fs/ubifs/gc.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: Adrian Hunter
  20  *          Artem Bityutskiy (Битюцкий Артём)
  21  */
  22
  23 /*
  24  * This file implements garbage collection. The procedure for garbage collection
  25  * is different depending on whether a LEB as an index LEB (contains index
  26  * nodes) or not. For non-index LEBs, garbage collection finds a LEB which
  27  * contains a lot of dirty space (obsolete nodes), and copies the non-obsolete
  28  * nodes to the journal, at which point the garbage-collected LEB is free to be
  29  * reused. For index LEBs, garbage collection marks the non-obsolete index nodes
  30  * dirty in the TNC, and after the next commit, the garbage-collected LEB is
  31  * to be reused. Garbage collection will cause the number of dirty index nodes
  32  * to grow, however sufficient space is reserved for the index to ensure the
  33  * commit will never run out of space.
  34  */
  35
  36 #include <linux/pagemap.h>
  37 #include "ubifs.h"
  38
  39 /*
  40  * GC tries to optimize the way it fit nodes to available space, and it sorts
  41  * nodes a little. The below constants are watermarks which define "large",
  42  * "medium", and "small" nodes.
  43  */
  44 #define MEDIUM_NODE_WM (UBIFS_BLOCK_SIZE / 4)
  45 #define SMALL_NODE_WM  UBIFS_MAX_DENT_NODE_SZ
  46
  47 /*
  48  * GC may need to move more then one LEB to make progress. The below constants
  49  * define "soft" and "hard" limits on the number of LEBs the garbage collector
  50  * may move.
  51  */
  52 #define SOFT_LEBS_LIMIT 4
  53 #define HARD_LEBS_LIMIT 32
  54
  55 /**
  56  * switch_gc_head - switch the garbage collection journal head.
  57  * @c: UBIFS file-system description object
  58  * @buf: buffer to write
  59  * @len: length of the buffer to write
  60  * @lnum: LEB number written is returned here
  61  * @offs: offset written is returned here
  62  *
  63  * This function switch the GC head to the next LEB which is reserved in
  64  * @c->gc_lnum. Returns %0 in case of success, %-EAGAIN if commit is required,
  65  * and other negative error code in case of failures.
  66  */
  67 static int switch_gc_head(struct ubifs_info *c)
  68 {
  69         int err, gc_lnum = c->gc_lnum;
  70         struct ubifs_wbuf *wbuf = &c->jheads[GCHD].wbuf;
  71
  72         ubifs_assert(gc_lnum != -1);
  73         dbg_gc("switch GC head from LEB %d:%d to LEB %d (waste %d bytes)",
  74                wbuf->lnum, wbuf->offs + wbuf->used, gc_lnum,
  75                c->leb_size - wbuf->offs - wbuf->used);
  76
  77         err = ubifs_wbuf_sync_nolock(wbuf);
  78         if (err)
  79                 return err;
  80
  81         /*
  82          * The GC write-buffer was synchronized, we may safely unmap
  83          * 'c->gc_lnum'.
  84          */
  85         err = ubifs_leb_unmap(c, gc_lnum);
  86         if (err)
  87                 return err;
  88
  89         err = ubifs_add_bud_to_log(c, GCHD, gc_lnum, 0);
  90         if (err)
  91                 return err;
  92
  93         c->gc_lnum = -1;
  94         err = ubifs_wbuf_seek_nolock(wbuf, gc_lnum, 0, UBI_LONGTERM);
  95         return err;
  96 }
  97
  98 /**
  99  * move_nodes - move nodes.
 100  * @c: UBIFS file-system description object
 101  * @sleb: describes nodes to move
 102  *
 103  * This function moves valid nodes from data LEB described by @sleb to the GC
 104  * journal head. The obsolete nodes are dropped.
