C++ sb_min_blocksize函数代码示例

static int squashfs_fill_super(struct super_block *sb, void *data, int silent)
{
	struct squashfs_sb_info *msblk;
	struct squashfs_super_block *sblk = NULL;
	char b[BDEVNAME_SIZE];
	struct inode *root;
	long long root_inode;
	unsigned short flags;
	unsigned int fragments;
	u64 lookup_table_start, xattr_id_table_start, next_table;
	int err;

	TRACE("Entered squashfs_fill_superblock\n");

	sb->s_fs_info = kzalloc(sizeof(*msblk), GFP_KERNEL);
	if (sb->s_fs_info == NULL) {
		ERROR("Failed to allocate squashfs_sb_info\n");
		return -ENOMEM;
	}
	msblk = sb->s_fs_info;

	msblk->devblksize = sb_min_blocksize(sb, SQUASHFS_DEVBLK_SIZE);
	msblk->devblksize_log2 = ffz(~msblk->devblksize);

	mutex_init(&msblk->read_data_mutex);
	mutex_init(&msblk->meta_index_mutex);

	/*
	 * msblk->bytes_used is checked in squashfs_read_table to ensure reads
	 * are not beyond filesystem end.  But as we're using
	 * squashfs_read_table here to read the superblock (including the value
	 * of bytes_used) we need to set it to an initial sensible dummy value
	 */
	msblk->bytes_used = sizeof(*sblk);
	sblk = squashfs_read_table(sb, SQUASHFS_START, sizeof(*sblk));

	if (IS_ERR(sblk)) {
		ERROR("unable to read squashfs_super_block\n");
		err = PTR_ERR(sblk);
		sblk = NULL;
		goto failed_mount;
	}

	err = -EINVAL;

	/* Check it is a SQUASHFS superblock */
	sb->s_magic = le32_to_cpu(sblk->s_magic);
	if (sb->s_magic != SQUASHFS_MAGIC) {
		if (!silent)
			ERROR("Can't find a SQUASHFS superblock on %s\n",
						bdevname(sb->s_bdev, b));
		goto failed_mount;
	}

	/* Check the MAJOR & MINOR versions and lookup compression type */
	msblk->decompressor = supported_squashfs_filesystem(
			le16_to_cpu(sblk->s_major),
			le16_to_cpu(sblk->s_minor),
			le16_to_cpu(sblk->compression));
	if (msblk->decompressor == NULL)
		goto failed_mount;

	/* Check the filesystem does not extend beyond the end of the
	   block device */
	msblk->bytes_used = le64_to_cpu(sblk->bytes_used);
	if (msblk->bytes_used < 0 || msblk->bytes_used >
			i_size_read(sb->s_bdev->bd_inode))
		goto failed_mount;

	/* Check block size for sanity */
	msblk->block_size = le32_to_cpu(sblk->block_size);
	if (msblk->block_size > SQUASHFS_FILE_MAX_SIZE)
		goto failed_mount;

	/*
	 * Check the system page size is not larger than the filesystem
	 * block size (by default 128K).  This is currently not supported.
	 */
	if (PAGE_CACHE_SIZE > msblk->block_size) {
		ERROR("Page size > filesystem block size (%d).  This is "
			"currently not supported!\n", msblk->block_size);
		goto failed_mount;
	}

	msblk->block_log = le16_to_cpu(sblk->block_log);
	if (msblk->block_log > SQUASHFS_FILE_MAX_LOG)
		goto failed_mount;

	/* Check the root inode for sanity */
	root_inode = le64_to_cpu(sblk->root_inode);
	if (SQUASHFS_INODE_OFFSET(root_inode) > SQUASHFS_METADATA_SIZE)
		goto failed_mount;

	msblk->inode_table = le64_to_cpu(sblk->inode_table_start);
	msblk->directory_table = le64_to_cpu(sblk->directory_table_start);
	msblk->inodes = le32_to_cpu(sblk->inodes);
	flags = le16_to_cpu(sblk->flags);

	TRACE("Found valid superblock on %s\n", bdevname(sb->s_bdev, b));
	TRACE("Inodes are %scompressed\n", SQUASHFS_UNCOMPRESSED_INODES(flags)
//.........这里部分代码省略.........

static int ext2_fill_super(struct super_block *sb, void *data, int silent)
{
	struct buffer_head * bh;
	struct ext2_sb_info * sbi;
	struct ext2_super_block * es;
	struct inode *root;
	unsigned long block;
	unsigned long sb_block = get_sb_block(&data);
	unsigned long logic_sb_block;
	unsigned long offset = 0;
	unsigned long def_mount_opts;
	long ret = -EINVAL;
	int blocksize = BLOCK_SIZE;
	int db_count;
	int i, j;
	__le32 features;
	int err;

	sbi = kzalloc(sizeof(*sbi), GFP_KERNEL);
	if (!sbi)
		return -ENOMEM;

	sbi->s_blockgroup_lock =
		kzalloc(sizeof(struct blockgroup_lock), GFP_KERNEL);
	if (!sbi->s_blockgroup_lock) {
		kfree(sbi);
		return -ENOMEM;
	}
	sb->s_fs_info = sbi;
	sbi->s_sb_block = sb_block;

	/*
	 * 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 = sb_min_blocksize(sb, BLOCK_SIZE);
	if (!blocksize) {
		printk ("EXT2-fs: unable to set blocksize\n");
		goto failed_sbi;
	}

	/*
	 * If the superblock doesn't start on a hardware sector boundary,
	 * calculate the offset.  
	 */
	if (blocksize != BLOCK_SIZE) {
		logic_sb_block = (sb_block*BLOCK_SIZE) / blocksize;
		offset = (sb_block*BLOCK_SIZE) % blocksize;
	} else {
		logic_sb_block = sb_block;
	}

	if (!(bh = sb_bread(sb, logic_sb_block))) {
		printk ("EXT2-fs: unable to read superblock\n");
		goto failed_sbi;
	}
	/*
	 * 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);
	sbi->s_es = es;
	sb->s_magic = le16_to_cpu(es->s_magic);

	if (sb->s_magic != EXT2_SUPER_MAGIC)
		goto cantfind_ext2;

