine whether LEB properties are valuable.
  48  * @c: the UBIFS file-system description object
  49  * @lprops: LEB properties
  50  *
  51  * This function return %1 if the LEB properties should be added to the LEB
  52  * properties tree in memory. Otherwise %0 is returned.
  53  */
  54 static int valuable(struct ubifs_info *c, const struct ubifs_lprops *lprops)
  55 {
  56         int n, cat = lprops->flags & LPROPS_CAT_MASK;
  57         struct ubifs_lpt_heap *heap;
  58
  59         switch (cat) {
  60         case LPROPS_DIRTY:
  61         case LPROPS_DIRTY_IDX:
  62         case LPROPS_FREE:
  63                 heap = &c->lpt_heap[cat - 1];
  64                 if (heap->cnt < heap->max_cnt)
  65                         return 1;
  66                 if (lprops->free + lprops->dirty >= c->dark_wm)
  67                         return 1;
  68                 return 0;
  69         case LPROPS_EMPTY:
  70                 n = c->lst.empty_lebs + c->freeable_cnt -
  71                     c->lst.taken_empty_lebs;
  72                 if (n < c->lsave_cnt)
  73                         return 1;
  74                 return 0;
  75         case LPROPS_FREEABLE:
  76                 return 1;
  77         case LPROPS_FRDI_IDX:
  78                 return 1;
  79         }
  80         return 0;
  81 }
  82
  83 /**
  84  * scan_for_dirty_cb - dirty space scan callback.
  85  * @c: the UBIFS file-system description object
  86  * @lprops: LEB properties to scan
  87  * @in_tree: whether the LEB properties are in main memory
  88  * @data: information passed to and from the caller of the scan
  89  *
  90  * This function returns a code that indicates whether the scan should continue
  91  * (%LPT_SCAN_CONTINUE), whether the LEB properties should be added to the tree
  92  * in main memory (%LPT_SCAN_ADD), or whether the scan should stop
  93  * (%LPT_SCAN_STOP).
  94  */
  95 static int scan_for_dirty_cb(struct ubifs_info *c,
  96                              const struct ubifs_lprops *lprops, int in_tree,
  97                              struct scan_data *data)
  98 {
  99         int ret = LPT_SCAN_CONTINUE;
 100
 101         /* Exclude LEBs that are currently in use */
 102         if (lprops->flags & LPROPS_TAKEN)
 103                 return LPT_SCAN_CONTINUE;
 104         /* Determine whether to add these LEB properties to the tree */
 105         if (!in_tree && valuable(c, lprops))
 106                 ret |= LPT_SCAN_ADD;
 107         /* Exclude LEBs with too little space */
 108         if (lprops->free + lprops->dirty < data->min_space)
 109                 return ret;
 110         /* If specified, exclude index LEBs */
 111         if (data->exclude_index && lprops->flags & LPROPS_INDEX)
 112                 return ret;
 113         /* If specified, exclude empty or freeable LEBs */
 114         if (lprops->free + lprops->dirty == c->leb_size) {
 115                 if (!data->pick_free)
 116                         return ret;
 117         /* Exclude LEBs with too little dirty space (unless it is empty) */
 118         } else if (lprops->dirty < c->dead_wm)
 119                 return ret;
 120         /* Finally we found space */
 121         data->lnum = lprops->lnum;
 122         return LPT_SCAN_ADD | LPT_SCAN_STOP;
 123 }
 124
 125 /**
 126  * scan_for_dirty - find a data LEB with free space.
 127  * @c: the UBIFS file-system description object
 128  * @min_space: minimum amount free plus dirty space the returned LEB has to
 129  *             have
 130  * @pick_free: if it is OK to return a free or freeable LEB
 131  * @exclude_index: whether to exclude index LEBs
 132  *
 133  * This function returns a pointer to the LEB properties found or a negative
 134  * error code.
 135  */
 136 static const struct ubifs_lprops *scan_for_dirty(struct ubifs_info *c,
 137                                                  int min_space, int pick_free,
 138                                                  int exclude_index)
 139 {
 140         const struct ubifs_lprops *lprops;
 141         struct ubifs_lpt_heap *heap;
 142         struct scan_data data;
 143         int err, i;
 144
 145         /* There may be an LEB with enough dirty space on the free heap */
 146         heap = &c->lpt_heap[LPROPS_FREE - 1];
 147         for (i = 0; i < heap->cnt; i++) {
 148                 lprops = heap->arr[i];
 149                 if (lprops->free + lprops->dirty < min_space)
 150                         continue;
 151                 if (lprops->dirty < c->dead_wm)
 152                         continue;
 153                 return lprops;
 154         }
 155         /*
 156          * A LEB may have fallen off of the bottom of the dirty heap, and ended
 157          * up as uncategorized even though it has enough dirty space for us now,
 158          * so check the uncategorized list. N.B. neither empty nor freeable LEBs
 159          * can end up as uncategorized because they are kept on lists not
 160          * finite-sized heaps.
