linux/fs/ubifs/gc.c
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   1// SPDX-License-Identifier: GPL-2.0-only
   2/*
   3 * This file is part of UBIFS.
   4 *
   5 * Copyright (C) 2006-2008 Nokia Corporation.
   6 *
   7 * Authors: Adrian Hunter
   8 *          Artem Bityutskiy (Битюцкий Артём)
   9 */
  10
  11/*
  12 * This file implements garbage collection. The procedure for garbage collection
  13 * is different depending on whether a LEB as an index LEB (contains index
  14 * nodes) or not. For non-index LEBs, garbage collection finds a LEB which
  15 * contains a lot of dirty space (obsolete nodes), and copies the non-obsolete
  16 * nodes to the journal, at which point the garbage-collected LEB is free to be
  17 * reused. For index LEBs, garbage collection marks the non-obsolete index nodes
  18 * dirty in the TNC, and after the next commit, the garbage-collected LEB is
  19 * to be reused. Garbage collection will cause the number of dirty index nodes
  20 * to grow, however sufficient space is reserved for the index to ensure the
  21 * commit will never run out of space.
  22 *
  23 * Notes about dead watermark. At current UBIFS implementation we assume that
  24 * LEBs which have less than @c->dead_wm bytes of free + dirty space are full
  25 * and not worth garbage-collecting. The dead watermark is one min. I/O unit
  26 * size, or min. UBIFS node size, depending on what is greater. Indeed, UBIFS
  27 * Garbage Collector has to synchronize the GC head's write buffer before
  28 * returning, so this is about wasting one min. I/O unit. However, UBIFS GC can
  29 * actually reclaim even very small pieces of dirty space by garbage collecting
  30 * enough dirty LEBs, but we do not bother doing this at this implementation.
  31 *
  32 * Notes about dark watermark. The results of GC work depends on how big are
  33 * the UBIFS nodes GC deals with. Large nodes make GC waste more space. Indeed,
  34 * if GC move data from LEB A to LEB B and nodes in LEB A are large, GC would
  35 * have to waste large pieces of free space at the end of LEB B, because nodes
  36 * from LEB A would not fit. And the worst situation is when all nodes are of
  37 * maximum size. So dark watermark is the amount of free + dirty space in LEB
  38 * which are guaranteed to be reclaimable. If LEB has less space, the GC might
  39 * be unable to reclaim it. So, LEBs with free + dirty greater than dark
  40 * watermark are "good" LEBs from GC's point of view. The other LEBs are not so
  41 * good, and GC takes extra care when moving them.
  42 */
  43
  44#include <linux/slab.h>
  45#include <linux/pagemap.h>
  46#include <linux/list_sort.h>
  47#include "ubifs.h"
  48
  49/*
  50 * GC may need to move more than one LEB to make progress. The below constants
  51 * define "soft" and "hard" limits on the number of LEBs the garbage collector
  52 * may move.
  53 */
  54#define SOFT_LEBS_LIMIT 4
  55#define HARD_LEBS_LIMIT 32
  56
  57/**
  58 * switch_gc_head - switch the garbage collection journal head.
  59 * @c: UBIFS file-system description object
  60 *
  61 * This function switch the GC head to the next LEB which is reserved in
  62 * @c->gc_lnum. Returns %0 in case of success, %-EAGAIN if commit is required,
  63 * and other negative error code in case of failures.
  64 */
  65static int switch_gc_head(struct ubifs_info *c)
  66{
  67        int err, gc_lnum = c->gc_lnum;
  68        struct ubifs_wbuf *wbuf = &c->jheads[GCHD].wbuf;
  69
  70        ubifs_assert(c, gc_lnum != -1);
  71        dbg_gc("switch GC head from LEB %d:%d to LEB %d (waste %d bytes)",
  72               wbuf->lnum, wbuf->offs + wbuf->used, gc_lnum,
  73               c->leb_size - wbuf->offs - wbuf->used);
  74
  75        err = ubifs_wbuf_sync_nolock(wbuf);
  76        if (err)
  77                return err;
  78
  79        /*
  80         * The GC write-buffer was synchronized, we may safely unmap
  81         * 'c->gc_lnum'.
  82         */
  83        err = ubifs_leb_unmap(c, gc_lnum);
  84        if (err)
  85                return err;
  86
  87        err = ubifs_add_bud_to_log(c, GCHD, gc_lnum, 0);
  88        if (err)
  89                return err;
  90
  91        c->gc_lnum = -1;
  92        err = ubifs_wbuf_seek_nolock(wbuf, gc_lnum, 0);
  93        return err;
  94}
  95
  96/**
  97 * data_nodes_cmp - compare 2 data nodes.
  98 * @priv: UBIFS file-system description object
  99 * @a: first data node
 100 * @b: second data node
 101 *
 102 * This function compares data nodes @a and @b. Returns %1 if @a has greater
 103 * inode or block number, and %-1 otherwise.
