Merge tag 'trace-v7.3-2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-tracegrafted

Pull tracing fixes from Steven Rostedt:

 - Fix error output of boot instance creation failure

   Currently if a boot instance creation fails, instead of printing out
   the name of the instance that failed, it prints "(null)". That is
   because it prints "cur_str" that had already been processed by
   strsep(). Print the saved name instead.

   While at it, print the error code of the failure.

 - Fix use-after-free for same named historgrams

   Histograms can be named so that they can be used in multiple events.
   But if the named histogram has a variable attached, the second event
   that uses the named histogram which duplicates it and needs to free
   the original after duplication leaves the old variable in place and
   still visible. If another histogram uses than variable, it will use
   the stale one which will try to reference the freed duplicate
   histogram and crash the kernel.

   Free the duplicate variables along with the duplicated histogram
   data.

 - Check return value of kthread_run() in event self test

   The events self tests uses a kthread for testing but does not check
   if it succeeded in creating a kthread. If the kthread creation were
   to fail, the code will still try to call kthread_stop() on the error
   returned.

 - Fix race between reading trace_pipe and updating subbuffer size

   If a user is reading the trace_pipe file at the same time they update
   the ring buffer sub-buffer size, can cause the trace_pipe read to
   read stale data. Add trace_access_lock() around updating the ring
   buffer sub-buffer size.

 - Fix eventfs_inode on failure path in creation of the events directory

   In the creation of the "events" directory, if after allocating the
   eventfs_inode a failure is detected, it calls cleanup_ei() which
   calls free_ei(). The free_ei() will test if eventfs_inode being freed
   has no children. It is a bug if it does. But on the failure case of
   the creation of the "events" directory, the children lists have not
   yet been initialized and the free will trigger a warning because
   list_empty() on an uninitialized list returns false.

   Move the initialization into init_ei() where it makes more sense and
   makes sure that a created eventfs_inode has its lists initialized
   upon creation.

 - Check return value of kthread_run() in ftrace direct sample code

   The sample code that shows how to use the ftrace direct calls does
   not test the return of kthread_run() to see if it succeeds. Return a
   failure if the kthread_run() doesn't succeed.

 - Clear user events state on fork in case of alloc failure

   On fork, the child gets a pointer to the parent's user events state.
   It makes a copy of it then updates the child's pointer to it. But if
   the allocation fails, the duplication function leaves the child with
   a pointer to its parent's descriptor. When the child cleans up its
   data, it will free the parent's descriptor while the parent is still
   using it.

   In the duplication function, set the child's user_event_mm to NULL
   before testing if the allocation succeeded, and when it exits it will
   not free the parent's descriptor.

 - Fix retry exhaustion in simple ring buffer reader swap

   simple_ring_buffer_swap_reader_page() starts with retry set to 8 and
   post-decrements it only after a failed link replacement. On the final
   attempt, a successful replacement leaves retry at zero, while a
   failed replacement leaves it at -1.

   But the check for success expects the retry value to be non-zero and
   exits with an error on zero. This is the opposite result. Fix it.

 - Fail nicely when the remote swap_reader_page() returns an error

   Currently, if the swap_reader_page() of a remote buffer fails, it
   triggers a WARN_ON_ONCE() and continues normally. Instead, have it
   exit with an error and a pr_warn() print instead of a full WARNING.

* tag 'trace-v7.3-2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace:
  ring-buffer: Stop remote reader update when page swap fails
  tracing: Fix retry exhaustion in simple ring buffer reader swap
  tracing/user_events: Clear copied tracing state before fork duplication
  samples/ftrace: Fix kthread_stop() on ERR_PTR in ftrace-direct-multi-modify
  samples/ftrace: Fix kthread_stop() on ERR_PTR in ftrace-direct-modify
  eventfs: Initialize ei->children and ei->list in init_ei()
  tracing: Fix use-after-free in trace_pipe read on sub-buffer order change
  tracing: Fix crash passing ERR_PTR to kthread_stop()
  tracing: Fix use-after-free with same-name named triggers
  tracing: Fix logged instance name on creation failure

1 files changed, 1112 insertions, 0 deletions

diff --git a/fs/ubifs/tnc_commit.c b/fs/ubifs/tnc_commit.c
new file mode 100644
index 000000000..7bf267206
--- /dev/null
+++ b/fs/ubifs/tnc_commit.c
@@ -0,0 +1,1112 @@
+// 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_objs(int, c->lst.idx_lebs + 1, 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) {
+			ubifs_assert(c, !znode->parent);
+			znode->cparent = NULL;
+			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_objs(int, leb_cnt, 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;
+}