super.c

ARM 嵌入式 系统 设计与实例开发 实验教材 二源码

	/*
	 * See what the current blocksize for the device is, and
	 * use that as the blocksize.  Otherwise (or if the blocksize
	 * is smaller than the default) use the default.
	 * This is important for devices that have a hardware
	 * sectorsize that is larger than the default.
	 */
	blocksize = get_hardsect_size(dev);
	if(blocksize < BLOCK_SIZE )
	    blocksize = BLOCK_SIZE;

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

	if (set_blocksize(dev, blocksize) < 0) {
		printk ("EXT2-fs: unable to set blocksize %d\n", blocksize);
		return NULL;
	}
	sb->s_blocksize = blocksize;

	/*
	 * If the superblock doesn't start on a sector boundary,
	 * calculate the offset.  FIXME(eric) this doesn't make sense
	 * that we would have to do this.
	 */
	if (blocksize != BLOCK_SIZE) {
		logic_sb_block = (sb_block*BLOCK_SIZE) / blocksize;
		offset = (sb_block*BLOCK_SIZE) % blocksize;
	}

	if (!(bh = sb_bread(sb, logic_sb_block))) {
		printk ("EXT2-fs: unable to read superblock\n");
		return NULL;
	}
	/*
	 * Note: s_es must be initialized as soon as possible because
	 *       some ext2 macro-instructions depend on its value
	 */
	es = (struct ext2_super_block *) (((char *)bh->b_data) + offset);
	sb->u.ext2_sb.s_es = es;
	sb->s_magic = le16_to_cpu(es->s_magic);
	if (sb->s_magic != EXT2_SUPER_MAGIC) {
		if (!silent)
			printk ("VFS: Can't find ext2 filesystem on dev %s.\n",
				bdevname(dev));
		goto failed_mount;
	}
	if (le32_to_cpu(es->s_rev_level) == EXT2_GOOD_OLD_REV &&
	    (EXT2_HAS_COMPAT_FEATURE(sb, ~0U) ||
	     EXT2_HAS_RO_COMPAT_FEATURE(sb, ~0U) ||
	     EXT2_HAS_INCOMPAT_FEATURE(sb, ~0U)))
		printk("EXT2-fs warning: feature flags set on rev 0 fs, "
		       "running e2fsck is recommended\n");
	/*
	 * Check feature flags regardless of the revision level, since we
	 * previously didn't change the revision level when setting the flags,
	 * so there is a chance incompat flags are set on a rev 0 filesystem.
	 */
	if ((i = EXT2_HAS_INCOMPAT_FEATURE(sb, ~EXT2_FEATURE_INCOMPAT_SUPP))) {
		printk("EXT2-fs: %s: couldn't mount because of "
		       "unsupported optional features (%x).\n",
		       bdevname(dev), i);
		goto failed_mount;
	}
	if (!(sb->s_flags & MS_RDONLY) &&
	    (i = EXT2_HAS_RO_COMPAT_FEATURE(sb, ~EXT2_FEATURE_RO_COMPAT_SUPP))){
		printk("EXT2-fs: %s: couldn't mount RDWR because of "
		       "unsupported optional features (%x).\n",
		       bdevname(dev), i);
		goto failed_mount;
	}
	sb->s_blocksize_bits =
		le32_to_cpu(EXT2_SB(sb)->s_es->s_log_block_size) + 10;
	sb->s_blocksize = 1 << sb->s_blocksize_bits;

	sb->s_maxbytes = ext2_max_size(sb->s_blocksize_bits);

