super.c

LINUX1.0内核源代码,学习LINUX编程的一定要看。

		    gdp->bg_inode_table + sb->u.ext2_sb.s_itb_per_group >=
		    block + EXT2_BLOCKS_PER_GROUP(sb))
		{
			ext2_error (sb, "ext2_check_desciptors",
				    "Inode table for group %d"
				    " not in group (block %lu)!",
				    i, gdp->bg_inode_table);
			return 0;
		}
		block += EXT2_BLOCKS_PER_GROUP(sb);
		gdp++;
	}
	return 1;
}

struct super_block * ext2_read_super (struct super_block * sb, void * data,
				      int silent)
{
	struct buffer_head * bh;
	struct ext2_super_block * es;
	unsigned long sb_block = 1;
	unsigned long logic_sb_block = 1;
	int dev = sb->s_dev;
	int bh_count;
	int i, j;
#ifdef EXT2FS_PRE_02B_COMPAT
	int fs_converted = 0;
#endif

	set_opt (sb->u.ext2_sb.s_mount_opt, CHECK_NORMAL);
	if (!parse_options ((char *) data, &sb_block,
	    &sb->u.ext2_sb.s_mount_opt)) {
		sb->s_dev = 0;
		return NULL;
	}

	lock_super (sb);
	set_blocksize (dev, BLOCK_SIZE);
	if (!(bh = bread (dev, sb_block, BLOCK_SIZE))) {
		sb->s_dev = 0;
		unlock_super (sb);
		printk ("EXT2-fs: unable to read superblock\n");
		return NULL;
	}
	/*
	 * Note: s_es must be initialized s_es as soon as possible because
	 * some ext2 macro-instructions depend on its value
	 */
	es = (struct ext2_super_block *) bh->b_data;
	sb->u.ext2_sb.s_es = es;
	sb->s_magic = es->s_magic;
	if (sb->s_magic != EXT2_SUPER_MAGIC
#ifdef EXT2FS_PRE_02B_COMPAT
	   && sb->s_magic != EXT2_PRE_02B_MAGIC
#endif
	   ) {
		sb->s_dev = 0;
		unlock_super (sb);
		brelse (bh);
		if (!silent)
			printk ("VFS: Can't find an ext2 filesystem on dev %d/%d.\n",
				MAJOR(dev), MINOR(dev));
		return NULL;
	}
	sb->s_blocksize = EXT2_MIN_BLOCK_SIZE << es->s_log_block_size;
	sb->s_blocksize_bits = EXT2_BLOCK_SIZE_BITS(sb);
	if (sb->s_blocksize != BLOCK_SIZE && 
	    (sb->s_blocksize == 1024 || sb->s_blocksize == 2048 ||  
	     sb->s_blocksize == 4096)) {
		unsigned long offset;

