dir.c

linux环境下基于FAT的文件系统的通用代码

	loff_t cpos;
	int count = 0;

	bh = NULL;
	cpos = 0;
	while (fat_get_short_entry(dir, &cpos, &bh, &de) >= 0) {
		if (de->attr & ATTR_DIR)
			count++;
	}
	brelse(bh);
	return count;
}

/*
 * Scans a directory for a given file (name points to its formatted name).
 * Returns an error code or zero.
 */
int fat_scan(struct inode *dir, const unsigned char *name,
	     struct fat_slot_info *sinfo)
{
	struct super_block *sb = dir->i_sb;

	sinfo->slot_off = 0;
	sinfo->bh = NULL;
	while (fat_get_short_entry(dir, &sinfo->slot_off, &sinfo->bh,
				   &sinfo->de) >= 0) {
		if (!strncmp(sinfo->de->name, name, MSDOS_NAME)) {
			sinfo->slot_off -= sizeof(*sinfo->de);
			sinfo->nr_slots = 1;
			sinfo->i_pos = fat_make_i_pos(sb, sinfo->bh, sinfo->de);
			return 0;
		}
	}
	return -ENOENT;
}

EXPORT_SYMBOL_GPL(fat_scan);

static int __fat_remove_entries(struct inode *dir, loff_t pos, int nr_slots)
{
	struct super_block *sb = dir->i_sb;
	struct buffer_head *bh;
	struct msdos_dir_entry *de, *endp;
	int err = 0, orig_slots;

	while (nr_slots) {
		bh = NULL;
		if (fat_get_entry(dir, &pos, &bh, &de) < 0) {
			err = -EIO;
			break;
		}

		orig_slots = nr_slots;
		endp = (struct msdos_dir_entry *)(bh->b_data + sb->s_blocksize);
		while (nr_slots && de < endp) {
			de->name[0] = DELETED_FLAG;
			de++;
			nr_slots--;
		}
		mark_buffer_dirty(bh);
		if (IS_DIRSYNC(dir))
			err = sync_dirty_buffer(bh);
		brelse(bh);
		if (err)
			break;

		/* pos is *next* de's position, so this does `- sizeof(de)' */
		pos += ((orig_slots - nr_slots) * sizeof(*de)) - sizeof(*de);
	}

	return err;
}

int fat_remove_entries(struct inode *dir, struct fat_slot_info *sinfo)
{
	struct msdos_dir_entry *de;
	struct buffer_head *bh;
	int err = 0, nr_slots;

	/*
	 * First stage: Remove the shortname. By this, the directory
	 * entry is removed.
	 */
	nr_slots = sinfo->nr_slots;
	de = sinfo->de;
	sinfo->de = NULL;
	bh = sinfo->bh;
	sinfo->bh = NULL;
	while (nr_slots && de >= (struct msdos_dir_entry *)bh->b_data) {
		de->name[0] = DELETED_FLAG;
		de--;
		nr_slots--;
	}
	mark_buffer_dirty(bh);
	if (IS_DIRSYNC(dir))
		err = sync_dirty_buffer(bh);
	brelse(bh);
	if (err)
		return err;
	dir->i_version++;

	if (nr_slots) {
		/*
		 * Second stage: remove the remaining longname slots.
		 * (This directory entry is already removed, and so return
		 * the success)
		 */
		err = __fat_remove_entries(dir, sinfo->slot_off, nr_slots);
		if (err) {
			printk(KERN_WARNING
			       "FAT: Couldn't remove the long name slots\n");
		}
	}

	dir->i_mtime = dir->i_atime = CURRENT_TIME_SEC;
	if (IS_DIRSYNC(dir))
		(void)fat_sync_inode(dir);
	else
		mark_inode_dirty(dir);

	return 0;
}

EXPORT_SYMBOL_GPL(fat_remove_entries);

static int fat_zeroed_cluster(struct inode *dir, sector_t blknr, int nr_used,
			      struct buffer_head **bhs, int nr_bhs)
{
	struct super_block *sb = dir->i_sb;
	sector_t last_blknr = blknr + MSDOS_SB(sb)->sec_per_clus;
	int err, i, n;

	/* Zeroing the unused blocks on this cluster */
	blknr += nr_used;
	n = nr_used;
	while (blknr < last_blknr) {
		bhs[n] = sb_getblk(sb, blknr);
		if (!bhs[n]) {
			err = -ENOMEM;
			goto error;
		}
		memset(bhs[n]->b_data, 0, sb->s_blocksize);
		set_buffer_uptodate(bhs[n]);
		mark_buffer_dirty(bhs[n]);

		n++;
		blknr++;
		if (n == nr_bhs) {
			if (IS_DIRSYNC(dir)) {
				err = fat_sync_bhs(bhs, n);
				if (err)
					goto error;
			}
			for (i = 0; i < n; i++)
				brelse(bhs[i]);
			n = 0;
		}
	}
	if (IS_DIRSYNC(dir)) {
		err = fat_sync_bhs(bhs, n);
		if (err)
			goto error;
	}
	for (i = 0; i < n; i++)
		brelse(bhs[i]);

	return 0;

