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  * Notes about dead watermark. At current UBIFS implementation we assume that
  36  * LEBs which have less than @c->dead_wm bytes of free + dirty space are full
  37  * and not worth garbage-collecting. The dead watermark is one min. I/O unit
  38  * size, or min. UBIFS node size, depending on what is greater. Indeed, UBIFS
  39  * Garbage Collector has to synchronize the GC head's write buffer before
  40  * returning, so this is about wasting one min. I/O unit. However, UBIFS GC can
  41  * actually reclaim even very small pieces of dirty space by garbage collecting
  42  * enough dirty LEBs, but we do not bother doing this at this implementation.
  43  *
  44  * Notes about dark watermark. The results of GC work depends on how big are
  45  * the UBIFS nodes GC deals with. Large nodes make GC waste more space. Indeed,
  46  * if GC move data from LEB A to LEB B and nodes in LEB A are large, GC would
  47  * have to waste large pieces of free space at the end of LEB B, because nodes
  48  * from LEB A would not fit. And the worst situation is when all nodes are of
  49  * maximum size. So dark watermark is the amount of free + dirty space in LEB
  50  * which are guaranteed to be reclaimable. If LEB has less space, the GC might
  51  * be unable to reclaim it. So, LEBs with free + dirty greater than dark
  52  * watermark are "good" LEBs from GC's point of few. The other LEBs are not so
  53  * good, and GC takes extra care when moving them.
  54  */
  55
  56 #include <linux/pagemap.h>
  57 #include <linux/list_sort.h>
  58 #include "ubifs.h"
  59
  60 /*
  61  * GC may need to move more than one LEB to make progress. The below constants
  62  * define "soft" and "hard" limits on the number of LEBs the garbage collector
  63  * may move.
  64  */
  65 #define SOFT_LEBS_LIMIT 4
  66 #define HARD_LEBS_LIMIT 32
  67
  68 /**
  69  * switch_gc_head - switch the garbage collection journal head.
  70  * @c: UBIFS file-system description object
  71  * @buf: buffer to write
  72  * @len: length of the buffer to write
  73  * @lnum: LEB number written is returned here
  74  * @offs: offset written is returned here
  75  *
  76  * This function switch the GC head to the next LEB which is reserved in
  77  * @c->gc_lnum. Returns %0 in case of success, %-EAGAIN if commit is required,
  78  * and other negative error code in case of failures.
  79  */
  80 static int switch_gc_head(struct ubifs_info *c)
  81 {
  82         int err, gc_lnum = c->gc_lnum;
  83         struct ubifs_wbuf *wbuf = &c->jheads[GCHD].wbuf;
  84
  85         ubifs_assert(gc_lnum != -1);
  86         dbg_gc("switch GC head from LEB %d:%d to LEB %d (waste %d bytes)",
  87                wbuf->lnum, wbuf->offs + wbuf->used, gc_lnum,
  88                c->leb_size - wbuf->offs - wbuf->used);
  89
  90         err = ubifs_wbuf_sync_nolock(wbuf);
  91         if (err)
  92                 return err;
  93
  94         /*
  95          * The GC write-buffer was synchronized, we may safely unmap
  96          * 'c->gc_lnum'.
  97          */
  98         err = ubifs_leb_unmap(c, gc_lnum);
  99         if (err)
 100                 return err;
 101
 102         err = ubifs_add_bud_to_log(c, GCHD, gc_lnum, 0);
 103         if (err)
 104                 return err;
 105
 106         c->gc_lnum = -1;
 107         err = ubifs_wbuf_seek_nolock(wbuf, gc_lnum, 0, UBI_LONGTERM);
 108         return err;
 109 }
 110
 111 /**
 112  * data_nodes_cmp - compare 2 data nodes.
 113  * @priv: UBIFS file-system description object
 114  * @a: first data node
 115  * @a: second data node
 116  *
 117  * This function compares data nodes @a and @b. Returns %1 if @a has greater
 118  * inode or block number, and %-1 otherwise.
 119  */
 120 int data_nodes_cmp(void *priv, struct list_head *a, struct list_head *b)
 121 {
 122         ino_t inuma, inumb;
 123         struct ubifs_info *c = priv;
 124         struct ubifs_scan_node *sa, *sb;
 125
 126         cond_resched();
 127         sa = list_entry(a, struct ubifs_scan_node, list);
 128         sb = list_entry(b, struct ubifs_scan_node, list);
 129         ubifs_assert(key_type(c, &sa->key) == UBIFS_DATA_KEY);
 130         ubifs_assert(key_type(c, &sb->key) == UBIFS_DATA_KEY);
 131
 132         inuma = key_inum(c, &sa->key);
 133         inumb = key_inum(c, &sb->key);
 134
 135         if (inuma == inumb) {
 136                 unsigned int blka = key_block(c, &sa->key);
 137                 unsigned int blkb = key_block(c, &sb->key);
 138
 139                 if (blka <= blkb)
 140                         return -1;
 141         } else if (inuma <= inumb)
 142                 return -1;
 143
 144         return 1;
 145 }
 146
 147 /*
 148  * nondata_nodes_cmp - compare 2 non-data nodes.