 161          */
 162         list_for_each_entry(lprops, &c->uncat_list, list) {
 163                 if (lprops->flags & LPROPS_TAKEN)
 164                         continue;
 165                 if (lprops->free + lprops->dirty < min_space)
 166                         continue;
 167                 if (exclude_index && (lprops->flags & LPROPS_INDEX))
 168                         continue;
 169                 if (lprops->dirty < c->dead_wm)
 170                         continue;
 171                 return lprops;
 172         }
 173         /* We have looked everywhere in main memory, now scan the flash */
 174         if (c->pnodes_have >= c->pnode_cnt)
 175                 /* All pnodes are in memory, so skip scan */
 176                 return ERR_PTR(-ENOSPC);
 177         data.min_space = min_space;
 178         data.pick_free = pick_free;
 179         data.lnum = -1;
 180         data.exclude_index = exclude_index;
 181         err = ubifs_lpt_scan_nolock(c, -1, c->lscan_lnum,
 182                                     (ubifs_lpt_scan_callback)scan_for_dirty_cb,
 183                                     &data);
 184         if (err)
 185                 return ERR_PTR(err);
 186         ubifs_assert(data.lnum >= c->main_first && data.lnum < c->leb_cnt);
 187         c->lscan_lnum = data.lnum;
 188         lprops = ubifs_lpt_lookup_dirty(c, data.lnum);
 189         if (IS_ERR(lprops))
 190                 return lprops;
 191         ubifs_assert(lprops->lnum == data.lnum);
 192         ubifs_assert(lprops->free + lprops->dirty >= min_space);
 193         ubifs_assert(lprops->dirty >= c->dead_wm ||
 194                      (pick_free &&
 195                       lprops->free + lprops->dirty == c->leb_size));
 196         ubifs_assert(!(lprops->flags & LPROPS_TAKEN));
 197         ubifs_assert(!exclude_index || !(lprops->flags & LPROPS_INDEX));
 198         return lprops;
 199 }
 200
 201 /**
 202  * ubifs_find_dirty_leb - find a dirty LEB for the Garbage Collector.
 203  * @c: the UBIFS file-system description object
 204  * @ret_lp: LEB properties are returned here on exit
 205  * @min_space: minimum amount free plus dirty space the returned LEB has to
 206  *             have
 207  * @pick_free: controls whether it is OK to pick empty or index LEBs
 208  *
 209  * This function tries to find a dirty logical eraseblock which has at least
 210  * @min_space free and dirty space. It prefers to take an LEB from the dirty or
 211  * dirty index heap, and it falls-back to LPT scanning if the heaps are empty
 212  * or do not have an LEB which satisfies the @min_space criteria.
 213  *
 214  * Note:
 215  *   o LEBs which have less than dead watermark of dirty space are never picked
 216  *   by this function;
 217  *
 218  * Returns zero and the LEB properties of
 219  * found dirty LEB in case of success, %-ENOSPC if no dirty LEB was found and a
 220  * negative error code in case of other failures. The returned LEB is marked as
 221  * "taken".
 222  *
 223  * The additional @pick_free argument controls if this function has to return a
 224  * free or freeable LEB if one is present. For example, GC must to set it to %1,
 225  * when called from the journal space reservation function, because the
 226  * appearance of free space may coincide with the loss of enough dirty space
 227  * for GC to succeed anyway.
 228  *
 229  * In contrast, if the Garbage Collector is called from budgeting, it should
 230  * just make free space, not return LEBs which are already free or freeable.
 231  *
 232  * In addition @pick_free is set to %2 by the recovery process in order to
 233  * recover gc_lnum in which case an index LEB must not be returned.
 234  */
 235 int ubifs_find_dirty_leb(struct ubifs_info *c, struct ubifs_lprops *ret_lp,
 236                          int min_space, int pick_free)
 237 {
 238         int err = 0, sum, exclude_index = pick_free == 2 ? 1 : 0;
 239         const struct ubifs_lprops *lp = NULL, *idx_lp = NULL;
 240         struct ubifs_lpt_heap *heap, *idx_heap;
 241
 242         ubifs_get_lprops(c);
 243
 244         if (pick_free) {
 245                 int lebs, rsvd_idx_lebs = 0;
 246
 247                 spin_lock(&c->space_lock);
 248                 lebs = c->lst.empty_lebs;
 249                 lebs += c->freeable_cnt - c->lst.taken_empty_lebs;
 250
 251                 /*
 252                  * Note, the index may consume more LEBs than have been reserved
 253                  * for it. It is OK because it might be consolidated by GC.
 254                  * But if the index takes fewer LEBs than it is reserved for it,
 255                  * this function must avoid picking those reserved LEBs.
 256                  */
 257                 if (c->min_idx_lebs >= c->lst.idx_lebs) {
 258                         rsvd_idx_lebs = c->min_idx_lebs -  c->lst.idx_lebs;
 259                         exclude_index = 1;
 260                 }
 261                 spin_unlock(&c->space_lock);
 262
 263                 /* Check if there are enough free LEBs for the index */
 264                 if (rsvd_idx_lebs < lebs) {
 265                         /* OK, try to find an empty LEB */
 266                         lp = ubifs_fast_find_empty(c);
 267                         if (lp)
 268                                 goto found;
 269
 270                         /* Or a freeable LEB */
 271                         lp = ubifs_fast_find_freeable(c);
 272                         if (lp)
 273                                 goto found;
 274                 } else
 275                         /*
 276                          * We cannot pick free/freeable LEBs in the below code.
