src/kernel/linux/v4.19/fs/ubifs/replay.c

/*
 * This file is part of UBIFS.
 *
 * Copyright (C) 2006-2008 Nokia Corporation.
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 as published by
 * the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
 * more details.
 *
 * You should have received a copy of the GNU General Public License along with
 * this program; if not, write to the Free Software Foundation, Inc., 51
 * Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
 *
 * Authors: Adrian Hunter
 *          Artem Bityutskiy (Битюцкий Артём)
 */

/*
 * This file contains journal replay code. It runs when the file-system is being
 * mounted and requires no locking.
 *
 * The larger is the journal, the longer it takes to scan it, so the longer it
 * takes to mount UBIFS. This is why the journal has limited size which may be
 * changed depending on the system requirements. But a larger journal gives
 * faster I/O speed because it writes the index less frequently. So this is a
 * trade-off. Also, the journal is indexed by the in-memory index (TNC), so the
 * larger is the journal, the more memory its index may consume.
 */

#include "ubifs.h"
#include <linux/list_sort.h>

/**
 * struct replay_entry - replay list entry.
 * @lnum: logical eraseblock number of the node
 * @offs: node offset
 * @len: node length
 * @deletion: non-zero if this entry corresponds to a node deletion
 * @sqnum: node sequence number
 * @list: links the replay list
 * @key: node key
 * @nm: directory entry name
 * @old_size: truncation old size
 * @new_size: truncation new size
 *
 * The replay process first scans all buds and builds the replay list, then
 * sorts the replay list in nodes sequence number order, and then inserts all
 * the replay entries to the TNC.
 */
struct replay_entry {
	int lnum;
	int offs;
	int len;
	unsigned int deletion:1;
	unsigned long long sqnum;
	struct list_head list;
	union ubifs_key key;
	union {
		struct fscrypt_name nm;
		struct {
			loff_t old_size;
			loff_t new_size;
		};
	};
};

/**
 * struct bud_entry - entry in the list of buds to replay.
 * @list: next bud in the list
 * @bud: bud description object
 * @sqnum: reference node sequence number
 * @free: free bytes in the bud
 * @dirty: dirty bytes in the bud
 */
struct bud_entry {
	struct list_head list;
	struct ubifs_bud *bud;
	unsigned long long sqnum;
	int free;
	int dirty;
};

/**
 * set_bud_lprops - set free and dirty space used by a bud.
 * @c: UBIFS file-system description object
 * @b: bud entry which describes the bud
 *
 * This function makes sure the LEB properties of bud @b are set correctly
 * after the replay. Returns zero in case of success and a negative error code
 * in case of failure.
 */
static int set_bud_lprops(struct ubifs_info *c, struct bud_entry *b)
{
	const struct ubifs_lprops *lp;
	int err = 0, dirty;

	ubifs_get_lprops(c);

	lp = ubifs_lpt_lookup_dirty(c, b->bud->lnum);
	if (IS_ERR(lp)) {
		err = PTR_ERR(lp);
		goto out;
	}

	dirty = lp->dirty;
	if (b->bud->start == 0 && (lp->free != c->leb_size || lp->dirty != 0)) {
		/*
		 * The LEB was added to the journal with a starting offset of
		 * zero which means the LEB must have been empty. The LEB
		 * property values should be @lp->free == @c->leb_size and
		 * @lp->dirty == 0, but that is not the case. The reason is that
		 * the LEB had been garbage collected before it became the bud,
		 * and there was not commit inbetween. The garbage collector
		 * resets the free and dirty space without recording it
		 * anywhere except lprops, so if there was no commit then
		 * lprops does not have that information.
		 *
		 * We do not need to adjust free space because the scan has told
		 * us the exact value which is recorded in the replay entry as
		 * @b->free.
		 *
		 * However we do need to subtract from the dirty space the
		 * amount of space that the garbage collector reclaimed, which
		 * is the whole LEB minus the amount of space that was free.
		 */
		dbg_mnt("bud LEB %d was GC'd (%d free, %d dirty)", b->bud->lnum,
			lp->free, lp->dirty);
		dbg_gc("bud LEB %d was GC'd (%d free, %d dirty)", b->bud->lnum,
			lp->free, lp->dirty);
		dirty -= c->leb_size - lp->free;
		/*
		 * If the replay order was perfect the dirty space would now be
		 * zero. The order is not perfect because the journal heads
		 * race with each other. This is not a problem but is does mean
		 * that the dirty space may temporarily exceed c->leb_size
		 * during the replay.
		 */
		if (dirty != 0)
			dbg_mnt("LEB %d lp: %d free %d dirty replay: %d free %d dirty",
				b->bud->lnum, lp->free, lp->dirty, b->free,
				b->dirty);
	}
	lp = ubifs_change_lp(c, lp, b->free, dirty + b->dirty,
			     lp->flags | LPROPS_TAKEN, 0);
	if (IS_ERR(lp)) {
		err = PTR_ERR(lp);
		goto out;
	}

