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 functions needed to recover from unclean un-mounts.
  25 * When UBIFS is mounted, it checks a flag on the master node to determine if
  26 * an un-mount was completed successfully. If not, the process of mounting
  27 * incorporates additional checking and fixing of on-flash data structures.
  28 * UBIFS always cleans away all remnants of an unclean un-mount, so that
  29 * errors do not accumulate. However UBIFS defers recovery if it is mounted
  30 * read-only, and the flash is not modified in that case.
  31 *
  32 * The general UBIFS approach to the recovery is that it recovers from
  33 * corruptions which could be caused by power cuts, but it refuses to recover
  34 * from corruption caused by other reasons. And UBIFS tries to distinguish
  35 * between these 2 reasons of corruptions and silently recover in the former
  36 * case and loudly complain in the latter case.
  37 *
  38 * UBIFS writes only to erased LEBs, so it writes only to the flash space
  39 * containing only 0xFFs. UBIFS also always writes strictly from the beginning
  40 * of the LEB to the end. And UBIFS assumes that the underlying flash media
  41 * writes in @c->max_write_size bytes at a time.
  42 *
  43 * Hence, if UBIFS finds a corrupted node at offset X, it expects only the min.
  44 * I/O unit corresponding to offset X to contain corrupted data, all the
  45 * following min. I/O units have to contain empty space (all 0xFFs). If this is
  46 * not true, the corruption cannot be the result of a power cut, and UBIFS
  47 * refuses to mount.
  48 */
  49
  50#include <linux/crc32.h>
  51#include <linux/slab.h>
  52#include "ubifs.h"
  53
  54/**
  55 * is_empty - determine whether a buffer is empty (contains all 0xff).
  56 * @buf: buffer to clean
  57 * @len: length of buffer
  58 *
  59 * This function returns %1 if the buffer is empty (contains all 0xff) otherwise
  60 * %0 is returned.
  61 */
  62static int is_empty(void *buf, int len)
  63{
  64	uint8_t *p = buf;
  65	int i;
  66
  67	for (i = 0; i < len; i++)
  68		if (*p++ != 0xff)
  69			return 0;
  70	return 1;
  71}
  72
  73/**
  74 * first_non_ff - find offset of the first non-0xff byte.
  75 * @buf: buffer to search in
  76 * @len: length of buffer
  77 *
  78 * This function returns offset of the first non-0xff byte in @buf or %-1 if
  79 * the buffer contains only 0xff bytes.
  80 */
  81static int first_non_ff(void *buf, int len)
  82{
  83	uint8_t *p = buf;
  84	int i;
  85
  86	for (i = 0; i < len; i++)
  87		if (*p++ != 0xff)
  88			return i;
  89	return -1;
  90}
  91
  92/**
  93 * get_master_node - get the last valid master node allowing for corruption.
  94 * @c: UBIFS file-system description object
  95 * @lnum: LEB number
  96 * @pbuf: buffer containing the LEB read, is returned here
  97 * @mst: master node, if found, is returned here
  98 * @cor: corruption, if found, is returned here
  99 *
 100 * This function allocates a buffer, reads the LEB into it, and finds and
 101 * returns the last valid master node allowing for one area of corruption.
 102 * The corrupt area, if there is one, must be consistent with the assumption
 103 * that it is the result of an unclean unmount while the master node was being
 104 * written. Under those circumstances, it is valid to use the previously written
 105 * master node.
 106 *
 107 * This function returns %0 on success and a negative error code on failure.
 108 */
 109static int get_master_node(const struct ubifs_info *c, int lnum, void **pbuf,
 110			   struct ubifs_mst_node **mst, void **cor)
 111{
 112	const int sz = c->mst_node_alsz;
 113	int err, offs, len;
 114	void *sbuf, *buf;
 115
 116	sbuf = vmalloc(c->leb_size);
 117	if (!sbuf)
 118		return -ENOMEM;
 119
 120	err = ubifs_leb_read(c, lnum, sbuf, 0, c->leb_size, 0);
 121	if (err && err != -EBADMSG)
 122		goto out_free;
 123
 124	/* Find the first position that is definitely not a node */
 125	offs = 0;
 126	buf = sbuf;
 127	len = c->leb_size;
 128	while (offs + UBIFS_MST_NODE_SZ <= c->leb_size) {
 129		struct ubifs_ch *ch = buf;
 130
 131		if (le32_to_cpu(ch->magic) != UBIFS_NODE_MAGIC)
 132			break;
 133		offs += sz;
 134		buf  += sz;
 135		len  -= sz;
 136	}
 137	/* See if there was a valid master node before that */
 138	if (offs) {
 139		int ret;
 140
 141		offs -= sz;
 142		buf  -= sz;
 143		len  += sz;
 144		ret = ubifs_scan_a_node(c, buf, len, lnum, offs, 1);
 145		if (ret != SCANNED_A_NODE && offs) {
 146			/* Could have been corruption so check one place back */
 147			offs -= sz;
 148			buf  -= sz;
 149			len  += sz;
 150			ret = ubifs_scan_a_node(c, buf, len, lnum, offs, 1);
 151			if (ret != SCANNED_A_NODE)
 152				/*
 153				 * We accept only one area of corruption because
 154				 * we are assuming that it was caused while
 155				 * trying to write a master node.
 156				 */
 157				goto out_err;
 158		}
 159		if (ret == SCANNED_A_NODE) {
 160			struct ubifs_ch *ch = buf;
 161
 162			if (ch->node_type != UBIFS_MST_NODE)
 163				goto out_err;
 164			dbg_rcvry("found a master node at %d:%d", lnum, offs);
 165			*mst = buf;
 166			offs += sz;
 167			buf  += sz;
 168			len  -= sz;
 169		}
 170	}
 171	/* Check for corruption */
 172	if (offs < c->leb_size) {
 173		if (!is_empty(buf, min_t(int, len, sz))) {
 174			*cor = buf;
 175			dbg_rcvry("found corruption at %d:%d", lnum, offs);
 176		}
 177		offs += sz;
 178		buf  += sz;
 179		len  -= sz;
 180	}
 181	/* Check remaining empty space */
 182	if (offs < c->leb_size)
 183		if (!is_empty(buf, len))
 184			goto out_err;
 185	*pbuf = sbuf;
 186	return 0;
 187
 188out_err:
 189	err = -EINVAL;
 190out_free:
 191	vfree(sbuf);
 192	*mst = NULL;
 193	*cor = NULL;
 194	return err;
 195}
 196
 197/**
 198 * write_rcvrd_mst_node - write recovered master node.
 199 * @c: UBIFS file-system description object
 200 * @mst: master node
 201 *
 202 * This function returns %0 on success and a negative error code on failure.
 203 */
 204static int write_rcvrd_mst_node(struct ubifs_info *c,
 205				struct ubifs_mst_node *mst)
 206{
 207	int err = 0, lnum = UBIFS_MST_LNUM, sz = c->mst_node_alsz;
 208	__le32 save_flags;
 209
 210	dbg_rcvry("recovery");
 211
 212	save_flags = mst->flags;
 213	mst->flags |= cpu_to_le32(UBIFS_MST_RCVRY);
 214
 215	ubifs_prepare_node(c, mst, UBIFS_MST_NODE_SZ, 1);
 216	err = ubifs_leb_change(c, lnum, mst, sz, UBI_SHORTTERM);
 
 
 
 217	if (err)
 218		goto out;
 219	err = ubifs_leb_change(c, lnum + 1, mst, sz, UBI_SHORTTERM);
 220	if (err)
 221		goto out;
 222out:
 223	mst->flags = save_flags;
 224	return err;
 225}
 226
 227/**
 228 * ubifs_recover_master_node - recover the master node.
