C++ EXT2_SB函数代码示例

static int ext2_show_options(struct seq_file *seq, struct vfsmount *vfs)
{
	struct ext2_sb_info *sbi = EXT2_SB(vfs->mnt_sb);

	if (sbi->s_mount_opt & EXT2_MOUNT_GRPID)
		seq_puts(seq, ",grpid");

#if defined(CONFIG_QUOTA)
	if (sbi->s_mount_opt & EXT2_MOUNT_USRQUOTA)
		seq_puts(seq, ",usrquota");

	if (sbi->s_mount_opt & EXT2_MOUNT_GRPQUOTA)
		seq_puts(seq, ",grpquota");
#endif

#if defined(CONFIG_EXT2_FS_XIP)
	if (sbi->s_mount_opt & EXT2_MOUNT_XIP)
		seq_puts(seq, ",xip");
#endif

	return 0;
}

static int ext2_sync_fs(struct super_block *sb, int wait)
{
	struct ext2_super_block *es = EXT2_SB(sb)->s_es;

	lock_kernel();
	if (es->s_state & cpu_to_le16(EXT2_VALID_FS)) {
		ext2_debug("setting valid to 0\n");
		es->s_state &= cpu_to_le16(~EXT2_VALID_FS);
		es->s_free_blocks_count =
			cpu_to_le32(ext2_count_free_blocks(sb));
		es->s_free_inodes_count =
			cpu_to_le32(ext2_count_free_inodes(sb));
		es->s_mtime = cpu_to_le32(get_seconds());
		ext2_sync_super(sb, es);
	} else {
		ext2_commit_super(sb, es);
	}
	sb->s_dirt = 0;
	unlock_kernel();

	return 0;
}

static struct dentry *ext2_get_dentry(struct super_block *sb, void *vobjp)
{
	__u32 *objp = vobjp;
	unsigned long ino = objp[0];
	__u32 generation = objp[1];
	struct inode *inode;
	struct dentry *result;

	if (ino < EXT2_FIRST_INO(sb) && ino != EXT2_ROOT_INO)
		return ERR_PTR(-ESTALE);
	if (ino > le32_to_cpu(EXT2_SB(sb)->s_es->s_inodes_count))
		return ERR_PTR(-ESTALE);

	/* iget isn't really right if the inode is currently unallocated!!
	 * ext2_read_inode currently does appropriate checks, but
	 * it might be "neater" to call ext2_get_inode first and check
	 * if the inode is valid.....
	 */
	inode = iget(sb, ino);
	if (inode == NULL)
		return ERR_PTR(-ENOMEM);
	if (is_bad_inode(inode) ||
	    (generation && inode->i_generation != generation)) {
		/* we didn't find the right inode.. */
		iput(inode);
		return ERR_PTR(-ESTALE);
	}
	/* now to find a dentry.
	 * If possible, get a well-connected one
	 */
	result = d_alloc_anon(inode);
	if (!result) {
		iput(inode);
		return ERR_PTR(-ENOMEM);
	}
	return result;
}

/*
 * This must be called with sbi->s_lock held.
 */
void ext2_update_dynamic_rev(struct super_block *sb)
{
	struct ext2_super_block *es = EXT2_SB(sb)->s_es;

	if (le32_to_cpu(es->s_rev_level) > EXT2_GOOD_OLD_REV)
		return;

	ext2_msg(sb, KERN_WARNING,
		     "warning: updating to rev %d because of "
		     "new feature flag, running e2fsck is recommended",
		     EXT2_DYNAMIC_REV);

	es->s_first_ino = cpu_to_le32(EXT2_GOOD_OLD_FIRST_INO);
	es->s_inode_size = cpu_to_le16(EXT2_GOOD_OLD_INODE_SIZE);
	es->s_rev_level = cpu_to_le32(EXT2_DYNAMIC_REV);
	/* leave es->s_feature_*compat flags alone */
	/* es->s_uuid will be set by e2fsck if empty */

