Adding upstream version 6.6.15.upstream/6.6.15

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1111 insertions, 0 deletions

diff --git a/fs/ubifs/tnc_commit.c b/fs/ubifs/tnc_commit.c
new file mode 100644
index 0000000000..a55e04822d
--- /dev/null
+++ b/fs/ubifs/tnc_commit.c
@@ -0,0 +1,1111 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * This file is part of UBIFS.
+ *
+ * Copyright (C) 2006-2008 Nokia Corporation.
+ *
+ * Authors: Adrian Hunter
+ *          Artem Bityutskiy (Битюцкий Артём)
+ */
+
+/* This file implements TNC functions for committing */
+
+#include <linux/random.h>
+#include "ubifs.h"
+
+/**
+ * make_idx_node - make an index node for fill-the-gaps method of TNC commit.
+ * @c: UBIFS file-system description object
+ * @idx: buffer in which to place new index node
+ * @znode: znode from which to make new index node
+ * @lnum: LEB number where new index node will be written
+ * @offs: offset where new index node will be written
+ * @len: length of new index node
+ */
+static int make_idx_node(struct ubifs_info *c, struct ubifs_idx_node *idx,
+			 struct ubifs_znode *znode, int lnum, int offs, int len)
+{
+	struct ubifs_znode *zp;
+	u8 hash[UBIFS_HASH_ARR_SZ];
+	int i, err;
+
+	/* Make index node */
+	idx->ch.node_type = UBIFS_IDX_NODE;
+	idx->child_cnt = cpu_to_le16(znode->child_cnt);
+	idx->level = cpu_to_le16(znode->level);
+	for (i = 0; i < znode->child_cnt; i++) {
+		struct ubifs_branch *br = ubifs_idx_branch(c, idx, i);
+		struct ubifs_zbranch *zbr = &znode->zbranch[i];
+
+		key_write_idx(c, &zbr->key, &br->key);
+		br->lnum = cpu_to_le32(zbr->lnum);
+		br->offs = cpu_to_le32(zbr->offs);
+		br->len = cpu_to_le32(zbr->len);
+		ubifs_copy_hash(c, zbr->hash, ubifs_branch_hash(c, br));
+		if (!zbr->lnum || !zbr->len) {
+			ubifs_err(c, "bad ref in znode");
+			ubifs_dump_znode(c, znode);
+			if (zbr->znode)
+				ubifs_dump_znode(c, zbr->znode);
+
+			return -EINVAL;
+		}
+	}
+	ubifs_prepare_node(c, idx, len, 0);
+	ubifs_node_calc_hash(c, idx, hash);
+
+	znode->lnum = lnum;
+	znode->offs = offs;
+	znode->len = len;
+
+	err = insert_old_idx_znode(c, znode);
+
+	/* Update the parent */
+	zp = znode->parent;
+	if (zp) {
+		struct ubifs_zbranch *zbr;
+
+		zbr = &zp->zbranch[znode->iip];
+		zbr->lnum = lnum;
+		zbr->offs = offs;
+		zbr->len = len;
+		ubifs_copy_hash(c, hash, zbr->hash);
+	} else {
+		c->zroot.lnum = lnum;
+		c->zroot.offs = offs;
+		c->zroot.len = len;
+		ubifs_copy_hash(c, hash, c->zroot.hash);
+	}
+	c->calc_idx_sz += ALIGN(len, 8);
+
+	atomic_long_dec(&c->dirty_zn_cnt);
+
+	ubifs_assert(c, ubifs_zn_dirty(znode));
+	ubifs_assert(c, ubifs_zn_cow(znode));
+
+	/*
+	 * Note, unlike 'write_index()' we do not add memory barriers here
+	 * because this function is called with @c->tnc_mutex locked.
+	 */
+	__clear_bit(DIRTY_ZNODE, &znode->flags);
+	__clear_bit(COW_ZNODE, &znode->flags);
+
+	return err;
+}
+
+/**
+ * fill_gap - make index nodes in gaps in dirty index LEBs.
+ * @c: UBIFS file-system description object
+ * @lnum: LEB number that gap appears in
+ * @gap_start: offset of start of gap
+ * @gap_end: offset of end of gap
+ * @dirt: adds dirty space to this
+ *
+ * This function returns the number of index nodes written into the gap.