error:
	for (i = 0; i < n; i++)
		bforget(bhs[i]);
	return err;
}

int fat_alloc_new_dir(struct inode *dir, struct timespec *ts)
{
	struct super_block *sb = dir->i_sb;
	struct msdos_sb_info *sbi = MSDOS_SB(sb);
	struct buffer_head *bhs[MAX_BUF_PER_PAGE];
	struct msdos_dir_entry *de;
	sector_t blknr;
	__le16 date, time;
	u8 time_cs;
	int err, cluster;

	err = fat_alloc_clusters(dir, &cluster, 1);
	if (err)
		goto error;

	blknr = fat_clus_to_blknr(sbi, cluster);
	bhs[0] = sb_getblk(sb, blknr);
	if (!bhs[0]) {
		err = -ENOMEM;
		goto error_free;
	}

	fat_time_unix2fat(sbi, ts, &time, &date, &time_cs);

	de = (struct msdos_dir_entry *)bhs[0]->b_data;
	/* filling the new directory slots ("." and ".." entries) */
	memcpy(de[0].name, MSDOS_DOT, MSDOS_NAME);
	memcpy(de[1].name, MSDOS_DOTDOT, MSDOS_NAME);
	de->attr = de[1].attr = ATTR_DIR;
	de[0].lcase = de[1].lcase = 0;
	de[0].time = de[1].time = time;
	de[0].date = de[1].date = date;
	if (sbi->options.isvfat) {
		/* extra timestamps */
		de[0].ctime = de[1].ctime = time;
		de[0].ctime_cs = de[1].ctime_cs = time_cs;
		de[0].adate = de[0].cdate = de[1].adate = de[1].cdate = date;
	} else {
		de[0].ctime = de[1].ctime = 0;
		de[0].ctime_cs = de[1].ctime_cs = 0;
		de[0].adate = de[0].cdate = de[1].adate = de[1].cdate = 0;
	}
	de[0].start = cpu_to_le16(cluster);
	de[0].starthi = cpu_to_le16(cluster >> 16);
	de[1].start = cpu_to_le16(MSDOS_I(dir)->i_logstart);
	de[1].starthi = cpu_to_le16(MSDOS_I(dir)->i_logstart >> 16);
	de[0].size = de[1].size = 0;
	memset(de + 2, 0, sb->s_blocksize - 2 * sizeof(*de));
	set_buffer_uptodate(bhs[0]);
	mark_buffer_dirty(bhs[0]);

	err = fat_zeroed_cluster(dir, blknr, 1, bhs, MAX_BUF_PER_PAGE);
	if (err)
		goto error_free;

	return cluster;

error_free:
	fat_free_clusters(dir, cluster);
error:
	return err;
}

EXPORT_SYMBOL_GPL(fat_alloc_new_dir);

static int fat_add_new_entries(struct inode *dir, void *slots, int nr_slots,
			       int *nr_cluster, struct msdos_dir_entry **de,
			       struct buffer_head **bh, loff_t *i_pos)
{
	struct super_block *sb = dir->i_sb;
	struct msdos_sb_info *sbi = MSDOS_SB(sb);
	struct buffer_head *bhs[MAX_BUF_PER_PAGE];
	sector_t blknr, start_blknr, last_blknr;
	unsigned long size, copy;
	int err, i, n, offset, cluster[2];

	/*
	 * The minimum cluster size is 512bytes, and maximum entry
	 * size is 32*slots (672bytes).  So, iff the cluster size is
	 * 512bytes, we may need two clusters.
	 */
	size = nr_slots * sizeof(struct msdos_dir_entry);
	*nr_cluster = (size + (sbi->cluster_size - 1)) >> sbi->cluster_bits;
	BUG_ON(*nr_cluster > 2);

	err = fat_alloc_clusters(dir, cluster, *nr_cluster);
	if (err)
		goto error;

	/*
	 * First stage: Fill the directory entry.  NOTE: This cluster
	 * is not referenced from any inode yet, so updates order is
	 * not important.
	 */
	i = n = copy = 0;
	do {
		start_blknr = blknr = fat_clus_to_blknr(sbi, cluster[i]);
		last_blknr = start_blknr + sbi->sec_per_clus;
		while (blknr < last_blknr) {
			bhs[n] = sb_getblk(sb, blknr);
			if (!bhs[n]) {
				err = -ENOMEM;
				goto error_nomem;
			}

			/* fill the directory entry */
			copy = min(size, sb->s_blocksize);
			memcpy(bhs[n]->b_data, slots, copy);
			slots += copy;
			size -= copy;
			set_buffer_uptodate(bhs[n]);
			mark_buffer_dirty(bhs[n]);
			if (!size)
				break;
			n++;
			blknr++;
		}
	} while (++i < *nr_cluster);

	memset(bhs[n]->b_data + copy, 0, sb->s_blocksize - copy);
	offset = copy - sizeof(struct msdos_dir_entry);
	get_bh(bhs[n]);
	*bh = bhs[n];
	*de = (struct msdos_dir_entry *)((*bh)->b_data + offset);
	*i_pos = fat_make_i_pos(sb, *bh, *de);