 105  *
 106  * When moving nodes we have to deal with classical bin-packing problem: the
 107  * space in the current GC journal head LEB and in @c->gc_lnum are the "bins",
 108  * where the nodes in the @sleb->nodes list are the elements which should be
 109  * fit optimally to the bins. This function uses the "first fit decreasing"
 110  * strategy, although it does not really sort the nodes but just split them on
 111  * 3 classes - large, medium, and small, so they are roughly sorted.
 112  *
 113  * This function returns zero in case of success, %-EAGAIN if commit is
 114  * required, and other negative error codes in case of other failures.
 115  */
 116 static int move_nodes(struct ubifs_info *c, struct ubifs_scan_leb *sleb)
 117 {
 118         struct ubifs_scan_node *snod, *tmp;
 119         struct list_head large, medium, small;
 120         struct ubifs_wbuf *wbuf = &c->jheads[GCHD].wbuf;
 121         int avail, err, min = INT_MAX;
 122
 123         INIT_LIST_HEAD(&large);
 124         INIT_LIST_HEAD(&medium);
 125         INIT_LIST_HEAD(&small);
 126
 127         list_for_each_entry_safe(snod, tmp, &sleb->nodes, list) {
 128                 struct list_head *lst;
 129
 130                 ubifs_assert(snod->type != UBIFS_IDX_NODE);
 131                 ubifs_assert(snod->type != UBIFS_REF_NODE);
 132                 ubifs_assert(snod->type != UBIFS_CS_NODE);
 133
 134                 err = ubifs_tnc_has_node(c, &snod->key, 0, sleb->lnum,
 135                                          snod->offs, 0);
 136                 if (err < 0)
 137                         goto out;
 138
 139                 lst = &snod->list;
 140                 list_del(lst);
 141                 if (!err) {
 142                         /* The node is obsolete, remove it from the list */
 143                         kfree(snod);
 144                         continue;
 145                 }
 146
 147                 /*
 148                  * Sort the list of nodes so that large nodes go first, and
 149                  * small nodes go last.
 150                  */
 151                 if (snod->len > MEDIUM_NODE_WM)
 152                         list_add(lst, &large);
 153                 else if (snod->len > SMALL_NODE_WM)
 154                         list_add(lst, &medium);
 155                 else
 156                         list_add(lst, &small);
 157
 158                 /* And find the smallest node */
 159                 if (snod->len < min)
 160                         min = snod->len;
 161         }
 162
 163         /*
 164          * Join the tree lists so that we'd have one roughly sorted list
 165          * ('large' will be the head of the joined list).
 166          */
 167         list_splice(&medium, large.prev);
 168         list_splice(&small, large.prev);
 169
 170         if (wbuf->lnum == -1) {
 171                 /*
 172                  * The GC journal head is not set, because it is the first GC
 173                  * invocation since mount.
 174                  */
 175                 err = switch_gc_head(c);
 176                 if (err)
 177                         goto out;
 178         }
 179
 180         /* Write nodes to their new location. Use the first-fit strategy */
 181         while (1) {
 182                 avail = c->leb_size - wbuf->offs - wbuf->used;
 183                 list_for_each_entry_safe(snod, tmp, &large, list) {
 184                         int new_lnum, new_offs;
 185
 186                         if (avail < min)
 187                                 break;
 188
 189                         if (snod->len > avail)
 190                                 /* This node does not fit */
 191                                 continue;
 192
 193                         cond_resched();
 194
 195                         new_lnum = wbuf->lnum;
 196                         new_offs = wbuf->offs + wbuf->used;
 197                         err = ubifs_wbuf_write_nolock(wbuf, snod->node,
 198                                                       snod->len);
 199                         if (err)
 200                                 goto out;
 201                         err = ubifs_tnc_replace(c, &snod->key, sleb->lnum,
 202                                                 snod->offs, new_lnum, new_offs,
 203                                                 snod->len);
 204                         if (err)
 205                                 goto out;
 206
 207                         avail = c->leb_size - wbuf->offs - wbuf->used;
 208                         list_del(&snod->list);
 209                         kfree(snod);
 210                 }
 211
 212                 if (list_empty(&large))
 213                         break;
 214
 215                 /*
 216                  * Waste the rest of the space in the LEB and switch to the
 217                  * next LEB.