+ */
+static int fill_gap(struct ubifs_info *c, int lnum, int gap_start, int gap_end,
+		    int *dirt)
+{
+	int len, gap_remains, gap_pos, written, pad_len;
+
+	ubifs_assert(c, (gap_start & 7) == 0);
+	ubifs_assert(c, (gap_end & 7) == 0);
+	ubifs_assert(c, gap_end >= gap_start);
+
+	gap_remains = gap_end - gap_start;
+	if (!gap_remains)
+		return 0;
+	gap_pos = gap_start;
+	written = 0;
+	while (c->enext) {
+		len = ubifs_idx_node_sz(c, c->enext->child_cnt);
+		if (len < gap_remains) {
+			struct ubifs_znode *znode = c->enext;
+			const int alen = ALIGN(len, 8);
+			int err;
+
+			ubifs_assert(c, alen <= gap_remains);
+			err = make_idx_node(c, c->ileb_buf + gap_pos, znode,
+					    lnum, gap_pos, len);
+			if (err)
+				return err;
+			gap_remains -= alen;
+			gap_pos += alen;
+			c->enext = znode->cnext;
+			if (c->enext == c->cnext)
+				c->enext = NULL;
+			written += 1;
+		} else
+			break;
+	}
+	if (gap_end == c->leb_size) {
+		c->ileb_len = ALIGN(gap_pos, c->min_io_size);
+		/* Pad to end of min_io_size */
+		pad_len = c->ileb_len - gap_pos;
+	} else
+		/* Pad to end of gap */
+		pad_len = gap_remains;
+	dbg_gc("LEB %d:%d to %d len %d nodes written %d wasted bytes %d",
+	       lnum, gap_start, gap_end, gap_end - gap_start, written, pad_len);
+	ubifs_pad(c, c->ileb_buf + gap_pos, pad_len);
+	*dirt += pad_len;
+	return written;
+}
+
+/**
+ * find_old_idx - find an index node obsoleted since the last commit start.
+ * @c: UBIFS file-system description object
+ * @lnum: LEB number of obsoleted index node
+ * @offs: offset of obsoleted index node
+ *
+ * Returns %1 if found and %0 otherwise.
+ */
+static int find_old_idx(struct ubifs_info *c, int lnum, int offs)
+{
+	struct ubifs_old_idx *o;
+	struct rb_node *p;
+
+	p = c->old_idx.rb_node;
+	while (p) {
+		o = rb_entry(p, struct ubifs_old_idx, rb);
+		if (lnum < o->lnum)
+			p = p->rb_left;
+		else if (lnum > o->lnum)
+			p = p->rb_right;
+		else if (offs < o->offs)
+			p = p->rb_left;
+		else if (offs > o->offs)
+			p = p->rb_right;
+		else
+			return 1;
+	}
+	return 0;
+}
+
+/**
+ * is_idx_node_in_use - determine if an index node can be overwritten.
+ * @c: UBIFS file-system description object
+ * @key: key of index node
+ * @level: index node level
+ * @lnum: LEB number of index node
+ * @offs: offset of index node
+ *
+ * If @key / @lnum / @offs identify an index node that was not part of the old
+ * index, then this function returns %0 (obsolete).  Else if the index node was
+ * part of the old index but is now dirty %1 is returned, else if it is clean %2
+ * is returned. A negative error code is returned on failure.
+ */
+static int is_idx_node_in_use(struct ubifs_info *c, union ubifs_key *key,
+			      int level, int lnum, int offs)
+{
+	int ret;
+
+	ret = is_idx_node_in_tnc(c, key, level, lnum, offs);
+	if (ret < 0)
+		return ret; /* Error code */
+	if (ret == 0)
+		if (find_old_idx(c, lnum, offs))
+			return 1;
+	return ret;
+}
+
+/**
+ * layout_leb_in_gaps - layout index nodes using in-the-gaps method.
+ * @c: UBIFS file-system description object
+ * @p: return LEB number in @c->gap_lebs[p]
+ *
+ * This function lays out new index nodes for dirty znodes using in-the-gaps
+ * method of TNC commit.
+ * This function merely puts the next znode into the next gap, making no attempt
+ * to try to maximise the number of znodes that fit.
+ * This function returns the number of index nodes written into the gaps, or a
+ * negative error code on failure.
+ */
+static int layout_leb_in_gaps(struct ubifs_info *c, int p)
+{
+	struct ubifs_scan_leb *sleb;
+	struct ubifs_scan_node *snod;
+	int lnum, dirt = 0, gap_start, gap_end, err, written, tot_written;
+
+	tot_written = 0;
+	/* Get an index LEB with lots of obsolete index nodes */
+	lnum = ubifs_find_dirty_idx_leb(c);
+	if (lnum < 0)
+		/*
+		 * There also may be dirt in the index head that could be
+		 * filled, however we do not check there at present.
+		 */
+		return lnum; /* Error code */
+	c->gap_lebs[p] = lnum;
+	dbg_gc("LEB %d", lnum);
+	/*
+	 * Scan the index LEB.  We use the generic scan for this even though
+	 * it is more comprehensive and less efficient than is needed for this
+	 * purpose.