 229 * @c: UBIFS file-system description object
 230 *
 231 * This function recovers the master node from corruption that may occur due to
 232 * an unclean unmount.
 233 *
 234 * This function returns %0 on success and a negative error code on failure.
 235 */
 236int ubifs_recover_master_node(struct ubifs_info *c)
 237{
 238	void *buf1 = NULL, *buf2 = NULL, *cor1 = NULL, *cor2 = NULL;
 239	struct ubifs_mst_node *mst1 = NULL, *mst2 = NULL, *mst;
 240	const int sz = c->mst_node_alsz;
 241	int err, offs1, offs2;
 242
 243	dbg_rcvry("recovery");
 244
 245	err = get_master_node(c, UBIFS_MST_LNUM, &buf1, &mst1, &cor1);
 246	if (err)
 247		goto out_free;
 248
 249	err = get_master_node(c, UBIFS_MST_LNUM + 1, &buf2, &mst2, &cor2);
 250	if (err)
 251		goto out_free;
 252
 253	if (mst1) {
 254		offs1 = (void *)mst1 - buf1;
 255		if ((le32_to_cpu(mst1->flags) & UBIFS_MST_RCVRY) &&
 256		    (offs1 == 0 && !cor1)) {
 257			/*
 258			 * mst1 was written by recovery at offset 0 with no
 259			 * corruption.
 260			 */
 261			dbg_rcvry("recovery recovery");
 262			mst = mst1;
 263		} else if (mst2) {
 264			offs2 = (void *)mst2 - buf2;
 265			if (offs1 == offs2) {
 266				/* Same offset, so must be the same */
 267				if (memcmp((void *)mst1 + UBIFS_CH_SZ,
 268					   (void *)mst2 + UBIFS_CH_SZ,
 269					   UBIFS_MST_NODE_SZ - UBIFS_CH_SZ))
 270					goto out_err;
 271				mst = mst1;
 272			} else if (offs2 + sz == offs1) {
 273				/* 1st LEB was written, 2nd was not */
 274				if (cor1)
 275					goto out_err;
 276				mst = mst1;
 277			} else if (offs1 == 0 &&
 278				   c->leb_size - offs2 - sz < sz) {
 279				/* 1st LEB was unmapped and written, 2nd not */
 280				if (cor1)
 281					goto out_err;
 282				mst = mst1;
 283			} else
 284				goto out_err;
 285		} else {
 286			/*
 287			 * 2nd LEB was unmapped and about to be written, so
 288			 * there must be only one master node in the first LEB
 289			 * and no corruption.
 290			 */
 291			if (offs1 != 0 || cor1)
 292				goto out_err;
 293			mst = mst1;
 294		}
 295	} else {
 296		if (!mst2)
 297			goto out_err;
 298		/*
 299		 * 1st LEB was unmapped and about to be written, so there must
 300		 * be no room left in 2nd LEB.
 301		 */
 302		offs2 = (void *)mst2 - buf2;
 303		if (offs2 + sz + sz <= c->leb_size)
 304			goto out_err;
 305		mst = mst2;
 306	}
 307
 308	ubifs_msg("recovered master node from LEB %d",
 309		  (mst == mst1 ? UBIFS_MST_LNUM : UBIFS_MST_LNUM + 1));
 310
 311	memcpy(c->mst_node, mst, UBIFS_MST_NODE_SZ);
 312
 313	if (c->ro_mount) {
 314		/* Read-only mode. Keep a copy for switching to rw mode */
 315		c->rcvrd_mst_node = kmalloc(sz, GFP_KERNEL);
 316		if (!c->rcvrd_mst_node) {
 317			err = -ENOMEM;
 318			goto out_free;
 319		}
 320		memcpy(c->rcvrd_mst_node, c->mst_node, UBIFS_MST_NODE_SZ);
 321
 322		/*
 323		 * We had to recover the master node, which means there was an
 324		 * unclean reboot. However, it is possible that the master node
 325		 * is clean at this point, i.e., %UBIFS_MST_DIRTY is not set.
 326		 * E.g., consider the following chain of events:
 327		 *
 328		 * 1. UBIFS was cleanly unmounted, so the master node is clean
 329		 * 2. UBIFS is being mounted R/W and starts changing the master
 330		 *    node in the first (%UBIFS_MST_LNUM). A power cut happens,
 331		 *    so this LEB ends up with some amount of garbage at the
 332		 *    end.
 333		 * 3. UBIFS is being mounted R/O. We reach this place and
 334		 *    recover the master node from the second LEB
 335		 *    (%UBIFS_MST_LNUM + 1). But we cannot update the media
 336		 *    because we are being mounted R/O. We have to defer the
 337		 *    operation.
 338		 * 4. However, this master node (@c->mst_node) is marked as
 339		 *    clean (since the step 1). And if we just return, the
 340		 *    mount code will be confused and won't recover the master
 341		 *    node when it is re-mounter R/W later.
 342		 *
 343		 *    Thus, to force the recovery by marking the master node as
 344		 *    dirty.
 345		 */
 346		c->mst_node->flags |= cpu_to_le32(UBIFS_MST_DIRTY);
 347	} else {
 348		/* Write the recovered master node */
 349		c->max_sqnum = le64_to_cpu(mst->ch.sqnum) - 1;
 350		err = write_rcvrd_mst_node(c, c->mst_node);
 351		if (err)
 352			goto out_free;
 353	}
 354
 355	vfree(buf2);
 356	vfree(buf1);
 357
 358	return 0;
 359
 360out_err:
 361	err = -EINVAL;
 362out_free:
 363	ubifs_err("failed to recover master node");
 364	if (mst1) {
 365		dbg_err("dumping first master node");
 366		dbg_dump_node(c, mst1);
 367	}
 368	if (mst2) {
 369		dbg_err("dumping second master node");
 370		dbg_dump_node(c, mst2);
 371	}
 372	vfree(buf2);
 373	vfree(buf1);
 374	return err;
 375}
 376
 377/**
 378 * ubifs_write_rcvrd_mst_node - write the recovered master node.
 379 * @c: UBIFS file-system description object
 380 *
 381 * This function writes the master node that was recovered during mounting in
 382 * read-only mode and must now be written because we are remounting rw.
 383 *
 384 * This function returns %0 on success and a negative error code on failure.
 385 */
 386int ubifs_write_rcvrd_mst_node(struct ubifs_info *c)
 387{
 388	int err;
 389
 390	if (!c->rcvrd_mst_node)
 391		return 0;
 392	c->rcvrd_mst_node->flags |= cpu_to_le32(UBIFS_MST_DIRTY);
 393	c->mst_node->flags |= cpu_to_le32(UBIFS_MST_DIRTY);
 394	err = write_rcvrd_mst_node(c, c->rcvrd_mst_node);
 395	if (err)
 396		return err;
 397	kfree(c->rcvrd_mst_node);
 398	c->rcvrd_mst_node = NULL;
 399	return 0;
 400}
 401
 402/**
 403 * is_last_write - determine if an offset was in the last write to a LEB.
 404 * @c: UBIFS file-system description object
 405 * @buf: buffer to check
 406 * @offs: offset to check
 407 *
 408 * This function returns %1 if @offs was in the last write to the LEB whose data
 409 * is in @buf, otherwise %0 is returned. The determination is made by checking
 410 * for subsequent empty space starting from the next @c->max_write_size
 411 * boundary.