 149  * @priv: UBIFS file-system description object
 150  * @a: first node
 151  * @a: second node
 152  *
 153  * This function compares nodes @a and @b. It makes sure that inode nodes go
 154  * first and sorted by length in descending order. Directory entry nodes go
 155  * after inode nodes and are sorted in ascending hash valuer order.
 156  */
 157 int nondata_nodes_cmp(void *priv, struct list_head *a, struct list_head *b)
 158 {
 159         int typea, typeb;
 160         ino_t inuma, inumb;
 161         struct ubifs_info *c = priv;
 162         struct ubifs_scan_node *sa, *sb;
 163
 164         cond_resched();
 165         sa = list_entry(a, struct ubifs_scan_node, list);
 166         sb = list_entry(b, struct ubifs_scan_node, list);
 167         typea = key_type(c, &sa->key);
 168         typeb = key_type(c, &sb->key);
 169         ubifs_assert(typea != UBIFS_DATA_KEY && typeb != UBIFS_DATA_KEY);
 170
 171         /* Inodes go before directory entries */
 172         if (typea == UBIFS_INO_KEY) {
 173                 if (typeb == UBIFS_INO_KEY)
 174                         return sb->len - sa->len;
 175                 return -1;
 176         }
 177         if (typeb == UBIFS_INO_KEY)
 178                 return 1;
 179
 180         ubifs_assert(typea == UBIFS_DENT_KEY && typeb == UBIFS_DENT_KEY);
 181         inuma = key_inum(c, &sa->key);
 182         inumb = key_inum(c, &sb->key);
 183
 184         if (inuma == inumb) {
 185                 uint32_t hasha = key_hash(c, &sa->key);
 186                 uint32_t hashb = key_hash(c, &sb->key);
 187
 188                 if (hasha <= hashb)
 189                         return -1;
 190         } else if (inuma <= inumb)
 191                 return -1;
 192
 193         return 1;
 194 }
 195
 196 /**
 197  * sort_nodes - sort nodes for GC.
 198  * @c: UBIFS file-system description object
 199  * @sleb: describes nodes to sort and contains the result on exit
 200  * @nondata: contains non-data nodes on exit
 201  * @min: minimum node size is returned here
 202  *
 203  * This function sorts the list of inodes to garbage collect. First of all, it
 204  * kills obsolete nodes and separates data and non-data nodes to the
 205  * @sleb->nodes and @nondata lists correspondingly.
 206  *
 207  * Data nodes are then sorted in block number order - this is important for
 208  * bulk-read; data nodes with lower inode number go before data nodes with
 209  * higher inode number, and data nodes with lower block number go before data
 210  * nodes with higher block number;
 211  *
 212  * Non-data nodes are sorted as follows.
 213  *   o First go inode nodes - they are sorted in descending length order.
 214  *   o Then go directory entry nodes - they are sorted in hash order, which
 215  *     should supposedly optimize 'readdir()'. Direntry nodes with lower parent
 216  *     inode number go before direntry nodes with higher parent inode number,
 217  *     and direntry nodes with lower name hash values go before direntry nodes
 218  *     with higher name hash values.
 219  *
 220  * This function returns zero in case of success and a negative error code in
 221  * case of failure.
 222  */
 223 static int sort_nodes(struct ubifs_info *c, struct ubifs_scan_leb *sleb,
 224                       struct list_head *nondata, int *min)
 225 {
 226         struct ubifs_scan_node *snod, *tmp;
 227
 228         *min = INT_MAX;
 229
 230         /* Separate data nodes and non-data nodes */
 231         list_for_each_entry_safe(snod, tmp, &sleb->nodes, list) {
 232                 int err;
 233
 234                 ubifs_assert(snod->type != UBIFS_IDX_NODE);
 235                 ubifs_assert(snod->type != UBIFS_REF_NODE);
 236                 ubifs_assert(snod->type != UBIFS_CS_NODE);
 237
 238                 err = ubifs_tnc_has_node(c, &snod->key, 0, sleb->lnum,
 239                                          snod->offs, 0);
 240                 if (err < 0)
 241                         return err;
 242
 243                 if (!err) {
 244                         /* The node is obsolete, remove it from the list */
 245                         list_del(&snod->list);
 246                         kfree(snod);
 247                         continue;
 248                 }
 249
 250                 if (snod->len < *min)
 251                         *min = snod->len;
 252
 253                 if (key_type(c, &snod->key) != UBIFS_DATA_KEY)
 254                         list_move_tail(&snod->list, nondata);
 255         }
 256
 257         /* Sort data and non-data nodes */
 258         list_sort(c, &sleb->nodes, &data_nodes_cmp);
 259         list_sort(c, nondata, &nondata_nodes_cmp);
 260         return 0;
 261 }
 262
 263 /**
 264  * move_node - move a node.