+	 */
+	sleb = ubifs_scan(c, lnum, 0, c->ileb_buf, 0);
+	c->ileb_len = 0;
+	if (IS_ERR(sleb))
+		return PTR_ERR(sleb);
+	gap_start = 0;
+	list_for_each_entry(snod, &sleb->nodes, list) {
+		struct ubifs_idx_node *idx;
+		int in_use, level;
+
+		ubifs_assert(c, snod->type == UBIFS_IDX_NODE);
+		idx = snod->node;
+		key_read(c, ubifs_idx_key(c, idx), &snod->key);
+		level = le16_to_cpu(idx->level);
+		/* Determine if the index node is in use (not obsolete) */
+		in_use = is_idx_node_in_use(c, &snod->key, level, lnum,
+					    snod->offs);
+		if (in_use < 0) {
+			ubifs_scan_destroy(sleb);
+			return in_use; /* Error code */
+		}
+		if (in_use) {
+			if (in_use == 1)
+				dirt += ALIGN(snod->len, 8);
+			/*
+			 * The obsolete index nodes form gaps that can be
+			 * overwritten.  This gap has ended because we have
+			 * found an index node that is still in use
+			 * i.e. not obsolete
+			 */
+			gap_end = snod->offs;
+			/* Try to fill gap */
+			written = fill_gap(c, lnum, gap_start, gap_end, &dirt);
+			if (written < 0) {
+				ubifs_scan_destroy(sleb);
+				return written; /* Error code */
+			}
+			tot_written += written;
+			gap_start = ALIGN(snod->offs + snod->len, 8);
+		}
+	}
+	ubifs_scan_destroy(sleb);
+	c->ileb_len = c->leb_size;
+	gap_end = c->leb_size;
+	/* Try to fill gap */
+	written = fill_gap(c, lnum, gap_start, gap_end, &dirt);
+	if (written < 0)
+		return written; /* Error code */
+	tot_written += written;
+	if (tot_written == 0) {
+		struct ubifs_lprops lp;
+
+		dbg_gc("LEB %d wrote %d index nodes", lnum, tot_written);
+		err = ubifs_read_one_lp(c, lnum, &lp);
+		if (err)
+			return err;
+		if (lp.free == c->leb_size) {
+			/*
+			 * We must have snatched this LEB from the idx_gc list
+			 * so we need to correct the free and dirty space.
+			 */
+			err = ubifs_change_one_lp(c, lnum,
+						  c->leb_size - c->ileb_len,
+						  dirt, 0, 0, 0);
+			if (err)
+				return err;
+		}
+		return 0;
+	}
+	err = ubifs_change_one_lp(c, lnum, c->leb_size - c->ileb_len, dirt,
+				  0, 0, 0);
+	if (err)
+		return err;
+	err = ubifs_leb_change(c, lnum, c->ileb_buf, c->ileb_len);
+	if (err)
+		return err;
+	dbg_gc("LEB %d wrote %d index nodes", lnum, tot_written);
+	return tot_written;
+}
+
+/**
+ * get_leb_cnt - calculate the number of empty LEBs needed to commit.
+ * @c: UBIFS file-system description object
+ * @cnt: number of znodes to commit
+ *
+ * This function returns the number of empty LEBs needed to commit @cnt znodes
+ * to the current index head.  The number is not exact and may be more than
+ * needed.
+ */
+static int get_leb_cnt(struct ubifs_info *c, int cnt)
+{
+	int d;
+
+	/* Assume maximum index node size (i.e. overestimate space needed) */
+	cnt -= (c->leb_size - c->ihead_offs) / c->max_idx_node_sz;
+	if (cnt < 0)
+		cnt = 0;
+	d = c->leb_size / c->max_idx_node_sz;
+	return DIV_ROUND_UP(cnt, d);
+}
+
+/**
+ * layout_in_gaps - in-the-gaps method of committing TNC.
+ * @c: UBIFS file-system description object
+ * @cnt: number of dirty znodes to commit.
+ *
+ * This function lays out new index nodes for dirty znodes using in-the-gaps
+ * method of TNC commit.
+ *
+ * This function returns %0 on success and a negative error code on failure.
+ */
+static int layout_in_gaps(struct ubifs_info *c, int cnt)
+{
+	int err, leb_needed_cnt, written, p = 0, old_idx_lebs, *gap_lebs;
+
+	dbg_gc("%d znodes to write", cnt);
+
+	c->gap_lebs = kmalloc_array(c->lst.idx_lebs + 1, sizeof(int),
+				    GFP_NOFS);
+	if (!c->gap_lebs)
+		return -ENOMEM;
+
+	old_idx_lebs = c->lst.idx_lebs;
+	do {
+		ubifs_assert(c, p < c->lst.idx_lebs);
+		written = layout_leb_in_gaps(c, p);
+		if (written < 0) {
+			err = written;
+			if (err != -ENOSPC) {
+				kfree(c->gap_lebs);
+				c->gap_lebs = NULL;
+				return err;
+			}
+			if (!dbg_is_chk_index(c)) {
+				/*
+				 * Do not print scary warnings if the debugging
+				 * option which forces in-the-gaps is enabled.
