linux/fs/ubifs/tnc_commit.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/* This file implements TNC functions for committing */
  12
  13#include <linux/random.h>
  14#include "ubifs.h"
  15
  16/**
  17 * make_idx_node - make an index node for fill-the-gaps method of TNC commit.
  18 * @c: UBIFS file-system description object
  19 * @idx: buffer in which to place new index node
  20 * @znode: znode from which to make new index node
  21 * @lnum: LEB number where new index node will be written
  22 * @offs: offset where new index node will be written
  23 * @len: length of new index node
  24 */
  25static int make_idx_node(struct ubifs_info *c, struct ubifs_idx_node *idx,
  26                         struct ubifs_znode *znode, int lnum, int offs, int len)
  27{
  28        struct ubifs_znode *zp;
  29        u8 hash[UBIFS_HASH_ARR_SZ];
  30        int i, err;
  31
  32        /* Make index node */
  33        idx->ch.node_type = UBIFS_IDX_NODE;
  34        idx->child_cnt = cpu_to_le16(znode->child_cnt);
  35        idx->level = cpu_to_le16(znode->level);
  36        for (i = 0; i < znode->child_cnt; i++) {
  37                struct ubifs_branch *br = ubifs_idx_branch(c, idx, i);
  38                struct ubifs_zbranch *zbr = &znode->zbranch[i];
  39
  40                key_write_idx(c, &zbr->key, &br->key);
  41                br->lnum = cpu_to_le32(zbr->lnum);
  42                br->offs = cpu_to_le32(zbr->offs);
  43                br->len = cpu_to_le32(zbr->len);
  44                ubifs_copy_hash(c, zbr->hash, ubifs_branch_hash(c, br));
  45                if (!zbr->lnum || !zbr->len) {
  46                        ubifs_err(c, "bad ref in znode");
  47                        ubifs_dump_znode(c, znode);
  48                        if (zbr->znode)
  49                                ubifs_dump_znode(c, zbr->znode);
  50
  51                        return -EINVAL;
  52                }
  53        }
  54        ubifs_prepare_node(c, idx, len, 0);
  55        ubifs_node_calc_hash(c, idx, hash);
  56
  57        znode->lnum = lnum;
  58        znode->offs = offs;
  59        znode->len = len;
  60
  61        err = insert_old_idx_znode(c, znode);
  62
  63        /* Update the parent */
  64        zp = znode->parent;
  65        if (zp) {
  66                struct ubifs_zbranch *zbr;
  67
  68                zbr = &zp->zbranch[znode->iip];
  69                zbr->lnum = lnum;
  70                zbr->offs = offs;
  71                zbr->len = len;
  72                ubifs_copy_hash(c, hash, zbr->hash);
  73        } else {
  74                c->zroot.lnum = lnum;
  75                c->zroot.offs = offs;
  76                c->zroot.len = len;
  77                ubifs_copy_hash(c, hash, c->zroot.hash);
  78        }
  79        c->calc_idx_sz += ALIGN(len, 8);
  80
  81        atomic_long_dec(&c->dirty_zn_cnt);
  82
  83        ubifs_assert(c, ubifs_zn_dirty(znode));
  84        ubifs_assert(c, ubifs_zn_cow(znode));
  85
  86        /*
  87         * Note, unlike 'write_index()' we do not add memory barriers here
  88         * because this function is called with @c->tnc_mutex locked.
  89         */
  90        __clear_bit(DIRTY_ZNODE, &znode->flags);
  91        __clear_bit(COW_ZNODE, &znode->flags);
  92
  93        return err;
  94}
  95
  96/**
  97 * fill_gap - make index nodes in gaps in dirty index LEBs.
  98 * @c: UBIFS file-system description object
  99 * @lnum: LEB number that gap appears in
 100 * @gap_start: offset of start of gap
 101 * @gap_end: offset of end of gap
 102 * @dirt: adds dirty space to this
 103 *
 104 * This function returns the number of index nodes written into the gap.
 105 */
 106static int fill_gap(struct ubifs_info *c, int lnum, int gap_start, int gap_end,
 107                    int *dirt)
 108{
 109        int len, gap_remains, gap_pos, written, pad_len;
 110
 111        ubifs_assert(c, (gap_start & 7) == 0);
 112        ubifs_assert(c, (gap_end & 7) == 0);
 113        ubifs_assert(c, gap_end >= gap_start);
 114
 115        gap_remains = gap_end - gap_start;
 116        if (!gap_remains)
 117                return 0;
 118        gap_pos = gap_start;
 119        written = 0;
 120        while (c->enext) {
 121                len = ubifs_idx_node_sz(c, c->enext->child_cnt);
 122                if (len < gap_remains) {
 123                        struct ubifs_znode *znode = c->enext;
 124                        const int alen = ALIGN(len, 8);
 125                        int err;
 126
 127                        ubifs_assert(c, alen <= gap_remains);
 128                        err = make_idx_node(c, c->ileb_buf + gap_pos, znode,
 129                                            lnum, gap_pos, len);
 130                        if (err)
 131                                return err;
 132                        gap_remains -= alen;
 133                        gap_pos += alen;
 134                        c->enext = znode->cnext;
 135                        if (c->enext == c->cnext)
 136                                c->enext = NULL;
 137                        written += 1;
 138                } else
 139                        break;
 140        }
 141        if (gap_end == c->leb_size) {
 142                c->ileb_len = ALIGN(gap_pos, c->min_io_size);
 143                /* Pad to end of min_io_size */
 144                pad_len = c->ileb_len - gap_pos;
 145        } else
 146                /* Pad to end of gap */
 147                pad_len = gap_remains;
 148        dbg_gc("LEB %d:%d to %d len %d nodes written %d wasted bytes %d",
 149               lnum, gap_start, gap_end, gap_end - gap_start, written, pad_len);
 150        ubifs_pad(c, c->ileb_buf + gap_pos, pad_len);
 151        *dirt += pad_len;
 152        return written;
 153}
 154
 155/**
 156 * find_old_idx - find an index node obsoleted since the last commit start.