 265  * @c: UBIFS file-system description object
 266  * @sleb: describes the LEB to move nodes from
 267  * @snod: the mode to move
 268  * @wbuf: write-buffer to move node to
 269  *
 270  * This function moves node @snod to @wbuf, changes TNC correspondingly, and
 271  * destroys @snod. Returns zero in case of success and a negative error code in
 272  * case of failure.
 273  */
 274 static int move_node(struct ubifs_info *c, struct ubifs_scan_leb *sleb,
 275                      struct ubifs_scan_node *snod, struct ubifs_wbuf *wbuf)
 276 {
 277         int err, new_lnum = wbuf->lnum, new_offs = wbuf->offs + wbuf->used;
 278
 279         cond_resched();
 280         err = ubifs_wbuf_write_nolock(wbuf, snod->node, snod->len);
 281         if (err)
 282                 return err;
 283
 284         err = ubifs_tnc_replace(c, &snod->key, sleb->lnum,
 285                                 snod->offs, new_lnum, new_offs,
 286                                 snod->len);
 287         list_del(&snod->list);
 288         kfree(snod);
 289         return err;
 290 }
 291
 292 /**
 293  * move_nodes - move nodes.
 294  * @c: UBIFS file-system description object
 295  * @sleb: describes the LEB to move nodes from
 296  *
 297  * This function moves valid nodes from data LEB described by @sleb to the GC
 298  * journal head. This function returns zero in case of success, %-EAGAIN if
 299  * commit is required, and other negative error codes in case of other
 300  * failures.
 301  */
 302 static int move_nodes(struct ubifs_info *c, struct ubifs_scan_leb *sleb)
 303 {
 304         int err, min;
 305         LIST_HEAD(nondata);
 306         struct ubifs_wbuf *wbuf = &c->jheads[GCHD].wbuf;
 307
 308         if (wbuf->lnum == -1) {
 309                 /*
 310                  * The GC journal head is not set, because it is the first GC
 311                  * invocation since mount.
 312                  */
 313                 err = switch_gc_head(c);
 314                 if (err)
 315                         return err;
 316         }
 317
 318         err = sort_nodes(c, sleb, &nondata, &min);
 319         if (err)
 320                 goto out;
 321
 322         /* Write nodes to their new location. Use the first-fit strategy */
 323         while (1) {
 324                 int avail;
 325                 struct ubifs_scan_node *snod, *tmp;
 326
 327                 /* Move data nodes */
 328                 list_for_each_entry_safe(snod, tmp, &sleb->nodes, list) {
 329                         avail = c->leb_size - wbuf->offs - wbuf->used;
 330                         if  (snod->len > avail)
 331                                 /*
 332                                  * Do not skip data nodes in order to optimize
 333                                  * bulk-read.
 334                                  */
 335                                 break;
 336
 337                         err = move_node(c, sleb, snod, wbuf);
 338                         if (err)
 339                                 goto out;
 340                 }
 341
 342                 /* Move non-data nodes */
 343                 list_for_each_entry_safe(snod, tmp, &nondata, list) {
 344                         avail = c->leb_size - wbuf->offs - wbuf->used;
 345                         if (avail < min)
 346                                 break;
 347
 348                         if  (snod->len > avail) {
 349                                 /*
 350                                  * Keep going only if this is an inode with
 351                                  * some data. Otherwise stop and switch the GC
 352                                  * head. IOW, we assume that data-less inode
 353                                  * nodes and direntry nodes are roughly of the
 354                                  * same size.
 355                                  */
 356                                 if (key_type(c, &snod->key) == UBIFS_DENT_KEY ||
 357                                     snod->len == UBIFS_INO_NODE_SZ)
 358                                         break;
 359                                 continue;
 360                         }
 361
 362                         err = move_node(c, sleb, snod, wbuf);
 363                         if (err)
 364                                 goto out;
 365                 }
 366
 367                 if (list_empty(&sleb->nodes) && list_empty(&nondata))
 368                         break;
 369
 370                 /*
 371                  * Waste the rest of the space in the LEB and switch to the
 372                  * next LEB.