	/* If the blocksize doesn't match, re-read the thing.. */
	if (sb->s_blocksize != blocksize) {
		blocksize = sb->s_blocksize;
		brelse(bh);

		if (set_blocksize(dev, blocksize) < 0) {
			printk(KERN_ERR "EXT2-fs: blocksize too small for device.\n");
			return NULL;
		}

		logic_sb_block = (sb_block*BLOCK_SIZE) / blocksize;
		offset = (sb_block*BLOCK_SIZE) % blocksize;
		bh = sb_bread(sb, logic_sb_block);
		if(!bh) {
			printk("EXT2-fs: Couldn't read superblock on "
			       "2nd try.\n");
			goto failed_mount;
		}
		es = (struct ext2_super_block *) (((char *)bh->b_data) + offset);
		sb->u.ext2_sb.s_es = es;
		if (es->s_magic != le16_to_cpu(EXT2_SUPER_MAGIC)) {
			printk ("EXT2-fs: Magic mismatch, very weird !\n");
			goto failed_mount;
		}
	}

	if (le32_to_cpu(es->s_rev_level) == EXT2_GOOD_OLD_REV) {
		sb->u.ext2_sb.s_inode_size = EXT2_GOOD_OLD_INODE_SIZE;
		sb->u.ext2_sb.s_first_ino = EXT2_GOOD_OLD_FIRST_INO;
	} else {
		sb->u.ext2_sb.s_inode_size = le16_to_cpu(es->s_inode_size);
		sb->u.ext2_sb.s_first_ino = le32_to_cpu(es->s_first_ino);
		if (sb->u.ext2_sb.s_inode_size != EXT2_GOOD_OLD_INODE_SIZE) {
			printk ("EXT2-fs: unsupported inode size: %d\n",
				sb->u.ext2_sb.s_inode_size);
			goto failed_mount;
		}
	}
	sb->u.ext2_sb.s_frag_size = EXT2_MIN_FRAG_SIZE <<
				   le32_to_cpu(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 = le32_to_cpu(es->s_blocks_per_group);
	sb->u.ext2_sb.s_frags_per_group = le32_to_cpu(es->s_frags_per_group);
	sb->u.ext2_sb.s_inodes_per_group = le32_to_cpu(es->s_inodes_per_group);
	sb->u.ext2_sb.s_inodes_per_block = sb->s_blocksize /
					   EXT2_INODE_SIZE(sb);
	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;
	if (resuid != EXT2_DEF_RESUID)
		sb->u.ext2_sb.s_resuid = resuid;
	else
		sb->u.ext2_sb.s_resuid = le16_to_cpu(es->s_def_resuid);
	if (resgid != EXT2_DEF_RESGID)
		sb->u.ext2_sb.s_resgid = resgid;
	else
		sb->u.ext2_sb.s_resgid = le16_to_cpu(es->s_def_resgid);
	sb->u.ext2_sb.s_mount_state = le16_to_cpu(es->s_state);
	sb->u.ext2_sb.s_addr_per_block_bits =
		log2 (EXT2_ADDR_PER_BLOCK(sb));
	sb->u.ext2_sb.s_desc_per_block_bits =
		log2 (EXT2_DESC_PER_BLOCK(sb));
	if (sb->s_magic != EXT2_SUPER_MAGIC) {
		if (!silent)
			printk ("VFS: Can't find an ext2 filesystem on dev "
				"%s.\n",
				bdevname(dev));
		goto failed_mount;
	}
	if (sb->s_blocksize != bh->b_size) {
		if (!silent)
			printk ("VFS: Unsupported blocksize on dev "
				"%s.\n", bdevname(dev));
		goto failed_mount;
	}

	if (sb->s_blocksize != sb->u.ext2_sb.s_frag_size) {
		printk ("EXT2-fs: fragsize %lu != blocksize %lu (not supported yet)\n",
			sb->u.ext2_sb.s_frag_size, sb->s_blocksize);
		goto failed_mount;
	}

	if (sb->u.ext2_sb.s_blocks_per_group > sb->s_blocksize * 8) {
		printk ("EXT2-fs: #blocks per group too big: %lu\n",
			sb->u.ext2_sb.s_blocks_per_group);
		goto failed_mount;
	}
	if (sb->u.ext2_sb.s_frags_per_group > sb->s_blocksize * 8) {
		printk ("EXT2-fs: #fragments per group too big: %lu\n",
			sb->u.ext2_sb.s_frags_per_group);
		goto failed_mount;
	}
	if (sb->u.ext2_sb.s_inodes_per_group > sb->s_blocksize * 8) {
		printk ("EXT2-fs: #inodes per group too big: %lu\n",
			sb->u.ext2_sb.s_inodes_per_group);
		goto failed_mount;
	}