 157 * @c: UBIFS file-system description object
 158 * @lnum: LEB number of obsoleted index node
 159 * @offs: offset of obsoleted index node
 160 *
 161 * Returns %1 if found and %0 otherwise.
 162 */
 163static int find_old_idx(struct ubifs_info *c, int lnum, int offs)
 164{
 165        struct ubifs_old_idx *o;
 166        struct rb_node *p;
 167
 168        p = c->old_idx.rb_node;
 169        while (p) {
 170                o = rb_entry(p, struct ubifs_old_idx, rb);
 171                if (lnum < o->lnum)
 172                        p = p->rb_left;
 173                else if (lnum > o->lnum)
 174                        p = p->rb_right;
 175                else if (offs < o->offs)
 176                        p = p->rb_left;
 177                else if (offs > o->offs)
 178                        p = p->rb_right;
 179                else
 180                        return 1;
 181        }
 182        return 0;
 183}
 184
 185/**
 186 * is_idx_node_in_use - determine if an index node can be overwritten.
 187 * @c: UBIFS file-system description object
 188 * @key: key of index node
 189 * @level: index node level
 190 * @lnum: LEB number of index node
 191 * @offs: offset of index node
 192 *
 193 * If @key / @lnum / @offs identify an index node that was not part of the old
 194 * index, then this function returns %0 (obsolete).  Else if the index node was
 195 * part of the old index but is now dirty %1 is returned, else if it is clean %2
 196 * is returned. A negative error code is returned on failure.
 197 */
 198static int is_idx_node_in_use(struct ubifs_info *c, union ubifs_key *key,
 199                              int level, int lnum, int offs)
 200{
 201        int ret;
 202
 203        ret = is_idx_node_in_tnc(c, key, level, lnum, offs);
 204        if (ret < 0)
 205                return ret; /* Error code */
 206        if (ret == 0)
 207                if (find_old_idx(c, lnum, offs))
 208                        return 1;
 209        return ret;
 210}
 211
 212/**
 213 * layout_leb_in_gaps - layout index nodes using in-the-gaps method.
 214 * @c: UBIFS file-system description object
 215 * @p: return LEB number in @c->gap_lebs[p]
 216 *
 217 * This function lays out new index nodes for dirty znodes using in-the-gaps
 218 * method of TNC commit.
 219 * This function merely puts the next znode into the next gap, making no attempt
 220 * to try to maximise the number of znodes that fit.
 221 * This function returns the number of index nodes written into the gaps, or a
 222 * negative error code on failure.
 223 */
 224static int layout_leb_in_gaps(struct ubifs_info *c, int p)
 225{
 226        struct ubifs_scan_leb *sleb;
 227        struct ubifs_scan_node *snod;
 228        int lnum, dirt = 0, gap_start, gap_end, err, written, tot_written;
 229
 230        tot_written = 0;
 231        /* Get an index LEB with lots of obsolete index nodes */
 232        lnum = ubifs_find_dirty_idx_leb(c);
 233        if (lnum < 0)
 234                /*
 235                 * There also may be dirt in the index head that could be
 236                 * filled, however we do not check there at present.
 237                 */
 238                return lnum; /* Error code */
 239        c->gap_lebs[p] = lnum;
 240        dbg_gc("LEB %d", lnum);
 241        /*
 242         * Scan the index LEB.  We use the generic scan for this even though
 243         * it is more comprehensive and less efficient than is needed for this
 244         * purpose.