 218                  */
 219                 err = switch_gc_head(c);
 220                 if (err)
 221                         goto out;
 222         }
 223
 224         return 0;
 225
 226 out:
 227         list_for_each_entry_safe(snod, tmp, &large, list) {
 228                 list_del(&snod->list);
 229                 kfree(snod);
 230         }
 231         return err;
 232 }
 233
 234 /**
 235  * gc_sync_wbufs - sync write-buffers for GC.
 236  * @c: UBIFS file-system description object
 237  *
 238  * We must guarantee that obsoleting nodes are on flash. Unfortunately they may
 239  * be in a write-buffer instead. That is, a node could be written to a
 240  * write-buffer, obsoleting another node in a LEB that is GC'd. If that LEB is
 241  * erased before the write-buffer is sync'd and then there is an unclean
 242  * unmount, then an existing node is lost. To avoid this, we sync all
 243  * write-buffers.
 244  *
 245  * This function returns %0 on success or a negative error code on failure.
 246  */
 247 static int gc_sync_wbufs(struct ubifs_info *c)
 248 {
 249         int err, i;
 250
 251         for (i = 0; i < c->jhead_cnt; i++) {
 252                 if (i == GCHD)
 253                         continue;
 254                 err = ubifs_wbuf_sync(&c->jheads[i].wbuf);
 255                 if (err)
 256                         return err;
 257         }
 258         return 0;
 259 }
 260
 261 /**
 262  * ubifs_garbage_collect_leb - garbage-collect a logical eraseblock.
 263  * @c: UBIFS file-system description object
 264  * @lp: describes the LEB to garbage collect
 265  *
 266  * This function garbage-collects an LEB and returns one of the @LEB_FREED,
 267  * @LEB_RETAINED, etc positive codes in case of success, %-EAGAIN if commit is
 268  * required, and other negative error codes in case of failures.
 269  */
 270 int ubifs_garbage_collect_leb(struct ubifs_info *c, struct ubifs_lprops *lp)
 271 {
 272         struct ubifs_scan_leb *sleb;
 273         struct ubifs_scan_node *snod;
 274         struct ubifs_wbuf *wbuf = &c->jheads[GCHD].wbuf;
 275         int err = 0, lnum = lp->lnum;
 276
 277         ubifs_assert(c->gc_lnum != -1 || wbuf->offs + wbuf->used == 0 ||
 278                      c->need_recovery);
 279         ubifs_assert(c->gc_lnum != lnum);
 280         ubifs_assert(wbuf->lnum != lnum);
 281
 282         /*
 283          * We scan the entire LEB even though we only really need to scan up to
 284          * (c->leb_size - lp->free).
 285          */
 286         sleb = ubifs_scan(c, lnum, 0, c->sbuf);
 287         if (IS_ERR(sleb))
 288                 return PTR_ERR(sleb);
 289
 290         ubifs_assert(!list_empty(&sleb->nodes));
 291         snod = list_entry(sleb->nodes.next, struct ubifs_scan_node, list);
 292
 293         if (snod->type == UBIFS_IDX_NODE) {
 294                 struct ubifs_gced_idx_leb *idx_gc;
 295
 296                 dbg_gc("indexing LEB %d (free %d, dirty %d)",
 297                        lnum, lp->free, lp->dirty);
 298                 list_for_each_entry(snod, &sleb->nodes, list) {
 299                         struct ubifs_idx_node *idx = snod->node;
 300                         int level = le16_to_cpu(idx->level);
 301
 302                         ubifs_assert(snod->type == UBIFS_IDX_NODE);
 303                         key_read(c, ubifs_idx_key(c, idx), &snod->key);
 304                         err = ubifs_dirty_idx_node(c, &snod->key, level, lnum,
 305                                                    snod->offs);
 306                         if (err)
 307                                 goto out;
 308                 }
 309
 310                 idx_gc = kmalloc(sizeof(struct ubifs_gced_idx_leb), GFP_NOFS);
 311                 if (!idx_gc) {
 312                         err = -ENOMEM;
 313                         goto out;
 314                 }
 315
 316                 idx_gc->lnum = lnum;
 317                 idx_gc->unmap = 0;
 318                 list_add(&idx_gc->list, &c->idx_gc);
 319
 320                 /*
 321                  * Don't release the LEB until after the next commit, because
 322                  * it may contain date which is needed for recovery. So
 323                  * although we freed this LEB, it will become usable only after
 324                  * the commit.