 277                          */
 278                         pick_free = 0;
 279         } else {
 280                 spin_lock(&c->space_lock);
 281                 exclude_index = (c->min_idx_lebs >= c->lst.idx_lebs);
 282                 spin_unlock(&c->space_lock);
 283         }
 284
 285         /* Look on the dirty and dirty index heaps */
 286         heap = &c->lpt_heap[LPROPS_DIRTY - 1];
 287         idx_heap = &c->lpt_heap[LPROPS_DIRTY_IDX - 1];
 288
 289         if (idx_heap->cnt && !exclude_index) {
 290                 idx_lp = idx_heap->arr[0];
 291                 sum = idx_lp->free + idx_lp->dirty;
 292                 /*
 293                  * Since we reserve twice as more space for the index than it
 294                  * actually takes, it does not make sense to pick indexing LEBs
 295                  * with less than half LEB of dirty space.
 296                  */
 297                 if (sum < min_space || sum < c->half_leb_size)
 298                         idx_lp = NULL;
 299         }
 300
 301         if (heap->cnt) {
 302                 lp = heap->arr[0];
 303                 if (lp->dirty + lp->free < min_space)
 304                         lp = NULL;
 305         }
 306
 307         /* Pick the LEB with most space */
 308         if (idx_lp && lp) {
 309                 if (idx_lp->free + idx_lp->dirty >= lp->free + lp->dirty)
 310                         lp = idx_lp;
 311         } else if (idx_lp && !lp)
 312                 lp = idx_lp;
 313
 314         if (lp) {
 315                 ubifs_assert(lp->dirty >= c->dead_wm);
 316                 goto found;
 317         }
 318
 319         /* Did not find a dirty LEB on the dirty heaps, have to scan */
 320         dbg_find("scanning LPT for a dirty LEB");
 321         lp = scan_for_dirty(c, min_space, pick_free, exclude_index);
 322         if (IS_ERR(lp)) {
 323                 err = PTR_ERR(lp);
 324                 goto out;
 325         }
 326         ubifs_assert(lp->dirty >= c->dead_wm ||
 327                      (pick_free && lp->free + lp->dirty == c->leb_size));
 328
 329 found:
 330         dbg_find("found LEB %d, free %d, dirty %d, flags %#x",
 331                  lp->lnum, lp->free, lp->dirty, lp->flags);
 332
 333         lp = ubifs_change_lp(c, lp, LPROPS_NC, LPROPS_NC,
 334                              lp->flags | LPROPS_TAKEN, 0);
 335         if (IS_ERR(lp)) {
 336                 err = PTR_ERR(lp);
 337                 goto out;
 338         }
 339
 340         memcpy(ret_lp, lp, sizeof(struct ubifs_lprops));
 341
 342 out:
 343         ubifs_release_lprops(c);
 344         return err;
 345 }
 346
 347 /**
 348  * scan_for_free_cb - free space scan callback.
 349  * @c: the UBIFS file-system description object
 350  * @lprops: LEB properties to scan
 351  * @in_tree: whether the LEB properties are in main memory
 352  * @data: information passed to and from the caller of the scan
 353  *
 354  * This function returns a code that indicates whether the scan should continue
 355  * (%LPT_SCAN_CONTINUE), whether the LEB properties should be added to the tree
 356  * in main memory (%LPT_SCAN_ADD), or whether the scan should stop
 357  * (%LPT_SCAN_STOP).
 358  */
 359 static int scan_for_free_cb(struct ubifs_info *c,
 360                             const struct ubifs_lprops *lprops, int in_tree,
 361                             struct scan_data *data)
 362 {
 363         int ret = LPT_SCAN_CONTINUE;
 364
 365         /* Exclude LEBs that are currently in use */
 366         if (lprops->flags & LPROPS_TAKEN)
 367                 return LPT_SCAN_CONTINUE;
 368         /* Determine whether to add these LEB properties to the tree */
 369         if (!in_tree && valuable(c, lprops))
 370                 ret |= LPT_SCAN_ADD;
 371         /* Exclude index LEBs */
 372         if (lprops->flags & LPROPS_INDEX)
 373                 return ret;
 374         /* Exclude LEBs with too little space */
 375         if (lprops->free < data->min_space)
 376                 return ret;
 377         /* If specified, exclude empty LEBs */
 378         if (!data->pick_free && lprops->free == c->leb_size)
 379                 return ret;
 380         /*
 381          * LEBs that have only free and dirty space must not be allocated
 382          * because they may have been unmapped already or they may have data
 383          * that is obsolete only because of nodes that are still sitting in a
 384          * wbuf.
 385          */
 386         if (lprops->free + lprops->dirty == c->leb_size && lprops->dirty > 0)
 387                 return ret;
 388         /* Finally we found space */
 389         data->lnum = lprops->lnum;
 390         return LPT_SCAN_ADD | LPT_SCAN_STOP;
 391 }
 392
 393 /**
 394  * do_find_free_space - find a data LEB with free space.