	/*
	 * The rest of the superblock fields should be zero, and if not it
	 * means they are likely already in use, so leave them alone.  We
	 * can leave it up to e2fsck to clean up any inconsistencies there.
	 */
}

/*
 * get the group's descriptor of group_num
 */
static const struct ext2_group_desc *
ext2_get_group_desc(struct fs_info *fs, uint32_t group_num)
{
    struct ext2_sb_info *sbi = EXT2_SB(fs);
    uint32_t desc_block, desc_index;
    const struct ext2_group_desc *desc_data_block;

    if (group_num >= sbi->s_groups_count) {
	printf ("ext2_get_group_desc"
		"block_group >= groups_count - "
		"block_group = %d, groups_count = %d",
		group_num, sbi->s_groups_count);

	return NULL;
    }

    desc_block = group_num / sbi->s_desc_per_block;
    desc_index = group_num % sbi->s_desc_per_block;

    desc_block += sbi->s_first_data_block + 1;

    desc_data_block = get_cache(fs->fs_dev, desc_block);
    return &desc_data_block[desc_index];
}

static const struct ext2_inode *
ext2_get_inode(struct fs_info *fs, int inr)
{
    const struct ext2_group_desc *desc;
    const char *data;
    uint32_t inode_group, inode_offset;
    uint32_t block_num, block_off;

    inr--;
    inode_group  = inr / EXT2_INODES_PER_GROUP(fs);
    inode_offset = inr % EXT2_INODES_PER_GROUP(fs);
    desc = ext2_get_group_desc(fs, inode_group);
    if (!desc)
	return NULL;

    block_num = desc->bg_inode_table +
	inode_offset / EXT2_INODES_PER_BLOCK(fs);
    block_off = inode_offset % EXT2_INODES_PER_BLOCK(fs);

    data = get_cache(fs->fs_dev, block_num);

    return (const struct ext2_inode *)
	(data + block_off * EXT2_SB(fs)->s_inode_size);
}

static char *ext2_fs_uuid(struct fs_info *fs)
{
    char *uuid = NULL;

    uuid = malloc(EXT2_UUID_LEN);
    if (!uuid)
	return NULL;

    if (snprintf(uuid, EXT2_UUID_LEN,
                  "%02x%02x%02x%02x-%02x%02x-%02x%02x-%02x%02x-%02x%02x%02x%02x%02x%02x",
	          EXT2_SB(fs)->s_uuid[0],
	          EXT2_SB(fs)->s_uuid[1],
	          EXT2_SB(fs)->s_uuid[2],
	          EXT2_SB(fs)->s_uuid[3],
	          EXT2_SB(fs)->s_uuid[4],
	          EXT2_SB(fs)->s_uuid[5],
	          EXT2_SB(fs)->s_uuid[6],
	          EXT2_SB(fs)->s_uuid[7],
	          EXT2_SB(fs)->s_uuid[8],
	          EXT2_SB(fs)->s_uuid[9],
	          EXT2_SB(fs)->s_uuid[10],
	          EXT2_SB(fs)->s_uuid[11],
	          EXT2_SB(fs)->s_uuid[12],
	          EXT2_SB(fs)->s_uuid[13],
	          EXT2_SB(fs)->s_uuid[14],
	          EXT2_SB(fs)->s_uuid[15]
	          ) < 0) {
	free(uuid);
	return NULL;
    }

    return uuid;
}

//.........这里部分代码省略.........
	/* 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))
		goto failed_mount;

	sb->s_flags = (sb->s_flags & ~MS_POSIXACL) |
		((EXT2_SB(sb)->s_mount_opt & EXT2_MOUNT_POSIX_ACL) ?
		 MS_POSIXACL : 0);

	ext2_xip_verify_sb(sb); /* see if bdev supports xip, unset
				    EXT2_MOUNT_XIP if not */

