linux/fs/ubifs/gc.c
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   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/slab.h>
  57#include <linux/pagemap.h>
  58#include <linux/list_sort.h>
  59#include "ubifs.h"
  60
  61/*
  62 * GC may need to move more than one LEB to make progress. The below constants
  63 * define "soft" and "hard" limits on the number of LEBs the garbage collector
  64 * may move.
  65 */
  66#define SOFT_LEBS_LIMIT 4
  67#define HARD_LEBS_LIMIT 32
  68
  69/**
  70 * switch_gc_head - switch the garbage collection journal head.
  71 * @c: UBIFS file-system description object
  72 * @buf: buffer to write
  73 * @len: length of the buffer to write
  74 * @lnum: LEB number written is returned here
  75 * @offs: offset written is returned here
  76 *
  77 * This function switch the GC head to the next LEB which is reserved in
  78 * @c->gc_lnum. Returns %0 in case of success, %-EAGAIN if commit is required,
  79 * and other negative error code in case of failures.
  80 */
  81static int switch_gc_head(struct ubifs_info *c)
  82{
  83        int err, gc_lnum = c->gc_lnum;
  84        struct ubifs_wbuf *wbuf = &c->jheads[GCHD].wbuf;
  85
  86        ubifs_assert(gc_lnum != -1);
  87        dbg_gc("switch GC head from LEB %d:%d to LEB %d (waste %d bytes)",
  88               wbuf->lnum, wbuf->offs + wbuf->used, gc_lnum,
  89               c->leb_size - wbuf->offs - wbuf->used);
  90
  91        err = ubifs_wbuf_sync_nolock(wbuf);
  92        if (err)
  93                return err;
  94
  95        /*
  96         * The GC write-buffer was synchronized, we may safely unmap
  97         * 'c->gc_lnum'.
  98         */
  99        err = ubifs_leb_unmap(c, gc_lnum);
 100        if (err)
 101                return err;
 102
 103        err = ubifs_wbuf_sync_nolock(wbuf);
 104        if (err)
 105                return err;
 106
 107        err = ubifs_add_bud_to_log(c, GCHD, gc_lnum, 0);
 108        if (err)
 109                return err;
 110
 111        c->gc_lnum = -1;
 112        err = ubifs_wbuf_seek_nolock(wbuf, gc_lnum, 0);
 113        return err;
 114}
 115
 116/**
 117 * data_nodes_cmp - compare 2 data nodes.
 118 * @priv: UBIFS file-system description object
 119 * @a: first data node
 120 * @a: second data node
 121 *
 122 * This function compares data nodes @a and @b. Returns %1 if @a has greater
 123 * inode or block number, and %-1 otherwise.
 124 */
 125static int data_nodes_cmp(void *priv, struct list_head *a, struct list_head *b)
 126{
 127        ino_t inuma, inumb;
 128        struct ubifs_info *c = priv;
 129        struct ubifs_scan_node *sa, *sb;
 130
 131        cond_resched();
 132        if (a == b)
 133                return 0;
 134
 135        sa = list_entry(a, struct ubifs_scan_node, list);
 136        sb = list_entry(b, struct ubifs_scan_node, list);
 137
 138        ubifs_assert(key_type(c, &sa->key) == UBIFS_DATA_KEY);
 139        ubifs_assert(key_type(c, &sb->key) == UBIFS_DATA_KEY);
 140        ubifs_assert(sa->type == UBIFS_DATA_NODE);
 141        ubifs_assert(sb->type == UBIFS_DATA_NODE);
 142
 143        inuma = key_inum(c, &sa->key);
 144        inumb = key_inum(c, &sb->key);
 145
 146        if (inuma == inumb) {
 147                unsigned int blka = key_block(c, &sa->key);
 148                unsigned int blkb = key_block(c, &sb->key);
 149
 150                if (blka <= blkb)
 151                        return -1;
 152        } else if (inuma <= inumb)
 153                return -1;
 154
 155        return 1;
 156}
 157
 158/*
 159 * nondata_nodes_cmp - compare 2 non-data nodes.
 160 * @priv: UBIFS file-system description object
 161 * @a: first node
 162 * @a: second node
 163 *
 164 * This function compares nodes @a and @b. It makes sure that inode nodes go
 165 * first and sorted by length in descending order. Directory entry nodes go
 166 * after inode nodes and are sorted in ascending hash valuer order.