 104 */
 105static int data_nodes_cmp(void *priv, const struct list_head *a,
 106                          const struct list_head *b)
 107{
 108        ino_t inuma, inumb;
 109        struct ubifs_info *c = priv;
 110        struct ubifs_scan_node *sa, *sb;
 111
 112        cond_resched();
 113        if (a == b)
 114                return 0;
 115
 116        sa = list_entry(a, struct ubifs_scan_node, list);
 117        sb = list_entry(b, struct ubifs_scan_node, list);
 118
 119        ubifs_assert(c, key_type(c, &sa->key) == UBIFS_DATA_KEY);
 120        ubifs_assert(c, key_type(c, &sb->key) == UBIFS_DATA_KEY);
 121        ubifs_assert(c, sa->type == UBIFS_DATA_NODE);
 122        ubifs_assert(c, sb->type == UBIFS_DATA_NODE);
 123
 124        inuma = key_inum(c, &sa->key);
 125        inumb = key_inum(c, &sb->key);
 126
 127        if (inuma == inumb) {
 128                unsigned int blka = key_block(c, &sa->key);
 129                unsigned int blkb = key_block(c, &sb->key);
 130
 131                if (blka <= blkb)
 132                        return -1;
 133        } else if (inuma <= inumb)
 134                return -1;
 135
 136        return 1;
 137}
 138
 139/*
 140 * nondata_nodes_cmp - compare 2 non-data nodes.
 141 * @priv: UBIFS file-system description object
 142 * @a: first node
 143 * @a: second node
 144 *
 145 * This function compares nodes @a and @b. It makes sure that inode nodes go
 146 * first and sorted by length in descending order. Directory entry nodes go
 147 * after inode nodes and are sorted in ascending hash valuer order.
 148 */
 149static int nondata_nodes_cmp(void *priv, const struct list_head *a,
 150                             const struct list_head *b)
 151{
 152        ino_t inuma, inumb;
 153        struct ubifs_info *c = priv;
 154        struct ubifs_scan_node *sa, *sb;
 155
 156        cond_resched();
 157        if (a == b)
 158                return 0;
 159
 160        sa = list_entry(a, struct ubifs_scan_node, list);
 161        sb = list_entry(b, struct ubifs_scan_node, list);
 162
 163        ubifs_assert(c, key_type(c, &sa->key) != UBIFS_DATA_KEY &&
 164                     key_type(c, &sb->key) != UBIFS_DATA_KEY);
 165        ubifs_assert(c, sa->type != UBIFS_DATA_NODE &&
 166                     sb->type != UBIFS_DATA_NODE);
 167
 168        /* Inodes go before directory entries */
 169        if (sa->type == UBIFS_INO_NODE) {
 170                if (sb->type == UBIFS_INO_NODE)
 171                        return sb->len - sa->len;
 172                return -1;
 173        }
 174        if (sb->type == UBIFS_INO_NODE)
 175                return 1;
 176
 177        ubifs_assert(c, key_type(c, &sa->key) == UBIFS_DENT_KEY ||
 178                     key_type(c, &sa->key) == UBIFS_XENT_KEY);
 179        ubifs_assert(c, key_type(c, &sb->key) == UBIFS_DENT_KEY ||
 180                     key_type(c, &sb->key) == UBIFS_XENT_KEY);
 181        ubifs_assert(c, sa->type == UBIFS_DENT_NODE ||
 182                     sa->type == UBIFS_XENT_NODE);
 183        ubifs_assert(c, sb->type == UBIFS_DENT_NODE ||
 184                     sb->type == UBIFS_XENT_NODE);
 185
 186        inuma = key_inum(c, &sa->key);
 187        inumb = key_inum(c, &sb->key);
 188
 189        if (inuma == inumb) {
 190                uint32_t hasha = key_hash(c, &sa->key);
 191                uint32_t hashb = key_hash(c, &sb->key);
 192
 193                if (hasha <= hashb)
 194                        return -1;
 195        } else if (inuma <= inumb)
 196                return -1;
 197
 198        return 1;
 199}
 200
 201/**
 202 * sort_nodes - sort nodes for GC.
 203 * @c: UBIFS file-system description object
 204 * @sleb: describes nodes to sort and contains the result on exit
 205 * @nondata: contains non-data nodes on exit
 206 * @min: minimum node size is returned here
 207 *
 208 * This function sorts the list of inodes to garbage collect. First of all, it
 209 * kills obsolete nodes and separates data and non-data nodes to the
 210 * @sleb->nodes and @nondata lists correspondingly.
 211 *
 212 * Data nodes are then sorted in block number order - this is important for
 213 * bulk-read; data nodes with lower inode number go before data nodes with
 214 * higher inode number, and data nodes with lower block number go before data
 215 * nodes with higher block number;
 216 *
 217 * Non-data nodes are sorted as follows.
 218 *   o First go inode nodes - they are sorted in descending length order.
 219 *   o Then go directory entry nodes - they are sorted in hash order, which
 220 *     should supposedly optimize 'readdir()'. Direntry nodes with lower parent
 221 *     inode number go before direntry nodes with higher parent inode number,
 222 *     and direntry nodes with lower name hash values go before direntry nodes
 223 *     with higher name hash values.
 224 *
 225 * This function returns zero in case of success and a negative error code in
 226 * case of failure.