		brelse (bh);
		set_blocksize (dev, sb->s_blocksize);
		logic_sb_block = sb_block / sb->s_blocksize;
		offset = sb_block % sb->s_blocksize;
		bh = bread (dev, logic_sb_block, sb->s_blocksize);
		if(!bh)
			return NULL;
		es = (struct ext2_super_block *) (((char *)bh->b_data) + offset);
		sb->u.ext2_sb.s_es = es;
		if (es->s_magic != EXT2_SUPER_MAGIC) {
			sb->s_dev = 0;
			unlock_super (sb);
			brelse (bh);
			printk ("EXT2-fs: Magic mismatch, very weird !\n");
			return NULL;
		}
	}
	sb->u.ext2_sb.s_frag_size = EXT2_MIN_FRAG_SIZE <<
				   es->s_log_frag_size;
	if (sb->u.ext2_sb.s_frag_size)
		sb->u.ext2_sb.s_frags_per_block = sb->s_blocksize /
						  sb->u.ext2_sb.s_frag_size;
	else
		sb->s_magic = 0;
	sb->u.ext2_sb.s_blocks_per_group = es->s_blocks_per_group;
	sb->u.ext2_sb.s_frags_per_group = es->s_frags_per_group;
	sb->u.ext2_sb.s_inodes_per_group = es->s_inodes_per_group;
	sb->u.ext2_sb.s_inodes_per_block = sb->s_blocksize /
					   sizeof (struct ext2_inode);
	sb->u.ext2_sb.s_itb_per_group = sb->u.ext2_sb.s_inodes_per_group /
				        sb->u.ext2_sb.s_inodes_per_block;
	sb->u.ext2_sb.s_desc_per_block = sb->s_blocksize /
					 sizeof (struct ext2_group_desc);
	sb->u.ext2_sb.s_sbh = bh;
	sb->u.ext2_sb.s_es = es;
	sb->u.ext2_sb.s_mount_state = es->s_state;
	sb->u.ext2_sb.s_rename_lock = 0;
	sb->u.ext2_sb.s_rename_wait = NULL;
#ifdef EXT2FS_PRE_02B_COMPAT
	if (sb->s_magic == EXT2_PRE_02B_MAGIC) {
		if (es->s_blocks_count > 262144) {
			/*
			 * fs > 256 MB can't be converted
			 */ 
			sb->s_dev = 0;
			unlock_super (sb);
			brelse (bh);
			printk ("EXT2-fs: trying to mount a pre-0.2b file"
				"system which cannot be converted\n");
			return NULL;
		}
		printk ("EXT2-fs: mounting a pre 0.2b file system, "
			"will try to convert the structure\n");
		if (!(sb->s_flags & MS_RDONLY)) {
			sb->s_dev = 0;
			unlock_super (sb);
			brelse (bh);
			printk ("EXT2-fs: cannot convert a read-only fs\n");
			return NULL;
		}
		if (!convert_pre_02b_fs (sb, bh)) {
			sb->s_dev = 0;
			unlock_super (sb);
			brelse (bh);
			printk ("EXT2-fs: conversion failed !!!\n");
			return NULL;
		}
		printk ("EXT2-fs: conversion succeeded !!!\n");
		fs_converted = 1;
	}
#endif
	if (sb->s_magic != EXT2_SUPER_MAGIC) {
		sb->s_dev = 0;
		unlock_super (sb);
		brelse (bh);
		if (!silent)
			printk ("VFS: Can't find an ext2 filesystem on dev %d/%d.\n",
				MAJOR(dev), MINOR(dev));
		return NULL;
	}
	if (sb->s_blocksize != bh->b_size) {
		sb->s_dev = 0;
		unlock_super (sb);
		brelse (bh);
		if (!silent)
			printk ("VFS: Unsupported blocksize on dev 0x%04x.\n",
				dev);
		return NULL;
	}

	if (sb->s_blocksize != sb->u.ext2_sb.s_frag_size) {
		sb->s_dev = 0;
		unlock_super (sb);
		brelse (bh);
		printk ("EXT2-fs: fragsize %lu != blocksize %lu (not supported yet)\n",
			sb->u.ext2_sb.s_frag_size, sb->s_blocksize);
		return NULL;
	}

	sb->u.ext2_sb.s_groups_count = (es->s_blocks_count -
				        es->s_first_data_block +
				       EXT2_BLOCKS_PER_GROUP(sb) - 1) /
				       EXT2_BLOCKS_PER_GROUP(sb);
	for (i = 0; i < EXT2_MAX_GROUP_DESC; i++)
		sb->u.ext2_sb.s_group_desc[i] = NULL;
	bh_count = (sb->u.ext2_sb.s_groups_count + EXT2_DESC_PER_BLOCK(sb) - 1) /
		   EXT2_DESC_PER_BLOCK(sb);
	if (bh_count > EXT2_MAX_GROUP_DESC) {
		sb->s_dev = 0;
		unlock_super (sb);
		brelse (bh);
		printk ("EXT2-fs: file system is too big\n");
		return NULL;
	}
	for (i = 0; i < bh_count; i++) {
		sb->u.ext2_sb.s_group_desc[i] = bread (dev, logic_sb_block + i + 1,
						       sb->s_blocksize);
		if (!sb->u.ext2_sb.s_group_desc[i]) {
			sb->s_dev = 0;
			unlock_super (sb);
			for (j = 0; j < i; j++)
				brelse (sb->u.ext2_sb.s_group_desc[j]);
			brelse (bh);
			printk ("EXT2-fs: unable to read group descriptors\n");
			return NULL;
		}
	}
	if (!ext2_check_descriptors (sb)) {
		sb->s_dev = 0;
		unlock_super (sb);
		for (j = 0; j < i; j++)
			brelse (sb->u.ext2_sb.s_group_desc[j]);
		brelse (bh);
		printk ("EXT2-fs: group descriptors corrupted !\n");
		return NULL;
	}
	for (i = 0; i < EXT2_MAX_GROUP_LOADED; i++) {
		sb->u.ext2_sb.s_inode_bitmap_number[i] = 0;
		sb->u.ext2_sb.s_inode_bitmap[i] = NULL;
		sb->u.ext2_sb.s_block_bitmap_number[i] = 0;
		sb->u.ext2_sb.s_block_bitmap[i] = NULL;
	}
	sb->u.ext2_sb.s_loaded_inode_bitmaps = 0;
	sb->u.ext2_sb.s_loaded_block_bitmaps = 0;
	unlock_super (sb);
	/*
	 * set up enough so that it can read an inode
	 */
	sb->s_dev = dev;
	sb->s_op = &ext2_sops;
	if (!(sb->s_mounted = iget (sb, EXT2_ROOT_INO))) {
		sb->s_dev = 0;
		for (i = 0; i < EXT2_MAX_GROUP_DESC; i++)
			if (sb->u.ext2_sb.s_group_desc[i])
				brelse (sb->u.ext2_sb.s_group_desc[i]);
		brelse (bh);
		printk ("EXT2-fs: get root inode failed\n");
		return NULL;
	}
#ifdef EXT2FS_PRE_02B_COMPAT
	if (fs_converted) {
		for (i = 0; i < bh_count; i++)
			sb->u.ext2_sb.s_group_desc[i]->b_dirt = 1;
		sb->s_dirt = 1;
	}
#endif
	ext2_setup_super (sb, es);
	return sb;
}