	/* Second stage: clear the rest of cluster, and write outs */
	err = fat_zeroed_cluster(dir, start_blknr, ++n, bhs, MAX_BUF_PER_PAGE);
	if (err)
		goto error_free;

	return cluster[0];

error_free:
	brelse(*bh);
	*bh = NULL;
	n = 0;
error_nomem:
	for (i = 0; i < n; i++)
		bforget(bhs[i]);
	fat_free_clusters(dir, cluster[0]);
error:
	return err;
}

int fat_add_entries(struct inode *dir, void *slots, int nr_slots,
		    struct fat_slot_info *sinfo)
{
	struct super_block *sb = dir->i_sb;
	struct msdos_sb_info *sbi = MSDOS_SB(sb);
	struct buffer_head *bh, *prev, *bhs[3]; /* 32*slots (672bytes) */
	struct msdos_dir_entry *de;
	int err, free_slots, i, nr_bhs;
	loff_t pos, i_pos;

	sinfo->nr_slots = nr_slots;

	/* First stage: search free direcotry entries */
	free_slots = nr_bhs = 0;
	bh = prev = NULL;
	pos = 0;
	err = -ENOSPC;
	while (fat_get_entry(dir, &pos, &bh, &de) > -1) {
		/* check the maximum size of directory */
		if (pos >= FAT_MAX_DIR_SIZE)
			goto error;

		if (IS_FREE(de->name)) {
			if (prev != bh) {
				get_bh(bh);
				bhs[nr_bhs] = prev = bh;
				nr_bhs++;
			}
			free_slots++;
			if (free_slots == nr_slots)
				goto found;
		} else {
			for (i = 0; i < nr_bhs; i++)
				brelse(bhs[i]);
			prev = NULL;
			free_slots = nr_bhs = 0;
		}
	}
	if (dir->i_ino == MSDOS_ROOT_INO) {
		if (sbi->fat_bits != 32)
			goto error;
	} else if (MSDOS_I(dir)->i_start == 0) {
		printk(KERN_ERR "FAT: Corrupted directory (i_pos %lld)\n",
		       MSDOS_I(dir)->i_pos);
		err = -EIO;
		goto error;
	}

found:
	err = 0;
	pos -= free_slots * sizeof(*de);
	nr_slots -= free_slots;
	if (free_slots) {
		/*
		 * Second stage: filling the free entries with new entries.
		 * NOTE: If this slots has shortname, first, we write
		 * the long name slots, then write the short name.
		 */
		int size = free_slots * sizeof(*de);
		int offset = pos & (sb->s_blocksize - 1);
		int long_bhs = nr_bhs - (nr_slots == 0);

		/* Fill the long name slots. */
		for (i = 0; i < long_bhs; i++) {
			int copy = min_t(int, sb->s_blocksize - offset, size);
			memcpy(bhs[i]->b_data + offset, slots, copy);
			mark_buffer_dirty(bhs[i]);
			offset = 0;
			slots += copy;
			size -= copy;
		}
		if (long_bhs && IS_DIRSYNC(dir))
			err = fat_sync_bhs(bhs, long_bhs);
		if (!err && i < nr_bhs) {
			/* Fill the short name slot. */
			int copy = min_t(int, sb->s_blocksize - offset, size);
			memcpy(bhs[i]->b_data + offset, slots, copy);
			mark_buffer_dirty(bhs[i]);
			if (IS_DIRSYNC(dir))
				err = sync_dirty_buffer(bhs[i]);
		}
		for (i = 0; i < nr_bhs; i++)
			brelse(bhs[i]);
		if (err)
			goto error_remove;
	}

	if (nr_slots) {
		int cluster, nr_cluster;

		/*
		 * Third stage: allocate the cluster for new entries.
		 * And initialize the cluster with new entries, then
		 * add the cluster to dir.
		 */
		cluster = fat_add_new_entries(dir, slots, nr_slots, &nr_cluster,
					      &de, &bh, &i_pos);
		if (cluster < 0) {
			err = cluster;
			goto error_remove;
		}
		err = fat_chain_add(dir, cluster, nr_cluster);
		if (err) {
			fat_free_clusters(dir, cluster);
			goto error_remove;
		}
		if (dir->i_size & (sbi->cluster_size - 1)) {
			fat_fs_panic(sb, "Odd directory size");
			dir->i_size = (dir->i_size + sbi->cluster_size - 1)
				& ~((loff_t)sbi->cluster_size - 1);
		}
		dir->i_size += nr_cluster << sbi->cluster_bits;
		MSDOS_I(dir)->mmu_private += nr_cluster << sbi->cluster_bits;
	}
	sinfo->slot_off = pos;
	sinfo->de = de;
	sinfo->bh = bh;
	sinfo->i_pos = fat_make_i_pos(sb, sinfo->bh, sinfo->de);

	return 0;

error:
	brelse(bh);
	for (i = 0; i < nr_bhs; i++)
		brelse(bhs[i]);
	return err;

error_remove:
	brelse(bh);
	if (free_slots)
		__fat_remove_entries(dir, pos, free_slots);
	return err;
}

EXPORT_SYMBOL_GPL(fat_add_entries);