 412 */
 413static int is_last_write(const struct ubifs_info *c, void *buf, int offs)
 414{
 415	int empty_offs, check_len;
 416	uint8_t *p;
 417
 418	/*
 419	 * Round up to the next @c->max_write_size boundary i.e. @offs is in
 420	 * the last wbuf written. After that should be empty space.
 421	 */
 422	empty_offs = ALIGN(offs + 1, c->max_write_size);
 423	check_len = c->leb_size - empty_offs;
 424	p = buf + empty_offs - offs;
 425	return is_empty(p, check_len);
 426}
 427
 428/**
 429 * clean_buf - clean the data from an LEB sitting in a buffer.
 430 * @c: UBIFS file-system description object
 431 * @buf: buffer to clean
 432 * @lnum: LEB number to clean
 433 * @offs: offset from which to clean
 434 * @len: length of buffer
 435 *
 436 * This function pads up to the next min_io_size boundary (if there is one) and
 437 * sets empty space to all 0xff. @buf, @offs and @len are updated to the next
 438 * @c->min_io_size boundary.
 439 */
 440static void clean_buf(const struct ubifs_info *c, void **buf, int lnum,
 441		      int *offs, int *len)
 442{
 443	int empty_offs, pad_len;
 444
 445	lnum = lnum;
 446	dbg_rcvry("cleaning corruption at %d:%d", lnum, *offs);
 447
 448	ubifs_assert(!(*offs & 7));
 449	empty_offs = ALIGN(*offs, c->min_io_size);
 450	pad_len = empty_offs - *offs;
 451	ubifs_pad(c, *buf, pad_len);
 452	*offs += pad_len;
 453	*buf += pad_len;
 454	*len -= pad_len;
 455	memset(*buf, 0xff, c->leb_size - empty_offs);
 456}
 457
 458/**
 459 * no_more_nodes - determine if there are no more nodes in a buffer.
 460 * @c: UBIFS file-system description object
 461 * @buf: buffer to check
 462 * @len: length of buffer
 463 * @lnum: LEB number of the LEB from which @buf was read
 464 * @offs: offset from which @buf was read
 465 *
 466 * This function ensures that the corrupted node at @offs is the last thing
 467 * written to a LEB. This function returns %1 if more data is not found and
 468 * %0 if more data is found.
 469 */
 470static int no_more_nodes(const struct ubifs_info *c, void *buf, int len,
 471			int lnum, int offs)
 472{
 473	struct ubifs_ch *ch = buf;
 474	int skip, dlen = le32_to_cpu(ch->len);
 475
 476	/* Check for empty space after the corrupt node's common header */
 477	skip = ALIGN(offs + UBIFS_CH_SZ, c->max_write_size) - offs;
 478	if (is_empty(buf + skip, len - skip))
 479		return 1;
 480	/*
 481	 * The area after the common header size is not empty, so the common
 482	 * header must be intact. Check it.
 483	 */
 484	if (ubifs_check_node(c, buf, lnum, offs, 1, 0) != -EUCLEAN) {
 485		dbg_rcvry("unexpected bad common header at %d:%d", lnum, offs);
 486		return 0;
 487	}
 488	/* Now we know the corrupt node's length we can skip over it */
 489	skip = ALIGN(offs + dlen, c->max_write_size) - offs;
 490	/* After which there should be empty space */
 491	if (is_empty(buf + skip, len - skip))
 492		return 1;
 493	dbg_rcvry("unexpected data at %d:%d", lnum, offs + skip);
 494	return 0;
 495}
 496
 497/**
 498 * fix_unclean_leb - fix an unclean LEB.
 499 * @c: UBIFS file-system description object
 500 * @sleb: scanned LEB information
 501 * @start: offset where scan started
 502 */
 503static int fix_unclean_leb(struct ubifs_info *c, struct ubifs_scan_leb *sleb,
 504			   int start)
 505{
 506	int lnum = sleb->lnum, endpt = start;
 507
 508	/* Get the end offset of the last node we are keeping */
 509	if (!list_empty(&sleb->nodes)) {
 510		struct ubifs_scan_node *snod;
 511
 512		snod = list_entry(sleb->nodes.prev,
 513				  struct ubifs_scan_node, list);
 514		endpt = snod->offs + snod->len;
 515	}
 516
 517	if (c->ro_mount && !c->remounting_rw) {
 518		/* Add to recovery list */
 519		struct ubifs_unclean_leb *ucleb;
 520
 521		dbg_rcvry("need to fix LEB %d start %d endpt %d",
 522			  lnum, start, sleb->endpt);
 523		ucleb = kzalloc(sizeof(struct ubifs_unclean_leb), GFP_NOFS);
 524		if (!ucleb)
 525			return -ENOMEM;
 526		ucleb->lnum = lnum;
 527		ucleb->endpt = endpt;
 528		list_add_tail(&ucleb->list, &c->unclean_leb_list);
 529	} else {
 530		/* Write the fixed LEB back to flash */
 531		int err;
 532
 533		dbg_rcvry("fixing LEB %d start %d endpt %d",
 534			  lnum, start, sleb->endpt);
 535		if (endpt == 0) {
 536			err = ubifs_leb_unmap(c, lnum);
 537			if (err)
 538				return err;
 539		} else {
 540			int len = ALIGN(endpt, c->min_io_size);
 541
 542			if (start) {
 543				err = ubifs_leb_read(c, lnum, sleb->buf, 0,
 544						     start, 1);
 545				if (err)
 546					return err;
 547			}
 548			/* Pad to min_io_size */
 549			if (len > endpt) {
 550				int pad_len = len - ALIGN(endpt, 8);
 551
 552				if (pad_len > 0) {
 553					void *buf = sleb->buf + len - pad_len;
 554
 555					ubifs_pad(c, buf, pad_len);
 556				}
 557			}
 558			err = ubifs_leb_change(c, lnum, sleb->buf, len,
 559					       UBI_UNKNOWN);
 560			if (err)
 561				return err;
 562		}
 563	}
 564	return 0;
 565}
 566
 567/**
 568 * drop_last_group - drop the last group of nodes.
 569 * @sleb: scanned LEB information
 570 * @offs: offset of dropped nodes is returned here
 571 *
 572 * This is a helper function for 'ubifs_recover_leb()' which drops the last
 573 * group of nodes of the scanned LEB.
 574 */
 575static void drop_last_group(struct ubifs_scan_leb *sleb, int *offs)
 576{
 577	while (!list_empty(&sleb->nodes)) {
 578		struct ubifs_scan_node *snod;
 579		struct ubifs_ch *ch;
 580
 581		snod = list_entry(sleb->nodes.prev, struct ubifs_scan_node,
 582				  list);
 583		ch = snod->node;
 584		if (ch->group_type != UBIFS_IN_NODE_GROUP)
 585			break;
 586
 587		dbg_rcvry("dropping grouped node at %d:%d",
 588			  sleb->lnum, snod->offs);
 589		*offs = snod->offs;
 590		list_del(&snod->list);
 591		kfree(snod);
 592		sleb->nodes_cnt -= 1;
 593	}
 594}
 595
 596/**
 597 * drop_last_node - drop the last node.
 598 * @sleb: scanned LEB information
 599 * @offs: offset of dropped nodes is returned here
 600 * @grouped: non-zero if whole group of nodes have to be dropped
 601 *
 602 * This is a helper function for 'ubifs_recover_leb()' which drops the last
 603 * node of the scanned LEB.