 227 */
 228static int sort_nodes(struct ubifs_info *c, struct ubifs_scan_leb *sleb,
 229                      struct list_head *nondata, int *min)
 230{
 231        int err;
 232        struct ubifs_scan_node *snod, *tmp;
 233
 234        *min = INT_MAX;
 235
 236        /* Separate data nodes and non-data nodes */
 237        list_for_each_entry_safe(snod, tmp, &sleb->nodes, list) {
 238                ubifs_assert(c, snod->type == UBIFS_INO_NODE  ||
 239                             snod->type == UBIFS_DATA_NODE ||
 240                             snod->type == UBIFS_DENT_NODE ||
 241                             snod->type == UBIFS_XENT_NODE ||
 242                             snod->type == UBIFS_TRUN_NODE ||
 243                             snod->type == UBIFS_AUTH_NODE);
 244
 245                if (snod->type != UBIFS_INO_NODE  &&
 246                    snod->type != UBIFS_DATA_NODE &&
 247                    snod->type != UBIFS_DENT_NODE &&
 248                    snod->type != UBIFS_XENT_NODE) {
 249                        /* Probably truncation node, zap it */
 250                        list_del(&snod->list);
 251                        kfree(snod);
 252                        continue;
 253                }
 254
 255                ubifs_assert(c, key_type(c, &snod->key) == UBIFS_DATA_KEY ||
 256                             key_type(c, &snod->key) == UBIFS_INO_KEY  ||
 257                             key_type(c, &snod->key) == UBIFS_DENT_KEY ||
 258                             key_type(c, &snod->key) == UBIFS_XENT_KEY);
 259
 260                err = ubifs_tnc_has_node(c, &snod->key, 0, sleb->lnum,
 261                                         snod->offs, 0);
 262                if (err < 0)
 263                        return err;
 264
 265                if (!err) {
 266                        /* The node is obsolete, remove it from the list */
 267                        list_del(&snod->list);
 268                        kfree(snod);
 269                        continue;
 270                }
 271
 272                if (snod->len < *min)
 273                        *min = snod->len;
 274
 275                if (key_type(c, &snod->key) != UBIFS_DATA_KEY)
 276                        list_move_tail(&snod->list, nondata);
 277        }
 278
 279        /* Sort data and non-data nodes */
 280        list_sort(c, &sleb->nodes, &data_nodes_cmp);
 281        list_sort(c, nondata, &nondata_nodes_cmp);
 282
 283        err = dbg_check_data_nodes_order(c, &sleb->nodes);
 284        if (err)
 285                return err;
 286        err = dbg_check_nondata_nodes_order(c, nondata);
 287        if (err)
 288                return err;
 289        return 0;
 290}
 291
 292/**
 293 * move_node - move a node.
 294 * @c: UBIFS file-system description object
 295 * @sleb: describes the LEB to move nodes from
 296 * @snod: the mode to move
 297 * @wbuf: write-buffer to move node to
 298 *
 299 * This function moves node @snod to @wbuf, changes TNC correspondingly, and
 300 * destroys @snod. Returns zero in case of success and a negative error code in
 301 * case of failure.
 302 */
 303static int move_node(struct ubifs_info *c, struct ubifs_scan_leb *sleb,
 304                     struct ubifs_scan_node *snod, struct ubifs_wbuf *wbuf)
 305{
 306        int err, new_lnum = wbuf->lnum, new_offs = wbuf->offs + wbuf->used;
 307
 308        cond_resched();
 309        err = ubifs_wbuf_write_nolock(wbuf, snod->node, snod->len);
 310        if (err)
 311                return err;
 312
 313        err = ubifs_tnc_replace(c, &snod->key, sleb->lnum,
 314                                snod->offs, new_lnum, new_offs,
 315                                snod->len);
 316        list_del(&snod->list);
 317        kfree(snod);
 318        return err;
 319}
 320
 321/**
 322 * move_nodes - move nodes.
 323 * @c: UBIFS file-system description object
 324 * @sleb: describes the LEB to move nodes from
 325 *
 326 * This function moves valid nodes from data LEB described by @sleb to the GC
 327 * journal head. This function returns zero in case of success, %-EAGAIN if
 328 * commit is required, and other negative error codes in case of other
 329 * failures.
 330 */
 331static int move_nodes(struct ubifs_info *c, struct ubifs_scan_leb *sleb)
 332{
 333        int err, min;
 334        LIST_HEAD(nondata);
 335        struct ubifs_wbuf *wbuf = &c->jheads[GCHD].wbuf;
 336
 337        if (wbuf->lnum == -1) {
 338                /*
 339                 * The GC journal head is not set, because it is the first GC
 340                 * invocation since mount.
 341                 */
 342                err = switch_gc_head(c);
 343                if (err)
 344                        return err;
 345        }
 346
 347        err = sort_nodes(c, sleb, &nondata, &min);
 348        if (err)
 349                goto out;
 350
 351        /* Write nodes to their new location. Use the first-fit strategy */
 352        while (1) {
 353                int avail, moved = 0;
 354                struct ubifs_scan_node *snod, *tmp;
 355
 356                /* Move data nodes */
 357                list_for_each_entry_safe(snod, tmp, &sleb->nodes, list) {
 358                        avail = c->leb_size - wbuf->offs - wbuf->used -
 359                                        ubifs_auth_node_sz(c);
 360                        if  (snod->len > avail)
 361                                /*
 362                                 * Do not skip data nodes in order to optimize
 363                                 * bulk-read.