 395  * @c: the UBIFS file-system description object
 396  * @min_space: minimum amount of free space required
 397  * @pick_free: whether it is OK to scan for empty LEBs
 398  * @squeeze: whether to try to find space in a non-empty LEB first
 399  *
 400  * This function returns a pointer to the LEB properties found or a negative
 401  * error code.
 402  */
 403 static
 404 const struct ubifs_lprops *do_find_free_space(struct ubifs_info *c,
 405                                               int min_space, int pick_free,
 406                                               int squeeze)
 407 {
 408         const struct ubifs_lprops *lprops;
 409         struct ubifs_lpt_heap *heap;
 410         struct scan_data data;
 411         int err, i;
 412
 413         if (squeeze) {
 414                 lprops = ubifs_fast_find_free(c);
 415                 if (lprops && lprops->free >= min_space)
 416                         return lprops;
 417         }
 418         if (pick_free) {
 419                 lprops = ubifs_fast_find_empty(c);
 420                 if (lprops)
 421                         return lprops;
 422         }
 423         if (!squeeze) {
 424                 lprops = ubifs_fast_find_free(c);
 425                 if (lprops && lprops->free >= min_space)
 426                         return lprops;
 427         }
 428         /* There may be an LEB with enough free space on the dirty heap */
 429         heap = &c->lpt_heap[LPROPS_DIRTY - 1];
 430         for (i = 0; i < heap->cnt; i++) {
 431                 lprops = heap->arr[i];
 432                 if (lprops->free >= min_space)
 433                         return lprops;
 434         }
 435         /*
 436          * A LEB may have fallen off of the bottom of the free heap, and ended
 437          * up as uncategorized even though it has enough free space for us now,
 438          * so check the uncategorized list. N.B. neither empty nor freeable LEBs
 439          * can end up as uncategorized because they are kept on lists not
 440          * finite-sized heaps.
 441          */
 442         list_for_each_entry(lprops, &c->uncat_list, list) {
 443                 if (lprops->flags & LPROPS_TAKEN)
 444                         continue;
 445                 if (lprops->flags & LPROPS_INDEX)
 446                         continue;
 447                 if (lprops->free >= min_space)
 448                         return lprops;
 449         }
 450         /* We have looked everywhere in main memory, now scan the flash */
 451         if (c->pnodes_have >= c->pnode_cnt)
 452                 /* All pnodes are in memory, so skip scan */
 453                 return ERR_PTR(-ENOSPC);
 454         data.min_space = min_space;
 455         data.pick_free = pick_free;
 456         data.lnum = -1;
 457         err = ubifs_lpt_scan_nolock(c, -1, c->lscan_lnum,
 458                                     (ubifs_lpt_scan_callback)scan_for_free_cb,
 459                                     &data);
 460         if (err)
 461                 return ERR_PTR(err);
 462         ubifs_assert(data.lnum >= c->main_first && data.lnum < c->leb_cnt);
 463         c->lscan_lnum = data.lnum;
 464         lprops = ubifs_lpt_lookup_dirty(c, data.lnum);
 465         if (IS_ERR(lprops))
 466                 return lprops;
 467         ubifs_assert(lprops->lnum == data.lnum);
 468         ubifs_assert(lprops->free >= min_space);
 469         ubifs_assert(!(lprops->flags & LPROPS_TAKEN));
 470         ubifs_assert(!(lprops->flags & LPROPS_INDEX));
 471         return lprops;
 472 }
 473
 474 /**
 475  * ubifs_find_free_space - find a data LEB with free space.
 476  * @c: the UBIFS file-system description object
 477  * @min_space: minimum amount of required free space
 478  * @free: contains amount of free space in the LEB on exit
 479  * @squeeze: whether to try to find space in a non-empty LEB first
 480  *
 481  * This function looks for an LEB with at least @min_space bytes of free space.
 482  * It tries to find an empty LEB if possible. If no empty LEBs are available,
 483  * this function searches for a non-empty data LEB. The returned LEB is marked
 484  * as "taken".
 485  *
 486  * This function returns found LEB number in case of success, %-ENOSPC if it
 487  * failed to find a LEB with @min_space bytes of free space and other a negative
 488  * error codes in case of failure.
 489  */
 490 int ubifs_find_free_space(struct ubifs_info *c, int min_space, int *free,
 491                           int squeeze)
 492 {
 493         const struct ubifs_lprops *lprops;
 494         int lebs, rsvd_idx_lebs, pick_free = 0, err, lnum, flags;
 495
 496         dbg_find("min_space %d", min_space);
 497         ubifs_get_lprops(c);
 498
 499         /* Check if there are enough empty LEBs for commit */
 500         spin_lock(&c->space_lock);
 501         if (c->min_idx_lebs > c->lst.idx_lebs)
 502                 rsvd_idx_lebs = c->min_idx_lebs -  c->lst.idx_lebs;
 503         else
 504                 rsvd_idx_lebs = 0;
 505         lebs = c->lst.empty_lebs + c->freeable_cnt + c->idx_gc_cnt -
 506                c->lst.taken_empty_lebs;
 507         ubifs_assert(lebs + c->lst.idx_lebs >= c->min_idx_lebs);
 508         if (rsvd_idx_lebs < lebs)
 509                 /*
 510                  * OK to allocate an empty LEB, but we still don't want to go
 511                  * looking for one if there aren't any.
