structures

Table of Contents Structural Hierarchy Component breakdown volume log chain itree inode dtree otree inum bitmap block bitmap

Structural Hierarchy

• Volume
• Physical structures
• Superblock
• Pointer to root of itree
• Pointer to root of otree
• Pointer to head of log chain
• Log chain (linked list)
• itree (b+tree)
• inode (indexed by inum)
• attribute list (serial encoding of some sort)
• inode attributes
• fixed length attributes
• ctime
• mtime
• atime
• link count
• pointer to root of dtree
• variable length attributes
• xattrs (structure unknown)
• dtree (b+tree)
• extent (indexed by offset)
• otree (b+tree)
• inum
• Virtual structures
• inum allocation bitmap (sparse file)
• block allocation bitmap (sparse file)

Component breakdown

volume

Log chain, itree, otree

log chain

Chain of log blocks

itree

b+tree of inodes indexed by inum

inode

inode information, dtree

dtree

b+tree of data extents indexed by logical offset

otree

b+tree of orphan inodes, indexed by inum

inum bitmap

sparse file containing bitmap of inum allocation

block bitmap

sparse file containing bitmap of block allocation