	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.
	 */
	features = EXT2_HAS_INCOMPAT_FEATURE(sb, ~EXT2_FEATURE_INCOMPAT_SUPP);
	if (features) {
		printk("EXT2-fs: %s: couldn't mount because of "
		       "unsupported optional features (%x).\n",
		       sb->s_id, le32_to_cpu(features));
		goto failed_mount;
	}
	if (!(sb->s_flags & MS_RDONLY) &&
	    (features = 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, le32_to_cpu(features));
		goto failed_mount;
	}

	blocksize = BLOCK_SIZE << le32_to_cpu(sbi->s_es->s_log_block_size);

static int ext2_show_options(struct seq_file *seq, struct vfsmount *vfs)
{
	struct super_block *sb = vfs->mnt_sb;
	struct ext2_sb_info *sbi = EXT2_SB(sb);
	struct ext2_super_block *es = sbi->s_es;
	unsigned long def_mount_opts;

	def_mount_opts = le32_to_cpu(es->s_default_mount_opts);

	if (sbi->s_sb_block != 1)
		seq_printf(seq, ",sb=%lu", sbi->s_sb_block);
	if (test_opt(sb, MINIX_DF))
		seq_puts(seq, ",minixdf");
	if (test_opt(sb, GRPID))
		seq_puts(seq, ",grpid");
	if (!test_opt(sb, GRPID) && (def_mount_opts & EXT2_DEFM_BSDGROUPS))
		seq_puts(seq, ",nogrpid");
	if (sbi->s_resuid != EXT2_DEF_RESUID ||
	    le16_to_cpu(es->s_def_resuid) != EXT2_DEF_RESUID) {
		seq_printf(seq, ",resuid=%u", sbi->s_resuid);
	}
	if (sbi->s_resgid != EXT2_DEF_RESGID ||
	    le16_to_cpu(es->s_def_resgid) != EXT2_DEF_RESGID) {
		seq_printf(seq, ",resgid=%u", sbi->s_resgid);
	}
	if (test_opt(sb, ERRORS_RO)) {
		int def_errors = le16_to_cpu(es->s_errors);

		if (def_errors == EXT2_ERRORS_PANIC ||
		    def_errors == EXT2_ERRORS_CONTINUE) {
			seq_puts(seq, ",errors=remount-ro");
		}
	}
	if (test_opt(sb, ERRORS_CONT))
		seq_puts(seq, ",errors=continue");
	if (test_opt(sb, ERRORS_PANIC))
		seq_puts(seq, ",errors=panic");
	if (test_opt(sb, NO_UID32))
		seq_puts(seq, ",nouid32");
	if (test_opt(sb, DEBUG))
		seq_puts(seq, ",debug");
	if (test_opt(sb, OLDALLOC))
		seq_puts(seq, ",oldalloc");

#ifdef CONFIG_EXT2_FS_XATTR
	if (test_opt(sb, XATTR_USER))
		seq_puts(seq, ",user_xattr");
	if (!test_opt(sb, XATTR_USER) &&
	    (def_mount_opts & EXT2_DEFM_XATTR_USER)) {
		seq_puts(seq, ",nouser_xattr");
	}
#endif

#ifdef CONFIG_EXT2_FS_POSIX_ACL
	if (test_opt(sb, POSIX_ACL))
		seq_puts(seq, ",acl");
	if (!test_opt(sb, POSIX_ACL) && (def_mount_opts & EXT2_DEFM_ACL))
		seq_puts(seq, ",noacl");
#endif

	if (test_opt(sb, NOBH))
		seq_puts(seq, ",nobh");