 604 */
 605static void drop_last_node(struct ubifs_scan_leb *sleb, int *offs)
 606{
 607	struct ubifs_scan_node *snod;
 608
 609	if (!list_empty(&sleb->nodes)) {
 610		snod = list_entry(sleb->nodes.prev, struct ubifs_scan_node,
 611				  list);
 612
 613		dbg_rcvry("dropping last node at %d:%d", sleb->lnum, snod->offs);
 
 614		*offs = snod->offs;
 615		list_del(&snod->list);
 616		kfree(snod);
 617		sleb->nodes_cnt -= 1;
 618	}
 619}
 620
 621/**
 622 * ubifs_recover_leb - scan and recover a LEB.
 623 * @c: UBIFS file-system description object
 624 * @lnum: LEB number
 625 * @offs: offset
 626 * @sbuf: LEB-sized buffer to use
 627 * @jhead: journal head number this LEB belongs to (%-1 if the LEB does not
 628 *         belong to any journal head)
 629 *
 630 * This function does a scan of a LEB, but caters for errors that might have
 631 * been caused by the unclean unmount from which we are attempting to recover.
 632 * Returns %0 in case of success, %-EUCLEAN if an unrecoverable corruption is
 633 * found, and a negative error code in case of failure.
 634 */
 635struct ubifs_scan_leb *ubifs_recover_leb(struct ubifs_info *c, int lnum,
 636					 int offs, void *sbuf, int jhead)
 637{
 638	int ret = 0, err, len = c->leb_size - offs, start = offs, min_io_unit;
 639	int grouped = jhead == -1 ? 0 : c->jheads[jhead].grouped;
 640	struct ubifs_scan_leb *sleb;
 641	void *buf = sbuf + offs;
 642
 643	dbg_rcvry("%d:%d, jhead %d, grouped %d", lnum, offs, jhead, grouped);
 644
 645	sleb = ubifs_start_scan(c, lnum, offs, sbuf);
 646	if (IS_ERR(sleb))
 647		return sleb;
 648
 649	ubifs_assert(len >= 8);
 650	while (len >= 8) {
 651		dbg_scan("look at LEB %d:%d (%d bytes left)",
 652			 lnum, offs, len);
 653
 654		cond_resched();
 655
 656		/*
 657		 * Scan quietly until there is an error from which we cannot
 658		 * recover
 659		 */
 660		ret = ubifs_scan_a_node(c, buf, len, lnum, offs, 1);
 661		if (ret == SCANNED_A_NODE) {
 662			/* A valid node, and not a padding node */
 663			struct ubifs_ch *ch = buf;
 664			int node_len;
 665
 666			err = ubifs_add_snod(c, sleb, buf, offs);
 667			if (err)
 668				goto error;
 669			node_len = ALIGN(le32_to_cpu(ch->len), 8);
 670			offs += node_len;
 671			buf += node_len;
 672			len -= node_len;
 673		} else if (ret > 0) {
 674			/* Padding bytes or a valid padding node */
 675			offs += ret;
 676			buf += ret;
 677			len -= ret;
 678		} else if (ret == SCANNED_EMPTY_SPACE ||
 679			   ret == SCANNED_GARBAGE     ||
 680			   ret == SCANNED_A_BAD_PAD_NODE ||
 681			   ret == SCANNED_A_CORRUPT_NODE) {
 682			dbg_rcvry("found corruption - %d", ret);
 
 683			break;
 684		} else {
 685			dbg_err("unexpected return value %d", ret);
 686			err = -EINVAL;
 687			goto error;
 688		}
 689	}
 690
 691	if (ret == SCANNED_GARBAGE || ret == SCANNED_A_BAD_PAD_NODE) {
 692		if (!is_last_write(c, buf, offs))
 693			goto corrupted_rescan;
 694	} else if (ret == SCANNED_A_CORRUPT_NODE) {
 695		if (!no_more_nodes(c, buf, len, lnum, offs))
 696			goto corrupted_rescan;
 697	} else if (!is_empty(buf, len)) {
 698		if (!is_last_write(c, buf, offs)) {
 699			int corruption = first_non_ff(buf, len);
 700
 701			/*
 702			 * See header comment for this file for more
 703			 * explanations about the reasons we have this check.
 704			 */
 705			ubifs_err("corrupt empty space LEB %d:%d, corruption "
 706				  "starts at %d", lnum, offs, corruption);
 707			/* Make sure we dump interesting non-0xFF data */
 708			offs += corruption;
 709			buf += corruption;
 710			goto corrupted;
 711		}
 712	}
 713
 714	min_io_unit = round_down(offs, c->min_io_size);
 715	if (grouped)
 716		/*
 717		 * If nodes are grouped, always drop the incomplete group at
 718		 * the end.
 719		 */
 720		drop_last_group(sleb, &offs);
 721
 722	if (jhead == GCHD) {
 723		/*
 724		 * If this LEB belongs to the GC head then while we are in the
 725		 * middle of the same min. I/O unit keep dropping nodes. So
 726		 * basically, what we want is to make sure that the last min.
 727		 * I/O unit where we saw the corruption is dropped completely
 728		 * with all the uncorrupted nodes which may possibly sit there.
 729		 *
 730		 * In other words, let's name the min. I/O unit where the
 731		 * corruption starts B, and the previous min. I/O unit A. The
 732		 * below code tries to deal with a situation when half of B
 733		 * contains valid nodes or the end of a valid node, and the
 734		 * second half of B contains corrupted data or garbage. This
 735		 * means that UBIFS had been writing to B just before the power
 736		 * cut happened. I do not know how realistic is this scenario
 737		 * that half of the min. I/O unit had been written successfully
 738		 * and the other half not, but this is possible in our 'failure
 739		 * mode emulation' infrastructure at least.
 740		 *
 741		 * So what is the problem, why we need to drop those nodes? Why
 742		 * can't we just clean-up the second half of B by putting a
 743		 * padding node there? We can, and this works fine with one
 744		 * exception which was reproduced with power cut emulation
 745		 * testing and happens extremely rarely.
 746		 *
 747		 * Imagine the file-system is full, we run GC which starts
 748		 * moving valid nodes from LEB X to LEB Y (obviously, LEB Y is
 749		 * the current GC head LEB). The @c->gc_lnum is -1, which means
 750		 * that GC will retain LEB X and will try to continue. Imagine
 751		 * that LEB X is currently the dirtiest LEB, and the amount of
 752		 * used space in LEB Y is exactly the same as amount of free
 753		 * space in LEB X.
 754		 *
 755		 * And a power cut happens when nodes are moved from LEB X to
 756		 * LEB Y. We are here trying to recover LEB Y which is the GC
 757		 * head LEB. We find the min. I/O unit B as described above.
 758		 * Then we clean-up LEB Y by padding min. I/O unit. And later
 759		 * 'ubifs_rcvry_gc_commit()' function fails, because it cannot
 760		 * find a dirty LEB which could be GC'd into LEB Y! Even LEB X
 761		 * does not match because the amount of valid nodes there does
 762		 * not fit the free space in LEB Y any more! And this is
 763		 * because of the padding node which we added to LEB Y. The
 764		 * user-visible effect of this which I once observed and
 765		 * analysed is that we cannot mount the file-system with
 766		 * -ENOSPC error.