 245         */
 246        sleb = ubifs_scan(c, lnum, 0, c->ileb_buf, 0);
 247        c->ileb_len = 0;
 248        if (IS_ERR(sleb))
 249                return PTR_ERR(sleb);
 250        gap_start = 0;
 251        list_for_each_entry(snod, &sleb->nodes, list) {
 252                struct ubifs_idx_node *idx;
 253                int in_use, level;
 254
 255                ubifs_assert(c, snod->type == UBIFS_IDX_NODE);
 256                idx = snod->node;
 257                key_read(c, ubifs_idx_key(c, idx), &snod->key);
 258                level = le16_to_cpu(idx->level);
 259                /* Determine if the index node is in use (not obsolete) */
 260                in_use = is_idx_node_in_use(c, &snod->key, level, lnum,
 261                                            snod->offs);
 262                if (in_use < 0) {
 263                        ubifs_scan_destroy(sleb);
 264                        return in_use; /* Error code */
 265                }
 266                if (in_use) {
 267                        if (in_use == 1)
 268                                dirt += ALIGN(snod->len, 8);
 269                        /*
 270                         * The obsolete index nodes form gaps that can be
 271                         * overwritten.  This gap has ended because we have
 272                         * found an index node that is still in use
 273                         * i.e. not obsolete
 274                         */
 275                        gap_end = snod->offs;
 276                        /* Try to fill gap */
 277                        written = fill_gap(c, lnum, gap_start, gap_end, &dirt);
 278                        if (written < 0) {
 279                                ubifs_scan_destroy(sleb);
 280                                return written; /* Error code */
 281                        }
 282                        tot_written += written;
 283                        gap_start = ALIGN(snod->offs + snod->len, 8);
 284                }
 285        }
 286        ubifs_scan_destroy(sleb);
 287        c->ileb_len = c->leb_size;
 288        gap_end = c->leb_size;
 289        /* Try to fill gap */
 290        written = fill_gap(c, lnum, gap_start, gap_end, &dirt);
 291        if (written < 0)
 292                return written; /* Error code */
 293        tot_written += written;
 294        if (tot_written == 0) {
 295                struct ubifs_lprops lp;
 296
 297                dbg_gc("LEB %d wrote %d index nodes", lnum, tot_written);
 298                err = ubifs_read_one_lp(c, lnum, &lp);
 299                if (err)
 300                        return err;
 301                if (lp.free == c->leb_size) {
 302                        /*
 303                         * We must have snatched this LEB from the idx_gc list
 304                         * so we need to correct the free and dirty space.
 305                         */
 306                        err = ubifs_change_one_lp(c, lnum,
 307                                                  c->leb_size - c->ileb_len,
 308                                                  dirt, 0, 0, 0);
 309                        if (err)
 310                                return err;
 311                }
 312                return 0;
 313        }
 314        err = ubifs_change_one_lp(c, lnum, c->leb_size - c->ileb_len, dirt,
 315                                  0, 0, 0);
 316        if (err)
 317                return err;
 318        err = ubifs_leb_change(c, lnum, c->ileb_buf, c->ileb_len);
 319        if (err)
 320                return err;
 321        dbg_gc("LEB %d wrote %d index nodes", lnum, tot_written);
 322        return tot_written;
 323}
 324
 325/**
 326 * get_leb_cnt - calculate the number of empty LEBs needed to commit.
 327 * @c: UBIFS file-system description object
 328 * @cnt: number of znodes to commit
 329 *
 330 * This function returns the number of empty LEBs needed to commit @cnt znodes
 331 * to the current index head.  The number is not exact and may be more than
 332 * needed.
 333 */
 334static int get_leb_cnt(struct ubifs_info *c, int cnt)
 335{
 336        int d;
 337
 338        /* Assume maximum index node size (i.e. overestimate space needed) */
 339        cnt -= (c->leb_size - c->ihead_offs) / c->max_idx_node_sz;
 340        if (cnt < 0)
 341                cnt = 0;
 342        d = c->leb_size / c->max_idx_node_sz;
 343        return DIV_ROUND_UP(cnt, d);
 344}
 345
 346/**
 347 * layout_in_gaps - in-the-gaps method of committing TNC.
 348 * @c: UBIFS file-system description object
 349 * @cnt: number of dirty znodes to commit.
 350 *
 351 * This function lays out new index nodes for dirty znodes using in-the-gaps
 352 * method of TNC commit.
 353 *
 354 * This function returns %0 on success and a negative error code on failure.
 355 */
 356static int layout_in_gaps(struct ubifs_info *c, int cnt)
 357{
 358        int err, leb_needed_cnt, written, p = 0, old_idx_lebs, *gap_lebs;
 359
 360        dbg_gc("%d znodes to write", cnt);
 361
 362        c->gap_lebs = kmalloc_array(c->lst.idx_lebs + 1, sizeof(int),
 363                                    GFP_NOFS);
 364        if (!c->gap_lebs)
 365                return -ENOMEM;
 366
 367        old_idx_lebs = c->lst.idx_lebs;
 368        do {
 369                ubifs_assert(c, p < c->lst.idx_lebs);
 370                written = layout_leb_in_gaps(c, p);
 371                if (written < 0) {
 372                        err = written;
 373                        if (err != -ENOSPC) {
 374                                kfree(c->gap_lebs);
 375                                c->gap_lebs = NULL;
 376                                return err;
 377                        }
 378                        if (!dbg_is_chk_index(c)) {
 379                                /*
 380                                 * Do not print scary warnings if the debugging
 381                                 * option which forces in-the-gaps is enabled.
 382                                 */
 383                                ubifs_warn(c, "out of space");
 384                                ubifs_dump_budg(c, &c->bi);
 385                                ubifs_dump_lprops(c);
 386                        }
 387                        /* Try to commit anyway */
 388                        break;
 389                }
 390                p++;
 391                cnt -= written;
 392                leb_needed_cnt = get_leb_cnt(c, cnt);
 393                dbg_gc("%d znodes remaining, need %d LEBs, have %d", cnt,
 394                       leb_needed_cnt, c->ileb_cnt);
 395                /*
 396                 * Dynamically change the size of @c->gap_lebs to prevent
 397                 * oob, because @c->lst.idx_lebs could be increased by
 398                 * function @get_idx_gc_leb (called by layout_leb_in_gaps->
 399                 * ubifs_find_dirty_idx_leb) during loop. Only enlarge
 400                 * @c->gap_lebs when needed.