#if defined(CONFIG_QUOTA)
	if (sbi->s_mount_opt & EXT2_MOUNT_USRQUOTA)
		seq_puts(seq, ",usrquota");

	if (sbi->s_mount_opt & EXT2_MOUNT_GRPQUOTA)
		seq_puts(seq, ",grpquota");
#endif

#if defined(CONFIG_EXT2_FS_XIP)
	if (sbi->s_mount_opt & EXT2_MOUNT_XIP)
		seq_puts(seq, ",xip");
#endif

	if (!test_opt(sb, RESERVATION))
		seq_puts(seq, ",noreservation");

	return 0;
}

static int ext2_statfs (struct dentry * dentry, struct kstatfs * buf)
{
	struct super_block *sb = dentry->d_sb;
	struct ext2_sb_info *sbi = EXT2_SB(sb);
	struct ext2_super_block *es = sbi->s_es;
	u64 fsid;

	if (test_opt (sb, MINIX_DF))
		sbi->s_overhead_last = 0;
	else if (sbi->s_blocks_last != le32_to_cpu(es->s_blocks_count)) {
		unsigned long i, overhead = 0;
		smp_rmb();

		/*
		 * Compute the overhead (FS structures). This is constant
		 * for a given filesystem unless the number of block groups
		 * changes so we cache the previous value until it does.
		 */

		/*
		 * All of the blocks before first_data_block are
		 * overhead
		 */
		overhead = le32_to_cpu(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 < sbi->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 += (sbi->s_groups_count *
			     (2 + sbi->s_itb_per_group));
		sbi->s_overhead_last = overhead;
		smp_wmb();
		sbi->s_blocks_last = le32_to_cpu(es->s_blocks_count);
	}

	buf->f_type = EXT2_SUPER_MAGIC;
	buf->f_bsize = sb->s_blocksize;
	buf->f_blocks = le32_to_cpu(es->s_blocks_count) - sbi->s_overhead_last;
	buf->f_bfree = ext2_count_free_blocks(sb);
	es->s_free_blocks_count = cpu_to_le32(buf->f_bfree);
	buf->f_bavail = buf->f_bfree - le32_to_cpu(es->s_r_blocks_count);
	if (buf->f_bfree < le32_to_cpu(es->s_r_blocks_count))
		buf->f_bavail = 0;
	buf->f_files = le32_to_cpu(es->s_inodes_count);
	buf->f_ffree = ext2_count_free_inodes(sb);
	es->s_free_inodes_count = cpu_to_le32(buf->f_ffree);
	buf->f_namelen = EXT2_NAME_LEN;
	fsid = le64_to_cpup((void *)es->s_uuid) ^
	       le64_to_cpup((void *)es->s_uuid + sizeof(u64));
	buf->f_fsid.val[0] = fsid & 0xFFFFFFFFUL;
	buf->f_fsid.val[1] = (fsid >> 32) & 0xFFFFFFFFUL;
	return 0;
}

static int ext2_remount (struct super_block * sb, int * flags, char * data)
{
	struct ext2_sb_info * sbi = EXT2_SB(sb);
	struct ext2_super_block * es;
	unsigned long old_mount_opt = sbi->s_mount_opt;
	struct ext2_mount_options old_opts;
	unsigned long old_sb_flags;
	int err;

	lock_kernel();

	/* Store the old options */
	old_sb_flags = sb->s_flags;
	old_opts.s_mount_opt = sbi->s_mount_opt;
	old_opts.s_resuid = sbi->s_resuid;
	old_opts.s_resgid = sbi->s_resgid;

	/*
	 * Allow the "check" option to be passed as a remount option.
	 */
	if (!parse_options (data, sbi)) {
		err = -EINVAL;
		goto restore_opts;
	}

	sb->s_flags = (sb->s_flags & ~MS_POSIXACL) |
		((sbi->s_mount_opt & EXT2_MOUNT_POSIX_ACL) ? MS_POSIXACL : 0);

	ext2_xip_verify_sb(sb); /* see if bdev supports xip, unset
				    EXT2_MOUNT_XIP if not */

	if ((ext2_use_xip(sb)) && (sb->s_blocksize != PAGE_SIZE)) {
		printk("XIP: Unsupported blocksize\n");
		err = -EINVAL;
		goto restore_opts;
	}