	/* Set defaults before we parse the mount options */
	def_mount_opts = le32_to_cpu(es->s_default_mount_opts);
	if (def_mount_opts & EXT2_DEFM_DEBUG)
		set_opt(sbi->s_mount_opt, DEBUG);
	if (def_mount_opts & EXT2_DEFM_BSDGROUPS)
		set_opt(sbi->s_mount_opt, GRPID);
	if (def_mount_opts & EXT2_DEFM_UID16)
		set_opt(sbi->s_mount_opt, NO_UID32);
#ifdef CONFIG_EXT2_FS_XATTR
	if (def_mount_opts & EXT2_DEFM_XATTR_USER)
		set_opt(sbi->s_mount_opt, XATTR_USER);
#endif
#ifdef CONFIG_EXT2_FS_POSIX_ACL
	if (def_mount_opts & EXT2_DEFM_ACL)
		set_opt(sbi->s_mount_opt, POSIX_ACL);
#endif
	
	if (le16_to_cpu(sbi->s_es->s_errors) == EXT2_ERRORS_PANIC)
		set_opt(sbi->s_mount_opt, ERRORS_PANIC);
	else if (le16_to_cpu(sbi->s_es->s_errors) == EXT2_ERRORS_CONTINUE)
		set_opt(sbi->s_mount_opt, ERRORS_CONT);
	else
		set_opt(sbi->s_mount_opt, ERRORS_RO);

	sbi->s_resuid = le16_to_cpu(es->s_def_resuid);
	sbi->s_resgid = le16_to_cpu(es->s_def_resgid);
	
	set_opt(sbi->s_mount_opt, RESERVATION);

	if (!parse_options ((char *) data, sbi))
//.........这里部分代码省略.........

/**
 * vxfs_read_super - read superblock into memory and initialize filesystem
 * @sbp:		VFS superblock (to fill)
 * @dp:			fs private mount data
 * @silent:		do not complain loudly when sth is wrong
 *
 * Description:
 *   We are called on the first mount of a filesystem to read the
 *   superblock into memory and do some basic setup.
 *
 * Returns:
 *   The superblock on success, else %NULL.
 *
 * Locking:
 *   We are under the bkl and @sbp->s_lock.
 */
static int vxfs_fill_super(struct super_block *sbp, void *dp, int silent)
{
	struct vxfs_sb_info	*infp;
	struct vxfs_sb		*rsbp;
	struct buffer_head	*bp = NULL;
	u_long			bsize;
	struct inode *root;
	int ret = -EINVAL;

	sbp->s_flags |= MS_RDONLY;

	infp = kzalloc(sizeof(*infp), GFP_KERNEL);
	if (!infp) {
		printk(KERN_WARNING "vxfs: unable to allocate incore superblock\n");
		return -ENOMEM;
	}

	bsize = sb_min_blocksize(sbp, BLOCK_SIZE);
	if (!bsize) {
		printk(KERN_WARNING "vxfs: unable to set blocksize\n");
		goto out;
	}

	bp = sb_bread(sbp, 1);
	if (!bp || !buffer_mapped(bp)) {
		if (!silent) {
			printk(KERN_WARNING
				"vxfs: unable to read disk superblock\n");
		}
		goto out;
	}

	rsbp = (struct vxfs_sb *)bp->b_data;
	if (rsbp->vs_magic != VXFS_SUPER_MAGIC) {
		if (!silent)
			printk(KERN_NOTICE "vxfs: WRONG superblock magic\n");
		goto out;
	}

	if ((rsbp->vs_version < 2 || rsbp->vs_version > 4) && !silent) {
		printk(KERN_NOTICE "vxfs: unsupported VxFS version (%d)\n",
		       rsbp->vs_version);
		goto out;
	}

#ifdef DIAGNOSTIC
	printk(KERN_DEBUG "vxfs: supported VxFS version (%d)\n", rsbp->vs_version);
	printk(KERN_DEBUG "vxfs: blocksize: %d\n", rsbp->vs_bsize);
#endif

	sbp->s_magic = rsbp->vs_magic;
	sbp->s_fs_info = infp;

	infp->vsi_raw = rsbp;
	infp->vsi_bp = bp;
	infp->vsi_oltext = rsbp->vs_oltext[0];
	infp->vsi_oltsize = rsbp->vs_oltsize;

	if (!sb_set_blocksize(sbp, rsbp->vs_bsize)) {
		printk(KERN_WARNING "vxfs: unable to set final block size\n");
		goto out;
	}

	if (vxfs_read_olt(sbp, bsize)) {
		printk(KERN_WARNING "vxfs: unable to read olt\n");
		goto out;
	}

	if (vxfs_read_fshead(sbp)) {
		printk(KERN_WARNING "vxfs: unable to read fshead\n");
		goto out;
	}

	sbp->s_op = &vxfs_super_ops;
	root = vxfs_iget(sbp, VXFS_ROOT_INO);
	if (IS_ERR(root)) {
		ret = PTR_ERR(root);
		goto out;
	}
	sbp->s_root = d_alloc_root(root);
	if (!sbp->s_root) {
		iput(root);
		printk(KERN_WARNING "vxfs: unable to get root dentry.\n");
		goto out_free_ilist;
//.........这里部分代码省略.........

/* Allocate private field of the superblock, fill it.
 *
 * Finish filling the public superblock fields
 * Make the root directory
 * Load a set of NLS translations if needed.
 */
static int
befs_fill_super(struct super_block *sb, void *data, int silent)
{
	struct buffer_head *bh;
	befs_sb_info *befs_sb;
	befs_super_block *disk_sb;
	struct inode *root;
	long ret = -EINVAL;
	const unsigned long sb_block = 0;
	const off_t x86_sb_off = 512;

	save_mount_options(sb, data);

	sb->s_fs_info = kmalloc(sizeof (*befs_sb), GFP_KERNEL);
	if (sb->s_fs_info == NULL) {
		printk(KERN_ERR
		       "BeFS(%s): Unable to allocate memory for private "
		       "portion of superblock. Bailing.\n", sb->s_id);
		goto unacquire_none;
	}
	befs_sb = BEFS_SB(sb);
	memset(befs_sb, 0, sizeof(befs_sb_info));

	if (!parse_options((char *) data, &befs_sb->mount_opts)) {
		befs_error(sb, "cannot parse mount options");
		goto unacquire_priv_sbp;
	}

	befs_debug(sb, "---> befs_fill_super()");