+				 */
+				ubifs_warn(c, "out of space");
+				ubifs_dump_budg(c, &c->bi);
+				ubifs_dump_lprops(c);
+			}
+			/* Try to commit anyway */
+			break;
+		}
+		p++;
+		cnt -= written;
+		leb_needed_cnt = get_leb_cnt(c, cnt);
+		dbg_gc("%d znodes remaining, need %d LEBs, have %d", cnt,
+		       leb_needed_cnt, c->ileb_cnt);
+		/*
+		 * Dynamically change the size of @c->gap_lebs to prevent
+		 * oob, because @c->lst.idx_lebs could be increased by
+		 * function @get_idx_gc_leb (called by layout_leb_in_gaps->
+		 * ubifs_find_dirty_idx_leb) during loop. Only enlarge
+		 * @c->gap_lebs when needed.
+		 *
+		 */
+		if (leb_needed_cnt > c->ileb_cnt && p >= old_idx_lebs &&
+		    old_idx_lebs < c->lst.idx_lebs) {
+			old_idx_lebs = c->lst.idx_lebs;
+			gap_lebs = krealloc(c->gap_lebs, sizeof(int) *
+					       (old_idx_lebs + 1), GFP_NOFS);
+			if (!gap_lebs) {
+				kfree(c->gap_lebs);
+				c->gap_lebs = NULL;
+				return -ENOMEM;
+			}
+			c->gap_lebs = gap_lebs;
+		}
+	} while (leb_needed_cnt > c->ileb_cnt);
+
+	c->gap_lebs[p] = -1;
+	return 0;
+}
+
+/**
+ * layout_in_empty_space - layout index nodes in empty space.
+ * @c: UBIFS file-system description object
+ *
+ * This function lays out new index nodes for dirty znodes using empty LEBs.
+ *
+ * This function returns %0 on success and a negative error code on failure.
+ */
+static int layout_in_empty_space(struct ubifs_info *c)
+{
+	struct ubifs_znode *znode, *cnext, *zp;
+	int lnum, offs, len, next_len, buf_len, buf_offs, used, avail;
+	int wlen, blen, err;
+
+	cnext = c->enext;
+	if (!cnext)
+		return 0;
+
+	lnum = c->ihead_lnum;
+	buf_offs = c->ihead_offs;
+
+	buf_len = ubifs_idx_node_sz(c, c->fanout);
+	buf_len = ALIGN(buf_len, c->min_io_size);
+	used = 0;
+	avail = buf_len;
+
+	/* Ensure there is enough room for first write */
+	next_len = ubifs_idx_node_sz(c, cnext->child_cnt);
+	if (buf_offs + next_len > c->leb_size)
+		lnum = -1;
+
+	while (1) {
+		znode = cnext;
+
+		len = ubifs_idx_node_sz(c, znode->child_cnt);
+
+		/* Determine the index node position */
+		if (lnum == -1) {
+			if (c->ileb_nxt >= c->ileb_cnt) {
+				ubifs_err(c, "out of space");
+				return -ENOSPC;
+			}
+			lnum = c->ilebs[c->ileb_nxt++];
+			buf_offs = 0;
+			used = 0;
+			avail = buf_len;
+		}
+
+		offs = buf_offs + used;
+
+		znode->lnum = lnum;
+		znode->offs = offs;
+		znode->len = len;
+
+		/* Update the parent */
+		zp = znode->parent;
+		if (zp) {
+			struct ubifs_zbranch *zbr;
+			int i;
+
+			i = znode->iip;
+			zbr = &zp->zbranch[i];
+			zbr->lnum = lnum;
+			zbr->offs = offs;
+			zbr->len = len;
+		} else {
+			c->zroot.lnum = lnum;
+			c->zroot.offs = offs;
+			c->zroot.len = len;
+		}
+		c->calc_idx_sz += ALIGN(len, 8);
+
+		/*
+		 * Once lprops is updated, we can decrease the dirty znode count
+		 * but it is easier to just do it here.
+		 */
+		atomic_long_dec(&c->dirty_zn_cnt);
+
+		/*
+		 * Calculate the next index node length to see if there is
+		 * enough room for it
+		 */
+		cnext = znode->cnext;
+		if (cnext == c->cnext)
+			next_len = 0;
+		else
+			next_len = ubifs_idx_node_sz(c, cnext->child_cnt);
+
+		/* Update buffer positions */
+		wlen = used + len;
+		used += ALIGN(len, 8);
+		avail -= ALIGN(len, 8);
+
+		if (next_len != 0 &&
+		    buf_offs + used + next_len <= c->leb_size &&
+		    avail > 0)
+			continue;
+
+		if (avail <= 0 && next_len &&
+		    buf_offs + used + next_len <= c->leb_size)
+			blen = buf_len;
+		else
+			blen = ALIGN(wlen, c->min_io_size);
+
+		/* The buffer is full or there are no more znodes to do */
+		buf_offs += blen;
+		if (next_len) {
+			if (buf_offs + next_len > c->leb_size) {
+				err = ubifs_update_one_lp(c, lnum,
+					c->leb_size - buf_offs, blen - used,
+					0, 0);
+				if (err)
+					return err;
+				lnum = -1;
+			}
+			used -= blen;
+			if (used < 0)
+				used = 0;
+			avail = buf_len - used;
+			continue;
+		}
+		err = ubifs_update_one_lp(c, lnum, c->leb_size - buf_offs,
+					  blen - used, 0, 0);
+		if (err)
+			return err;
+		break;
+	}
+
+	c->dbg->new_ihead_lnum = lnum;
+	c->dbg->new_ihead_offs = buf_offs;
+
+	return 0;
+}
+
+/**
+ * layout_commit - determine positions of index nodes to commit.