 364                                 */
 365                                break;
 366
 367                        err = ubifs_shash_update(c, c->jheads[GCHD].log_hash,
 368                                                 snod->node, snod->len);
 369                        if (err)
 370                                goto out;
 371
 372                        err = move_node(c, sleb, snod, wbuf);
 373                        if (err)
 374                                goto out;
 375                        moved = 1;
 376                }
 377
 378                /* Move non-data nodes */
 379                list_for_each_entry_safe(snod, tmp, &nondata, list) {
 380                        avail = c->leb_size - wbuf->offs - wbuf->used -
 381                                        ubifs_auth_node_sz(c);
 382                        if (avail < min)
 383                                break;
 384
 385                        if  (snod->len > avail) {
 386                                /*
 387                                 * Keep going only if this is an inode with
 388                                 * some data. Otherwise stop and switch the GC
 389                                 * head. IOW, we assume that data-less inode
 390                                 * nodes and direntry nodes are roughly of the
 391                                 * same size.
 392                                 */
 393                                if (key_type(c, &snod->key) == UBIFS_DENT_KEY ||
 394                                    snod->len == UBIFS_INO_NODE_SZ)
 395                                        break;
 396                                continue;
 397                        }
 398
 399                        err = ubifs_shash_update(c, c->jheads[GCHD].log_hash,
 400                                                 snod->node, snod->len);
 401                        if (err)
 402                                goto out;
 403
 404                        err = move_node(c, sleb, snod, wbuf);
 405                        if (err)
 406                                goto out;
 407                        moved = 1;
 408                }
 409
 410                if (ubifs_authenticated(c) && moved) {
 411                        struct ubifs_auth_node *auth;
 412
 413                        auth = kmalloc(ubifs_auth_node_sz(c), GFP_NOFS);
 414                        if (!auth) {
 415                                err = -ENOMEM;
 416                                goto out;
 417                        }
 418
 419                        err = ubifs_prepare_auth_node(c, auth,
 420                                                c->jheads[GCHD].log_hash);
 421                        if (err) {
 422                                kfree(auth);
 423                                goto out;
 424                        }
 425
 426                        err = ubifs_wbuf_write_nolock(wbuf, auth,
 427                                                      ubifs_auth_node_sz(c));
 428                        if (err) {
 429                                kfree(auth);
 430                                goto out;
 431                        }
 432
 433                        ubifs_add_dirt(c, wbuf->lnum, ubifs_auth_node_sz(c));
 434                }
 435
 436                if (list_empty(&sleb->nodes) && list_empty(&nondata))
 437                        break;
 438
 439                /*
 440                 * Waste the rest of the space in the LEB and switch to the
 441                 * next LEB.
 442                 */
 443                err = switch_gc_head(c);
 444                if (err)
 445                        goto out;
 446        }
 447
 448        return 0;
 449
 450out:
 451        list_splice_tail(&nondata, &sleb->nodes);
 452        return err;
 453}
 454
 455/**
 456 * gc_sync_wbufs - sync write-buffers for GC.
 457 * @c: UBIFS file-system description object
 458 *
 459 * We must guarantee that obsoleting nodes are on flash. Unfortunately they may
 460 * be in a write-buffer instead. That is, a node could be written to a
 461 * write-buffer, obsoleting another node in a LEB that is GC'd. If that LEB is
 462 * erased before the write-buffer is sync'd and then there is an unclean
 463 * unmount, then an existing node is lost. To avoid this, we sync all
 464 * write-buffers.
 465 *
 466 * This function returns %0 on success or a negative error code on failure.
 467 */
 468static int gc_sync_wbufs(struct ubifs_info *c)
 469{
 470        int err, i;
 471
 472        for (i = 0; i < c->jhead_cnt; i++) {
 473                if (i == GCHD)
 474                        continue;
 475                err = ubifs_wbuf_sync(&c->jheads[i].wbuf);
 476                if (err)
 477                        return err;
 478        }
 479        return 0;
 480}
 481
 482/**
 483 * ubifs_garbage_collect_leb - garbage-collect a logical eraseblock.
 484 * @c: UBIFS file-system description object
 485 * @lp: describes the LEB to garbage collect
 486 *
 487 * This function garbage-collects an LEB and returns one of the @LEB_FREED,
 488 * @LEB_RETAINED, etc positive codes in case of success, %-EAGAIN if commit is
 489 * required, and other negative error codes in case of failures.