#ifndef CONFIG_BEFS_RW
	if (!(sb->s_flags & MS_RDONLY)) {
		befs_warning(sb,
			     "No write support. Marking filesystem read-only");
		sb->s_flags |= MS_RDONLY;
	}
#endif				/* CONFIG_BEFS_RW */

	/*
	 * Set dummy blocksize to read super block.
	 * Will be set to real fs blocksize later.
	 *
	 * Linux 2.4.10 and later refuse to read blocks smaller than
	 * the hardsect size for the device. But we also need to read at 
	 * least 1k to get the second 512 bytes of the volume.
	 * -WD 10-26-01
	 */ 
	sb_min_blocksize(sb, 1024);

	if (!(bh = sb_bread(sb, sb_block))) {
		befs_error(sb, "unable to read superblock");
		goto unacquire_priv_sbp;
	}

	/* account for offset of super block on x86 */
	disk_sb = (befs_super_block *) bh->b_data;
	if ((disk_sb->magic1 == BEFS_SUPER_MAGIC1_LE) ||
	    (disk_sb->magic1 == BEFS_SUPER_MAGIC1_BE)) {
		befs_debug(sb, "Using PPC superblock location");
	} else {
		befs_debug(sb, "Using x86 superblock location");
		disk_sb =
		    (befs_super_block *) ((void *) bh->b_data + x86_sb_off);
	}

	if (befs_load_sb(sb, disk_sb) != BEFS_OK)
		goto unacquire_bh;

	befs_dump_super_block(sb, disk_sb);

	brelse(bh);

	if (befs_check_sb(sb) != BEFS_OK)
		goto unacquire_priv_sbp;

	if( befs_sb->num_blocks > ~((sector_t)0) ) {
		befs_error(sb, "blocks count: %Lu "
			"is larger than the host can use",
			befs_sb->num_blocks);
		goto unacquire_priv_sbp;
	}

	/*
	 * set up enough so that it can read an inode
	 * Fill in kernel superblock fields from private sb
	 */
	sb->s_magic = BEFS_SUPER_MAGIC;
	/* Set real blocksize of fs */
	sb_set_blocksize(sb, (ulong) befs_sb->block_size);
	sb->s_op = &befs_sops;
	root = befs_iget(sb, iaddr2blockno(sb, &(befs_sb->root_dir)));
	if (IS_ERR(root)) {
		ret = PTR_ERR(root);
		goto unacquire_priv_sbp;
//.........这里部分代码省略.........

/* Takes in super block, returns true if good data read */
int hfsplus_read_wrapper(struct super_block *sb)
{
    struct hfsplus_sb_info *sbi = HFSPLUS_SB(sb);
    struct hfsplus_wd wd;
    sector_t part_start, part_size;
    u32 blocksize;
    int error = 0;

    error = -EINVAL;
    blocksize = sb_min_blocksize(sb, HFSPLUS_SECTOR_SIZE);
    if (!blocksize)
        goto out;

    if (hfsplus_get_last_session(sb, &part_start, &part_size))
        goto out;

    error = -ENOMEM;
    sbi->s_vhdr_buf = kmalloc(hfsplus_min_io_size(sb), GFP_KERNEL);
    if (!sbi->s_vhdr_buf)
        goto out;
    sbi->s_backup_vhdr_buf = kmalloc(hfsplus_min_io_size(sb), GFP_KERNEL);
    if (!sbi->s_backup_vhdr_buf)
        goto out_free_vhdr;

reread:
    error = hfsplus_submit_bio(sb, part_start + HFSPLUS_VOLHEAD_SECTOR,
                               sbi->s_vhdr_buf, (void **)&sbi->s_vhdr,
                               READ);
    if (error)
        goto out_free_backup_vhdr;

    error = -EINVAL;
    switch (sbi->s_vhdr->signature) {
    case cpu_to_be16(HFSPLUS_VOLHEAD_SIGX):
        set_bit(HFSPLUS_SB_HFSX, &sbi->flags);
    /*FALLTHRU*/
    case cpu_to_be16(HFSPLUS_VOLHEAD_SIG):
        break;
    case cpu_to_be16(HFSP_WRAP_MAGIC):
        if (!hfsplus_read_mdb(sbi->s_vhdr, &wd))
            goto out_free_backup_vhdr;
        wd.ablk_size >>= HFSPLUS_SECTOR_SHIFT;
        part_start += (sector_t)wd.ablk_start +
                      (sector_t)wd.embed_start * wd.ablk_size;
        part_size = (sector_t)wd.embed_count * wd.ablk_size;
        goto reread;
    default:
        /*
         * Check for a partition block.
         *
         * (should do this only for cdrom/loop though)
         */
        if (hfs_part_find(sb, &part_start, &part_size))
            goto out_free_backup_vhdr;
        goto reread;
    }

    error = hfsplus_submit_bio(sb, part_start + part_size - 2,
                               sbi->s_backup_vhdr_buf,
                               (void **)&sbi->s_backup_vhdr, READ);
    if (error)
        goto out_free_backup_vhdr;

    error = -EINVAL;
    if (sbi->s_backup_vhdr->signature != sbi->s_vhdr->signature) {
        pr_warn("invalid secondary volume header\n");
        goto out_free_backup_vhdr;
    }

    blocksize = be32_to_cpu(sbi->s_vhdr->blocksize);

    /*
     * Block size must be at least as large as a sector and a multiple of 2.
     */
    if (blocksize < HFSPLUS_SECTOR_SIZE || ((blocksize - 1) & blocksize))
        goto out_free_backup_vhdr;
    sbi->alloc_blksz = blocksize;
    sbi->alloc_blksz_shift = 0;
    while ((blocksize >>= 1) != 0)
        sbi->alloc_blksz_shift++;
    blocksize = min(sbi->alloc_blksz, (u32)PAGE_SIZE);

    /*
     * Align block size to block offset.
     */
    while (part_start & ((blocksize >> HFSPLUS_SECTOR_SHIFT) - 1))
        blocksize >>= 1;

    if (sb_set_blocksize(sb, blocksize) != blocksize) {
        pr_err("unable to set blocksize to %u!\n", blocksize);
        goto out_free_backup_vhdr;
    }

    sbi->blockoffset =
        part_start >> (sb->s_blocksize_bits - HFSPLUS_SECTOR_SHIFT);
    sbi->part_start = part_start;
    sbi->sect_count = part_size;
    sbi->fs_shift = sbi->alloc_blksz_shift - sb->s_blocksize_bits;
    return 0;
//.........这里部分代码省略.........