+ * @c: UBIFS file-system description object
+ * @no_space: indicates that insufficient empty LEBs were allocated
+ * @cnt: number of znodes to commit
+ *
+ * Calculate and update the positions of index nodes to commit.  If there were
+ * an insufficient number of empty LEBs allocated, then index nodes are placed
+ * into the gaps created by obsolete index nodes in non-empty index LEBs.  For
+ * this purpose, an obsolete index node is one that was not in the index as at
+ * the end of the last commit.  To write "in-the-gaps" requires that those index
+ * LEBs are updated atomically in-place.
+ */
+static int layout_commit(struct ubifs_info *c, int no_space, int cnt)
+{
+	int err;
+
+	if (no_space) {
+		err = layout_in_gaps(c, cnt);
+		if (err)
+			return err;
+	}
+	err = layout_in_empty_space(c);
+	return err;
+}
+
+/**
+ * find_first_dirty - find first dirty znode.
+ * @znode: znode to begin searching from
+ */
+static struct ubifs_znode *find_first_dirty(struct ubifs_znode *znode)
+{
+	int i, cont;
+
+	if (!znode)
+		return NULL;
+
+	while (1) {
+		if (znode->level == 0) {
+			if (ubifs_zn_dirty(znode))
+				return znode;
+			return NULL;
+		}
+		cont = 0;
+		for (i = 0; i < znode->child_cnt; i++) {
+			struct ubifs_zbranch *zbr = &znode->zbranch[i];
+
+			if (zbr->znode && ubifs_zn_dirty(zbr->znode)) {
+				znode = zbr->znode;
+				cont = 1;
+				break;
+			}
+		}
+		if (!cont) {
+			if (ubifs_zn_dirty(znode))
+				return znode;
+			return NULL;
+		}
+	}
+}
+
+/**
+ * find_next_dirty - find next dirty znode.
+ * @znode: znode to begin searching from
+ */
+static struct ubifs_znode *find_next_dirty(struct ubifs_znode *znode)
+{
+	int n = znode->iip + 1;
+
+	znode = znode->parent;
+	if (!znode)
+		return NULL;
+	for (; n < znode->child_cnt; n++) {
+		struct ubifs_zbranch *zbr = &znode->zbranch[n];
+
+		if (zbr->znode && ubifs_zn_dirty(zbr->znode))
+			return find_first_dirty(zbr->znode);
+	}
+	return znode;
+}
+
+/**
+ * get_znodes_to_commit - create list of dirty znodes to commit.
+ * @c: UBIFS file-system description object
+ *
+ * This function returns the number of znodes to commit.
+ */
+static int get_znodes_to_commit(struct ubifs_info *c)
+{
+	struct ubifs_znode *znode, *cnext;
+	int cnt = 0;
+
+	c->cnext = find_first_dirty(c->zroot.znode);
+	znode = c->enext = c->cnext;
+	if (!znode) {
+		dbg_cmt("no znodes to commit");
+		return 0;
+	}
+	cnt += 1;
+	while (1) {
+		ubifs_assert(c, !ubifs_zn_cow(znode));
+		__set_bit(COW_ZNODE, &znode->flags);
+		znode->alt = 0;
+		cnext = find_next_dirty(znode);
+		if (!cnext) {
+			znode->cnext = c->cnext;
+			break;
+		}
+		znode->cparent = znode->parent;
+		znode->ciip = znode->iip;
+		znode->cnext = cnext;
+		znode = cnext;
+		cnt += 1;
+	}
+	dbg_cmt("committing %d znodes", cnt);
+	ubifs_assert(c, cnt == atomic_long_read(&c->dirty_zn_cnt));
+	return cnt;
+}
+
+/**
+ * alloc_idx_lebs - allocate empty LEBs to be used to commit.
+ * @c: UBIFS file-system description object
+ * @cnt: number of znodes to commit
+ *
+ * This function returns %-ENOSPC if it cannot allocate a sufficient number of
+ * empty LEBs.  %0 is returned on success, otherwise a negative error code
+ * is returned.