	/* Make sure the journal head points to the latest bud */
	err = ubifs_wbuf_seek_nolock(&c->jheads[b->bud->jhead].wbuf,
				     b->bud->lnum, c->leb_size - b->free);

out:
	ubifs_release_lprops(c);
	return err;
}

/**
 * set_buds_lprops - set free and dirty space for all replayed buds.
 * @c: UBIFS file-system description object
 *
 * This function sets LEB properties for all replayed buds. Returns zero in
 * case of success and a negative error code in case of failure.
 */
static int set_buds_lprops(struct ubifs_info *c)
{
	struct bud_entry *b;
	int err;

	list_for_each_entry(b, &c->replay_buds, list) {
		err = set_bud_lprops(c, b);
		if (err)
			return err;
	}

	return 0;
}

/**
 * trun_remove_range - apply a replay entry for a truncation to the TNC.
 * @c: UBIFS file-system description object
 * @r: replay entry of truncation
 */
static int trun_remove_range(struct ubifs_info *c, struct replay_entry *r)
{
	unsigned min_blk, max_blk;
	union ubifs_key min_key, max_key;
	ino_t ino;

	min_blk = r->new_size / UBIFS_BLOCK_SIZE;
	if (r->new_size & (UBIFS_BLOCK_SIZE - 1))
		min_blk += 1;

	max_blk = r->old_size / UBIFS_BLOCK_SIZE;
	if ((r->old_size & (UBIFS_BLOCK_SIZE - 1)) == 0)
		max_blk -= 1;

	ino = key_inum(c, &r->key);

	data_key_init(c, &min_key, ino, min_blk);
	data_key_init(c, &max_key, ino, max_blk);

	return ubifs_tnc_remove_range(c, &min_key, &max_key);
}

/**
 * inode_still_linked - check whether inode in question will be re-linked.
 * @c: UBIFS file-system description object
 * @rino: replay entry to test
 *
 * O_TMPFILE files can be re-linked, this means link count goes from 0 to 1.
 * This case needs special care, otherwise all references to the inode will
 * be removed upon the first replay entry of an inode with link count 0
 * is found.
 */
static bool inode_still_linked(struct ubifs_info *c, struct replay_entry *rino)
{
	struct replay_entry *r;

	ubifs_assert(c, rino->deletion);
	ubifs_assert(c, key_type(c, &rino->key) == UBIFS_INO_KEY);

	/*
	 * Find the most recent entry for the inode behind @rino and check
	 * whether it is a deletion.
	 */
	list_for_each_entry_reverse(r, &c->replay_list, list) {
		ubifs_assert(c, r->sqnum >= rino->sqnum);
		if (key_inum(c, &r->key) == key_inum(c, &rino->key))
			return r->deletion == 0;

	}

	ubifs_assert(c, 0);
	return false;
}

/**
 * apply_replay_entry - apply a replay entry to the TNC.
 * @c: UBIFS file-system description object
 * @r: replay entry to apply
 *
 * Apply a replay entry to the TNC.
 */
static int apply_replay_entry(struct ubifs_info *c, struct replay_entry *r)
{
	int err;

	dbg_mntk(&r->key, "LEB %d:%d len %d deletion %d sqnum %llu key ",
		 r->lnum, r->offs, r->len, r->deletion, r->sqnum);

	if (is_hash_key(c, &r->key)) {
		if (r->deletion)
			err = ubifs_tnc_remove_nm(c, &r->key, &r->nm);
		else
			err = ubifs_tnc_add_nm(c, &r->key, r->lnum, r->offs,
					       r->len, &r->nm);
	} else {
		if (r->deletion)
			switch (key_type(c, &r->key)) {
			case UBIFS_INO_KEY:
			{
				ino_t inum = key_inum(c, &r->key);

				if (inode_still_linked(c, r)) {
					err = 0;
					break;
				}

				err = ubifs_tnc_remove_ino(c, inum);
				break;
			}
			case UBIFS_TRUN_KEY:
				err = trun_remove_range(c, r);
				break;
			default:
				err = ubifs_tnc_remove(c, &r->key);
				break;
			}
		else
			err = ubifs_tnc_add(c, &r->key, r->lnum, r->offs,
					    r->len);
		if (err)
			return err;