/*
 * hfs_mdb_get()
 *
 * Build the in-core MDB for a filesystem, including
 * the B-trees and the volume bitmap.
 */
int hfs_mdb_get(struct super_block *sb)
{
	struct buffer_head *bh;
	struct hfs_mdb *mdb, *mdb2;
	unsigned int block;
	char *ptr;
	int off2, len, size, sect;
	sector_t part_start, part_size;
	loff_t off;
	__be16 attrib;

	/* set the device driver to 512-byte blocks */
	size = sb_min_blocksize(sb, HFS_SECTOR_SIZE);
	if (!size)
		return -EINVAL;

	if (hfs_get_last_session(sb, &part_start, &part_size))
		return -EINVAL;
	while (1) {
		/* See if this is an HFS filesystem */
		bh = sb_bread512(sb, part_start + HFS_MDB_BLK, mdb);
		if (!bh)
			goto out;

		if (mdb->drSigWord == cpu_to_be16(HFS_SUPER_MAGIC))
			break;
		brelse(bh);

		/* check for a partition block
		 * (should do this only for cdrom/loop though)
		 */
		if (hfs_part_find(sb, &part_start, &part_size))
			goto out;
	}

	HFS_SB(sb)->alloc_blksz = size = be32_to_cpu(mdb->drAlBlkSiz);
	if (!size || (size & (HFS_SECTOR_SIZE - 1))) {
		hfs_warn("hfs_fs: bad allocation block size %d\n", size);
		goto out_bh;
	}

	size = min(HFS_SB(sb)->alloc_blksz, (u32)PAGE_SIZE);
	/* size must be a multiple of 512 */
	while (size & (size - 1))
		size -= HFS_SECTOR_SIZE;
	sect = be16_to_cpu(mdb->drAlBlSt) + part_start;
	/* align block size to first sector */
	while (sect & ((size - 1) >> HFS_SECTOR_SIZE_BITS))
		size >>= 1;
	/* align block size to weird alloc size */
	while (HFS_SB(sb)->alloc_blksz & (size - 1))
		size >>= 1;
	brelse(bh);
	if (!sb_set_blocksize(sb, size)) {
		printk("hfs_fs: unable to set blocksize to %u\n", size);
		goto out;
	}

	bh = sb_bread512(sb, part_start + HFS_MDB_BLK, mdb);
	if (!bh)
		goto out;
	if (mdb->drSigWord != cpu_to_be16(HFS_SUPER_MAGIC))
		goto out_bh;

	HFS_SB(sb)->mdb_bh = bh;
	HFS_SB(sb)->mdb = mdb;

	/* These parameters are read from the MDB, and never written */
	HFS_SB(sb)->part_start = part_start;
	HFS_SB(sb)->fs_ablocks = be16_to_cpu(mdb->drNmAlBlks);
	HFS_SB(sb)->fs_div = HFS_SB(sb)->alloc_blksz >> sb->s_blocksize_bits;
	HFS_SB(sb)->clumpablks = be32_to_cpu(mdb->drClpSiz) /
				 HFS_SB(sb)->alloc_blksz;
	if (!HFS_SB(sb)->clumpablks)
		HFS_SB(sb)->clumpablks = 1;
	HFS_SB(sb)->fs_start = (be16_to_cpu(mdb->drAlBlSt) + part_start) >>
			       (sb->s_blocksize_bits - HFS_SECTOR_SIZE_BITS);

	/* These parameters are read from and written to the MDB */
	HFS_SB(sb)->free_ablocks = be16_to_cpu(mdb->drFreeBks);
	HFS_SB(sb)->next_id = be32_to_cpu(mdb->drNxtCNID);
	HFS_SB(sb)->root_files = be16_to_cpu(mdb->drNmFls);
	HFS_SB(sb)->root_dirs = be16_to_cpu(mdb->drNmRtDirs);
	HFS_SB(sb)->file_count = be32_to_cpu(mdb->drFilCnt);
	HFS_SB(sb)->folder_count = be32_to_cpu(mdb->drDirCnt);

	/* TRY to get the alternate (backup) MDB. */
	sect = part_start + part_size - 2;
	bh = sb_bread512(sb, sect, mdb2);
	if (bh) {
		if (mdb2->drSigWord == cpu_to_be16(HFS_SUPER_MAGIC)) {
			HFS_SB(sb)->alt_mdb_bh = bh;
			HFS_SB(sb)->alt_mdb = mdb2;
		} else
//.........这里部分代码省略.........

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 short resuid = EXT2_DEF_RESUID;
	unsigned short resgid = EXT2_DEF_RESGID;
	unsigned long logic_sb_block = 1;
	unsigned long offset = 0;
	int blocksize = BLOCK_SIZE;
	int db_count;
	int i, j;

	/*
	 * 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.
	 */

	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;
	}

	blocksize = sb_min_blocksize(sb, BLOCK_SIZE);
	if (!blocksize) {
		printk ("EXT2-fs: unable to set blocksize\n");
		return NULL;
	}

	/*
	 * 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",
				sb->s_id);
		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",
		       sb->s_id, 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",
		       sb->s_id, i);
		goto failed_mount;
	}
	blocksize = BLOCK_SIZE << le32_to_cpu(EXT2_SB(sb)->s_es->s_log_block_size);
	/* If the blocksize doesn't match, re-read the thing.. */
	if (sb->s_blocksize != blocksize) {
		brelse(bh);

		if (!sb_set_blocksize(sb, blocksize)) {
			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 "
//.........这里部分代码省略.........