+ */
+static int alloc_idx_lebs(struct ubifs_info *c, int cnt)
+{
+	int i, leb_cnt, lnum;
+
+	c->ileb_cnt = 0;
+	c->ileb_nxt = 0;
+	leb_cnt = get_leb_cnt(c, cnt);
+	dbg_cmt("need about %d empty LEBS for TNC commit", leb_cnt);
+	if (!leb_cnt)
+		return 0;
+	c->ilebs = kmalloc_array(leb_cnt, sizeof(int), GFP_NOFS);
+	if (!c->ilebs)
+		return -ENOMEM;
+	for (i = 0; i < leb_cnt; i++) {
+		lnum = ubifs_find_free_leb_for_idx(c);
+		if (lnum < 0)
+			return lnum;
+		c->ilebs[c->ileb_cnt++] = lnum;
+		dbg_cmt("LEB %d", lnum);
+	}
+	if (dbg_is_chk_index(c) && !get_random_u32_below(8))
+		return -ENOSPC;
+	return 0;
+}
+
+/**
+ * free_unused_idx_lebs - free unused LEBs that were allocated for the commit.
+ * @c: UBIFS file-system description object
+ *
+ * It is possible that we allocate more empty LEBs for the commit than we need.
+ * This functions frees the surplus.
+ *
+ * This function returns %0 on success and a negative error code on failure.
+ */
+static int free_unused_idx_lebs(struct ubifs_info *c)
+{
+	int i, err = 0, lnum, er;
+
+	for (i = c->ileb_nxt; i < c->ileb_cnt; i++) {
+		lnum = c->ilebs[i];
+		dbg_cmt("LEB %d", lnum);
+		er = ubifs_change_one_lp(c, lnum, LPROPS_NC, LPROPS_NC, 0,
+					 LPROPS_INDEX | LPROPS_TAKEN, 0);
+		if (!err)
+			err = er;
+	}
+	return err;
+}
+
+/**
+ * free_idx_lebs - free unused LEBs after commit end.
+ * @c: UBIFS file-system description object
+ *
+ * This function returns %0 on success and a negative error code on failure.
+ */
+static int free_idx_lebs(struct ubifs_info *c)
+{
+	int err;
+
+	err = free_unused_idx_lebs(c);
+	kfree(c->ilebs);
+	c->ilebs = NULL;
+	return err;
+}
+
+/**
+ * ubifs_tnc_start_commit - start TNC commit.
+ * @c: UBIFS file-system description object
+ * @zroot: new index root position is returned here
+ *
+ * This function prepares the list of indexing nodes to commit and lays out
+ * their positions on flash. If there is not enough free space it uses the
+ * in-gap commit method. Returns zero in case of success and a negative error
+ * code in case of failure.
+ */
+int ubifs_tnc_start_commit(struct ubifs_info *c, struct ubifs_zbranch *zroot)
+{
+	int err = 0, cnt;
+
+	mutex_lock(&c->tnc_mutex);
+	err = dbg_check_tnc(c, 1);
+	if (err)
+		goto out;
+	cnt = get_znodes_to_commit(c);
+	if (cnt != 0) {
+		int no_space = 0;
+
+		err = alloc_idx_lebs(c, cnt);
+		if (err == -ENOSPC)
+			no_space = 1;
+		else if (err)
+			goto out_free;
+		err = layout_commit(c, no_space, cnt);
+		if (err)
+			goto out_free;
+		ubifs_assert(c, atomic_long_read(&c->dirty_zn_cnt) == 0);
+		err = free_unused_idx_lebs(c);
+		if (err)
+			goto out;
+	}
+	destroy_old_idx(c);
+	memcpy(zroot, &c->zroot, sizeof(struct ubifs_zbranch));
+
+	err = ubifs_save_dirty_idx_lnums(c);
+	if (err)
+		goto out;
+
+	spin_lock(&c->space_lock);
+	/*
+	 * Although we have not finished committing yet, update size of the
+	 * committed index ('c->bi.old_idx_sz') and zero out the index growth
+	 * budget. It is OK to do this now, because we've reserved all the
+	 * space which is needed to commit the index, and it is save for the
+	 * budgeting subsystem to assume the index is already committed,
+	 * even though it is not.
+	 */
+	ubifs_assert(c, c->bi.min_idx_lebs == ubifs_calc_min_idx_lebs(c));
+	c->bi.old_idx_sz = c->calc_idx_sz;
+	c->bi.uncommitted_idx = 0;
+	c->bi.min_idx_lebs = ubifs_calc_min_idx_lebs(c);
+	spin_unlock(&c->space_lock);
+	mutex_unlock(&c->tnc_mutex);
+
+	dbg_cmt("number of index LEBs %d", c->lst.idx_lebs);
+	dbg_cmt("size of index %llu", c->calc_idx_sz);
+	return err;
+
+out_free:
+	free_idx_lebs(c);
+out:
+	mutex_unlock(&c->tnc_mutex);
+	return err;
+}
+
+/**
+ * write_index - write index nodes.
+ * @c: UBIFS file-system description object
+ *
+ * This function writes the index nodes whose positions were laid out in the
+ * layout_in_empty_space function.
