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