	sb->u.ext2_sb.s_groups_count = (le32_to_cpu(es->s_blocks_count) -
				        le32_to_cpu(es->s_first_data_block) +
				       EXT2_BLOCKS_PER_GROUP(sb) - 1) /
				       EXT2_BLOCKS_PER_GROUP(sb);
	db_count = (sb->u.ext2_sb.s_groups_count + EXT2_DESC_PER_BLOCK(sb) - 1) /
		   EXT2_DESC_PER_BLOCK(sb);
	sb->u.ext2_sb.s_group_desc = kmalloc (db_count * sizeof (struct buffer_head *), GFP_KERNEL);
	if (sb->u.ext2_sb.s_group_desc == NULL) {
		printk ("EXT2-fs: not enough memory\n");
		goto failed_mount;
	}
	for (i = 0; i < db_count; i++) {
		sb->u.ext2_sb.s_group_desc[i] = sb_bread(sb, logic_sb_block + i + 1);
		if (!sb->u.ext2_sb.s_group_desc[i]) {
			for (j = 0; j < i; j++)
				brelse (sb->u.ext2_sb.s_group_desc[j]);
			kfree(sb->u.ext2_sb.s_group_desc);
			printk ("EXT2-fs: unable to read group descriptors\n");
			goto failed_mount;
		}
	}
	if (!ext2_check_descriptors (sb)) {
		printk ("EXT2-fs: group descriptors corrupted!\n");
		db_count = i;
		goto failed_mount2;
	}
	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;
	sb->u.ext2_sb.s_gdb_count = db_count;
	/*
	 * set up enough so that it can read an inode
	 */
	sb->s_op = &ext2_sops;
	sb->s_root = d_alloc_root(iget(sb, EXT2_ROOT_INO));
	if (!sb->s_root || !S_ISDIR(sb->s_root->d_inode->i_mode) ||
	    !sb->s_root->d_inode->i_blocks || !sb->s_root->d_inode->i_size) {
		if (sb->s_root) {
			dput(sb->s_root);
			sb->s_root = NULL;
			printk(KERN_ERR "EXT2-fs: corrupt root inode, run e2fsck\n");
		} else
			printk(KERN_ERR "EXT2-fs: get root inode failed\n");
		goto failed_mount2;
	}
	ext2_setup_super (sb, es, sb->s_flags & MS_RDONLY);
	return sb;
failed_mount2:
	for (i = 0; i < db_count; i++)
		brelse(sb->u.ext2_sb.s_group_desc[i]);
	kfree(sb->u.ext2_sb.s_group_desc);
failed_mount:
	brelse(bh);
	return NULL;
}

static void ext2_commit_super (struct super_block * sb,
			       struct ext2_super_block * es)
{
	es->s_wtime = cpu_to_le32(CURRENT_TIME);
	mark_buffer_dirty(sb->u.ext2_sb.s_sbh);
	sb->s_dirt = 0;
}

static void ext2_sync_super(struct super_block *sb, struct ext2_super_block *es)
{
	es->s_wtime = cpu_to_le32(CURRENT_TIME);
	mark_buffer_dirty(EXT2_SB(sb)->s_sbh);
	ll_rw_block(WRITE, 1, &EXT2_SB(sb)->s_sbh);
	wait_on_buffer(EXT2_SB(sb)->s_sbh);
	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;

		if (le16_to_cpu(es->s_state) & EXT2_VALID_FS) {
			ext2_debug ("setting valid to 0\n");
			es->s_state = cpu_to_le16(le16_to_cpu(es->s_state) &
						  ~EXT2_VALID_FS);
			es->s_mtime = cpu_to_le32(CURRENT_TIME);
			ext2_sync_super(sb, es);
		} else
			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 short resuid = sb->u.ext2_sb.s_resuid;
	unsigned short resgid = sb->u.ext2_sb.s_resgid;
	unsigned long new_mount_opt;
	unsigned long tmp;