 167 */
 168static int nondata_nodes_cmp(void *priv, struct list_head *a,
 169                             struct list_head *b)
 170{
 171        ino_t inuma, inumb;
 172        struct ubifs_info *c = priv;
 173        struct ubifs_scan_node *sa, *sb;
 174
 175        cond_resched();
 176        if (a == b)
 177                return 0;
 178
 179        sa = list_entry(a, struct ubifs_scan_node, list);
 180        sb = list_entry(b, struct ubifs_scan_node, list);
 181
 182        ubifs_assert(key_type(c, &sa->key) != UBIFS_DATA_KEY &&
 183                     key_type(c, &sb->key) != UBIFS_DATA_KEY);
 184        ubifs_assert(sa->type != UBIFS_DATA_NODE &&
 185                     sb->type != UBIFS_DATA_NODE);
 186
 187        /* Inodes go before directory entries */
 188        if (sa->type == UBIFS_INO_NODE) {
 189                if (sb->type == UBIFS_INO_NODE)
 190                        return sb->len - sa->len;
 191                return -1;
 192        }
 193        if (sb->type == UBIFS_INO_NODE)
 194                return 1;
 195
 196        ubifs_assert(key_type(c, &sa->key) == UBIFS_DENT_KEY ||
 197                     key_type(c, &sa->key) == UBIFS_XENT_KEY);
 198        ubifs_assert(key_type(c, &sb->key) == UBIFS_DENT_KEY ||
 199                     key_type(c, &sb->key) == UBIFS_XENT_KEY);
 200        ubifs_assert(sa->type == UBIFS_DENT_NODE ||
 201                     sa->type == UBIFS_XENT_NODE);
 202        ubifs_assert(sb->type == UBIFS_DENT_NODE ||
 203                     sb->type == UBIFS_XENT_NODE);
 204
 205        inuma = key_inum(c, &sa->key);
 206        inumb = key_inum(c, &sb->key);
 207
 208        if (inuma == inumb) {
 209                uint32_t hasha = key_hash(c, &sa->key);
 210                uint32_t hashb = key_hash(c, &sb->key);
 211
 212                if (hasha <= hashb)
 213                        return -1;
 214        } else if (inuma <= inumb)
 215                return -1;
 216
 217        return 1;
 218}
 219
 220/**
 221 * sort_nodes - sort nodes for GC.
 222 * @c: UBIFS file-system description object
 223 * @sleb: describes nodes to sort and contains the result on exit
 224 * @nondata: contains non-data nodes on exit
 225 * @min: minimum node size is returned here
 226 *
 227 * This function sorts the list of inodes to garbage collect. First of all, it
 228 * kills obsolete nodes and separates data and non-data nodes to the
 229 * @sleb->nodes and @nondata lists correspondingly.
 230 *
 231 * Data nodes are then sorted in block number order - this is important for
 232 * bulk-read; data nodes with lower inode number go before data nodes with
 233 * higher inode number, and data nodes with lower block number go before data
 234 * nodes with higher block number;
 235 *
 236 * Non-data nodes are sorted as follows.
 237 *   o First go inode nodes - they are sorted in descending length order.
 238 *   o Then go directory entry nodes - they are sorted in hash order, which
 239 *     should supposedly optimize 'readdir()'. Direntry nodes with lower parent
 240 *     inode number go before direntry nodes with higher parent inode number,
 241 *     and direntry nodes with lower name hash values go before direntry nodes
 242 *     with higher name hash values.
 243 *
 244 * This function returns zero in case of success and a negative error code in
 245 * case of failure.
 246 */
 247static int sort_nodes(struct ubifs_info *c, struct ubifs_scan_leb *sleb,
 248                      struct list_head *nondata, int *min)
 249{
 250        int err;
 251        struct ubifs_scan_node *snod, *tmp;
 252
 253        *min = INT_MAX;
 254
 255        /* Separate data nodes and non-data nodes */
 256        list_for_each_entry_safe(snod, tmp, &sleb->nodes, list) {
 257                ubifs_assert(snod->type == UBIFS_INO_NODE  ||
 258                             snod->type == UBIFS_DATA_NODE ||
 259                             snod->type == UBIFS_DENT_NODE ||
 260                             snod->type == UBIFS_XENT_NODE ||
 261                             snod->type == UBIFS_TRUN_NODE);
 262
 263                if (snod->type != UBIFS_INO_NODE  &&
 264                    snod->type != UBIFS_DATA_NODE &&
 265                    snod->type != UBIFS_DENT_NODE &&
 266                    snod->type != UBIFS_XENT_NODE) {
 267                        /* Probably truncation node, zap it */
 268                        list_del(&snod->list);
 269                        kfree(snod);
 270                        continue;
 271                }
 272
 273                ubifs_assert(key_type(c, &snod->key) == UBIFS_DATA_KEY ||
 274                             key_type(c, &snod->key) == UBIFS_INO_KEY  ||
 275                             key_type(c, &snod->key) == UBIFS_DENT_KEY ||
 276                             key_type(c, &snod->key) == UBIFS_XENT_KEY);
 277
 278                err = ubifs_tnc_has_node(c, &snod->key, 0, sleb->lnum,
 279                                         snod->offs, 0);
 280                if (err < 0)
 281                        return err;
 282
 283                if (!err) {
 284                        /* The node is obsolete, remove it from the list */
 285                        list_del(&snod->list);
 286                        kfree(snod);
 287                        continue;
 288                }
 289
 290                if (snod->len < *min)
 291                        *min = snod->len;
 292
 293                if (key_type(c, &snod->key) != UBIFS_DATA_KEY)
 294                        list_move_tail(&snod->list, nondata);
 295        }
 296
 297        /* Sort data and non-data nodes */
 298        list_sort(c, &sleb->nodes, &data_nodes_cmp);
 299        list_sort(c, nondata, &nondata_nodes_cmp);
 300
 301        err = dbg_check_data_nodes_order(c, &sleb->nodes);
 302        if (err)
 303                return err;
 304        err = dbg_check_nondata_nodes_order(c, nondata);
 305        if (err)
 306                return err;
 307        return 0;
 308}
 309
 310/**
 311 * move_node - move a node.
 312 * @c: UBIFS file-system description object
 313 * @sleb: describes the LEB to move nodes from
 314 * @snod: the mode to move
 315 * @wbuf: write-buffer to move node to
 316 *
 317 * This function moves node @snod to @wbuf, changes TNC correspondingly, and
 318 * destroys @snod. Returns zero in case of success and a negative error code in
 319 * case of failure.