		if (c->need_recovery)
			err = ubifs_recover_size_accum(c, &r->key, r->deletion,
						       r->new_size);
	}

	return err;
}

/**
 * replay_entries_cmp - compare 2 replay entries.
 * @priv: UBIFS file-system description object
 * @a: first replay entry
 * @b: second replay entry
 *
 * This is a comparios function for 'list_sort()' which compares 2 replay
 * entries @a and @b by comparing their sequence numer.  Returns %1 if @a has
 * greater sequence number and %-1 otherwise.
 */
static int replay_entries_cmp(void *priv, struct list_head *a,
			      struct list_head *b)
{
	struct ubifs_info *c = priv;
	struct replay_entry *ra, *rb;

	cond_resched();
	if (a == b)
		return 0;

	ra = list_entry(a, struct replay_entry, list);
	rb = list_entry(b, struct replay_entry, list);
	ubifs_assert(c, ra->sqnum != rb->sqnum);
	if (ra->sqnum > rb->sqnum)
		return 1;
	return -1;
}

/**
 * apply_replay_list - apply the replay list to the TNC.
 * @c: UBIFS file-system description object
 *
 * Apply all entries in the replay list to the TNC. Returns zero in case of
 * success and a negative error code in case of failure.
 */
static int apply_replay_list(struct ubifs_info *c)
{
	struct replay_entry *r;
	int err;

	list_sort(c, &c->replay_list, &replay_entries_cmp);

	list_for_each_entry(r, &c->replay_list, list) {
		cond_resched();

		err = apply_replay_entry(c, r);
		if (err)
			return err;
	}

	return 0;
}

/**
 * destroy_replay_list - destroy the replay.
 * @c: UBIFS file-system description object
 *
 * Destroy the replay list.
 */
static void destroy_replay_list(struct ubifs_info *c)
{
	struct replay_entry *r, *tmp;

	list_for_each_entry_safe(r, tmp, &c->replay_list, list) {
		if (is_hash_key(c, &r->key))
			kfree(fname_name(&r->nm));
		list_del(&r->list);
		kfree(r);
	}
}

/**
 * insert_node - insert a node to the replay list
 * @c: UBIFS file-system description object
 * @lnum: node logical eraseblock number
 * @offs: node offset
 * @len: node length
 * @key: node key
 * @sqnum: sequence number
 * @deletion: non-zero if this is a deletion
 * @used: number of bytes in use in a LEB
 * @old_size: truncation old size
 * @new_size: truncation new size
 *
 * This function inserts a scanned non-direntry node to the replay list. The
 * replay list contains @struct replay_entry elements, and we sort this list in
 * sequence number order before applying it. The replay list is applied at the
 * very end of the replay process. Since the list is sorted in sequence number
 * order, the older modifications are applied first. This function returns zero
 * in case of success and a negative error code in case of failure.
 */
static int insert_node(struct ubifs_info *c, int lnum, int offs, int len,
		       union ubifs_key *key, unsigned long long sqnum,
		       int deletion, int *used, loff_t old_size,
		       loff_t new_size)
{
	struct replay_entry *r;

	dbg_mntk(key, "add LEB %d:%d, key ", lnum, offs);

	if (key_inum(c, key) >= c->highest_inum)
		c->highest_inum = key_inum(c, key);

	r = kzalloc(sizeof(struct replay_entry), GFP_KERNEL);
	if (!r)
		return -ENOMEM;

	if (!deletion)
		*used += ALIGN(len, 8);
	r->lnum = lnum;
	r->offs = offs;
	r->len = len;
	r->deletion = !!deletion;
	r->sqnum = sqnum;
	key_copy(c, key, &r->key);
	r->old_size = old_size;
	r->new_size = new_size;

	list_add_tail(&r->list, &c->replay_list);
	return 0;
}

/**
 * insert_dent - insert a directory entry node into the replay list.
 * @c: UBIFS file-system description object
 * @lnum: node logical eraseblock number
 * @offs: node offset
 * @len: node length
 * @key: node key
 * @name: directory entry name
 * @nlen: directory entry name length
 * @sqnum: sequence number
 * @deletion: non-zero if this is a deletion
 * @used: number of bytes in use in a LEB
 *
 * This function inserts a scanned directory entry node or an extended
 * attribute entry to the replay list. Returns zero in case of success and a
 * negative error code in case of failure.
 */
static int insert_dent(struct ubifs_info *c, int lnum, int offs, int len,
		       union ubifs_key *key, const char *name, int nlen,
		       unsigned long long sqnum, int deletion, int *used)
{
	struct replay_entry *r;
	char *nbuf;

