alloc.c

busybox最新版的源码:学习和应用的好东东,多的不说了,大家看后再说吧

/* vi: set sw=4 ts=4: */
/*
 * alloc.c --- allocate new inodes, blocks for ext2fs
 *
 * Copyright (C) 1993, 1994, 1995, 1996 Theodore Ts'o.
 *
 * %Begin-Header%
 * This file may be redistributed under the terms of the GNU Public
 * License.
 * %End-Header%
 *
 */

#include <stdio.h>
#if HAVE_UNISTD_H
#include <unistd.h>
#endif
#include <time.h>
#include <string.h>
#if HAVE_SYS_STAT_H
#include <sys/stat.h>
#endif
#if HAVE_SYS_TYPES_H
#include <sys/types.h>
#endif

#include "ext2_fs.h"
#include "ext2fs.h"

/*
 * Right now, just search forward from the parent directory's block
 * group to find the next free inode.
 *
 * Should have a special policy for directories.
 */
errcode_t ext2fs_new_inode(ext2_filsys fs, ext2_ino_t dir,
			   int mode EXT2FS_ATTR((unused)),
			   ext2fs_inode_bitmap map, ext2_ino_t *ret)
{
	ext2_ino_t	dir_group = 0;
	ext2_ino_t	i;
	ext2_ino_t	start_inode;

	EXT2_CHECK_MAGIC(fs, EXT2_ET_MAGIC_EXT2FS_FILSYS);

	if (!map)
		map = fs->inode_map;
	if (!map)
		return EXT2_ET_NO_INODE_BITMAP;

	if (dir > 0)
		dir_group = (dir - 1) / EXT2_INODES_PER_GROUP(fs->super);

	start_inode = (dir_group * EXT2_INODES_PER_GROUP(fs->super)) + 1;
	if (start_inode < EXT2_FIRST_INODE(fs->super))
		start_inode = EXT2_FIRST_INODE(fs->super);
	i = start_inode;

	do {
		if (!ext2fs_fast_test_inode_bitmap(map, i))
			break;
		i++;
		if (i > fs->super->s_inodes_count)
			i = EXT2_FIRST_INODE(fs->super);
	} while (i != start_inode);

	if (ext2fs_test_inode_bitmap(map, i))
		return EXT2_ET_INODE_ALLOC_FAIL;
	*ret = i;
	return 0;
}

/*
 * Stupid algorithm --- we now just search forward starting from the
 * goal.  Should put in a smarter one someday....
 */
errcode_t ext2fs_new_block(ext2_filsys fs, blk_t goal,
			   ext2fs_block_bitmap map, blk_t *ret)
{
	blk_t	i;

	EXT2_CHECK_MAGIC(fs, EXT2_ET_MAGIC_EXT2FS_FILSYS);

	if (!map)
		map = fs->block_map;
	if (!map)
		return EXT2_ET_NO_BLOCK_BITMAP;
	if (!goal || (goal >= fs->super->s_blocks_count))
		goal = fs->super->s_first_data_block;
	i = goal;
	do {
		if (!ext2fs_fast_test_block_bitmap(map, i)) {
			*ret = i;
			return 0;
		}
		i++;
		if (i >= fs->super->s_blocks_count)
			i = fs->super->s_first_data_block;
	} while (i != goal);
	return EXT2_ET_BLOCK_ALLOC_FAIL;
}

/*
 * This function zeros out the allocated block, and updates all of the
 * appropriate filesystem records.
 */
errcode_t ext2fs_alloc_block(ext2_filsys fs, blk_t goal,
			     char *block_buf, blk_t *ret)
{
	errcode_t	retval;
	blk_t		block;
	char		*buf = 0;

	if (!block_buf) {
		retval = ext2fs_get_mem(fs->blocksize, &buf);
		if (retval)
			return retval;
		block_buf = buf;
	}
	memset(block_buf, 0, fs->blocksize);

	if (!fs->block_map) {
		retval = ext2fs_read_block_bitmap(fs);
		if (retval)
			goto fail;
	}

	retval = ext2fs_new_block(fs, goal, 0, &block);
	if (retval)
		goto fail;

	retval = io_channel_write_blk(fs->io, block, 1, block_buf);
	if (retval)
		goto fail;

	ext2fs_block_alloc_stats(fs, block, +1);
	*ret = block;
	return 0;

fail:
	if (buf)
		ext2fs_free_mem(&buf);
	return retval;
}

errcode_t ext2fs_get_free_blocks(ext2_filsys fs, blk_t start, blk_t finish,
				 int num, ext2fs_block_bitmap map, blk_t *ret)
{
	blk_t	b = start;

	EXT2_CHECK_MAGIC(fs, EXT2_ET_MAGIC_EXT2FS_FILSYS);

	if (!map)
		map = fs->block_map;
	if (!map)
		return EXT2_ET_NO_BLOCK_BITMAP;
	if (!b)
		b = fs->super->s_first_data_block;
	if (!finish)
		finish = start;
	if (!num)
		num = 1;
	do {
		if (b+num-1 > fs->super->s_blocks_count)
			b = fs->super->s_first_data_block;
		if (ext2fs_fast_test_block_bitmap_range(map, b, num)) {
			*ret = b;
			return 0;
		}
		b++;
	} while (b != finish);
	return EXT2_ET_BLOCK_ALLOC_FAIL;
}