 320 */
 321static int move_node(struct ubifs_info *c, struct ubifs_scan_leb *sleb,
 322                     struct ubifs_scan_node *snod, struct ubifs_wbuf *wbuf)
 323{
 324        int err, new_lnum = wbuf->lnum, new_offs = wbuf->offs + wbuf->used;
 325
 326        cond_resched();
 327        err = ubifs_wbuf_write_nolock(wbuf, snod->node, snod->len);
 328        if (err)
 329                return err;
 330
 331        err = ubifs_tnc_replace(c, &snod->key, sleb->lnum,
 332                                snod->offs, new_lnum, new_offs,
 333                                snod->len);
 334        list_del(&snod->list);
 335        kfree(snod);
 336        return err;
 337}
 338
 339/**
 340 * move_nodes - move nodes.
 341 * @c: UBIFS file-system description object
 342 * @sleb: describes the LEB to move nodes from
 343 *
 344 * This function moves valid nodes from data LEB described by @sleb to the GC
 345 * journal head. This function returns zero in case of success, %-EAGAIN if
 346 * commit is required, and other negative error codes in case of other
 347 * failures.
 348 */
 349static int move_nodes(struct ubifs_info *c, struct ubifs_scan_leb *sleb)
 350{
 351        int err, min;
 352        LIST_HEAD(nondata);
 353        struct ubifs_wbuf *wbuf = &c->jheads[GCHD].wbuf;
 354
 355        if (wbuf->lnum == -1) {
 356                /*
 357                 * The GC journal head is not set, because it is the first GC
 358                 * invocation since mount.
 359                 */
 360                err = switch_gc_head(c);
 361                if (err)
 362                        return err;
 363        }
 364
 365        err = sort_nodes(c, sleb, &nondata, &min);
 366        if (err)
 367                goto out;
 368
 369        /* Write nodes to their new location. Use the first-fit strategy */
 370        while (1) {
 371                int avail;
 372                struct ubifs_scan_node *snod, *tmp;
 373
 374                /* Move data nodes */
 375                list_for_each_entry_safe(snod, tmp, &sleb->nodes, list) {
 376                        avail = c->leb_size - wbuf->offs - wbuf->used;
 377                        if  (snod->len > avail)
 378                                /*
 379                                 * Do not skip data nodes in order to optimize
 380                                 * bulk-read.
 381                                 */
 382                                break;
 383
 384                        err = move_node(c, sleb, snod, wbuf);
 385                        if (err)
 386                                goto out;
 387                }
 388
 389                /* Move non-data nodes */
 390                list_for_each_entry_safe(snod, tmp, &nondata, list) {
 391                        avail = c->leb_size - wbuf->offs - wbuf->used;
 392                        if (avail < min)
 393                                break;
 394
 395                        if  (snod->len > avail) {
 396                                /*
 397                                 * Keep going only if this is an inode with
 398                                 * some data. Otherwise stop and switch the GC
 399                                 * head. IOW, we assume that data-less inode
 400                                 * nodes and direntry nodes are roughly of the
 401                                 * same size.
 402                                 */
 403                                if (key_type(c, &snod->key) == UBIFS_DENT_KEY ||
 404                                    snod->len == UBIFS_INO_NODE_SZ)
 405                                        break;
 406                                continue;
 407                        }
 408
 409                        err = move_node(c, sleb, snod, wbuf);
 410                        if (err)
 411                                goto out;
 412                }
 413
 414                if (list_empty(&sleb->nodes) && list_empty(&nondata))
 415                        break;
 416
 417                /*
 418                 * Waste the rest of the space in the LEB and switch to the
 419                 * next LEB.
 420                 */
 421                err = switch_gc_head(c);
 422                if (err)
 423                        goto out;
 424        }
 425
 426        return 0;
 427
 428out:
 429        list_splice_tail(&nondata, &sleb->nodes);
 430        return err;
 431}
 432
 433/**
 434 * gc_sync_wbufs - sync write-buffers for GC.
 435 * @c: UBIFS file-system description object
 436 *
 437 * We must guarantee that obsoleting nodes are on flash. Unfortunately they may
 438 * be in a write-buffer instead. That is, a node could be written to a
 439 * write-buffer, obsoleting another node in a LEB that is GC'd. If that LEB is
 440 * erased before the write-buffer is sync'd and then there is an unclean
 441 * unmount, then an existing node is lost. To avoid this, we sync all
 442 * write-buffers.
 443 *
 444 * This function returns %0 on success or a negative error code on failure.
 445 */
 446static int gc_sync_wbufs(struct ubifs_info *c)
 447{
 448        int err, i;
 449
 450        for (i = 0; i < c->jhead_cnt; i++) {
 451                if (i == GCHD)
 452                        continue;
 453                err = ubifs_wbuf_sync(&c->jheads[i].wbuf);
 454                if (err)
 455                        return err;
 456        }
 457        return 0;
 458}
 459
 460/**
 461 * ubifs_garbage_collect_leb - garbage-collect a logical eraseblock.
 462 * @c: UBIFS file-system description object
 463 * @lp: describes the LEB to garbage collect
 464 *
 465 * This function garbage-collects an LEB and returns one of the @LEB_FREED,
 466 * @LEB_RETAINED, etc positive codes in case of success, %-EAGAIN if commit is
 467 * required, and other negative error codes in case of failures.