 490 */
 491int ubifs_garbage_collect_leb(struct ubifs_info *c, struct ubifs_lprops *lp)
 492{
 493        struct ubifs_scan_leb *sleb;
 494        struct ubifs_scan_node *snod;
 495        struct ubifs_wbuf *wbuf = &c->jheads[GCHD].wbuf;
 496        int err = 0, lnum = lp->lnum;
 497
 498        ubifs_assert(c, c->gc_lnum != -1 || wbuf->offs + wbuf->used == 0 ||
 499                     c->need_recovery);
 500        ubifs_assert(c, c->gc_lnum != lnum);
 501        ubifs_assert(c, wbuf->lnum != lnum);
 502
 503        if (lp->free + lp->dirty == c->leb_size) {
 504                /* Special case - a free LEB  */
 505                dbg_gc("LEB %d is free, return it", lp->lnum);
 506                ubifs_assert(c, !(lp->flags & LPROPS_INDEX));
 507
 508                if (lp->free != c->leb_size) {
 509                        /*
 510                         * Write buffers must be sync'd before unmapping
 511                         * freeable LEBs, because one of them may contain data
 512                         * which obsoletes something in 'lp->lnum'.
 513                         */
 514                        err = gc_sync_wbufs(c);
 515                        if (err)
 516                                return err;
 517                        err = ubifs_change_one_lp(c, lp->lnum, c->leb_size,
 518                                                  0, 0, 0, 0);
 519                        if (err)
 520                                return err;
 521                }
 522                err = ubifs_leb_unmap(c, lp->lnum);
 523                if (err)
 524                        return err;
 525
 526                if (c->gc_lnum == -1) {
 527                        c->gc_lnum = lnum;
 528                        return LEB_RETAINED;
 529                }
 530
 531                return LEB_FREED;
 532        }
 533
 534        /*
 535         * We scan the entire LEB even though we only really need to scan up to
 536         * (c->leb_size - lp->free).
 537         */
 538        sleb = ubifs_scan(c, lnum, 0, c->sbuf, 0);
 539        if (IS_ERR(sleb))
 540                return PTR_ERR(sleb);
 541
 542        ubifs_assert(c, !list_empty(&sleb->nodes));
 543        snod = list_entry(sleb->nodes.next, struct ubifs_scan_node, list);
 544
 545        if (snod->type == UBIFS_IDX_NODE) {
 546                struct ubifs_gced_idx_leb *idx_gc;
 547
 548                dbg_gc("indexing LEB %d (free %d, dirty %d)",
 549                       lnum, lp->free, lp->dirty);
 550                list_for_each_entry(snod, &sleb->nodes, list) {
 551                        struct ubifs_idx_node *idx = snod->node;
 552                        int level = le16_to_cpu(idx->level);
 553
 554                        ubifs_assert(c, snod->type == UBIFS_IDX_NODE);
 555                        key_read(c, ubifs_idx_key(c, idx), &snod->key);
 556                        err = ubifs_dirty_idx_node(c, &snod->key, level, lnum,
 557                                                   snod->offs);
 558                        if (err)
 559                                goto out;
 560                }
 561
 562                idx_gc = kmalloc(sizeof(struct ubifs_gced_idx_leb), GFP_NOFS);
 563                if (!idx_gc) {
 564                        err = -ENOMEM;
 565                        goto out;
 566                }
 567
 568                idx_gc->lnum = lnum;
 569                idx_gc->unmap = 0;
 570                list_add(&idx_gc->list, &c->idx_gc);
 571
 572                /*
 573                 * Don't release the LEB until after the next commit, because
 574                 * it may contain data which is needed for recovery. So
 575                 * although we freed this LEB, it will become usable only after
 576                 * the commit.
 577                 */
 578                err = ubifs_change_one_lp(c, lnum, c->leb_size, 0, 0,
 579                                          LPROPS_INDEX, 1);
 580                if (err)
 581                        goto out;
 582                err = LEB_FREED_IDX;
 583        } else {
 584                dbg_gc("data LEB %d (free %d, dirty %d)",
 585                       lnum, lp->free, lp->dirty);
 586
 587                err = move_nodes(c, sleb);
 588                if (err)
 589                        goto out_inc_seq;
 590
 591                err = gc_sync_wbufs(c);
 592                if (err)
 593                        goto out_inc_seq;
 594
 595                err = ubifs_change_one_lp(c, lnum, c->leb_size, 0, 0, 0, 0);
 596                if (err)
 597                        goto out_inc_seq;
 598
 599                /* Allow for races with TNC */
 600                c->gced_lnum = lnum;
 601                smp_wmb();
 602                c->gc_seq += 1;
 603                smp_wmb();
 604
 605                if (c->gc_lnum == -1) {
 606                        c->gc_lnum = lnum;
 607                        err = LEB_RETAINED;
 608                } else {
 609                        err = ubifs_wbuf_sync_nolock(wbuf);
 610                        if (err)
 611                                goto out;
 612
 613                        err = ubifs_leb_unmap(c, lnum);
 614                        if (err)
 615                                goto out;
 616
 617                        err = LEB_FREED;
 618                }
 619        }
 620
 621out:
 622        ubifs_scan_destroy(sleb);
 623        return err;
 624
 625out_inc_seq:
 626        /* We may have moved at least some nodes so allow for races with TNC */
 627        c->gced_lnum = lnum;
 628        smp_wmb();
 629        c->gc_seq += 1;
 630        smp_wmb();
 631        goto out;
 632}
 633
 634/**
 635 * ubifs_garbage_collect - UBIFS garbage collector.