 401                 *
 402                 */
 403                if (leb_needed_cnt > c->ileb_cnt && p >= old_idx_lebs &&
 404                    old_idx_lebs < c->lst.idx_lebs) {
 405                        old_idx_lebs = c->lst.idx_lebs;
 406                        gap_lebs = krealloc(c->gap_lebs, sizeof(int) *
 407                                               (old_idx_lebs + 1), GFP_NOFS);
 408                        if (!gap_lebs) {
 409                                kfree(c->gap_lebs);
 410                                c->gap_lebs = NULL;
 411                                return -ENOMEM;
 412                        }
 413                        c->gap_lebs = gap_lebs;
 414                }
 415        } while (leb_needed_cnt > c->ileb_cnt);
 416
 417        c->gap_lebs[p] = -1;
 418        return 0;
 419}
 420
 421/**
 422 * layout_in_empty_space - layout index nodes in empty space.
 423 * @c: UBIFS file-system description object
 424 *
 425 * This function lays out new index nodes for dirty znodes using empty LEBs.
 426 *
 427 * This function returns %0 on success and a negative error code on failure.
 428 */
 429static int layout_in_empty_space(struct ubifs_info *c)
 430{
 431        struct ubifs_znode *znode, *cnext, *zp;
 432        int lnum, offs, len, next_len, buf_len, buf_offs, used, avail;
 433        int wlen, blen, err;
 434
 435        cnext = c->enext;
 436        if (!cnext)
 437                return 0;
 438
 439        lnum = c->ihead_lnum;
 440        buf_offs = c->ihead_offs;
 441
 442        buf_len = ubifs_idx_node_sz(c, c->fanout);
 443        buf_len = ALIGN(buf_len, c->min_io_size);
 444        used = 0;
 445        avail = buf_len;
 446
 447        /* Ensure there is enough room for first write */
 448        next_len = ubifs_idx_node_sz(c, cnext->child_cnt);
 449        if (buf_offs + next_len > c->leb_size)
 450                lnum = -1;
 451
 452        while (1) {
 453                znode = cnext;
 454
 455                len = ubifs_idx_node_sz(c, znode->child_cnt);
 456
 457                /* Determine the index node position */
 458                if (lnum == -1) {
 459                        if (c->ileb_nxt >= c->ileb_cnt) {
 460                                ubifs_err(c, "out of space");
 461                                return -ENOSPC;
 462                        }
 463                        lnum = c->ilebs[c->ileb_nxt++];
 464                        buf_offs = 0;
 465                        used = 0;
 466                        avail = buf_len;
 467                }
 468
 469                offs = buf_offs + used;
 470
 471                znode->lnum = lnum;
 472                znode->offs = offs;
 473                znode->len = len;
 474
 475                /* Update the parent */
 476                zp = znode->parent;
 477                if (zp) {
 478                        struct ubifs_zbranch *zbr;
 479                        int i;
 480
 481                        i = znode->iip;
 482                        zbr = &zp->zbranch[i];
 483                        zbr->lnum = lnum;
 484                        zbr->offs = offs;
 485                        zbr->len = len;
 486                } else {
 487                        c->zroot.lnum = lnum;
 488                        c->zroot.offs = offs;
 489                        c->zroot.len = len;
 490                }
 491                c->calc_idx_sz += ALIGN(len, 8);
 492
 493                /*
 494                 * Once lprops is updated, we can decrease the dirty znode count
 495                 * but it is easier to just do it here.
 496                 */
 497                atomic_long_dec(&c->dirty_zn_cnt);
 498
 499                /*
 500                 * Calculate the next index node length to see if there is
 501                 * enough room for it
 502                 */
 503                cnext = znode->cnext;
 504                if (cnext == c->cnext)
 505                        next_len = 0;
 506                else
 507                        next_len = ubifs_idx_node_sz(c, cnext->child_cnt);
 508
 509                /* Update buffer positions */
 510                wlen = used + len;
 511                used += ALIGN(len, 8);
 512                avail -= ALIGN(len, 8);
 513
 514                if (next_len != 0 &&
 515                    buf_offs + used + next_len <= c->leb_size &&
 516                    avail > 0)
 517                        continue;
 518
 519                if (avail <= 0 && next_len &&
 520                    buf_offs + used + next_len <= c->leb_size)
 521                        blen = buf_len;
 522                else
 523                        blen = ALIGN(wlen, c->min_io_size);
 524
 525                /* The buffer is full or there are no more znodes to do */
 526                buf_offs += blen;
 527                if (next_len) {
 528                        if (buf_offs + next_len > c->leb_size) {
 529                                err = ubifs_update_one_lp(c, lnum,
 530                                        c->leb_size - buf_offs, blen - used,
 531                                        0, 0);
 532                                if (err)
 533                                        return err;
 534                                lnum = -1;
 535                        }
 536                        used -= blen;
 537                        if (used < 0)
 538                                used = 0;
 539                        avail = buf_len - used;
 540                        continue;
 541                }
 542                err = ubifs_update_one_lp(c, lnum, c->leb_size - buf_offs,
 543                                          blen - used, 0, 0);
 544                if (err)
 545                        return err;
 546                break;
 547        }
 548
 549        c->dbg->new_ihead_lnum = lnum;
 550        c->dbg->new_ihead_offs = buf_offs;
 551
 552        return 0;
 553}
 554
 555/**
 556 * layout_commit - determine positions of index nodes to commit.