static void ext2_commit_super (struct super_block * sb,
			       struct ext2_super_block * es)
{
	es->s_wtime = CURRENT_TIME;
	sb->u.ext2_sb.s_sbh->b_dirt = 1;
	sb->s_dirt = 0;
}

/*
 * In the second extended file system, it is not necessary to
 * write the super block since we use a mapping of the
 * disk super block in a buffer.
 *
 * However, this function is still used to set the fs valid
 * flags to 0.  We need to set this flag to 0 since the fs
 * may have been checked while mounted and e2fsck may have
 * set s_state to EXT2_VALID_FS after some corrections.
 */

void ext2_write_super (struct super_block * sb)
{
	struct ext2_super_block * es;

	if (!(sb->s_flags & MS_RDONLY)) {
		es = sb->u.ext2_sb.s_es;

		ext2_debug ("setting valid to 0\n");

		if (es->s_state & EXT2_VALID_FS) {
			es->s_state &= ~EXT2_VALID_FS;
			es->s_mtime = CURRENT_TIME;
		}
		ext2_commit_super (sb, es);
	}
	sb->s_dirt = 0;
}

int ext2_remount (struct super_block * sb, int * flags, char * data)
{
	struct ext2_super_block * es;
	unsigned long tmp;

	/*
	 * Allow the "check" option to be passed as a remount option.
	 */
	set_opt (sb->u.ext2_sb.s_mount_opt, CHECK_NORMAL);
	parse_options (data, &tmp, &sb->u.ext2_sb.s_mount_opt);

	es = sb->u.ext2_sb.s_es;
	if ((*flags & MS_RDONLY) == (sb->s_flags & MS_RDONLY))
		return 0;
	if (*flags & MS_RDONLY) {
		if (es->s_state & EXT2_VALID_FS ||
		    !(sb->u.ext2_sb.s_mount_state & EXT2_VALID_FS))
			return 0;
		/*
		 * OK, we are remounting a valid rw partition rdonly, so set
		 * the rdonly flag and then mark the partition as valid again.
		 */
		es->s_state = sb->u.ext2_sb.s_mount_state;
		es->s_mtime = CURRENT_TIME;
		sb->u.ext2_sb.s_sbh->b_dirt = 1;
		sb->s_dirt = 1;
		ext2_commit_super (sb, es);
	}
	else {
		/*
		 * Mounting a RDONLY partition read-write, so reread and
		 * store the current valid flag.  (It may have been changed 
		 * by e2fsck since we originally mounted the partition.)
		 */
		sb->u.ext2_sb.s_mount_state = es->s_state;
		sb->s_flags &= ~MS_RDONLY;
		ext2_setup_super (sb, es);
	}
	return 0;
}

void ext2_statfs (struct super_block * sb, struct statfs * buf)
{
	long tmp;

	put_fs_long (EXT2_SUPER_MAGIC, &buf->f_type);
	put_fs_long (sb->s_blocksize, &buf->f_bsize);
	put_fs_long (sb->u.ext2_sb.s_es->s_blocks_count, &buf->f_blocks);
	tmp = ext2_count_free_blocks (sb);
	put_fs_long (tmp, &buf->f_bfree);
	if (tmp >= sb->u.ext2_sb.s_es->s_r_blocks_count)
		put_fs_long (tmp - sb->u.ext2_sb.s_es->s_r_blocks_count,
			     &buf->f_bavail);
	else
		put_fs_long (0, &buf->f_bavail);
	put_fs_long (sb->u.ext2_sb.s_es->s_inodes_count, &buf->f_files);
	put_fs_long (ext2_count_free_inodes (sb), &buf->f_ffree);
	put_fs_long (EXT2_NAME_LEN, &buf->f_namelen);
	/* Don't know what value to put in buf->f_fsid */
}