/*
==================================================================================
	Function	:me2fsFillSuperBlock
	Input		:struct super_block *sb
				 < vfs super block object >
				 void *data
				 < user data >
				 int silent
				 < silent flag >
	Output		:void
	Return		:void

	Description	:fill my ext2 super block object
==================================================================================
*/
static int me2fsFillSuperBlock( struct super_block *sb,
								void *data,
								int silent )
{
	struct buffer_head		*bh;
	struct ext2_super_block	*esb;
	struct me2fs_sb_info	*msi;
	struct inode			*root;
	int						block_size;
	int						ret = -EINVAL;
	int						i;
	int						err;
	unsigned long			sb_block = 1;

	/* ------------------------------------------------------------------------ */
	/* allocate memory to me2fs_sb_info											*/
	/* ------------------------------------------------------------------------ */
	msi = kzalloc( sizeof( struct me2fs_sb_info ), GFP_KERNEL );

	if( !msi )
	{
		ME2FS_ERROR( "<ME2FS>error: unable to alloc me2fs_sb_info\n" );
		ret = -ENOMEM;
		return( ret );
	}

	/* set me2fs information to vfs super block									*/
	sb->s_fs_info	= ( void* )msi;

	/* ------------------------------------------------------------------------ */
	/* allocate memory to spin locks for block group							*/
	/* ------------------------------------------------------------------------ */
	msi->s_blockgroup_lock = kzalloc( sizeof( struct blockgroup_lock ),
									  GFP_KERNEL );
	if( !msi->s_blockgroup_lock )
	{
		ME2FS_ERROR( "<ME2FS>error: unabel to alloc s_blockgroup_lock\n" );
		kfree( msi );
		return( -ENOMEM );
	}

	/* ------------------------------------------------------------------------ */
	/* set device's block size and size bits to super block						*/
	/* ------------------------------------------------------------------------ */
	block_size = sb_min_blocksize( sb, BLOCK_SIZE );

	DBGPRINT( "<ME2FS>Fill Super! block_size = %d\n", block_size );
	DBGPRINT( "<ME2FS>s_blocksize_bits = %d\n", sb->s_blocksize_bits );
	DBGPRINT( "<ME2FS>default block size is : %d\n", BLOCK_SIZE );

	if( !block_size )
	{
		ME2FS_ERROR( "<ME2FS>error: unable to set blocksize\n" );
		goto error_read_sb;
	}

	/* ------------------------------------------------------------------------ */
	/* read super block															*/
	/* ------------------------------------------------------------------------ */
	if( !( bh = sb_bread( sb, sb_block ) ) )
	{
		ME2FS_ERROR( "<ME2FS>failed to bread super block\n" );
		goto error_read_sb;
	}

	esb = ( struct ext2_super_block* )( bh->b_data );

	/* ------------------------------------------------------------------------ */
	/* check magic number														*/
	/* ------------------------------------------------------------------------ */
	sb->s_magic = le16_to_cpu( esb->s_magic );

	if( sb->s_magic != ME2FS_SUPER_MAGIC )
	{
		ME2FS_ERROR( "<ME2FS>error : magic of super block is %lu\n", sb->s_magic );
		goto error_mount;
	}

	/* ------------------------------------------------------------------------ */
	/* check revison															*/
	/* ------------------------------------------------------------------------ */
	if( ME2FS_OLD_REV == le32_to_cpu( esb->s_rev_level ) )
	{
		ME2FS_ERROR( "<ME2FS>error : cannot mount old revision\n" );
		goto error_mount;
//.........这里部分代码省略.........

/* Called to mount a filesystem by read_super() in fs/super.c.
 * Return a super block, the main structure of a filesystem.
 *
 * NOTE : Don't store a pointer to an option, as the page containing the
 * options is freed after ntfs_read_super() returns.
 *
 * NOTE : A context switch can happen in kernel code only if the code blocks
 * (= calls schedule() in kernel/sched.c). */
struct super_block *ntfs_read_super(struct super_block *sb, void *options,
		int silent)
{
	ntfs_volume *vol;
	struct buffer_head *bh;
	int i, to_read, blocksize;

	ntfs_debug(DEBUG_OTHER, "ntfs_read_super\n");
	vol = NTFS_SB2VOL(sb);
	init_ntfs_super_block(vol);
	if (!parse_options(vol, (char*)options))
		goto ntfs_read_super_vol;
	blocksize = sb_min_blocksize(sb, 512);
	if (!blocksize) {
		ntfs_error("Unable to set blocksize.\n");
		goto ntfs_read_super_vol;
	}
	/* Read the super block (boot block). */
	if (!(bh = sb_bread(sb, 0))) {
		ntfs_error("Reading super block failed\n");
		goto ntfs_read_super_unl;
	}
	ntfs_debug(DEBUG_OTHER, "Done reading boot block\n");
	/* Check for valid 'NTFS' boot sector. */
	if (!is_boot_sector_ntfs(bh->b_data)) {
		ntfs_debug(DEBUG_OTHER, "Not a NTFS volume\n");
		bforget(bh);
		goto ntfs_read_super_unl;
	}
	ntfs_debug(DEBUG_OTHER, "Going to init volume\n");
	if (ntfs_init_volume(vol, bh->b_data) < 0) {
		ntfs_debug(DEBUG_OTHER, "Init volume failed.\n");
		bforget(bh);
		goto ntfs_read_super_unl;
	}
	ntfs_debug(DEBUG_OTHER, "$Mft at cluster 0x%lx\n", vol->mft_lcn);
	brelse(bh);
	NTFS_SB(vol) = sb;
	if (vol->cluster_size > PAGE_SIZE) {
		ntfs_error("Partition cluster size is not supported yet (it "
			   "is > max kernel blocksize).\n");
		goto ntfs_read_super_unl;
	}
	ntfs_debug(DEBUG_OTHER, "Done to init volume\n");
	/* Inform the kernel that a device block is a NTFS cluster. */
	if (!sb_set_blocksize(sb, vol->cluster_size)) {
		ntfs_error("Cluster size too small for device.\n");
		goto ntfs_read_super_unl;
	}
	ntfs_debug(DEBUG_OTHER, "set_blocksize\n");
	/* Allocate an MFT record (MFT record can be smaller than a cluster). */
	i = vol->cluster_size;
	if (i < vol->mft_record_size)
		i = vol->mft_record_size;
	if (!(vol->mft = ntfs_malloc(i)))
		goto ntfs_read_super_unl;