 373                  */
 374                 err = switch_gc_head(c);
 375                 if (err)
 376                         goto out;
 377         }
 378
 379         return 0;
 380
 381 out:
 382         list_splice_tail(&nondata, &sleb->nodes);
 383         return err;
 384 }
 385
 386 /**
 387  * gc_sync_wbufs - sync write-buffers for GC.
 388  * @c: UBIFS file-system description object
 389  *
 390  * We must guarantee that obsoleting nodes are on flash. Unfortunately they may
 391  * be in a write-buffer instead. That is, a node could be written to a
 392  * write-buffer, obsoleting another node in a LEB that is GC'd. If that LEB is
 393  * erased before the write-buffer is sync'd and then there is an unclean
 394  * unmount, then an existing node is lost. To avoid this, we sync all
 395  * write-buffers.
 396  *
 397  * This function returns %0 on success or a negative error code on failure.
 398  */
 399 static int gc_sync_wbufs(struct ubifs_info *c)
 400 {
 401         int err, i;
 402
 403         for (i = 0; i < c->jhead_cnt; i++) {
 404                 if (i == GCHD)
 405                         continue;
 406                 err = ubifs_wbuf_sync(&c->jheads[i].wbuf);
 407                 if (err)
 408                         return err;
 409         }
 410         return 0;
 411 }
 412
 413 /**
 414  * ubifs_garbage_collect_leb - garbage-collect a logical eraseblock.
 415  * @c: UBIFS file-system description object
 416  * @lp: describes the LEB to garbage collect
 417  *
 418  * This function garbage-collects an LEB and returns one of the @LEB_FREED,
 419  * @LEB_RETAINED, etc positive codes in case of success, %-EAGAIN if commit is
 420  * required, and other negative error codes in case of failures.
 421  */
 422 int ubifs_garbage_collect_leb(struct ubifs_info *c, struct ubifs_lprops *lp)
 423 {
 424         struct ubifs_scan_leb *sleb;
 425         struct ubifs_scan_node *snod;
 426         struct ubifs_wbuf *wbuf = &c->jheads[GCHD].wbuf;
 427         int err = 0, lnum = lp->lnum;
 428
 429         ubifs_assert(c->gc_lnum != -1 || wbuf->offs + wbuf->used == 0 ||
 430                      c->need_recovery);
 431         ubifs_assert(c->gc_lnum != lnum);
 432         ubifs_assert(wbuf->lnum != lnum);
 433
 434         /*
 435          * We scan the entire LEB even though we only really need to scan up to
 436          * (c->leb_size - lp->free).
 437          */
 438         sleb = ubifs_scan(c, lnum, 0, c->sbuf, 0);
 439         if (IS_ERR(sleb))
 440                 return PTR_ERR(sleb);
 441
 442         ubifs_assert(!list_empty(&sleb->nodes));
 443         snod = list_entry(sleb->nodes.next, struct ubifs_scan_node, list);
 444
 445         if (snod->type == UBIFS_IDX_NODE) {
 446                 struct ubifs_gced_idx_leb *idx_gc;
 447
 448                 dbg_gc("indexing LEB %d (free %d, dirty %d)",
 449                        lnum, lp->free, lp->dirty);
 450                 list_for_each_entry(snod, &sleb->nodes, list) {
 451                         struct ubifs_idx_node *idx = snod->node;
 452                         int level = le16_to_cpu(idx->level);
 453
 454                         ubifs_assert(snod->type == UBIFS_IDX_NODE);
 455                         key_read(c, ubifs_idx_key(c, idx), &snod->key);
 456                         err = ubifs_dirty_idx_node(c, &snod->key, level, lnum,
 457                                                    snod->offs);
 458                         if (err)
 459                                 goto out;
 460                 }
 461
 462                 idx_gc = kmalloc(sizeof(struct ubifs_gced_idx_leb), GFP_NOFS);
 463                 if (!idx_gc) {
 464                         err = -ENOMEM;
 465                         goto out;
 466                 }
 467
 468                 idx_gc->lnum = lnum;
 469                 idx_gc->unmap = 0;
 470                 list_add(&idx_gc->list, &c->idx_gc);
 471
 472                 /*
 473                  * Don't release the LEB until after the next commit, because
 474                  * it may contain data which is needed for recovery. So
 475                  * although we freed this LEB, it will become usable only after
 476                  * the commit.