 636 * @c: UBIFS file-system description object
 637 * @anyway: do GC even if there are free LEBs
 638 *
 639 * This function does out-of-place garbage collection. The return codes are:
 640 *   o positive LEB number if the LEB has been freed and may be used;
 641 *   o %-EAGAIN if the caller has to run commit;
 642 *   o %-ENOSPC if GC failed to make any progress;
 643 *   o other negative error codes in case of other errors.
 644 *
 645 * Garbage collector writes data to the journal when GC'ing data LEBs, and just
 646 * marking indexing nodes dirty when GC'ing indexing LEBs. Thus, at some point
 647 * commit may be required. But commit cannot be run from inside GC, because the
 648 * caller might be holding the commit lock, so %-EAGAIN is returned instead;
 649 * And this error code means that the caller has to run commit, and re-run GC
 650 * if there is still no free space.
 651 *
 652 * There are many reasons why this function may return %-EAGAIN:
 653 * o the log is full and there is no space to write an LEB reference for
 654 *   @c->gc_lnum;
 655 * o the journal is too large and exceeds size limitations;
 656 * o GC moved indexing LEBs, but they can be used only after the commit;
 657 * o the shrinker fails to find clean znodes to free and requests the commit;
 658 * o etc.
 659 *
 660 * Note, if the file-system is close to be full, this function may return
 661 * %-EAGAIN infinitely, so the caller has to limit amount of re-invocations of
 662 * the function. E.g., this happens if the limits on the journal size are too
 663 * tough and GC writes too much to the journal before an LEB is freed. This
 664 * might also mean that the journal is too large, and the TNC becomes to big,
 665 * so that the shrinker is constantly called, finds not clean znodes to free,
 666 * and requests commit. Well, this may also happen if the journal is all right,
 667 * but another kernel process consumes too much memory. Anyway, infinite
 668 * %-EAGAIN may happen, but in some extreme/misconfiguration cases.
 669 */
 670int ubifs_garbage_collect(struct ubifs_info *c, int anyway)
 671{
 672        int i, err, ret, min_space = c->dead_wm;
 673        struct ubifs_lprops lp;
 674        struct ubifs_wbuf *wbuf = &c->jheads[GCHD].wbuf;
 675
 676        ubifs_assert_cmt_locked(c);
 677        ubifs_assert(c, !c->ro_media && !c->ro_mount);
 678
 679        if (ubifs_gc_should_commit(c))
 680                return -EAGAIN;
 681
 682        mutex_lock_nested(&wbuf->io_mutex, wbuf->jhead);
 683
 684        if (c->ro_error) {
 685                ret = -EROFS;
 686                goto out_unlock;
 687        }
 688
 689        /* We expect the write-buffer to be empty on entry */
 690        ubifs_assert(c, !wbuf->used);
 691
 692        for (i = 0; ; i++) {
 693                int space_before, space_after;
 694
 695                cond_resched();
 696
 697                /* Give the commit an opportunity to run */
 698                if (ubifs_gc_should_commit(c)) {
 699                        ret = -EAGAIN;
 700                        break;
 701                }
 702
 703                if (i > SOFT_LEBS_LIMIT && !list_empty(&c->idx_gc)) {
 704                        /*
 705                         * We've done enough iterations. Indexing LEBs were
 706                         * moved and will be available after the commit.
 707                         */
 708                        dbg_gc("soft limit, some index LEBs GC'ed, -EAGAIN");
 709                        ubifs_commit_required(c);
 710                        ret = -EAGAIN;
 711                        break;
 712                }
 713
 714                if (i > HARD_LEBS_LIMIT) {
 715                        /*
 716                         * We've moved too many LEBs and have not made
 717                         * progress, give up.
 718                         */
 719                        dbg_gc("hard limit, -ENOSPC");
 720                        ret = -ENOSPC;
 721                        break;
 722                }
 723
 724                /*
 725                 * Empty and freeable LEBs can turn up while we waited for
 726                 * the wbuf lock, or while we have been running GC. In that
 727                 * case, we should just return one of those instead of
 728                 * continuing to GC dirty LEBs. Hence we request
 729                 * 'ubifs_find_dirty_leb()' to return an empty LEB if it can.
 730                 */
 731                ret = ubifs_find_dirty_leb(c, &lp, min_space, anyway ? 0 : 1);
 732                if (ret) {
 733                        if (ret == -ENOSPC)
 734                                dbg_gc("no more dirty LEBs");
 735                        break;
 736                }
 737
 738                dbg_gc("found LEB %d: free %d, dirty %d, sum %d (min. space %d)",
 739                       lp.lnum, lp.free, lp.dirty, lp.free + lp.dirty,
 740                       min_space);
 741
 742                space_before = c->leb_size - wbuf->offs - wbuf->used;
 743                if (wbuf->lnum == -1)
 744                        space_before = 0;
 745
 746                ret = ubifs_garbage_collect_leb(c, &lp);
 747                if (ret < 0) {
 748                        if (ret == -EAGAIN) {
 749                                /*
 750                                 * This is not error, so we have to return the
 751                                 * LEB to lprops. But if 'ubifs_return_leb()'
 752                                 * fails, its failure code is propagated to the
 753                                 * caller instead of the original '-EAGAIN'.