	es = sbi->s_es;
	if (((sbi->s_mount_opt & EXT2_MOUNT_XIP) !=
	    (old_mount_opt & EXT2_MOUNT_XIP)) &&
	    invalidate_inodes(sb)) {
		ext2_warning(sb, __func__, "refusing change of xip flag "
			     "with busy inodes while remounting");
		sbi->s_mount_opt &= ~EXT2_MOUNT_XIP;
		sbi->s_mount_opt |= old_mount_opt & EXT2_MOUNT_XIP;
	}
	if ((*flags & MS_RDONLY) == (sb->s_flags & MS_RDONLY)) {
		unlock_kernel();
		return 0;
	}
	if (*flags & MS_RDONLY) {
		if (le16_to_cpu(es->s_state) & EXT2_VALID_FS ||
		    !(sbi->s_mount_state & EXT2_VALID_FS)) {
			unlock_kernel();
			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(sbi->s_mount_state);
		es->s_mtime = cpu_to_le32(get_seconds());
	} else {
		__le32 ret = EXT2_HAS_RO_COMPAT_FEATURE(sb,
					       ~EXT2_FEATURE_RO_COMPAT_SUPP);
		if (ret) {
			printk("EXT2-fs: %s: couldn't remount RDWR because of "
			       "unsupported optional features (%x).\n",
			       sb->s_id, le32_to_cpu(ret));
			err = -EROFS;
			goto restore_opts;
		}
		/*
		 * 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.)
		 */
		sbi->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);
	unlock_kernel();
	return 0;
restore_opts:
	sbi->s_mount_opt = old_opts.s_mount_opt;
	sbi->s_resuid = old_opts.s_resuid;
	sbi->s_resgid = old_opts.s_resgid;
	sb->s_flags = old_sb_flags;
	unlock_kernel();
	return err;
}

static int ext2_setup_super (struct super_block * sb,
			      struct ext2_super_block * es,
			      int read_only)
{
	int res = 0;
	struct ext2_sb_info *sbi = EXT2_SB(sb);

	if (le32_to_cpu(es->s_rev_level) > EXT2_MAX_SUPP_REV) {
		printk ("EXT2-fs warning: revision level too high, "
			"forcing read-only mode\n");
		res = MS_RDONLY;
	}
	if (read_only)
		return res;
	/* PR 28089 - Allow user to turn off a forced fsck in order
	 * to let user to mount a dirty FS RW
	 * Thus if FS is dirty and nocheck is the mount option, then
	 * FS is mounted RW.
	 */
	if (!(sbi->s_mount_state & EXT2_VALID_FS)) {
		if (!test_opt (sb, CHECK))
			printk ("EXT2-fs warning: mounting unclean fs with "
			"errors in RW mode.\nRunning e2fsck is strongly urged "
			"and recommended.\n");
		else {
			printk ("EXT2-fs warning: mounting unchecked fs read-only. "
			"Running e2fsck is recommended before re-mounting read-write.\n");
			sb->s_flags |= MS_RDONLY;
			return MS_RDONLY;
		}
	}
	/* PR 28089 - Allow user to turn off a forced fsck in order
	 * to let user to mount a dirty FS RW.
	 * Thus if FS is dirty and nocheck is the mount option, then
	 * FS is mounted RW.
	 */
	else if ((sbi->s_mount_state & EXT2_ERROR_FS)) {
		if (!test_opt (sb, CHECK))
			printk ("EXT2-fs warning: mounting unclean fs with "
			"errors in RW mode.\nRunning e2fsck is strongly urged "
			"and recommended.\n");
		else {
			printk ("EXT2-fs warning: mounting unchecked fs read-only. "
			"Running e2fsck is recommended before re-mounting read-write.\n");
			sb->s_flags |= MS_RDONLY;
			return MS_RDONLY;
		}
	}
	else if ((__s16) le16_to_cpu(es->s_max_mnt_count) >= 0 &&
		 le16_to_cpu(es->s_mnt_count) >=
		 (unsigned short) (__s16) le16_to_cpu(es->s_max_mnt_count)) {
		printk ("EXT2-fs warning: maximal mount count reached. Mounting read-only. "
			"Running e2fsck is recommended before re-mounting read-write.\n");
		sb->s_flags |= MS_RDONLY;
		return MS_RDONLY;
	}
	else if (le32_to_cpu(es->s_checkinterval) &&
		(le32_to_cpu(es->s_lastcheck) + le32_to_cpu(es->s_checkinterval) <= get_seconds())) {
		printk ("EXT2-fs warning: checktime reached. Mounting read-only. "
			"Running e2fsck is recommended before re-mounting read-write.\n");
		sb->s_flags |= MS_RDONLY;
		return MS_RDONLY;
	}
	if (!le16_to_cpu(es->s_max_mnt_count))
		es->s_max_mnt_count = cpu_to_le16(EXT2_DFL_MAX_MNT_COUNT);
	es->s_mnt_count=cpu_to_le16(le16_to_cpu(es->s_mnt_count) + 1);
	ext2_write_super(sb);
	if (test_opt (sb, DEBUG))
		printk ("[EXT II FS %s, %s, bs=%lu, fs=%lu, gc=%lu, "
			"bpg=%lu, ipg=%lu, mo=%04lx]\n",
			EXT2FS_VERSION, EXT2FS_DATE, sb->s_blocksize,
			sbi->s_frag_size,
			sbi->s_groups_count,
			EXT2_BLOCKS_PER_GROUP(sb),
			EXT2_INODES_PER_GROUP(sb),
			sbi->s_mount_opt);
#ifdef CONFIG_EXT2_CHECK
	if (test_opt (sb, CHECK)) {
		ext2_check_blocks_bitmap (sb);
		ext2_check_inodes_bitmap (sb);
	}
#endif
	return res;
}