 557 * @c: UBIFS file-system description object
 558 * @no_space: indicates that insufficient empty LEBs were allocated
 559 * @cnt: number of znodes to commit
 560 *
 561 * Calculate and update the positions of index nodes to commit.  If there were
 562 * an insufficient number of empty LEBs allocated, then index nodes are placed
 563 * into the gaps created by obsolete index nodes in non-empty index LEBs.  For
 564 * this purpose, an obsolete index node is one that was not in the index as at
 565 * the end of the last commit.  To write "in-the-gaps" requires that those index
 566 * LEBs are updated atomically in-place.
 567 */
 568static int layout_commit(struct ubifs_info *c, int no_space, int cnt)
 569{
 570        int err;
 571
 572        if (no_space) {
 573                err = layout_in_gaps(c, cnt);
 574                if (err)
 575                        return err;
 576        }
 577        err = layout_in_empty_space(c);
 578        return err;
 579}
 580
 581/**
 582 * find_first_dirty - find first dirty znode.
 583 * @znode: znode to begin searching from
 584 */
 585static struct ubifs_znode *find_first_dirty(struct ubifs_znode *znode)
 586{
 587        int i, cont;
 588
 589        if (!znode)
 590                return NULL;
 591
 592        while (1) {
 593                if (znode->level == 0) {
 594                        if (ubifs_zn_dirty(znode))
 595                                return znode;
 596                        return NULL;
 597                }
 598                cont = 0;
 599                for (i = 0; i < znode->child_cnt; i++) {
 600                        struct ubifs_zbranch *zbr = &znode->zbranch[i];
 601
 602                        if (zbr->znode && ubifs_zn_dirty(zbr->znode)) {
 603                                znode = zbr->znode;
 604                                cont = 1;
 605                                break;
 606                        }
 607                }
 608                if (!cont) {
 609                        if (ubifs_zn_dirty(znode))
 610                                return znode;
 611                        return NULL;
 612                }
 613        }
 614}
 615
 616/**
 617 * find_next_dirty - find next dirty znode.
 618 * @znode: znode to begin searching from
 619 */
 620static struct ubifs_znode *find_next_dirty(struct ubifs_znode *znode)
 621{
 622        int n = znode->iip + 1;
 623
 624        znode = znode->parent;
 625        if (!znode)
 626                return NULL;
 627        for (; n < znode->child_cnt; n++) {
 628                struct ubifs_zbranch *zbr = &znode->zbranch[n];
 629
 630                if (zbr->znode && ubifs_zn_dirty(zbr->znode))
 631                        return find_first_dirty(zbr->znode);
 632        }
 633        return znode;
 634}
 635
 636/**
 637 * get_znodes_to_commit - create list of dirty znodes to commit.
 638 * @c: UBIFS file-system description object
 639 *
 640 * This function returns the number of znodes to commit.
 641 */
 642static int get_znodes_to_commit(struct ubifs_info *c)
 643{
 644        struct ubifs_znode *znode, *cnext;
 645        int cnt = 0;
 646
 647        c->cnext = find_first_dirty(c->zroot.znode);
 648        znode = c->enext = c->cnext;
 649        if (!znode) {
 650                dbg_cmt("no znodes to commit");
 651                return 0;
 652        }
 653        cnt += 1;
 654        while (1) {
 655                ubifs_assert(c, !ubifs_zn_cow(znode));
 656                __set_bit(COW_ZNODE, &znode->flags);
 657                znode->alt = 0;
 658                cnext = find_next_dirty(znode);
 659                if (!cnext) {
 660                        znode->cnext = c->cnext;
 661                        break;
 662                }
 663                znode->cparent = znode->parent;
 664                znode->ciip = znode->iip;
 665                znode->cnext = cnext;
 666                znode = cnext;
 667                cnt += 1;
 668        }
 669        dbg_cmt("committing %d znodes", cnt);
 670        ubifs_assert(c, cnt == atomic_long_read(&c->dirty_zn_cnt));
 671        return cnt;
 672}
 673
 674/**
 675 * alloc_idx_lebs - allocate empty LEBs to be used to commit.
 676 * @c: UBIFS file-system description object
 677 * @cnt: number of znodes to commit
 678 *
 679 * This function returns %-ENOSPC if it cannot allocate a sufficient number of
 680 * empty LEBs.  %0 is returned on success, otherwise a negative error code
 681 * is returned.
