fs/ubifs/tnc_commit.c



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/*
 * 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 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;
	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);
		if (!zbr->lnum || !zbr->len) {
			ubifs_err("bad ref in znode");
			ubifs_dump_znode(c, znode);
			if (zbr->znode)
				ubifs_dump_znode(c, zbr->znode);
		}
	}
	ubifs_prepare_node(c, idx, len, 0);

	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;
	} else {
		c->zroot.lnum = lnum;
		c->zroot.offs = offs;
		c->zroot.len = len;
	}
	c->calc_idx_sz += ALIGN(len, 8);

	atomic_long_dec(&c->dirty_zn_cnt);

	ubifs_assert(ubifs_zn_dirty(znode));
	ubifs_assert(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((gap_start & 7) == 0);
	ubifs_assert((gap_end & 7) == 0);
	ubifs_assert(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(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 here
 *
 * 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 */
	*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(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;