struct super_block * ext2_read_super (struct super_block * sb, void * data,
				      int silent)
{
	struct buffer_head * bh;
  	struct ext2_sb_info * sbi = EXT2_SB(sb);
	struct ext2_super_block * es;
	unsigned long sb_block = 1;
	unsigned short resuid = EXT2_DEF_RESUID;
	unsigned short resgid = EXT2_DEF_RESGID;
	unsigned long block;
	unsigned long logic_sb_block;
	unsigned long offset = 0;
	kdev_t dev = sb->s_dev;
	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.
	 */
	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;
	} else {
		logic_sb_block = sb_block;
	}

	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;
	}
	if (EXT2_HAS_COMPAT_FEATURE(sb, EXT3_FEATURE_COMPAT_HAS_JOURNAL))
		ext2_warning(sb, __FUNCTION__,
			"mounting ext3 filesystem as ext2\n");
	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;

//.........这里部分代码省略.........

static int parse_options(char *options, struct super_block *sb)
{
	char *p;
	struct ext2_sb_info *sbi = EXT2_SB(sb);
	substring_t args[MAX_OPT_ARGS];
	int option;

	if (!options)
		return 1;

	while ((p = strsep (&options, ",")) != NULL) {
		int token;
		if (!*p)
			continue;

		token = match_token(p, tokens, args);
		switch (token) {
		case Opt_bsd_df:
			clear_opt (sbi->s_mount_opt, MINIX_DF);
			break;
		case Opt_minix_df:
			set_opt (sbi->s_mount_opt, MINIX_DF);
			break;
		case Opt_grpid:
			set_opt (sbi->s_mount_opt, GRPID);
			break;
		case Opt_nogrpid:
			clear_opt (sbi->s_mount_opt, GRPID);
			break;
		case Opt_resuid:
			if (match_int(&args[0], &option))
				return 0;
			sbi->s_resuid = option;
			break;
		case Opt_resgid:
			if (match_int(&args[0], &option))
				return 0;
			sbi->s_resgid = option;
			break;
		case Opt_sb:
			/* handled by get_sb_block() instead of here */
			/* *sb_block = match_int(&args[0]); */
			break;
		case Opt_err_panic:
			clear_opt (sbi->s_mount_opt, ERRORS_CONT);
			clear_opt (sbi->s_mount_opt, ERRORS_RO);
			set_opt (sbi->s_mount_opt, ERRORS_PANIC);
			break;
		case Opt_err_ro:
			clear_opt (sbi->s_mount_opt, ERRORS_CONT);
			clear_opt (sbi->s_mount_opt, ERRORS_PANIC);
			set_opt (sbi->s_mount_opt, ERRORS_RO);
			break;
		case Opt_err_cont:
			clear_opt (sbi->s_mount_opt, ERRORS_RO);
			clear_opt (sbi->s_mount_opt, ERRORS_PANIC);