 767		 *
 768		 * So obviously, to make sure that situation does not happen we
 769		 * should free min. I/O unit B in LEB Y completely and the last
 770		 * used min. I/O unit in LEB Y should be A. This is basically
 771		 * what the below code tries to do.
 772		 */
 773		while (offs > min_io_unit)
 774			drop_last_node(sleb, &offs);
 775	}
 776
 777	buf = sbuf + offs;
 778	len = c->leb_size - offs;
 779
 780	clean_buf(c, &buf, lnum, &offs, &len);
 781	ubifs_end_scan(c, sleb, lnum, offs);
 782
 783	err = fix_unclean_leb(c, sleb, start);
 784	if (err)
 785		goto error;
 786
 787	return sleb;
 788
 789corrupted_rescan:
 790	/* Re-scan the corrupted data with verbose messages */
 791	dbg_err("corruptio %d", ret);
 792	ubifs_scan_a_node(c, buf, len, lnum, offs, 1);
 793corrupted:
 794	ubifs_scanned_corruption(c, lnum, offs, buf);
 795	err = -EUCLEAN;
 796error:
 797	ubifs_err("LEB %d scanning failed", lnum);
 798	ubifs_scan_destroy(sleb);
 799	return ERR_PTR(err);
 800}
 801
 802/**
 803 * get_cs_sqnum - get commit start sequence number.
 804 * @c: UBIFS file-system description object
 805 * @lnum: LEB number of commit start node
 806 * @offs: offset of commit start node
 807 * @cs_sqnum: commit start sequence number is returned here
 808 *
 809 * This function returns %0 on success and a negative error code on failure.
 810 */
 811static int get_cs_sqnum(struct ubifs_info *c, int lnum, int offs,
 812			unsigned long long *cs_sqnum)
 813{
 814	struct ubifs_cs_node *cs_node = NULL;
 815	int err, ret;
 816
 817	dbg_rcvry("at %d:%d", lnum, offs);
 818	cs_node = kmalloc(UBIFS_CS_NODE_SZ, GFP_KERNEL);
 819	if (!cs_node)
 820		return -ENOMEM;
 821	if (c->leb_size - offs < UBIFS_CS_NODE_SZ)
 822		goto out_err;
 823	err = ubifs_leb_read(c, lnum, (void *)cs_node, offs,
 824			     UBIFS_CS_NODE_SZ, 0);
 825	if (err && err != -EBADMSG)
 826		goto out_free;
 827	ret = ubifs_scan_a_node(c, cs_node, UBIFS_CS_NODE_SZ, lnum, offs, 0);
 828	if (ret != SCANNED_A_NODE) {
 829		dbg_err("Not a valid node");
 830		goto out_err;
 831	}
 832	if (cs_node->ch.node_type != UBIFS_CS_NODE) {
 833		dbg_err("Node a CS node, type is %d", cs_node->ch.node_type);
 834		goto out_err;
 835	}
 836	if (le64_to_cpu(cs_node->cmt_no) != c->cmt_no) {
 837		dbg_err("CS node cmt_no %llu != current cmt_no %llu",
 838			(unsigned long long)le64_to_cpu(cs_node->cmt_no),
 839			c->cmt_no);
 840		goto out_err;
 841	}
 842	*cs_sqnum = le64_to_cpu(cs_node->ch.sqnum);
 843	dbg_rcvry("commit start sqnum %llu", *cs_sqnum);
 844	kfree(cs_node);
 845	return 0;
 846
 847out_err:
 848	err = -EINVAL;
 849out_free:
 850	ubifs_err("failed to get CS sqnum");
 851	kfree(cs_node);
 852	return err;
 853}
 854
 855/**
 856 * ubifs_recover_log_leb - scan and recover a log LEB.
 857 * @c: UBIFS file-system description object
 858 * @lnum: LEB number
 859 * @offs: offset
 860 * @sbuf: LEB-sized buffer to use
 861 *
 862 * This function does a scan of a LEB, but caters for errors that might have
 863 * been caused by unclean reboots from which we are attempting to recover
 864 * (assume that only the last log LEB can be corrupted by an unclean reboot).
 865 *
 866 * This function returns %0 on success and a negative error code on failure.
 867 */
 868struct ubifs_scan_leb *ubifs_recover_log_leb(struct ubifs_info *c, int lnum,
 869					     int offs, void *sbuf)
 870{
 871	struct ubifs_scan_leb *sleb;
 872	int next_lnum;
 873
 874	dbg_rcvry("LEB %d", lnum);
 875	next_lnum = lnum + 1;
 876	if (next_lnum >= UBIFS_LOG_LNUM + c->log_lebs)
 877		next_lnum = UBIFS_LOG_LNUM;
 878	if (next_lnum != c->ltail_lnum) {
 879		/*
 880		 * We can only recover at the end of the log, so check that the
 881		 * next log LEB is empty or out of date.
 882		 */
 883		sleb = ubifs_scan(c, next_lnum, 0, sbuf, 0);
 884		if (IS_ERR(sleb))
 885			return sleb;
 886		if (sleb->nodes_cnt) {
 887			struct ubifs_scan_node *snod;
 888			unsigned long long cs_sqnum = c->cs_sqnum;
 889
 890			snod = list_entry(sleb->nodes.next,
 891					  struct ubifs_scan_node, list);
 892			if (cs_sqnum == 0) {
 893				int err;
 894
 895				err = get_cs_sqnum(c, lnum, offs, &cs_sqnum);
 896				if (err) {
 897					ubifs_scan_destroy(sleb);
 898					return ERR_PTR(err);
 899				}
 900			}
 901			if (snod->sqnum > cs_sqnum) {
 902				ubifs_err("unrecoverable log corruption "
 903					  "in LEB %d", lnum);
 904				ubifs_scan_destroy(sleb);
 905				return ERR_PTR(-EUCLEAN);
 906			}
 907		}
 908		ubifs_scan_destroy(sleb);
 909	}
 910	return ubifs_recover_leb(c, lnum, offs, sbuf, -1);
 911}
 912
 913/**
 914 * recover_head - recover a head.
 915 * @c: UBIFS file-system description object
 916 * @lnum: LEB number of head to recover
 917 * @offs: offset of head to recover
 918 * @sbuf: LEB-sized buffer to use
 919 *
 920 * This function ensures that there is no data on the flash at a head location.
 921 *
 922 * This function returns %0 on success and a negative error code on failure.
 923 */
 924static int recover_head(struct ubifs_info *c, int lnum, int offs, void *sbuf)
 925{
 926	int len = c->max_write_size, err;
 927
 928	if (offs + len > c->leb_size)
 929		len = c->leb_size - offs;
 930
 931	if (!len)
 932		return 0;
 933
 934	/* Read at the head location and check it is empty flash */
 935	err = ubifs_leb_read(c, lnum, sbuf, offs, len, 1);
 936	if (err || !is_empty(sbuf, len)) {
 937		dbg_rcvry("cleaning head at %d:%d", lnum, offs);
 938		if (offs == 0)
 939			return ubifs_leb_unmap(c, lnum);
 940		err = ubifs_leb_read(c, lnum, sbuf, 0, offs, 1);
 941		if (err)
 942			return err;
 943		return ubifs_leb_change(c, lnum, sbuf, offs, UBI_UNKNOWN);
 944	}
 945
 946	return 0;
 947}
 948
 949/**
 950 * ubifs_recover_inl_heads - recover index and LPT heads.
 951 * @c: UBIFS file-system description object
 952 * @sbuf: LEB-sized buffer to use
 953 *
 954 * This function ensures that there is no data on the flash at the index and
 955 * LPT head locations.