 682 */
 683static int alloc_idx_lebs(struct ubifs_info *c, int cnt)
 684{
 685        int i, leb_cnt, lnum;
 686
 687        c->ileb_cnt = 0;
 688        c->ileb_nxt = 0;
 689        leb_cnt = get_leb_cnt(c, cnt);
 690        dbg_cmt("need about %d empty LEBS for TNC commit", leb_cnt);
 691        if (!leb_cnt)
 692                return 0;
 693        c->ilebs = kmalloc_array(leb_cnt, sizeof(int), GFP_NOFS);
 694        if (!c->ilebs)
 695                return -ENOMEM;
 696        for (i = 0; i < leb_cnt; i++) {
 697                lnum = ubifs_find_free_leb_for_idx(c);
 698                if (lnum < 0)
 699                        return lnum;
 700                c->ilebs[c->ileb_cnt++] = lnum;
 701                dbg_cmt("LEB %d", lnum);
 702        }
 703        if (dbg_is_chk_index(c) && !(prandom_u32() & 7))
 704                return -ENOSPC;
 705        return 0;
 706}
 707
 708/**
 709 * free_unused_idx_lebs - free unused LEBs that were allocated for the commit.
 710 * @c: UBIFS file-system description object
 711 *
 712 * It is possible that we allocate more empty LEBs for the commit than we need.
 713 * This functions frees the surplus.
 714 *
 715 * This function returns %0 on success and a negative error code on failure.
 716 */
 717static int free_unused_idx_lebs(struct ubifs_info *c)
 718{
 719        int i, err = 0, lnum, er;
 720
 721        for (i = c->ileb_nxt; i < c->ileb_cnt; i++) {
 722                lnum = c->ilebs[i];
 723                dbg_cmt("LEB %d", lnum);
 724                er = ubifs_change_one_lp(c, lnum, LPROPS_NC, LPROPS_NC, 0,
 725                                         LPROPS_INDEX | LPROPS_TAKEN, 0);
 726                if (!err)
 727                        err = er;
 728        }
 729        return err;
 730}
 731
 732/**
 733 * free_idx_lebs - free unused LEBs after commit end.
 734 * @c: UBIFS file-system description object
 735 *
 736 * This function returns %0 on success and a negative error code on failure.
 737 */
 738static int free_idx_lebs(struct ubifs_info *c)
 739{
 740        int err;
 741
 742        err = free_unused_idx_lebs(c);
 743        kfree(c->ilebs);
 744        c->ilebs = NULL;
 745        return err;
 746}
 747
 748/**
 749 * ubifs_tnc_start_commit - start TNC commit.
 750 * @c: UBIFS file-system description object
 751 * @zroot: new index root position is returned here
 752 *
 753 * This function prepares the list of indexing nodes to commit and lays out
 754 * their positions on flash. If there is not enough free space it uses the
 755 * in-gap commit method. Returns zero in case of success and a negative error
 756 * code in case of failure.
 757 */
 758int ubifs_tnc_start_commit(struct ubifs_info *c, struct ubifs_zbranch *zroot)
 759{
 760        int err = 0, cnt;
 761
 762        mutex_lock(&c->tnc_mutex);
 763        err = dbg_check_tnc(c, 1);
 764        if (err)
 765                goto out;
 766        cnt = get_znodes_to_commit(c);
 767        if (cnt != 0) {
 768                int no_space = 0;
 769
 770                err = alloc_idx_lebs(c, cnt);
 771                if (err == -ENOSPC)
 772                        no_space = 1;
 773                else if (err)
 774                        goto out_free;
 775                err = layout_commit(c, no_space, cnt);
 776                if (err)
 777                        goto out_free;
 778                ubifs_assert(c, atomic_long_read(&c->dirty_zn_cnt) == 0);
 779                err = free_unused_idx_lebs(c);
 780                if (err)
 781                        goto out;
 782        }
 783        destroy_old_idx(c);
 784        memcpy(zroot, &c->zroot, sizeof(struct ubifs_zbranch));
 785
 786        err = ubifs_save_dirty_idx_lnums(c);
 787        if (err)
 788                goto out;
 789
 790        spin_lock(&c->space_lock);
 791        /*
 792         * Although we have not finished committing yet, update size of the
 793         * committed index ('c->bi.old_idx_sz') and zero out the index growth
 794         * budget. It is OK to do this now, because we've reserved all the
 795         * space which is needed to commit the index, and it is save for the
 796         * budgeting subsystem to assume the index is already committed,
 797         * even though it is not.
 798         */
 799        ubifs_assert(c, c->bi.min_idx_lebs == ubifs_calc_min_idx_lebs(c));
 800        c->bi.old_idx_sz = c->calc_idx_sz;
 801        c->bi.uncommitted_idx = 0;
 802        c->bi.min_idx_lebs = ubifs_calc_min_idx_lebs(c);
 803        spin_unlock(&c->space_lock);
 804        mutex_unlock(&c->tnc_mutex);
 805
 806        dbg_cmt("number of index LEBs %d", c->lst.idx_lebs);
 807        dbg_cmt("size of index %llu", c->calc_idx_sz);
 808        return err;
 809
 810out_free:
 811        free_idx_lebs(c);
 812out:
 813        mutex_unlock(&c->tnc_mutex);
 814        return err;
 815}
 816
 817/**
 818 * write_index - write index nodes.
 819 * @c: UBIFS file-system description object
 820 *
 821 * This function writes the index nodes whose positions were laid out in the
 822 * layout_in_empty_space function.