 754                                 */
 755                                err = ubifs_return_leb(c, lp.lnum);
 756                                if (err)
 757                                        ret = err;
 758                                break;
 759                        }
 760                        goto out;
 761                }
 762
 763                if (ret == LEB_FREED) {
 764                        /* An LEB has been freed and is ready for use */
 765                        dbg_gc("LEB %d freed, return", lp.lnum);
 766                        ret = lp.lnum;
 767                        break;
 768                }
 769
 770                if (ret == LEB_FREED_IDX) {
 771                        /*
 772                         * This was an indexing LEB and it cannot be
 773                         * immediately used. And instead of requesting the
 774                         * commit straight away, we try to garbage collect some
 775                         * more.
 776                         */
 777                        dbg_gc("indexing LEB %d freed, continue", lp.lnum);
 778                        continue;
 779                }
 780
 781                ubifs_assert(c, ret == LEB_RETAINED);
 782                space_after = c->leb_size - wbuf->offs - wbuf->used;
 783                dbg_gc("LEB %d retained, freed %d bytes", lp.lnum,
 784                       space_after - space_before);
 785
 786                if (space_after > space_before) {
 787                        /* GC makes progress, keep working */
 788                        min_space >>= 1;
 789                        if (min_space < c->dead_wm)
 790                                min_space = c->dead_wm;
 791                        continue;
 792                }
 793
 794                dbg_gc("did not make progress");
 795
 796                /*
 797                 * GC moved an LEB bud have not done any progress. This means
 798                 * that the previous GC head LEB contained too few free space
 799                 * and the LEB which was GC'ed contained only large nodes which
 800                 * did not fit that space.
 801                 *
 802                 * We can do 2 things:
 803                 * 1. pick another LEB in a hope it'll contain a small node
 804                 *    which will fit the space we have at the end of current GC
 805                 *    head LEB, but there is no guarantee, so we try this out
 806                 *    unless we have already been working for too long;
 807                 * 2. request an LEB with more dirty space, which will force
 808                 *    'ubifs_find_dirty_leb()' to start scanning the lprops
 809                 *    table, instead of just picking one from the heap
 810                 *    (previously it already picked the dirtiest LEB).
 811                 */
 812                if (i < SOFT_LEBS_LIMIT) {
 813                        dbg_gc("try again");
 814                        continue;
 815                }
 816
 817                min_space <<= 1;
 818                if (min_space > c->dark_wm)
 819                        min_space = c->dark_wm;
 820                dbg_gc("set min. space to %d", min_space);
 821        }
 822
 823        if (ret == -ENOSPC && !list_empty(&c->idx_gc)) {
 824                dbg_gc("no space, some index LEBs GC'ed, -EAGAIN");
 825                ubifs_commit_required(c);
 826                ret = -EAGAIN;
 827        }
 828
 829        err = ubifs_wbuf_sync_nolock(wbuf);
 830        if (!err)
 831                err = ubifs_leb_unmap(c, c->gc_lnum);
 832        if (err) {
 833                ret = err;
 834                goto out;
 835        }
 836out_unlock:
 837        mutex_unlock(&wbuf->io_mutex);
 838        return ret;
 839
 840out:
 841        ubifs_assert(c, ret < 0);
 842        ubifs_assert(c, ret != -ENOSPC && ret != -EAGAIN);
 843        ubifs_wbuf_sync_nolock(wbuf);
 844        ubifs_ro_mode(c, ret);
 845        mutex_unlock(&wbuf->io_mutex);
 846        ubifs_return_leb(c, lp.lnum);
 847        return ret;
 848}
 849
 850/**
 851 * ubifs_gc_start_commit - garbage collection at start of commit.
 852 * @c: UBIFS file-system description object
 853 *
 854 * If a LEB has only dirty and free space, then we may safely unmap it and make
 855 * it free.  Note, we cannot do this with indexing LEBs because dirty space may
 856 * correspond index nodes that are required for recovery.  In that case, the
 857 * LEB cannot be unmapped until after the next commit.
 858 *
 859 * This function returns %0 upon success and a negative error code upon failure.
 860 */
 861int ubifs_gc_start_commit(struct ubifs_info *c)
 862{
 863        struct ubifs_gced_idx_leb *idx_gc;
 864        const struct ubifs_lprops *lp;
 865        int err = 0, flags;
 866
 867        ubifs_get_lprops(c);
 868
 869        /*
 870         * Unmap (non-index) freeable LEBs. Note that recovery requires that all
 871         * wbufs are sync'd before this, which is done in 'do_commit()'.