 468 */
 469int ubifs_garbage_collect_leb(struct ubifs_info *c, struct ubifs_lprops *lp)
 470{
 471        struct ubifs_scan_leb *sleb;
 472        struct ubifs_scan_node *snod;
 473        struct ubifs_wbuf *wbuf = &c->jheads[GCHD].wbuf;
 474        int err = 0, lnum = lp->lnum;
 475
 476        ubifs_assert(c->gc_lnum != -1 || wbuf->offs + wbuf->used == 0 ||
 477                     c->need_recovery);
 478        ubifs_assert(c->gc_lnum != lnum);
 479        ubifs_assert(wbuf->lnum != lnum);
 480
 481        if (lp->free + lp->dirty == c->leb_size) {
 482                /* Special case - a free LEB  */
 483                dbg_gc("LEB %d is free, return it", lp->lnum);
 484                ubifs_assert(!(lp->flags & LPROPS_INDEX));
 485
 486                if (lp->free != c->leb_size) {
 487                        /*
 488                         * Write buffers must be sync'd before unmapping
 489                         * freeable LEBs, because one of them may contain data
 490                         * which obsoletes something in 'lp->pnum'.
 491                         */
 492                        err = gc_sync_wbufs(c);
 493                        if (err)
 494                                return err;
 495                        err = ubifs_change_one_lp(c, lp->lnum, c->leb_size,
 496                                                  0, 0, 0, 0);
 497                        if (err)
 498                                return err;
 499                }
 500                err = ubifs_leb_unmap(c, lp->lnum);
 501                if (err)
 502                        return err;
 503
 504                if (c->gc_lnum == -1) {
 505                        c->gc_lnum = lnum;
 506                        return LEB_RETAINED;
 507                }
 508
 509                return LEB_FREED;
 510        }
 511
 512        /*
 513         * We scan the entire LEB even though we only really need to scan up to
 514         * (c->leb_size - lp->free).
 515         */
 516        sleb = ubifs_scan(c, lnum, 0, c->sbuf, 0);
 517        if (IS_ERR(sleb))
 518                return PTR_ERR(sleb);
 519
 520        ubifs_assert(!list_empty(&sleb->nodes));
 521        snod = list_entry(sleb->nodes.next, struct ubifs_scan_node, list);
 522
 523        if (snod->type == UBIFS_IDX_NODE) {
 524                struct ubifs_gced_idx_leb *idx_gc;
 525
 526                dbg_gc("indexing LEB %d (free %d, dirty %d)",
 527                       lnum, lp->free, lp->dirty);
 528                list_for_each_entry(snod, &sleb->nodes, list) {
 529                        struct ubifs_idx_node *idx = snod->node;
 530                        int level = le16_to_cpu(idx->level);
 531
 532                        ubifs_assert(snod->type == UBIFS_IDX_NODE);
 533                        key_read(c, ubifs_idx_key(c, idx), &snod->key);
 534                        err = ubifs_dirty_idx_node(c, &snod->key, level, lnum,
 535                                                   snod->offs);
 536                        if (err)
 537                                goto out;
 538                }
 539
 540                idx_gc = kmalloc(sizeof(struct ubifs_gced_idx_leb), GFP_NOFS);
 541                if (!idx_gc) {
 542                        err = -ENOMEM;
 543                        goto out;
 544                }
 545
 546                idx_gc->lnum = lnum;
 547                idx_gc->unmap = 0;
 548                list_add(&idx_gc->list, &c->idx_gc);
 549
 550                /*
 551                 * Don't release the LEB until after the next commit, because
 552                 * it may contain data which is needed for recovery. So
 553                 * although we freed this LEB, it will become usable only after
 554                 * the commit.
 555                 */
 556                err = ubifs_change_one_lp(c, lnum, c->leb_size, 0, 0,
 557                                          LPROPS_INDEX, 1);
 558                if (err)
 559                        goto out;
 560                err = LEB_FREED_IDX;
 561        } else {
 562                dbg_gc("data LEB %d (free %d, dirty %d)",
 563                       lnum, lp->free, lp->dirty);
 564
 565                err = move_nodes(c, sleb);
 566                if (err)
 567                        goto out_inc_seq;
 568
 569                err = gc_sync_wbufs(c);
 570                if (err)
 571                        goto out_inc_seq;
 572
 573                err = ubifs_change_one_lp(c, lnum, c->leb_size, 0, 0, 0, 0);
 574                if (err)
 575                        goto out_inc_seq;
 576
 577                /* Allow for races with TNC */
 578                c->gced_lnum = lnum;
 579                smp_wmb();
 580                c->gc_seq += 1;
 581                smp_wmb();
 582
 583                if (c->gc_lnum == -1) {
 584                        c->gc_lnum = lnum;
 585                        err = LEB_RETAINED;
 586                } else {
 587                        err = ubifs_wbuf_sync_nolock(wbuf);
 588                        if (err)
 589                                goto out;
 590
 591                        err = ubifs_leb_unmap(c, lnum);
 592                        if (err)
 593                                goto out;
 594
 595                        err = LEB_FREED;
 596                }
 597        }
 598
 599out:
 600        ubifs_scan_destroy(sleb);
 601        return err;
 602
 603out_inc_seq:
 604        /* We may have moved at least some nodes so allow for races with TNC */
 605        c->gced_lnum = lnum;
 606        smp_wmb();
 607        c->gc_seq += 1;
 608        smp_wmb();
 609        goto out;
 610}
 611
 612/**
 613 * ubifs_garbage_collect - UBIFS garbage collector.