 325                  */
 326                 err = ubifs_change_one_lp(c, lnum, c->leb_size, 0, 0,
 327                                           LPROPS_INDEX, 1);
 328                 if (err)
 329                         goto out;
 330                 err = LEB_FREED_IDX;
 331         } else {
 332                 dbg_gc("data LEB %d (free %d, dirty %d)",
 333                        lnum, lp->free, lp->dirty);
 334
 335                 err = move_nodes(c, sleb);
 336                 if (err)
 337                         goto out;
 338
 339                 err = gc_sync_wbufs(c);
 340                 if (err)
 341                         goto out;
 342
 343                 err = ubifs_change_one_lp(c, lnum, c->leb_size, 0, 0, 0, 0);
 344                 if (err)
 345                         goto out;
 346
 347                 if (c->gc_lnum == -1) {
 348                         c->gc_lnum = lnum;
 349                         err = LEB_RETAINED;
 350                 } else {
 351                         err = ubifs_wbuf_sync_nolock(wbuf);
 352                         if (err)
 353                                 goto out;
 354
 355                         err = ubifs_leb_unmap(c, lnum);
 356                         if (err)
 357                                 goto out;
 358
 359                         err = LEB_FREED;
 360                 }
 361         }
 362
 363 out:
 364         ubifs_scan_destroy(sleb);
 365         return err;
 366 }
 367
 368 /**
 369  * ubifs_garbage_collect - UBIFS garbage collector.
 370  * @c: UBIFS file-system description object
 371  * @anyway: do GC even if there are free LEBs
 372  *
 373  * This function does out-of-place garbage collection. The return codes are:
 374  *   o positive LEB number if the LEB has been freed and may be used;
 375  *   o %-EAGAIN if the caller has to run commit;
 376  *   o %-ENOSPC if GC failed to make any progress;
 377  *   o other negative error codes in case of other errors.
 378  *
 379  * Garbage collector writes data to the journal when GC'ing data LEBs, and just
 380  * marking indexing nodes dirty when GC'ing indexing LEBs. Thus, at some point
 381  * commit may be required. But commit cannot be run from inside GC, because the
 382  * caller might be holding the commit lock, so %-EAGAIN is returned instead;
 383  * And this error code means that the caller has to run commit, and re-run GC
 384  * if there is still no free space.
 385  *
 386  * There are many reasons why this function may return %-EAGAIN:
 387  * o the log is full and there is no space to write an LEB reference for
 388  *   @c->gc_lnum;
 389  * o the journal is too large and exceeds size limitations;
 390  * o GC moved indexing LEBs, but they can be used only after the commit;
 391  * o the shrinker fails to find clean znodes to free and requests the commit;
 392  * o etc.
 393  *
 394  * Note, if the file-system is close to be full, this function may return
 395  * %-EAGAIN infinitely, so the caller has to limit amount of re-invocations of
 396  * the function. E.g., this happens if the limits on the journal size are too
 397  * tough and GC writes too much to the journal before an LEB is freed. This
 398  * might also mean that the journal is too large, and the TNC becomes to big,
 399  * so that the shrinker is constantly called, finds not clean znodes to free,
 400  * and requests commit. Well, this may also happen if the journal is all right,
 401  * but another kernel process consumes too much memory. Anyway, infinite
 402  * %-EAGAIN may happen, but in some extreme/misconfiguration cases.