	dbg_mntk(key, "add LEB %d:%d, key ", lnum, offs);
	if (key_inum(c, key) >= c->highest_inum)
		c->highest_inum = key_inum(c, key);

	r = kzalloc(sizeof(struct replay_entry), GFP_KERNEL);
	if (!r)
		return -ENOMEM;

	nbuf = kmalloc(nlen + 1, GFP_KERNEL);
	if (!nbuf) {
		kfree(r);
		return -ENOMEM;
	}

	if (!deletion)
		*used += ALIGN(len, 8);
	r->lnum = lnum;
	r->offs = offs;
	r->len = len;
	r->deletion = !!deletion;
	r->sqnum = sqnum;
	key_copy(c, key, &r->key);
	fname_len(&r->nm) = nlen;
	memcpy(nbuf, name, nlen);
	nbuf[nlen] = '\0';
	fname_name(&r->nm) = nbuf;

	list_add_tail(&r->list, &c->replay_list);
	return 0;
}

/**
 * ubifs_validate_entry - validate directory or extended attribute entry node.
 * @c: UBIFS file-system description object
 * @dent: the node to validate
 *
 * This function validates directory or extended attribute entry node @dent.
 * Returns zero if the node is all right and a %-EINVAL if not.
 */
int ubifs_validate_entry(struct ubifs_info *c,
			 const struct ubifs_dent_node *dent)
{
	int key_type = key_type_flash(c, dent->key);
	int nlen = le16_to_cpu(dent->nlen);

	if (le32_to_cpu(dent->ch.len) != nlen + UBIFS_DENT_NODE_SZ + 1 ||
	    dent->type >= UBIFS_ITYPES_CNT ||
	    nlen > UBIFS_MAX_NLEN || dent->name[nlen] != 0 ||
	    (key_type == UBIFS_XENT_KEY && strnlen(dent->name, nlen) != nlen) ||
	    le64_to_cpu(dent->inum) > MAX_INUM) {
		ubifs_err(c, "bad %s node", key_type == UBIFS_DENT_KEY ?
			  "directory entry" : "extended attribute entry");
		return -EINVAL;
	}

	if (key_type != UBIFS_DENT_KEY && key_type != UBIFS_XENT_KEY) {
		ubifs_err(c, "bad key type %d", key_type);
		return -EINVAL;
	}

	return 0;
}

/**
 * is_last_bud - check if the bud is the last in the journal head.
 * @c: UBIFS file-system description object
 * @bud: bud description object
 *
 * This function checks if bud @bud is the last bud in its journal head. This
 * information is then used by 'replay_bud()' to decide whether the bud can
 * have corruptions or not. Indeed, only last buds can be corrupted by power
 * cuts. Returns %1 if this is the last bud, and %0 if not.
 */
static int is_last_bud(struct ubifs_info *c, struct ubifs_bud *bud)
{
	struct ubifs_jhead *jh = &c->jheads[bud->jhead];
	struct ubifs_bud *next;
	uint32_t data;
	int err;

	if (list_is_last(&bud->list, &jh->buds_list))
		return 1;

	/*
	 * The following is a quirk to make sure we work correctly with UBIFS
	 * images used with older UBIFS.
	 *
	 * Normally, the last bud will be the last in the journal head's list
	 * of bud. However, there is one exception if the UBIFS image belongs
	 * to older UBIFS. This is fairly unlikely: one would need to use old
	 * UBIFS, then have a power cut exactly at the right point, and then
	 * try to mount this image with new UBIFS.
	 *
	 * The exception is: it is possible to have 2 buds A and B, A goes
	 * before B, and B is the last, bud B is contains no data, and bud A is
	 * corrupted at the end. The reason is that in older versions when the
	 * journal code switched the next bud (from A to B), it first added a
	 * log reference node for the new bud (B), and only after this it
	 * synchronized the write-buffer of current bud (A). But later this was
	 * changed and UBIFS started to always synchronize the write-buffer of
	 * the bud (A) before writing the log reference for the new bud (B).
	 *
	 * But because older UBIFS always synchronized A's write-buffer before
	 * writing to B, we can recognize this exceptional situation but
	 * checking the contents of bud B - if it is empty, then A can be
	 * treated as the last and we can recover it.
	 *
	 * TODO: remove this piece of code in a couple of years (today it is
	 * 16.05.2011).
	 */
	next = list_entry(bud->list.next, struct ubifs_bud, list);
	if (!list_is_last(&next->list, &jh->buds_list))
		return 0;