	/* Read at least the MFT record for $Mft. */
	to_read = vol->mft_clusters_per_record;
	if (to_read < 1)
		to_read = 1;
	for (i = 0; i < to_read; i++) {
		if (!(bh = sb_bread(sb, vol->mft_lcn + i))) {
			ntfs_error("Could not read $Mft record 0\n");
			goto ntfs_read_super_mft;
		}
		ntfs_memcpy(vol->mft + ((__s64)i << vol->cluster_size_bits),
						bh->b_data, vol->cluster_size);
		brelse(bh);
		ntfs_debug(DEBUG_OTHER, "Read cluster 0x%x\n",
							 vol->mft_lcn + i);
	}
	/* Check and fixup this MFT record */
	if (!ntfs_check_mft_record(vol, vol->mft)){
		ntfs_error("Invalid $Mft record 0\n");
		goto ntfs_read_super_mft;
	}
	/* Inform the kernel about which super operations are available. */
	sb->s_op = &ntfs_super_operations;
	sb->s_magic = NTFS_SUPER_MAGIC;
	sb->s_maxbytes = ~0ULL >> 1;
	ntfs_debug(DEBUG_OTHER, "Reading special files\n");
	if (ntfs_load_special_files(vol)) {
		ntfs_error("Error loading special files\n");
		goto ntfs_read_super_mft;
	}
	ntfs_debug(DEBUG_OTHER, "Getting RootDir\n");
	/* Get the root directory. */
	if (!(sb->s_root = d_alloc_root(iget(sb, FILE_root)))) {
		ntfs_error("Could not get root dir inode\n");
		goto ntfs_read_super_mft;
	}
//.........这里部分代码省略.........

static int tux3_fill_super(struct super_block *sb, void *data, int silent)
{
	static struct tux_iattr iattr;
	struct sb *sbi;
	struct root iroot;
	int err, blocksize;

	sbi = kzalloc(sizeof(struct sb), GFP_KERNEL);
	if (!sbi)
		return -ENOMEM;
	sbi->vfs_sb = sb;
	sb->s_fs_info = sbi;
	sb->s_maxbytes = MAX_LFS_FILESIZE;
	sb->s_magic = 0x54555833;
	sb->s_op = &tux3_super_ops;
	sb->s_time_gran = 1;

	mutex_init(&sbi->loglock);

	err = -EIO;
	blocksize = sb_min_blocksize(sb, BLOCK_SIZE);
	if (!blocksize) {
		if (!silent)
			printk(KERN_ERR "TUX3: unable to set blocksize\n");
		goto error;
	}

	err = tux_load_sb(sb, &iroot, silent);
	if (err)
		goto error;
	printk("%s: depth %Lu, block %Lu\n",
	       __func__, (L)iroot.depth, (L)iroot.block);
	printk("%s: blocksize %u, blockbits %u, blockmask %08x\n",
	       __func__, sbi->blocksize, sbi->blockbits, sbi->blockmask);
	printk("%s: volblocks %Lu, freeblocks %Lu, nextalloc %Lu\n",
	       __func__, sbi->volblocks, sbi->freeblocks, sbi->nextalloc);
	printk("%s: freeatom %u, atomgen %u\n",
	       __func__, sbi->freeatom, sbi->atomgen);

	if (sbi->blocksize != blocksize) {
		if (!sb_set_blocksize(sb, sbi->blocksize)) {
			printk(KERN_ERR "TUX3: blocksize too small for device.\n");
			goto error;
		}
	}
	printk("%s: s_blocksize %lu\n", __func__, sb->s_blocksize);

	err = -ENOMEM;
	sbi->volmap = tux_new_volmap(tux_sb(sb));
	if (!sbi->volmap)
		goto error;

	/* Initialize itable btree */
	init_btree(itable_btree(sbi), sbi, iroot, &itable_ops);

//	struct inode *vtable;
	sbi->bitmap = tux3_iget(sb, TUX_BITMAP_INO);
	err = PTR_ERR(sbi->bitmap);
	if (IS_ERR(sbi->bitmap))
		goto error_bitmap;

	sbi->rootdir = tux3_iget(sb, TUX_ROOTDIR_INO);
	err = PTR_ERR(sbi->rootdir);
	if (IS_ERR(sbi->rootdir))
		goto error_rootdir;

	sbi->atable = tux3_iget(sb, TUX_ATABLE_INO);
	err = PTR_ERR(sbi->atable);
	if (IS_ERR(sbi->atable))
		goto error_atable;

	err = -ENOMEM;
	sbi->logmap = tux_new_inode(sbi->rootdir, &iattr, 0);
	if (!sbi->logmap)
		goto error_logmap;

	sb->s_root = d_alloc_root(sbi->rootdir);
	if (!sb->s_root)
		goto error_alloc_root;

	return 0;

error_alloc_root:
	iput(sbi->logmap);
error_logmap:
	iput(sbi->atable);
error_atable:
	iput(sbi->rootdir);
error_rootdir:
	iput(sbi->bitmap);
error_bitmap:
	iput(sbi->volmap);
error:
	kfree(sbi);
	return err;
}

static int ext2_fill_super(struct super_block *sb, void *data, int silent)
{
	struct buffer_head * bh;
	struct ext2_sb_info * sbi;
	struct ext2_super_block * es;
	struct inode *root;
	unsigned long block;
	unsigned long sb_block = get_sb_block(&data);
	unsigned long logic_sb_block;
	unsigned long offset = 0;
	unsigned long def_mount_opts;
	long ret = -EINVAL;
	int blocksize = BLOCK_SIZE;
	int db_count;
	int i, j;
	__le32 features;
	int err;

	err = -ENOMEM;
	sbi = kzalloc(sizeof(*sbi), GFP_KERNEL);
	if (!sbi)
		goto failed;

	sbi->s_blockgroup_lock =
		kzalloc(sizeof(struct blockgroup_lock), GFP_KERNEL);
	if (!sbi->s_blockgroup_lock) {
		kfree(sbi);
		goto failed;
	}
	sb->s_fs_info = sbi;
	sbi->s_sb_block = sb_block;

	spin_lock_init(&sbi->s_lock);

	/*
	 * 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 = sb_min_blocksize(sb, BLOCK_SIZE);
	if (!blocksize) {
		ext2_msg(sb, KERN_ERR, "error: unable to set blocksize");
		goto failed_sbi;
	}