 477                  */
 478                 err = ubifs_change_one_lp(c, lnum, c->leb_size, 0, 0,
 479                                           LPROPS_INDEX, 1);
 480                 if (err)
 481                         goto out;
 482                 err = LEB_FREED_IDX;
 483         } else {
 484                 dbg_gc("data LEB %d (free %d, dirty %d)",
 485                        lnum, lp->free, lp->dirty);
 486
 487                 err = move_nodes(c, sleb);
 488                 if (err)
 489                         goto out_inc_seq;
 490
 491                 err = gc_sync_wbufs(c);
 492                 if (err)
 493                         goto out_inc_seq;
 494
 495                 err = ubifs_change_one_lp(c, lnum, c->leb_size, 0, 0, 0, 0);
 496                 if (err)
 497                         goto out_inc_seq;
 498
 499                 /* Allow for races with TNC */
 500                 c->gced_lnum = lnum;
 501                 smp_wmb();
 502                 c->gc_seq += 1;
 503                 smp_wmb();
 504
 505                 if (c->gc_lnum == -1) {
 506                         c->gc_lnum = lnum;
 507                         err = LEB_RETAINED;
 508                 } else {
 509                         err = ubifs_wbuf_sync_nolock(wbuf);
 510                         if (err)
 511                                 goto out;
 512
 513                         err = ubifs_leb_unmap(c, lnum);
 514                         if (err)
 515                                 goto out;
 516
 517                         err = LEB_FREED;
 518                 }
 519         }
 520
 521 out:
 522         ubifs_scan_destroy(sleb);
 523         return err;
 524
 525 out_inc_seq:
 526         /* We may have moved at least some nodes so allow for races with TNC */
 527         c->gced_lnum = lnum;
 528         smp_wmb();
 529         c->gc_seq += 1;
 530         smp_wmb();
 531         goto out;
 532 }
 533
 534 /**
 535  * ubifs_garbage_collect - UBIFS garbage collector.
 536  * @c: UBIFS file-system description object
 537  * @anyway: do GC even if there are free LEBs
 538  *
 539  * This function does out-of-place garbage collection. The return codes are:
 540  *   o positive LEB number if the LEB has been freed and may be used;
 541  *   o %-EAGAIN if the caller has to run commit;
 542  *   o %-ENOSPC if GC failed to make any progress;
 543  *   o other negative error codes in case of other errors.
 544  *
 545  * Garbage collector writes data to the journal when GC'ing data LEBs, and just
 546  * marking indexing nodes dirty when GC'ing indexing LEBs. Thus, at some point
 547  * commit may be required. But commit cannot be run from inside GC, because the
 548  * caller might be holding the commit lock, so %-EAGAIN is returned instead;
 549  * And this error code means that the caller has to run commit, and re-run GC
 550  * if there is still no free space.
 551  *
 552  * There are many reasons why this function may return %-EAGAIN:
 553  * o the log is full and there is no space to write an LEB reference for
 554  *   @c->gc_lnum;
 555  * o the journal is too large and exceeds size limitations;
 556  * o GC moved indexing LEBs, but they can be used only after the commit;
 557  * o the shrinker fails to find clean znodes to free and requests the commit;
 558  * o etc.
 559  *
 560  * Note, if the file-system is close to be full, this function may return
 561  * %-EAGAIN infinitely, so the caller has to limit amount of re-invocations of
 562  * the function. E.g., this happens if the limits on the journal size are too
 563  * tough and GC writes too much to the journal before an LEB is freed. This
 564  * might also mean that the journal is too large, and the TNC becomes to big,
 565  * so that the shrinker is constantly called, finds not clean znodes to free,
 566  * and requests commit. Well, this may also happen if the journal is all right,
 567  * but another kernel process consumes too much memory. Anyway, infinite
 568  * %-EAGAIN may happen, but in some extreme/misconfiguration cases.
 569  */
 570 int ubifs_garbage_collect(struct ubifs_info *c, int anyway)
 571 {
 572         int i, err, ret, min_space = c->dead_wm;
 573         struct ubifs_lprops lp;
 574         struct ubifs_wbuf *wbuf = &c->jheads[GCHD].wbuf;
 575
 576         ubifs_assert_cmt_locked(c);
 577
 578         if (ubifs_gc_should_commit(c))
 579                 return -EAGAIN;
 580
 581         mutex_lock_nested(&wbuf->io_mutex, wbuf->jhead);
 582
 583         if (c->ro_media) {
 584                 ret = -EROFS;
 585                 goto out_unlock;
 586         }
 587
 588         /* We expect the write-buffer to be empty on entry */
 589         ubifs_assert(!wbuf->used);
 590
 591         for (i = 0; ; i++) {
 592                 int space_before = c->leb_size - wbuf->offs - wbuf->used;
 593                 int space_after;
 594
 595                 cond_resched();
 596
 597                 /* Give the commit an opportunity to run */
 598                 if (ubifs_gc_should_commit(c)) {
 599                         ret = -EAGAIN;
 600                         break;
 601                 }
 602
 603                 if (i > SOFT_LEBS_LIMIT && !list_empty(&c->idx_gc)) {
 604                         /*
 605                          * We've done enough iterations. Indexing LEBs were
 606                          * moved and will be available after the commit.