	err = ubifs_leb_read(c, next->lnum, (char *)&data, next->start, 4, 1);
	if (err)
		return 0;

	return data == 0xFFFFFFFF;
}

/**
 * replay_bud - replay a bud logical eraseblock.
 * @c: UBIFS file-system description object
 * @b: bud entry which describes the bud
 *
 * This function replays bud @bud, recovers it if needed, and adds all nodes
 * from this bud to the replay list. Returns zero in case of success and a
 * negative error code in case of failure.
 */
static int replay_bud(struct ubifs_info *c, struct bud_entry *b)
{
	int is_last = is_last_bud(c, b->bud);
	int err = 0, used = 0, lnum = b->bud->lnum, offs = b->bud->start;
	struct ubifs_scan_leb *sleb;
	struct ubifs_scan_node *snod;

	dbg_mnt("replay bud LEB %d, head %d, offs %d, is_last %d",
		lnum, b->bud->jhead, offs, is_last);

	if (c->need_recovery && is_last)
		/*
		 * Recover only last LEBs in the journal heads, because power
		 * cuts may cause corruptions only in these LEBs, because only
		 * these LEBs could possibly be written to at the power cut
		 * time.
		 */
		sleb = ubifs_recover_leb(c, lnum, offs, c->sbuf, b->bud->jhead);
	else
		sleb = ubifs_scan(c, lnum, offs, c->sbuf, 0);
	if (IS_ERR(sleb))
		return PTR_ERR(sleb);

	/*
	 * The bud does not have to start from offset zero - the beginning of
	 * the 'lnum' LEB may contain previously committed data. One of the
	 * things we have to do in replay is to correctly update lprops with
	 * newer information about this LEB.
	 *
	 * At this point lprops thinks that this LEB has 'c->leb_size - offs'
	 * bytes of free space because it only contain information about
	 * committed data.
	 *
	 * But we know that real amount of free space is 'c->leb_size -
	 * sleb->endpt', and the space in the 'lnum' LEB between 'offs' and
	 * 'sleb->endpt' is used by bud data. We have to correctly calculate
	 * how much of these data are dirty and update lprops with this
	 * information.
	 *
	 * The dirt in that LEB region is comprised of padding nodes, deletion
	 * nodes, truncation nodes and nodes which are obsoleted by subsequent
	 * nodes in this LEB. So instead of calculating clean space, we
	 * calculate used space ('used' variable).
	 */

	list_for_each_entry(snod, &sleb->nodes, list) {
		int deletion = 0;

		cond_resched();

		if (snod->sqnum >= SQNUM_WATERMARK) {
			ubifs_err(c, "file system's life ended");
			goto out_dump;
		}

		if (snod->sqnum > c->max_sqnum)
			c->max_sqnum = snod->sqnum;

		switch (snod->type) {
		case UBIFS_INO_NODE:
		{
			struct ubifs_ino_node *ino = snod->node;
			loff_t new_size = le64_to_cpu(ino->size);

			if (le32_to_cpu(ino->nlink) == 0)
				deletion = 1;
			err = insert_node(c, lnum, snod->offs, snod->len,
					  &snod->key, snod->sqnum, deletion,
					  &used, 0, new_size);
			break;
		}
		case UBIFS_DATA_NODE:
		{
			struct ubifs_data_node *dn = snod->node;
			loff_t new_size = le32_to_cpu(dn->size) +
					  key_block(c, &snod->key) *
					  UBIFS_BLOCK_SIZE;

			err = insert_node(c, lnum, snod->offs, snod->len,
					  &snod->key, snod->sqnum, deletion,
					  &used, 0, new_size);
			break;
		}
		case UBIFS_DENT_NODE:
		case UBIFS_XENT_NODE:
		{
			struct ubifs_dent_node *dent = snod->node;

			err = ubifs_validate_entry(c, dent);
			if (err)
				goto out_dump;

			err = insert_dent(c, lnum, snod->offs, snod->len,
					  &snod->key, dent->name,
					  le16_to_cpu(dent->nlen), snod->sqnum,
					  !le64_to_cpu(dent->inum), &used);
			break;
		}
		case UBIFS_TRUN_NODE:
		{
			struct ubifs_trun_node *trun = snod->node;
			loff_t old_size = le64_to_cpu(trun->old_size);
			loff_t new_size = le64_to_cpu(trun->new_size);
			union ubifs_key key;