	/*
	 * If the superblock doesn't start on a hardware sector boundary,
	 * calculate the offset.  
	 */
	if (blocksize != BLOCK_SIZE) {
		logic_sb_block = (sb_block*BLOCK_SIZE) / blocksize;
		offset = (sb_block*BLOCK_SIZE) % blocksize;
	} else {
		logic_sb_block = sb_block;
	}

	if (!(bh = sb_bread(sb, logic_sb_block))) {
		ext2_msg(sb, KERN_ERR, "error: unable to read superblock");
		goto failed_sbi;
	}
	/*
	 * 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);
	sbi->s_es = es;
	sb->s_magic = le16_to_cpu(es->s_magic);

	if (sb->s_magic != EXT2_SUPER_MAGIC)
		goto cantfind_ext2;

	/* Set defaults before we parse the mount options */
	def_mount_opts = le32_to_cpu(es->s_default_mount_opts);
	if (def_mount_opts & EXT2_DEFM_DEBUG)
		set_opt(sbi->s_mount_opt, DEBUG);
	if (def_mount_opts & EXT2_DEFM_BSDGROUPS)
		set_opt(sbi->s_mount_opt, GRPID);
	if (def_mount_opts & EXT2_DEFM_UID16)
		set_opt(sbi->s_mount_opt, NO_UID32);
#ifdef CONFIG_EXT2_FS_XATTR
	if (def_mount_opts & EXT2_DEFM_XATTR_USER)
		set_opt(sbi->s_mount_opt, XATTR_USER);
#endif
#ifdef CONFIG_EXT2_FS_POSIX_ACL
	if (def_mount_opts & EXT2_DEFM_ACL)
		set_opt(sbi->s_mount_opt, POSIX_ACL);
#endif
	
	if (le16_to_cpu(sbi->s_es->s_errors) == EXT2_ERRORS_PANIC)
		set_opt(sbi->s_mount_opt, ERRORS_PANIC);
	else if (le16_to_cpu(sbi->s_es->s_errors) == EXT2_ERRORS_CONTINUE)
		set_opt(sbi->s_mount_opt, ERRORS_CONT);
	else
		set_opt(sbi->s_mount_opt, ERRORS_RO);

	sbi->s_resuid = make_kuid(&init_user_ns, le16_to_cpu(es->s_def_resuid));
	sbi->s_resgid = make_kgid(&init_user_ns, le16_to_cpu(es->s_def_resgid));
	
//.........这里部分代码省略.........

STATIC int
linvfs_fill_super(
	struct super_block	*sb,
	void			*data,
	int			silent)
{
	vnode_t			*rootvp;
	struct vfs		*vfsp = vfs_allocate();
	struct xfs_mount_args	*args = xfs_args_allocate(sb);
	struct kstatfs		statvfs;
	int			error;

	vfsp->vfs_super = sb;
	LINVFS_SET_VFS(sb, vfsp);
	if (sb->s_flags & MS_RDONLY)
		vfsp->vfs_flag |= VFS_RDONLY;
	bhv_insert_all_vfsops(vfsp);

	VFS_PARSEARGS(vfsp, (char *)data, args, 0, error);
	if (error) {
		bhv_remove_all_vfsops(vfsp, 1);
		goto fail_vfsop;
	}

	sb_min_blocksize(sb, BBSIZE);
	sb->s_export_op = &linvfs_export_ops;
	sb->s_qcop = &linvfs_qops;
	sb->s_op = &linvfs_sops;

	VFS_MOUNT(vfsp, args, NULL, error);
	if (error) {
		bhv_remove_all_vfsops(vfsp, 1);
		goto fail_vfsop;
	}

	VFS_STATVFS(vfsp, &statvfs, NULL, error);
	if (error)
		goto fail_unmount;

	sb->s_dirt = 1;
	sb->s_magic = statvfs.f_type;
	sb->s_blocksize = statvfs.f_bsize;
	sb->s_blocksize_bits = ffs(statvfs.f_bsize) - 1;
	sb->s_maxbytes = xfs_max_file_offset(sb->s_blocksize_bits);
	set_posix_acl_flag(sb);

	VFS_ROOT(vfsp, &rootvp, error);
	if (error)
		goto fail_unmount;

	sb->s_root = d_alloc_root(LINVFS_GET_IP(rootvp));
	if (!sb->s_root)
		goto fail_vnrele;
	if (is_bad_inode(sb->s_root->d_inode))
		goto fail_vnrele;
	if (linvfs_start_syncd(vfsp))
		goto fail_vnrele;
	vn_trace_exit(rootvp, __FUNCTION__, (inst_t *)__return_address);

	kmem_free(args, sizeof(*args));
	return 0;

fail_vnrele:
	if (sb->s_root) {
		dput(sb->s_root);
		sb->s_root = NULL;
	} else {
		VN_RELE(rootvp);
	}

fail_unmount:
	VFS_UNMOUNT(vfsp, 0, NULL, error);

fail_vfsop:
	vfs_deallocate(vfsp);
	kmem_free(args, sizeof(*args));
	return -error;
}

static int tux3_fill_super(struct super_block *sb, void *data, int silent)
{
	struct sb *sbi;
	int err, blocksize;

	sbi = kzalloc(sizeof(struct sb), GFP_KERNEL);
	if (!sbi)
		return -ENOMEM;
	sbi->vfs_sb = sb;
	sb->s_fs_info = sbi;
	sb->s_maxbytes = MAX_LFS_FILESIZE;
	sb->s_magic = TUX3_SUPER_MAGIC;
	sb->s_op = &tux3_super_ops;
	sb->s_time_gran = 1;

	mutex_init(&sbi->loglock);
	INIT_LIST_HEAD(&sbi->alloc_inodes);

	err = -EIO;
	blocksize = sb_min_blocksize(sb, BLOCK_SIZE);
	if (!blocksize) {
		if (!silent)
			printk(KERN_ERR "TUX3: unable to set blocksize\n");
		goto error;
	}

	if ((err = load_sb(tux_sb(sb)))) {
		if (!silent) {
			if (err == -EINVAL)
				warn("invalid superblock [%Lx]",
					(L)from_be_u64(*(be_u64 *)sbi->super.magic));
			else
				warn("Unable to read superblock");
		}
		goto error;
	}

	if (sbi->blocksize != blocksize) {
		if (!sb_set_blocksize(sb, sbi->blocksize)) {
			printk(KERN_ERR "TUX3: blocksize too small for device.\n");
			goto error;
		}
	}
	warn("s_blocksize %lu", sb->s_blocksize);

	err = -ENOMEM;
	sbi->volmap = tux_new_volmap(tux_sb(sb));
	if (!sbi->volmap)
		goto error;
	insert_inode_hash(sbi->volmap);

	sbi->logmap = tux_new_logmap(tux_sb(sb));
	if (!sbi->logmap)
		goto error_logmap;

	err = load_itable(sbi);
	if (err)
		goto error_bitmap;