	/*
	 * Allow the "check" option to be passed as a remount option.
	 */
	new_mount_opt = sb->u.ext2_sb.s_mount_opt;
	if (!parse_options (data, &tmp, &resuid, &resgid,
			    &new_mount_opt))
		return -EINVAL;

	sb->u.ext2_sb.s_mount_opt = new_mount_opt;
	sb->u.ext2_sb.s_resuid = resuid;
	sb->u.ext2_sb.s_resgid = resgid;
	es = sb->u.ext2_sb.s_es;
	if ((*flags & MS_RDONLY) == (sb->s_flags & MS_RDONLY))
		return 0;
	if (*flags & MS_RDONLY) {
		if (le16_to_cpu(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 = cpu_to_le16(sb->u.ext2_sb.s_mount_state);
		es->s_mtime = cpu_to_le32(CURRENT_TIME);
	} else {
		int ret;
		if ((ret = EXT2_HAS_RO_COMPAT_FEATURE(sb,
					       ~EXT2_FEATURE_RO_COMPAT_SUPP))) {
			printk("EXT2-fs: %s: couldn't remount RDWR because of "
			       "unsupported optional features (%x).\n",
			       bdevname(sb->s_dev), ret);
			return -EROFS;
		}
		/*
		 * 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 = le16_to_cpu(es->s_state);
		if (!ext2_setup_super (sb, es, 0))
			sb->s_flags &= ~MS_RDONLY;
	}
	ext2_sync_super(sb, es);
	return 0;
}

int ext2_statfs (struct super_block * sb, struct statfs * buf)
{
	unsigned long overhead;
	int i;

	if (test_opt (sb, MINIX_DF))
		overhead = 0;
	else {
		/*
		 * Compute the overhead (FS structures)
		 */

		/*
		 * All of the blocks before first_data_block are
		 * overhead
		 */
		overhead = le32_to_cpu(sb->u.ext2_sb.s_es->s_first_data_block);

		/*
		 * Add the overhead attributed to the superblock and
		 * block group descriptors.  If the sparse superblocks
		 * feature is turned on, then not all groups have this.
		 */
		for (i = 0; i < EXT2_SB(sb)->s_groups_count; i++)
			overhead += ext2_bg_has_super(sb, i) +
				ext2_bg_num_gdb(sb, i);

		/*
		 * Every block group has an inode bitmap, a block
		 * bitmap, and an inode table.
		 */
		overhead += (sb->u.ext2_sb.s_groups_count *
			     (2 + sb->u.ext2_sb.s_itb_per_group));
	}

	buf->f_type = EXT2_SUPER_MAGIC;
	buf->f_bsize = sb->s_blocksize;
	buf->f_blocks = le32_to_cpu(sb->u.ext2_sb.s_es->s_blocks_count) - overhead;
	buf->f_bfree = ext2_count_free_blocks (sb);
	buf->f_bavail = buf->f_bfree - le32_to_cpu(sb->u.ext2_sb.s_es->s_r_blocks_count);
	if (buf->f_bfree < le32_to_cpu(sb->u.ext2_sb.s_es->s_r_blocks_count))
		buf->f_bavail = 0;
	buf->f_files = le32_to_cpu(sb->u.ext2_sb.s_es->s_inodes_count);
	buf->f_ffree = ext2_count_free_inodes (sb);
	buf->f_namelen = EXT2_NAME_LEN;
	return 0;
}

static DECLARE_FSTYPE_DEV(ext2_fs_type, "ext2", ext2_read_super);

static int __init init_ext2_fs(void)
{
        return register_filesystem(&ext2_fs_type);
}

static void __exit exit_ext2_fs(void)
{
	unregister_filesystem(&ext2_fs_type);
}

EXPORT_NO_SYMBOLS;

module_init(init_ext2_fs)
module_exit(exit_ext2_fs)