 956 *
 957 * This deals with the recovery of a half-completed journal commit. UBIFS is
 958 * careful never to overwrite the last version of the index or the LPT. Because
 959 * the index and LPT are wandering trees, data from a half-completed commit will
 960 * not be referenced anywhere in UBIFS. The data will be either in LEBs that are
 961 * assumed to be empty and will be unmapped anyway before use, or in the index
 962 * and LPT heads.
 963 *
 964 * This function returns %0 on success and a negative error code on failure.
 965 */
 966int ubifs_recover_inl_heads(struct ubifs_info *c, void *sbuf)
 967{
 968	int err;
 969
 970	ubifs_assert(!c->ro_mount || c->remounting_rw);
 971
 972	dbg_rcvry("checking index head at %d:%d", c->ihead_lnum, c->ihead_offs);
 973	err = recover_head(c, c->ihead_lnum, c->ihead_offs, sbuf);
 974	if (err)
 975		return err;
 976
 977	dbg_rcvry("checking LPT head at %d:%d", c->nhead_lnum, c->nhead_offs);
 978	err = recover_head(c, c->nhead_lnum, c->nhead_offs, sbuf);
 979	if (err)
 980		return err;
 981
 982	return 0;
 983}
 984
 985/**
 986 *  clean_an_unclean_leb - read and write a LEB to remove corruption.
 987 * @c: UBIFS file-system description object
 988 * @ucleb: unclean LEB information
 989 * @sbuf: LEB-sized buffer to use
 990 *
 991 * This function reads a LEB up to a point pre-determined by the mount recovery,
 992 * checks the nodes, and writes the result back to the flash, thereby cleaning
 993 * off any following corruption, or non-fatal ECC errors.
 994 *
 995 * This function returns %0 on success and a negative error code on failure.
 996 */
 997static int clean_an_unclean_leb(struct ubifs_info *c,
 998				struct ubifs_unclean_leb *ucleb, void *sbuf)
 999{
1000	int err, lnum = ucleb->lnum, offs = 0, len = ucleb->endpt, quiet = 1;
1001	void *buf = sbuf;
1002
1003	dbg_rcvry("LEB %d len %d", lnum, len);
1004
1005	if (len == 0) {
1006		/* Nothing to read, just unmap it */
1007		err = ubifs_leb_unmap(c, lnum);
1008		if (err)
1009			return err;
1010		return 0;
1011	}
1012
1013	err = ubifs_leb_read(c, lnum, buf, offs, len, 0);
1014	if (err && err != -EBADMSG)
1015		return err;
1016
1017	while (len >= 8) {
1018		int ret;
1019
1020		cond_resched();
1021
1022		/* Scan quietly until there is an error */
1023		ret = ubifs_scan_a_node(c, buf, len, lnum, offs, quiet);
1024
1025		if (ret == SCANNED_A_NODE) {
1026			/* A valid node, and not a padding node */
1027			struct ubifs_ch *ch = buf;
1028			int node_len;
1029
1030			node_len = ALIGN(le32_to_cpu(ch->len), 8);
1031			offs += node_len;
1032			buf += node_len;
1033			len -= node_len;
1034			continue;
1035		}
1036
1037		if (ret > 0) {
1038			/* Padding bytes or a valid padding node */
1039			offs += ret;
1040			buf += ret;
1041			len -= ret;
1042			continue;
1043		}
1044
1045		if (ret == SCANNED_EMPTY_SPACE) {
1046			ubifs_err("unexpected empty space at %d:%d",
1047				  lnum, offs);
1048			return -EUCLEAN;
1049		}
1050
1051		if (quiet) {
1052			/* Redo the last scan but noisily */
1053			quiet = 0;
1054			continue;
1055		}
1056
1057		ubifs_scanned_corruption(c, lnum, offs, buf);
1058		return -EUCLEAN;
1059	}
1060
1061	/* Pad to min_io_size */
1062	len = ALIGN(ucleb->endpt, c->min_io_size);
1063	if (len > ucleb->endpt) {
1064		int pad_len = len - ALIGN(ucleb->endpt, 8);
1065
1066		if (pad_len > 0) {
1067			buf = c->sbuf + len - pad_len;
1068			ubifs_pad(c, buf, pad_len);
1069		}
1070	}
1071
1072	/* Write back the LEB atomically */
1073	err = ubifs_leb_change(c, lnum, sbuf, len, UBI_UNKNOWN);
1074	if (err)
1075		return err;
1076
1077	dbg_rcvry("cleaned LEB %d", lnum);
1078
1079	return 0;
1080}
1081
1082/**
1083 * ubifs_clean_lebs - clean LEBs recovered during read-only mount.
1084 * @c: UBIFS file-system description object
1085 * @sbuf: LEB-sized buffer to use
1086 *
1087 * This function cleans a LEB identified during recovery that needs to be
1088 * written but was not because UBIFS was mounted read-only. This happens when
1089 * remounting to read-write mode.
1090 *
1091 * This function returns %0 on success and a negative error code on failure.
1092 */
1093int ubifs_clean_lebs(struct ubifs_info *c, void *sbuf)
1094{
1095	dbg_rcvry("recovery");
1096	while (!list_empty(&c->unclean_leb_list)) {
1097		struct ubifs_unclean_leb *ucleb;
1098		int err;
1099
1100		ucleb = list_entry(c->unclean_leb_list.next,
1101				   struct ubifs_unclean_leb, list);
1102		err = clean_an_unclean_leb(c, ucleb, sbuf);
1103		if (err)
1104			return err;
1105		list_del(&ucleb->list);
1106		kfree(ucleb);
1107	}
1108	return 0;
1109}
1110
1111/**
1112 * grab_empty_leb - grab an empty LEB to use as GC LEB and run commit.
1113 * @c: UBIFS file-system description object
1114 *
1115 * This is a helper function for 'ubifs_rcvry_gc_commit()' which grabs an empty
1116 * LEB to be used as GC LEB (@c->gc_lnum), and then runs the commit. Returns
1117 * zero in case of success and a negative error code in case of failure.
1118 */
1119static int grab_empty_leb(struct ubifs_info *c)
1120{
1121	int lnum, err;
1122
1123	/*
1124	 * Note, it is very important to first search for an empty LEB and then
1125	 * run the commit, not vice-versa. The reason is that there might be
1126	 * only one empty LEB at the moment, the one which has been the
1127	 * @c->gc_lnum just before the power cut happened. During the regular
1128	 * UBIFS operation (not now) @c->gc_lnum is marked as "taken", so no
1129	 * one but GC can grab it. But at this moment this single empty LEB is
1130	 * not marked as taken, so if we run commit - what happens? Right, the
1131	 * commit will grab it and write the index there. Remember that the
1132	 * index always expands as long as there is free space, and it only
1133	 * starts consolidating when we run out of space.
1134	 *
1135	 * IOW, if we run commit now, we might not be able to find a free LEB
1136	 * after this.
1137	 */
1138	lnum = ubifs_find_free_leb_for_idx(c);
1139	if (lnum < 0) {
1140		dbg_err("could not find an empty LEB");
1141		dbg_dump_lprops(c);
1142		dbg_dump_budg(c, &c->bi);
1143		return lnum;
1144	}
1145
1146	/* Reset the index flag */
1147	err = ubifs_change_one_lp(c, lnum, LPROPS_NC, LPROPS_NC, 0,
1148				  LPROPS_INDEX, 0);
1149	if (err)
1150		return err;
1151
1152	c->gc_lnum = lnum;
1153	dbg_rcvry("found empty LEB %d, run commit", lnum);
1154
1155	return ubifs_run_commit(c);
1156}
1157
1158/**
1159 * ubifs_rcvry_gc_commit - recover the GC LEB number and run the commit.