 607                          */
 608                         dbg_gc("soft limit, some index LEBs GC'ed, -EAGAIN");
 609                         ubifs_commit_required(c);
 610                         ret = -EAGAIN;
 611                         break;
 612                 }
 613
 614                 if (i > HARD_LEBS_LIMIT) {
 615                         /*
 616                          * We've moved too many LEBs and have not made
 617                          * progress, give up.
 618                          */
 619                         dbg_gc("hard limit, -ENOSPC");
 620                         ret = -ENOSPC;
 621                         break;
 622                 }
 623
 624                 /*
 625                  * Empty and freeable LEBs can turn up while we waited for
 626                  * the wbuf lock, or while we have been running GC. In that
 627                  * case, we should just return one of those instead of
 628                  * continuing to GC dirty LEBs. Hence we request
 629                  * 'ubifs_find_dirty_leb()' to return an empty LEB if it can.
 630                  */
 631                 ret = ubifs_find_dirty_leb(c, &lp, min_space, anyway ? 0 : 1);
 632                 if (ret) {
 633                         if (ret == -ENOSPC)
 634                                 dbg_gc("no more dirty LEBs");
 635                         break;
 636                 }
 637
 638                 dbg_gc("found LEB %d: free %d, dirty %d, sum %d "
 639                        "(min. space %d)", lp.lnum, lp.free, lp.dirty,
 640                        lp.free + lp.dirty, min_space);
 641
 642                 if (lp.free + lp.dirty == c->leb_size) {
 643                         /* An empty LEB was returned */
 644                         dbg_gc("LEB %d is free, return it", lp.lnum);
 645                         /*
 646                          * ubifs_find_dirty_leb() doesn't return freeable index
 647                          * LEBs.
 648                          */
 649                         ubifs_assert(!(lp.flags & LPROPS_INDEX));
 650                         if (lp.free != c->leb_size) {
 651                                 /*
 652                                  * Write buffers must be sync'd before
 653                                  * unmapping freeable LEBs, because one of them
 654                                  * may contain data which obsoletes something
 655                                  * in 'lp.pnum'.
 656                                  */
 657                                 ret = gc_sync_wbufs(c);
 658                                 if (ret)
 659                                         goto out;
 660                                 ret = ubifs_change_one_lp(c, lp.lnum,
 661                                                           c->leb_size, 0, 0, 0,
 662                                                           0);
 663                                 if (ret)
 664                                         goto out;
 665                         }
 666                         ret = ubifs_leb_unmap(c, lp.lnum);
 667                         if (ret)
 668                                 goto out;
 669                         ret = lp.lnum;
 670                         break;
 671                 }
 672
 673                 space_before = c->leb_size - wbuf->offs - wbuf->used;
 674                 if (wbuf->lnum == -1)
 675                         space_before = 0;
 676
 677                 ret = ubifs_garbage_collect_leb(c, &lp);
 678                 if (ret < 0) {
 679                         if (ret == -EAGAIN || ret == -ENOSPC) {
 680                                 /*
 681                                  * These codes are not errors, so we have to
 682                                  * return the LEB to lprops. But if the
 683                                  * 'ubifs_return_leb()' function fails, its
 684                                  * failure code is propagated to the caller
 685                                  * instead of the original '-EAGAIN' or
 686                                  * '-ENOSPC'.
 687                                  */
 688                                 err = ubifs_return_leb(c, lp.lnum);
 689                                 if (err)
 690                                         ret = err;
 691                                 break;
 692                         }
 693                         goto out;
 694                 }
 695
 696                 if (ret == LEB_FREED) {
 697                         /* An LEB has been freed and is ready for use */
 698                         dbg_gc("LEB %d freed, return", lp.lnum);
 699                         ret = lp.lnum;
 700                         break;
 701                 }
 702
 703                 if (ret == LEB_FREED_IDX) {
 704                         /*
 705                          * This was an indexing LEB and it cannot be
 706                          * immediately used. And instead of requesting the
 707                          * commit straight away, we try to garbage collect some
 708                          * more.