 403  */
 404 int ubifs_garbage_collect(struct ubifs_info *c, int anyway)
 405 {
 406         int i, err, ret, min_space = c->dead_wm;
 407         struct ubifs_lprops lp;
 408         struct ubifs_wbuf *wbuf = &c->jheads[GCHD].wbuf;
 409
 410         ubifs_assert_cmt_locked(c);
 411
 412         if (ubifs_gc_should_commit(c))
 413                 return -EAGAIN;
 414
 415         mutex_lock_nested(&wbuf->io_mutex, wbuf->jhead);
 416
 417         if (c->ro_media) {
 418                 ret = -EROFS;
 419                 goto out_unlock;
 420         }
 421
 422         /* We expect the write-buffer to be empty on entry */
 423         ubifs_assert(!wbuf->used);
 424
 425         for (i = 0; ; i++) {
 426                 int space_before = c->leb_size - wbuf->offs - wbuf->used;
 427                 int space_after;
 428
 429                 cond_resched();
 430
 431                 /* Give the commit an opportunity to run */
 432                 if (ubifs_gc_should_commit(c)) {
 433                         ret = -EAGAIN;
 434                         break;
 435                 }
 436
 437                 if (i > SOFT_LEBS_LIMIT && !list_empty(&c->idx_gc)) {
 438                         /*
 439                          * We've done enough iterations. Indexing LEBs were
 440                          * moved and will be available after the commit.
 441                          */
 442                         dbg_gc("soft limit, some index LEBs GC'ed, -EAGAIN");
 443                         ubifs_commit_required(c);
 444                         ret = -EAGAIN;
 445                         break;
 446                 }
 447
 448                 if (i > HARD_LEBS_LIMIT) {
 449                         /*
 450                          * We've moved too many LEBs and have not made
 451                          * progress, give up.
 452                          */
 453                         dbg_gc("hard limit, -ENOSPC");
 454                         ret = -ENOSPC;
 455                         break;
 456                 }
 457
 458                 /*
 459                  * Empty and freeable LEBs can turn up while we waited for
 460                  * the wbuf lock, or while we have been running GC. In that
 461                  * case, we should just return one of those instead of
 462                  * continuing to GC dirty LEBs. Hence we request
 463                  * 'ubifs_find_dirty_leb()' to return an empty LEB if it can.
 464                  */
 465                 ret = ubifs_find_dirty_leb(c, &lp, min_space, anyway ? 0 : 1);
 466                 if (ret) {
 467                         if (ret == -ENOSPC)
 468                                 dbg_gc("no more dirty LEBs");
 469                         break;
 470                 }
 471
 472                 dbg_gc("found LEB %d: free %d, dirty %d, sum %d "
 473                        "(min. space %d)", lp.lnum, lp.free, lp.dirty,
 474                        lp.free + lp.dirty, min_space);
 475
 476                 if (lp.free + lp.dirty == c->leb_size) {
 477                         /* An empty LEB was returned */
 478                         dbg_gc("LEB %d is free, return it", lp.lnum);
 479                         /*
 480                          * ubifs_find_dirty_leb() doesn't return freeable index
 481                          * LEBs.
 482                          */
 483                         ubifs_assert(!(lp.flags & LPROPS_INDEX));
 484                         if (lp.free != c->leb_size) {
 485                                 /*
 486                                  * Write buffers must be sync'd before
 487                                  * unmapping freeable LEBs, because one of them
 488                                  * may contain data which obsoletes something
 489                                  * in 'lp.pnum'.