+ */
+static int write_index(struct ubifs_info *c)
+{
+	struct ubifs_idx_node *idx;
+	struct ubifs_znode *znode, *cnext;
+	int i, lnum, offs, len, next_len, buf_len, buf_offs, used;
+	int avail, wlen, err, lnum_pos = 0, blen, nxt_offs;
+
+	cnext = c->enext;
+	if (!cnext)
+		return 0;
+
+	/*
+	 * Always write index nodes to the index head so that index nodes and
+	 * other types of nodes are never mixed in the same erase block.
+	 */
+	lnum = c->ihead_lnum;
+	buf_offs = c->ihead_offs;
+
+	/* Allocate commit buffer */
+	buf_len = ALIGN(c->max_idx_node_sz, c->min_io_size);
+	used = 0;
+	avail = buf_len;
+
+	/* Ensure there is enough room for first write */
+	next_len = ubifs_idx_node_sz(c, cnext->child_cnt);
+	if (buf_offs + next_len > c->leb_size) {
+		err = ubifs_update_one_lp(c, lnum, LPROPS_NC, 0, 0,
+					  LPROPS_TAKEN);
+		if (err)
+			return err;
+		lnum = -1;
+	}
+
+	while (1) {
+		u8 hash[UBIFS_HASH_ARR_SZ];
+
+		cond_resched();
+
+		znode = cnext;
+		idx = c->cbuf + used;
+
+		/* Make index node */
+		idx->ch.node_type = UBIFS_IDX_NODE;
+		idx->child_cnt = cpu_to_le16(znode->child_cnt);
+		idx->level = cpu_to_le16(znode->level);
+		for (i = 0; i < znode->child_cnt; i++) {
+			struct ubifs_branch *br = ubifs_idx_branch(c, idx, i);
+			struct ubifs_zbranch *zbr = &znode->zbranch[i];
+
+			key_write_idx(c, &zbr->key, &br->key);
+			br->lnum = cpu_to_le32(zbr->lnum);
+			br->offs = cpu_to_le32(zbr->offs);
+			br->len = cpu_to_le32(zbr->len);
+			ubifs_copy_hash(c, zbr->hash, ubifs_branch_hash(c, br));
+			if (!zbr->lnum || !zbr->len) {
+				ubifs_err(c, "bad ref in znode");
+				ubifs_dump_znode(c, znode);
+				if (zbr->znode)
+					ubifs_dump_znode(c, zbr->znode);
+
+				return -EINVAL;
+			}
+		}
+		len = ubifs_idx_node_sz(c, znode->child_cnt);
+		ubifs_prepare_node(c, idx, len, 0);
+		ubifs_node_calc_hash(c, idx, hash);
+
+		mutex_lock(&c->tnc_mutex);
+
+		if (znode->cparent)
+			ubifs_copy_hash(c, hash,
+					znode->cparent->zbranch[znode->ciip].hash);
+
+		if (znode->parent) {
+			if (!ubifs_zn_obsolete(znode))
+				ubifs_copy_hash(c, hash,
+					znode->parent->zbranch[znode->iip].hash);
+		} else {
+			ubifs_copy_hash(c, hash, c->zroot.hash);
+		}
+
+		mutex_unlock(&c->tnc_mutex);
+
+		/* Determine the index node position */
+		if (lnum == -1) {
+			lnum = c->ilebs[lnum_pos++];
+			buf_offs = 0;
+			used = 0;
+			avail = buf_len;
+		}
+		offs = buf_offs + used;
+
+		if (lnum != znode->lnum || offs != znode->offs ||
+		    len != znode->len) {
+			ubifs_err(c, "inconsistent znode posn");
+			return -EINVAL;
+		}
+
+		/* Grab some stuff from znode while we still can */
+		cnext = znode->cnext;
+
+		ubifs_assert(c, ubifs_zn_dirty(znode));
+		ubifs_assert(c, ubifs_zn_cow(znode));
+
+		/*
+		 * It is important that other threads should see %DIRTY_ZNODE
+		 * flag cleared before %COW_ZNODE. Specifically, it matters in
+		 * the 'dirty_cow_znode()' function. This is the reason for the
+		 * first barrier. Also, we want the bit changes to be seen to
+		 * other threads ASAP, to avoid unnecessary copying, which is
+		 * the reason for the second barrier.
+		 */
+		clear_bit(DIRTY_ZNODE, &znode->flags);
+		smp_mb__before_atomic();
+		clear_bit(COW_ZNODE, &znode->flags);
+		smp_mb__after_atomic();
+
+		/*
+		 * We have marked the znode as clean but have not updated the
+		 * @c->clean_zn_cnt counter. If this znode becomes dirty again
+		 * before 'free_obsolete_znodes()' is called, then
+		 * @c->clean_zn_cnt will be decremented before it gets
+		 * incremented (resulting in 2 decrements for the same znode).
+		 * This means that @c->clean_zn_cnt may become negative for a
+		 * while.