			/* Validate truncation node */
			if (old_size < 0 || old_size > c->max_inode_sz ||
			    new_size < 0 || new_size > c->max_inode_sz ||
			    old_size <= new_size) {
				ubifs_err(c, "bad truncation node");
				goto out_dump;
			}

			/*
			 * Create a fake truncation key just to use the same
			 * functions which expect nodes to have keys.
			 */
			trun_key_init(c, &key, le32_to_cpu(trun->inum));
			err = insert_node(c, lnum, snod->offs, snod->len,
					  &key, snod->sqnum, 1, &used,
					  old_size, new_size);
			break;
		}
		default:
			ubifs_err(c, "unexpected node type %d in bud LEB %d:%d",
				  snod->type, lnum, snod->offs);
			err = -EINVAL;
			goto out_dump;
		}
		if (err)
			goto out;
	}

	ubifs_assert(c, ubifs_search_bud(c, lnum));
	ubifs_assert(c, sleb->endpt - offs >= used);
	ubifs_assert(c, sleb->endpt % c->min_io_size == 0);

	b->dirty = sleb->endpt - offs - used;
	b->free = c->leb_size - sleb->endpt;
	dbg_mnt("bud LEB %d replied: dirty %d, free %d",
		lnum, b->dirty, b->free);

out:
	ubifs_scan_destroy(sleb);
	return err;

out_dump:
	ubifs_err(c, "bad node is at LEB %d:%d", lnum, snod->offs);
	ubifs_dump_node(c, snod->node);
	ubifs_scan_destroy(sleb);
	return -EINVAL;
}

/**
 * replay_buds - replay all buds.
 * @c: UBIFS file-system description object
 *
 * This function returns zero in case of success and a negative error code in
 * case of failure.
 */
static int replay_buds(struct ubifs_info *c)
{
	struct bud_entry *b;
	int err;
	unsigned long long prev_sqnum = 0;

	list_for_each_entry(b, &c->replay_buds, list) {
		err = replay_bud(c, b);
		if (err)
			return err;

		ubifs_assert(c, b->sqnum > prev_sqnum);
		prev_sqnum = b->sqnum;
	}

	return 0;
}

/**
 * destroy_bud_list - destroy the list of buds to replay.
 * @c: UBIFS file-system description object
 */
static void destroy_bud_list(struct ubifs_info *c)
{
	struct bud_entry *b;

	while (!list_empty(&c->replay_buds)) {
		b = list_entry(c->replay_buds.next, struct bud_entry, list);
		list_del(&b->list);
		kfree(b);
	}
}

/**
 * add_replay_bud - add a bud to the list of buds to replay.
 * @c: UBIFS file-system description object
 * @lnum: bud logical eraseblock number to replay
 * @offs: bud start offset
 * @jhead: journal head to which this bud belongs
 * @sqnum: reference node sequence number
 *
 * This function returns zero in case of success and a negative error code in
 * case of failure.
 */
static int add_replay_bud(struct ubifs_info *c, int lnum, int offs, int jhead,
			  unsigned long long sqnum)
{
	struct ubifs_bud *bud;
	struct bud_entry *b;

	dbg_mnt("add replay bud LEB %d:%d, head %d", lnum, offs, jhead);

	bud = kmalloc(sizeof(struct ubifs_bud), GFP_KERNEL);
	if (!bud)
		return -ENOMEM;

	b = kmalloc(sizeof(struct bud_entry), GFP_KERNEL);
	if (!b) {
		kfree(bud);
		return -ENOMEM;
	}

	bud->lnum = lnum;
	bud->start = offs;
	bud->jhead = jhead;
	ubifs_add_bud(c, bud);

	b->bud = bud;
	b->sqnum = sqnum;
	list_add_tail(&b->list, &c->replay_buds);

	return 0;
}

/**
 * validate_ref - validate a reference node.
 * @c: UBIFS file-system description object
 * @ref: the reference node to validate
 * @ref_lnum: LEB number of the reference node
 * @ref_offs: reference node offset
 *
 * This function returns %1 if a bud reference already exists for the LEB. %0 is
 * returned if the reference node is new, otherwise %-EINVAL is returned if
 * validation failed.
 */
static int validate_ref(struct ubifs_info *c, const struct ubifs_ref_node *ref)
{
	struct ubifs_bud *bud;
	int lnum = le32_to_cpu(ref->lnum);
	unsigned int offs = le32_to_cpu(ref->offs);
	unsigned int jhead = le32_to_cpu(ref->jhead);