			set_opt (sbi->s_mount_opt, ERRORS_CONT);
			break;
		case Opt_nouid32:
			set_opt (sbi->s_mount_opt, NO_UID32);
			break;
		case Opt_nocheck:
			clear_opt (sbi->s_mount_opt, CHECK);
			break;
		case Opt_debug:
			set_opt (sbi->s_mount_opt, DEBUG);
			break;
		case Opt_oldalloc:
			set_opt (sbi->s_mount_opt, OLDALLOC);
			break;
		case Opt_orlov:
			clear_opt (sbi->s_mount_opt, OLDALLOC);
			break;
		case Opt_nobh:
			set_opt (sbi->s_mount_opt, NOBH);
			break;
#ifdef CONFIG_EXT2_FS_XATTR
		case Opt_user_xattr:
			set_opt (sbi->s_mount_opt, XATTR_USER);
			break;
		case Opt_nouser_xattr:
			clear_opt (sbi->s_mount_opt, XATTR_USER);
			break;
#else
		case Opt_user_xattr:
		case Opt_nouser_xattr:
			ext2_msg(sb, KERN_INFO, "(no)user_xattr options"
				"not supported");
			break;
#endif
#ifdef CONFIG_EXT2_FS_POSIX_ACL
		case Opt_acl:
			set_opt(sbi->s_mount_opt, POSIX_ACL);
			break;
		case Opt_noacl:
			clear_opt(sbi->s_mount_opt, POSIX_ACL);
			break;
#else
		case Opt_acl:
		case Opt_noacl:
//.........这里部分代码省略.........

//.........这里部分代码省略.........
	/* 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));
	
	set_opt(sbi->s_mount_opt, RESERVATION);

	if (!parse_options((char *) data, sb))
		goto failed_mount;

	sb->s_flags = (sb->s_flags & ~MS_POSIXACL) |
		((EXT2_SB(sb)->s_mount_opt & EXT2_MOUNT_POSIX_ACL) ?
		 MS_POSIXACL : 0);
	sb->s_iflags |= SB_I_CGROUPWB;

	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)))
		ext2_msg(sb, KERN_WARNING,
			"warning: feature flags set on rev 0 fs, "
			"running e2fsck is recommended");
	/*
	 * 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.
	 */
	features = EXT2_HAS_INCOMPAT_FEATURE(sb, ~EXT2_FEATURE_INCOMPAT_SUPP);
	if (features) {
		ext2_msg(sb, KERN_ERR,	"error: couldn't mount because of "
		       "unsupported optional features (%x)",
			le32_to_cpu(features));
		goto failed_mount;
	}
	if (!(sb->s_flags & MS_RDONLY) &&
	    (features = EXT2_HAS_RO_COMPAT_FEATURE(sb, ~EXT2_FEATURE_RO_COMPAT_SUPP))){
		ext2_msg(sb, KERN_ERR, "error: couldn't mount RDWR because of "
		       "unsupported optional features (%x)",
		       le32_to_cpu(features));
		goto failed_mount;
	}

	blocksize = BLOCK_SIZE << le32_to_cpu(sbi->s_es->s_log_block_size);