 614 * @c: UBIFS file-system description object
 615 * @anyway: do GC even if there are free LEBs
 616 *
 617 * This function does out-of-place garbage collection. The return codes are:
 618 *   o positive LEB number if the LEB has been freed and may be used;
 619 *   o %-EAGAIN if the caller has to run commit;
 620 *   o %-ENOSPC if GC failed to make any progress;
 621 *   o other negative error codes in case of other errors.
 622 *
 623 * Garbage collector writes data to the journal when GC'ing data LEBs, and just
 624 * marking indexing nodes dirty when GC'ing indexing LEBs. Thus, at some point
 625 * commit may be required. But commit cannot be run from inside GC, because the
 626 * caller might be holding the commit lock, so %-EAGAIN is returned instead;
 627 * And this error code means that the caller has to run commit, and re-run GC
 628 * if there is still no free space.
 629 *
 630 * There are many reasons why this function may return %-EAGAIN:
 631 * o the log is full and there is no space to write an LEB reference for
 632 *   @c->gc_lnum;
 633 * o the journal is too large and exceeds size limitations;
 634 * o GC moved indexing LEBs, but they can be used only after the commit;
 635 * o the shrinker fails to find clean znodes to free and requests the commit;
 636 * o etc.
 637 *
 638 * Note, if the file-system is close to be full, this function may return
 639 * %-EAGAIN infinitely, so the caller has to limit amount of re-invocations of
 640 * the function. E.g., this happens if the limits on the journal size are too
 641 * tough and GC writes too much to the journal before an LEB is freed. This
 642 * might also mean that the journal is too large, and the TNC becomes to big,
 643 * so that the shrinker is constantly called, finds not clean znodes to free,
 644 * and requests commit. Well, this may also happen if the journal is all right,
 645 * but another kernel process consumes too much memory. Anyway, infinite
 646 * %-EAGAIN may happen, but in some extreme/misconfiguration cases.
 647 */
 648int ubifs_garbage_collect(struct ubifs_info *c, int anyway)
 649{
 650        int i, err, ret, min_space = c->dead_wm;
 651        struct ubifs_lprops lp;
 652        struct ubifs_wbuf *wbuf = &c->jheads[GCHD].wbuf;
 653
 654        ubifs_assert_cmt_locked(c);
 655        ubifs_assert(!c->ro_media && !c->ro_mount);
 656
 657        if (ubifs_gc_should_commit(c))
 658                return -EAGAIN;
 659
 660        mutex_lock_nested(&wbuf->io_mutex, wbuf->jhead);
 661
 662        if (c->ro_error) {
 663                ret = -EROFS;
 664                goto out_unlock;
 665        }
 666
 667        /* We expect the write-buffer to be empty on entry */
 668        ubifs_assert(!wbuf->used);
 669
 670        for (i = 0; ; i++) {
 671                int space_before = c->leb_size - wbuf->offs - wbuf->used;
 672                int space_after;
 673
 674                cond_resched();
 675
 676                /* Give the commit an opportunity to run */
 677                if (ubifs_gc_should_commit(c)) {
 678                        ret = -EAGAIN;
 679                        break;
 680                }
 681
 682                if (i > SOFT_LEBS_LIMIT && !list_empty(&c->idx_gc)) {
 683                        /*
 684                         * We've done enough iterations. Indexing LEBs were
 685                         * moved and will be available after the commit.
 686                         */
 687                        dbg_gc("soft limit, some index LEBs GC'ed, -EAGAIN");
 688                        ubifs_commit_required(c);
 689                        ret = -EAGAIN;
 690                        break;
 691                }
 692
 693                if (i > HARD_LEBS_LIMIT) {
 694                        /*
 695                         * We've moved too many LEBs and have not made
 696                         * progress, give up.
 697                         */
 698                        dbg_gc("hard limit, -ENOSPC");
 699                        ret = -ENOSPC;
 700                        break;
 701                }
 702
 703                /*
 704                 * Empty and freeable LEBs can turn up while we waited for
 705                 * the wbuf lock, or while we have been running GC. In that
 706                 * case, we should just return one of those instead of
 707                 * continuing to GC dirty LEBs. Hence we request
 708                 * 'ubifs_find_dirty_leb()' to return an empty LEB if it can.
 709                 */
 710                ret = ubifs_find_dirty_leb(c, &lp, min_space, anyway ? 0 : 1);
 711                if (ret) {
 712                        if (ret == -ENOSPC)
 713                                dbg_gc("no more dirty LEBs");
 714                        break;
 715                }
 716
 717                dbg_gc("found LEB %d: free %d, dirty %d, sum %d "
 718                       "(min. space %d)", lp.lnum, lp.free, lp.dirty,
 719                       lp.free + lp.dirty, min_space);
 720
 721                space_before = c->leb_size - wbuf->offs - wbuf->used;
 722                if (wbuf->lnum == -1)
 723                        space_before = 0;
 724
 725                ret = ubifs_garbage_collect_leb(c, &lp);
 726                if (ret < 0) {
 727                        if (ret == -EAGAIN) {
 728                                /*
 729                                 * This is not error, so we have to return the
 730                                 * LEB to lprops. But if 'ubifs_return_leb()'
 731                                 * fails, its failure code is propagated to the
 732                                 * caller instead of the original '-EAGAIN'.