 512                  */
 513                 if (c->lst.empty_lebs - c->lst.taken_empty_lebs > 0) {
 514                         pick_free = 1;
 515                         /*
 516                          * Because we release the space lock, we must account
 517                          * for this allocation here. After the LEB properties
 518                          * flags have been updated, we subtract one. Note, the
 519                          * result of this is that lprops also decreases
 520                          * @taken_empty_lebs in 'ubifs_change_lp()', so it is
 521                          * off by one for a short period of time which may
 522                          * introduce a small disturbance to budgeting
 523                          * calculations, but this is harmless because at the
 524                          * worst case this would make the budgeting subsystem
 525                          * be more pessimistic than needed.
 526                          *
 527                          * Fundamentally, this is about serialization of the
 528                          * budgeting and lprops subsystems. We could make the
 529                          * @space_lock a mutex and avoid dropping it before
 530                          * calling 'ubifs_change_lp()', but mutex is more
 531                          * heavy-weight, and we want budgeting to be as fast as
 532                          * possible.
 533                          */
 534                         c->lst.taken_empty_lebs += 1;
 535                 }
 536         spin_unlock(&c->space_lock);
 537
 538         lprops = do_find_free_space(c, min_space, pick_free, squeeze);
 539         if (IS_ERR(lprops)) {
 540                 err = PTR_ERR(lprops);
 541                 goto out;
 542         }
 543
 544         lnum = lprops->lnum;
 545         flags = lprops->flags | LPROPS_TAKEN;
 546
 547         lprops = ubifs_change_lp(c, lprops, LPROPS_NC, LPROPS_NC, flags, 0);
 548         if (IS_ERR(lprops)) {
 549                 err = PTR_ERR(lprops);
 550                 goto out;
 551         }
 552
 553         if (pick_free) {
 554                 spin_lock(&c->space_lock);
 555                 c->lst.taken_empty_lebs -= 1;
 556                 spin_unlock(&c->space_lock);
 557         }
 558
 559         *free = lprops->free;
 560         ubifs_release_lprops(c);
 561
 562         if (*free == c->leb_size) {
 563                 /*
 564                  * Ensure that empty LEBs have been unmapped. They may not have
 565                  * been, for example, because of an unclean unmount.  Also
 566                  * LEBs that were freeable LEBs (free + dirty == leb_size) will
 567                  * not have been unmapped.
 568                  */
 569                 err = ubifs_leb_unmap(c, lnum);
 570                 if (err)
 571                         return err;
 572         }
 573
 574         dbg_find("found LEB %d, free %d", lnum, *free);
 575         ubifs_assert(*free >= min_space);
 576         return lnum;
 577
 578 out:
 579         if (pick_free) {
 580                 spin_lock(&c->space_lock);
 581                 c->lst.taken_empty_lebs -= 1;
 582                 spin_unlock(&c->space_lock);
 583         }
 584         ubifs_release_lprops(c);
 585         return err;
 586 }
 587
 588 /**
 589  * scan_for_idx_cb - callback used by the scan for a free LEB for the index.
 590  * @c: the UBIFS file-system description object
 591  * @lprops: LEB properties to scan
 592  * @in_tree: whether the LEB properties are in main memory
 593  * @data: information passed to and from the caller of the scan
 594  *
 595  * This function returns a code that indicates whether the scan should continue
 596  * (%LPT_SCAN_CONTINUE), whether the LEB properties should be added to the tree
 597  * in main memory (%LPT_SCAN_ADD), or whether the scan should stop
 598  * (%LPT_SCAN_STOP).
 599  */
 600 static int scan_for_idx_cb(struct ubifs_info *c,
 601                            const struct ubifs_lprops *lprops, int in_tree,
 602                            struct scan_data *data)
 603 {
 604         int ret = LPT_SCAN_CONTINUE;
 605
 606         /* Exclude LEBs that are currently in use */
 607         if (lprops->flags & LPROPS_TAKEN)
 608                 return LPT_SCAN_CONTINUE;
 609         /* Determine whether to add these LEB properties to the tree */
 610         if (!in_tree && valuable(c, lprops))
 611                 ret |= LPT_SCAN_ADD;
 612         /* Exclude index LEBS */
 613         if (lprops->flags & LPROPS_INDEX)
 614                 return ret;
 615         /* Exclude LEBs that cannot be made empty */
 616         if (lprops->free + lprops->dirty != c->leb_size)
 617                 return ret;
 618         /*
 619          * We are allocating for the index so it is safe to allocate LEBs with
 620          * only free and dirty space, because write buffers are sync'd at commit
 621          * start.
 622          */
 623         data->lnum = lprops->lnum;
 624         return LPT_SCAN_ADD | LPT_SCAN_STOP;
 625 }
 626
 627 /**
 628  * scan_for_leb_for_idx - scan for a free LEB for the index.