 709                          */
 710                         dbg_gc("indexing LEB %d freed, continue", lp.lnum);
 711                         continue;
 712                 }
 713
 714                 ubifs_assert(ret == LEB_RETAINED);
 715                 space_after = c->leb_size - wbuf->offs - wbuf->used;
 716                 dbg_gc("LEB %d retained, freed %d bytes", lp.lnum,
 717                        space_after - space_before);
 718
 719                 if (space_after > space_before) {
 720                         /* GC makes progress, keep working */
 721                         min_space >>= 1;
 722                         if (min_space < c->dead_wm)
 723                                 min_space = c->dead_wm;
 724                         continue;
 725                 }
 726
 727                 dbg_gc("did not make progress");
 728
 729                 /*
 730                  * GC moved an LEB bud have not done any progress. This means
 731                  * that the previous GC head LEB contained too few free space
 732                  * and the LEB which was GC'ed contained only large nodes which
 733                  * did not fit that space.
 734                  *
 735                  * We can do 2 things:
 736                  * 1. pick another LEB in a hope it'll contain a small node
 737                  *    which will fit the space we have at the end of current GC
 738                  *    head LEB, but there is no guarantee, so we try this out
 739                  *    unless we have already been working for too long;
 740                  * 2. request an LEB with more dirty space, which will force
 741                  *    'ubifs_find_dirty_leb()' to start scanning the lprops
 742                  *    table, instead of just picking one from the heap
 743                  *    (previously it already picked the dirtiest LEB).
 744                  */
 745                 if (i < SOFT_LEBS_LIMIT) {
 746                         dbg_gc("try again");
 747                         continue;
 748                 }
 749
 750                 min_space <<= 1;
 751                 if (min_space > c->dark_wm)
 752                         min_space = c->dark_wm;
 753                 dbg_gc("set min. space to %d", min_space);
 754         }
 755
 756         if (ret == -ENOSPC && !list_empty(&c->idx_gc)) {
 757                 dbg_gc("no space, some index LEBs GC'ed, -EAGAIN");
 758                 ubifs_commit_required(c);
 759                 ret = -EAGAIN;
 760         }
 761
 762         err = ubifs_wbuf_sync_nolock(wbuf);
 763         if (!err)
 764                 err = ubifs_leb_unmap(c, c->gc_lnum);
 765         if (err) {
 766                 ret = err;
 767                 goto out;
 768         }
 769 out_unlock:
 770         mutex_unlock(&wbuf->io_mutex);
 771         return ret;
 772
 773 out:
 774         ubifs_assert(ret < 0);
 775         ubifs_assert(ret != -ENOSPC && ret != -EAGAIN);
 776         ubifs_ro_mode(c, ret);
 777         ubifs_wbuf_sync_nolock(wbuf);
 778         mutex_unlock(&wbuf->io_mutex);
 779         ubifs_return_leb(c, lp.lnum);
 780         return ret;
 781 }
 782
 783 /**
 784  * ubifs_gc_start_commit - garbage collection at start of commit.
 785  * @c: UBIFS file-system description object
 786  *
 787  * If a LEB has only dirty and free space, then we may safely unmap it and make
 788  * it free.  Note, we cannot do this with indexing LEBs because dirty space may
 789  * correspond index nodes that are required for recovery.  In that case, the
 790  * LEB cannot be unmapped until after the next commit.
 791  *
 792  * This function returns %0 upon success and a negative error code upon failure.
 793  */
 794 int ubifs_gc_start_commit(struct ubifs_info *c)
 795 {
 796         struct ubifs_gced_idx_leb *idx_gc;
 797         const struct ubifs_lprops *lp;
 798         int err = 0, flags;
 799
 800         ubifs_get_lprops(c);
 801
 802         /*
 803          * Unmap (non-index) freeable LEBs. Note that recovery requires that all
 804          * wbufs are sync'd before this, which is done in 'do_commit()'.
