{
  "slug": "ext4-data-writeback",
  "term": "Ext4 writeback mode",
  "aliases": [
    "ext4 data=writeback"
  ],
  "definition": "Ext4 writeback mode journals metadata without requiring associated file-data writes to precede the metadata commit.",
  "note": "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. [journal]\n\nApplications still need explicit synchronization and error handling where persistence is required. Synchronizing a file does not by itself make its directory entry durable. [fsync-contract]",
  "related": [
    "ext4-data-ordered",
    "ext4-data-journal",
    "write-back-cache",
    "fsync",
    "directory-fsync",
    "crash-consistency"
  ],
  "citations": [
    {
      "id": "journal",
      "title": "Linux v6.12: journal coverage and ordered-mode fast commits",
      "url": "https://github.com/torvalds/linux/blob/adc218676eef25575469234709c2d87185ca223a/Documentation/filesystems/ext4/journal.rst",
      "accessed": "2026-10-21"
    },
    {
      "id": "fsync-contract",
      "title": "Linux man-pages: fsync(2), file data, directory entries and errors",
      "url": "https://man7.org/linux/man-pages/man2/fsync.2.html",
      "accessed": "2026-10-21"
    }
  ],
  "provenance": [
    "Source review scoped to Linux v6.12; not a crash experiment or certification of later kernels."
  ],
  "status": "shipping",
  "advantages": [],
  "limitations": [],
  "supersedes": [],
  "supersededBy": [],
  "firstSeen": null,
  "lastSeen": null,
  "updated": "2026-10-21"
}