 629  * @c: the UBIFS file-system description object
 630  */
 631 static const struct ubifs_lprops *scan_for_leb_for_idx(struct ubifs_info *c)
 632 {
 633         struct ubifs_lprops *lprops;
 634         struct scan_data data;
 635         int err;
 636
 637         data.lnum = -1;
 638         err = ubifs_lpt_scan_nolock(c, -1, c->lscan_lnum,
 639                                     (ubifs_lpt_scan_callback)scan_for_idx_cb,
 640                                     &data);
 641         if (err)
 642                 return ERR_PTR(err);
 643         ubifs_assert(data.lnum >= c->main_first && data.lnum < c->leb_cnt);
 644         c->lscan_lnum = data.lnum;
 645         lprops = ubifs_lpt_lookup_dirty(c, data.lnum);
 646         if (IS_ERR(lprops))
 647                 return lprops;
 648         ubifs_assert(lprops->lnum == data.lnum);
 649         ubifs_assert(lprops->free + lprops->dirty == c->leb_size);
 650         ubifs_assert(!(lprops->flags & LPROPS_TAKEN));
 651         ubifs_assert(!(lprops->flags & LPROPS_INDEX));
 652         return lprops;
 653 }
 654
 655 /**
 656  * ubifs_find_free_leb_for_idx - find a free LEB for the index.
 657  * @c: the UBIFS file-system description object
 658  *
 659  * This function looks for a free LEB and returns that LEB number. The returned
 660  * LEB is marked as "taken", "index".
 661  *
 662  * Only empty LEBs are allocated. This is for two reasons. First, the commit
 663  * calculates the number of LEBs to allocate based on the assumption that they
 664  * will be empty. Secondly, free space at the end of an index LEB is not
 665  * guaranteed to be empty because it may have been used by the in-the-gaps
 666  * method prior to an unclean unmount.
 667  *
 668  * If no LEB is found %-ENOSPC is returned. For other failures another negative
 669  * error code is returned.
 670  */
 671 int ubifs_find_free_leb_for_idx(struct ubifs_info *c)
 672 {
 673         const struct ubifs_lprops *lprops;
 674         int lnum = -1, err, flags;
 675
 676         ubifs_get_lprops(c);
 677
 678         lprops = ubifs_fast_find_empty(c);
 679         if (!lprops) {
 680                 lprops = ubifs_fast_find_freeable(c);
 681                 if (!lprops) {
 682                         ubifs_assert(c->freeable_cnt == 0);
 683                         if (c->lst.empty_lebs - c->lst.taken_empty_lebs > 0) {
 684                                 lprops = scan_for_leb_for_idx(c);
 685                                 if (IS_ERR(lprops)) {
 686                                         err = PTR_ERR(lprops);
 687                                         goto out;
 688                                 }
 689                         }
 690                 }
 691         }
 692
 693         if (!lprops) {
 694                 err = -ENOSPC;
 695                 goto out;
 696         }
 697
 698         lnum = lprops->lnum;
 699
 700         dbg_find("found LEB %d, free %d, dirty %d, flags %#x",
 701                  lnum, lprops->free, lprops->dirty, lprops->flags);
 702
 703         flags = lprops->flags | LPROPS_TAKEN | LPROPS_INDEX;
 704         lprops = ubifs_change_lp(c, lprops, c->leb_size, 0, flags, 0);
 705         if (IS_ERR(lprops)) {
 706                 err = PTR_ERR(lprops);
 707                 goto out;
 708         }
 709
 710         ubifs_release_lprops(c);
 711
 712         /*
 713          * Ensure that empty LEBs have been unmapped. They may not have been,
 714          * for example, because of an unclean unmount. Also LEBs that were
 715          * freeable LEBs (free + dirty == leb_size) will not have been unmapped.
 716          */
 717         err = ubifs_leb_unmap(c, lnum);
 718         if (err) {
 719                 ubifs_change_one_lp(c, lnum, LPROPS_NC, LPROPS_NC, 0,
 720                                     LPROPS_TAKEN | LPROPS_INDEX, 0);
 721                 return err;
 722         }
 723
 724         return lnum;
 725
 726 out:
 727         ubifs_release_lprops(c);
 728         return err;
 729 }
 730
 731 static int cmp_dirty_idx(const struct ubifs_lprops **a,
 732                          const struct ubifs_lprops **b)
 733 {
 734         const struct ubifs_lprops *lpa = *a;
 735         const struct ubifs_lprops *lpb = *b;
 736
 737         return lpa->dirty + lpa->free - lpb->dirty - lpb->free;
 738 }
 739
 740 static void swap_dirty_idx(struct ubifs_lprops **a, struct ubifs_lprops **b,
 741                            int size)
 742 {
 743         struct ubifs_lprops *t = *a;
 744
 745         *a = *b;
 746         *b = t;
 747 }
 748
 749 /**
 750  * ubifs_save_dirty_idx_lnums - save an array of the most dirty index LEB nos.
 751  * @c: the UBIFS file-system description object
 752  *
 753  * This function is called each commit to create an array of LEB numbers of
 754  * dirty index LEBs sorted in order of dirty and free space.  This is used by
 755  * the in-the-gaps method of TNC commit.