 490                                  */
 491                                 ret = gc_sync_wbufs(c);
 492                                 if (ret)
 493                                         goto out;
 494                                 ret = ubifs_change_one_lp(c, lp.lnum,
 495                                                           c->leb_size, 0, 0, 0,
 496                                                           0);
 497                                 if (ret)
 498                                         goto out;
 499                         }
 500                         ret = ubifs_leb_unmap(c, lp.lnum);
 501                         if (ret)
 502                                 goto out;
 503                         ret = lp.lnum;
 504                         break;
 505                 }
 506
 507                 space_before = c->leb_size - wbuf->offs - wbuf->used;
 508                 if (wbuf->lnum == -1)
 509                         space_before = 0;
 510
 511                 ret = ubifs_garbage_collect_leb(c, &lp);
 512                 if (ret < 0) {
 513                         if (ret == -EAGAIN || ret == -ENOSPC) {
 514                                 /*
 515                                  * These codes are not errors, so we have to
 516                                  * return the LEB to lprops. But if the
 517                                  * 'ubifs_return_leb()' function fails, its
 518                                  * failure code is propagated to the caller
 519                                  * instead of the original '-EAGAIN' or
 520                                  * '-ENOSPC'.
 521                                  */
 522                                 err = ubifs_return_leb(c, lp.lnum);
 523                                 if (err)
 524                                         ret = err;
 525                                 break;
 526                         }
 527                         goto out;
 528                 }
 529
 530                 if (ret == LEB_FREED) {
 531                         /* An LEB has been freed and is ready for use */
 532                         dbg_gc("LEB %d freed, return", lp.lnum);
 533                         ret = lp.lnum;
 534                         break;
 535                 }
 536
 537                 if (ret == LEB_FREED_IDX) {
 538                         /*
 539                          * This was an indexing LEB and it cannot be
 540                          * immediately used. And instead of requesting the
 541                          * commit straight away, we try to garbage collect some
 542                          * more.
 543                          */
 544                         dbg_gc("indexing LEB %d freed, continue", lp.lnum);
 545                         continue;
 546                 }
 547
 548                 ubifs_assert(ret == LEB_RETAINED);
 549                 space_after = c->leb_size - wbuf->offs - wbuf->used;
 550                 dbg_gc("LEB %d retained, freed %d bytes", lp.lnum,
 551                        space_after - space_before);
 552
 553                 if (space_after > space_before) {
 554                         /* GC makes progress, keep working */
 555                         min_space >>= 1;
 556                         if (min_space < c->dead_wm)
 557                                 min_space = c->dead_wm;
 558                         continue;
 559                 }
 560
 561                 dbg_gc("did not make progress");
 562
 563                 /*
 564                  * GC moved an LEB bud have not done any progress. This means
 565                  * that the previous GC head LEB contained too few free space
 566                  * and the LEB which was GC'ed contained only large nodes which
 567                  * did not fit that space.
 568                  *
 569                  * We can do 2 things:
 570                  * 1. pick another LEB in a hope it'll contain a small node
 571                  *    which will fit the space we have at the end of current GC
 572                  *    head LEB, but there is no guarantee, so we try this out
 573                  *    unless we have already been working for too long;
 574                  * 2. request an LEB with more dirty space, which will force
 575                  *    'ubifs_find_dirty_leb()' to start scanning the lprops
 576                  *    table, instead of just picking one from the heap
 577                  *    (previously it already picked the dirtiest LEB).