+		 *
+		 * Q: why we cannot increment @c->clean_zn_cnt?
+		 * A: because we do not have the @c->tnc_mutex locked, and the
+		 *    following code would be racy and buggy:
+		 *
+		 *    if (!ubifs_zn_obsolete(znode)) {
+		 *            atomic_long_inc(&c->clean_zn_cnt);
+		 *            atomic_long_inc(&ubifs_clean_zn_cnt);
+		 *    }
+		 *
+		 *    Thus, we just delay the @c->clean_zn_cnt update until we
+		 *    have the mutex locked.
+		 */
+
+		/* Do not access znode from this point on */
+
+		/* Update buffer positions */
+		wlen = used + len;
+		used += ALIGN(len, 8);
+		avail -= ALIGN(len, 8);
+
+		/*
+		 * Calculate the next index node length to see if there is
+		 * enough room for it
+		 */
+		if (cnext == c->cnext)
+			next_len = 0;
+		else
+			next_len = ubifs_idx_node_sz(c, cnext->child_cnt);
+
+		nxt_offs = buf_offs + used + next_len;
+		if (next_len && nxt_offs <= c->leb_size) {
+			if (avail > 0)
+				continue;
+			else
+				blen = buf_len;
+		} else {
+			wlen = ALIGN(wlen, 8);
+			blen = ALIGN(wlen, c->min_io_size);
+			ubifs_pad(c, c->cbuf + wlen, blen - wlen);
+		}
+
+		/* The buffer is full or there are no more znodes to do */
+		err = ubifs_leb_write(c, lnum, c->cbuf, buf_offs, blen);
+		if (err)
+			return err;
+		buf_offs += blen;
+		if (next_len) {
+			if (nxt_offs > c->leb_size) {
+				err = ubifs_update_one_lp(c, lnum, LPROPS_NC, 0,
+							  0, LPROPS_TAKEN);
+				if (err)
+					return err;
+				lnum = -1;
+			}
+			used -= blen;
+			if (used < 0)
+				used = 0;
+			avail = buf_len - used;
+			memmove(c->cbuf, c->cbuf + blen, used);
+			continue;
+		}
+		break;
+	}
+
+	if (lnum != c->dbg->new_ihead_lnum ||
+	    buf_offs != c->dbg->new_ihead_offs) {
+		ubifs_err(c, "inconsistent ihead");
+		return -EINVAL;
+	}
+
+	c->ihead_lnum = lnum;
+	c->ihead_offs = buf_offs;
+
+	return 0;
+}
+
+/**
+ * free_obsolete_znodes - free obsolete znodes.
+ * @c: UBIFS file-system description object
+ *
+ * At the end of commit end, obsolete znodes are freed.
+ */
+static void free_obsolete_znodes(struct ubifs_info *c)
+{
+	struct ubifs_znode *znode, *cnext;
+
+	cnext = c->cnext;
+	do {
+		znode = cnext;
+		cnext = znode->cnext;
+		if (ubifs_zn_obsolete(znode))
+			kfree(znode);
+		else {
+			znode->cnext = NULL;
+			atomic_long_inc(&c->clean_zn_cnt);
+			atomic_long_inc(&ubifs_clean_zn_cnt);
+		}
+	} while (cnext != c->cnext);
+}
+
+/**
+ * return_gap_lebs - return LEBs used by the in-gap commit method.
+ * @c: UBIFS file-system description object
+ *
+ * This function clears the "taken" flag for the LEBs which were used by the
+ * "commit in-the-gaps" method.
+ */
+static int return_gap_lebs(struct ubifs_info *c)
+{
+	int *p, err;
+
+	if (!c->gap_lebs)
+		return 0;
+
+	dbg_cmt("");
+	for (p = c->gap_lebs; *p != -1; p++) {
+		err = ubifs_change_one_lp(c, *p, LPROPS_NC, LPROPS_NC, 0,
+					  LPROPS_TAKEN, 0);
+		if (err)
+			return err;
+	}
+
+	kfree(c->gap_lebs);
+	c->gap_lebs = NULL;
+	return 0;
+}
+
+/**
+ * ubifs_tnc_end_commit - update the TNC for commit end.
+ * @c: UBIFS file-system description object
+ *
+ * Write the dirty znodes.
+ */
+int ubifs_tnc_end_commit(struct ubifs_info *c)
+{
+	int err;
+
+	if (!c->cnext)
+		return 0;
+
+	err = return_gap_lebs(c);
+	if (err)
+		return err;
+
+	err = write_index(c);
+	if (err)
+		return err;
+
+	mutex_lock(&c->tnc_mutex);
+
+	dbg_cmt("TNC height is %d", c->zroot.znode->level + 1);
+
+	free_obsolete_znodes(c);
+
+	c->cnext = NULL;
+	kfree(c->ilebs);
+	c->ilebs = NULL;
+
+	mutex_unlock(&c->tnc_mutex);
+
+	return 0;
+}