 872         */
 873        while (1) {
 874                lp = ubifs_fast_find_freeable(c);
 875                if (!lp)
 876                        break;
 877                ubifs_assert(c, !(lp->flags & LPROPS_TAKEN));
 878                ubifs_assert(c, !(lp->flags & LPROPS_INDEX));
 879                err = ubifs_leb_unmap(c, lp->lnum);
 880                if (err)
 881                        goto out;
 882                lp = ubifs_change_lp(c, lp, c->leb_size, 0, lp->flags, 0);
 883                if (IS_ERR(lp)) {
 884                        err = PTR_ERR(lp);
 885                        goto out;
 886                }
 887                ubifs_assert(c, !(lp->flags & LPROPS_TAKEN));
 888                ubifs_assert(c, !(lp->flags & LPROPS_INDEX));
 889        }
 890
 891        /* Mark GC'd index LEBs OK to unmap after this commit finishes */
 892        list_for_each_entry(idx_gc, &c->idx_gc, list)
 893                idx_gc->unmap = 1;
 894
 895        /* Record index freeable LEBs for unmapping after commit */
 896        while (1) {
 897                lp = ubifs_fast_find_frdi_idx(c);
 898                if (IS_ERR(lp)) {
 899                        err = PTR_ERR(lp);
 900                        goto out;
 901                }
 902                if (!lp)
 903                        break;
 904                idx_gc = kmalloc(sizeof(struct ubifs_gced_idx_leb), GFP_NOFS);
 905                if (!idx_gc) {
 906                        err = -ENOMEM;
 907                        goto out;
 908                }
 909                ubifs_assert(c, !(lp->flags & LPROPS_TAKEN));
 910                ubifs_assert(c, lp->flags & LPROPS_INDEX);
 911                /* Don't release the LEB until after the next commit */
 912                flags = (lp->flags | LPROPS_TAKEN) ^ LPROPS_INDEX;
 913                lp = ubifs_change_lp(c, lp, c->leb_size, 0, flags, 1);
 914                if (IS_ERR(lp)) {
 915                        err = PTR_ERR(lp);
 916                        kfree(idx_gc);
 917                        goto out;
 918                }
 919                ubifs_assert(c, lp->flags & LPROPS_TAKEN);
 920                ubifs_assert(c, !(lp->flags & LPROPS_INDEX));
 921                idx_gc->lnum = lp->lnum;
 922                idx_gc->unmap = 1;
 923                list_add(&idx_gc->list, &c->idx_gc);
 924        }
 925out:
 926        ubifs_release_lprops(c);
 927        return err;
 928}
 929
 930/**
 931 * ubifs_gc_end_commit - garbage collection at end of commit.
 932 * @c: UBIFS file-system description object
 933 *
 934 * This function completes out-of-place garbage collection of index LEBs.
 935 */
 936int ubifs_gc_end_commit(struct ubifs_info *c)
 937{
 938        struct ubifs_gced_idx_leb *idx_gc, *tmp;
 939        struct ubifs_wbuf *wbuf;
 940        int err = 0;
 941
 942        wbuf = &c->jheads[GCHD].wbuf;
 943        mutex_lock_nested(&wbuf->io_mutex, wbuf->jhead);
 944        list_for_each_entry_safe(idx_gc, tmp, &c->idx_gc, list)
 945                if (idx_gc->unmap) {
 946                        dbg_gc("LEB %d", idx_gc->lnum);
 947                        err = ubifs_leb_unmap(c, idx_gc->lnum);
 948                        if (err)
 949                                goto out;
 950                        err = ubifs_change_one_lp(c, idx_gc->lnum, LPROPS_NC,
 951                                          LPROPS_NC, 0, LPROPS_TAKEN, -1);
 952                        if (err)
 953                                goto out;
 954                        list_del(&idx_gc->list);
 955                        kfree(idx_gc);
 956                }
 957out:
 958        mutex_unlock(&wbuf->io_mutex);
 959        return err;
 960}
 961
 962/**
 963 * ubifs_destroy_idx_gc - destroy idx_gc list.
 964 * @c: UBIFS file-system description object
 965 *
 966 * This function destroys the @c->idx_gc list. It is called when unmounting
 967 * so locks are not needed. Returns zero in case of success and a negative
 968 * error code in case of failure.
 969 */
 970void ubifs_destroy_idx_gc(struct ubifs_info *c)
 971{
 972        while (!list_empty(&c->idx_gc)) {
 973                struct ubifs_gced_idx_leb *idx_gc;
 974
 975                idx_gc = list_entry(c->idx_gc.next, struct ubifs_gced_idx_leb,
 976                                    list);
 977                c->idx_gc_cnt -= 1;
 978                list_del(&idx_gc->list);
 979                kfree(idx_gc);
 980        }
 981}
 982
 983/**
 984 * ubifs_get_idx_gc_leb - get a LEB from GC'd index LEB list.
 985 * @c: UBIFS file-system description object
 986 *
 987 * Called during start commit so locks are not needed.
 988 */
 989int ubifs_get_idx_gc_leb(struct ubifs_info *c)
 990{
 991        struct ubifs_gced_idx_leb *idx_gc;
 992        int lnum;
 993
 994        if (list_empty(&c->idx_gc))
 995                return -ENOSPC;
 996        idx_gc = list_entry(c->idx_gc.next, struct ubifs_gced_idx_leb, list);
 997        lnum = idx_gc->lnum;
 998        /* c->idx_gc_cnt is updated by the caller when lprops are updated */
 999        list_del(&idx_gc->list);
1000        kfree(idx_gc);
1001        return lnum;
1002}
1003
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