 756  */
 757 int ubifs_save_dirty_idx_lnums(struct ubifs_info *c)
 758 {
 759         int i;
 760
 761         ubifs_get_lprops(c);
 762         /* Copy the LPROPS_DIRTY_IDX heap */
 763         c->dirty_idx.cnt = c->lpt_heap[LPROPS_DIRTY_IDX - 1].cnt;
 764         memcpy(c->dirty_idx.arr, c->lpt_heap[LPROPS_DIRTY_IDX - 1].arr,
 765                sizeof(void *) * c->dirty_idx.cnt);
 766         /* Sort it so that the dirtiest is now at the end */
 767         sort(c->dirty_idx.arr, c->dirty_idx.cnt, sizeof(void *),
 768              (int (*)(const void *, const void *))cmp_dirty_idx,
 769              (void (*)(void *, void *, int))swap_dirty_idx);
 770         dbg_find("found %d dirty index LEBs", c->dirty_idx.cnt);
 771         if (c->dirty_idx.cnt)
 772                 dbg_find("dirtiest index LEB is %d with dirty %d and free %d",
 773                          c->dirty_idx.arr[c->dirty_idx.cnt - 1]->lnum,
 774                          c->dirty_idx.arr[c->dirty_idx.cnt - 1]->dirty,
 775                          c->dirty_idx.arr[c->dirty_idx.cnt - 1]->free);
 776         /* Replace the lprops pointers with LEB numbers */
 777         for (i = 0; i < c->dirty_idx.cnt; i++)
 778                 c->dirty_idx.arr[i] = (void *)(size_t)c->dirty_idx.arr[i]->lnum;
 779         ubifs_release_lprops(c);
 780         return 0;
 781 }
 782
 783 /**
 784  * scan_dirty_idx_cb - callback used by the scan for a dirty index LEB.
 785  * @c: the UBIFS file-system description object
 786  * @lprops: LEB properties to scan
 787  * @in_tree: whether the LEB properties are in main memory
 788  * @data: information passed to and from the caller of the scan
 789  *
 790  * This function returns a code that indicates whether the scan should continue
 791  * (%LPT_SCAN_CONTINUE), whether the LEB properties should be added to the tree
 792  * in main memory (%LPT_SCAN_ADD), or whether the scan should stop
 793  * (%LPT_SCAN_STOP).
 794  */
 795 static int scan_dirty_idx_cb(struct ubifs_info *c,
 796                            const struct ubifs_lprops *lprops, int in_tree,
 797                            struct scan_data *data)
 798 {
 799         int ret = LPT_SCAN_CONTINUE;
 800
 801         /* Exclude LEBs that are currently in use */
 802         if (lprops->flags & LPROPS_TAKEN)
 803                 return LPT_SCAN_CONTINUE;
 804         /* Determine whether to add these LEB properties to the tree */
 805         if (!in_tree && valuable(c, lprops))
 806                 ret |= LPT_SCAN_ADD;
 807         /* Exclude non-index LEBs */
 808         if (!(lprops->flags & LPROPS_INDEX))
 809                 return ret;
 810         /* Exclude LEBs with too little space */
 811         if (lprops->free + lprops->dirty < c->min_idx_node_sz)
 812                 return ret;
 813         /* Finally we found space */
 814         data->lnum = lprops->lnum;
 815         return LPT_SCAN_ADD | LPT_SCAN_STOP;
 816 }
 817
 818 /**
 819  * find_dirty_idx_leb - find a dirty index LEB.
 820  * @c: the UBIFS file-system description object
 821  *
 822  * This function returns LEB number upon success and a negative error code upon
 823  * failure.  In particular, -ENOSPC is returned if a dirty index LEB is not
 824  * found.
 825  *
 826  * Note that this function scans the entire LPT but it is called very rarely.
 827  */
 828 static int find_dirty_idx_leb(struct ubifs_info *c)
 829 {
 830         const struct ubifs_lprops *lprops;
 831         struct ubifs_lpt_heap *heap;
 832         struct scan_data data;
 833         int err, i, ret;
 834
 835         /* Check all structures in memory first */
 836         data.lnum = -1;
 837         heap = &c->lpt_heap[LPROPS_DIRTY_IDX - 1];
 838         for (i = 0; i < heap->cnt; i++) {
 839                 lprops = heap->arr[i];
 840                 ret = scan_dirty_idx_cb(c, lprops, 1, &data);
 841                 if (ret & LPT_SCAN_STOP)
 842                         goto found;
 843         }
 844         list_for_each_entry(lprops, &c->frdi_idx_list, list) {
 845                 ret = scan_dirty_idx_cb(c, lprops, 1, &data);
 846                 if (ret & LPT_SCAN_STOP)
 847                         goto found;
 848         }
 849         list_for_each_entry(lprops, &c->uncat_list, list) {
 850                 ret = scan_dirty_idx_cb(c, lprops, 1, &data);
 851                 if (ret & LPT_SCAN_STOP)
 852                         goto found;
 853         }
 854         if (c->pnodes_have >= c->pnode_cnt)
 855                 /* All pnodes are in memory, so skip scan */
 856                 return -ENOSPC;
 857         err = ubifs_lpt_scan_nolock(c, -1, c->lscan_lnum,
 858                                     (ubifs_lpt_scan_callback)scan_dirty_idx_cb,
 859                                     &data);
 860         if (err)
 861                 return err;
 862 found:
 863         ubifs_assert(data.lnum >= c->main_first && data.lnum < c->leb_cnt);
 864         c->lscan_lnum = data.lnum;
 865         lprops = ubifs_lpt_lookup_dirty(c, data.lnum);
 866         if (IS_ERR(lprops))
 867                 return PTR_ERR(lprops);
 868         ubifs_assert(lprops->lnum == data.lnum);
 869         ubifs_assert(lprops->free + lprops->dirty >= c->min_idx_node_sz);
 870         ubifs_assert(!(lprops->flags & LPROPS_TAKEN));
 871         ubifs_assert((lprops->flags & LPROPS_INDEX));
 872
 873         dbg_find("found dirty LEB %d, free %d, dirty %d, flags %#x",
 874                  lprops->lnum, lprops->free, lprops->dirty, lprops->flags);
 875
 876         lprops = ubifs_change_lp(c, lprops, LPROPS_NC, LPROPS_NC,
 877                                  lprops->flags | LPROPS_TAKEN, 0);
 878         if (IS_ERR(lprops))
 879                 return PTR_ERR(lprops);
 880
 881         return lprops->lnum;
 882 }
 883
 884 /**
 885  * get_idx_gc_leb - try to get a LEB number from trivial GC.