1160 * @c: UBIFS file-system description object
1161 *
1162 * Out-of-place garbage collection requires always one empty LEB with which to
1163 * start garbage collection. The LEB number is recorded in c->gc_lnum and is
1164 * written to the master node on unmounting. In the case of an unclean unmount
1165 * the value of gc_lnum recorded in the master node is out of date and cannot
1166 * be used. Instead, recovery must allocate an empty LEB for this purpose.
1167 * However, there may not be enough empty space, in which case it must be
1168 * possible to GC the dirtiest LEB into the GC head LEB.
1169 *
1170 * This function also runs the commit which causes the TNC updates from
1171 * size-recovery and orphans to be written to the flash. That is important to
1172 * ensure correct replay order for subsequent mounts.
1173 *
1174 * This function returns %0 on success and a negative error code on failure.
1175 */
1176int ubifs_rcvry_gc_commit(struct ubifs_info *c)
1177{
1178	struct ubifs_wbuf *wbuf = &c->jheads[GCHD].wbuf;
1179	struct ubifs_lprops lp;
1180	int err;
1181
1182	dbg_rcvry("GC head LEB %d, offs %d", wbuf->lnum, wbuf->offs);
1183
1184	c->gc_lnum = -1;
1185	if (wbuf->lnum == -1 || wbuf->offs == c->leb_size)
1186		return grab_empty_leb(c);
1187
1188	err = ubifs_find_dirty_leb(c, &lp, wbuf->offs, 2);
1189	if (err) {
1190		if (err != -ENOSPC)
1191			return err;
1192
1193		dbg_rcvry("could not find a dirty LEB");
1194		return grab_empty_leb(c);
1195	}
1196
1197	ubifs_assert(!(lp.flags & LPROPS_INDEX));
1198	ubifs_assert(lp.free + lp.dirty >= wbuf->offs);
1199
1200	/*
1201	 * We run the commit before garbage collection otherwise subsequent
1202	 * mounts will see the GC and orphan deletion in a different order.
1203	 */
1204	dbg_rcvry("committing");
1205	err = ubifs_run_commit(c);
1206	if (err)
1207		return err;
1208
1209	dbg_rcvry("GC'ing LEB %d", lp.lnum);
1210	mutex_lock_nested(&wbuf->io_mutex, wbuf->jhead);
1211	err = ubifs_garbage_collect_leb(c, &lp);
1212	if (err >= 0) {
1213		int err2 = ubifs_wbuf_sync_nolock(wbuf);
1214
1215		if (err2)
1216			err = err2;
1217	}
1218	mutex_unlock(&wbuf->io_mutex);
1219	if (err < 0) {
1220		dbg_err("GC failed, error %d", err);
1221		if (err == -EAGAIN)
1222			err = -EINVAL;
1223		return err;
1224	}
1225
1226	ubifs_assert(err == LEB_RETAINED);
1227	if (err != LEB_RETAINED)
1228		return -EINVAL;
1229
1230	err = ubifs_leb_unmap(c, c->gc_lnum);
1231	if (err)
1232		return err;
1233
1234	dbg_rcvry("allocated LEB %d for GC", lp.lnum);
1235	return 0;
1236}
1237
1238/**
1239 * struct size_entry - inode size information for recovery.
1240 * @rb: link in the RB-tree of sizes
1241 * @inum: inode number
1242 * @i_size: size on inode
1243 * @d_size: maximum size based on data nodes
1244 * @exists: indicates whether the inode exists
1245 * @inode: inode if pinned in memory awaiting rw mode to fix it
1246 */
1247struct size_entry {
1248	struct rb_node rb;
1249	ino_t inum;
1250	loff_t i_size;
1251	loff_t d_size;
1252	int exists;
1253	struct inode *inode;
1254};
1255
1256/**
1257 * add_ino - add an entry to the size tree.
1258 * @c: UBIFS file-system description object
1259 * @inum: inode number
1260 * @i_size: size on inode
1261 * @d_size: maximum size based on data nodes
1262 * @exists: indicates whether the inode exists
1263 */
1264static int add_ino(struct ubifs_info *c, ino_t inum, loff_t i_size,
1265		   loff_t d_size, int exists)
1266{
1267	struct rb_node **p = &c->size_tree.rb_node, *parent = NULL;
1268	struct size_entry *e;
1269
1270	while (*p) {
1271		parent = *p;
1272		e = rb_entry(parent, struct size_entry, rb);
1273		if (inum < e->inum)
1274			p = &(*p)->rb_left;
1275		else
1276			p = &(*p)->rb_right;
1277	}
1278
1279	e = kzalloc(sizeof(struct size_entry), GFP_KERNEL);
1280	if (!e)
1281		return -ENOMEM;
1282
1283	e->inum = inum;
1284	e->i_size = i_size;
1285	e->d_size = d_size;
1286	e->exists = exists;
1287
1288	rb_link_node(&e->rb, parent, p);
1289	rb_insert_color(&e->rb, &c->size_tree);
1290
1291	return 0;
1292}
1293
1294/**
1295 * find_ino - find an entry on the size tree.
1296 * @c: UBIFS file-system description object
1297 * @inum: inode number
1298 */
1299static struct size_entry *find_ino(struct ubifs_info *c, ino_t inum)
1300{
1301	struct rb_node *p = c->size_tree.rb_node;
1302	struct size_entry *e;
1303
1304	while (p) {
1305		e = rb_entry(p, struct size_entry, rb);
1306		if (inum < e->inum)
1307			p = p->rb_left;
1308		else if (inum > e->inum)
1309			p = p->rb_right;
1310		else
1311			return e;
1312	}
1313	return NULL;
1314}
1315
1316/**
1317 * remove_ino - remove an entry from the size tree.
1318 * @c: UBIFS file-system description object
1319 * @inum: inode number
1320 */
1321static void remove_ino(struct ubifs_info *c, ino_t inum)
1322{
1323	struct size_entry *e = find_ino(c, inum);
1324
1325	if (!e)
1326		return;
1327	rb_erase(&e->rb, &c->size_tree);
1328	kfree(e);
1329}
1330
1331/**
1332 * ubifs_destroy_size_tree - free resources related to the size tree.
1333 * @c: UBIFS file-system description object
1334 */
1335void ubifs_destroy_size_tree(struct ubifs_info *c)
1336{
1337	struct rb_node *this = c->size_tree.rb_node;
1338	struct size_entry *e;
1339
1340	while (this) {
1341		if (this->rb_left) {
1342			this = this->rb_left;
1343			continue;
1344		} else if (this->rb_right) {
1345			this = this->rb_right;
1346			continue;
1347		}
1348		e = rb_entry(this, struct size_entry, rb);
1349		if (e->inode)
1350			iput(e->inode);
1351		this = rb_parent(this);
1352		if (this) {
1353			if (this->rb_left == &e->rb)
1354				this->rb_left = NULL;
1355			else
1356				this->rb_right = NULL;
1357		}
1358		kfree(e);
1359	}
 
1360	c->size_tree = RB_ROOT;
1361}
1362
1363/**
1364 * ubifs_recover_size_accum - accumulate inode sizes for recovery.
