3. Global Structures

The filesystem is sharded into a number of block groups, each of which have static metadata at fixed locations.

• 3.1. Super Block
• 3.2. Block Group Descriptors
• 3.3. Block and inode Bitmaps
• 3.4. Inode Table
• 3.5. Multiple Mount Protection
• 3.6. Journal (jbd2)
  • 3.6.1. Layout
  • 3.6.2. External Journal
  • 3.6.3. Block Header
  • 3.6.4. Super Block
  • 3.6.5. Descriptor Block
  • 3.6.6. Data Block
  • 3.6.7. Revocation Block
  • 3.6.8. Commit Block
  • 3.6.9. Fast commits
  • 3.6.10. Fast Commit Replay Idempotence
  • 3.6.11. Journal Checkpoint
• 3.7. Orphan file