 886  * @c: the UBIFS file-system description object
 887  */
 888 static int get_idx_gc_leb(struct ubifs_info *c)
 889 {
 890         const struct ubifs_lprops *lp;
 891         int err, lnum;
 892
 893         err = ubifs_get_idx_gc_leb(c);
 894         if (err < 0)
 895                 return err;
 896         lnum = err;
 897         /*
 898          * The LEB was due to be unmapped after the commit but
 899          * it is needed now for this commit.
 900          */
 901         lp = ubifs_lpt_lookup_dirty(c, lnum);
 902         if (unlikely(IS_ERR(lp)))
 903                 return PTR_ERR(lp);
 904         lp = ubifs_change_lp(c, lp, LPROPS_NC, LPROPS_NC,
 905                              lp->flags | LPROPS_INDEX, -1);
 906         if (unlikely(IS_ERR(lp)))
 907                 return PTR_ERR(lp);
 908         dbg_find("LEB %d, dirty %d and free %d flags %#x",
 909                  lp->lnum, lp->dirty, lp->free, lp->flags);
 910         return lnum;
 911 }
 912
 913 /**
 914  * find_dirtiest_idx_leb - find dirtiest index LEB from dirtiest array.
 915  * @c: the UBIFS file-system description object
 916  */
 917 static int find_dirtiest_idx_leb(struct ubifs_info *c)
 918 {
 919         const struct ubifs_lprops *lp;
 920         int lnum;
 921
 922         while (1) {
 923                 if (!c->dirty_idx.cnt)
 924                         return -ENOSPC;
 925                 /* The lprops pointers were replaced by LEB numbers */
 926                 lnum = (size_t)c->dirty_idx.arr[--c->dirty_idx.cnt];
 927                 lp = ubifs_lpt_lookup(c, lnum);
 928                 if (IS_ERR(lp))
 929                         return PTR_ERR(lp);
 930                 if ((lp->flags & LPROPS_TAKEN) || !(lp->flags & LPROPS_INDEX))
 931                         continue;
 932                 lp = ubifs_change_lp(c, lp, LPROPS_NC, LPROPS_NC,
 933                                      lp->flags | LPROPS_TAKEN, 0);
 934                 if (IS_ERR(lp))
 935                         return PTR_ERR(lp);
 936                 break;
 937         }
 938         dbg_find("LEB %d, dirty %d and free %d flags %#x", lp->lnum, lp->dirty,
 939                  lp->free, lp->flags);
 940         ubifs_assert(lp->flags | LPROPS_TAKEN);
 941         ubifs_assert(lp->flags | LPROPS_INDEX);
 942         return lnum;
 943 }
 944
 945 /**
 946  * ubifs_find_dirty_idx_leb - try to find dirtiest index LEB as at last commit.
 947  * @c: the UBIFS file-system description object
 948  *
 949  * This function attempts to find an untaken index LEB with the most free and
 950  * dirty space that can be used without overwriting index nodes that were in the
 951  * last index committed.
 952  */
 953 int ubifs_find_dirty_idx_leb(struct ubifs_info *c)
 954 {
 955         int err;
 956
 957         ubifs_get_lprops(c);
 958
 959         /*
 960          * We made an array of the dirtiest index LEB numbers as at the start of
 961          * last commit.  Try that array first.
 962          */
 963         err = find_dirtiest_idx_leb(c);
 964
 965         /* Next try scanning the entire LPT */
 966         if (err == -ENOSPC)
 967                 err = find_dirty_idx_leb(c);
 968
 969         /* Finally take any index LEBs awaiting trivial GC */
 970         if (err == -ENOSPC)
 971                 err = get_idx_gc_leb(c);
 972
 973         ubifs_release_lprops(c);
 974         return err;
 975 }