 805          */
 806         while (1) {
 807                 lp = ubifs_fast_find_freeable(c);
 808                 if (IS_ERR(lp)) {
 809                         err = PTR_ERR(lp);
 810                         goto out;
 811                 }
 812                 if (!lp)
 813                         break;
 814                 ubifs_assert(!(lp->flags & LPROPS_TAKEN));
 815                 ubifs_assert(!(lp->flags & LPROPS_INDEX));
 816                 err = ubifs_leb_unmap(c, lp->lnum);
 817                 if (err)
 818                         goto out;
 819                 lp = ubifs_change_lp(c, lp, c->leb_size, 0, lp->flags, 0);
 820                 if (IS_ERR(lp)) {
 821                         err = PTR_ERR(lp);
 822                         goto out;
 823                 }
 824                 ubifs_assert(!(lp->flags & LPROPS_TAKEN));
 825                 ubifs_assert(!(lp->flags & LPROPS_INDEX));
 826         }
 827
 828         /* Mark GC'd index LEBs OK to unmap after this commit finishes */
 829         list_for_each_entry(idx_gc, &c->idx_gc, list)
 830                 idx_gc->unmap = 1;
 831
 832         /* Record index freeable LEBs for unmapping after commit */
 833         while (1) {
 834                 lp = ubifs_fast_find_frdi_idx(c);
 835                 if (IS_ERR(lp)) {
 836                         err = PTR_ERR(lp);
 837                         goto out;
 838                 }
 839                 if (!lp)
 840                         break;
 841                 idx_gc = kmalloc(sizeof(struct ubifs_gced_idx_leb), GFP_NOFS);
 842                 if (!idx_gc) {
 843                         err = -ENOMEM;
 844                         goto out;
 845                 }
 846                 ubifs_assert(!(lp->flags & LPROPS_TAKEN));
 847                 ubifs_assert(lp->flags & LPROPS_INDEX);
 848                 /* Don't release the LEB until after the next commit */
 849                 flags = (lp->flags | LPROPS_TAKEN) ^ LPROPS_INDEX;
 850                 lp = ubifs_change_lp(c, lp, c->leb_size, 0, flags, 1);
 851                 if (IS_ERR(lp)) {
 852                         err = PTR_ERR(lp);
 853                         kfree(idx_gc);
 854                         goto out;
 855                 }
 856                 ubifs_assert(lp->flags & LPROPS_TAKEN);
 857                 ubifs_assert(!(lp->flags & LPROPS_INDEX));
 858                 idx_gc->lnum = lp->lnum;
 859                 idx_gc->unmap = 1;
 860                 list_add(&idx_gc->list, &c->idx_gc);
 861         }
 862 out:
 863         ubifs_release_lprops(c);
 864         return err;
 865 }
 866
 867 /**
 868  * ubifs_gc_end_commit - garbage collection at end of commit.
 869  * @c: UBIFS file-system description object
 870  *
 871  * This function completes out-of-place garbage collection of index LEBs.
 872  */
 873 int ubifs_gc_end_commit(struct ubifs_info *c)
 874 {
 875         struct ubifs_gced_idx_leb *idx_gc, *tmp;
 876         struct ubifs_wbuf *wbuf;
 877         int err = 0;
 878
 879         wbuf = &c->jheads[GCHD].wbuf;
 880         mutex_lock_nested(&wbuf->io_mutex, wbuf->jhead);
 881         list_for_each_entry_safe(idx_gc, tmp, &c->idx_gc, list)
 882                 if (idx_gc->unmap) {
 883                         dbg_gc("LEB %d", idx_gc->lnum);
 884                         err = ubifs_leb_unmap(c, idx_gc->lnum);
 885                         if (err)
 886                                 goto out;
 887                         err = ubifs_change_one_lp(c, idx_gc->lnum, LPROPS_NC,
 888                                           LPROPS_NC, 0, LPROPS_TAKEN, -1);
 889                         if (err)
 890                                 goto out;
 891                         list_del(&idx_gc->list);
 892                         kfree(idx_gc);
 893                 }
 894 out:
 895         mutex_unlock(&wbuf->io_mutex);
 896         return err;
 897 }
 898
 899 /**
 900  * ubifs_destroy_idx_gc - destroy idx_gc list.
 901  * @c: UBIFS file-system description object
 902  *
 903  * This function destroys the @c->idx_gc list. It is called when unmounting
 904  * so locks are not needed. Returns zero in case of success and a negative
 905  * error code in case of failure.
 906  */
 907 void ubifs_destroy_idx_gc(struct ubifs_info *c)
 908 {
 909         while (!list_empty(&c->idx_gc)) {
 910                 struct ubifs_gced_idx_leb *idx_gc;
 911
 912                 idx_gc = list_entry(c->idx_gc.next, struct ubifs_gced_idx_leb,
 913                                     list);
 914                 c->idx_gc_cnt -= 1;
 915                 list_del(&idx_gc->list);
 916                 kfree(idx_gc);
 917         }
 918 }
 919
 920 /**
 921  * ubifs_get_idx_gc_leb - get a LEB from GC'd index LEB list.
 922  * @c: UBIFS file-system description object
 923  *
 924  * Called during start commit so locks are not needed.
 925  */
 926 int ubifs_get_idx_gc_leb(struct ubifs_info *c)
 927 {
 928         struct ubifs_gced_idx_leb *idx_gc;
 929         int lnum;
 930
 931         if (list_empty(&c->idx_gc))
 932                 return -ENOSPC;
 933         idx_gc = list_entry(c->idx_gc.next, struct ubifs_gced_idx_leb, list);
 934         lnum = idx_gc->lnum;
 935         /* c->idx_gc_cnt is updated by the caller when lprops are updated */
 936         list_del(&idx_gc->list);
 937         kfree(idx_gc);
 938         return lnum;
 939 }