1365 * @c: UBIFS file-system description object
1366 * @key: node key
1367 * @deletion: node is for a deletion
1368 * @new_size: inode size
1369 *
1370 * This function has two purposes:
1371 *     1) to ensure there are no data nodes that fall outside the inode size
1372 *     2) to ensure there are no data nodes for inodes that do not exist
1373 * To accomplish those purposes, a rb-tree is constructed containing an entry
1374 * for each inode number in the journal that has not been deleted, and recording
1375 * the size from the inode node, the maximum size of any data node (also altered
1376 * by truncations) and a flag indicating a inode number for which no inode node
1377 * was present in the journal.
1378 *
1379 * Note that there is still the possibility that there are data nodes that have
1380 * been committed that are beyond the inode size, however the only way to find
1381 * them would be to scan the entire index. Alternatively, some provision could
1382 * be made to record the size of inodes at the start of commit, which would seem
1383 * very cumbersome for a scenario that is quite unlikely and the only negative
1384 * consequence of which is wasted space.
1385 *
1386 * This functions returns %0 on success and a negative error code on failure.
1387 */
1388int ubifs_recover_size_accum(struct ubifs_info *c, union ubifs_key *key,
1389			     int deletion, loff_t new_size)
1390{
1391	ino_t inum = key_inum(c, key);
1392	struct size_entry *e;
1393	int err;
1394
1395	switch (key_type(c, key)) {
1396	case UBIFS_INO_KEY:
1397		if (deletion)
1398			remove_ino(c, inum);
1399		else {
1400			e = find_ino(c, inum);
1401			if (e) {
1402				e->i_size = new_size;
1403				e->exists = 1;
1404			} else {
1405				err = add_ino(c, inum, new_size, 0, 1);
1406				if (err)
1407					return err;
1408			}
1409		}
1410		break;
1411	case UBIFS_DATA_KEY:
1412		e = find_ino(c, inum);
1413		if (e) {
1414			if (new_size > e->d_size)
1415				e->d_size = new_size;
1416		} else {
1417			err = add_ino(c, inum, 0, new_size, 0);
1418			if (err)
1419				return err;
1420		}
1421		break;
1422	case UBIFS_TRUN_KEY:
1423		e = find_ino(c, inum);
1424		if (e)
1425			e->d_size = new_size;
1426		break;
1427	}
1428	return 0;
1429}
1430
1431/**
1432 * fix_size_in_place - fix inode size in place on flash.
1433 * @c: UBIFS file-system description object
1434 * @e: inode size information for recovery
1435 */
1436static int fix_size_in_place(struct ubifs_info *c, struct size_entry *e)
1437{
1438	struct ubifs_ino_node *ino = c->sbuf;
1439	unsigned char *p;
1440	union ubifs_key key;
1441	int err, lnum, offs, len;
1442	loff_t i_size;
1443	uint32_t crc;
1444
1445	/* Locate the inode node LEB number and offset */
1446	ino_key_init(c, &key, e->inum);
1447	err = ubifs_tnc_locate(c, &key, ino, &lnum, &offs);
1448	if (err)
1449		goto out;
1450	/*
1451	 * If the size recorded on the inode node is greater than the size that
1452	 * was calculated from nodes in the journal then don't change the inode.
1453	 */
1454	i_size = le64_to_cpu(ino->size);
1455	if (i_size >= e->d_size)
1456		return 0;
1457	/* Read the LEB */
1458	err = ubifs_leb_read(c, lnum, c->sbuf, 0, c->leb_size, 1);
1459	if (err)
1460		goto out;
1461	/* Change the size field and recalculate the CRC */
1462	ino = c->sbuf + offs;
1463	ino->size = cpu_to_le64(e->d_size);
1464	len = le32_to_cpu(ino->ch.len);
1465	crc = crc32(UBIFS_CRC32_INIT, (void *)ino + 8, len - 8);
1466	ino->ch.crc = cpu_to_le32(crc);
1467	/* Work out where data in the LEB ends and free space begins */
1468	p = c->sbuf;
1469	len = c->leb_size - 1;
1470	while (p[len] == 0xff)
1471		len -= 1;
1472	len = ALIGN(len + 1, c->min_io_size);
1473	/* Atomically write the fixed LEB back again */
1474	err = ubifs_leb_change(c, lnum, c->sbuf, len, UBI_UNKNOWN);
1475	if (err)
1476		goto out;
1477	dbg_rcvry("inode %lu at %d:%d size %lld -> %lld",
1478		  (unsigned long)e->inum, lnum, offs, i_size, e->d_size);
1479	return 0;
1480
1481out:
1482	ubifs_warn("inode %lu failed to fix size %lld -> %lld error %d",
1483		   (unsigned long)e->inum, e->i_size, e->d_size, err);
1484	return err;
1485}
1486
1487/**
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1488 * ubifs_recover_size - recover inode size.
1489 * @c: UBIFS file-system description object
 
1490 *
1491 * This function attempts to fix inode size discrepancies identified by the
1492 * 'ubifs_recover_size_accum()' function.
1493 *
1494 * This functions returns %0 on success and a negative error code on failure.
1495 */
1496int ubifs_recover_size(struct ubifs_info *c)
1497{
1498	struct rb_node *this = rb_first(&c->size_tree);
1499
1500	while (this) {
1501		struct size_entry *e;
1502		int err;
1503
1504		e = rb_entry(this, struct size_entry, rb);
 
 
 
1505		if (!e->exists) {
1506			union ubifs_key key;
1507
1508			ino_key_init(c, &key, e->inum);
1509			err = ubifs_tnc_lookup(c, &key, c->sbuf);
1510			if (err && err != -ENOENT)
1511				return err;
1512			if (err == -ENOENT) {
1513				/* Remove data nodes that have no inode */
1514				dbg_rcvry("removing ino %lu",
1515					  (unsigned long)e->inum);
1516				err = ubifs_tnc_remove_ino(c, e->inum);
1517				if (err)
1518					return err;
1519			} else {
1520				struct ubifs_ino_node *ino = c->sbuf;
1521
1522				e->exists = 1;
1523				e->i_size = le64_to_cpu(ino->size);
1524			}
1525		}
1526
1527		if (e->exists && e->i_size < e->d_size) {
1528			if (c->ro_mount) {
1529				/* Fix the inode size and pin it in memory */
1530				struct inode *inode;
1531				struct ubifs_inode *ui;
1532
1533				ubifs_assert(!e->inode);
1534
1535				inode = ubifs_iget(c->vfs_sb, e->inum);
1536				if (IS_ERR(inode))
1537					return PTR_ERR(inode);
1538
1539				ui = ubifs_inode(inode);
1540				if (inode->i_size < e->d_size) {
1541					dbg_rcvry("ino %lu size %lld -> %lld",
1542						  (unsigned long)e->inum,
1543						  inode->i_size, e->d_size);
1544					inode->i_size = e->d_size;
1545					ui->ui_size = e->d_size;
1546					ui->synced_i_size = e->d_size;
1547					e->inode = inode;
1548					this = rb_next(this);
1549					continue;
1550				}
1551				iput(inode);
1552			} else {
1553				/* Fix the size in place */
1554				err = fix_size_in_place(c, e);
1555				if (err)
1556					return err;
1557				if (e->inode)
1558					iput(e->inode);
 
 
 
 
1559			}
1560		}
1561
1562		this = rb_next(this);
1563		rb_erase(&e->rb, &c->size_tree);
1564		kfree(e);
1565	}
1566
1567	return 0;
1568}