hesela.devExt4 writeback mode
Ext4 writeback mode journals metadata without requiring associated file-data writes to precede the metadata commit.
The name describes a filesystem journaling mode, not a disk's volatile write cache. File contents are outside the journal, and recovery can leave recently written files with incorrect data. [1]
Applications still need explicit synchronization and error handling where persistence is required. Synchronizing a file does not by itself make its directory entry durable. [2]
Relations
- related
- Ext4 ordered mode, Ext4 data journaling, Write-back cache, fsync, Directory fsync, Crash consistency
Citations
- Linux v6.12: journal coverage and ordered-mode fast commits
- Linux man-pages: fsync(2), file data, directory entries and errors
Sources & caveats
- Source review scoped to Linux v6.12; not a crash experiment or certification of later kernels.