	/*
	 * ref->offs may point to the end of LEB when the journal head points
	 * to the end of LEB and we write reference node for it during commit.
	 * So this is why we require 'offs > c->leb_size'.
	 */
	if (jhead >= c->jhead_cnt || lnum >= c->leb_cnt ||
	    lnum < c->main_first || offs > c->leb_size ||
	    offs & (c->min_io_size - 1))
		return -EINVAL;

	/* Make sure we have not already looked at this bud */
	bud = ubifs_search_bud(c, lnum);
	if (bud) {
		if (bud->jhead == jhead && bud->start <= offs)
			return 1;
		ubifs_err(c, "bud at LEB %d:%d was already referred", lnum, offs);
		return -EINVAL;
	}

	return 0;
}

/**
 * replay_log_leb - replay a log logical eraseblock.
 * @c: UBIFS file-system description object
 * @lnum: log logical eraseblock to replay
 * @offs: offset to start replaying from
 * @sbuf: scan buffer
 *
 * This function replays a log LEB and returns zero in case of success, %1 if
 * this is the last LEB in the log, and a negative error code in case of
 * failure.
 */
static int replay_log_leb(struct ubifs_info *c, int lnum, int offs, void *sbuf)
{
	int err;
	struct ubifs_scan_leb *sleb;
	struct ubifs_scan_node *snod;
	const struct ubifs_cs_node *node;

	dbg_mnt("replay log LEB %d:%d", lnum, offs);
	sleb = ubifs_scan(c, lnum, offs, sbuf, c->need_recovery);
	if (IS_ERR(sleb)) {
		if (PTR_ERR(sleb) != -EUCLEAN || !c->need_recovery)
			return PTR_ERR(sleb);
		/*
		 * Note, the below function will recover this log LEB only if
		 * it is the last, because unclean reboots can possibly corrupt
		 * only the tail of the log.
		 */
		sleb = ubifs_recover_log_leb(c, lnum, offs, sbuf);
		if (IS_ERR(sleb))
			return PTR_ERR(sleb);
	}

	if (sleb->nodes_cnt == 0) {
		err = 1;
		goto out;
	}

	node = sleb->buf;
	snod = list_entry(sleb->nodes.next, struct ubifs_scan_node, list);
	if (c->cs_sqnum == 0) {
		/*
		 * This is the first log LEB we are looking at, make sure that
		 * the first node is a commit start node. Also record its
		 * sequence number so that UBIFS can determine where the log
		 * ends, because all nodes which were have higher sequence
		 * numbers.
		 */
		if (snod->type != UBIFS_CS_NODE) {
			ubifs_err(c, "first log node at LEB %d:%d is not CS node",
				  lnum, offs);
			goto out_dump;
		}
		if (le64_to_cpu(node->cmt_no) != c->cmt_no) {
			ubifs_err(c, "first CS node at LEB %d:%d has wrong commit number %llu expected %llu",
				  lnum, offs,
				  (unsigned long long)le64_to_cpu(node->cmt_no),
				  c->cmt_no);
			goto out_dump;
		}

		c->cs_sqnum = le64_to_cpu(node->ch.sqnum);
		dbg_mnt("commit start sqnum %llu", c->cs_sqnum);
	}

	if (snod->sqnum < c->cs_sqnum) {
		/*
		 * This means that we reached end of log and now
		 * look to the older log data, which was already
		 * committed but the eraseblock was not erased (UBIFS
		 * only un-maps it). So this basically means we have to
		 * exit with "end of log" code.
		 */
		err = 1;
		goto out;
	}

	/* Make sure the first node sits at offset zero of the LEB */
	if (snod->offs != 0) {
		ubifs_err(c, "first node is not at zero offset");
		goto out_dump;
	}

	list_for_each_entry(snod, &sleb->nodes, list) {
		cond_resched();

		if (snod->sqnum >= SQNUM_WATERMARK) {
			ubifs_err(c, "file system's life ended");
			goto out_dump;
		}

		if (snod->sqnum < c->cs_sqnum) {
			ubifs_err(c, "bad sqnum %llu, commit sqnum %llu",
				  snod->sqnum, c->cs_sqnum);
			goto out_dump;
		}

		if (snod->sqnum > c->max_sqnum)
			c->max_sqnum = snod->sqnum;

		switch (snod->type) {
		case UBIFS_REF_NODE: {
			const struct ubifs_ref_node *ref = snod->node;

			err = validate_ref(c, ref);
			if (err == 1)
				break; /* Already have this bud */
			if (err)
				goto out_dump;

			err = add_replay_bud(c, le32_to_cpu(ref->lnum),
					     le32_to_cpu(ref->offs),
					     le32_to_cpu(ref->jhead),
					     snod->sqnum);
			if (err)
				goto out;