 578                  */
 579                 if (i < SOFT_LEBS_LIMIT) {
 580                         dbg_gc("try again");
 581                         continue;
 582                 }
 583
 584                 min_space <<= 1;
 585                 if (min_space > c->dark_wm)
 586                         min_space = c->dark_wm;
 587                 dbg_gc("set min. space to %d", min_space);
 588         }
 589
 590         if (ret == -ENOSPC && !list_empty(&c->idx_gc)) {
 591                 dbg_gc("no space, some index LEBs GC'ed, -EAGAIN");
 592                 ubifs_commit_required(c);
 593                 ret = -EAGAIN;
 594         }
 595
 596         err = ubifs_wbuf_sync_nolock(wbuf);
 597         if (!err)
 598                 err = ubifs_leb_unmap(c, c->gc_lnum);
 599         if (err) {
 600                 ret = err;
 601                 goto out;
 602         }
 603 out_unlock:
 604         mutex_unlock(&wbuf->io_mutex);
 605         return ret;
 606
 607 out:
 608         ubifs_assert(ret < 0);
 609         ubifs_assert(ret != -ENOSPC && ret != -EAGAIN);
 610         ubifs_ro_mode(c, ret);
 611         ubifs_wbuf_sync_nolock(wbuf);
 612         mutex_unlock(&wbuf->io_mutex);
 613         ubifs_return_leb(c, lp.lnum);
 614         return ret;
 615 }
 616
 617 /**
 618  * ubifs_gc_start_commit - garbage collection at start of commit.
 619  * @c: UBIFS file-system description object
 620  *
 621  * If a LEB has only dirty and free space, then we may safely unmap it and make
 622  * it free.  Note, we cannot do this with indexing LEBs because dirty space may
 623  * correspond index nodes that are required for recovery.  In that case, the
 624  * LEB cannot be unmapped until after the next commit.
 625  *
 626  * This function returns %0 upon success and a negative error code upon failure.
 627  */
 628 int ubifs_gc_start_commit(struct ubifs_info *c)
 629 {
 630         struct ubifs_gced_idx_leb *idx_gc;
 631         const struct ubifs_lprops *lp;
 632         int err = 0, flags;
 633
 634         ubifs_get_lprops(c);
 635
 636         /*
 637          * Unmap (non-index) freeable LEBs. Note that recovery requires that all
 638          * wbufs are sync'd before this, which is done in 'do_commit()'.
 639          */
 640         while (1) {
 641                 lp = ubifs_fast_find_freeable(c);
 642                 if (unlikely(IS_ERR(lp))) {
 643                         err = PTR_ERR(lp);
 644                         goto out;
 645                 }
 646                 if (!lp)
 647                         break;
 648                 ubifs_assert(!(lp->flags & LPROPS_TAKEN));
 649                 ubifs_assert(!(lp->flags & LPROPS_INDEX));
 650                 err = ubifs_leb_unmap(c, lp->lnum);
 651                 if (err)
 652                         goto out;
 653                 lp = ubifs_change_lp(c, lp, c->leb_size, 0, lp->flags, 0);
 654                 if (unlikely(IS_ERR(lp))) {
 655                         err = PTR_ERR(lp);
 656                         goto out;
 657                 }
 658                 ubifs_assert(!(lp->flags & LPROPS_TAKEN));
 659                 ubifs_assert(!(lp->flags & LPROPS_INDEX));
 660         }
 661
 662         /* Mark GC'd index LEBs OK to unmap after this commit finishes */
 663         list_for_each_entry(idx_gc, &c->idx_gc, list)
 664                 idx_gc->unmap = 1;
 665
 666         /* Record index freeable LEBs for unmapping after commit */
 667         while (1) {
 668                 lp = ubifs_fast_find_frdi_idx(c);
 669                 if (unlikely(IS_ERR(lp))) {
 670                         err = PTR_ERR(lp);
 671                         goto out;
 672                 }
 673                 if (!lp)
 674                         break;
 675                 idx_gc = kmalloc(sizeof(struct ubifs_gced_idx_leb), GFP_NOFS);
 676                 if (!idx_gc) {
 677                         err = -ENOMEM;
 678                         goto out;
 679                 }
 680                 ubifs_assert(!(lp->flags & LPROPS_TAKEN));
 681                 ubifs_assert(lp->flags & LPROPS_INDEX);
 682                 /* Don't release the LEB until after the next commit */
 683                 flags = (lp->flags | LPROPS_TAKEN) ^ LPROPS_INDEX;
 684                 lp = ubifs_change_lp(c, lp, c->leb_size, 0, flags, 1);
 685                 if (unlikely(IS_ERR(lp))) {
 686                         err = PTR_ERR(lp);
 687                         kfree(idx_gc);
 688                         goto out;
 689                 }
 690                 ubifs_assert(lp->flags & LPROPS_TAKEN);
 691                 ubifs_assert(!(lp->flags & LPROPS_INDEX));
 692                 idx_gc->lnum = lp->lnum;
 693                 idx_gc->unmap = 1;
 694                 list_add(&idx_gc->list, &c->idx_gc);
 695         }
 696 out:
 697         ubifs_release_lprops(c);
 698         return err;
 699 }
 700
 701 /**
 702  * ubifs_gc_end_commit - garbage collection at end of commit.