 733                                 */
 734                                err = ubifs_return_leb(c, lp.lnum);
 735                                if (err)
 736                                        ret = err;
 737                                break;
 738                        }
 739                        goto out;
 740                }
 7c#L687" id="L687"> 612 630wbuf= -wbuf_FREED;
 643/*
 644c-><("found LEB %d: free %rty %d)n>
lp.lnum,  645err = err;
href="+code=lnum" class="sref">lnum,  646 647 648int  649{
wbuf= -wbuf_FREED;
 650        int  651        struct7 652        struct7 653
 654         655         656
c-><("found LEB %d: free % be used onl %d)n>
lp.lnum,  657        if ( 658              7 retu7n - 659
 660        ret =ubifs_assert(!wbuf= -wbuf_FRERETAINED;
 661
space_fter;
c->leb_size - wbuf->offs - wbuf->used;
 662        if (c-><("found LEB %d: free %rty %d)EAGa   o fr>
lp.lnum,  663              7 space_fter;
wbufspace_before = 0;
 664              7 goto76c#L725" id="L725" class="line" name="L667"> 665        }
wbufspace_fter;
 666
 667        dbg_gc_space =  668        err)
_space = dead_wm;
 669
err)
_space = c->dead_wm;
 670        for (<7 href77  break;
 671              7 int 7a href="+code=space_be41" id="L7ugh and GC writesname="L677"> 672              7 int 77c#L703" id="L703" class="line" name="L677"> 673
ret =("found LEB %d: free %dids/ubifske 674              7  675
 676              7 
 677              7 if (77                 * continuing to GC dirty LEBsntly callpreviou/spa s/gc 678              7     77                 * 'ubifs_find_dirty_leb()
a hrwhichowa);

 679              7     77                 */
 680              7 }
 681
 682              7 if (78                                 * caller in* 1. picksumes tooef="fn  idope itn>);
llr. Hea    isma href/gc.c#L696" id="L696" class="line"7name="L687"> 683              7     78                                 */
<
 684 685 686
);
 687              7     78                 * continuing to GC dirty LEBssss' to return an empty LEB if it cstary sC, b7;-EAGAIp" classc#L729" id="L729" class="line" name="L667"> 688              7     78                 * 'ubifs_find_dirty_leb())))t we , 9;-EAGAIN&#steadpick7;-Exingf/spaAGAIs/gpssc#L729" id="L729" class="line" name="L667"> 689              7     78                 */
 690              7     79                                 * LEB to lpggc.c#L734" id="L734" class="line" name="L697"> 691              7 }
i > SOFT_LEBS_LIMIT && ! 692
ret =("found LEB %d: free %bifsaga  /ubifs/gc.c#L714" id="L714" class="line" name="L697"> 693              7 if (7a href="+code=i" classssssssss. Hencee35" id="L735" class="line" name="L697"> 694              7     7    695 696/* Givref">err)
_space =  697 = c->dead_warka>;
 698              7     7   dbg_gc_space = c->dead_warka>;
 699              7     7   ret =("found LEB %d: free %set pan>, lp.);
 700              8     8   break;
 701              8 }
 6308name="L708"> 702
c-><= -ENOSPC)
list_empty(&c->idx_gc)) {
 703              8 /*ret =("found LEB %d: free %ference , -EAGAIN");
 704a href="+code=c" clas(!c);
 705ret = EAGAIN;
 706 697 698              8mment80=ubifs_assert" class="sref"> ub=use_sync_nock;
ub=use_sync_nockc);
 699              8mment809ode=c" class="sr class="sref">li 710              8 ret = ubde=wunmaref="+code=lnum"ef">ubde=wunmars="sref">c);
lp.idx_gc/ubifs/ href="+code=id/ubifs/d" c689" id="L689" class="line"8name="L718"> 711              8 if (8a href="+code=ss="sref">err)
 712              8     8   if (ret = err)
 713              8     8           out;
 714              8     8   break;
 715              8 }
out;
;
 716
;
c-><->io_mutex,  717              8 ret =  718              8     81c#L599" id="L599" class="line"8name="L718"> 719              8     8  out;
 720
wbuf= - 721              8 wbuf= -ENOSPC)
wbuf= -ENOSPC) {
 722              8 if (8a href="+code=_leb" class="sref">ub=use_sync_nock;
ub=use_sync_nockc);
 723              8     8   ububifsda>);
ububifsdas="sref">c);
lp. 724
;
c-><->io_mutex,  725              8 ubufs_return_leb(c, lp.lnum);
 726              8 if (8a href="+code=fs/ubifsref">ret =  727              8     8   if 41" id="L7ugh and GC write8name="L728"> 728              8     82c#L599" id="L599" class="line"8name="L728"> 729 730 731 732 733 734              8     83 * and requests commit. Well,  735              8     83 * but another kernel process correspoat 9;&quoef="fsntly ars/ubifclasGs="srecove