 823 */
 824static int write_index(struct ubifs_info *c)
 825{
 826        struct ubifs_idx_node *idx;
 827        struct ubifs_znode *znode, *cnext;
 828        int i, lnum, offs, len, next_len, buf_len, buf_offs, used;
 829        int avail, wlen, err, lnum_pos = 0, blen, nxt_offs;
 830
 831        cnext = c->enext;
 832        if (!cnext)
 833                return 0;
 834
 835        /*
 836         * Always write index nodes to the index head so that index nodes and
 837         * other types of nodes are never mixed in the same erase block.
 838         */
 839        lnum = c->ihead_lnum;
 840        buf_offs = c->ihead_offs;
 841
 842        /* Allocate commit buffer */
 843        buf_len = ALIGN(c->max_idx_node_sz, c->min_io_size);
 844        used = 0;
 845        avail = buf_len;
 846
 847        /* Ensure there is enough room for first write */
 848        next_len = ubifs_idx_node_sz(c, cnext->child_cnt);
 849        if (buf_offs + next_len > c->leb_size) {
 850                err = ubifs_update_one_lp(c, lnum, LPROPS_NC, 0, 0,
 851                                          LPROPS_TAKEN);
 852                if (err)
 853                        return err;
 854                lnum = -1;
 855        }
 856
 857        while (1) {
 858                u8 hash[UBIFS_HASH_ARR_SZ];
 859
 860                cond_resched();
 861
 862                znode = cnext;
 863                idx = c->cbuf + used;
 864
 865                /* Make index node */
 866                idx->ch.node_type = UBIFS_IDX_NODE;
 867                idx->child_cnt = cpu_to_le16(znode->child_cnt);
 868                idx->level = cpu_to_le16(znode->level);
 869                for (i = 0; i < znode->child_cnt; i++) {
 870                        struct ubifs_branch *br = ubifs_idx_branch(c, idx, i);
 871                        struct ubifs_zbranch *zbr = &znode->zbranch[i];
 872
 873                        key_write_idx(c, &zbr->key, &br->key);
 874                        br->lnum = cpu_to_le32(zbr->lnum);
 875                        br->offs = cpu_to_le32(zbr->offs);
 876                        br->len = cpu_to_le32(zbr->len);
 877                        ubifs_copy_hash(c, zbr->hash, ubifs_branch_hash(c, br));
 878                        if (!zbr->lnum || !zbr->len) {
 879                                ubifs_err(c, "bad ref in znode");
 880                                ubifs_dump_znode(c, znode);
 881                                if (zbr->znode)
 882                                        ubifs_dump_znode(c, zbr->znode);
 883
 884                                return -EINVAL;
 885                        }
 886                }
 887                len = ubifs_idx_node_sz(c, znode->child_cnt);
 888                ubifs_prepare_node(c, idx, len, 0);
 889                ubifs_node_calc_hash(c, idx, hash);
 890
 891                mutex_lock(&c->tnc_mutex);
 892
 893                if (znode->cparent)
 894                        ubifs_copy_hash(c, hash,
 895                                        znode->cparent->zbranch[znode->ciip].hash);
 896
 897                if (znode->parent) {
 898                        if (!ubifs_zn_obsolete(znode))
 899                                ubifs_copy_hash(c, hash,
 900                                        znode->parent->zbranch[znode->iip].hash);
 901                } else {
 902                        ubifs_copy_hash(c, hash, c->zroot.hash);
 903                }
 904
 905                mutex_unlock(&c->tnc_mutex);
 906
 907                /* Determine the index node position */
 908                if (lnum == -1) {
 909                        lnum = c->ilebs[lnum_pos++];
 910                        buf_offs = 0;
 911                        used = 0;
 912                        avail = buf_len;
 913                }
 914                offs = buf_offs + used;
 915
 916                if (lnum != znode->lnum || offs != znode->offs ||
 917                    len != znode->len) {
 918                        ubifs_err(c, "inconsistent znode posn");
 919                        return -EINVAL;
 920                }
 921
 922                /* Grab some stuff from znode while we still can */
 923                cnext = znode->cnext;
 924
 925                ubifs_assert(c, ubifs_zn_dirty(znode));
 926                ubifs_assert(c, ubifs_zn_cow(znode));
 927
 928                /*
 929                 * It is important that other threads should see %DIRTY_ZNODE
 930                 * flag cleared before %COW_ZNODE. Specifically, it matters in
 931                 * the 'dirty_cow_znode()' function. This is the reason for the
 932                 * first barrier. Also, we want the bit changes to be seen to
 933                 * other threads ASAP, to avoid unnecessary copying, which is
 934                 * the reason for the second barrier.
 935                 */
 936                clear_bit(DIRTY_ZNODE, &znode->flags);
 937                smp_mb__before_atomic();
 938                clear_bit(COW_ZNODE, &znode->flags);
 939                smp_mb__after_atomic();
 940
 941                /*
 942                 * We have marked the znode as clean but have not updated the
 943                 * @c->clean_zn_cnt counter. If this znode becomes dirty again
 944                 * before 'free_obsolete_znodes()' is called, then
 945                 * @c->clean_zn_cnt will be decremented before it gets
 946                 * incremented (resulting in 2 decrements for the same znode).
 947                 * This means that @c->clean_zn_cnt may become negative for a
 948                 * while.
 949                 *
 950                 * Q: why we cannot increment @c->clean_zn_cnt?