			break;
		}
		case UBIFS_CS_NODE:
			/* Make sure it sits at the beginning of LEB */
			if (snod->offs != 0) {
				ubifs_err(c, "unexpected node in log");
				goto out_dump;
			}
			break;
		default:
			ubifs_err(c, "unexpected node in log");
			goto out_dump;
		}
	}

	if (sleb->endpt || c->lhead_offs >= c->leb_size) {
		c->lhead_lnum = lnum;
		c->lhead_offs = sleb->endpt;
	}

	err = !sleb->endpt;
out:
	ubifs_scan_destroy(sleb);
	return err;

out_dump:
	ubifs_err(c, "log error detected while replaying the log at LEB %d:%d",
		  lnum, offs + snod->offs);
	ubifs_dump_node(c, snod->node);
	ubifs_scan_destroy(sleb);
	return -EINVAL;
}

/**
 * take_ihead - update the status of the index head in lprops to 'taken'.
 * @c: UBIFS file-system description object
 *
 * This function returns the amount of free space in the index head LEB or a
 * negative error code.
 */
static int take_ihead(struct ubifs_info *c)
{
	const struct ubifs_lprops *lp;
	int err, free;

	ubifs_get_lprops(c);

	lp = ubifs_lpt_lookup_dirty(c, c->ihead_lnum);
	if (IS_ERR(lp)) {
		err = PTR_ERR(lp);
		goto out;
	}

	free = lp->free;

	lp = ubifs_change_lp(c, lp, LPROPS_NC, LPROPS_NC,
			     lp->flags | LPROPS_TAKEN, 0);
	if (IS_ERR(lp)) {
		err = PTR_ERR(lp);
		goto out;
	}

	err = free;
out:
	ubifs_release_lprops(c);
	return err;
}

/**
 * ubifs_replay_journal - replay journal.
 * @c: UBIFS file-system description object
 *
 * This function scans the journal, replays and cleans it up. It makes sure all
 * memory data structures related to uncommitted journal are built (dirty TNC
 * tree, tree of buds, modified lprops, etc).
 */
int ubifs_replay_journal(struct ubifs_info *c)
{
	int err, lnum, free;

	BUILD_BUG_ON(UBIFS_TRUN_KEY > 5);

	/* Update the status of the index head in lprops to 'taken' */
	free = take_ihead(c);
	if (free < 0)
		return free; /* Error code */

	if (c->ihead_offs != c->leb_size - free) {
		ubifs_err(c, "bad index head LEB %d:%d", c->ihead_lnum,
			  c->ihead_offs);
		return -EINVAL;
	}

	dbg_mnt("start replaying the journal");
	c->replaying = 1;
	lnum = c->ltail_lnum = c->lhead_lnum;

	do {
		err = replay_log_leb(c, lnum, 0, c->sbuf);
		if (err == 1) {
			if (lnum != c->lhead_lnum)
				/* We hit the end of the log */
				break;

			/*
			 * The head of the log must always start with the
			 * "commit start" node on a properly formatted UBIFS.
			 * But we found no nodes at all, which means that
			 * something went wrong and we cannot proceed mounting
			 * the file-system.
			 */
			ubifs_err(c, "no UBIFS nodes found at the log head LEB %d:%d, possibly corrupted",
				  lnum, 0);
			err = -EINVAL;
		}
		if (err)
			goto out;
		lnum = ubifs_next_log_lnum(c, lnum);
	} while (lnum != c->ltail_lnum);

	err = replay_buds(c);
	if (err)
		goto out;

	err = apply_replay_list(c);
	if (err)
		goto out;

	err = set_buds_lprops(c);
	if (err)
		goto out;

	/*
	 * UBIFS budgeting calculations use @c->bi.uncommitted_idx variable
	 * to roughly estimate index growth. Things like @c->bi.min_idx_lebs
	 * depend on it. This means we have to initialize it to make sure
	 * budgeting works properly.
	 */
	c->bi.uncommitted_idx = atomic_long_read(&c->dirty_zn_cnt);
	c->bi.uncommitted_idx *= c->max_idx_node_sz;

	ubifs_assert(c, c->bud_bytes <= c->max_bud_bytes || c->need_recovery);
	dbg_mnt("finished, log head LEB %d:%d, max_sqnum %llu, highest_inum %lu",
		c->lhead_lnum, c->lhead_offs, c->max_sqnum,
		(unsigned long)c->highest_inum);
out:
	destroy_replay_list(c);
	destroy_bud_list(c);
	c->replaying = 0;
	return err;
}