 736              8     83 * %-EAGAIN may happen, bua hr., becaus; 737              8     83 */
 738              8     83                 * 'ubifhave tofun:upoa to the 739              8     83                 */
 740              8 }
sa>((ubifs_wbinfo_leb(c);
 7c#L687" id="L687"> 6828span c83" id="L683" class="line"8/a>ubifs_wbgced_ubifbage_collect_leb(c);
)) {
 643ubifs_lprops c);
 644s lp.  645 646a>( c);
 647 648int 
 649{
 650        int );
dausbifssss/g,rwhicho toexingins'do=="+codLEB if gc.c#L686" id="L686" class="line"8name="L658"> 651        struct8 652        struct8 653
/*ret = href="fs/ubifs/gc.c#L6d_dirty_leb" class="sref"asteturn hile we  c);
 654        err)
IS_ERRref="fs/ubifs/gIS_ERRs="sref">c);
 655        err = c);
 656
out;
 657        if ( 658              8 retu8n -lia href="fs/ubifs/gc.c#L71" id="L7ugh and GC write8name="L648"> 659
 660        ret =ubifs_assert(!c);
io_mflags wbufLPROPS_TAKE {
 661
ubifs_assert(!c);
io_mflags wbufLPROPS_INDEDX;
 662        if (c->< ubde=wunmaref="+code=lnum"ef">ubde=wunmars="sref">c);
lp.io_m);
 663              8 err)
 664              8 goto86  out;
 665        }
ret = href="fs/ubifs/gc.c#L6d_dirty_leb" class="srefchange_ href="fs/ubifs/g="srefchange_ hs="sref">c);
lp.lp.idx_gcsize - lp.io_mflags  666
err)
IS_ERRref="fs/ubifs/gIS_ERRs="sref">c);
 667        dbg_gc c);
 668        out;
 669
 670        for (<8 href87  break;
ubifs_assert(!c);
io_mflags wbufLPROPS_TAKE {
 671              8 int 8a href="+code=space_be" class="sref">ubifs_assert(!c);
io_mflags wbufLPROPS_INDEDX;
 672              8 int 87 href="+code=41" id="L7ugh and GC write8name="L648"> 673
 674              8 );
dAIN" 675
(&c);
)) {
lp);
idx_gc)) {
lp.(& 676              8 /* Givref">err)
)) {
used;nmaref="+code=lnum"enmars="s #L608" id="L608" class="line"8name="L668"> 677              8 if (87     1" id="L7ugh and GC write8name="L668"> 678              8     87=ubifs_assert"an>
 679              8     87          gotGC. In(13683" id="L683" class="line"8name="L688"> 680              8 }
 href="fs/ubifs/gc.c#L6d_dirty_leb" class="sref"asteturn hidi_ubi c);
 681
i > IS_ERRref="fs/ubifs/gIS_ERRs="sref">c);
 682              8 if (88  if (ret = c);
 683              8     88 href="+code=i" classssssssssass="sref">out;
 684 685lia href="fs/ubifs/gc.c#L71" id="L7ugh and GC write8name="L688"> 686 687              8     88f="+code=dbg_gc" class="sref">dbg_gc)) {
ubifs_wbgced_ubifbage_collect_leb(lp. 688              8     88 -li)) {
 689              8     88  break;
ret = ENOSPC 690              8     89  break;
out;
 691              8 }
 692
ubifs_assert(!c);
io_mflags wbufLPROPS_TAKE {
 693              8 if (8a href="+code=i" class" class="sref">ubifs_assert(!c);
io_mflags wbufLPROPS_INDEDX;
 694              8     8   
 695ret =flags i > a href="fs/ubifs/gc.c#Lx" class="sref">io_mflags wbufLPROPS_TAKE {
wbufLPROPS_INDEDX;
 696/* Givref">err)
 href="fs/ubifs/gc.c#L6d_dirty_leb" class="srefchange_ href="fs/ubifs/g="srefchange_ hs="sref">c);
lp.lp.idx_gcsize - lp.  697c);
 698              8     8   dbg_gc c);
 699              8     8   dbg_gck + c);
)) {
 700              9     90  break;
out;
 701              9 }
 702
ubifs_assert(!c);
io_mflags wbufLPROPS_TAKE {
 693              9 /*ret =ubifs_assert(!c);
io_mflags wbufLPROPS_INDEDX;
 704)) {
used == -1)
lp.io_m);
 695ret =)) {
used;nmaref="+code=lnum"enmars="s #L608" id="L608" class="line"9name="L709"> 706/* Givref">err)
 "+coads(!lp);
<)) {
used "+ca>(&lp);
idx_gc)) {
 697 698              9mment90=ubifsref">out;
 699              9mment909ode=c" classpref">ret =ubifs_release_lprops c);
 710              9 ret = 711              9 if (9 8 if 41" id="L7ugh and GC write9="line"8n9.c#L714" id="L714" class="line" name2( 9            8     8     9     91                * If a be u id="L729" class="line"8name="L738"9 714 9            8     8   br9ak;
<91sts commit. Well,  9            8 }

9a href="fs/u8ifs/g816ubi9s_ass91AIN may happen, bua hr., beca="L686" class="line"8name="L718"9 697              8     81c#L599" id91     * 'ubifhave tofun: 9            8     8  sa>((ubifs_wbinfo_leb(c);

9a href="fs/u8ifs/g82=mut9x_loc9_neste" class="line"8name="L698"9 721 9            8 ubifs_wbgced_ubifbage_collect_leb(c);
)) {
 722 9            8 if (8a hre9="+co92=_wbuf" class="sref">ubifs_wbgced_ubifbag="+code=io_mutex" cbifbag="+c/a>);