 951                 * A: because we do not have the @c->tnc_mutex locked, and the
 952                 *    following code would be racy and buggy:
 953                 *
 954                 *    if (!ubifs_zn_obsolete(znode)) {
 955                 *            atomic_long_inc(&c->clean_zn_cnt);
 956                 *            atomic_long_inc(&ubifs_clean_zn_cnt);
 957                 *    }
 958                 *
 959                 *    Thus, we just delay the @c->clean_zn_cnt update until we
 960                 *    have the mutex locked.
 961                 */
 962
 963                /* Do not access znode from this point on */
 964
 965                /* Update buffer positions */
 966                wlen = used + len;
 967                used += ALIGN(len, 8);
 968                avail -= ALIGN(len, 8);
 969
 970                /*
 971                 * Calculate the next index node length to see if there is
 972                 * enough room for it
 973                 */
 974                if (cnext == c->cnext)
 975                        next_len = 0;
 976                else
 977                        next_len = ubifs_idx_node_sz(c, cnext->child_cnt);
 978
 979                nxt_offs = buf_offs + used + next_len;
 980                if (next_len && nxt_offs <= c->leb_size) {
 981                        if (avail > 0)
 982                                continue;
 983                        else
 984                                blen = buf_len;
 985                } else {
 986                        wlen = ALIGN(wlen, 8);
 987                        blen = ALIGN(wlen, c->min_io_size);
 988                        ubifs_pad(c, c->cbuf + wlen, blen - wlen);
 989                }
 990
 991                /* The buffer is full or there are no more znodes to do */
 992                err = ubifs_leb_write(c, lnum, c->cbuf, buf_offs, blen);
 993                if (err)
 994                        return err;
 995                buf_offs += blen;
 996                if (next_len) {
 997                        if (nxt_offs > c->leb_size) {
 998                                err = ubifs_update_one_lp(c, lnum, LPROPS_NC, 0,
 999                                                          0, LPROPS_TAKEN);
1000                                if (err)
1001                                        return err;
1002                                lnum = -1;
1003                        }
1004                        used -= blen;
1005                        if (used < 0)
1006                                used = 0;
1007                        avail = buf_len - used;
1008                        memmove(c->cbuf, c->cbuf + blen, used);
1009                        continue;
1010                }
1011                break;
1012        }
1013
1014        if (lnum != c->dbg->new_ihead_lnum ||
1015            buf_offs != c->dbg->new_ihead_offs) {
1016                ubifs_err(c, "inconsistent ihead");
1017                return -EINVAL;
1018        }
1019
1020        c->ihead_lnum = lnum;
1021        c->ihead_offs = buf_offs;
1022
1023        return 0;
1024}
1025
1026/**
1027 * free_obsolete_znodes - free obsolete znodes.
1028 * @c: UBIFS file-system description object
1029 *
1030 * At the end of commit end, obsolete znodes are freed.
1031 */
1032static void free_obsolete_znodes(struct ubifs_info *c)
1033{
1034        struct ubifs_znode *znode, *cnext;
1035
1036        cnext = c->cnext;
1037        do {
1038                znode = cnext;
1039                cnext = znode->cnext;
1040                if (ubifs_zn_obsolete(znode))
1041                        kfree(znode);
1042                else {
1043                        znode->cnext = NULL;
1044                        atomic_long_inc(&c->clean_zn_cnt);
1045                        atomic_long_inc(&ubifs_clean_zn_cnt);
1046                }
1047        } while (cnext != c->cnext);
1048}
1049
1050/**
1051 * return_gap_lebs - return LEBs used by the in-gap commit method.
1052 * @c: UBIFS file-system description object
1053 *
1054 * This function clears the "taken" flag for the LEBs which were used by the
1055 * "commit in-the-gaps" method.
1056 */
1057static int return_gap_lebs(struct ubifs_info *c)
1058{
1059        int *p, err;
1060
1061        if (!c->gap_lebs)
1062                return 0;
1063
1064        dbg_cmt("");
1065        for (p = c->gap_lebs; *p != -1; p++) {
1066                err = ubifs_change_one_lp(c, *p, LPROPS_NC, LPROPS_NC, 0,
1067                                          LPROPS_TAKEN, 0);
1068                if (err)
1069                        return err;
1070        }
1071
1072        kfree(c->gap_lebs);
1073        c->gap_lebs = NULL;
1074        return 0;
1075}
1076
1077/**
1078 * ubifs_tnc_end_commit - update the TNC for commit end.
1079 * @c: UBIFS file-system description object
1080 *
1081 * Write the dirty znodes.
1082 */
1083int ubifs_tnc_end_commit(struct ubifs_info *c)
1084{
1085        int err;
1086
1087        if (!c->cnext)
1088                return 0;
1089
1090        err = return_gap_lebs(c);
1091        if (err)
1092                return err;
1093
1094        err = write_index(c);
1095        if (err)
1096                return err;
1097
1098        mutex_lock(&c->tnc_mutex);
1099
1100        dbg_cmt("TNC height is %d", c->zroot.znode->level + 1);
1101
1102        free_obsolete_znodes(c);
1103
1104        c->cnext = NULL;
1105        kfree(c->ilebs);
1106        c->ilebs = NULL;
1107
1108        mutex_unlock(&c->tnc_mutex);
1109
1110        return 0;
1111}
1112
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