 703  * @c: UBIFS file-system description object
 704  *
 705  * This function completes out-of-place garbage collection of index LEBs.
 706  */
 707 int ubifs_gc_end_commit(struct ubifs_info *c)
 708 {
 709         struct ubifs_gced_idx_leb *idx_gc, *tmp;
 710         struct ubifs_wbuf *wbuf;
 711         int err = 0;
 712
 713         wbuf = &c->jheads[GCHD].wbuf;
 714         mutex_lock_nested(&wbuf->io_mutex, wbuf->jhead);
 715         list_for_each_entry_safe(idx_gc, tmp, &c->idx_gc, list)
 716                 if (idx_gc->unmap) {
 717                         dbg_gc("LEB %d", idx_gc->lnum);
 718                         err = ubifs_leb_unmap(c, idx_gc->lnum);
 719                         if (err)
 720                                 goto out;
 721                         err = ubifs_change_one_lp(c, idx_gc->lnum, LPROPS_NC,
 722                                           LPROPS_NC, 0, LPROPS_TAKEN, -1);
 723                         if (err)
 724                                 goto out;
 725                         list_del(&idx_gc->list);
 726                         kfree(idx_gc);
 727                 }
 728 out:
 729         mutex_unlock(&wbuf->io_mutex);
 730         return err;
 731 }
 732
 733 /**
 734  * ubifs_destroy_idx_gc - destroy idx_gc list.
 735  * @c: UBIFS file-system description object
 736  *
 737  * This function destroys the idx_gc list. It is called when unmounting or
 738  * remounting read-only so locks are not needed.
 739  */
 740 void ubifs_destroy_idx_gc(struct ubifs_info *c)
 741 {
 742         while (!list_empty(&c->idx_gc)) {
 743                 struct ubifs_gced_idx_leb *idx_gc;
 744
 745                 idx_gc = list_entry(c->idx_gc.next, struct ubifs_gced_idx_leb,
 746                                     list);
 747                 c->idx_gc_cnt -= 1;
 748                 list_del(&idx_gc->list);
 749                 kfree(idx_gc);
 750         }
 751
 752 }
 753
 754 /**
 755  * ubifs_get_idx_gc_leb - get a LEB from GC'd index LEB list.
 756  * @c: UBIFS file-system description object
 757  *
 758  * Called during start commit so locks are not needed.
 759  */
 760 int ubifs_get_idx_gc_leb(struct ubifs_info *c)
 761 {
 762         struct ubifs_gced_idx_leb *idx_gc;
 763         int lnum;
 764
 765         if (list_empty(&c->idx_gc))
 766                 return -ENOSPC;
 767         idx_gc = list_entry(c->idx_gc.next, struct ubifs_gced_idx_leb, list);
 768         lnum = idx_gc->lnum;
 769         /* c->idx_gc_cnt is updated by the caller when lprops are updated */
 770         list_del(&idx_gc->list);
 771         kfree(idx_gc);
 772         return lnum;
 773 }