)) {
 713 9            8     8   s lp 714 9a href="fs/u8ifs/g82=ubi9s_ass92L725" class="line" name="L677"9 725 9            8 ubufs_re="+code=io_mutex" class="srp);
idx_gc)) {
);
 716
9            8 if (8a hre9="+co92t" class="sref">;
;
lp);
<)) {
io_mutex, io_mutex,  727 9            8     8   if941" i927" class="sref">cc);
)) {
idx_gc)) {
lp.(& 9            8     82c#L599" id92code=EAGA="sr class="sref> =)) {
used;nmaref="+code=lnum"enmars="s #L608" id="83" class="line"8name="L698"9 729<9pan class="c8mment8>    9     92code=ret"gc" class="sref">dbg_gck + "found LEB %d: free %rty %d)EAGa   o fr="sref">lp.);href="fs/ubifs/gc.class="sref">used == -1)
lp 730<9pan class="c8mment8>    9     93href="fs/ubifs/gcpan>
ubde=wunmars="sref">c);
lp.used == -1)
lp 721 9pan class="c8mment8>    9     93s/gc.c#L641" id="L7ug class="sref> =)) {
<9pan class="c8mment8>    9     93f="+code=ret" clasref">ret;
 733<9pan class="c8mment8>    9     93=i" classssssssssass="sref">o=gc conubifs/g="srefchange_ hs="sref">conubifa>);
lp.used == -1)
lp. 714 9            8     83 * a9d req93code=c" class="srass="sref">ossssssass="sref">o=gc  9            8     83 * b9t ano93code=err" class="sref">err =)) {

9            8     83 * &937;-E93      ;
 727 9            8     83 */<9span>93code=dbg_gc" class="sref">dbg_gc lp);
<)) {
used "+ca>(&0" class="line"8name="L688"9 728 9            8     83    9     93code=dbg_gc" class="sref">dbg_gc c);
)) {
 739 9            8     83    9     93to  9            8 }
 7c#L687"9id="L687"> 6828span 983" i94cested" class="subifs_asserta>;
c-><->io_mutex, ret = 643<9pan class="c8mment84   9pan class="c8mment84  <9pan class="c8mment84c#L696" id94er kernel process correspoa id="L729" class="line"8name="L738"9 646<9pan class="c8mment846ubi9s_ass94AIN may happen, bua hr., becau_ hs="de<9pan class="c8mment84    91" id94a href="fs/ubifs/c.c#L686" idsle-system descripi9t  9i9" id= ="srd It'called wafim">co"fs/ng="L686" class="line"8name="L718"9 650 9      int  9      struct8
9a href="fs/u8ifs/g85clas9="com9ent">/void="srPTR_ERRref="maref=deubifs_wbinfo_leb(c);
 9       9      list_empty(&c->idx_gc)) {

9a href="fs/u8ifs/g85    9     9       ubifs_wbgced_ubifbage_collect_leb(c);
)) {
 9      if ( 9            8 retu8n -c);
)) {
idx_gc)) {
ubifs_wbgced_ubifbage_collect_leb(c)> class="line"9name="L709"> 659
9a href="fs/u8ifs/g85  br9ak;
<9 href="fs/ubifs/gc.c#L680" id=s="sref">dbg_gc 0" class="line"8name="L688"9 660 9      ret =ubifs_asserte=idx_gc" class="sref">idx_gc)) {
 661
9a href="fs/u8ifs/g86f="+9ode=s9ace_before" class="sref">ubifs_assertsss="delf=" "+coadsclassss="delf">lp);
<)) {
used "+ca>(&0" class="line"8name="L688"9 662 9      if (c->< c);
)) {
 663 9            8  9            8 goto86   9      }

9a href="fs/u8ifs/g86    9     96AIN may happen, bua hr., be id="L729" class="line"8name="L738"9 667 9       9      
9a href="fs/u8ifs/g86    9     96     */
 9      for (<8 href87  br9ak;
<97                     * L*e b*sCalled durty ifs/gc. codes /gtsref);
daupasGneeded.="L686" class="line"8name="L718"9 661
9            8 int 8a hre9="+co97                     * fggc.*d="L734" class="line"8name="L698"9 672 9            8 int 87 hre9="+co9e=41" sref">sa>(ubifs_wbinfo_leb(c);

9a href="fs/u8ifs/g87f="+91" id9"L7ugh" class="line"8name="L708"9 674 9            8 ubifs_wbgced_ubifbage_collect_leb(c);
)) {

9a href="fs/u8ifs/g87f="+9ode=r9t"_leb" class=sref">sa>( 676 9            8 / class="line"9n5me="L709"> 667 9            8 if (87    91" id97code=dbg_gc" sref> =)) {
c->idx_gc)) {
 668 9            8     87=ubi9s_ass97code=EAGA="sr class=">ret)
 669
9            8     87    9     97spref">ret =ubifs_releashref="fs/ubifs/gc.c89" id="L689a>.c);
)) {
idx_gc)) {
ubifs_wbgced_ubifbage_collect_leb(c)>g_gc 0" class="line"8name="L688"9 680 9            8 }
sa>(used == -1)
lp
9a href="fs/u8ifs/g88ref=9fs/ub9fs/gc.c#L6="sr="fs/ubifs/g Donn>);
gnrecef">i9" id=_cn='updated byifs/tcaller wafimf">c 9            8 if (88  if9(ubifs_assertsss="delf=" "+coadsclassss="delf">lp);
<)) {
used "+ca>(&0" class="line"8name="L688"9 683 9            8     88 hre9="+co9e=i" classsssst;< c);
)) {
 684<9pan class="c8mment88  ret =lp
9pan class="c8mment88  <9pan class="c8mment88    9     9      
exr.c8mux.no kKrtly hosted byiand GC wrhttp://www.redpill-c8mpro.nosrRedpill L8mpro AS">c<,tprovider of L8muxps" cultommit s/gperabc#Ls services since 1995.