//	struct inode *vtable;
	sbi->bitmap = tux3_iget(sb, TUX_BITMAP_INO);
	err = PTR_ERR(sbi->bitmap);
	if (IS_ERR(sbi->bitmap))
		goto error_bitmap;

	sbi->rootdir = tux3_iget(sb, TUX_ROOTDIR_INO);
	err = PTR_ERR(sbi->rootdir);
	if (IS_ERR(sbi->rootdir))
		goto error_rootdir;

	sbi->atable = tux3_iget(sb, TUX_ATABLE_INO);
	err = PTR_ERR(sbi->atable);
	if (IS_ERR(sbi->atable))
		goto error_atable;

	sb->s_root = d_alloc_root(sbi->rootdir);
	if (!sb->s_root)
		goto error_alloc_root;

	return 0;

error_alloc_root:
	iput(sbi->atable);
error_atable:
	iput(sbi->rootdir);
error_rootdir:
	iput(sbi->bitmap);
error_bitmap:
	iput(sbi->logmap);
error_logmap:
	iput(sbi->volmap);
error:
	kfree(sbi);
	return err;
}

static int lab4fs_fill_super(struct super_block * sb, void * data, int silent)
{
    struct buffer_head * bh;
    int blocksize = BLOCK_SIZE;
    unsigned long logic_sb_block;
    unsigned offset = 0;
    unsigned long sb_block = 1;
    struct lab4fs_super_block *es;
    struct lab4fs_sb_info *sbi;
    struct inode *root;
    int hblock;
    int err = 0;

    sbi = kmalloc(sizeof(*sbi), GFP_KERNEL);
    if (!sbi)
        return -ENOMEM;

    sb->s_fs_info = sbi;
    memset(sbi, 0, sizeof(*sbi));
    blocksize = sb_min_blocksize(sb, BLOCK_SIZE);
    if (!blocksize) {
        LAB4ERROR("unable to set blocksize\n");
        err = -EIO;
        goto out_fail;
    }

    /*
     * If the superblock doesn't start on a hardware sector boundary,
     * calculate the offset.  
     */
    if (blocksize != BLOCK_SIZE) {
        logic_sb_block = (sb_block * BLOCK_SIZE) / blocksize;
        offset = (sb_block * BLOCK_SIZE) % blocksize;
    } else {
        logic_sb_block = sb_block;
    }

    if (!(bh = sb_bread(sb, logic_sb_block))) {
        LAB4ERROR("unable to read super block\n");
        goto out_fail;
    }

    es = (struct lab4fs_super_block *) (((char *)bh->b_data) + offset);
    sb->s_magic = le32_to_cpu(es->s_magic);
    if (sb->s_magic != LAB4FS_SUPER_MAGIC) {
        if (!silent)
            LAB4ERROR("VFS: Can't find lab4fs filesystem on dev %s.\n",
                    sb->s_id);
        goto failed_mount;
    }

    sbi->s_sb = es;
    blocksize = le32_to_cpu(es->s_block_size);
    hblock = bdev_hardsect_size(sb->s_bdev);
    if (sb->s_blocksize != blocksize) {
        /*
         * Make sure the blocksize for the filesystem is larger
         * than the hardware sectorsize for the machine.
         */
        if (blocksize < hblock) {
            LAB4ERROR("blocksize %d too small for "
                    "device blocksize %d.\n", blocksize, hblock);
            goto failed_mount;
        }

        brelse (bh);
        sb_set_blocksize(sb, blocksize);
        logic_sb_block = (sb_block * BLOCK_SIZE) / blocksize;
        offset = (sb_block * BLOCK_SIZE) % blocksize;
        bh = sb_bread(sb, logic_sb_block);
        if (!bh) {
            LAB4ERROR("Can't read superblock on 2nd try.\n");
            goto failed_mount;
        }
        es = (struct lab4fs_super_block *)(((char *)bh->b_data) + offset);
        sbi->s_sb = es;
        if (es->s_magic != cpu_to_le32(LAB4FS_SUPER_MAGIC)) {
            LAB4ERROR("Magic mismatch, very weird !\n");
            goto failed_mount;
        }
    }
    sb->s_maxbytes = lab4fs_max_size(es);
    sbi->s_sbh = bh;
    sbi->s_log_block_size = log2(sb->s_blocksize);
    sbi->s_first_ino = le32_to_cpu(es->s_first_inode);
    sbi->s_inode_size = le32_to_cpu(es->s_inode_size);
    sbi->s_log_inode_size = log2(sbi->s_inode_size);
    sbi->s_inode_table = le32_to_cpu(es->s_inode_table);
    sbi->s_data_blocks = le32_to_cpu(es->s_data_blocks);
    sbi->s_next_generation = 0;
    sbi->s_free_inodes_count = le32_to_cpu(es->s_free_inodes_count);
    sbi->s_free_data_blocks_count = le32_to_cpu(es->s_free_data_blocks_count);
    sbi->s_inodes_count = le32_to_cpu(es->s_inodes_count);
    sbi->s_blocks_count = le32_to_cpu(es->s_blocks_count);

    sbi->s_inode_bitmap.nr_valid_bits = le32_to_cpu(es->s_inodes_count);
    sbi->s_data_bitmap.nr_valid_bits = le32_to_cpu(es->s_blocks_count) 
        - le32_to_cpu(es->s_data_blocks);

    rwlock_init(&sbi->rwlock);
//.........这里部分代码省略.........