FS to physical disk block conversion

[Dima Naumov]

I am sorry for my English. OK my problem: i do not understand how i can 
get real address of disk block, when i use macros fsbtodb() to convert 
fs address to physical disk block address i receive odd result, explain 
me please where my error.
Example:
         struct fs *sblock;
         ino_t inode = 2;
         caddr_t inoblock;
         struct ufs2_dinode * ino;
         ...
         if(pread(dev_fd, ino, sizeof(struct ufs2_dinode),\
                 (sblock->fs_bsize * fsbtodb(sblock, \
                 ino_to_fsba(sblock, inode)))) != sizeof(struct 
ufs2_dinode))
                                 error(__LINE__, errno);
After executing this string a not get correct inode in "ino". Please 
explain, it important to me!